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Background: Control of buffalo flies (Haematobia irritans exigua, BFs) relies mainly on chemical methods; however, resistance to insecticides is widespread in BF populations. Breeding for resistance to BFs represents a possible alternative, but direct phenotyping of animals is laborious and often inaccurate. The availability of reliable diagnostic biomarker(s) to identify low BF carrier cattle would facilitate rapid and accurate selection for genetic improvement. However, limited information is available regarding differences amongst cattle in host responses to BF infestation. Methods: This study investigated the variation in Brangus cattle serum proteomic profiles before (naïve) and after peak BF exposure, in low (LF) and high BF burden (HF) cattle. Cattle were phenotyped for susceptibility based on BF counts on multiple dates using visual and photographic techniques. The relative abundance of serum proteins in cattle before and after exposure to BFs was analysed using sequential window acquisition of all theoretical fragment ion mass spectrometry (SWATH-MS). Results: Exposure to BFs elicited similar responses in HF and LF cattle, with 79 and 70 proteins, respectively, showing significantly different abundances post exposure as compared to their relevant naïve groups. The comparison of serum samples from naïve HF and LF cattle identified 44 significantly differentially abundant (DA) proteins, while 37 significantly DA proteins were identified from the comparison between HF and LF cattle post-exposure to BFs. Proteins with higher abundance in naïve LF cattle were enriched in blood coagulation mechanisms that were sustained after exposure to BFs. Strong immune response mechanisms were also identified in naïve LF cattle, whereas these responses developed in HF cattle only after exposure to BF. High BF cattle also showed active anticoagulation mechanisms in response to BF exposure, including downregulation of coagulation factor IX and upregulation of antithrombin-III, which might facilitate BF feeding. Conclusion: Underlying differences in the abundance of proteins related to blood coagulation and immune response pathways could potentially provide indirect indicators of susceptibility to BF infestation and biomarkers for selecting more BF-resistant cattle. [ABSTRACT FROM AUTHOR]

This article discusses the first recorded instance of a phoretic association between Pediculaster sp. mites and Musca crassirostris flies in India. The mites attach to the flies for transportation and were found on muscid flies on a bird corpse in Himachal Pradesh, India. The study explores the phoretic relationships between mites and flies in India, including different species of mites and flies. It also suggests the need for further research on mite species and their habitat preferences, as well as their potential use in forensic analysis. References for further reading are provided. [Extracted from the article]

Abstract This study aimed to develop a pyriproxyfen-based Rumino-Reticulum Device (RRD) consisting of films of poly(vinyl)alcohol (PVA) and sodium carboxymethylcellulose (NaCMC) to control the horn fly in cattle, one of the major pests of livestock. Films were obtained by the solvent casting method by PVA/NaCMC crosslinking and presented satisfactory homogeneity, drug content (104.8%) and pH (6.5), besides great absorptive capacity with swelling degree of 331.40% after 1 hour and diffusion-controlled release kinetics (Higuchi). FTIR and SEM analyzes clarify the characteristic bands of PVA, NaCMC and pyriproxyfen. The XRD and thermal analysis shows an increase in crystallinity due to pyriproxyfen (Xc:36.59%) and the active delivery alters the chain packing (Tg:74ºC). The pyriproxyfen-based RRD developed, in addition to fulfilling the characteristics of prolonged release, allows it to be rolled up (compressed form) facilitating swallowing and subsequent conversion to an expanded form that is retained in the rumen throughout the treatment period.

Background: Ticks and tick-borne diseases pose significant challenges to cattle production, thus the species identification of ticks and knowledge on their presence, abundance, and dispersal are necessary for the development of effective control measures. The standard method of inspection for the presence of ticks is the visual and physical examination of restrained animals, but the limitations of human sight and touch can allow larval, nymphal, and unfed adult ticks to remain undetected due to their small size and site of attachment. However, Raman spectroscopy, an analytical tool widely used in agriculture and other sectors, shows promise for the identification of tick species in infested cattle. Raman spectroscopy is a non-invasive and efficient method that employs the interaction between molecules and light for the identification of the molecular constituents of specimens. Methods: Raman spectroscopy was employed to analyze the structure and composition of tick feces deposited on host skin and hair during blood-feeding. Feces of 12 species from a total of five genera and one subgenus of ixodid ticks were examined. Spectral data were subjected to partial least squares discriminant analysis, a machine-learning model. We also used Raman spectroscopy and the same analytical procedures to compare and evaluate feces of the horn fly Haematobia irritans after it fed on cattle. Results: Five genera and one sub-genus at overall true prediction rates ranging from 92.3 to 100% were identified from the Raman spectroscopy data of the tick feces. At the species level, Dermacentor albipictus, Dermacentor andersoni and Dermacentor variabilis at overall true prediction rates of 100, 99.3 and 100%, respectively, were identified. There were distinct differences between horn fly and tick feces with respect to blood and guanine vibrational frequencies. The overall true prediction rate for the separation of tick and horn fly feces was 98%. Conclusions: Our findings highlight the utility of Raman spectroscopy for the reliable identification of tick species from their feces, and its potential application for the identification of ticks from infested cattle in the field. [ABSTRACT FROM AUTHOR]

Simple Summary: Fly control has always been a hot topic for dairy farmers, because there are not a lot of viable options to alleviate fly pressure. Dairy cows on pasture are commonly disturbed by many fly species, and dairy cow behavior may be affected by different fly species. In an experimental research trial, there was a strong relationship between the number of flies and the number of defensive behaviors of cows of different lactations. Milk yield was not affected by low fly numbers, indicating that greater than 40 horn flies per cow are needed to potentially lower the milk production of grazing dairy cows. To improve profitability, farmers need to properly identify key pasture flies, understand their biology and habitat, monitor their populations, and then reduce the fly population through mechanical or biological management techniques. Thirty-four crossbred dairy cows were observed on pasture six times per week from June to August 2014 at the University of Minnesota West Central Research and Outreach Center grazing dairy in Morris, MN, for defensive behaviors in response to three species of muscid flies. Counts of stable flies (Stomoxys calcitrans (L.)), horn flies (Haematobia irritans (L.)), and face flies (Musca autumnalis DeGeer) were recorded before and after pasture observation. Individual cows were monitored for 5 min intervals to observe the frequencies of five different defensive behaviors: front and back leg stomps, head tosses, skin twitches, and tail swishes. Fly numbers averaged 5 stable flies per leg, 37 horn flies per side, and 1 face fly per face during the study. The fly counts and behavior frequencies increased with ambient temperature. The results showed a very strong relationship between the numbers of flies and numbers of defensive behaviors, though correlations between specific flies and behaviors were low. Younger cows had fewer stable flies and horn flies than older cows. The thresholds of flies to lower production for pastured organic dairy cows may be greater than 5 for stable flies, 37 for horn flies, and 1 for face flies. [ABSTRACT FROM AUTHOR]

The genetic basis of horn fly abundance remains largely unknown and only few heritability estimates are available based on small scale studies. In this study, one subjective and two image-based fly abundance phenotypes were analyzed. Each animal was assessed subjectively for fly abundance by at least one trained agent (SUB). Additionally, several digital images were taken and the best image for each animal was used to assess fly abundance. A box that runs roughly from the withers to the hook and from the chest floor to the fore of the udder was established and all horn flies (PA) and sampling-based estimated number of flies (PR) within the box were calculated. Horn fly counts (SUB, PA, and PR) were discretized into 4 classes based on the quartiles of their respective distributions. Heritability estimates ranged between 0.10 and 0.15 and between 0.14 and 0.16 for the continuous and discrete cases, respectively. The genetic correlation was 0.66 between PA and PR and decreased significantly between the image-based (PA and PR) and the subjective (SUB) assessments for the continuous case. For the discrete case, the genetic correlations between the three traits were very similar, indicating a high concordance between traits.

