Progress 10/01/10 to 09/30/11
Outputs
OUTPUTS: Experiments were conducted to determine if the monoterpene geraniol was an effective contact repellent or spatial repellent for house flies and stable flies in a petri dish bioassay. Geraniol in water was applied to one half of a filter paper with 0, 1, 2, 3 and 4% solution. The opposing half of the filter paper was untreated. House and stable fly activity was restricted to the untreated portion of the filter paper. House flies were sensitive to 2 and 3% geraniol while stable flies were most sensitive to 1 and 2% geraniol. House flies and stable flies exposed to 4% and 3% geraniol were anesthetized, respectively. House flies (50%) became anesthetized after 160 minutes and 50% of the exposed stable flies were knocked down in 54 minutes. In a second choice experiment, female flies were allowed to select for oviposition substrates treated with or without geraniol at concentrations of 0, 1, 2, 3, and 4%. Flies were deterred from ovipositing on substrates treated with 4% geraniol. An 8 week study was performed to evaluate the movement of flies among facilities on a diversified farm housing dairy cattle, swine and beef cattle. The distance from the dairy to the swine facility was about 700m, and the distance from the swine unit to the beef facility was 500m. Fly traps equipped with house fly pheromone lures were placed at each location. One additional fly trap was placed half the distance between the dairy and swine unit and another half way to the beef unit. Laboratory reared house flies, 1000 each, were marked with day glow colored powders, green (dairy), orange (swine), pink (beef). Marked flies were released weekly at designated locations. Collections were made 24 and 72 hours post-release. About 1-2% of the released flies were captured in the traps. The trap at the beef facility recovered the most marked house flies, although the dairy produced the most unmarked flies. Fly movement from the beef to the swine unit was evident, few flies moved from the swine unit to the beef unit. No flies moved from the dairy to the swine or beef units. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Most marked flies remained at or near the release site where natural food supplies were abundant. Some flies, however, dispersed from the site of release. These experiments illustrate the potential for at least some house flies to move between facilities on a diversified farm. This poses a potential biosecurity risk for the movement of disease agents from animal to animal regardless of species. Limiting fly access to animals is difficult. Repellents may reduce exposure to flies by limiting access to treated facilities. The monoterpene, geraniol, is a generally regarded as safe compound that can be used as an insect repellent on animals or as a premises treatment. This plant derived material meets the standards for organic certification. When used at concentrations of less than 3%, house flies and stable flies avoid contact with treated surfaces. At higher concentrations flies were subject to knockdown and in some instances death. These studies illustrate that geraniol may have utility as a fly repellent in livestock facilities. Limiting exposures to flies, reduces the potential for disease transmission among animals on diversified farms.
Publications
- No publications reported this period
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Progress 10/01/09 to 09/30/10
Outputs
OUTPUTS: Enteric bacteria associated with flies in swine production. Arthropods, especially the house fly very likely contribute to the transmission and maintenance of bacteria associated with foodborne illnesses in the preharvest interval. House fies have been shown to transmit Campylobacter experimentally and half of all flies captured near poultry houses containing naturally infected chickens were positive for the bacterium. The house fly is the predominant pest in the southeastern US. Specifically, these highly mobile insects are capable of disseminating foodborne bacteria within and between livestock facilities. We have been monitoring house flies and other pests associated with swine production for the prevalence of enteric bacteria that could cause foodborne illness in humans From July 14th to October 29th 15 sets of pooled fly samples were analyzed. Flies were pooled into 10 flies per sample and received one of four treatments to determine location of bacteria on the fly (internal or external): surface sterilized and crushed, surface sterilized and intact, non-surface sterilized and crushed, or non-surface sterilized and intact. All but two samples were house flies, one pool sample was Drosophila repleta (vinegar flies) and one pool was stable flies. Flies were tested for Campylobacter and Salmonella (see page below for detailed isolation protocol). Campylobacter prevalence was 6.5% (7 positive/107 collected). In July and August, positive samples originated from barns 4 and 5, containing finishing pigs. When these hogs when to slaughter in September, sows were moved into barns 1, 2, 3, 4. In September and October, positive samples came from barns 1 and 2 containing sows and farrowing sows with piglets. All positive samples were non-surface sterilized and crushed. Salmonella prevalence was almost half that of Campylobacter at 2.9% (3 positive/103 collected). Two of the three positive Salmonella samples originated from barn 2, containing farrowing sows. The remaining sample came from barn 5, containing finishing pigs. All positive samples came from non-surface sterilized and crushed. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
These results indicate that house flies collected from swine barns are carrying the bacterium Campylobactor. Salmonella was rarely collected from the flies. These data illustrate that house flies may disseminate bacteria from within farm and likely are a source of contamination regardless of biosecurity efforts between farms. Furthermore these experiments suggest that house flies may function as a means to spread pathogenic bacteria between vertebrate hosts, i.e. swine to cattle or swine to poultry. This is particularly a concern for diversified farms that raise a variety of animals. Traditionally such farms tend to use few antibiotics and are considered "antibiotic free". Future studies are going to focus on the potential role of house flies in the dissemination of antibiotic or antimicrobial resistant bacteria among antibiotic free swine herds.
