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Resistance to gastrointestinal nematodes has previously been shown to be a moderately heritable trait in some breeds of sheep, but the mechanisms of resistance are not well understood. Selection for resistance currently relies upon faecal egg counts (FEC), blood packed cell volumes and FAMACHA visual indicator scores of anaemia. Identifying genomic markers associated with disease resistance would potentially improve the selection process and provide a more reliable means of classifying and understanding the biology behind resistant and susceptible sheep. A GWAS was conducted to identify possible genetic loci associated with resistance to Haemonchus contortus in Katahdin sheep. Forty animals were selected from the top and bottom 10% of estimated breeding values for FEC from a total pool of 641 sires and ram lambs. Samples were genotyped using Applied Biosystems™ Axiom™ Ovine Genotyping Array (50K) consisting of 51 572 SNPs. Following quality control, 46 268 SNPs were included in subsequent analyses. Analyses were conducted using a linear regression model in plink v1.90 and a single-locus mixed model in snp and variation suite. Genome-wide significance was determined by a Bonferroni correction for multiple testing. Using linear regression, loci on chromosomes 2, 3, 16, 23 and 24 were significantly associated at the genome level with FEC estimated breeding values, and we identified a region on chromosome 2 that was significant using both statistical analyses. We suggest a potential role for the gene DIS3L2 for gastrointestinal nematode resistance in Katahdin sheep, although further research is needed to validate these findings., (© 2020 The Authors. Animal Genetics published by John Wiley & Sons Ltd on behalf of Stichting International Foundation for Animal Genetics.)

Reliance on anthelmintic drugs to control internal parasites in sheep is no longer sustainable because of the development of resistance to these drugs in parasite populations. Genetic selection may offer an alternative long-term solution, as differences in parasite resistance exist both within and among sheep breeds. However, selection for parasite resistance may have correlated effects on other production traits. The objectives of this study were to estimate genetic parameters for weaning (WFEC) and postweaning (PWFEC) fecal egg counts (FEC) and assess their relationship with birth (BWT), weaning (WWT), and postweaning (PWWT) BW in Katahdin lambs. The study used WFEC (n = 2,537), PWFEC (n = 3.421), BWT (n = 12,869), WWT (n = 10,961), and PWWT (n = 7,812) from 12,869 lambs measured between 2003 and 2015 in 13 flocks enrolled in the U.S. National Sheep Improvement Program. Animal and sire models were fitted to the data using the ASReml statistical package. Records were corrected for fixed effects of dam age, joint effect of type of birth and rearing, and management group (defined by joint effects of flock, sex, and birth year and season); lamb age in days at each measurement time was fitted as a covariate. Maternal additive and maternal permanent environmental effects were not significant (P > 0.05), but litter effects influenced (P < 0.01) both WFEC and PWFEC. Heritability estimates ranged from 0.18 to 0.26 for WFEC and 0.23 to 0.46 for PWFEC, depending on the model used. Heritability estimates from sire models were higher than estimates from animal models. Direct additive, litter, residual, and phenotypic correlations between WFEC and PWFEC were 0.82, 0.25, 0.15, and 0.29, respectively. Bivariate analyses revealed low to moderate correlations between BW and FEC. Moderate heritabilities for FEC in this study indicated that genetic progress for this trait can be achieved in Katahdin lambs and that selection for low FEC should have little or no effect on BW.

Haemonchus contortus is a major parasite of small ruminants and its blood-feeding behaviour causes effects ranging from mild anaemia to death. Knowledge of the genetic variation within and among H. contortus populations can provide the foundation for understanding transmission patterns and aid in the control of haemonchosis. Adult male H. contortus were collected from three geographical regions in Egypt. The second internal transcribed spacer (ITS2) of nuclear ribosomal DNA was amplified using the polymerase chain reaction (PCR) and sequenced directly. The population genetic diversity and sequence variations were determined. Nucleotide sequence analyses revealed one genotype (ITS2) in all worms, without genetic differentiation. The similarity in population genetic diversity and genetic patterns observed among the three geographical regions could be attributed to possible movement between the sites. This is the first study of genetic variation in H. contortus in Egypt. The present results could have implications for the rapid characterization of H. contortus and other trichostrongyloid nematodes, and evaluation of the epidemiology of H. contortus in Egypt.

The FAMACHA system was introduced to the U.S. just over 10 yr ago to allow selective deworming of lambs with anemia associated with and retard the development of anthelmintic resistance. The FAMACHA system was initially developed as a predictor of packed cell volume (PCV), but correlations between FAMACHA and fecal egg counts (FEC) have also been reported. It is important to understand factors that influence FAMACHA scores among farms to improve management of gastrointestinal nematodes. The objectives of this study were therefore to quantify associations between FAMACHA scores, FEC, BW, and age in Katahdin lambs at 2 different measurement times in 8 flocks in the eastern U.S., and to assess consistency of relationships between FAMACHA and FEC among flocks. Data came from 1,644 Katahdin lambs from 7 flocks sampled at approximately 90 d of age, and 1,295 lambs from 6 flocks sampled at approximately 120 d of age over a 5 yr period. Residual correlations among log-transformed FEC (LFEC), FAMACHA scores, BW, and lamb ages at each measurement time were determined. Repeatability of each variable was also determined as residual correlations among repeated measures. At both 90 and 120 d of age, correlations of FAMACHA scores with LFEC and BW were significant ( < 0.001), but numerically modest (0.25 and -0.16, respectively at 90 d; 0.31 and -0.16, respectively at 120 d), demonstrating that higher FAMACHA scores were associated with higher FEC and more likely to be observed in lighter lambs. A small negative correlation was observed between FAMACHA score and lamb age ( = -0.05, = 0.05, 90 d; = -0.11, < 0.001, 120 d) indicating that younger lambs were more likely to have elevated FAMACHA scores. Thus, younger and lighter lambs will likely be more susceptible to parasitism and may need to be managed more diligently than older or heavier lambs. In addition, FAMACHA scores have potential to improve breeding value estimates in programs designed to genetically improve parasite resistance.

Selection for low fecal egg counts (FEC) can be used to genetically enhance resistance to gastrointestinal nematode parasites in growing lambs, thereby reducing the frequency of use of anthelmintics, facilitating marketing of organic lamb, and reducing the risk of development of anthelmintic resistance by the parasite. Recording of FEC in lambs has, therefore, been incorporated into several national sheep genetic evaluation programs. Ewes in late gestation and early lactation are also vulnerable to parasite infection and commonly experience a periparturient rise in FEC. This study was designed to assess factors associated with the periparturient rise in FEC in Katahdin ewes and associated changes in FEC in their lambs. Data came from 1,487 lambings by 931 Katahdin ewes from 11 farms in the Eastern United States. Fecal egg counts were measured in ewes at approximately 0, 30, and 60 d postpartum and in their lambs at approximately 60, 90, and 120 d of age. Approximately 1,400 lambs were evaluated at each measurement age. Data were analyzed separately for ewes and lambs and also initially analyzed separately for each measurement time. Repeated-measures analyses were then used to evaluate responses across measurement times. In ewes, FEC peaked at approximately 28 d postpartum, and we concluded that informative periparturient FEC could be obtained from 1 wk before until approximately 5 wk after lambing. Yearling ewes had higher FEC than adult ewes ( < 0.01), and ewes that nursed twin or triplet lambs had higher FEC than ewes that nursed single lambs ( < 0.01). In lambs, FEC increased through approximately 120 d of age. Lambs from yearling ewes and lambs nursed in larger litters were, like their dams, at greater risk of parasitism ( < 0.05). Ewes and lambs in these groups would benefit from enhanced monitoring of parasite loads at lambing and in early lactation. Correlations () between FEC in lambs at 90 d of age and FEC in ewes at 0, 30, and 60 d postpartum of 0.05 to 0.09 ( ≤ 0.05) support the presence of a genetic relationship between these 2 indicators of parasite resistance.

