Bacterial Communities of House Flies from Dairy Farms Highlight Their Role as Reservoirs, Disseminators, and Sentinels of Microbial Threats to Human and Animal Health.

Adult house flies (Musca domestica L.) inhabiting dairy farms not only are nuisance pests but also harbor and disseminate bacteria. We examined the bacterial community composition, diversity, environmental sources, and prevalence in individual adult female house flies and cattle manure samples collected monthly from Florida, North Carolina, and Tennessee dairy farms between May and August 2021. Individual house flies carried diverse bacterial communities, encompassing all bacterial taxa (100%) identified across manure samples, and additional species likely acquired from the animals. Bacterial community assemblage in house flies and manure samples within farms varied by month. Some taxa were differentially associated with either house flies (Corynebacterium, Acinetobacter, and Staphylococcus) or manure samples (Treponema, Succinivibrio, and Clostridia). House fly bacterial communities mostly contained specialist species originating from manure, with several taxa (Escherichia, Corynebacterium, Turicibacter) being potential pathogens of livestock and humans. These findings further support the role of house flies as carriers of cattle-associated bacteria, including pathogens, and their potential for disseminating these microbes among cattle and to neighboring environments. Since their bacterial communities provide a snapshot of their surrounding environment, house flies also serve as effective sentinels in xenosurveillance strategies.

Microbiome of Invasive Tick Species Haemaphysalis Longicornis in North Carolina, USA.

Ticks are one of the most important vectors of human and animal disease worldwide. In addition to pathogens, ticks carry a diverse microbiota of symbiotic and commensal microorganisms. In this study, we used next-generation sequencing (NGS) to survey the microbiomes of Haemaphysalis longicornis (Acari: Ixodidae) at different life stages collected from field populations in North Carolina (NC), USA. Sequence analyses were performed using QIIME2 with the DADA2 plugin and taxonomic assignments using the Greengenes database. Following quality filtering and rarefaction, the bacterial DNA sequences were assigned to 4795 amplicon sequence variants (ASVs) in 105 ticks. A core microbiome of H. longicornis was conserved across all ticks analyzed, and included bacterial taxa: Coxiella, Sphingomonas, Staphylococcus, Acinetobacter, Pseudomonas, Sphingomonadaceae, Actinomycetales, and Sphingobium. Less abundant bacterial taxa, including Rickettsia and Aeromonas, were also identified in some ticks. We discovered some ASVs that are associated with human and animal infections among the identified bacteria. Alpha diversity metrics revealed significant differences in bacterial diversity between life stages. Beta diversity metrics also revealed that bacterial communities across the three life stages were significantly different, suggesting dramatic changes in the microbiome as ticks mature. Based on these results, additional investigation is necessary to determine the significance of the Haemaphysalis longicornis microbiome for animal and human health.

Using Visual and Digital Imagery to Quantify Horn Fly (Diptera: Muscidae) Densities.

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.

Field trials of fatty acids and geraniol applied to cattle for suppression of horn flies, Haematobia irritans (Diptera: Muscidae), with observations on fly defensive behaviors.

Adult horn fly populations were tracked on cattle for 2-week periods before, during and after multiple treatments (every 3-4days) with two repellents in a mineral oil carrier. Cattle were sprayed four times in a two-week period either with 2% geraniol (125ml/cow) or a 15% mixture of short chain fatty acids (C8-C9-C10)(250ml/cow), and there were untreated control cattle. Trials were conducted in California and North Carolina for 3 summers. Short-term fly counts (same day) on treated cattle were reduced by 61-99%, depending on material and trial, and the fatty acid mixture provided better control than geraniol. Horn fly counts were suppressed for 1-3 d and rebounded somewhat after both treatments. Consecutive treatments showed evidence of persistent impact in California where herds were more isolated. Rebounds to pre-treatment levels 3-4 d after treatment occurred more often in North Carolina, where other infested cattle were closer to treated herds. By 3-4 d post-treatment, horn flies were reduced by 29-61% in California and 0-83% in North Carolina, relative to pre-treatment. Background behavior frequencies were assessed from hundreds of counts on untreated, infested California cattle, where horn flies were the only abundant biting fly. Behavior averages were 16.5 tail flicks, 7.6 skin twitches, 1.2 head throws, or 0.2 leg stamps per 2min observation period. At horn fly densities from about 200 to more than 1000 flies per animal (moderate to high numbers), fly defensive behaviors on control cattle were poorly related (or unrelated) to fly numbers. Immediately after repellent application, however, flies were almost absent and behavior frequencies dropped distinctly. Cattle fly defensive behaviors therefore seem to be quite sensitive to low (less than 100 flies/animal) horn fly densities, and behaviors would be a poor quantitative tool to track fly stress at moderate densities and above. Both geraniol and the fatty acids show promise for horn fly control, especially in organic agriculture. Treatments at 1-2 d intervals probably would keep infestations below the economic threshold (200 flies/cow).

Effects of the insect growth regulator, methoprene, on Onthophagus taurus (Coleoptera: Scarabaeidae).

A bioassay was conducted to determine the impact of methoprene, an insect growth regulator (IGR), on fecundity, larval survival, and size of progeny for Onthophagus taurus Schreber. Adult O. taurus dung beetles were offered methoprene-treated manure in three to five replications each at concentrations of 0.08, 0.45, and 4.5 ppm, respectively. An additional group of adult beetles was immersed in a methoprene-water solution and allowed to reproduce in containers with untreated manure. Data from all treatment groups were compared with untreated control groups. Methoprene did not seem to hinder brood production at 0.45 ppm. Survival of O. taurus was not affected by methoprene-treated manure at 0.08 ppm or when parent beetles were immersed in methoprene-water solution. However, progeny survival was significantly reduced on manure treated with methoprene at 4.5 ppm. Mean pronotal width of O. taurus progeny was significantly smaller in beetles fed methoprene-treated manure (4.5 ppm). The low dose of 0.08 ppm did not affect pronotal widths nor did topical application of methoprene to adults affect pronotal widths in resulting offspring. Although some adverse effects of methoprene were observed at higher concentrations, use of methoprene at concentrations of 0.08 ppm as part of a horn fly control program likely would not greatly affect populations of O. taurus, the most common paracoprid dung beetle in North Carolina.

