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Cross-reactivity between Hypoderma lineatum antigen and anti-Przhevalskiana silenus antibodies has been demonstrated by an ELISA technique. To evaluate the applicability of a commercial ELISA kit for the immunodiagnosis of goat warble fly infestation, different dilutions of serum and conjugate were tested, the development of antibody to P silenus in naturally infested goats was studied, and the results were compared with an ELISA technique using an antigen extracted from the first instar larvae of H lineatum. The best results were obtained with a serum dilution of 1:50; with both techniques the highest antibody concentration were recorded in October, November and December. In view of the confirmed cross-reactivity between H lineatum antigen and anti-P silenus antibodies, and the simplicity and rapidity of the assay, the commercial ELISA kit can be considered as a useful tool for the diagnosis of goat warble fly infestation.

Objective: To determine effectiveness of a pour-on formulation of doramectin against Damalinia bovis, Haematopinus eurysternus, Linognathus vituli, Solenopotes capillatus, Chorioptes bovis, Sarcoptes scabiei, Hypoderma bovis, and Hypoderma lineatum., Animals: Cattle of various ages with naturally acquired or artificial infestations with 1 or more species of lice, mites, or grubs., Procedure: In 10 louse and 6 mite studies, cattle were treated with doramectin (500 microg/kg, topically) on day 0, and parasite counts were performed approximately weekly from days 0 to 35. In 6 grub studies, cattle expected to harbor Hypoderma spp were treated before emergence of warbles. After warbles began to emerge, they were counted every 2 weeks, and grubs were collected and identified by species., Results: Burdens of D bovis, H eurystemus, L vituli, and S capillatus on doramectin-treated cattle were 0 by 28 days after treatment. Burdens of C bovis and S scabiei decreased to 0 in naturally infested cattle and approximately 0 in artificially infested cattle by day 14 to 15. In grub studies, 107 of 136 control cattle had warbles, whereas 2 of 136 doramectin-treated cattle had 1 warble each, which represented a cure rate of 98.5%., Conclusion and Clinical Relevance: One topical application of doramectin was highly efficacious against common species of lice, mites, and grubs known to affect performance, health, and appearance of cattle.

Myiasis is a problem of Medical and Veterinary importance worldwide. It affects human welfare both directly and indirectly. ELISA kit hypodermosis was evaluated in detecting antibodies against two oestrid larvae, Przhevalskiana silenus in goats and Cephalopina titillator in camels. Both animals were parasitologically proved to have oestrid myiasis infestation. Antibodies against P. silenus were detected in 38 out of 40 (95%) infested goats and negative results among the control group. With C. titillator, antibodies were detected in 39 out of 40 (97.5%) infested camels. But one of the control (10%) gave false seropositivity. ELISA kit hypodermosis diagnosed antibodies against P. silenus in goats and C. titillator in camels. Consequently, there are cross reactions between anti-hypoderma antibodies and antibodies against both Przhevalskiana and Cephalopina. ELISA is confirmed to be an easy and economic tool in diagnosing myiasis infestation when direct examination is not a simple mean and/or for epidemiological studies. The whole results were discussed. Focusing on the clinical pictures and pathogenesis of human myiasis was included to clarify the zoonotic importance of myiasis in Egypt.

To evaluate the cross-reactivity between Hypoderma lineatum antigen and anti-Przhevalskiana silenus antibodies six protocols with different concentrations of antigen and different dilutions of sera and conjugate were applied. The highest cross-reaction between the H. lineatum antigen and the anti-P. silenus antibodies is given by 2 micrograms/ml of antigen concentration, 1:400 of serum and 1:10,000 conjugate dilution. The study on the kinetic development of antibodies in goats naturally infested by P. silenus and the natural course of infestation pointed out the existence of a good correlation between individual antibody kinetics and the natural evolution of the cycle of infestation. The highest antibody concentration may be registered from October through November, coinciding with the end of the migration fo the larvae inside the animal's body. In our condition, this period can be considered as a favorable sampling period for immunodiagnosis and immunoepidemiological studies of goat warble fly infestation.