Control of gastrointestinal nematodes (GIN) remains a critical issue due to the prevalence of anthelmintic resistance. The objective of the experiment was to determine the efficacy of copper oxide wire particles (COWP) from three commercial sources and a combination of COWP and albendazole to control GIN and/or Haemonchus contortus in lambs. Naturally infected Katahdin lambs in early June 2014 and 2015 were randomly assigned to receive no COWP (CON; n=9 and 12) or 2g COWP in a gel capsule as Copasure(®) (COP; n=4 and 17; Animax Ltd.), copper oxide-wire form (AUS; n=7 in 2014 only; Pharmplex), Ultracruz™ (ULT; n=8 and 15; Santa Cruz Animal Health™), no COWP and albendazole (CON+alb; n=10 in 2015 only; 15mg/kg BW; Valbazen(®); Zoetis Animal Health), or COWP+alb (n=7 and 11; in 2014, lambs were administered alb on day 3). Lambs grazed grass pastures as a group and were supplemented with 227g/lamb daily of a commercial grain mix (15% crude protein) and the same amount of alfalfa pellets. Feces were collected on days 0 (day of COWP treatment), 7, and 14 for determination of fecal egg counts (FEC). Pooled (2014) or pooled treatment group feces were cultured on days 0, 7, and 14 (2015 only) to determine GIN genera. Data were analyzed using repeated measures in a mixed model, and FEC were log transformed. The predominant GIN on day 0 was H. contortus (87%) in 2014, and there was a mixed population in 2015. The mean FEC was reduced by day 7 in AUS and ULT lambs (treatment×day, P=0.001), and all of the COWP products were similar. By day 14, the AUS FEC were lower than the CON and COP groups. When examining the combination of COWP and synthetic anthelmintic, the FEC of COWP+alb were reduced to nearly 0eggs/g (back-transformed) and lower than the other groups (treatment×day, P=0.001). The percentage of H. contortus in cultured feces was reduced to a greater extent in the COWP than CON or CON+alb groups of lambs. In a mixed GIN population, the COWP products appeared to be similar in efficacy and using a combination of COWP+alb increased the efficacy not only against H. contortus, but all GIN genera present, offering options in the face of resistance to benzimidazoles., (Published by Elsevier B.V.)

Sericea lespedeza (SL; Lespedeza cuneata) is a legume rich in condensed tannins that can be grazed or fed to small ruminants for parasite control. Condensed tannins, a secondary plant compound in SL, may lead to unintended consequences such as changes in production. In our preliminary research, there was consistently a reduction in serum and liver concentrations of Mo. The objective of this study was to determine the effect of SL with or without Mo supplementation on changes in BW, hematology, and serum biochemistry in lambs. Thirty ram lambs weaned in May (84 ± 1.5 d of age; 27 ± 1.1 kg) were blocked by BW, breed type (full or three-fourths Katahdin), and EBV of parasite resistance and randomly assigned to be fed 900 g of alfalfa-based supplement (CON; n = 10) or SL-based supplement (n = 20) for 103 d. Supplements were formulated to be isonitrogenous and isocaloric and to meet trace mineral requirements. Within the SL diet, half of the lambs received 490 mg sodium molybdate weekly (SLMO). Body condition scores and BW were determined every 14 d and blood and feces collected to determine hematological and serum biochemical profiles and fecal egg counts (FEC). Data were analyzed using a mixed model with repeated measures and orthogonal contrasts. The white blood cell counts tended to be reduced in SL- and SLMO-fed lambs compared with CON-fed lambs (P < 0.06), which was associated with a reduction in neutrophils (P < 0.001). Red blood cell counts were also reduced in SL but not SLMO lambs compared with CON lambs (P < 0.04). There was a reduction in blood packed cell volume (P < 0.04) and serum concentrations of albumin (P < 0.001) and creatinine (P < 0.02) in both SL and SLMO lambs compared with CON lambs. Similarly, concentrations of blood urea nitrogen were reduced in both SL and SLMO lambs, but differences among dietary treatments disappeared after 42 d of feeding (treatment × day, P < 0.004). Serum concentrations of total proteins were reduced only in SLMO lambs compared with other lambs (P < 0.001). Body weight and FEC were similar among dietary treatments. Means of all measurements were within a normal range, even though there were subtle but significant differences between dietary groups. Feeding a diet high in condensed tannin-rich SL did not lead to serious effects on hematology or serum biochemistry in lambs.

The objective of this study was to determine the impact of integrated parasite management (IPM) training, including FAMACHA(©) eyelid color scoring, on the ability of U.S. sheep and goat producers to control gastrointestinal nematodes (GIN) on their farms. A survey was developed and provided to over 2000 producers trained from 2004 to 2008 in IPM with questions involving farm size (number of sheep/goats), location (U.S. state), impact of training on parasite control efforts and parasite problems on farm, and IPM practices used. Responses were divided into U.S. Census regions of the U.S. Descriptive statistics and logistic regression were used to describe results. Most of the 729 respondents were from the southern region of the U.S. (54.3%) and were small-scale producers (50 or less animals; 64.8%). Nearly all of the respondents (95.1%) agreed that IPM workshop attendance made a difference in their ability to control and monitor parasitism in their herd or flock and employed IPM practices to control GIN (96.3%). The most popular practices respondents used were rotational grazing (71.2%), genetic selection (choosing a parasite resistant breed and/or culling susceptible animals; 52.7%), grain supplementation on pasture to improve nutrition (44.0%), and increased height of plants being grazed (41.8%). Although reporting using a practice decreased (P<0.05) the likelihood of reporting fewer problems, for each 1-point increase in the number of practices which producers employed to control internal parasitism in their herd or flock, they were 16% more likely to report fewer GIN problems (P<0.05). Approximately 75% of respondents indicated an economic benefit of IPM on their farm (P<0.05), and those reporting savings of over $80 were more likely to report fewer problems (P<0.05) with parasites after the training while those reporting no economic benefit were less likely to report fewer problems with GIN (P<0.001). Overall, IPM training resulted in positive impacts for producers responding to the survey and should continue., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The objective was to examine the effects of feeding sericea lespedeza leaf meal (SL) on control of coccidiosis in lambs. In Exp. 1, naturally infected lambs (n=76) were weaned (102.7±1.4 d of age) in May (spring) and randomly assigned in a 2×2 factorial design to receive 2% of BW/d of alfalfa pellets (control) or SL with or without amprolium added to drinking water (n=38/level or 19/treatment). Fecal oocyst counts (FOC), egg counts (FEC), and fecal score (1=solid pellets; 5=slurry) were determined every 7d between weaning and 21 d post-weaning. In Exp. 2, twin rearing ewes were randomly assigned to two groups, and their naturally infected lambs were fed a control creep supplement (16% CP; n=40) or SL pellets (14% CP; n=32) 30 d before weaning. Intake of SL was initially low (100g/lamb daily) and increased to 454 g/lamb daily after weaning. Lambs were weaned at 103.6±0.9 d of age and moved to semi-confinement. The FEC, FOC, packed cell volume (PCV), fecal score, and dag score (soiling around rear of lamb; 1=no soiling; 5=heavy soiling) were determined at d -14, 0 (weaning), 7, 14, and 21. In Exp. 3, lambs were randomly assigned to a control or SL diet (n=12/diet) fed at 1.4 kg/d for 22d and inoculated with 50,000 sporulated oocysts on d 8, 11, and 13. The FEC, FOC, and fecal score were determined every 2 to 3d between d 1 and 29 (d 0=first day of dietary treatment). Data on all experiments were analyzed using mixed models. The FOC and FEC data were log transformed. Chi squared analysis was used to determine differences in incidence of treatment (sulfadimethoxine) for coccidiosis in Exp. 1 and 2. In Exp. 1, FOC and FEC were similar between dietary groups, and FOC declined more rapidly in amprolium treated lambs following weaning (P<0.001). Fecal score was higher in the control compared with the SL fed lambs (P=0.05), suggesting more signs of coccidiosis in control lambs. In Exp. 2, FOC was similar initially but was reduced in SL fed lambs by weaning and remained lower thereafter (P=0.004). Dag (P=0.01) and fecal (P=0.001) scores were similar before weaning, but lower in SL fed lambs by weaning and remained lower thereafter. No SL lambs required treatment for coccidiosis, whereas 33% of control lambs required treatment (P<0.001). Fecal egg counts were similar before weaning but were reduced in SL compared with control fed lambs after weaning (P<0.001). In Exp. 3, FOC (P<0.001) and FEC (P<0.001) were reduced in SL compared with control fed lambs. Sericea lespedeza was effective in the prevention and control of coccidiosis as well as in reducing GIN infection. Use of SL could reduce lamb loss post-weaning, reduce the need to treat for coccidiosis, and create a significant economic benefit to livestock producers., (Published by Elsevier B.V.)