The ectoparasites Rhipicephalus microplus, Dermatobia hominis, and Haematobia hominis are a major obstacle to livestock productivity, a factor that is aggravated above all by the acquisition of drug resistance to many active ingredients. With the aim of minimizing this phenomenon, four clinical studies were conducted with a new formulation (benzoylphenylurea + organophosphate). In order to assess the anti-ixodid activity, trials were carried out on naturally and experimentally infested cattle. In the former, the carrapaticidal efficacy index was over 90% from the 7º to the 28º DPT (Days post-treatment). In the "Stall test" (artificial infestations), the maximum efficacy rate (100%) was achieved from the 20º to the 47º DPT. The mosquicidal activity of the new formulation against Haematobia irritans (natural infestation) remained above 90% from the 1º to the 14º DPT. It was more than 90% effective against Dermatobia hominis larvae from the 7º to the 21º DPT. Based on the results obtained in the four studies carried out, the unprecedented formulation can be recommended, in the dose and route prescribed, for the treatment and control of external parasites in cattle. [ABSTRACT FROM AUTHOR]

Background: This study describes the effectiveness of a novel active pharmaceutical ingredient, fluralaner (isoxazoline class), against important ectoparasites infesting cattle in Brazil. Methods: A total of 13 studies involving a 5% fluralaner-based pour-on formulation (Exzolt 5%; further referred to as Exzolt) were conducted. Specifically, the effectiveness of this formulation was studied against Rhipicephalus microplus (6 studies), Cochliomyia hominivorax larvae (4 studies), Dermatobia hominis larvae (1 study) and Haematobia irritans flies (2 studies). Results: The therapeutic efficacy of Exzolt was found to exceed 98% at 4 days post treatment (DPT), while persistent efficacy (> 90% efficacy) against repeated infestations of R. microplus was observed for up to 79 DPT. In field studies, ≥ 98% therapeutic efficacy was demonstrated at all study sites by 7 DPT, and a persistent efficacy (> 90% efficacy) was observed for 42, 49 or 56 DPT. Exzolt prevented C. hominivorax eggs from developing to the larval stage, thus mitigating the development of myiasis in cattle naturally and artificially infested with this screworm. The efficacy of Exzolt against D. hominis larvae was 98% at 3 DPT, while persistent efficacy (> 90% effectiveness) was found to last for up to 70 DPT. Against H. irritans, Exzolt showed therapeutic efficacy (≥ 90%) within the first day of treatment at both study sites, while persistent efficacy (≥ 90%) was observed for 7 DPT at one site and for 21 DPT at the other site. Conclusions: Overall, the results from these studies confirm that Exzolt is therapeutically efficacious against the most important ectoparasites infesting cattle in Brazil. The novel active pharmaceutical ingredient, fluralaner, provides a new treatment option for farmers to control cattle ectoparasites, especially where there is resistance to other chemical classes. In addition, an effective control of ectoparasites will improve overall cattle health and well-being as well as production. [ABSTRACT FROM AUTHOR]

Horn flies are the most common summer pests of cattle, leading to substantial economic losses due to impaired production and decreased animal welfare. Genetic and non-genetic factors have been reported to influence cattle susceptibility to horn flies. However, the wide range of heritability estimates, and few identified genomic regions associated with cattle resistance to horn fly may be due to subjective assessment in collecting the fly load phenotype and the small size of the population assessed. Here, beef calves from the UF purebred Brahman (BRA) and Multibreed Angus-Brahman (MAB) populations were video recorded at weaning using a GoPro camera mounted on the top of the chute. Fly infestation was determined as the average fly count obtained from five longitudinal images of each animal using ImageJ software. A total of 748 crossbred and 415 purebred calves born from 2021 to 2023 were evaluated during summer (August or September). Analysis of variance (ANOVA) was performed within herd by fitting linear models that included collection date, age, skin color, coat color, and pre-weaning average daily gain (ADG) as fixed effects, and residual as a random effect. For MAB calves, breed groups (BG) determined based on the percentage of Brahman breed, with BG1 ranging from 0 to 19%, BG2 from 20 to 39%, BG3 from 40 to 59%, BG4 from 60 to 79%, BG5 from 80 to 100%, were also fit in the model. Fly count was transformed to a natural log value (log[count +1]) ensuring normally distribute residuals. As expected, darker colors were significantly more attractive to horn flies, while animals with greaterr percentage of Brahman were less susceptible than animals with greater percentage of Angus breed. Considerable variability in fly load was observed within purebred Brahmans, indicating that additional genetic factors, other than breed, influence cattle resistance to flies. Positive estimates were observed between horn fly load and average daily gain in both herds, which can be due to the fly load below the previously reported economic injury level of 200 flies (BRA: 28.78 ± 38.20, MAB: 19.31 ± 26.72). Variance components were estimated within herds by fitting the same aforementioned effects and a genomic-based relationship matrix (G) constructed with genotypes from the GeneSeek Genomic Profiler F250 SNP chip. The moderate heritability estimate demonstrates the feasibility of selecting cattle resistant to horn flies. Overall, our findings have the potential to contribute to reducing losses and costs in beef cattle operations, while reducing the impact on the environment of overuse of insecticides. [ABSTRACT FROM AUTHOR]