The activity of the moxidectin as an 1% w/v injectable solution on first instar Hypoderma spp. has been evaluated in sixteen naturally infested young cattle. The animals were selected on the basis of their serological status and allocated to two groups of eight animals. At the end of November, one group was treated with moxidectin at a dose rate of 0.2 mg/kg via the subcutaneous route and the non treated control calves injected with the vehicle. The serological status was assessed 1, 2, 4, 8 and 12 weeks post treatment and the presence of Hypoderma lumps determined every two weeks from February to June. A 100% efficacy of the injectable formulation was demonstrated. A progressive fall of the antibody levels was observed in the treated calves for one month following treatment, suggesting a progressive action of the test compound and a limited risk of hypersensitivity.

A new method for collecting 3rd-instar Hypoderma lineatum (Villers) and Hypoderma bovis (L.) is described. A procedure for carrying out chronobiological and other studies involving the life cycle of these flies is included. The larvae are collected from cattle using a dressing made of a circle of cardboard attached to a piece of tulle similar in color to the coat of the animal. These small cloth cages were attached to the animal skin with fast-drying contact glue wherever the swellings produced by 2nd- or 3rd-instar Hypoderma spp. had been previously detected. Each animal was inspected daily to detect the appearance of new larvae. This procedure allows the collection of each emerged larva without contact with other larvae and avoids friction of the cloth cages or dressing with the larvae, thus reducing larval death and increasing viability of the parasite.

Objective: To determine the efficacy of a topical formulation of eprinomectin against natural infestations of first (L1)-stage, and second and third (L2/L3)-stage larvae of Hypoderma spp., Animals: 140 approximately 6- to 18-month-old cattle of various breeds., Procedure: Cattle, selected from herds with high prevalence of Hypoderma infestation, were treated in 4 experiments: within each replicate, 1 animal received eprinomectin at a dosage of 500 micrograms/kg of body weight against first-stage larvae (L1). The second animal received the same treatment against second or third-stage larvae (L2/L3). The third animal served as an untreated control. In a fifth experiment, visible warbles were treated on half of the cattle. Remaining cattle served as vehicle-treated controls. In 1 experiment, warbles were examined from time of treatment until all lesions were resolved. In 4 experiments, emerging Hypoderma larvae were recovered, speciated, and enumerated, and viability was determined., Results: Eprinomectin (500 micrograms/kg) efficacy was complete against L1. Hypoderma L2/L3 eradication approached 100% efficacy (1 live larva was recorded). Warbles in treated cattle resolved in a significantly shorter time than did those in controls. Adverse reactions related to treatment were not observed in any of the trials., Conclusions: Eprinomectin (500 micrograms/kg) applied topically was safe and highly efficacious for treatment of all larval stages of Hypoderma spp in these trials., Clinical Relevance: Attributes of eprinomectin besides antiparasite efficacy allow treatment of all classes of cattle with no need for meat or milk withdrawal.

The efficacy of different drugs (microdose of ivermectin, doramectin and moxidectin at the recommended doses and topically applied rotenone) against the first, second and third instar larvae of Hypoderma bovis and H. lineatum was studied in cattle in the El Tarf area (northeastern Algeria). Before performing the efficacy trials, the life cycle of the warble fly was studied at the slaughterhouse between July 1993 and June 1994. This survey revealed that both species of warble fly were present in this area: L1 larvae of H. lineatum were found around the oesophagus between August and January, whereas L1 larvae of H. bovis were observed around the spine from November until March. Warbles were present under the skin from the end of October until May. The nymphal phase took place between February and May. As a result of this study the authors recommend applying chemoprophylaxis (treatment against L1) in September. This work also confirmed the excellent efficacy of avermectins and milbemycins against the three instar larvae of Hypoderma sp. under the field conditions prevailing in Algeria. Rotenone has a lower efficacy (95%) which is limited to the second and third instar larvae. However, this drug appears useful in dairy cattle.