Because of a high prevalence of anthelmintic resistance and consumer demand for chemical free meat products, management tools to minimize the need for deworming are needed. The objective was to examine the effectiveness of grazing sericea lespedeza (SL) in a mixed grass or a pure forage system for control of gastrointestinal nematodes (GIN); in other words pasture systems included grass, grass plus SL, or SL alone (Experiments 2 and 3). Selective use of copper oxide wire particles (COWP) based on the FAMACHA(©) system was used to aid in GIN control. In Experiment 1, lambs co-grazed bermudagrass (BG; n=21) or SL in a mixed grass pasture (SLM; n=22) with dams for 14 days. In Experiment 2, lambs grazed BG (n=14), SLM (n=13), or pure SL (SLP; n=13) pastures for 56 days. In Experiment 3, doe kids grazed BG (n=12), SLM (n=13), or SLP (n=13) for 84 days. Animals were fed a 16% crude protein supplement based on NRC requirements and estimated forage quality of pastures, so that 454, 389, and 200 g/lamb (Experiment 2), or 454, 300, and 150 g of supplement/goat (Experiment 3) was fed to BG, SLM, and SLP, respectively. Animals were dewormed with COWP if FAMACHA(©) was >3. Coprocultures were conducted to identify GIN genus. In Experiment 1, FEC were reduced in lambs grazing SLM compared with BG pastures. In Experiment 2, FEC were reduced in SLP compared with BG lambs on all days, and reduced in SLM compared with BG lambs on day 56. Initially, Haemonchus contortus was the predominant nematode, but the population shifted to other species in the SL groups by the end of the study. The mean number of dewormings/lamb was 0.71, 0.20, and 0.21±0.13 for BG, SLM, and SLP groups, respectively. In goats in Experiment 3, Trichostrongylus spp. was the predominant nematode in May and June and H. contortus in July. There was little meaningful effect of forage treatments on GIN infection in kids. Because H. contortus was not the predominant nematode in kids, the integrated approaches used may not have been effective in controlling GIN. Grazing SL was effective for GIN control in lambs in early summer, but the effect was delayed in lambs grazing a mixed SL/grass pasture unless lambs initially grazed with dams. An integrated approach used that included SL grazing and COWP for deworming was effective in lambs., (Published by Elsevier B.V.)

Alternatives to chemical dewormers are needed to counter anthelmintic resistance and improve worm control in organic management systems. The objective was to examine the effectiveness of grazing sericea lespedeza (SL) compared with grass pastures for control of gastrointestinal nematodes (GIN) in lambs. In Experiment 1, Katahdin lambs grazed bermudagrass (BG; n=14), tall fescue (TF; n=7), or SL (n=19) pastures during early summer months. In Experiment 2, lambs grazed TF (n=15) or SL (n=13) pastures during late summer. Stocking rate of pastures was based on forage availability; additional lambs grazed pastures in Experiment 2, but were not sampled. Lambs were dewormed with 0.5 g COWP if FAMACHA(©) score was >3. In Experiment 1, FEC were reduced within 35 days in SL compared with BG lambs (forage by time, P=0.03). The PCV was more resilient to changes over time in SL compared with other groups of lambs (forage by time, P=0.001). In Experiment 2, FEC were lower (P=0.02) and PCV tended to be higher (P=0.09) in lambs grazing SL compared with TF forage. Incidence of deworming was similar among forage groups in both experiments. Grazing SL reduced FEC in lambs in early and late summer, despite reluctance by lambs to graze. Grazing forage and selective deworming using COWP was effective in lambs., (Published by Elsevier B.V.)

The objective of three experiments was to determine the impact of supplementing sericea lespedeza (Lespedeza cuneata; SL) in three concentrations in a loose or pelleted diet on gastrointestinal nematodes (GIN) in small ruminants. Experiments on lambs were conducted at the USDA, Agricultural Research Service in Booneville, AR (Exp. 1) and at Louisiana State University in Baton Rouge, LA (Exp. 2); an experiment on goat kids occurred at University of Maryland-Eastern Shore (Exp. 3). Exp. 1 used crossbred hair sheep lambs naturally infected with GIN that were randomly allocated to diets containing 0, 25, 50, and 75% SL diets (n=11 or 12/diet). Exp. 2 consisted of Haemonchus contortus-inoculated crossbred wool breed lambs that were blocked by gender and FEC and randomly assigned to 0, 25, 50, or 75% SL diet (n=8/diet). Fecal egg counts (FEC) and blood packed cell volume (PCV) were not influenced by SL supplementation in Exp. 1 and 2. Exp. 3 consisted of naturally GIN infected Boer crossbred goat kids in individual pens. Kids were blocked by FEC and randomly allotted to treatments of 0, 20, 40, or 60% SL with 9-13 goats/diet. The more SL fed, the greater the reduction in FEC (P<0.001). There was an increase in PCV in SL fed goats (P<0.001). Larval speciation at the end of the experiment indicated that feces from control animals produced 43% H. contortus larva while 20, 40 and 60% SL resulted in 39%, 35% and 31% H. contortus larvae, respectively. Feeding dried SL may be less effective in lambs than kids, though concurrent studies must be conducted to confirm this., (Published by Elsevier B.V.)

The Gulf Coast Native (Native) breed of sheep among many others is identified as being relatively resistant to Haemonchus contortus, an abomasal nematode parasite of small ruminants. Understanding the mode of immune response that helps these breeds of sheep control infection could help design and implement appropriate control programs. In this experiment, the components of the immune response during the early infection period in resistant Native lambs were evaluated and compared with susceptible Suffolk breed of sheep. Groups (n=5) of six month old Native and Suffolk lambs were given infective larvae as one time (single) or trickle experimental infections. Fecal, blood, and serum samples were collected on days 0, 2, 7, 14 and 21 post-infection. Abomasal mucosa and regional lymph node samples were collected at the time of necropsy on days 14 and 21. There was no significant difference in number of worms recovered at necropsy but the ratio of adult versus larvae was significantly greater in single infected Suffolk than Native lambs. Native lambs had significantly greater numbers of mast cells and eosinophils in the abomasal mucosa and serum IgG production was significantly greater compared to Suffolk lambs. Native lambs also showed a trend of increased level of serum IgA and IgE compared to Suffolk lambs., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Control of gastrointestinal nematodes (GIN) in small ruminants in regions of the world where anthelmintic resistance is prevalent must rely on more than just chemical deworming strategies. The objective of this experiment was to compare two integrated treatment protocols for control of GIN (primarily Haemonchus contortus in this region) using anthelmintics, copper oxide wire particles (COWP) and FAMACHA(©), compared to traditional anthelmintic use only. Three separate trials were conducted on mature ewes, weaned goats, and weaned lambs in which three deworming management strategies were applied: 1) all animals were dewormed with levamisole at four week intervals (LEV), 2) individual animals were dewormed with moxidectin when scored≥4 (ewes) or ≥3 (kids and lambs) using FAMACHA(©) (FAM/MOX), 3) all animals were dewormed with moxidectin initially and again with COWP (2g) when group mean FEC exceeded 500 (ewes), 3000 (kids), or 1000 (lambs) eggs/g (MOX/COWP). In this final group, during periods between group treatments, individual animals were dewormed with albendazole and levamisole according to FAMACHA(©) score. Fecal egg counts (FEC) and blood packed cell volume (PCV) were determined every 7 days and body weight every 28 days for 30, 20, or 16 weeks in ewes, goats, and lambs, respectively. Efficacy of levamisole was 83.4-86.4%, efficacy of moxidectin was 93.5-100%, and efficacy of COWP was 10.8-98.1% among the three trials. The mean number of deworming treatments per animal that occurred for the LEV, FAM/MOX, and MOX/COWP groups, respectively, was 7.9, 0.6, and 2.5±0.4 (P<0.001) for ewes, 5.2, 1.6, and 3.4±0.3 (P<0.001) for goats, and 4.0, 1.7, and 3.6±0.2 (P<0.001) for lambs. Production (body weight of lambs weaned from ewes or final body weight of kids and lambs) was similar among management strategy groups for ewes and kids, but FAM/MOX lambs were lighter by the end of the trial (P<0.003). While more time and labor was required to use the FAMACHA(©) system, a more conservative use of anthelmintics occurred in the FAM/MOX group., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Profitable sheep and goat production in the USA is severely limited by gastrointestinal nematode (GIN) parasitism, particularly by Haemonchus contortus. Copper oxide wire particles (COWP) have anti-parasitic properties in the diet of small ruminants, but efficacy of COWP may differ between sheep and goats. In a study with weaned kids (Kiko x Spanish cross, 6 months old) and lambs (Katahdin or Dorper x Blackface crosses, 5 months old), grazing the same pasture area in Central Georgia, 2g of COWP in a gel capsule was given to half the animals of each species, while the other half were given no COWP. Fecal and blood samples were taken weekly to determine GIN fecal egg counts (FEC) and blood packed cell volume (PCV). After COWP treatment, animals were grazed for 4 weeks and then slaughtered, with adult GIN recovered from the abomasum and small intestines for counting and identification to species. For both sheep and goats, COWP treatment reduced EPG (P<0.05), increased PCV (P<0.05), and lowered abomasal GIN numbers (P<0.05). For EPG, these differences were 82.5 and 90.5% for sheep and goats, respectively, 26 days after treatment, while adult H. contortus were 67.2 and 85.8% lower for COWP-treated sheep and goats, respectively. In this study, COWP treatment was equally effective against H. contortus infection in lambs and kids and appears to be an effective method of controlling H. contortus infection for up to 6 weeks in small ruminants following weaning.

