Fly Management in Animal Agriculture Systems and Impacts on Animal Health and Food Safety

<p>NON-TECHNICAL SUMMARY:<br/> Federal funding priorities are focused on major issues of national concern, climate change, food safety, food security, biofuels, and obesity. Entomologists play a key and vital role in helping to solve many of these national concerns by researching the potential impact of climate change on insect populations and how these changes can threaten the health and well-being of humans and animals, and compromise the nations safe and secure food supply. Few insects are more influenced by anthropogenic effects than nuisance and pest flies; the house fly, stable fly, horn fly, face fly and blow flies. There is a significant body of literature on the biology and economic impact of these pests but this multidisciplinary project examines closely predictive models influencing pest distribution in light of climate change, the effects of the microbial
community of pest populations, and the dispersal of pathogenic microorganisms that compromise a safe and secure food supply. Advances developed in the course of this project will lead to the development of new and innovative pest management technologies to mitigate these threats. Biting and nuisance flies are among the most important pests in livestock and poultry production systems. These flies are responsible for damage and control costs in excess of a billion dollars per year in the United States. In addition to the direct damage these flies inflict upon livestock, their presence as a byproduct of confined livestock and poultry operations has been repeatedly cited as a nuisance, especially when flies enter the vicinity of human habitations and urban environments. Law suits, zoning limitations and animosity between farmers and home owners have resulted. In spite of their ubiquitous
presence, importance as pests, and association with diseases of humans and livestock, our knowledge of the biology of these species is seriously wanting and available control technologies remain inadequate. The recent sequencing of the house fly genome (underway), and future sequencing of the stable fly genome (planned) offer great potential for the identification of new opportunities for managing these pests. House flies are considered to be the #1 nuisance pest associated with dairy and other confined animal operations. House flies are capable of carrying more than 65 disease organisms that affect humans and animals, such as the virulent Escherichia coli strain O157:H7. In poultry production, house flies can transmit Salmonella among flocks; and the spotting of eggs with fly specks may reduce the eggs' market value. Stable are among the most serious pests of cattle worldwide. With
their painful bites, they can reduce weight gains of cattle on finishing rations up to 20%. The total impact to U.S. cattle industries is estimated to exceed $2 billion dollars annually. Given the economic importance of nuisance and biting flies, control of their populations is critically important. For decades insecticides have provided economical control of these pests. However, the evolution of insecticide resistance compromises the control achieved in many locations around the USA. Stable flies develop as maggots in a wide array of decomposing organic matter, including soiled animal bedding and soiled feed debris that accumulates wherever cattle are confined. Populations build exponentially by continuous reproduction from spring to fall in northern temperate localities. Dairy farm surveys indicate calf hutch bedding is a prominent source of stable flies around dairies, and choice of
bedding material can minimize stable fly production. More recently, it has also become apparent that feed debris and manure that accumulate during winter are important sources of stable flies, especially where overwintered debris piles remain intact into the following summer. The face fly is the primary pest of pastured cattle in most state north of the 35th parallel. Adult face flies overwinter in attics and out-buildings and colonize cattle in the spring. The face fly feeds on lachrymal and mucosal secretions of the eyes and nose of cattle. Gravid flies lay eggs exclusively in fresh cattle dung pats, and the life cycle can be completed in as little as 14 days. When face flies are abundant, cattle change grazing habits, which often results in poor utilization of pasture. In addition to the annoyance and irritation associated with its feeding habits, the face fly is the primary means of
transmission of Moraxella bovis, the causative agent of infectious bovine keratoconjunctivitis (IBK), also known as pinkeye. Face fly infestations were estimated to cause annual losses of more than $53 million. Action threshold levels of 10-15 flies per face were established to reduce the spread of pinkeye and maximize animal comfort. In the northeast face fly numbers often exceed 100 flies per face. The horn fly is an obligate blood-sucking parasite of cattle and is considered a serious pest of pastured cattle in US. Horn fly feeding annoys cattle, alters their grazing habits, and decreases both milk production and weight gains. Horn fly numbers as high as 10,000 per animal have been reported and they feed 10 to 12 times per day. Horn flies oviposit exclusively in fresh dung, and they do so immediately after it has been deposited. The fly can complete development in 9-12 days, with 50%
