Understanding attraction stimuli of the cat flea, Ctenocephalides felis, in non-chemical control methods.

Comparisons were conducted of flea catches of four commercially available flea traps in the laboratory and under field conditions, in both rural and urban locations. The results clearly showed the My Flea Trap™, which utilizes an intermittent light to attract fleas, to be far superior in trapping ability to the three continuous light traps; it caught up to 23 times as many fleas as the other traps. Altering the lighting mechanism to provide continuous rather than intermittent light significantly decreased the number of fleas captured. In addition, the use of a green filter significantly increased trapping efficiency, whereas the addition of a heat source had no apparent effect.

An immunoglobulin binding protein (antigen 5) of the stable fly (Diptera: Muscidae) salivary gland stimulates bovine immune responses.

The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), is an economically important pest of livestock. Previous studies demonstrated lymphocyte suppression by crude salivary gland extract (SGE) of the stable fly. A dominant 27-kDa protein identified in the SGE was reported to stimulate immunodominant antibody responses in exposed cattle. The purpose of this study was to determine whether this protein, now identified as ahomolog of insect proteins named antigen 5 (Ag5), was responsible for the lymphocyte suppression and whether naive calves can mount an immune response to it. Calves raised in the winter were immunized with recombinant Ag5 (rAg5) expressed in Drosophila S2 cells or with "natural" Ag5 protein isolated by preparative gel electrophoresis of SGE. Control calves were immunized with adjuvant alone. Rising antibody concentrations to rAg5 were detected in two of three calves immunized with rAg5 and one of three calves immunized with natural Ag5. Recall lymphocyte responses to rAg5 were detected at 21 and 28 d postimmunization in calves immunized with rAg5 but not in calves immunized with the natural Ag5 or those exposed to adjuvant alone. Mitogen-stimulated bovine lymphocyte responses were not suppressed by rAg5. Further investigation using immunoblotting revealed that rAg5 binds to the Fc and F (ab')2 portions of bovine IgG, but not to an Fab fragment. These findings suggest that Ag5 of the stable fly salivary gland is not immunosuppressive but that it has immunoglobulin binding properties and can invoke specific antibody and memory lymphocyte responses in immunized calves.

Flea blood feeding patterns in cats treated with oral nitenpyram and the topical insecticides imidacloprid, fipronil and selamectin.

A series of studies was conducted to determine the effect of systemically and topically active insecticides on blood consumption by fleas (Ctenocephalides felis). Infestations were conducted by placing fleas into plexi-glass chambers attached to the lateral rib cage of domestic short-hair cats. After pre-defined periods, fleas and flea feces were extracted using vacuum aspiration and spectrophotometrically analyzed for hemoglobin using Drabkin's reagent. To determine how rapidly nitenpyram kills actively feeding fleas, a single oral treatment was administered 24h after infestation. To determine the effect of nitenpyram on blood consumption of newly acquired fleas, cats were infested with fleas 1h post-treatment and fleas and flea feces from both studies were extracted at 15, 30, 60, 120, 240 and 480min post-treatment or post-infestation. To compare the effects of topically versus systemically active insecticides, 20 cats each with 2 chambers attached, were randomly allocated among groups and were infested with fleas 1h after each of 4 nitenpyram treatments, or at 7, 14, 21 and 28 days after a single application of commercial spot-on formulations of fipronil, imidacloprid or selamectin. Infestations were also completed for untreated (control) cats. Twenty-four hours after infestation, fleas and flea feces were removed for host blood quantification. If at any time, flea blood consumption in a treated group did not significantly differ from that of fleas infesting controls, that treatment group was withdrawn from the study. Nitenpyram effects on actively feeding fleas were first observed at 60min post-dosing when 38% of fleas were dead or moribund, and at 240min 100% were dead or moribund. Nitenpyram produced a significant reduction in flea blood consumption (p<0.05), which appeared to cease 15min after infestation. For the treatment comparisons, significantly more (p<0.05) blood was consumed by fleas taken from imidacloprid and fipronil-treated cats than from the nitenpyram or selamectin groups. Only on nitenpyram- or selamectin-treated cats were there significant reductions (p<0.05) in flea blood consumption on days 21 and 28, with significant difference (p>0.05) between these two groups on day 28. In this study systemically acting insecticides such as nitenpyram, and the topically applied but systemically active insecticide selamectin, were more effective in interfering with flea blood feeding than were imidacloprid and fipronil.