Gastrointestinal nematode (GIN) control for 'natural' or organic lamb production is needed, especially where Haemonchus contortus is prevalent. The objective was to determine the impact of rotational grazing on GIN infection of weaned lambs. In year 1, naturally infected Katahdin lambs (120 days of age) were randomly assigned to graze (1) continuous bermudagrass (CB; n=14), (2) rotational bermudagrass moved every 3.5 days and returned to original plot 35 days later for three rotations (RB; n=14), or (3) rotational bermudagrass rotated when forage height fell below 10 cm (RBH; n=7) where first day of grazing=Day 0. In late summer, all lambs were supplemented with 500 g corn/SBM because of poor condition. The following year, similar animals were used and included the CB (n=18) and the RB (n=36) groups only. In both years, fecal egg counts (FECs) and blood packed cell volume (PCV) were determined every 7-14 days and body weight every 28 days. Individuals were dewormed with 0.5 g copper oxide wire particles (COWP) when FAMACHA score increased to 3 or more. Between 0 and 3 deworming treatments per lamb were necessary and there tended to be fewer RB than CB lambs dewormed by Day 84 for both years combined (P<0.001). Worm free tracer lambs were introduced to CB (n=6) and RB (n=8) plots following the last rotation during the first year to determine worm burdens after 20 days of grazing. Abomasal worm burden tended to be greater in RB than CB or RBH tracer lambs (P<0.10), but intestinal worm numbers were similar. Differences may be due to differences in grazing patterns among groups. Body weight gains were similar between CB and RB groups. Economic value between the CB and RB lambs was similar based on number of lambs that could have been marketed as organic. For both years, lambs relied exclusively on COWP for GIN control with the exception of one lamb. In summary, while there was a reduced incidence of deworming in the RB compared with the CB group of lambs, estimated economic value of these systems was similar.

Haemonchus contortus is one of the major nematode parasites causing substantial economic losses in small ruminant farming worldwide. Recently, effectiveness of anthelmintic treatment has decreased due to an increasing problem of nematode populations that have developed resistance to anthelmintics. Efforts to develop effective vaccines have had limited success. There are certain breeds of sheep that are relatively resistant to the parasite including Gulf Coast Native (Native) sheep. Understanding the protective nature of the immune response that helps these breeds of sheep control infection could enable the development of vaccines to enhance control programs. This experiment was designed to compare the immunological responses of resistant Native versus susceptible Suffolk sheep in order to identify the mechanisms responsible for this resistance. Immune responses were evaluated in naturally infected Native and Suffolk lambs that grazed pasture contaminated predominantly with H. contortus. Ten lambs of each breed grazed together for 42 days. Fecal, blood and serum samples were collected on 0, 2, 4, 7, 10, 14, 21, 28, 35 and 42 days of exposure. Five lambs of each breed were necropsied on day 35 and five on day 42 for nematode recovery and abomasal tissue sample collection. Throughout the course of infection, Native lambs had significantly lower FEC, significantly lower PCV reduction percent, and significantly higher serum IgE after day 14 and increased expression of IL-4 on day 10 post-exposure compared to Suffolk lambs. At both necropsy time points, Native lambs had significantly greater numbers of mucosal mast cells, eosinophils and globule leukocytes in abomasal mucosa than Suffolk lambs. Results indicated that Native lambs had a more pronounced immune response to infection with H. contortus than Suffolk lambs which may be responsible for the observed resistance to infection.

Gastrointestinal nematodes (GIN) continue to hinder small ruminant production because of anthelmintic resistance and lack of effective products for GIN control in organic production. The objective of this study was to examine the effectiveness of a commercially available certified organic garlic product, fresh garlic juice, or garlic bulbs as an anthelmintic to control GIN in goats and papaya seeds for GIN control in lambs. In the first experiment, weaned meat goat kids were administered water or a commercial garlic juice product (n=7/treatment). In the second experiment, kids were administered water, fresh garlic juice, or fed garlic bulbs (n=9 or 10/treatment). In a third experiment, lambs were administered nothing or papaya seed in water (n=12/treatment). Naturally infected goats were supplemented with bermudagrass hay and corn/soybean supplement in the first experiment or maintained on bermudagrass pasture in the second experiment or lambs grazed mixed grasses in the third. Blood and fecal samples were collected on Days 0, 7, and 14 after administration of treatment to examine changes in blood packed cell volume (PCV) and fecal egg counts (FEC). PCV and FEC were similar by Day 14 between kids treated with a commercial garlic juice and water in the first experiment. Similarly, PCV was not different among treatment groups in the second experiment. FEC of the garlic juice group was lower than the other two groups on Day 0, but was similar among groups by Day 14. Deworming was required in one goat within each treatment group by Day 7 and in three kids in the garlic juice group and two in the garlic bulb group by Day 14. No changes in PCV or FEC were apparent in response to papaya seed compared with untreated lambs. Based on the alternative plant products used in this study, garlic or papaya seed is not recommended as an aid to control GIN in goats or lambs.

High levels of anthelmintic resistance in gastrointestinal nematodes (GIN) of small ruminants have created the need for animals with greater resistance to these parasites. The objective of this experiment was to evaluate the effectiveness of the FAMACHA system in identification of parasite resilient/resistant offspring, and thus identification of stud rams with greater resilience/resistance. Katahdin ewes bred in separate groups to two sires to lamb in spring (2004, 2005: Ram A and Ram B; 2006, 2007: Ram C and Ram D) at the USDA, Agricultural Research Station in Booneville, Arkansas produced 20-40 offspring/sire each year. Ewes and lambs grazed mixed grass (predominantly bermudagrass and ryegrass) pastures and were supplemented with corn/soybean meal between 30 days pre- and 60 days post-lambing (ewes) and starting 45 days of age until weaning (lambs; 95.0+/-0.6 days of age). Blood samples and feces were collected from the lambs to determine blood packed cell volume (PCV) and fecal egg counts (FEC) and FAMACHA scores were determined at 90, 120, and 150 days of age. Lambs were dewormed if anemic (PCV<19% or FAMACHA score >2) and data removed within 30 days after deworming. Data were analyzed for the 2004/2005 and 2006/2007 groups using general linear models with year, sex of lamb, and sire nested within year as variables. Sire differences were detected (P<0.05 or less) for PCV and FAMACHA at all time points, but not FEC. There tended (P<0.10) to be sire differences for FEC at 90 and 120 days of age, but not at 150 days of age. Lambs sired by Ram D were dewormed less by 150 days of age than those sired by Ram C. The FAMACHA system can be used to identify superior sires for parasite resilience/resistance, thus increasing flock resilience, and perhaps resistance.