The field efficacy of two avermectins (ivermectin and doramectin) and the subsequent development of the antibody response were assessed in cows naturally infested with first-instar larvae (L-1) of Hypoderma sp. Twenty-eight Frisian cows were randomly divided into three groups while the first-instar larvae were still in migration: Group 1 (G-C) untreated control; Group 2 (G-Iv), treated with ivermectin injectable (0.2 mg kg-1 body weight) and Group 3 (G-Dor), which received doramectin injectable (0.2 mg kg-1 body weight). Serum antibody response was studied by an indirect ELISA test using, as antigen, the hypodermin C obtained from L-1 of H. lineatum. In treated animals no grubs were present on the back at any time during the trial, whereas a variable number of nodules were found in untreated animals. Both avermectins showed total efficacy against L-1 of Hypoderma sp., and there were no local or general reactions. In ivermectin-treated cattle serum antibody levels declined from one month p.t., while in those treated with doramectin they started to fall two weeks later, but no differences were found among both groups. On the other hand, G-C antibody levels progressively increased and remained high until December, when the first grubs became detectable on the back; after that, they began to decline. Early treatments against Hypoderma sp. have an influence on the results of ELISA, so they must be considered to determine the most suitable time for blood sampling.

Hypodermosis is a common parasitic disease of great importance on cattle production and breeding worldwide. In Greece, no reliable data are available regarding the extent of this infection and therefore, as expected, no national or regional control programme is being applied. In order to cover this lack of information, a total of 4200 cattle blood sera were collected from different parts of the country and tested for hypodermosis using the ELISA method. The prevalence of the infection was found to be 37.4%, varying from place to place between 0.7 and 78.8%. The range of the infection per flock was from 0 up to 100%.

Hypodermyiasis is a common myiasis which affects a wide variety of deer species in many parts of the world. In this article a great review of the disease is made, treating the different species of flies that cause the myiasis in the different species of hosts. Biologies of deer and flies are also studied, with special dedication to the chronobiology of the life cycle of the parasite. Prevalence and intensity of parasitization in many parts of Europe are recorded like expression of the importance of hypodermyiasis in deer. Finally, some remarks about treatment and control are included.

Sera from 100,400 cattle on 2850 farms in England, Scotland and Wales were tested for the presence of antibodies to Hypoderma species between the end of November 1995 and the end of February 1996. Twelve animals were resampled because the initial results were equivocal but only one of them was confirmed as seropositive. This animal was a bull imported from Belgium which had been treated with an approved warble fly treatment within 24 hours of arrival at its destination in Great Britain. No seropositive animals were confirmed within the native British cattle population. Statistical analysis of these data indicates that the probable maximum number of infested cattle herds in Great Britain is 112. To detect the disease by direct clinical observation would require more than 500 herds to be infested, indicating that the serological testing of this number of cattle and farms is more than four times as sensitive as clinical observation for the detection of hypodermosis.

A quasi-sequential sampling plan for observing cattle was undertaken in the framework of Hypoderma bovis epidemiological surveillance. This plan enabled us to test whether or not the prevalence of Hypoderma bovis is within a threshold p0 chosen for an eradication scheme or for qualifying a zone. The sampling cost was reduced but the estimation precision remained acceptable. The sensitivity of monthly controls with respect to the reference period (April, May, June, July) was studied from data observed over 6 consecutive years in Côtes d'Armor, France. The best ratio sensitivity/sampling cost was obtained with a unique counting plan in June where 48% (36 to 60%) of the herds found to be infested during the reference period were detected. The test procedure concerning the prevalence level was then adapted to take into account the sensitivity of the observation method. This is tantamount to reducing the threshold p0.

Hypodermosis is a parasitic disease of cattle caused by Hypoderma lineatum and H. bovis. It is an important health and welfare problem of infested cattle and a cause of considerable economic loss. In live animals, detection can be either by direct clinical examination of infested cattle and palpation of second and third stage larvae in the back or by the use of serological methods. This paper describes a competitive ELISA for the detection of antibodies to Hypoderma species in cattle sera. It has been validated using a small panel of 40 samples from clinically positive cattle and 200 samples from clinically negative (unexposed) cattle from a warble free area. Sensitivity and specificity calculated from this panel were 100% and 92% respectively at 2 SD from the mean or 92.5% and 98.5% at 3 SD from the mean. The use of serology and direct clinical examination of affected cattle, are discussed as methods for monitoring hypodermosis. The competitive ELISA should prove a useful adjunct to the standard sandwich ELISA, particularly in the resolution of samples which display non-specific binding properties.

