Surveillance and screening of Stomoxyinae flies from Mallorca Island (Spain) reveal the absence of selected pathogens but confirm the presence of the endosymbiotic bacterium Wolbachia pipientis

Adult brachycera biting flies can significantly impact livestock through both direct effects (reduction of food intake, disturbance, painful bites, and blood loss) and indirect effects (pathogen transmission), leading to substantial economic losses and production damage. This study aimed to assess the presence of blood-sucking flies in six mixed-animal farm environments on the island of Mallorca (Balearic Islands, Spain) by employing multiple trapping methods. Additionally, distribution maps of brachycera biting fly species recorded in Spain were created, based on data extracted thorough review of scientific literature and citizen digital databases. Investigation of several pathogens, including equine infectious anemia virus (EIAV), Anaplasmataceae bacteria, and piroplasm protozoa, was carried out using different PCR targets (18S rRNA, 16S rRNA, groESL, and tat genes). Citizen science databases and literature review corroborated the consistent distribution trend for two Stomoxyinae species, underscoring the importance of citizen collaboration as a complement to traditional entomological surveillance. Our study confirmed the presence of two biting Stomoxyinae species: the prevalent stable fly Stomoxys calcitrans across all sampled farms, and the horn fly Haematobia irritans, which turned out to be less abundant. DNA barcoding techniques validated the identification of the two species. Neither EIAV nor bacterial/protozoan pathogens were detected using the selected PCR targets in either fly species. However, Wolbachia pipientis (clustered in the supergroup A together with the only sequence of W. pipientis from the USA) was identified through PCR targeting 16S rRNA, groESL and wsp genes in all pools of H. irritans (n = 13) collected from two of the examined farms. This study represents the first attempt to investigate pathogens in Stomoxyinae biting flies in Spain. The discovery of the endosymbiotic Wolbachia organism in H. irritans represents the first record in Spain and the second from Europe. This finding holds significant implications for future research on the applications of this bacterium in biocontrol programs.

First report of the efficacy of a fluralaner-based pour-on product (Exzolt® 5%) against ectoparasites infesting cattle in Brazil

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.

Horn fly transcriptome data of ten populations from the southern United States with varying degrees and molecular mechanisms of pesticide resistance

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).

Strategic control of cattle co-parasitized by tick, fly and gastrointestinal nematodes: Is it better to use ecto + endoparasiticide or just endectocide formulations?

Ticks, flies, and gastrointestinal helminths (GINs) significantly affect cattle productivity; thus, ectoparasiticide, endoparasiticide, and endectocide drugs have commonly been used for their control. The study aimed to compare the technical (parasites counts), productive, and financial effects of a treatment protocol comprising ecto- + endoparasiticides formulations (T01: fluazuron 2.5 mg/kg + fipronil 1.25 mg/kg and fenbendazole 5 mg/kg; n = 15) to a treatment with one formulation of endectocide (T02: ivermectin 450 μg/kg + abamectin 250 μg/kg; n = 15) over 308 days under field conditions in crossbred cattle co-parasitized by Rhipicephalus microplus, Haematobia irritans, and GINs. Bovine weight gain and return on investment (ROI) were also evaluated. Bovines from T01 received four treatments against the cattle tick and two against two GINs. For T02, four treatments were performed. Animals from T01 gained 15.4 kg more than T02 and provided a comparative ROI of 15.8. In cattle co-parasitized with R. microplus, H. irritans, and GINs, the treatment protocol used in this study with ecto- + endoparasiticidal action formulations showed better technical results regarding parasite counts and productive and financial data than the strategic treatment protocol using only an endectocide formulation.

Don) Florin Heartwood against Horn Flies, Haematobia irritans (Diptera: Muscidae)