Publications
- No publications reported this period
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: The overall goal of this research project is to document and demonstrate integrated pest management approaches to minimize the severity of filth fly infestation in a dry-bedding waste management system. Objective 1. Characterization of the dynamics of filth fly breeding and beneficial insect activity in the hoop barn management system. Insects were monitored during the summer months. The insect populations are comprised of, in order of abundance, house flies, vinegar flies, stable flies, dump flies, blow flies and flesh flies. Beneficial arthropods were dominated by parasitic mites, Macrochelidae and the parasitoids, Muscidifurax raptor and Spalangia cameroni. Occasionally natural epizootics of the entomopathogenic fungus, Entomophthora muscae developed in the house fly population. Low levels of two entomophathogenic fungi, Beauveria bassiana and Metarhizium anosopliae, were identified from field collected house flies. Objective 2. Define the optimal dose formulation to maximize fly repellency in a swine barn. Laboratory studies employing geraniol and tridecanone repellents were performed to establish a dose response for tactile repellency. A tactile repellency assay was developed using repellent treated filter paper discs. Discs were cut into halves; one half was treated with the test repellent and the other with water. Test concentrations were 1, 3, 6, 8, 14 and 20% geraniol prepared in water or tridecanone prepared in ethanol. Test material or carrier control was allowed to dry on the surface of the filter papers for 3 hours then placed in petri dishes, treatment on one side and control on the other. Three species of flies were tested, house fly, stable fly and the lesser house fly. Five flies were anesthetized with carbon dioxide and placed in the center of the plate to recover. The location of the flies was determined visually and by counting the number of fly specks on the treated and untreated filter papers. All three species of flies were repelled from the treated surfaces at 20% tridecanone. House flies, stable flies and lesser house flies were least sensitive to tridecanone. Flies were most sensitive to 3% geraniol. Objective 3. Evaluate the push-pull strategy using plant derived insect repellents and the entomopathogenic fungus, Beauveria bassiana, in deep-bedded swine production facilities. Under this objective we conducted a mark and recapture study to determine if flies moved from barn to barn and if marked flies could be repelled from a treated barn and lured into an untreated barn. House flies (n=2000) were marked with colored fluorescent dyes and released in a single barn. Fly movement was monitored with sticky ribbons and traps placed inside and outside the barns. After 1 week the flies were examined with a black light and the numbers of marked and unmarked flies recorded. About 1% of the marked flies moved from the release barn to another. Currently underway, marked flies were released in one barn and allowed to acclimate. The barn has been treated with 1% geraniol to determine if flies can be pushed into untreated barns. Results will be presented in the next report. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Outcomes The push-pull strategy is the manipulation of the pest by applying pressures to induce behavioral changes that result in less crop damage. Conceptually a variety of compounds, including repellents, oviposition deterrents, and antifeedants are used to "push" the pest away from the crop. Other agents pull the pests toward an unsuitable or trap crop using lures such as pheromones, attractants, and feeding stimulants. In this study we are using repellents geraniol and tridecanone to induce change in fly behaviors resulting in reduced fly populations in straw bedded swine houses. In this study we have characterized the arthropod community within deep bedded hoop houses that have received no insecticide inputs. House flies are the most abundant pest species present. The vinegar fly, Drosophila repleta is a common fly in conventional and deep bedded swine production. Stable flies are common outside the swine houses and enter the hoop barns to feed on the pigs. Flies are a present throughout the warm months when sufficient bedding and manure supports the immature population. Abundant parasitoids and predatory mites help keep the fly population low but have not below pest threshold levels. Geraniol at 3% concentration effectively repelled flies in laboratory assays. Further studies will be designed to refine the tactile and spatial repellency of both geraniol and tridecanone. Mark and recapture studies are currently underway to demonstrate the push-pull strategy in fly management. Isolates of Beauveria bassiana will be evaluated for mass production and incorporation into the study.
