Suppression of mosquito (Diptera: Culicidae) and black fly (Diptera: Simuliidae) blood feeding from Hereford cattle and ponies treated with permethrin

Efficacy of topical administration of prallethrin-permethrin-piperonyl butoxide (Bronco® Equine Fly Spray) for the treatment and control of flies and other nuisance insects of horses

Numerous biting and nuisance insects are a noted cause of discomfort and stress to horses. Pyrethrins and pyrethroids have been used for many years in numerous formulations for the control of insect pests in animals, humans and environment. There are, however, few studies reporting their field efficacy in horses. The aim of the present study was to evaluate the repellent activity of a spray formulation based on prallethrin and permethrin synergized with piperonyl butoxide (BRONCO® Equine Fly Spray, Farnam Companies, Inc., USA) against annoying and harmful insects for horses in field conditions. Nine horses of mixed breed were divided into 2 groups (treatment and control). Pre-treatment insect counts were compared to daily counts for 4 days post-treatment (pt). One minute after the administration of the product (day 0), all the horses were negative for the presence of insects. All counts up to the 6-h pt check remained negative for Hippobosca equina, tabanid flies and Simulium spp., showing 100% efficacy. This remained above 90% throughout the study. For the H. equina, the repellent efficacy remained > 99.7% for all 4 days pt, for tabanid flies > 93.3% and for Simulium spp. > 97.4%. The efficacy against Musca spp. decreased from 82.2% at day 0 to 62.2% at day 3. Treatment was well-tolerated. In conclusion, despite the low number of tested horses, Bronco® has demonstrated high insecticide and repellent efficacy and a good persistence, maintained for up to 4 days post-treatment, against the most common species of insects harmful for horses.

Effects of cattle on vector-borne disease risk to humans: A systematic review

Vector-borne pathogens (VBPs) causing vector-borne diseases (VBDs) can circulate among humans, domestic animals, and wildlife, with cattle in particular serving as an important source of exposure risk to humans. The close associations between humans and cattle can facilitate the transmission of numerous VBPs, impacting public health and economic security. Published studies demonstrate that cattle can influence human exposure risk positively, negatively, or have no effect. There is a critical need to synthesize the information in the scientific literature on this subject, in order to illuminate the various ecological mechanisms that can affect VBP exposure risk in humans. Therefore, the aim of this systematic review was to review the scientific literature, provide a synthesis of the possible effects of cattle on VBP risk to humans, and propose future directions for research. This study was performed according to the PRISMA 2020 extension guidelines for systematic review. After screening 470 peer-reviewed articles published between 1999-2019 using the databases Web of Science Core Collection, PubMed Central, CABI Global Health, and Google Scholar, and utilizing forward and backward search techniques, we identified 127 papers that met inclusion criteria. Results of the systematic review indicate that cattle can be beneficial or harmful to human health with respect to VBDs depending on vector and pathogen ecology and livestock management practices. Cattle can increase risk of exposure to infections spread by tsetse flies and ticks, followed by sandflies and mosquitoes, through a variety of mechanisms. However, cattle can have a protective effect when the vector prefers to feed on cattle instead of humans and when chemical control measures (e.g., acaricides/insecticides), semio-chemicals, and other integrated vector control measures are utilized in the community. We highlight that further research is needed to determine ways in which these mechanisms may be exploited to reduce VBD risk in humans.

Management Strategies for Reducing the Risk of Equines Contracting Vesicular Stomatitis Virus (VSV) in the Western United States

Vesicular stomatitis viruses (VSVs) cause a condition known as vesicular stomatitis (VS), which results in painful lesions in equines, cattle, swine, and camelids, and when transmitted to humans, can cause flu-like symptoms. When animal premises are affected by VS, they are subject to a quarantine. The equine industry more broadly may incur economic losses due to interruptions of animal trade and transportation to shows, competitions, and other events. Equine owners, barn managers, and veterinarians can take proactive measures to reduce the risk of equines contracting VS. To identify appropriate risk management strategies, it helps to understand which biting insects are capable of transmitting the virus to animals, and to identify these insect vectors' preferred habitats and behaviors. We make this area of science more accessible to equine owners, barn managers, and veterinarians, by (1) translating the most relevant scientific information about biting insect vectors of VSV and (2) identifying practical management strategies that might reduce the risk of equines contracting VSV from infectious biting insects or from other equines already infected with VSV. We address transmission risk at four different spatial scales-the animal, the barn/shelter, the barnyard/premises, and the surrounding environment/neighborhood-noting that a multiscale and spatially collaborative strategy may be needed to reduce the risk of VS.

Behavioral Inhibition of the House Fly (Diptera: Muscidae) When Exposed to Commercial Equine Fly Repellents

House flies can have negative consequences on the welfare of horses and other equids. Fly repellents in the form of on-animal sprays, wipes, or spot-ons are the most commonly used fly control method for horses. Many products are available, but repellent efficacy and duration of effectiveness may influence repellent choice by horse owners. A better understanding of the efficacy of common fly repellent products will help guide repellent selection to reduce fly pressure on horses. To evaluate commercially available repellents, house fly behavioral inhibition after application of three products marketed as natural (Ecovet, Equiderma, and Outsmart) and four with synthetic pyrethroids as active ingredients (Bronco, Endure, UltraShield, and Optiforce) was compared at 100, 50, and 25% concentration and at 15, 30, 60, 240, 1,440, and 2,880 min. Time and product were significant at all tested concentrations. The natural products performed as well as or better than the synthetic products at all dilutions and times. Ecovet in particular retained over 75% inhibition of flies for >1 d at the 100 and 50% concentrations. Differences were seen among products with pyrethroids, suggesting that formulation differences significantly affect efficacy. Cost and application suggestions are discussed, and these results will aid horse owners in selecting fly repellents to meet their individual needs.