Haematobia irritans is a cosmopolitan obligate blood-feeding ectoparasite of cattle and is the major global pest of livestock production. Currently, H. irritans management is largely dependent on broad-spectrum pesticides, which has led to the development of insecticide resistance. Thus, alternative control methods are needed. Essential oils have been studied as an alternative due to their wide spectrum of biological activities against insects. Thus, the main aim of this study was to evaluate the insecticidal, repellent and antifeedant activity of the essential oils from Blepharocalyx cruckshanksii leaves and Pilgerodendron uviferum heartwood against horn flies in laboratory conditions. The composition of the essential oils was analyzed using gas chromatography coupled to mass spectrometry. Accordingly, α-pinene (36.50%) and limonene (20.50%) were the principal components of the B. cruckchanksii essential oil, and δ-cadinol (24.16%), cubenol (22.64%), 15-copaenol (15.46%) and δ-cadinene (10.81%) were the most abundant compounds in the P. uviferum essential oil. Mortality of flies and feeding behavior were evaluated by non-choice tests, and olfactory response was evaluated using a Y-tube olfactometer. Both essential oils were toxic to horn flies, with LC50 values for B. cruckchanksii essential oil of 3.58 µL L-1 air at 4 h, and for P. uviferum essential oil of 9.41 µL L-1 air and 1.02 µL L-1 air at 1 and 4 h, respectively. Moreover, the essential oils exhibited spatial repellency in the olfactometer using only 10 µg of each oil, and these significantly reduced the horn fly feeding at all doses evaluated. Although further laboratory and field studies related to the insectistatic and insecticide properties of these essential oils against H. irritans are necessary, B. cruckshanksii leaves and P. uviferum heartwood essential oils are promising candidates for horn fly management.

Antifeedant Effects and Repellent Activity of Loline Alkaloids from Endophyte-Infected Tall Fescue against Horn Flies, Haematobia irritans (Diptera: Muscidae)

Haematobia irritans is an obligate bloodsucking ectoparasite of cattle and is the global major pest of livestock production. Currently, H. irritans management is largely dependent upon broad-spectrum pesticides, which lately has led to the development of insecticide resistance. Thus, alternative control methods are necessary. Endophyte-infected grasses have been studied as an alternative due to their capability to biosynthesize alkaloids associated with anti-insect activities. Thus, the main aim of this study was to evaluate the antifeedant and repellent activity of lolines obtained from endophyte-infected tall fescue against H. irritans adults in laboratory conditions. The alkaloid extract (ALKE) was obtained by acid–base extraction. N-formyl loline (NFL) and N-acetyl loline (NAL) were isolated by preparative thin layer chromatography (pTLC) and column chromatography (CC), and the loline was prepared by acid hydrolysis of a NFL/NAL mixture. Loline identification was performed by gas chromatography coupled to mass spectrometry (GC/MS). Feeding behavior was evaluated by a non-choice test, and olfactory response was evaluated using a Y-tube olfactometer. Accordingly, all samples showed antifeedant activities. NFL was the most antifeedant compound at 0.5 µg/µL and 1.0 µg/µL, and it was statistically equal to NAL but different to loline; however, NAL was not statistically different to loline. NFL and NAL at 0.25 µg/µL were more active than loline. All samples except loline exhibited spatial repellency in the olfactometer. Thus, the little or non-adverse effects for cattle and beneficial activities of those lolines make them suitable candidates for horn fly management.

Parabronema skrjabini (Nematoda: Habronematidae) infection and development in the intermediate host-Haematobia irritans (Linnaeus, 1758) in Inner Mongolia, China

Parabronemosis is a disease that severely threatens camel health, causing huge economic losses to industries involved in camel husbandry. Previous studies have reported that horn flies (Haematobia irritans) act as intermediate hosts of Parabronema skrjabini; however, the infection and developmental processes of P. skrjabini in horn flies remain unclear. In the present study, the infection rates of P. skrjabini were determined in morphologically and molecularly identified horn flies collected from Bactrian camels (Camelus bactrianus) producing regions in Inner Mongolia, China that have high P. skrjabini infection rates. The horn flies were dissected to obtain the nematode larvae at various instar stages. The P. skrjabini found in the different instar stages of horn fly instars were counted and identified to assess the infection and developmental status. Nematode larvae at different developmental stages were obtained from the horn fly instars for further molecular analysis. Sequencing results confirmed that the nematode larvae were P. skrjabini. Furthermore, we found that the mean growth rate of the nematode larva increased as the horn fly instars develops. The results suggested that P. skrjabini infected the horn flies at the larval instar stage, and that the nematode larvae developed simultaneously with the horn fly instars stages. Our findings provide useful information into the elucidation of P. skrjabini infection and life history by studying horn fly development.