FAMACHA is a practical on-farm system designed to provide small ruminant producers a tool for improving their management of Haemonchus contortus infections. Although this system has become very popular and widely accepted by small ruminant producers in many regions of the southern United States, there is very limited data reported on the effectiveness of the FAMACHA system when performed by farmers. The objective of this study was to evaluate the accuracy of the FAMACHA system for on-farm use by small ruminant producers during the summer season. Small ruminant producers from Georgia, Louisiana, Florida, and Puerto Rico were trained to use the FAMACHA system by veterinarians and scientists experienced with this method. FAMACHA scores were assigned at least every 2 weeks by producers to weaned and mature sheep (n=552) and goats (n=676) of various breeds and ages between April and September 2004. At intervals that varied among farms from 2 to 8 weeks, researchers determined body condition scores (BCS; 1=thin and 5=fat) and collected blood and feces from a group of animals selected randomly to determine packed cell volume (PCV) and fecal egg counts (FEC). Two separate anemia thresholds were evaluated; these were defined by either FAMACHA score (>or=3 versus >or=4) or PCV (or=3 were considered anemic and PCV cutoff was or=3 were considered anemic and PCV cutoff was

Copper oxide wire particles (COWP) have been used to reduce infection of Haemonchus contortus in hair breed lambs in southeastern USA without signs of copper toxicity. However, copper sensitivity among breeds and regions varies. The objective was to determine the effectiveness and safety of COWP in lactating Polypay ewes and their offspring grazing alfalfa/bluegrass pasture in a rotational grazing system. Mature Polypay ewes were administered 0, 0.5, 1, or 2 g (n=8 or 9/dose) COWP approximately 60 days after lambing in mid-July 2005. Their offspring were administered 0 (n=6), 0.5 or 0.75 g (n=9), 1 or 2 g (n=6) COWP 2 weeks later in late July. The primary gastrointestinal nematode was H. contortus (70%). Between Days 7 and 35, FEC were greater in 0 and 0.5 g COWP groups compared with ewes administered 2 g COWP (COWP x day, P<0.004). PCV decreased in all groups of ewes between Days 0 and 21 (day, P<0.001). Aspartate aminotransferase (AST) activity, a measure of liver copper levels, and body weight was similar among groups of ewes. FEC decreased within 7 days in COWP-treated compared with untreated lambs and remained low throughout experiment (COWP x day, P<0.05). PCV increased in COWP-treated lambs between Days 7 and 35 and decreased in untreated lambs between Days 0 and 21 (COWP x day, P<0.009). AST activity was similar among groups of lambs. Administration of 2 g COWP to ewes prevented a rise in FEC, but a dose of 0.5 g was ineffective as an anthelmintic. Administration of all doses of COWP to lambs decreased FEC and increased PCV compared to untreated lambs. There were no signs of copper toxicity in ewes or lambs. Alternative suppression of H. contortus infections may be necessary in ewes, but COWP was effective in H. contortus management for lambs.

Parasitic infection is one of the leading economic constraints in small ruminant production. This problem is exacerbated as the resistance of nematode populations to chemical treatment (anthelmintics) becomes increasingly more common. Condensed tannin (CT) containing plants are being investigated as alternative solutions to address these problems. This investigation was conducted to evaluate the effect of the CT containing forage, Lespedeza cuneata (sericea lespedeza, SL) fed as hay, on Haemonchus contortus infection in sheep. Naturally and experimentally infected lambs were fed either SL or bermudagrass (BG, control) hay for 49 days. All lambs were fed BG hay for an additional 14 days. SL hay effectively reduced (67-98%) fecal egg count (FEC) during the time of feeding for both infection groups. FEC increased in both infection groups after SL feeding was stopped which indicated an effect on fecundity. SL hay feeding also reduced worm numbers, with more of an effect on reducing naturally infected worm burdens (67.2%) than on establishment of incoming larvae (26.1%). SL fed as hay may be more useful to remove existing worms than establishing worms. The decrease in FEC would have the benefit of reduced pasture contamination.

Gastrointestinal nematode parasitism is a concern to small ruminants worldwide. Productivity has been compromised because such nematodes, particularly Haemonchus contortus, have developed resistance to available anthelmintics. Some sheep breeds and lines within breeds are relatively resistant to infection, a trait that may be useful for developing control strategies. Suffolk sheep, which are susceptible to infection, were crossed with Gulf Coast Native sheep, which are more resistant to infection, to produce F1 progeny. F1 rams were bred to F1 ewes which produced 227 F2 offspring. These F2 offspring were evaluated for variability in infection levels, based on fecal egg count (FEC) and blood packed cell volume (PCV), under two natural infection conditions (one at weaning and another after a summer grazing period) and one experimental infection. The range of both FEC and PCV was large for all three infection periods with annual variation. Overall, the range for the three infection periods, respectively, were 167-149,933, 0-31,400 and 17-114,667 eggs per gram (EPG) of feces and 8.7-37.0%, 7.3-33.0% and 8.3-36.0%. This segregation of infection is what would be expected of F(2) progeny from susceptible and resistant parent breeds. Heritabilities of FEC and PCV for the three infection periods, respectively, were 0.15, 0.29 and 0.12, and 0.11, 0.22 and 0.12. Based on segregation of infection, larger heritabilities and maternal environment effects that declined after weaning, the summer natural infection was probably the best model for assessing genetic variation.

High levels of anthelmintic resistance in gastrointestinal nematodes (GIN) of small ruminants have created the need for alternative approaches to parasite control. Copper oxide wire particles (COWP; 2g) have proven effective in decreasing GIN infection in lambs. However, the risk of copper toxicity has limited the usefulness of this approach. Recently, smaller doses (0.5 and 1g) have proven effective in GIN control, reducing the risk of toxicity. The objective of this study was to examine the effectiveness and risk of toxicity using multiple small doses of COWP for GIN control in lambs between weaning and market weight. Dorper crossbred ram lambs were orally administered levamisole (Levasol, 8.0mg/kg; n=8), 0.5g (n=9), or 1g COWP (n=9) at weaning (Day 0; 118+/-2 days of age; late May 2005) and again at 6-week intervals for a total of four treatments. A pooled fecal culture determined that Haemonchus contortus was the predominant gastrointestinal parasite at weaning. Lambs grazed bermudagrass pastures and were supplemented with up to 500g corn/soybean meal and free choice trace mineralized salt. Fecal egg counts (FEC), packed cell volume (PCV), and plasma aspartate aminotransferase (AST) activity were determined every 14 days and lambs weighed every 28 days. GIN infection reached a peak at Day 42 (high FEC, low PCV). COWP effectively reduced FEC on Days 0 and 42 compared with the previous week, but did not reduce FEC on Days 84 and 126 (treatment by time interaction, P<0.005). Plasma AST activity and weight gains were similar among treatment groups throughout the study period. Concentrations of copper in the liver on Day 155 were greater in COWP-treated lambs (P<0.001), but all concentrations were normal. Multiple doses of COWP were as effective as levamisole for control of H. contortus without risk of copper toxicity.

It has been reported that CD4(+) T lymphocytes are important in acquired immunity to gastrointestinal nematode infection. Whether these lymphocytes are also involved in the immune response of naturally resistant Gulf Coast Native (GCN) sheep to Haemonchus contortus infection remains to be defined. The objective of this study was to determine the role of CD4(+) T lymphocytes in this resistance. Ten GCN lambs were randomly assigned to a control (n=5) or a treatment (n=5) group. The treatment consisted of a series of IV injections with mouse anti-ovine CD4(+) T lymphocyte monoclonal antibodies for a period of 3 weeks. After the second treatment, all lambs were experimentally infected with 10,000 H. contortus infective larvae by oral inoculation. All lambs were monitored for fecal egg counts, blood packed cell volumes, white blood cell differential counts and serum antibody responses on a weekly basis. Fluorescence-activated cell sorter (FACS) analysis was done biweekly to enumerate CD4(+) T lymphocytes in peripheral blood. Necropsies were performed at the end of the study and 10% of the contents of the gastrointestinal tract were preserved for nematode enumeration and identification. Also at necropsy, mesenteric lymph nodes were extracted and FACS analysis was run on lymphoid cells. Mean fecal egg counts on day 21 and 28 post-infection and nematode counts at necropsy of the treated group were significantly (p<0.05) higher than that of the control group. Percent CD4(+) T lymphocytes in peripheral blood was significantly (p<0.05) lower in the treatment group than in the control group from day 9 to the end of the study. No differences were found in blood packed cell volumes, white blood cell differential counts, antibody titer or lymph node CD4(+) lymphocytes between groups. Lambs depleted of their CD4(+) T lymphocytes were more susceptible to H. contortus infection than undepleted lambs. The results of this study suggest that CD4(+) T lymphocytes are associated with the natural resistance of GCN sheep to H. contortus infection.