Publications
- No publications reported this period
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Porcine Reproductive and Respiratory Syndrome (PRRS) is a globally significant swine disease. The virus replicates in macrophages of infected pigs resulting in pneumonia and late-term abortions in sows. The link between outbreaks on farms within an area despite biosecurity measures remains unclear. Mosquitoes and house flies were implicated as possible mechanical vectors of the disease in Minnesota. Since the stable fly also frequents swine barns we investigated the vectorial potential of stable flies in the transmission of PRRSV under laboratory conditions. Our first objective was to investigate the potential of stable flies to directly transmit PRRSV from pig to pig. Second, we investigated the ability of stable flies to acquire PRRS virus through a bloodmeal and the fate of the virus in the fly digestive tract. Third, we examined the fate of PRRS virus in the hemolymph of the flies following a midgut barrier bypass operation. Objective 1: Stable flies were collected around PRRS-negative boar stud barns in North Carolina and tested for presence of the virus. Significantly more stable flies were collected on traps placed near the exhaust fan of the close-sided buildings, indicating blood seeking flies are attracted by olfactory cues. None of the flies collected were positive for PRRS virus. We assessed transmission of the virus through an infective bite by feeding laboratory reared stable flies on blood containing virus and transferring them to naive pigs for subsequent bloodmeals. Stable flies did not transmit virus to naive pigs. The volume of blood contained in the closed mouthparts of the stable fly was insufficient to deliver an infective dose of the virus. Objective 2: Stable flies were fed blood containing either modified live vaccine virus, chemically inactivated virus or no virus. Groups of 30 flies were sampled at random over a period of 96h. We used virus isolation and real-time PCR to detect and quantify the virus. Stable flies acquired PRRS virus from the bloodmeal and the amount of virus in the flies declined with time, indicating the virus does not replicate in fly digestive tissues. We were unable to differentiate between active and inactive virus with PCR, but active virus was recovered from the flies up to 24h post-feeding using cell culture. Although stable flies are unlikely vectors of PRRS virus, they may spread the virus by contaminating the environment. Objective 3: We further examine the fate of PRRS virus in the hemolymph of the flies following a midgut barrier bypass. Adult stable flies were intrathoracically inoculated with a PRRS virus solution and the amount of virus present in the flies was monitored for 10 days using quantitative real-time PCR. The detectable quantities of virus over time followed an exponential decay curve. Detectable virus quantities never fell below 5 logs in the stable fly hemolymph. Virus levels were 9,500 times greater in the hemolymph when compared to detected levels in the digestive tract. Further study to test the saliva of inoculated stable flies for presence of the virus is needed to determine if PRRS virus can enter and escape stable fly salivary glands. PARTICIPANTS: Dr. Butch Baker, DVM, Iowa State University, College of Veterinary Medicine Dr. Glen Almond, DVM, North Carolina State University, College of Veterinary Medicine Dr. Isabel Gimeno, DVM, North Carolina State University, College of Veterinary Medicine Dr. Adalberto Perez de Leon, Ph.D., DVM, USDA ARS Livestock Insects Lab, Kerrville, TX TARGET AUDIENCES: Veterinary Entomologists Vector Biologists Swine Industry Veterinary Services PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
In direct pig to pig transmission experiments stable flies failed to cause PRRSV infection in naive pigs. Measurable quantities of PRRSV on the fly mouthparts were below detectable levels 1 hour post exposure. We conclude that the volume of blood contained in the closed mouthparts of the stable fly is insufficient to deliver an infective dose of the virus. Stable flies acquired PRRS virus by feeding on an infective bloodmeal. Active PRRS virus was recovered from the flies up to 24h post-feeding using cell culture. Measurable quantities of virus within the flies declined with time. Ours studies indicate that PRRS virus does not replicate in fly digestive tissues. Although stable flies are unlikely vectors of PRRS virus, they may spread the virus by contaminating the environment. The midgut barrier is the primary line of defense against infection in bloodfeeding insects. Occasionally the midgut barrier may be compromised, allowing the pathogen to enter the insect's circulatory system and increasing the potential of the insect to transmit disease. Adult stable fly bodies were inoculated with a PRRS virus solution and the amount of virus present in the flies was monitored for 10 days. Unlike the previous experiment, detectable virus quantities never fell below 5 logs of virus in the stable fly. Detectible virus levels were 9,500 times greater in the fly when compared to detectible levels in the digestive tract. These experiments indicate the stable fly is able to acquire PRRS virus by taking an infective bloodmeal. The stable fly not a likely vector of PRRS virus in swine under natural conditions. Stable flies support the virus for longer time periods if the midgut barrier is compromised. Infection of stable fly salivary glands with PRRSV has not been resolved.
Publications
- Rochon, K. 2008. Vector Potential of Stable Flies (Stomoxys calcitrans) for the Rransmission of Porcine Reproductive and Respiratory Syndrome Virus. Ph.D. Dissertation. Department of Entomology, North Carolina State University, Raleigh, NC 27695
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