Simple Summary: Skin lesions in cattle associated with feeding by Haematobia fly species are a significant health issue in northern Australian cattle. These lesions have most commonly been attributed to the effects of Stephanofilaria nematodes vectored by the Haematobia spp. flies. However, the exact etiology of these lesions and reasons for the variation between the cattle in the severity of lesions was unclear. This study investigated the cutaneous responses to fly and nematode antigens in lesion-resistant and susceptible cattle, which indicated that differences in the hypersensitivity response to buffalo fly (Haematobia irritans exigua) antigens is a key factor underlying the variation amongst the cattle in susceptibility-to-lesion development. There was no association found between the intensity of fly infestation and lesion susceptibility. The findings from this study suggest that further characterization of the skin response could lead to the identification of the biomarkers for selecting cattle with an increased resistance to buffalo fly lesion development. This study investigated the role of cattle immune responses in the pathogenesis of buffalo fly (Haematobia irritans exigua) (BF) lesions. Brangus steers phenotyped for lesion development were divided into three groups: high lesion susceptibility (HL), low lesion susceptibility (LL) and no lesions (NL), based on lesion severity scores. Each steer was injected intradermally with different concentrations of BF, Onchocerca gibsoni (Og), and Musca domestica (Md) antigens. At 1 h post-injection, wheal areas at BF injection sites were found to be significantly larger in HL than NL cattle, but there were no significant differences (p < 0.05) found between either the HL or NL cattle and LL cattle. At 24, 48, and 72 h post-injection, the skinfold thickness response to both BF and Md antigens was significantly greater in the HL group than the NL group. However, skin thickness was significantly greater for the BF antigens than the Md antigens (p < 0.05). There were no significant differences found between the LL and NL animals in response to the BF antigens at any time, and no significant differences were determined between any of the lesion groups in response to the Og antigens. Histological examination of skin sections taken from the BF antigen injection sites in HL cattle at 72 h post-injection revealed necrosis of the epidermis and superficial dermis, along with severe eosinophilic inflammation. This study suggests that differences in the hypersensitivity to BF antigens underlie differences amongst the cattle in their susceptibility to the development of BF lesions, and breeding for immune-related biomarkers may assist in selecting more BF lesion-resistant cattle. [ABSTRACT FROM AUTHOR]

The horn fly Haematobia irritans is a cosmopolitan hematophagous ectoparasite of great importance in livestock. In Mexico, H. irritans is distributed across the country, and is found during the whole year. The fluctuation of H. irritans population is related with climate conditions. Despite its wide distribution, the effects on animal health, and its negative impact on meat and milk production, little data exists on its infestation and epidemiology is limited. This paper is a review on the current situation of H. irritans in cattle in Mexico, its economic impact, control methods, perspectives, and research opportunities. [ABSTRACT FROM AUTHOR]

The beef industry endures major economic losses from a complex of flies that feed on bovine blood and mucus. For cattle on pasture, the most important of these pests are horn flies (Haematobia irritans [L.] [Diptera: Muscidae]) and face flies (Musca autumnalis [Diptera: Muscidae] De Geer). Pasture dragging to spread manure pats has been promoted as a management tactic for these species because their larvae inhabit bovine manure pats, but the efficacy of this practice has not been empirically validated. Spreading pats might promote fly mortality through desiccation or overheating, but these processes are weather‐dependent and warrant testing in disparate climates. We evaluated pasture dragging effects while monitoring for weather interactions throughout nine experiment rounds in summers of 2018 and 2020 in Pennsylvania, USA. The manure spreading treatments increased pat surface area up to 300% but failed to significantly reduce emergence of horn flies and face flies as compared to controls. In contrast, precipitation and temperature were significant predictors in fly emergence models. Surprisingly, face fly emergence was significantly elevated in dragged pats twice in 2020. These data call for a reevaluation of pasture dragging as a management technique for horn flies and face flies across a range of climates. [ABSTRACT FROM AUTHOR]

Haematobia irritans irritans (Linnaeus, 1758: Diptera: Muscidae), the horn fly, is an external parasite of penned and pastured livestock that causes a major economic impact on cattle production worldwide. Pesticides such as synthetic pyrethroids and organophosphates are routinely used to control horn flies; however, resistance to these chemicals has become a concern in several countries. To further elucidate the molecular mechanisms of resistance in horn fly populations, we sequenced the transcriptomes of ten populations of horn flies from the southern US possessing varying degrees of pesticide resistance levels to pyrethroids, organophosphates, and endosulfans. We employed an Illumina paired end HiSeq approach, followed by de novo assembly of the transcriptomes using CLC Genomics Workbench 8.0.1 De Novo Assembler using multiple kmers, and annotation using Blast2GO PRO version 5.2.5. The Gene Ontology biological process term Response to Insecticide was found in all the populations, but at an increased frequency in the populations with higher levels of insecticide resistance. The raw sequence reads are archived in the Sequence Read Archive (SRA) and assembled population transcriptomes in the Transcriptome Shotgun Assembly (TSA) at the National Center for Biotechnology Information (NCBI).

Thirty-four crossbred dairy cows were observed on pasture six times per week from June to August 2014 at the University of Minnesota West Central Research and Outreach Center grazing dairy in Morris, MN, for defensive behaviors in response to three species of muscid flies. Counts of stable flies (Stomoxys calcitrans (L.)), horn flies (Haematobia irritans (L.)), and face flies (Musca autumnalis DeGeer) were recorded before and after pasture observation. Individual cows were monitored for 5 min intervals to observe the frequencies of five different defensive behaviors: front and back leg stomps, head tosses, skin twitches, and tail swishes. Fly numbers averaged 5 stable flies per leg, 37 horn flies per side, and 1 face fly per face during the study. The fly counts and behavior frequencies increased with ambient temperature. The results showed a very strong relationship between the numbers of flies and numbers of defensive behaviors, though correlations between specific flies and behaviors were low. Younger cows had fewer stable flies and horn flies than older cows. The thresholds of flies to lower production for pastured organic dairy cows may be greater than 5 for stable flies, 37 for horn flies, and 1 for face flies.

Horn flies, Haematobia irritans irritans (L.); house flies, MuscadomesticaL.; and stable flies, Stomoxys calcitrans (L.), are problematic to livestock production and, in the instance of M. domestica, to human health. p-Anisaldehyde was assessed for its bioactivity against the eggs of the three muscid species. The compound, which is found in many edible plants, was lethal to the eggs of H. irritans and S. calcitrans at a relatively low (=0.01%) concentration when eggs were exposed to the treated substrate and when exposed to fumigation (=0.0001%). Although M. domestica eggs were less vulnerable to the treated substrate than the other two muscids, egg hatch was delayed, and fumigation with a low p-anisaldehyde concentration (0.001%) induced substantial egg mortality. In many instances, larval development inside the eggs did not occur, while other larvae developed, swelled, and although they broke the egg casing, they failed to emerge. The possible utility of p-anisaldehyde against the eggs of the three muscid species as a possible integrated pest management tactic is discussed. [ABSTRACT FROM AUTHOR]

For gregarious parasitoid species, the number of adult parasitoid progeny produced per parasitized pupa was also calculated. After parasitoid emergence, data collected for each cup included numbers of: emerged flies, emerged male and female parasitoid progeny, pupae with parasitoid exit holes and pupae with no exit holes (not developed, uneclosed pupae). There were significant differences in tibia lengths of parasitoids reared from both solitary and gregarious parasitoid species, with the larger I M. domestica i hosts generally producing parasitoids with longer tibia (Table 3). In central and south America, parasitism of I E. euxesta i and I E. mazorca i Steyskal has been reported with a I Spalangia i spp. (pupal parasitoid), I Dettmeria euxestae i Borgmeirer (Eucoilidae) (larval parasitoid) and I Euxestophaga argentinensis i Gallardo (Figitidae) (larval parasitoids) [[58]]. [Extracted from the article]