Gastrointestinal nematode parasitism is arguably the most serious constraint affecting sheep production worldwide. Economic losses are caused by decreased production, the costs of prophylaxis and treatment, and the death of the infected animals. The nematode of particular concern is Haemonchus contortus, which can cause severe blood loss resulting in anemia, anorexia, depression, loss of condition, and eventual death. The control of nematode parasites traditionally relies on anthelmintic treatment. The evolution of anthelmintic resistance in nematode populations threatens the success of drug treatment programs. Alternative strategies for control of nematode infections are being developed, and one approach is to take advantage of the host's natural or acquired immune responses, which can be used in selection programs to increase the level of resistance in the population. Vaccination can also be used to stimulate or boost the host's acquired immunity. The induction of protective resistance is dependent on the pattern of cytokine gene expression induced during infection by two defined CD4+ T-helper cell subsets, which have been designated as Th1 or Th2. Intracellular parasites most often invoke a Th1-type response, and helminth parasites a Th2-type response. Breeds of sheep resistant to infection have developed resistance over a much longer term of host-parasite relationship than genetically selected resistant lines. The immune components involved in these different responses and types of host-parasite relationships will be reviewed. The potential for using vaccines has been investigated, with variable results, for several decades. The few successes and potential new antigen candidates will also be reviewed.

An experiment was completed to determine if copper oxide wire particles (COWP) had any effect on the activity of the nematode-trapping fungus Duddingtonia flagrans in growing lambs. COWP has been used recently as a dewormer in small ruminants because of nematode resistance to anthelmintics. D. flagrans has been used to control free-living stages of parasitic nematodes in livestock. Katahdin and Dorper lambs, 4 months of age, were administered no or 4 g COWP (n=24/dose) in early October 2003. Haemonchus contortus was the predominant gastrointestinal parasite during the trial, which was acquired naturally from pasture. Half the lambs from each COWP group were supplemented with corn/soybean meal with or without D. flagrans for 35 days. Fecal egg counts (FEC) and packed cell volume (PCV) were determined weekly between days 0 (day of COWP administration) and 35. Feces from lambs in each treatment group were pooled and three replicates per group were cultured for 14 days at room temperature. Larvae (L3) were identified and counted per gram of feces cultured. Treatment with COWP was effective in decreasing FEC, which remained low compared with FEC from lambs not treated with COWP. This led to an increase in PCV in these lambs (COWP x day, P<0.001). Number of larvae was decreased in feces from lambs treated with COWP and D. flagrans between days 14 and 35 compared to the other groups of lambs (COWP x D. flagrans x day, P<0.003). Percentage of larvae identified as H. contortus decreased in feces collected from lambs treated with COWP and D. flagrans between days 14 and 28 compared with other treatments (COWP x D. flagrans x day, P<0.05). Other trichostrongyles were present and remained less than 7% in feces collected from control lambs. There was no adverse effect of COWP on the ability of D. flagrans to trap residual larvae after COWP treatment. With fewer eggs being excreted due to the effect of copper on H. contortus, and the additional larval reducing effect exerted by the nematode destroying fungus D. flagrans, the expected result would be a much lower larval challenge on pasture when these two tools are used together in a sustainable control strategy.

The objective of the experiment was to determine the effectiveness of copper oxide wire particles (COWP) in pregnant ewes and safety to lambs. COWP have been used recently as an anthelmintic in small ruminants to overcome problems associated with nematode resistance to chemical dewormers. Doses of COWP (

The objective of the experiment was to determine the optimal dose of copper oxide wire particles (COWPs) to reduce infection of Haemonchus contortus in male lambs. Five to six-month-old hair breed lambs were housed on concrete and fed 450 (L; n = 25) or 675 g (H; n = 25) corn/soybean meal supplement and bermudagrass hay. In July, lambs were inoculated with 10,000 L(3) larvae (97% H. contortus; Day 0). Lambs were administered 0, 2, 4, or 6 g COWP on Day 28. Concentrations of copper in the liver were determined. There were no effects of supplement level on concentrations of copper in the liver and a linear relationship existed between COWP treatment and concentrations of copper in liver (P < 0.001). Least squares means of the 0, 2, 4, 6 g COWP treatments were 62.2, 135.7, 161.1, and 208.4 ppm (P < 0.001). Between Days 0 and 28, PCV declined and by Day 42, PCV of all COWP-treated lambs was markedly higher than control lambs and remained higher (COWP x day, P < 0.05). By Day 21, PCV was greater in the H compared with the L group of lambs (P < 0.001). Within 14 days of COWP treatment FEC declined from more than 8000 eggs/g (epg) to less than 250 epg in all COWP-treated lambs (COWP x day, P < 0.001). The numbers of H. contortus in the abomasum were greatly reduced in all COWP-treated groups of lambs and remaining nematodes were predominantly males. FEC were greater in L versus H supplemented lambs and values decreased to a greater extent in H lambs when treated with COWP (supplement x COWP; P < 0.02). The 2 g COWP was effective in alleviating H. contortus infection and reducing number of egg-laying nematodes in the abomasum with the lowest concentration of copper in the liver of the COWP treatment groups. PCV values were more favorable for lambs fed the higher level of supplement, especially when FEC were greater than 8000 epg.

Recent studies on sheep and goat farms in the southern United States indicate that multiple-anthelmintic resistance in Haemonchus contortus is becoming a severe problem. Though many factors are involved in the evolution of resistance, the proportion of the parasite population under drug selection is believed to be the single most important factor influencing how rapidly resistance develops. Therefore, where prevention of resistance is an important parallel goal of worm control, it is recommended to leave a portion of the animals untreated. Recently, a novel system called FAMACHA was developed in South Africa, which enables clinical identification of anemic sheep and goats. When H. contortus is the primary parasitic pathogen, this system can be applied on the farm level to reduce the number of treatments administered, thereby increasing the proportion of the worm population in refugia. Since most studies validating the FAMACHA method have been performed in South Africa, it is important that the method be tested in other regions before its use is broadly recommended. We performed a validation study of FAMACHA by testing the system in sheep (n = 847) and goats (n = 537) of various breeds and ages from 39 farms located in Arkansas, Georgia, Louisiana, Florida, and the US Virgin Islands. The color of the ocular conjunctiva of all animals were scored on a 1-5 scale using the FAMACHA card, and blood samples were collected from each animal for determination of packed cell volume (PCV). Fecal samples were also collected from a majority of the animals tested for performance of fecal egg counts (FEC). Correlations between PCV and eye scores, PCV and FEC, and FEC and eye scores were all highly significant for both sheep and goats (P < 0.001). Data for both FAMACHA scores and PCV were evaluated using two separate criteria for anemia: eye score values of 3, 4 and 5 or 4 and 5, and PCV values of < or =19 or < or =15 were considered anemic. Specificity was maximized when eye score values of 4 and 5 were considered anemic and PCV cut off for anemia was < or =19, but sensitivity was low. In contrast, sensitivity was 100% for both sheep and goats when eye score values of 3, 4 and 5 were considered anemic and PCV cut off was < or =15, but specificity was low. In both sheep and goats, predictive value of a negative was greater than 92% for all anemia and eye score categories, and was greater than 99% for both eye score categories when an anemia cutoff of < or =15 was used. Predictive value of a positive test was low under all criteria indicating that many non-anemic animals would be treated using this system. However, compared to conventional dosing practices where all animals are treated, a large proportion of animals would still be left untreated. These data indicate that the FAMACHA method is an extremely useful tool for identifying anemic sheep and goats in the southern US and US Virgin Islands. However, further studies are required to determine optimal strategies for incorporating FAMACHA-based selective treatment protocols into integrated nematode control programs.