Large scale preventive treatments against bovine hypodermosis have been performed in the Canton of Grisons and in different Jura areas. Either Metrifonate (Neguvon 10% spot-on, Bayer AG) or Ivermectin "microdoses" (i.e. 0.1 ml Ivomec ad. inj-MSD AGVET-per animal) have been applied. The treatment of dairy cows with Neguvon at the then recommended dose (24 ml/animal) showed a low efficacy of 80%, without any correlation to the date of treatment. An increase of the dose to 36 ml/animal revealed an efficacy of 93%, while a weight-dependent dose of 6 ml/100 kg body weight reduced the warble infestation by 97.3% without any drug-related side-effects. The few observed side-effects-salivation and mild meteorism--are likely to be due to the destruction of Hypoderma lineatum larvae in the gullet of treated cows. No case of abortion was reported. The Ivomec--"microdose" applied to young animals or dry cows showed an efficacy > 99.8%. The available drugs would thus allow a quick and efficacious control of bovine hypodermosis, provided they would be used systematically and at an appropriate dose in endemic areas.

The effect of parasiticide treatment on dynamics of antigen specific antibody responses to Hypoderma lineatum (De Villers) was investigated in naturally infested calves. Parasiticides were applied to cattle 1 month prior to, 1 week prior to, and coincident with the appearance of warbles in untreated calves from the same source herd. When cattle were treated approximately 1 month before warbles appeared in untreated control animals, antigen specific antibody levels increased for 25-34 days then declined to undetectable levels by approximately 75 days. Antigen specific antibody levels sharply declined in cattle treated 1 week prior to appearance of warbles in untreated controls. Treatment applied coincident with arrival of grubs on the back did not alter the antigen specific antibody profile, but reduced the relative magnitude of antigen specific antibodies present. Persistence of the antigen specific antibody following treatment will permit conduct of serological surveillance programmes.

A cattle herd from the experimental farm of INRA in Nouzilly has been treated for hypodermosis since October 1990. Additionally, a regional eradication scheme has been implemented in this area since autumn 1992. Bi-monthly warble counts were performed between March and July each year on an average of 200 animals. No warble was recorded in this herd from 1991 to 1994 with the exception of two dairy cows in 1993. In autumn 1994, therapeutic control measures were stopped. Serological surveys were performed in the autumn of each year from 1991 until 1995. Anti-Hypoderma antibodies were found in 25%, 27.2%, 4.3%, 3.2% and 0% of the animals respectively. An experimental low infestation was conducted in the summer of 1994. During the spring 1994, third instars of Hypoderma bovis were collected from naturally infested animals. From a total of 13 pupae, six adults (four males and two females) emerged and were released in the herd of Nouzilly on 24 June and 4 July. In October 1994 serological investigations revealed two animals seropositive for hypodermosis. This number increased to six in January 1995. The antibody kinetics of these six animals remained parallel throughout the next 6 months: the titres increased up to April and started to fall in May to return to negative values in August. Manual examinations of the animals at weekly intervals between April and July revealed the presence of four warbled animals with one, one, two and three warbles respectively. The two other seropositive animals remained warble free. One other animal showed antibody titre fluctuations between negative and low positive values, but was warble free in the spring. In October 1995 all the animals of the herd were seronegative. The interpretation and the value of a sensitive immunodiagnosis in a large eradication programme are discussed and compared with warble counts, especially in the case of a low level of infestation.

A serological survey was carried out to establish the prevalence of hypodermosis in Extremadura, a region of western Spain. Direct clinical methods and an enzyme linked immunosorbent assay (ELISA) were used to examine 1668 cattle between February 1992 and March 1993. An overall prevalence of 19.54 per cent was observed by the direct methods, and a prevalence of 42.3 per cent by the ELISA. The sensitivity and specificity of the ELISA for hypodermosis were assessed, and the fluctuation of antibody levels was studied throughout the year and correlated with the age of the host, the intensity of parasitism and the mean larval burden.