Impacts of long-term insecticide treatment regimes on skdr and kdr pyrethroid resistance alleles in horn fly field populations

We evaluated the effects of four different 6-year duration control strategies on the resistance levels and frequency of the pyrethroid target site resistance alleles, superkdr (skdr) and kdr, at four field populations of Haematobia irritans irritans (Linnaeus, 1758) (Diptera: Muscidae) in Louisiana, USA. Consecutive use of pyrethroid ear tags for 6 years caused a significant increase in the resistance ratio to pyrethroids as well as the frequencies of both skdr and kdr resistance alleles. After 3 years of consecutive use of pyrethroid ear tags, followed by 1 year with no treatment, and followed by 2 years with organophosphate ear tags, the resistance ratio for pyrethroid was not significantly affected, the %R-skdr significantly dropped while the %R-kdr allele remained relatively high and stable. Similar results were observed when pyrethroid ear tags were used for three consecutive years, followed by 1 year with no treatment, and followed by 2 years with endosulfan ear tags; however, this treatment resulted in a slight increase in the resistance ratio for pyrethroids. In a mosaic, the resistance ratio for pyrethroids showed a 2.5-fold increase but the skdr-kdr genetic profiles did not change, as the %R alleles (skdr and kdr) remained low and stable through the 6 years. Lack of exposure to pyrethroid insecticides for 3 years significantly affected the skdr mutation but not the kdr mutation, preventing re-establishment of susceptibility to pyrethroids. SS-SR (skdr-kdr) individuals were responsible for the maintenance of the kdr mutation in two of the populations studied, and fitness cost seems to strongly affect the SR-RR genotype. None of the four treatment regimens evaluated in the study had satisfactory results for the management of kdr resistance alleles.

Pyrethroid and organophosphate pesticide resistance in field populations of horn fly in Brazil

Pesticides are used worldwide to control arthropod parasites in cattle herds. The indiscriminate and/or inappropriate use of pesticides without veterinary guidance is a reality in several countries of South America. Improper pesticide use increases the chances of contamination of food and the environment with chemical pesticides and their metabolites. Reduction of these contamination events is an increasing challenge for those involved in livestock production. The horn fly, Haematobia irritans (Linnaeus) (Diptera: Muscidae), is one of the most economically important parasites affecting cattle herds around the world. As such, horn fly control efforts are often required to promote the best productive performance of herds. Pesticide susceptibility bioassays revealed that pyrethroid resistance was widespread and reached high levels in horn fly populations in the Brazilian state of Rondônia. The knockdown resistance (kdr) sodium channel gene mutation was detected in all horn fly populations studied (n = 48), and the super kdr sodium channel gene mutation was found in all homozygous resistant kdr individuals (n = 204). Organophosphate resistance was not identified in any of the fly populations evaluated.

Study of horn flies as vectors of bovine leukemia virus

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 10 pools with four horn-fly mouthparts each were prepared. The presence of BLV was determined by nested polymerase chain reaction 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 was 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.

Hematobin is a novel immunomodulatory protein from the saliva of the horn fly Haematobia irritans that inhibits the inflammatory response in murine macrophages

Background

The horn fly Haematobia irritans is a blood-sucking ectoparasite responsible for substantial economic loss of livestock. Like other hematophagous arthropods species, the successful blood-feeding of H. irritans is highly dependent on the modulation of the host’s hemostasis and immune system. Here, we evaluated the biological activity of hematobin (HTB), a protein recently identified in the H. irritans saliva, on macrophage biology. The goal was to understand the putative interactions between the components of H. irritans saliva and the early host immune responses.

Results

Thioglycolate-elicited peritoneal macrophages from BALB/c mice were stimulated by lipopolysaccharide (LPS) plus interferon-γ (IFN-γ) in the presence or absence of recombinant HTB. The presence of the salivary protein in the cultures inhibited nitric oxide production and decreased the inducible nitric oxide synthase (iNOS) expression induced by LPS plus IFN-γ. The tumor necrosis factor-α (TNF-α) and interleukin-12p40 (IL-12p40) levels were also reduced in the macrophages pre-incubated with HTB; these findings correlated to the decreased NF-κB expression. The biological activities described here were not associated with changes in annexin V binding to macrophages suggesting that HTB does not induce cell death. In addition, the activity of HTB seems to be specific to macrophages because no changes were observed in lymphocyte proliferation or cytokine production.

Conclusions

We describe here the first bioactive salivary protein of H. irritans. We characterized its ability to modulate macrophage inflammatory response, and the results can help explain how horn flies modulate the host immune system to feed on blood.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3017-z) contains supplementary material, which is available to authorized users.