Neonatal and weaner Gulf Coast Native (Native) lambs were studied to determine whether an immunological basis underlies their natural resistance to Haemonchus contortus infection. Neonatal Native lambs (n = 8) and weaner Native lambs (n = 15) were randomly assigned to a treatment or a control group. Lambs in the treatment group received dexamethasone by intramuscular injection three times a week for 10 weeks (neonatal) and 15 weeks (weaners). All lambs were monitored for fecal egg count (FEC), blood packed cell volume (PCV), and white blood cell differential counts on a weekly basis for the duration of the studies. Neonatal lambs were kept on pasture with their dams and weaner lambs were dewormed at weaning and kept in pens where they received trickle infections. Serum antibody titers to H. contortus whole worm antigen (WWA) were determined using ELISA. Lymphocyte proliferation assays on peripheral blood mononuclear cells (PBMC) were done to assess lymphocyte function. All lambs were vaccinated with killed Brucella abortus strain 19 to assess the effect of dexamethasone treatment on antibody response. All lambs were necropsied at the end of each study to recover the contents of the gastrointestinal tract for nematode enumeration and identification. The results showed that mean FEC and mean PCV of the treatment group was significantly higher and lower, respectively, than in the control group in both neonatal and weaner lambs from weeks 6 and 5, respectively. At necropsy, total nematode count was significantly higher in treatment groups than in the control groups. Serum antibody titers to H. contortus WWA were significantly lower in treated groups than in control groups. Treatment groups showed a consistent depression in lymphocyte percentage being significantly lower from week 6 in both neonatal and weaner lambs. No differences were found in the response of PBMC to mitogen stimulation between the groups. Lambs in the control groups showed strong positive brucellosis card tests and the treatment groups did not. Dexamethasone treatment resulted in depression of the immune response and loss of natural resistance of Native lambs to H. contortus infection. The results of these studies suggest that some aspects of the immune response may underlie the natural resistance of Native sheep to H. contortus infection.

Gastrointestinal nematodes are of concern in sheep production because of production and economic losses. Control of these nematodes is primarily based on the use of anthelmintic treatment and pasture management. The almost exclusive use of anthelmintic treatment has resulted in development of anthelmintic resistance which has led to the need for other parasite control options to be explored. The blood sucking abomasal parasitic nematode Haemonchus contortus causes severe losses in small ruminant production in the warm, humid sub-tropic and tropics. This study evaluated the effectiveness of a nematode trapping fungus, Duddingtonia flagrans, in reducing availability of parasitic nematode larvae, specifically H. contortus, on pasture. Chlamydospores of D. flagrans were mixed with a supplement feed which was fed daily to a group of crossbred ewes for the duration of the summer grazing season. A control group was fed the same supplement feed without chlamydospores. A reduction in infective larval numbers was observed in fecal cultures of the fungus-fed group. Herbage samples from the pasture grazed by the fungus-fed group also showed a reduction in infective larvae. There were no significant (P > 0.05) differences in overall fecal egg count, packed cell volume or animal weight between fungus-fed and control groups. Tracer animals were placed on the study pastures at the end of the study to assess pasture infectivity. Although tracer animals were only two per group, those that grazed with the fungus-fed group had substantially reduced (96.8%) nematode burdens as compared to those from the control group pasture. Results demonstrated that the fungus did have activity against nematode larvae in the feces which reduced pasture infectivity and subsequently nematode burdens in tracer animals. This study showed that D. flagrans, fed daily to grazing ewes, was an effective biological control agent in reducing a predominantly H. contortus larval population on pasture.

A study was conducted to evaluate relative resistance of Dorper crossbred (DO), Katahdin (KA), St. Croix (SC), and Hampshire (HA) ewes to natural and experimental gastro-intestinal (GI) nematode infection over a 20-month period. The objective of Experiment 1 was to evaluate breeds for resistance to infection acquired naturally from mixed grass pastures. In Year 1 (May-December 2000) de-worming of ewes occurred during wet, hot conditions in July and during late pregnancy in December. In Year 2 (January-December 2001), ewes were de-wormed after fecal egg count (FEC) for a breed group rose above 1000 eggs per gram (epg) or after blood packed cell volume (PCV) of an individual ewe fell below 20. FEC was determined every 28 days and PCV every 14-28 days. In both the years, ewes were pastured together, except during the 28-days breeding periods, on tall fescue, bermudagrass, or ryegrass, and rotated among pastures dependent on forage availability. Ewes were in good or excellent condition (body condition score of 3-4 out of 5) throughout the study. The objective of Experiment 2 was to evaluate the breeds for relative resistance to an experimental infection with Haemonchus contortus infective larvae. Both PCV and FEC were determined every 7 days from 14 to 42 days after inoculation with 30000 infective larvae per ewe. In Experiment 1, Year 1, FEC was slightly greater and PCV was lower from July to September in DO ewes (breed x time, P<0.001). In Year 2, de-worming occurred 14 days later in DO ewes compared with other breed types. Otherwise PCV and FEC were similar among the hair breeds and higher and lower, respectively, compared with HA ewes (breed x time, P<0.001). In Experiment 2, FEC and PCV were similar among hair breeds; FEC was lower and PCV higher in hair breeds compared with that of HA ewes (P<0.01). Relative resistance of mature Dorper crossbred ewes was comparable to that of Katahdin and St. Croix ewes and superior to that of Hampshire ewes.

Consequences of nematode infections due to Haemonchus contortus are a serious constraint for the sheep industry worldwide. Development of anthelmintic resistance and increasing concern about the impact of anthelmintic use dictate the need of alternative control. Such an alternative is using the nematode trapping fungus Duddingtonia flagrans to reduce infective larvae levels on pasture. Two trials were conducted to determine the effect of D. flagrans in reducing infective larvae (predominantly H. contortus) in feces. The first trial determined the dose effect of D. flagrans in reducing infective larvae in feces. Eighteen ewes were dewormed to remove existing infections and randomly assigned to six treatment groups: 5 x 10(4), 1 x 10(5), 2.5 x 10(5), 5 x 10(5), 1 x 10(6) or no (control) spores of D. flagrans per kg of body weight mixed in their feed for 7 days. Fecal samples were collected daily from these and from infected donor ewes. Feces from individual-treated ewes were mixed with equal amounts of donor ewe feces, theoretically approximating oral dose spore concentrations of 2.5 x 10(4), 5 x 10(4), 1.25 x 10(5), 2.5 x 10(5), 5 x 10(5) and no spores, and were cultured. Across dosages and during the 7 days of fungus feeding, percent reduction of infective larvae ranged from 76.6 to 100.0%. The second trial determined the effect of D. flagrans at the dose of 10(5) spores per kg body weight on reducing infective larvae in feces from naturally infected lambs. Twenty lambs were randomly assigned to either treatment or control groups based on fecal egg count. Treatment lambs were fed spores mixed in feed for 7 days. Feces were collected daily and cultured. During the 7 days of fungus feeding, the percent reduction of infective larvae ranged from 82.8 to 99.7%. Results of these trials demonstrated that the nematode trapping fungus D. flagrans was highly effective in reducing infective larvae in sheep feces and should be considered as a biological control agent for integrated nematode control programs.

A crossbreeding program was conducted to evaluate the resistant status to gastrointestinal nematode parasite infection in crossbred (F1) lambs and their Suffolk and Gulf Coast Native (Native) breed counterparts. A total of 253 lambs were included in the study over 2 years. Fecal egg count (FEC) and blood packed cell volume (PCV) of 18-20 monitor lambs of each breed group in each year were collected every other week from birth to 24-30 weeks of age. The FEC and PCV of all lambs were determined at weaning (11-12 weeks of age) and at three subsequent times when anthelmintic treatment was administered. Nematode counts of wether lambs were obtained at 30 weeks of age in the first year. The epidemiological patterns of FEC and PCV of each breed group were similar in both years. The Suffolk group consistently showed the highest FEC and the lowest PCV. Conversely, the Native group had the lowest FEC and highest PCV. For the most part, all parameters for the F1 group fell intermediate to the Native and Suffolk groups. Nematode count followed the same pattern. Heterosis analysis showed that FEC, PCV, nematode count and weight gain of the F1 group favored the Native group. These results suggested that crossbreeding Suffolk to Native sheep may be a suitable way to produce lambs with improved resistance to gastrointestinal nematode infection, but production may be compromised.