Hypodermosis and cephenemyiosis are largely widespread diseases in roe deer in the conditions of the Czech Republic. Both kinds of parasitosis cause great losses of game. The aim of this study was to test peroral administration of ivermectin with respect to the control of larval stages of hypodermosis (Hypoderma diana B.) in roe deer. Studies were performed on three localities within one three-year study and two 18-month studies. Ivermectin was administered for two days at a daily dose of 0.30 mg/kg body weight during winter game feeding. The shot deer were checked for the presence of larvae throughout the year. Prevalence and intensity of infection were determined. A total of 147 animals were checked in 1992-1994 (Tab.I); prevalence and intensity of infection were very low in comparison with the situation before treatment and with the control group (1994). Similar results were obtained in both shorter studies (Tab. II) performed on 27 animals in total. The results suggest (on the base of detail discussion) that the low values of prevalence and intensity of infection should be taken as partly distorted due to the methodical conditions of checks. The efficacy of ivermectin treatment was complemented by observation of several cases and their results employing direct checks of shot deer (Tab. III), including a six-year observation of a group of 6 to 10 individuals of tame deer treated year by. These results explicitly document the high efficacy of mass peroral ivermectin administration in the control of warble fly larvae. Ivermectin is the first drug suitable for the treatment of roe deer hypodermosis.

Seven individual trials were conducted in Wyoming to evaluate the therapeutic efficacy of doramectin administered subcutaneously at a dosage of 200 micrograms kg-1 against multiple, natural infestations of cattle grubs or cattle lice. Insect species present and the number of trials that included each species were: Hypoderma lineatum, 2; Hypoderma bovis. 1; Bovicola bovis, 5; Haematopinus eurysternus, 1; Linognathus vituli, 5; and Solenopotes capillatus, 3. Examinations for lice were performed prior to treatment and either weekly or bi-weekly thereafter for 28 days. Examinations for cattle warbles were performed either weekly or every 4 to 5 weeks from time of first appearance through last appearance in the backs of the cattle. No H. lineatum, H. bovis, H. eurysternus, L. vituli, or S. capillatus were found on doramectin-treated animals at any time following treatment. By 28 days following treatment, the number of B. bovis was reduced between 58 and 98%. Treatments applied later in the season, i.e. in March, were more efficacious against B. bovis than those applied in January or February.

From November 1992 to February 1993, 455 red deer (Cervus elaphus) were surveyed in order to estimate the prevalence of warble fly (Hypoderma actaeon) larvae under the skin of this ungulate species. Material came from Montes de Toledo, Sierra Morena, Sierra de Alcaraz, and Sierras de Cazorla, Segura y Las Villas Natural Park (central and southern Spain). We observed a prevalence of 92%, with a mean +/- SD intensity of 35.7 +/- 41.3 grubs per parasitized host; there was a maximum of 317 larvae per host. No significant differences in prevalence by host sex were found, although significant differences were observed in prevalences among different host age classes. The main location of feeding larvae in deer was in the back tissues.

The geographic distribution of bovine hypodermyiasis in the canton Vaud/Switzerland has been investigated in two ways: By direct examination of the animals by the livestock officers at the 1993 annual census and by ELISA on bulk milk sampled in January 1994. The efficacy of the two methods is compared and the distribution of hypodermyiasis presented on a map. The serological analyses have revealed a highly satisfactory degree of sensitivity and specificity (92.1% and 98.1%, resp.). The epidemiological interpretation however, is rather difficult, partly because quite often the animals are not infested on their farms but rather while being on alpine pastures. A monitoring of the herds with a view to an efficient control of hypodermyiasis could thus in a first instance be based on the indications provided by the livestock officers, whereas a serological monitoring in a second place would allow to detect the last and remaining foci of infestation.

An antigen was prepared from metabolic products which were produced by maintaining first instar larvae of Hypoderma lineatum in RPMI tissue culture medium for 48 h. Three major proteins were identified in the secretory products and were characterised in terms of their molecular weights and iso-electric points. The antigen compared favourably with a soluble extract of larvae when used in an enzyme-linked immunosorbent assay (ELISA) against a panel of control sera and 2000 bovine sera collected from farms in Andalucia, Spain.

