Selection for, and characterization of, fluralaner resistance in the house fly, Musca domestica.

House flies, Musca domestica (L), are the mechanical vector of >100 human and animal pathogens, including those that are antibiotic-resistant. Given that house flies are associated closely with human and livestock activity, they present medical and veterinary health concerns. Although there are numerous strategies for control of house fly populations, chemical control has been favored in many facilities. Products with pyrethroid active ingredients have been used predominantly for >35 years in space sprays. As a result, strong selection for pyrethroid resistance has led to reduced control of many populations. Reliance on a limited number of insecticides for decades has created fly control problems necessitating the discovery and formulation of new control chemistries. Fluralaner is a relatively new insecticide and acaricide (first reported in 2010), belonging to the isoxazoline class. These insecticides target the glutamate- and gamma-aminobutyric acid-gated (GABA) chloride channels, which is a different mode of action from other insecticides used against house flies. Although is it not currently registered for house fly control in the United States, previous work has shown that fluralaner is highly toxic to house flies and that there was limited cross-resistance found in laboratory strains having high levels of resistance to other insecticides. Herein, we characterized the time and age dependency of fluralaner toxicity, detected cross-resistance in populations from across the United States, and selected a highly resistant (>11,000-fold) house fly strain. We found that the fluralaner LD50 of 18-24 h old flies was 2-fold higher than for 5-6 d old flies. This appears to be due to more rapid penetration of fluralaner into the 5-6 d old flies. Fluralaner resistance was inherited as an intermediate to incompletely dominant trait and was mapped to chromosomes 5 and 3. Resistance could be suppressed to 7-fold with piperonyl butoxide, suggesting that cytochrome P450 (CYP)-mediated detoxification was a major mechanism of resistance. Decreased penetration was also demonstrated as a mechanism of resistance. The utility of fluralaner for house fly control is discussed.

Thrombin as a Potential Proxy to Select for Horn Fly Abundance in Beef Cattle.

Horn flies are a major nuisance to cattle and induce significant economic losses. Fly abundance varies within and across breeds and genetic analyses have shown sufficient genetic variation to permit selection. A major bottleneck for selecting against horn fly abundance is the complexity of measuring fly attraction phenotypes. Easy-to-measure proxy phenotypes could be an attractive option to indirectly estimate fly abundance. In the current study, thrombin was investigated as a potential proxy to assess fly abundance. Fly counts and blood samples were collected on 355 cows. Pearson correlation between subjective fly count and thrombin was -0.13, indicating a decrease in fly abundance with the increase in thrombin concentration. When thrombin was discretized into three classes, there was a 22% difference in fly count between the top and bottom classes. Heritability estimates of thrombin were 0.38 and 0.39 using linear and threshold models, respectively. The correlation between estimated thrombin breeding values and fly count was around -0.18. There was a noticeably lower density of high fly counts among animals with high breeding values for thrombin. These results indicate that thrombin could be used in combination with other biological factors to estimate fly abundance and as a proxy for selection against fly abundance.

A Review of Alternative Controls for House Flies.

House flies are the most prevalent synanthropic pest worldwide. Although they seldom reproduce in homes, they invade buildings, cause annoyance, and carry pathogens. Urban pest management personnel are limited in their ability to locate and manage larval habitats, so most house fly management in urban settings focuses on adult fly suppression. Sanitation is probably the most critical component, eliminating odors that attract flies. Source reduction applies where larval habitats can be identified and eliminated. Exclusion involves keeping flies out of structures. Despite all efforts, flies will manage to enter the human environment, so exclusion includes air curtains, fans, screened windows, and doors. Ultraviolet light traps attract and immobilize, while window traps entice flies into devices that entrap them. Sticky tubes and ribbons rely on flies' inclination to land on vertical lines to entangle them in glue. Even low-tech fly swatters can play significant roles in eliminating individual flies. Timed-release aerosol pyrethrin dispensers can be effective against flies confined in enclosed spaces. Toxic baits have limited use in urban settings. Chemical suppression remains a critical component of fly IPM, essential in situations requiring immediate fly elimination.

Genetic Structure of Northern Fowl Mite (Mesostigmata: Macronyssidae) Populations Among Layer Chicken Flocks and Local House Sparrows (Passeriformes: Passeridae).