Malaria vectors and their blood-meal sources in an area of high bed net ownership in the western Kenya highlands

Background

Blood-meal sources of malaria vectors affect their capacity to transmit the disease. Most efficient malaria vectors prefer human hosts. However, with increasing personal protection measures it becomes more difficult for them to find human hosts. Here recent malaria vector blood-meal sources in western Kenya highlands were investigated.

Methods

Adult mosquitoes resting indoors, outdoors and exiting through windows were collected in three study areas within the western Kenya highlands from June 2011 to June 2013. A census of people, livestock and of insecticide-treated nets was done per house. Mosquito blood-meal sources were determined as human, goat, bovine or chicken using enzyme-linked-immunosorbent assays.

Results

Most (86.3 %) households possessed at least one bed net, 57.2 % had domesticated animals and 83.6 % had people sharing houses with livestock at night. Most (94.9 %) unfed malaria vectors were caught exiting through windows. Overall, 53.1 % of Anopheles gambiae sensu stricto obtained blood-meals from humans, 26.5 % from goats and 18.4 % from bovines. Single blood-meal sources by An. gambiae s.s. from humans were 26.5 %, 8.2 % from bovines and 2.0 % from goats. Mixed blood-meal sources by An. gambiae s.s. identified included: 24.5 % human/goat, 10.2 % human/bovine, 8.2 % human/bovine/goat and also 8.2 % bovine/goat. One An. arabiensis mosquito obtained blood-meal only from humans.

Conclusion

An unusually high frequency of animal and mixed human-animal blood meals in the major malaria vector An. gambiae s.s. was revealed in the western Kenya highlands where bed net coverage is above the WHO target. The shift in blood-meal sources from humans to livestock is most likely the vectors’ response to increased bed net coverage and the close location of livestock frequently in the same house as people at night. Livestock-targeted interventions should be considered under these circumstances to address residual malaria transmission.

Controlling malaria using livestock-based interventions: a one health approach

Where malaria is transmitted by zoophilic vectors, two types of malaria control strategies have been proposed based on animals: using livestock to divert vector biting from people (zooprophylaxis) or as baits to attract vectors to insecticide sources (insecticide-treated livestock). Opposing findings have been obtained on malaria zooprophylaxis, and despite the success of an insecticide-treated livestock trial in Pakistan, where malaria vectors are highly zoophilic, its effectiveness is yet to be formally tested in Africa where vectors are more anthropophilic. This study aims to clarify the different effects of livestock on malaria and to understand under what circumstances livestock-based interventions could play a role in malaria control programmes. This was explored by developing a mathematical model and combining it with data from Pakistan and Ethiopia. Consistent with previous work, a zooprophylactic effect of untreated livestock is predicted in two situations: if vector population density does not increase with livestock introduction, or if livestock numbers and availability to vectors are sufficiently high such that the increase in vector density is counteracted by the diversion of bites from humans to animals. Although, as expected, insecticide-treatment of livestock is predicted to be more beneficial in settings with highly zoophilic vectors, like South Asia, we find that the intervention could also considerably decrease malaria transmission in regions with more anthropophilic vectors, like Anopheles arabiensis in Africa, under specific circumstances: high treatment coverage of the livestock population, using a product with stronger or longer lasting insecticidal effect than in the Pakistan trial, and with small (ideally null) repellency effect, or if increasing the attractiveness of treated livestock to malaria vectors. The results suggest these are the most appropriate conditions for field testing insecticide-treated livestock in an Africa region with moderately zoophilic vectors, where this intervention could contribute to the integrated control of malaria and livestock diseases.

Evaluation of mosquito responses to pyrethroid insecticides topically applied to sheep

A rise in the incidence of mosquito-transmitted Cache Valley virus (CVV) in lambs in 2011 prompted a study to evaluate on-animal pyrethroid insecticides to reduce mosquito attacks on sheep. Using enclosure traps for 1 night per wk for 6 wk, we compared engorgement rates of mosquitoes given the opportunity to feed on untreated sheep and sheep treated with 1 Python insecticide ear tag (containing 10% zeta-cypermethrin and 20% piperonyl butoxide) per animal or 2 synergized permethrin body spray treatments (containing 2.5% permethrin and 2.5% piperonyl butoxide). During the 6-wk study, 18,920 mosquitoes were collected in the animal-baited enclosure traps. Thirteen species were identified from these collections with the floodwater species Aedes increpitus and Ae. idahoensis making up 68% of the total. Potential CVV vector species, making up 25% of the samples, included Ae. vexans, Ae. dorsalis, Culex tarsalis, and Culiseta inornata. Traps baited with untreated sheep collected 9,701 mosquitoes with 65% of these engorged. Traps baited with sheep treated with Python ear tags or permethrin spray collected 4,034 and 4,555, respectively, with engorgement rates of 23% and 35%. Blood feeding on ear-tagged sheep was significantly reduced by as much as 90% compared to the untreated sheep, and protection lasted 4 wk or longer. Permethrin spray treatments were most effective within 24 h after application and provided better protection against Ae. dorsalis than the Python tag. Effectiveness of the permethrin spray diminished 1 wk after the 2nd application was made. The effect of these treatments appeared to be repellency because negligible mosquito mortality was observed at the time of collection. Further evaluation of these insecticides under conditions of natural exposure to a mosquito-borne pathogen is warranted.

United States Department of Agriculture-Agricultural Research Service research on veterinary pests

An overview of ARS research in the field of veterinary pests is presented. Results of research from the past three years on ticks, fire ants, nuisance flies, mosquitoes, sand flies and black flies, among others, are included. Where applicable, significance of research is discussed.