Simple Summary: Horn flies are a major nuisance to livestock, resulting in reduced productivity and substantial economic losses. Current fly control methods have temporary efficacy, adversely impact the environment, and increase fly resistance to insecticides. Using the animal's innate resistance and tolerance to horn flies through genetic selection could be an attractive alternative. Unfortunately, measuring horn fly abundance, especially under pasture conditions, is economically and logistically challenging, and alternative approaches are needed. In this study, thrombin, a major player in blood coagulation, was investigated as a potential proxy trait to assess on-animal fly counts. Our genetic analyses showed that the blood thrombin level is negatively correlated with fly count, is moderately heritable, and can be used to select against fly abundance in beef cattle. Horn flies are a major nuisance to cattle and induce significant economic losses. Fly abundance varies within and across breeds and genetic analyses have shown sufficient genetic variation to permit selection. A major bottleneck for selecting against horn fly abundance is the complexity of measuring fly attraction phenotypes. Easy-to-measure proxy phenotypes could be an attractive option to indirectly estimate fly abundance. In the current study, thrombin was investigated as a potential proxy to assess fly abundance. Fly counts and blood samples were collected on 355 cows. Pearson correlation between subjective fly count and thrombin was −0.13, indicating a decrease in fly abundance with the increase in thrombin concentration. When thrombin was discretized into three classes, there was a 22% difference in fly count between the top and bottom classes. Heritability estimates of thrombin were 0.38 and 0.39 using linear and threshold models, respectively. The correlation between estimated thrombin breeding values and fly count was around −0.18. There was a noticeably lower density of high fly counts among animals with high breeding values for thrombin. These results indicate that thrombin could be used in combination with other biological factors to estimate fly abundance and as a proxy for selection against fly abundance. [ABSTRACT FROM AUTHOR]

The aim of this study was to identify factors that play a key role in the epidemiology of bovine anaplasmosis by adapting a model primarily developed for cattle babesiosis. A cross-sectional observational study was conducted to study the proportion of calf herds in endemic stability/instability for A. marginale in a semi-arid area of Argentina. The A. marginale inoculation rate (h) was calculated from age-specific seroprevalence using double-antigen sandwich ELISA in 58 herds of 4.5–8.5-month–old calves. Herds were considered to be in endemic instability (EI) at h < 0.005 and, therefore, at risk of anaplasmosis outbreaks. A generalized linear model was performed to explore husbandry practices associated with differences in A. marginale transmission. Additionally, spatial clustering of herds with the same immunological status was analyzed using spatial scan statistics (SatScan, Bernoulli model). Spearman's correlation was used to explore a possible association between A. marginale h and Babesia bovis and B. bigemina h (data obtained in previous works). Almost half (43 %) of the herds were in the EI zone for A. marginale. Calves raised under forage combinations had a greater risk of being in EI (OR = 5.41, CI95 %OR = 1.43–20.41) than those reared exclusively on permanent pastures, where cattle density is higher (P = 0.01). Moreover, calves from herds treated only with pyrethroids to control ticks had more chances of being in EI (OR = 4.16, CI95 %OR = 1.12–15.38) than calves from herds receiving different acaricide combinations (P = 0.03). Calves from herds subjected to more than two treatments against Haematobia irritans had higher odds for EI (OR = 5.69, CI95 %OR = 1.24–26.11) than those from herds using fewer than two treatments (P = 0.02). The spatial analysis revealed no spatial clustering of the immune status of the herds (P = 0.67 and P = 0.74 for low and high incidence rates, respectively). A significant variation between farms was observed in A. marginale h (CV = 90.38 %). The correlation analysis revealed a strong epidemiological link of A. marginale h with B. bovis h (Rho=0.794, P <0.001) and B. bigemina h (Rho=0.839, P <0.001). Given that R. microplus is the only vector of B. bovis and B. bigemina in the region, the results of this work strongly suggest an active and significant role of R. microplus in the transmission of A. marginale. • Endemic instability for Anaplasma marginale is frequent in northwestern Argentina. • Farm-level risk factors had strong influence on the immunological status. • Findings indicate R. microplus plays a crucial role in A. marginale transmission. [ABSTRACT FROM AUTHOR]

Horn flies are one of the most prevalent ectoparasites on pasture raised cattle. Studies have shown reasonable evidence of a genetic basis for horn fly attraction in beef cattle. Current methods for assessing fly abundance-related phenotypes (e.g., subjective assessment and image-based counts) suffer from limited accuracy and logistic difficulties. Previous attempts to assess horn fly abundance using image-based methods were hindered by several factors including weather conditions, distance and angle between the image taker and the animal, and lighting during image acquisition. The aim of this study was to address these limitations through the development of practical guidance to optimize image acquisition and to develop an adaptive image analysis algorithm to enhance the accuracy of image-based assessment of fly abundance. Images of beef cattle on pasture over multiple horn fly seasons (late spring to early fall) were collected. For each animal, the best image (where the entire side of the animal was in view) was selected and cropped from the withers to the hooks and from the chest floor to the udder. For every image (n = 314), all the flies were manually counted using the ImageJ software. Several image enhancement and analysis techniques including adaptive thresholding, pixel region connection, and pixel classification were used. The images were then clustered into three quality classes based on quality metrics computed using several algorithms from the image processing toolbox in MATLAB (BRISQUE, NIQE, and PIQE). BRISQUE and NIQE use distortions of natural scene statistics to compute quality scores. PIQE uses image features and models of human perception to compute quality scores. Pearson correlation, mean squared error (MSE), and the coefficient of determination (R² ) were used to evaluate the concordance between the manual (ground truth) and the image predicted counts. Across the different scenarios, the Pearson correlation and R2 ranged between 0.21 to 0.67 and 0.04 and 0.45, respectively (Table 1). When the images were first clustered in quality classes, all the assessment metrics showed a substantial increase (Table 2). In fact, the Pearson correlation ranged between 0.47 to 0.80 using the NIQE. When the images were classified as low or medium quality by BRISQUE, the correlation was greater (0.74 to 0.79) compared with NIQE (0.47 to 0.70) and PIQE (0.69 to 0.74). Similar patterns were observed for the other assessment criteria (MSE and R2 ). These results seem to indicate that NIQE, BRISQUE, or a combination of the two algorithms could be used to assess image quality and determine the appropriate combination of image parameters to maximize the predictive ability. The NIQE method could be used as a filter to detect low quality images that are unsuitable for counting and then BRISQUE could be used on the remaining images. [ABSTRACT FROM AUTHOR]