The field efficacy of moxidectin 0.5% pour-on formulation was assessed in heifers naturally infested with Hypoderma bovis. After their first grazing season in an infested area 34 heifers were selected on the basis of results of an ELISA test performed in January 1992. Twenty-five animals were treated with moxidectin 0.5% pour-on at a dose of 0.5 mg kg-1 bodyweight and nine heifers were left untreated. No local or general side-effects associated with the treatment were noticed. In April, seven of the nine untreated heifers were affected by warble fly, and in May all were infested; none of the treated animals harboured warble fly at any time during the trial. All the extracted larvae were identified as Hypoderma bovis. On the basis of the warble counts, efficacy was 100%. The antibody kinetics, studied on blood samples collected on Days 0 (14 January), 6, 27, 48, 90, 119 and 150, showed that in the untreated animals, the antibody titres increased until May (Day 119) and then declined sharply, whereas in the treated animals there was a drop from Day 30 onwards. The mean ELISA titres of the control and treated groups became significantly different from Day 48 onwards (P < 0.05). In conclusion, moxidectin 0.5% pour-on formulation at a dose of 0.5 mg kg-1 bodyweight can effectively treat cattle naturally infested with Hypoderma bovis first instar larvae.

The efficacy of doramectin in the treatment of cattle harbouring naturally acquired infestations of first, second and third instar larvae of Hypoderma bovis was determined in two studies carried out in the Burgundy region of France. In the first study, cattle on six farms with a history of H. bovis infestations were treated during October 1989 with either doramectin at a dose of 200 micrograms kg-1 liveweight (186 animals) or with an equivalent volume of saline (157 animals). During the following March and April, all animals were examined for the presence of warbles. In the second study, cattle on four farms with warbles present in their backs were treated during March 1990, with either doramectin or saline (as before). The viability of larvae within each warble on all the animals was then assessed every 2 days for 14 days. In Study 1, no warbles were present in any of the doramectin-treated cattle at any time, whereas warbles were found in 135 saline-treated animals. In Study 2, all larvae in warbles on the backs of the doramectin-treated cattle were dead by Day 14 after treatment, whereas viable larvae were still present in warbles in the backs of all saline-treated cattle. No adverse reaction to doramectin treatment was observed in any animal at any time. It was concluded that doramectin is both safe and 100% efficacious in the treatment of first, second and third instar H. bovis infections of cattle.

Migrating first-instar larvae of Hypoderma lineatum are a frequent cause of focal inflammatory lesions in connective tissues of the mediastinum, parietal and visceral pleura, peritoneum, lungs, diaphragm, and other loci. The lesions are characterized grossly by foci of yellowish or greenish gelatinous edema and microscopically by infiltration of the edematous tissue by a dense array of eosinophils. Lesions were recognized during a period of several weeks in late spring; the timing was attributable to events in the life cycle of the fly. The larvae, which were small (approximately 1 x 4.5 mm), transparent, and unobtrusive, were recovered from lesions in 12 of 20 cattle in which careful parasitologic examination was made.

The aim of this work was to determine if Hypodermin C (HC), an enzyme secreted by Hypoderma spp. larvae during their migration, is able to depress the lymphocyte response to mitogens and antigens. HC, when added to the lymphocyte culture, was able to influence the response of naive-calf lymphocytes to phytohemagglutinin. Secondly, injections of HC to uninfested and previously-infested cattle did not modify the proliferative response of the lymphocytes of these animals to mitogens. Thirdly, injections of HC to infested cattle did not negatively influence the specific humoral and cellular responses.

Cattle grubs (Hypoderma lineatum and H. bovis) are obligate parasites of cattle for most of their one year life cycle. Previously exposed animals become resistant to productive reinfestation, presumably as a result of immune system involvement, suggesting potential control by vaccination. Research progress towards development and utilization of a recombinant subunit vaccine for hypodermosis is described.

The British warble fly eradication programme has resulted in the numbers of infested cattle falling from an estimated four million in 1978 to zero in 1991. In 1982, when about 705 herds were infested the disease was made notifiable, and serological surveillance was begun in 1988. In spring 1991, 227,000 blood samples were tested by using the ELISA technique and no warbled animals were found. In addition no clinical cases were reported during 1991.

Moxidectin, a systemic insecticide, was evaluated for its efficacy against the migrating first instars of the common cattle grub, Hypoderma lineatum, and against nematode egg production in beef cattle. It was observed that all three levels (0.1, 0.2 and 0.4 mg moxidectin kg-1) were 100% effective against cattle grubs when administered as a s.c. injection. The same levels of treatment were very effective (90-100%) in reducing trichostrongyle nematode egg production. However, there was a slight indication that at least one species, Cooperia oncophora, was not completely eliminated, as it was observed that small numbers of eggs began to appear after 2 weeks post-treatment when there had been no opportunity for reinfection.