Experimental evaluation of Musca domestica (Diptera: Muscidae) as a vector of Newcastle disease virus.

House flies, Musca domestica L. (Diptera: Muscidae), were examined for their ability to harbor and transmit Newcastle disease virus (family Paramyxoviridae, genus Avulavirus, NDV) by using a mesogenic NDV strain. Laboratory-reared flies were experimentally exposed to NDV (Roakin strain) by allowing flies to imbibe an inoculum consisting of chicken embryo-propagated virus. NDV was detected in dissected crops and intestinal tissues from exposed flies for up to 96 and 24 h postexposure, respectively; no virus was detected in crops and intestines of sham-exposed flies. The potential of the house fly to directly transmit NDV to live chickens was examined by placing 14-d-old chickens in contact with NDV-exposed house flies 2 h after flies consumed NDV inoculum. NDV-exposed house flies contained approximately 10(4) 50% infectious doses (ID50) per fly, but no transmission of NDV was observed in chickens placed in contact with exposed flies at densities as high as 25 flies per bird. Subsequent dose-response studies demonstrated that oral exposure, the most likely route for fly-to-chicken transmission, required an NDV (Roakin) dose > or =10(6) ID50. These results indicate that house flies are capable of harboring NDV (Roakin) but that they are poor vectors of the virus because they carry an insufficient virus titer to cause infection.

Lesser mealworm (Coleoptera: Tenebrionidae) emergence after mechanical incorporation of poultry litter into field soils.

Lesser mealworm, Alphitobius diaperinus (Panzer), emergence from North Carolina field soils was evaluated in a controlled experiment simulating land application of turkey litter and again in field studies. Adult lesser mealworms were buried in central North Carolina Cecil red clay at depths of 0, 8, 15, 23, and 30 cm and the beetles emerging from the soil counted 1, 3, 7, 10, 13, 17, 21, 24, and 28 d after burial. Beetles emerged from all depths and differences among depths were not significant. Beetles survived at least 28 d buried in the soil at depths < or =30 cm. In seasonal field studies, lesser mealworm emergence from clay soil with poultry litter incorporated by disk, mulch and plow was compared with emergence from plots with no incorporation. Incorporation significantly reduced beetle emergence when poultry litter containing large numbers of beetles was applied to clay field soils during the summer (F = 3.45; df = 3, 143; P = 0.018). Although mechanical incorporation of poultry litter reduced beetle emergence relative to the control, greatest reductions were seen in plowed treatments. Beetle activity was reduced after land application of litter during colder months. Generally, lesser mealworm emergence decreased with time and few beetles emerged from the soil 28 d after litter was applied. Similarly, mechanical incorporation of poultry litter into sandy soils reduced beetle emergence (F = 4.06; df = 3, 143; P < 0.008). In sandy soils typical of eastern North Carolina, disk and plow treatments significantly reduced beetle emergence compared with control.

Water solutions of boric acid and sugar for management of German cockroach populations in livestock production systems.

Pest management in confinement swine production relies primarily on calendar-based applications of broad-spectrum insecticides. However, regulatory restrictions imposed by the U.S. Food Quality Protection Act of 1996, the large financial obligation of pesticide registration, and development of insecticide resistance have led to a renewed search for alternative control methods. Boric acid dust has long served as an insecticide in urban pest management and has been shown an effective alternative for use in sensitive environments such as swine production. However, dust formulations are difficult to apply and require specialized equipment. The purpose of this study was to evaluate the efficacy of liquid baits containing boric acid for the control of German cockroaches in a commercial swine nursery. Bait, consisting of 1 or 2% boric acid and 0.5 M sucrose, was deployed in 21 bait delivery tubes per room. Results of a 2-yr study showed significant reductions in cockroach populations. When baits were withdrawn in the summer, the cockroach population increased significantly faster than when the baits were removed during the winter. These data indicate that liquid formulations of boric acid effectively reduce the burden of cockroach infestation in swine production. This approach should have applications in structures in other urban and agricultural environments.

Mechanical transmission of turkey coronavirus by domestic houseflies (Musca domestica Linnaeaus).

Domestic houseflies (Musca domestica Linnaeaus) were examined for their ability to harbor and transmit turkey coronavirus (TCV). Laboratory-reared flies were experimentally exposed to TCV by allowing flies to imbibe an inoculum comprised of turkey embryo-propagated virus (NC95 strain). TCV was detected in dissected crops from exposed flies for up to 9 hr postexposure; no virus was detected in crops of sham-exposed flies. TCV was not detected in dissected intestinal tissues collected from exposed or sham-exposed flies at any time postexposure. The potential of the housefly to directly transmit TCV to live turkey poults was examined by placing 7-day-old turkey poults in contact with TCV-exposed houseflies 3 hr after flies consumed TCV inoculum. TCV infection was detected in turkeys placed in contact with TCV-exposed flies at densities as low as one fly/bird (TCV antigens detected at 3 days post fly contact in tissues of 3/12 turkeys); however, increased rates of infection were observed with higher fly densities (TCV antigens detected in 9/12 turkeys after contact with 10 flies/bird). This study demonstrates the potential of the housefly to serve as a mechanical vector of TCV.