A vaccination trial was conducted to evaluate the potential benefit of Haemonchus contortus gut membrane proteins as vaccine antigens under field conditions in Louisiana. The trial was conducted in the summer of 1996 in a flock of ewes grazing pasture naturally infected with H. contortus. Ewes were randomly assigned to three treatment groups (vaccine, adjuvant only, and saline) and fecal egg counts (FEC, measured as eggs per gram of feces), packed cell volumes (PCV), and antibody levels were monitored fortnightly for 12 weeks. It was shown by FEC that there were large individual variations in susceptibility to H. contortus in both vaccinated and non-vaccinated sheep, a finding which could have masked differences between treatments when analyzed by conventional statistical methods. Based on their egg counts before the period when the vaccination could have had an effect, all ewes were categorized as 'susceptible' or 'relatively resistant'. The significance of differences between FEC, PCV and antibody responses of vaccinated and control sheep were tested separately for the 'susceptible' and 'relatively resistant' category. The 'susceptible' vaccinates shed 65% fewer worm eggs during the period when the vaccine could have had an effect, but the difference was only significant on Week 6 post-vaccination. In these experiments, it was difficult to completely exclude the confounding effect of having 'relatively resistant' sheep in the control group. More studies are needed to further evaluate H11 and H-gal-GP antigens under field conditions.

An eight-year study was conducted to define the epidemiology of gastrointestinal nematode infection in Suffolk and Gulf Coast Native (Native) breeds of sheep, and to determine if the Native sheep is more resistant to infection. For the initial three years, each breed grazed separate pastures where anthelmintic treatments were administered to individual animals on a salvage basis. For the last five years, both breeds grazed concurrently; anthelmintic treatments were administered to individual animals on a salvage basis for the first three years, and to all animals, when treatment criteria were met, for the last two years. The fecal egg count (FEC) and blood packed cell volume (PCV) were monitored, and tracer lamb nematode burdens were determined. Overall, FEC for both breeds increased in the spring (periparturient rise) for most years and in the summer for all years. Under separate grazing conditions, Native ewes and lambs had consistently lower infection levels than Suffolk ewes and lambs. During the haemonchosis season (June-September) each year, Suffolk ewe and lamb PCV decreased, and Native ewe and lamb PCV remained relatively stable. The salvage treatment protocol resulted in 27 treatments for Suffolk and one for Native ewes; similarly for lambs, 13 for Suffolk and zero for Native. Tracer lambs grazed with their respective breed, and the FEC and mean total nematode burden corresponded with the pattern of infection for their respective breed. The predominant nematodes found in Suffolk and Native tracer lambs were Haemonchus contortus and Trichostrongylus spp., respectively. Under concurrent grazing conditions, the same seasonal repeatable pattern of infection was present and was exhibited by both breeds, with the Native ewes and lambs being consistently and significantly (p < or = 0.05) lower for FEC and higher for PCV. The salvage treatment protocol resulted in 57 and zero treatments for Suffolk and Native ewes, respectively; for lambs, 46 and 11. Tracer lamb nematode burdens again corresponded to their respective breed pattern of infection, with H. contortus and Trichostrongylus spp. being predominant in Suffolk and Native lambs, respectively. Data from all tracer lambs showed a relatively low level of hypobiosis (H. contortus only), and, although there was no consistent hypobiosis season, the tendency was for a higher level to occur in the fall. These results showed that the classic repeatable seasonal pattern of gastrointestinal nematode infection occurred in both breeds of sheep, and that Native sheep were more resistant to infection (specifically H. contortus) than Suffolk sheep.

Three trials compared responses to naturally-acquired strongylate nematode infection between suckling Suffolk and Gulf Coast Native (Native) lambs which grazed together. In Trial 1 (1992), infection in 14 lambs of each breed was monitored from birth to 12 weeks of age using fecal egg count (FEC) and blood packed cell volume (PCV). In Trial 2 (1993), two age-matched lambs of each breed were sacrificed at seven and ten weeks of age to estimate nematode burdens. In Trial 3 (1994), infection in 18 lambs of each breed was monitored (FEC, PCV, white blood cell count, differential leukocyte count, and anti-Haemonchus contortus immunoglobulin level) from birth to 8 weeks of age, at which time six age-matched lambs of each breed were sacrificed to estimate nematode burdens. The remaining 24 lambs were monitored until 12 weeks of age. In both Trials 1 and 3, infection in Native lambs peaked and then declined between 6-10 weeks of age. Infection in Suffolk lambs continued to increase as evidenced by increasing FEC with concomitant reduction in PCV, higher morbidity and mortality (Trial 1), and number of anthelmintic treatments required (Trial 3). In Trials 2 and 3, the principal nematode found at necropsy was H. contortus, and infection level was consistently lower (> 64%) in Native compared with Suffolk lambs. In Trial 3, there was no difference between breeds for WBC, any leukocyte type, or anti-H. contortus immunoglobulin level. These results demonstrated that suckling Native lambs developed resistance to H. contortus infection during their first exposure to infection at an age when they are considered immune incompetent and colostrally transferred anti-H. contortus immunoglobulin did not appear to be involved in the resistance.

The prevalence and identification of Eimeria spp. in the Louisiana State University ewe flock were determined from 109 fecal samples. Unsporulated oocysts were recovered from 94 of the samples and 1208 oocysts representing ten species of Eimeria were identified: E. ahsata, E. crandallis, E. Faurei, E. granulosa, E. intricata, E. ovina, E. ovinoidalis, E. pallida, E. parava and E. punctata. Eimeria ovinoidalis, which is probably the most pathogenic, was the species common to the most number of samples (59.6%); however, E. granulosa, which is non-pathogenic, was the most numerous species (23.7% of the total identified). The prevalence and identification of oocysts from ewes may be useful to evaluate infection potential when considering control programs, especially for lambs.

Levamisole, morantel, fenbendazole, or ivermectin was administered at 2-week intervals from May 1 through Sept 14, 1985, to breeding ewes (20 ewes/drug) infected with various gastrointestinal nematodes. All ewes had fewer gastrointestinal nematode eggs per gram of feces (epg) after 2 treatments, compared with pretreatment epg counts. Ewes administered ivermectin continued to have a low mean epg (0 to 3) throughout the study. The mean epg counts of ewes treated with levamisole increased from 3 to 483 during the study. This increase was similar to that of ewes treated with morantel (7 to 485 epg). The mean epg count of fenbendazole-treated ewes increased from 4 to 192 during the study. By the end of the study, the mean epg counts when expressed as a percentage of the pretreatment epg counts were 4% (ivermectin), 249% (fenbendazole), 627% (levamisole), and 630% (morantel). With the exception of the ivermectin-treated ewes, the epg count increased almost linearly in the ewes after the 2nd anthelmintic treatment. These data indicate that the gastrointestinal nematodes (including Haemonchus contortus) may have developed more resistance to levamisole and morantel than to fenbendazole. On the basis of the epg counts, resistance to ivermectin did not develop during the 4.5-month treatment period. The percentage of ewes shedding eggs after 2, 4, and 6 anthelmintic treatments was lowest for ewes treated with ivermectin (20%) and was similar (40%) for ewes treated with 1 of the other 3 anthelmintics. At the conclusion of the study, most of the ewes (90%) were shedding at least a small number of eggs, regardless of the anthelmintic treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of levamisole was evaluated in a suspected levamisole-resistant population of Haemonchus contortus in the Louisiana State University sheep flock. The efficacy of netobimin also was evaluated against this population of Haemonchus. In trial 1, 5 lambs naturally infected with H contortus were given 8 mg of levamisole/kg of body weight as a drench, and 5 lambs were not treated (controls). Nematode recovery after slaughter indicated 0% efficacy against H contortus. In trial 2, 30 nematode-free lambs were each given 8,300 F1 generation infective larvae of H contortus, which were derived from parent H contortus that survived 2 levamisole treatments in lambs being maintained in a nematode-free environment. Ten lambs were treated with 8 mg of levamisole/kg as a drench, 10 were treated with 20 mg of netobimin/kg as a drench, and 10 were not treated (control). Nematode recovery after slaughter revealed 62.3% and 99.8% efficacy for levamisole and netobimin, respectively, against H contortus.

Ten parasite-free experimental lambs were inoculated intraruminally with a mixed-larvae inoculum which contained approximately 5,000 Haemonchus contortus infective larvae. Five lambs were treated with thiabendazole (66 mg/kg of body weight) and 5 were untreated controls. All lambs were killed 35 days after inoculations were done, and parasites present were recovered. Reduction in numbers of recovered Haemonchus contortus (25.7%) and Ostertagia spp (26.8%) were not significant (P greater than 0.05).