Resistance to Permethrin, β-cyfluthrin, and Diazinon in Florida Horn Fly Populations

Horn flies, Haematobia irritans, a major cattle pest in the USA, cause substantial economic losses and current control methods rely heavily on insecticides. Three horn fly populations were evaluated for insecticide susceptibility to permethrin, β-cyfluthrin, and diazinon. Susceptibility was variable by population, with the greatest resistance exhibited by a 66-fold resistance ratio (RR) to permethrin and >14-fold RR to diazinon. Mechanisms of resistance were determined using molecular techniques and enzymatic assays. The knockdown resistance (kdr) genotype (L150F) associated with pyrethroid resistance, and a G262A mutation in acetylcholinesterase, previously associated with organophosphate resistance, were found in all field populations evaluated. Insensitivity of diazoxon at the acetylcholinesterase (AChE) target site was significantly different in horn flies from one of the field sites. For metabolic detoxifying enzymes, cytochrome P450 nor general esterases showed a significant difference between field strains and a laboratory susceptible strain. Pyrethroid resistance was likely due to the presence of the L150F mutation in the population. In vitro studies targeting the AChE enzyme did not support the notion that the G262A mutation was the sole cause of resistance to organophosphates, and, therefore, the exact resistance mechanism to diazinon was not able to be confirmed.

Molecular Characterization of the Horn Fly Haematobia irritans Infesting Horses in Central Anatolia Region in Turkey

This study reports intense horn fly infestations of horses raised in an important wetland ecosystem, Sultan Marshes in Central Anatolia, Turkey. In total, seven horses raised together were found to be harbored over 500 flies per site of each animal. Totally, 376 fly specimens were collected from the horses by using the nets and were subjected to the laboratory for species identification. All flies were morphologically identified as the adults of Haematobia irritans. Partial fragments of mitochondrial cytochrome oxidase I (mt-COI) gene from totally 50 isolates were amplified for sequence and phylogenetic analyses. The mt-COI sequence analyses revealed no polymorphism among the isolates and explored a unique haplotype for H. irritans. A mean haplotype and nucleotide diversities of 0.8571 and 0.00695 were determined, respectively, within the COI data set of H. irritans, and newly characterized haplotype from Turkey exhibited a mean intraspecific genetic difference of 1.0 to the all published sequences of the isolates from several countries. COI data set also revealed a mean interspecific genetic difference of 1.7 between H. irritans and Haematobia exigua.

Effects of the Botanical Compound p-Anisaldehyde on Horn Fly (Diptera: Muscidae) Repellency, Mortality, and Reproduction

The horn fly, Haematobia irritans irritans (L.) (Diptera: Muscidae), is an economically important obligate blood feeder that mainly attacks cattle in Europe, Asia, and North and South America. As horn fly resistance to conventional insecticides becomes more common, alternative control tactics, such as application of bioactive botanical natural products are being investigated. p-Anisaldehyde has been found in many plant species, and it has shown effects that include mortality, attractancy, and interference with host seeking. The series of bioassays we developed was effective for assessing a range of horn fly responses to chemicals and probably those of some other filth fly species. In our study, p-anisaldehyde was lethal to horn fly eggs at concentrations of 0.00001%, and possibly less. Mixed into cow manure, 5000-20,000 ppm p-anisaldehyde reduced horn fly larvae by 85.4%-100%. p-Anisaldehyde caused some immobilization of adult horn flies when exposed by direct contract with spray droplets and by fumigation. Mortality was 90%-100% in response to 5%-10% concentrations by 30 min, and LD50 and LD90 values are reported for five times from 30 min-4 h. Complete horn fly mortality was achieved by fumigation with 0.75% p-anisaldehyde by 3 h in an enclosed space, and we determined that fumigation was more (≈12.5-fold) lethal to adult horn flies than sprayed droplets. Although horn flies were not repelled by p-anisaldehyde in static air tube olfactometers, the compound completely deterred feeding from cotton pads soaked in bovine blood in response to concentrations of 0.6% and greater in ventilated containers. Although horn fly control is not likely to use fumigation methods, p-anisaldehyde might be useful for adult control using sprays and egg and larval control using feed-through techniques. Exposure to sublethal concentrations of p-anisaldehyde did not affect horn fly egg production and hatching. Aside from causing different responses in the same species of arthropod, p-anisaldehyde has a variety of effects on other arthropods. Research on this compound as a potentially multifaceted pest management tool has been sparse. This study, for example, is the first to demonstrate p-anisaldehyde's feeding deterrent and immobilization properties and effects on different life stages.