The objective of the present study was to characterize a herd of 72 ½ Angus × ½ Nellore heifers, identify the resistant, resilient and susceptible animals to parasites, relate the overall DNA methylation of these animals with the degree of parasitism, evaluated by the egg count per gram of feces (EPG), Haematobia irritans count (horn fly) and Rhipicephalus microplus count (bovine tick). The experiment was carried out in a completely randomized design, containing 72 treatments, with each animal considered a treatment, and 11 repetitions, with each collection within a year considered a repetition. The data obtained from the counts of the evaluated parasites were subjected to statistical analysis using the SISVAR program, to classify heifers according to the degree of parasitism in low (resistant), intermediary (resilient) and high (susceptible) parasite load for infection by nematodes, infestation by ticks and flies. Addition the animals in these three groups, by hierarchical grouping using the GENES program, heifers were classified as to the degree of parasitism by the three parasites along with the DNA methylation content of the animals in each group. A negative relationship was observed between resistance and methylated DNA content in both classifications, with the resistant, resilient, and susceptible animals showing the highest, intermediate, and lowest methylated DNA quantifications, respectively. Thus, the methodologies used herein enabled the classification of 72 heifers according to the degree of collective infection by gastrointestinal nematodes and infestation by ticks and horn flies, thereby establishing a link between the degree of parasitic resistance in cattle and the global methylated DNA quantification. [ABSTRACT FROM AUTHOR]

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Objective: To evaluate the infestation with flies in grazing cattle, and its relationship with some behaviors (tail butting, head butting, kicking and rubbing) that alter animal welfare, through direct observation and use of photographs. Design/Methodology/Approach: At two times (7:00 and 14:00 h) the variables were measured on thirty naturally infested cows and randomly distributed in two treatments: TS: control without deworming and TD: chemically dewormed. Results: The fly infestation were higher (p=0.001) in TS cows (483.7 flies/animal), they also, expressed with greater intensity (p=0.001) and frequency of upset behaviors: tail-tapping (10.84 movements min-1), headbutting (1.66), kicking (0.51) and rubbing (0.33) in order to drive away the annoying contact and aggression of the ectoparasite. Limitations: More in deep research is needed in order to assess the physiological disorders that this parasite could cause by altering well-being of grazing cattle in the tropics. Findings/Conclusions: It is concluded that the greater the fly infestation, the movements that alter the welfare of the animals' increase; however, more research is required to know the physiological welfare consequences that the infestation of this parasite implies. [ABSTRACT FROM AUTHOR]

Tennessee and Texas cow-calf producers were surveyed to assess their 2016 expenses for horn fly control methods. Cattle producers who were members of the Texas and Southwestern Cattle Raisers Association and Tennessee cattle producers who have participated in the Tennessee Agricultural Enhancement Program participated in the survey. Average horn fly management costs in Tennessee and Texas were $9.50/head and $12.40/head, respectively. An ordinary least squares regression and quantile regression were estimated to examine how horn fly costs are influenced by producer and farm demographics, seasonality of horn flies, producer horn fly perceptions, and management practices. When controlling for these variables, Tennessee and Texas cattle producers did not spend significantly different amounts on horn fly control methods. Horn fly costs were associated with producer and farm demographics, producer perceptions of horn flies, and management practices. For example, results indicate that horn fly management costs vary depending on a producer's level of education and income. Having Angus cattle and larger herd sizes were associated with lower costs per head spent on horn fly management. Producers who did not consider horn flies to be a problem until greater quantities of flies were present on the animal spent 15% less per head on managing horn flies. In terms of horn fly control methods, feedthrough insecticides increased horn fly costs the most, followed by using ear tags. This is the first known research to estimate horn fly management costs among cattle producers. [ABSTRACT FROM AUTHOR]

Seven mature Angus × Hereford crossbreed cows (544 ± 23.2 kg of body weight) fitted with duodenal and ruminal cannulas were used in a crossover design to evaluate the effects of horn fly (Haematobia irritans) (L.) infestation on horn fly-induced defensive behaviors, feed and water intake, as well as digestion characteristics of beef cows. Cows were randomly assigned to one of two treatment groups: 1) a horn fly infested (1,000 flies per cow) or 2) a noninfested control group. All cows were housed in individual screened pens. Fly counts and infestations were performed daily to maintain consistent populations throughout the study. Sudan hay (11.4 % crude protein, dry matter basis) was selected to mimic forage quality that range cattle frequently graze in the southwest region. Horn fly-induced host defensive behaviors were greater (P ≤ 0.0002) for horn fly infested cattle. Intake of water, dry matter, organic matter, crude protein, and neutral detergent fiber were similar (P ≥ 0.4765) among infested and noninfested cows. However, total volatile fatty acid concentration tended to increase (P = 0.0967) when horn flies were present. Dry matter fecal excretion and total tract digestion were not affected (P ≥ 0.2602) by horn fly infestation. These data indicate that horn fly infestations do not affect forage intake or digestion characteristics of beef cattle (Bos taurus) in confinement settings. [ABSTRACT FROM AUTHOR]

The article discusses study of impact of inconsistent consumption of insect growth regulator evaluated on filth fly population control in simulated field environment. Topics discussed include economic impact of house or horn fly on cattle operations across the U.S., larvicides that take advantage of manupitaed hormonal or protein production of immature flies and inconsistent consumption of diflubenzuron (DFB).

Horn flies (Haematobia irritans [L.]) contribute to major economic losses of pastured cattle operations, particularly in organic herds because of limitations on control methods that can be used. The objectives of this research were to determine if resistance to horn flies is a heritable trait in organic Holstein cattle, determine associations with yield traits, and to detect genomic regions associated with fly infestation. Observations of fly load were recorded from 1,667 pastured Holstein cows, of which 640 were genotyped, on 13 organic dairies across the United States. Fly load score was determined using a 0 to 4 scale based on fly coverage from chine to loin on one side of the body, with 0 indicating few to no flies and 4 indicating high infestation. The scoring system was validated by counting flies from photographs taken at the time of scoring from 252 cows. To mitigate the effect of our data structure on potential selection bias effects on genetic parameter estimates, survival to subsequent lactations of scored animals and herd-mates that had been culled before the trial was accounted for as the trait stayability. Genetic parameters were estimated using single-step genomic analysis with 3-trait mixed models that included fly score, stayability, and a third phenotype. Model effects differed by variable, but fixed effects generally included a contemporary group, scorer, parity, and stage of lactation; random effects included animal, permanent environment, and residual error. A genome-wide association study was performed by decomposing estimated breeding values into marker effects to detect significant genomic regions associated with fly score. The rank correlation between the subjective fly score and the objective count was 0.79. The average heritability of fly score (± standard error) estimated across multiple models was 0.25 ± 0.04 when a known Holstein maternal grandsire was required and 0.19 ± 0.03 when only a known Holstein sire was required. Genetic correlation estimates with yield traits were moderately positive, but a greater fly load was associated with reduced yield after accounting for genetic merit. Lower fly loads were associated with white coat coloration; a significant genomic region on Bos taurus autosome 6 was identified that contains the gene KIT , which was the most plausible candidate gene for fly resistance because of its role in coat pattern and coloration. The magnitude of heritable variation in fly infestation is similar to other traits included in selection programs, suggesting that producers can select for resistance to horn flies. [ABSTRACT FROM AUTHOR]