The anti-parasitic effect of the orally administered paste formulation of ivermectin (Ivomec) in reindeer was evaluated by means of a trial designed to compare the efficacies of orally and s.c. administered ivermectin at the same dosage (0.2 mg kg-1 body weight) in naturally infected adult reindeer (n = 92). Both formulations were 100% effective against larvae of the warble fly, Oedemagena tarandi, while oral treatment was less efficacious than s.c. injection against parasitic nematodes. Both formulations, but particularly the injectable ivermectin treatment, increased the weight gain of pregnant females compared to that of those not treated.

The absence of any inflammatory reaction around the first instar larvae (L1) of Hypoderma sp. in previously uninfested cattle suggested that these larvae may escape the non-specific defence system of the host. Immunosuppression had been noted during an experimental infestation. The aim of this work was to determine more precisely the potential role of hypodermin A (HA), an enzyme secreted by the larvae, in this immunosuppression. HA was found to have no effect on unstimulated lymphocytes from naive cattle but could influence the response of these cells to mitogens. In calves, injection of HA was accompanied by a decrease in the lymphocyte proliferative response to mitogens. This immunodepression lasted only for the duration of enzyme injections. In cattle, when HA is added, the antigen-dependent proliferative response increased significantly after 1 week of injection and disappeared 2 weeks after the end of the injection period. Finally, the rate of production of anti-HA antibodies increased at the same rate for calves and cows, and achieved a similar level. These results suggest that HA significantly modified the lymphoproliferative response for naive cattle and, to a lesser extent, immune cattle during the time of administration only.

In this study, we have determined whether immunization with hypodermin A (HA), associated with various adjuvants, could provide protective immunity for calves when challenged with a natural hypoderma infestation. Groups of naive calves were vaccinated with HA antigen alone or with adjuvants [Freund's incomplete adjuvant (FIA) or alumina phosphate (AP)]. Subcutaneous injection with HA antigen with or without adjuvant did not significantly protect calves against a natural hypodermosis infestation. The humoral response during the infestation period was evaluated by ELISA. A significant earlier and greater response was induced in groups vaccinated with HA alone and HA combined with FIA. These results indicate that HA, in this vaccination protocol, induces a very incomplete protection in calves exposed to a natural infestation.

Cattle infested with the common cattle grub, Hypoderma lineatum (Villers) develop specific humoral antibodies and a cellular immune reaction, defined by delayed-type hypersensitivity, to purified H. lineatum proteins. This investigation was designed to study the antigen-specific bovine lymphocyte response to hypodermin A (HyA), a serine protease of larval first-instar H. lineatum. Calves were vaccinated with either native or denatured HyA, and challenge-infested with H. lineatum. The kinetic development of a cellular immune response to HyA was monitored during vaccination and infestation. The HyA-specific responses were highly variable and weak during vaccination and infestation. Although HyA-specific lymphocyte blastogenic responses were observed, no correlation was noted between the magnitude of antigen-specific, peripheral lymphocyte proliferation and larval mortality. In striking contrast to responses observed during infestation, intense HyA-specific lymphocyte responses were observed with 3 calves 6 months after recovery from infestation. In addition, those responses were further heightened by a 250 micrograms booster injection of pure HyA.

An enzyme-linked immunosorbent assay (ELISA) was used on pooled serum and milk samples to determine whether hypodermosis could be detected where a larger sero-epidemiological survey was required. This study was undertaken to assess the potential of this assay for testing sera on milk samples, pooled from 10 cows, and determining the period of the year when detection was optimal. The sensitivity of the assay was determined by increasingly diluting a positive serum with pooled negative sera, from 1:10 to 1:100. The diagnostic lower limit of the assay requires at least two serological reactors within a herd of 100. The kinetic development and depletion of anti-Hypoderma antibody of individual and pooled sera or milk from 30 cows was evaluated from November to July. Anti-Hypoderma antibody levels of two groups of 8 calves, one control and one teated with ivermectin (Ivomec), were tested from October to June. These preliminary results indicate that an ELISA assay on serum or milk samples pooled from 10 cows can be used between February and April to evaluate the prevalence of hypodermosis within cattle herds in France, demonstrating the feasibility of using pooled serum already collected for bovine leucosis testing.