Efficiency of a walk-through fly trap for Haematobia irritans control in milking cows in Uruguay

Haematobia irritans (horn fly) is a bloodsucking insect that affects grazing cattle. Since this fly's introduction into Uruguay in 1992, pest management practices used to control the insect have been exclusively based on the use of insecticides, which has caused synthetic pyrethroid resistance. The use of insecticides is a major constraint to livestock production due to food safety and environmental concerns. This study evaluated the effectiveness of a walk-through fly trap for horn fly control. The field trail was conducted in 18 trail evaluations dates from 2015 to 2016 in Holstein-Frisian lactating cows on two dairy farms in southern Uruguay. The traps were placed at the exit of the milking parlor. Two digital cameras were used to record video at the entrances and exits of the traps. On each of the 18 trail evaluation, between 30 and 158 cows were randomly selected for fly counting according to video records. On Farm 1, a total of 718 cows were assessed. The median number of flies per cow at the entrance of the traps was 22 (ranging from 1 to 199), while the median number at the exit was three flies per cow (ranging from 0 to 22). The median efficiency of the trap was 88%. Farm 2 had 345 observations, and the median fly count at the entrance of the traps was of 22 flies per cow (ranging from 1 to 129) and four flies at the exit (ranging from 0 to 35) with a median efficiency of 82%. It was observed that the effectiveness of the fly traps varied depending on the number of flies at entry, the season of the year and the farm site. In conclusion, fly traps could be used for the control of H. irritans in milking cows without the use of insecticides.

Comparing Visual and Digital Counting Methods to Estimate Horn Fly (Diptera: Muscidae) Populations on Cattle

Horn fly, Haematobia irritans (L.), population estimates often serve as a diagnostic tool prior to implementing managerial control options available to researchers and producers. Digital photographs taken of cattle infested with horn flies have been suggested to provide similarly accurate population estimates as compared with traditional visual assessments. The objective of this study was to compare visual and digital techniques used to estimate horn fly populations. Sixteen Angus × Hereford yearling heifers artificially infested with four levels of horn flies (Low = 0 flies; Medium = 250 flies; High = 500 flies; Extreme = 1,000 flies) were evaluated. Population estimates were taken visually by experienced (VE1) and inexperienced (VE2) technicians, as well as digitally, with photographs taken on both lateral sides of the south-facing animal. Horn flies were counted in both photographs and combined (CDC) for full body estimates. In addition, the highest photographed side population times two (DDC) was used for comparison. Estimations were made at 0700, 1200, and 1900 h the day following infestation. A time of observation × infestation level interaction (P < 0.01) was detected. On average, VE1 population estimates were greater (P < 0.01) than any other counting method observed. Morning estimates were greater (P < 0.05) than those taken at noon or in the early evening regardless of counting method. Further research regarding the standardization of these techniques to ensure more accurate population estimates is needed before these methods can be incorporated into integrated pest management programs.

Evaluation of Hematobin as a Vaccine Candidate to Control Haematobia irritans (Diptera: Muscidae) Loads in Cattle

The horn fly, Haematobia irritans (L.), is a blood-sucking livestock ectoparasite responsible for substantial livestock losses. In the present work, the potential use of recombinant hematobin (HTB), a horn fly salivary protein, as an antigen for cattle vaccination was investigated. In this trial, horn fly loads and H. irritans's blood intake were assessed in vaccinated (n = 4) and control (n = 4) crossbred dark-coated steers, which were naturally infected. The vaccinated group received a 1 ml subcutaneous injection of 100 µg of HTB protein emulsified in 500 µl of Incomplete Freund Adjuvant (AIF) on days 0 and 30. The control group received on the same days 1 ml of distilled water emulsified in 500 µl of AIF. The vaccinated group had significantly more HTB-specific IgG antibodies after the HTB booster and had a lower fly load than the control group (206 ± 23 vs. 285 ± 23 flies per animal, respectively). Blood intake by H. irritans did not differ between groups. In summary, these results suggest that vaccinating cattle with HTB could reduce cattle H. irritans load.