Stephanophyllariasis is a worldwide distributed disease and is characterized by skin lesions caused by nematodes of the genus Stephanophyllaria SP, which is transmitted through flies, specifically the horn fly. This parasitic fly plus the head and neck region, however, in hot periods of the year there is a higher amount of it, it spreads throughout the body of the bovine, injecting the worm into the skin of the same through the saliva. Flies can become contaminated with nematode when feeding sick cows and then transmit it to healthy cows. In cattle, manisfest is caused by chronic dermatitis associated with papular eruption progressing to nodules, alopecia and crusted ulceration. This parasitic infection is a zoonosis and can be transmitted to man, studies show the presence of microfilarias in the peripheral blood of newborn babies and babies generated by mothers with no skin lesions indicating that in addition to transmission to man, placental transmission of the parasite occurs. The diagnosis is made by the Veterinarian, who can confirm the presence of the parasite by collecting material from the wound, the best visualization is given in the liquid used to send tissue sample to the laboratory, called direct examination, with observation of sediment under a microscope. The treatment is performed with anthelmintic drugs such as ivermectin, levamisol and amitraz, organophosphorus compounds can be recommended for topical placement in the wound, with association of injectable drugs. [ABSTRACT FROM AUTHOR]

Sex chromosomes and sex determining genes can evolve fast, with the sex-linked chromosomes often differing between closely related species. Population genetics theory has been developed and tested to explain the rapid evolution of sex chromosomes and sex determination. However, we do not know why the sex chromosomes are divergent in some taxa and conserved in others. Addressing this question requires comparing closely related taxa with conserved and divergent sex chromosomes to identify biological features that could explain these differences. Cytological karyotypes suggest that muscid flies (e.g., house fly) and blow flies are such a taxonomic pair. The sex chromosomes appear to differ across muscid species, whereas they are conserved across blow flies. Despite the cytological evidence, we do not know the extent to which muscid sex chromosomes are independently derived along different evolutionary lineages. To address that question, we used genomic and transcriptomic sequence data to identify young sex chromosomes in two closely related muscid species, horn fly (Haematobia irritans) and stable fly (Stomoxys calcitrans). We provide evidence that the nascent sex chromosomes of horn fly and stable fly were derived independently from each other and from the young sex chromosomes of the closely related house fly (Musca domestica). We present three different scenarios that could have given rise to the sex chromosomes of horn fly and stable fly, and we describe how the scenarios could be distinguished. Distinguishing between these scenarios in future work could identify features of muscid genomes that promote sex chromosome divergence.

Horn flies (HF) are one of the most prevalent external parasites on pastured cattle in North America, although they can be found worldwide. HF cause animals severe stress leading to increased cardiac and respiratory rates, and decreased feed efficiency, average daily gain, and milk production. All these detrimental effects caused by HF contribute to over $1 dollars in economic loss in the United States, annually. Current methods of reducing fly numbers, including manure management, feed additives, and insecticides, are being utilized with varying degrees of success. However, these methods require extensive management, are temporary, and are costly to producers. While several studies have investigated the effects of horn flies on growth and milk production traits, there have been very few studies on their potential impacts on reproduction in beef cattle. Insemination and calving data collected on cows and yearling heifers at Northwest Georgia Research and Education Center between 2015 to 2022 was used to determine the effect of HF abundance on fertility. Each animal was exposed to two insemination events. Artificial Insemination (AI) was used except for cows that did not get pregnant from the first AI which were placed on pasture with a proven bull for natural service. The outcomes (success/failure) of each insemination event and calving were recorded. Still births where the dam carried the calf to term, but the calf passed during parturition were recorded as successes. As part of a research project, no fly control methods were carried out on the farms during 2019 and 2022. During these years, images of each animal were taken twice between May and August. The best image of each animal was used to estimate HF count. Animals were placed in three abundance classes (Low: 0-150, Med: 151-400, High: 401+) to analyze the effects of fly abundance on reproduction. For the remaining years (2015-2018, 2020-2021) animals received fly control and were not assessed for fly abundance. As shown Table 1, conception rates of each breeding attempt and calving rates were lower in both years where no horn fly control was used (2019 and 2022) compared with the remaining years where fly control was utilized. The decrease in conception rates when no fly control was used suggests a detrimental effect of HF on reproductive success. Additionally, for the animals measured in 2022, the average fly count for the dams who did not calf successfully was 357 which is significantly higher than the average count for the dams who did successfully calf (290). This suggests that animals with greater fly loads are less likely to carry to term. These adverse effects on reproductive health could be mitigated by genetically selecting for animals that can tolerate a greater fly load. [ABSTRACT FROM AUTHOR]

Horn flies are a major irritant to livestock. In cattle, horn flies can cause increased heart and respiratory rates, decreased feed efficiency, decreased weaning weights, and reduced milk production, resulting in substantial economic losses. In the United States, horn flies are estimated to cause more than $1 billion in economic losses on pastured cattle, annually. Reliance on management and insecticides has proven inadequate. Additionally, intensive use of insecticides has led to increased resistance in horn fly populations. Thus, there is an increasing need for a long-term solution to the horn fly problem in cattle. Assessing horn fly abundance related phenotypes under commercial conditions is costly and logistically complex. Consequently, the genetic basis of these traits remains largely unknown due to the lack of sufficient phenotypic data. Although several studies reported clear differences in fly abundance within and across breeds, only a few heritability estimates are available based on small-scale studies. This study was conducted during the summers of 2019 and 2022 (two data collections per year) on two University of Georgia associated farms, Northwest Georgia Research and Education center and Eatonton Beef Research Unit. A total of 1,047 cows and heifers were assessed by trained evaluators and several digital images were taken for each animal. Each animal was scored at least twice with some cows scored both years for a total of 4 times during the study period. During each scoring period, the best image for each animal was used to assess fly abundance using direct and sampling-based counting approaches. After edits, the data consisted of 2,197 records collected on 936 cows and heifers. The pedigree consisted of 1,226 animals. A mixed linear model that included year, farm-pen, month, and age (in years) as fixed effects and the random additive and permanent effects was used to jointly analyze three fly abundance related phenotypes. Estimates of heritability of horn fly abundance was between 0.15 and 0.21 for subjective and image-based phenotypes. Genetic correlation was high (0.83) between the image-based phenotypes and moderate between the image-based phenotypes and the subjective assessment (0.61 to 0.65). Repeatability ranged between 0.28 and 0.35 across the three traits. The lower heritability for the subjective assessment points towards added variability due to variation between evaluators. Although the results of this study support the potential to improve horn fly resistance using genetic tools, alternative phenotypes to assess fly abundance are needed. Non-count-based phenotypes could provide an attractive alternative for selecting against horn fly abundance. [ABSTRACT FROM AUTHOR]