The northern fowl mite (NFM) Ornithonyssus sylviarum Canestrini and Fanzago is a blood-feeding ectoparasite found on many wild bird species and is a pest of poultry in the United States. It is unknown where NFM infestations of poultry originate, which has made it difficult to establish preventative biosecurity or effective control. We used microsatellite markers to evaluate genetic variation within and among NFM populations to determine routes of introduction onto farms and long-term persistence. We compared NFM from flocks of chickens (Gallus gallus) on different farms in California, Washington, and Georgia, and we compared NFM collected over a 5-yr interval. On three farms we collected NFM from chickens and house sparrows (Passer domesticus) nesting on each farm, which we used to assess movement between host species. There was strong genetic structure among mites from different poultry farms and low estimates of migration between farms. There were significant differences between mites on chickens and house sparrows on two farms where sparrows nested near flocks, indicating no exchange of mites. Only one farm showed evidence of NFM movement between chickens and sparrows. There was high genetic similarity between mites collected 5 yr apart on each of two farms, indicating that NFM infestations can persist for long periods. The genetic patterns did not reveal sources of NFM infestations on chicken farms. The data suggest that NFMs are strongly differentiated, which likely reflects periodic population declines with flock turnover and pesticide pressure.

Efficacy and safety assessment of a water-soluble formulation of fluralaner for treatment of natural Ornithonyssus sylviarum infestations in laying hens.

BACKGROUND: Northern fowl mite, Ornithonyssus sylviarum (Canestrini & Fanzago, 1877), infestations can stress birds, impairing welfare and causing substantial economic losses. A study was undertaken to determine the efficacy of an ectoparasiticide solution (fluralaner) for oral administration in the treatment of mite-infested hens. METHODS: Clinically healthy, naturally mite-infested laying hens (n = 132), approximately 32 weeks of age, were ranked by Day -9 mite vent counts and randomized among 12 study pens, each to hold one of four treatment groups. Three groups received fluralaner-medicated water by oral gavage at dose rates of 0.25, 0.5 or 1.0 mg/kg on Days 0 and 7; one group was an untreated control (three pens for each group). Five naturally infested untreated birds were included in each pen to act as mite-infested source birds. Thus each pen, treated and control, had six non-source birds for assessment of efficacy, plus five source birds to provide ongoing challenge. Primary efficacy assessments were based on mean O. sylviarum vent counts from non-source birds in the control and treated group pens on Days 1, 2, 6, 8, 12, 15, 19, 22 and 26. RESULTS: Source-birds maintained infestations throughout the study, validating the challenge to study birds. On Days 1 through 22, mean control group mite counts were significantly greater than those of the treated groups (P ≤ 0.013). Relative to the control group, mean O. sylviarum counts were reduced by at least 90% from Day 6 through Days 19, 22 and 22 in the fluralaner 0.25, 0.5 and 1.0 mg/kg groups, respectively. On Day 19, mean mite counts were lower in the 0.5 and 1.0 mg/kg groups compared with the 0.25 mg/kg group (P ≤ 0.018), and in the 1.0 mg/kg compared with the 0.5 mg/kg group (P = 0.014). There were no adverse events in treated birds. CONCLUSIONS: A fluralaner solution administered twice by gavage to laying hens with a one-week between-treatment interval was safe and effective in quickly controlling O. sylviarum infestations despite continuous challenge from infested birds. By eliminating mites, this fluralaner solution has the potential to improve bird health and productivity, and to eliminate the burden of topical pesticide application.

Salmonella, including antibiotic-resistant Salmonella, from flies captured from cattle farms in Georgia, U.S.A.

Flies can be transmission vehicles of Salmonella from cattle to humans. This study determined the prevalence of Salmonella in/on flies captured from 33 cattle farms, including 5 beef and 28 dairy farms, in Georgia, USA, and characterized antibiotic resistance profiles of the isolated Salmonella. Twenty-six out of the 33 cattle farms (79%) and 185 out of the 1650 flies (11%) tested positive for Salmonella in the study. The incidence of Salmonella-positive flies varied from farm to farm, ranging from 0 to 78%. Among the 185 Salmonella isolated from flies, 29% were resistant to ampicillin, 28% to tetracycline, 21% to amoxicillin/clavulanic acid, 20% to cefoxitin, and 12% to streptomycin. Incidences of resistance against other tested antibiotics were low, ranging from 0 to 3%. Furthermore, 28% of the Salmonella isolates were multidrug resistant, demonstrating resistance to 3 or more antibiotics. The minimal inhibitory concentrations of ampicillin, cefoxitin, streptomycin, and tetracycline against the Salmonella isolates ranged from 32 to >2048, 64 to 2048, 128 to 1024, and 32 to 1024µg/mL, respectively. These data suggest that flies could be effective vehicles of transmitting antibiotic resistant Salmonella and disseminating antibiotic resistance genes on cattle farms, posing risks to human and animal health.