Discovery, Development, and Evaluation of a Horn Fly-Isolated (Diptera: Muscidae) Beauveria bassiana (Hypocreales: Cordyciptaceae) Strain From Florida, USA

The horn fly, Haematobia irritans (L.) is an important cattle pest and traditionally has been managed using insecticides; however, many horn fly populations are insecticide-resistant in United States. Use of alternative control techniques has been limited because of the challenges of managing a fly pest on pastured cattle. After the discovery of a wild horn fly infected with Beauveria bassiana in Florida, the fungus was cultured and evaluated for efficacy against laboratory-reared horn flies. This fungal strain was selected for increased virulence by passage through laboratory-reared horn fly hosts to shorten interval from infection to fly death and subsequent conidia formation, properties important to future use of the fungus as a biological control agent against horn flies. After seven passages through horn fly hosts, fly mortality was not significantly accelerated as evaluated through LT50 values, but conidia were readily produced from these killed flies. Although further development is needed to improve fungal efficacy, this fungal strain holds promise as a biological control agent for inclusion in horn fly integrated pest management programs.

Use of electroporation as an option to transform the horn fly, Haematobia irritans: a species recalcitrant to microinjection

The horn fly, Haematobia irritans, is a serious pest of cattle in North America. The control of horn flies has primarily relied on insecticides. However, the heavy use of insecticides has led to the development of insecticide resistance in horn flies. Novel methods to control horn flies are greatly needed. Transgenic technology is an effective tool to genetically modify insects and may lead to novel methods of pest control based on genomic approaches. Here we report a piggyBac-mediated transformation of the horn fly via electroporation. Transformation with a DsRed fluorescent marker protein coding region was verified by PCR analysis of individual fly bodies and pupal cases and sequencing of PCR products. However, Southern blot analysis failed to indicate the DsRed gene was integrated into the horn fly genome. Thus, the electroporation protocol may have caused the DsRed gene to be integrated into bacterial symbionts of the horn fly.

Horn fly larval survival in cattle dung is reduced by endophyte infection of tall fescue pasture

BACKGROUND

The potential for using endophytic microorganisms in pest control has increased during the last 40 years. In this study, we investigated the impact of endophyte (Neotyphodium coenophialum) infection of cattle pasture upon the survival of the horn fly, Haematobia irritans, a major agricultural pest affecting livestock in many parts of the world.

RESULTS

In laboratory assays, where cattle dung collected from endophyte-infected (E+) tall fescue cultivar K-31 was used as the oviposition substrate, larval development was significantly reduced compared with development on cattle dung from steers that grazed uninfected (E-) tall fescue. Furthermore, studies with cattle dung supplemented with the alkaloid fraction extracted from the endophytic fungi revealed significant larval mortality, and HPLC analysis identified two alkaloids, peramine and lolitrem B. The development of larvae was shown to be significantly reduced in field-collected cattle dung. These results suggest that part of the toxicity of alkaloids contained in endophytes is transferred to faecal matter, causing an increase in mortality of H. irritans.

CONCLUSION

These data suggest that endophyte infection of cattle pasture, i.e. modified pasture management, can significantly affect horn fly development. © 2015 Society of Chemical Industry.

Behavioral Responses of Cattle to Naturally Occurring Seasonal Populations of Horn Flies (Diptera: Muscidae) Under Rangeland Conditions

The behavioral responses of cattle under the influence of naturally occurring seasonal horn fly, Haematobia irritans (L.), populations were evaluated under rangeland conditions. This study was replicated four times using 10 cows as the subsampling unit equipped with GPS collars scheduled to receive locational fixes every 5 min for 6 d prior to, and 6 d following horn fly insecticidal control application. Data derived from GPS collars were used to evaluate potential horn fly-induced behavioral modifications expressed during predawn, daytime, and nighttime periods. These data were used to analyze variables, which included distance travelled, daily area explored, vertical and horizontal head movements, and inferred activities such as resting, grazing, and walking. Horn fly populations were estimated using daily visual counts and were reduced significantly on animals following insecticidal application. There was no significant difference between treatment periods in any of the aforementioned analyzed variables. During the night-time hours estimated differences (pretreatment minus posttreatment) for distance travelled, area explored, and vertical head movements were 0.81 ± 0.46 km/d, 0.35 ± 0.21 km(2)/d, and 7.25 ± 5.30 counts/d, respectively. The implications of these observations are discussed.