adult survival at 5 weeks. Horn flies diapause beneath dung pats during the winter months. Horn fly control leads to increased milk production and calf growth. Unlike other kinds of flies that just visit cattle for brief moments, adult horn flies reside on their host animals, which makes then especially vulnerable to control. Organic dairy farmers rely on essential oil repellents to alleviate horn fly problems, but success of these products is limited. Horn flies have been incriminated in the transmission of bovine mastitis, also known as summer mastitis. In NC, 53% of horn flies collected from cattle were positive for S. aureus, and 39% of the cows were positive for the same genotype found in the flies. In 2003, the Northeastern IPM Center Livestock and Field Crop working group created a list of prioritized needs. The group indicated that the "development of new integrated management of
key pests of livestock and poultry in confined and pasture settings" was a top priority with specific reference to "stable fly breeding and migration in pasture systems" and "fly control methods for pasture and feedlot situations." Ten of the working group's 17 assessed needs and seven of the top 10 directly referred to muscid flies, including house flies, stable flies, and face flies as top priorities. The objectives of the current proposal address 10 of the 17 needs. Coordinated extension of the research outcomes derived from this proposal to stakeholders will address 2 additional priorities of this working group. Successful completion of this project will provide a better understanding of the interactions between livestock production systems and the life cycles of pestiferous flies. Exploitation of these interactions will provide economically feasible and environmentally friendly
technology for reducing the impact of flies on livestock production and human health. The project will provide quantitative data to analyze fly borne spread of pathogens from animal production systems into the urban environment. The project will develop new control technologies for biting and nuisance flies and will assess the fly resistance to insecticides that are currently available or under development. New technological innovations and comprehensive pest management information will be disseminated to producers through a multistate coordinated effort to provide the broadest reach for project outcomes thereby increasing the health and quality of livestock and reducing the economic impact of these pest flies.
<p>APPROACH:<br/> A nationwide survey for stable fly resistance to permethrin will be conducted. Treated jars will be shipped to collaborating scientists and results will be compiled by the University of Florida. Flies that survive the bioassay will be frozen and archived for evaluation of Vssc mutations using molecular techniques. Although a mutation in the stable fly Vssc has been described, its absence from field collections is probable and would support the presence of other Vssc mutations or other mechanisms of resistance unrelated to the target site. These specimens would enable additional screening. Resistance to benzylphenyl urea and triazine compounds has not been reported for stable fly. Therefore, we will use house fly as a model to evaluate cross-resistance and synergy between these compounds. Cyromazine resistant house fly colonies (3-4) will be established by
collecting house flies from poultry operations with a history of using Larvadex (Bloomcamp et al. 1987). Susceptible colonies will be acquired from institutions maintaining susceptible house fly colonies. Bioassays will be conducted to establish LC50 values for cyromazine and novaluron for each colony. If novaluron resistance is observed in cyromazine resistant colonies, they will be crossed with susceptible colonies and progeny independently selected for cyromazine and novaluron resistance. Lines will be evaluated for susceptibility to both insecticides after selection. Synergistic effects of cyromazine, novaluron, and pyriproxyfen on stable fly and house fly will be evaluated as well. Assessment of insecticide resistance in horn flies collected from beef and dairy herds and stable flies from dairy, beef and equine farms will include field surveys using multiple existing registered
chemistries. Up to 10 farms will be surveyed and their resistance to insecticides in the pyrethroid (Type I and II) and organophosphate classes will be determined, with other classes added as available. Genetic profiling of for acetylcholinesterase (Ace) and kdr-type mutations (Vssc) as well as other biochemical assays will be carried out on these same fly populations. This study provides an opportunity to identify stable fly populations that may exhibit OP-resistance, facilitating identification of mutations occurring within the stable fly acetylcholinesterase gene (ScAChE) that associate with the OP-resistant phenotype. Sequencing of the house fly and stable fly genomes also offers the potential for rapid identification of the mutations responsible for resistance. Identification of the alleles responsible for resistance allows for detailed studies of the evolution of resistance that
are not possible with bioassays. We propose to use high-throughput Illumina sequencing of transcripts between resistant and susceptible house fly strains to rapidly identify the basis of resistance. This would be done for both spinosad and imidacloprid resistant strains. Given the importance of olfaction to stable fly development (host location, oviposition), a more complete understanding of the genes involved in the olfactory pathway provides a means to more rapidly screen attractant/repellent compounds in vitro to evaluate possible use in field settings. Transcriptome data has provided some insight into stable fly olfactory genes (Olafson et al. 2011; Olafson et al., 2013); however, availability of a genome sequence would greatly strengthen this base, especially with respect to identifying the repertoire of ligand-selective odorant receptors that are known to be highly divergent within
insects. Once identified, these receptors will be isolated and used in vitro for screening compounds of interest.