Background: The horn fly, Haematobia irritans irritans, causes significant production losses to the cattle industry. Horn fly control relies on insecticides; however, alternative control methods such as vaccines are needed due to the fly's capacity to quickly develop resistance to insecticides, and the pressure for eco-friendly options. Methods: We used a reverse vaccinology approach comprising three vaccine prediction and 11 annotation tools to evaluate and rank 79,542 translated open reading frames (ORFs) from the horn fly's transcriptome, and selected 10 transcript ORFs as vaccine candidates for expression in Pichia pastoris. The expression of the 10 selected transcripts and the proteins that they encoded were investigated in adult flies by reverse transcription polymerase chain reaction (RT-PCR) and mass spectrometry, respectively. Then, we evaluated the immunogenicity of a vaccine candidate in an immunization trial and the antigen's effects on horn fly mortality and fecundity in an in vitro feeding assay. Results: Six of the ten vaccine candidate antigens were successfully expressed in P. pastoris. RT-PCR confirmed the expression of all six ORFs in adult fly RNA. One of the vaccine candidate antigens, BI-HS009, was expressed in sufficient quantity for immunogenicity and efficacy trials. The IgG titers of animals vaccinated with BI-HS009 plus adjuvant were significantly higher than those of animals vaccinated with buffer plus adjuvant only from days 42 to 112, with a peak on day 56. Progeny of horn flies feeding upon blood from animals vaccinated with BI-HS009 plus adjuvant collected on day 56 had 63% lower pupariation rate and 57% lower adult emergence than the control group (ANOVA: F(1, 6) = 8.221, P = 0.028 and F(1, 6) = 8.299, P = 0.028, respectively). Conclusions: The reverse vaccinology approach streamlined the discovery process by prioritizing possible vaccine antigen candidates. Through a thoughtful process of selection and in vivo and in vitro evaluations, we were able to identify a promising antigen for an anti-horn fly vaccine. [ABSTRACT FROM AUTHOR]

Background: The stable fly, Stomoxys calcitrans, is a major blood-feeding pest of livestock that has near worldwide distribution, causing an annual cost of over $2 billion for control and product loss in the USA alone. Control of these flies has been limited to increased sanitary management practices and insecticide application for suppressing larval stages. Few genetic and molecular resources are available to help in developing novel methods for controlling stable flies. Results: This study examines stable fly biology by utilizing a combination of high-quality genome sequencing and RNA-Seq analyses targeting multiple developmental stages and tissues. In conjunction, 1600 genes were manually curated to characterize genetic features related to stable fly reproduction, vector host interactions, host-microbe dynamics, and putative targets for control. Most notable was characterization of genes associated with reproduction and identification of expanded gene families with functional associations to vision, chemosensation, immunity, and metabolic detoxification pathways. Conclusions: The combined sequencing, assembly, and curation of the male stable fly genome followed by RNA-Seq and downstream analyses provide insights necessary to understand the biology of this important pest. These resources and new data will provide the groundwork for expanding the tools available to control stable fly infestations. The close relationship of Stomoxys to other blood-feeding (horn flies and Glossina) and non-blood-feeding flies (house flies, medflies, Drosophila) will facilitate understanding of the evolutionary processes associated with development of blood feeding among the Cyclorrhapha. [ABSTRACT FROM AUTHOR]

Abstract Background The horn fly (Haematobia irritans) is an obligate blood feeder that causes considerable economic losses in livestock industries worldwide. The control of this cattle pest is mainly based on insecticides; unfortunately, in many regions, horn flies have developed resistance. Vaccines or biological control have been proposed as alternative control methods, but the available information about the biology or physiology of this parasite is rather scarce. Results We present a comprehensive description of the salivary and midgut transcriptomes of the horn fly (Haematobia irritans), using deep sequencing achieved by the Illumina protocol, as well as exploring the virome of this fly. Comparison of the two transcriptomes allow for identification of uniquely salivary or uniquely midgut transcripts, as identified by statistically differential transcript expression at a level of 16 x or more. In addition, we provide genomic highlights and phylogenetic insights of Haematobia irritans Nora virus and present evidence of a novel densovirus, both associated to midgut libraries of H. irritans. Conclusions We provide a catalog of protein sequences associated with the salivary glands and midgut of the horn fly that will be useful for vaccine design. Additionally, we discover two midgut-associated viruses that infect these flies in nature. Future studies should address the prevalence, biological effects and life cycles of these viruses, which could eventually lead to translational work oriented to the control of this economically important cattle pest.

Bovine leukemia virus (BLV) is the agent responsible for enzootic bovine leukosis, the most common neoplastic disease in cattle. The horn fly, a major hematophagous pest of cattle, is able to transmit different diseases in cattle. However, its implication in BLV transmission under a natural environment is still discussed. The objectives of this work were to determine the presence of BLV in horn flies (by sequencing) and to evaluate the ability of horn flies to transmit BLV to cattle (through an experimental assay under a natural environment). To demonstrate the presence of BLV in the flies, 40 horn flies were collected from a BLV-positive cow with a sweep net and ten pools with four horn-fly mouthparts each were prepared. The presence of BLV was determined by nested PCR and sequencing. To demonstrate BLV transmission, other 40 flies were collected from the same BLV-positive cow with a sweep net. Eight homogenates containing five horn-fly mouthparts each were prepared and injected to eight cows of different breeds, and blood samples were collected every 21 days. Then, to evaluate the ability of horn flies to transmit BLV to grazing cattle under natural conditions, both infected and uninfected cattle from the experimental transmission assay were kept together in the same paddock with more than 200 horn flies per animal for 120 days. Blood samples were collected every 20 days and the number of flies determined. The sequencing results confirmed the presence of the provirus in horn flies. The results also confirmed that BLV transmission is a possible event, at least experimentally. However, the role of horn flies as vectors of BLV under a natural grazing system is still discussed.