Comparisons of antifeedancy and spatial repellency of three natural product repellents against horn flies, Haematobia irritans (Diptera: Muscidae)

BACKGROUND

Horn flies are among the most important biting fly pests of cattle in the United States. Horn fly management is largely dependent upon pesticides, which ultimately leads to the rapid development of insecticide resistance. Alternative control strategies, including repellents, have shown promising results in reducing fly biting. In the present study, we examined the efficacy and longevity of recently identified natural product repellents against horn flies.

RESULTS

Catnip oil, geraniol and C8910 acids reduced horn fly feeding in a laboratory bioassay and also exhibited spatial repellency in the olfactometer. Residual activity was observed for up to 3 days in laboratory assays; however, 24 h of residual effectiveness was observed from the two repellents when applied on cattle in the field. The limited residual effectiveness was correlated with the high volatility of the major active repellent compounds.

CONCLUSION

All three natural product repellents effectively repel biting horn flies, exhibiting both feeding deterrence and spatial repellency. They may be used for developing an effective push-pull strategy with a slow release matrix that can prolong their effectiveness for horn fly management.

Development of a novel walk-through fly trap for the control of horn flies and other pests on pastured dairy cows

A prototype walk-through fly vacuum system, designed to remove horn flies Haematobia irritans (L.) (Diptera: Muscidae) from cattle, was developed and tested for efficacy. The study was conducted during 4 fly seasons over 17 consecutive weeks each year within the months of May through September at 1 dairy research herd in the coastal plain of North Carolina. Additional data on horn flies, as well as face flies (Musca autumnalis) and stable flies (Stomoxys calcitrans), were collected during 1 yr from 7 commercial pasture-based and organic dairy farms in the piedmont region of North Carolina. The number of flies observed on animals in the pasture was compared with the number of flies collected in the trap. Studies were initiated after horn fly densities had met or exceeded a threshold of 200 flies per animal. The vacuum trap removed between 1.3 and 2.5 million flies annually from the research station cattle. Most fly removal occurred during the first few weeks of operation and maintained densities below threshold thereafter. Cattle using the fly trap at the research farm had only about 28% the number of horn flies as untreated cattle, and reductions ranged from 67.5 to 74.5% across the 4-yr study. In addition to large numbers of horn flies, traps placed on commercial dairies during 1 yr collected stable flies, face flies, and house flies, all species with differing behavior and larger in size than horn flies. The estimated cost of running the trap is $72 per season at commercial rates of $0.12 per hour and an expected 4h of daily operation during the time of milking. Use of a vacuum system as described herein has potential as a cost-effective method in reducing populations of parasitic flies in pasture-based dairy production systems without the use of insecticides.

Accessibility of blood affects the attractiveness of cattle to horn flies

The burden of infestation of the horn fly, Haematobia irritans (Linnaeus) (Diptera: Muscidae), differs among bovines within the same herd. We hypothesized that these differences might be related to the epidermal thickness of the cattle and the blood intake capacity of the fly. Results showed that dark animals carried more flies and had a thinner epidermis than light-coloured animals, which was consistent with the greater haemoglobin content found in flies caught on darker cattle. Similarly, epidermal thickness increased with body weight, whereas haemoglobin content decreased. Overall, we suggest that accessibility of blood is a factor that partially explains cattle attractiveness to flies.

aureus antibody titres in holstein heifers

Staphylococcus aureus remains a major mastitis-causing pathogen in growing dairy heifers, resulting in damage to developing milk secretory tissue. The purpose of this study was to evaluate the role of horn flies as vectors in the spread of S. aureus among dairy heifers immunized with a S. aureus bacterin. We analyzed the prevalence of mastitis among quarters, evaluated teat skin condition (as a result of biting flies) prior to and after insecticide administration, and measured serum anti-S. aureus antibody titres monthly after vaccination. Response to S. aureus immunization was poor; however, titres increased 2- to 3-fold during the period when fly populations increased drastically and teat skin condition worsened, especially front quarter teat condition. Presence of flies and the resulting teat lesions were associated with a high level of S. aureus mastitis. Use of an insecticidal pour-on reduced fly populations and healed teat lesions, but existing cases of mastitis required antibiotic therapy.