Ekbom syndrome: a delusional condition of "bugs in the skin".

Entomologists estimate that more than 100,000 Americans suffer from "invisible bug" infestations, a condition known clinically as Ekbom syndrome (ES), although the psychiatric literature dubs the condition "rare." This illustrates the reluctance of ES patients to seek mental health care, as they are convinced that their problem is bugs. In addition to suffering from the delusion that bugs are attacking their bodies, ES patients also experience visual and tactile hallucinations that they see and feel the bugs. ES patients exhibit a consistent complex of attributes and behaviors that can adversely affect their lives.

Ekbom syndrome: the challenge of "invisible bug" infestations.

Ekbom Syndrome is synonymous with delusory parasitosis, a belief that one's body is infested by invisible bugs. Persons suffering from this syndrome often claim to feel dermal sensations and to visualize the bugs, although no one else can see them. Ekbom Syndrome is a delusional condition; it is intractable and cannot be corrected by argument or evidence. Ekbom Syndrome sufferers exhibit a range of predictable behaviors in their attempts to eliminate their infestations, including seeking identifications and treatment from physicians and entomologists. Frequently they also experience comorbid psychological conditions. Because this is a delusional affliction, successful treatment typically requires neuroleptic medications, necessitating intervention by medical professionals.

Distribution of the brown recluse spider (Araneae: Sicariidae) in Georgia with comparison to poison center reports of envenomations.

Georgia is on the southeastern margin of the native range of the brown recluse spider, Loxosceles reclusa Gertsch and Mulaik. The brown recluse is not a common Georgia spider and has limited distribution in the state. Using recent submissions, previously published records, and examination of museum specimens, we document the spider's presence in 31 (19.5%) of Georgia's 159 counties, with almost all being found in the northern portion. The spider was collected almost exclusively north of the Fall Line (a transition zone separating the Piedmont and the Coastal Plain geological provinces). Only two locations in the southern Coastal Plain province produced L. reclusa specimens; these southern finds are considered spiders that were transported outside their range. There were six finds of the non-native world tramp species, L. rufescens (Dufour), three south of the Fall Line. In conspicuous contrast, over a 5-yr period, a Georgia poison center database recorded 963 reports of brown recluse spider bites from 103 counties. These figures greatly outnumber the historic verifications of brown recluses in the state for both specimen quantity and county occurrence, indicating improbable spider involvement and the overdiagnosis of bites. In the southern half of the state, medical diagnoses of brown recluse spider bites have virtually zero probability of being correct. Bite diagnoses should be made with caution in north Georgia given the spider's spotty distribution with low frequency of occurrence.

Nasal myiasis in an intensive care unit linked to hospital-wide mouse infestation.

A large city hospital experienced an infestation of mice combated in part by broadcasting poisoned baits. Months later there was an invasion of flies into the hospital, and 2 comatose patients in an intensive care unit contracted nasal maggots. Adult flies were trapped and maggots removed from the nares of the second patient. These were identified as the green blowfly (Phaenicia sericata). Recent downsizing of hospital personnel had led to the unintended and unrecognized loss of housekeeping services in the canteen food storage areas. A mouse infestation of the hospital occurred, with the epicenter in the canteen area. This was initially addressed by scattering poisoned bait and using rodent glue boards. The result of such treatment was the presence of numerous mouse carcasses scattered throughout the building attracting the green blowfly. Adult gravid female flies trapped in the new intensive care unit (where mice were not present) laid eggs in the fetid nasal discharge of 2 comatose patients. Live trapping of mice and removal of carcasses led to an abatement of the fly infestation. The cause-and-effect nature of the mouse carcasses and flies was underscored a year later when an outbreak of P. sericata occurred in the operating department and was linked to the presence of mouse carcasses on glue boards not removed the previous fall. Hence, the disruption or loss of 1 vital link in hospital organization (in this case, housekeeping support) may lead to an unintended and bizarre outcome.