The horn fly, Haematobia irritans irritans (L.), is one of the most important external parasites of cattle in North America and elsewhere. Horn fly adults have an intimate association with cattle, their primary host. With their often-high numbers and by feeding up to 38 times per day per fly, horn flies stress cattle. The resulting productivity loss is valued at more than 2.3 billion USD in the United States. Insecticides are commonly used to mitigate direct injury from feeding and indirect injury from disease transmission. This paper discusses horn fly biology, distribution, and management. Emphasis is on promising new approaches in novel insecticides, repellents, biological control, vaccines, animal genetics, and sterile insect technology that will lead to effective preventative tactics and the integration of smart technologies with horn fly management. We conclude with a discussion of research needs necessary to shift horn fly integrated pest management to an emphasis on preventative tactics and the precision use of reactive techniques. [ABSTRACT FROM AUTHOR]

The horn fly, Haematobia irritans L. (Diptera: Muscidae), is a persistent pest of cattle globally. A threshold of 200 flies per animal is considered the standard management goal; however, determining when that threshold has been exceeded is difficult using visual estimates that tend to overestimate the actual fly densities and are, at best, subjective. As a result, a more reliable and durable method of determining horn fly densities is needed. Here, we describe the methods commonly used to quantify horn fly densities including visual estimates and digital photography, and provide examples of quantification software and the prospect for computer automation methods. [ABSTRACT FROM AUTHOR]

The horn fly, Haematobia irritans (L.), is an obligate hematophagous ectoparasite of cattle, and one of the most important pests of cattle causing unrealized gains or losses in meat and milk production. The present study describes the difficulties that arise when research programs have attempted to maintain this pest, both on-host and off-host, in a laboratory environment. Suggestions aimed at assisting future researchers in successfully colonizing horn flies in the laboratory are provided. [ABSTRACT FROM AUTHOR]

Haematobia irritans, commonly known as the horn fly, is a globally distributed blood-feeding pest of cattle that is responsible for significant economic losses to cattle producers. Chemical insecticides are the primary means for controlling this pest but problems with insecticide resistance have become common in the horn fly. To provide a foundation for identification of genomic loci for insecticide resistance and for discovery of new control technology, we report the sequencing, assembly, and annotation of the horn fly genome. The assembled genome is 1.14 Gb, comprising 76,616 scaffolds with N50 scaffold length of 23 Kb. Using RNA-Seq data, we have predicted 34,413 gene models of which 19,185 have been assigned functional annotations. Comparative genomics analysis with the Dipteran flies Musca domestica L., Drosophila melanogaster, and Lucilia cuprina, show that the horn fly is most closely related to M. domestica, sharing 8,748 orthologous clusters followed by D. melanogaster and L. cuprina, sharing 7,582 and 7,490 orthologous clusters respectively. We also identified a gene locus for the sodium channel protein in which mutations have been previously reported that confers target site resistance to the most common class of pesticides used in fly control. Additionally, we identified 276 genomic loci encoding members of metabolic enzyme gene families such as cytochrome P450s, esterases and glutathione S-transferases, and several genes orthologous to sex determination pathway genes in other Dipteran species.

In horn flies, Haematobia irritans irritans (Diptera: Muscidae) (Linnaeus, 1758), target site resistance to pyrethroids can be diagnosed by an allele‐specific PCR that genotypes individual flies at both the super‐kdr (skdr) and the knock down resistance (kdr) associated loci. When this technique uses genomic DNA as template, modifications, such as alternative RNA splicing and RNA editing are not specifically detected. Alternative splicing at the skdr locus has been reported in Dipterans; thus, the genomic DNA‐based allele‐specific PCR may not accurately reflect the frequency of the skdr mutation in horn fly field populations. To investigate if alternative splicing occurs at the skdr locus of horn flies, genomic DNA and cDNA sequences isolated from two wild populations and two laboratory‐reared colonies with varying degrees of pyrethroid resistance were compared. There was no indication of alternative splicing at the super‐kdr locus neither in the wild populations nor in the laboratory‐reared colonies. [ABSTRACT FROM AUTHOR]

BACKGROUND: Haematobia spp., horn flies (HF) and buffalo flies (BF), are economically important ectoparasites of dairy and beef cattle. Control of these flies relies mainly on treating cattle with chemical insecticides. However, the development of resistance to commonly used compounds is compromising the effectiveness of these treatments and alternative methods of control are required. Wolbachia are maternally transmitted endosymbiotic bacteria of arthropods that cause various reproductive distortions and fitness effects, making them a potential candidate for use in the biological control of pests. The first step towards this is the establishment and adaptation of xenobiotic infections of Wolbachia in target host cell lines. RESULTS: Here, we report the successful establishment of a continuous HF cell line (HIE‐18) from embryonic cells and its stable transinfection with Wolbachia strains wAlbB native to mosquitoes, and wMel and wMelPop native to Drosophila melanogaster. HIE‐18 cells were typically round and diploid with ten chromosomes (2n = 10) or tetraploid with 20 chromosomes (4n = 20), with a doubling time of 67.2 h. Wolbachia density decreased significantly in HIE‐18 cells in the first 48 h of infection, possibly due to overexpression of antimicrobial peptides through the Imd immune signalling pathway. However, density recovered after this time and HIE‐18 cell lines stably infected with the three strains of Wolbachia have now each been subcultured more than 50 times as persistently infected lines. CONCLUSION: The amenability of HF cells to infection with different strains of Wolbachia and the establishment of stable sustaining infections suggest the potential for use of Wolbachia in novel approaches for the control of Haematobia spp. Further, the availability of the HIE‐18 cell line will provide an important resource for the study of genetics, host–parasite interactions and chemical resistance in Haematobia populations. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Background: Buffalo flies (Haematobia irritans exigua) (BF) and closely related horn flies (Haematobia irritans irritans) (HF) are invasive haematophagous parasites with significant economic and welfare impacts on cattle production. Wolbachia are intracellular bacteria found widely in insects and currently of much interest for use in novel strategies for the area wide control of insect pests and insect-vectored diseases. In this paper, we report the transinfection of BF towards the development of area-wide controls. Methods: Three stages of BF; embryos, pupae and adult female flies, were injected with different Wolbachia strains (wAlbB, wMel and wMelPop). The success of transinfection and infection dynamics was compared by real-time PCR and FISH and fitness effects were assessed in transinfected flies. Results: BF eggs were not easily injected because of their tough outer chorion and embryos were frequently damaged with less than 1% hatch rate of microinjected eggs. No Wolbachia infection was recorded in flies successfully reared from injected eggs. Adult and pupal injection resulted in higher survival rates and somatic and germinal tissue infections, with transmission to the succeeding generations on some occasions. Investigations of infection dynamics in flies from injected pupae confirmed that Wolbachia were actively multiplying in somatic tissues. Ovarian infections were confirmed with wMel and wMelPop in a number of instances, though not with wAlbB. Measurement of fitness traits indicated reduced longevity, decreased and delayed adult emergence, and reduced fecundity in Wolbachia-infected flies compared to mock-injected flies. Effects varied with the Wolbachia strain injected with most marked changes seen in the wMelPop-injected flies and least severe effects seen with wAlbB. Conclusions: Adult and pupal injection were the most suitable methods for transinfecting BF and all three strains of Wolbachia successfully replicated in somatic tissues. The Wolbachia-induced fitness effects seen in transinfected BF suggest potential for use of the wMel or wMelPop strains in Wolbachia-based biocontrol programmes for BF. [ABSTRACT FROM AUTHOR]