Vector competence of stable flies, Stomoxys calcitrans L. (Diptera: Muscidae), for Enterobacter sakazakii.

Enterobacter sakazakii is an opportunistic food-borne pathogen causing meningitis, enterocolitis, and sepsis, primarily in immunocompromised infants. It has been suggested that stable flies, Stomoxys calcitrans L., are a vector/reservoir of this pathogen. In this study, we assessed a) vector competence of adult stable flies (SF) for E. sakazakii, b) effect of E. sakazakii on SF development, and c) survival of E. sakazakii during SF development and colonization of the digestive tract of newly-emerged flies. Our data show that in the colony, adult SF can maintain E. sakazakii for at least 20 days regardless of the food source (blood or sugar) and contaminate the food source. The concentration of the pathogen per individual SF ranged from 1.8 x 10(5) to 6.4 x 10(6) CFU. E. sakazakii supported development of immature SF in sterilized cattle manure and sterilized artificial medium (78.3% and 76.7% SF survival to adult stage, respectively). In addition, E. sakazakii survived during SF development and colonized the gut of emerging adult SF but only when SF larvae were maintained on sterilized cattle manure inoculated with E. sakazakii (12.8% prevalence in adult SF) and on the sterile artificial medium with E. sakazakii (21.7% prevalence in adult SF). E. sakazakii was not recovered from flies or the substrate when larvae were reared on cattle manure with a non-sterilized complex microbial community plus the E. sakazakii inoculum. This study shows that SF adults have a potential to carry E. sakazakii for an extended period of time. E. sakazakii supports SF development and can survive during SF pupation and then colonize the gut of newly-emerged flies.

Development of a trap for collecting newly emerged Ctenocephalides felis (Siphonaptera: Pulicidae) in homes.

The visible light spectra most attractive to cat fleas, Ctenocephalides felis (Bouché), were determined. A green-yellow filter with a transmittance spectrum centered at 515-nm and a 82.5-nm half-height width attracted significantly more fleas than any other filter or white light. This information and observations on this flea's behavior were used to design a trap with a green-yellow filter and a light source with a 10-min:5-s (on and off) cycle. This trap collected > 86% of the live fleas released into a carpeted room (3.1 by 3.3 m) during a 20-h test period, whereas each of three commercially available flea traps collected approximately 13% of the fleas. Fleas < 1 d after emergence were not as responsive to the traps as older fleas. During 20-h testing periods, this new trap caught > 57% of the fleas released 8.4 m from the trap.

Landing pattern of stable flies (Diptera: Muscidae) on the alsynite cylinder trap: effect of wind speed and direction.

The distribution of stable flies, Stomoxys calcitrans (L.), caught on adhesive-coated Alsynite cylinder traps indicated that a significantly higher proportion of flies landed on the side most protected from the wind, and that flies were distributed equally on both sides of the traps bisected by the direction of the prevailing wind, and that the proportion of trapped flies decreased significantly with height on the trap. The landing pattern of house flies, Musca domestica L., appeared to differ from that of stable flies. As wind speed increased, the proportion of stable flies landing on the lower and downwind parts of the trap increased.

Susceptibility to insect growth regulators and cuticle deposition of the cat flea (Siphonaptera: Pulicidae) as a function of age.

Wandering larval, pharate pupal, pupal, and pharate adult stages of the cat flea, Ctenocephalides felis (Bouché), were identified by examination of cuticular cross sections via scanning electron microscopy. Visible morphological characteristics of each stage were identified and described. Various stages of the flea throughout metamorphosis were exposed to juvenile hormone mimics and insect developmental inhibitors. Wandering larvae treated with juvenile hormone mimics were unable to pupate, whereas treated pharate pupae ecdysed to the pupal stage but were unable to enclose. Pupae and pharate adults did not succumb to juvenile hormone mimic exposure, even at concentrations 3 orders of magnitude greater than those that killed 100% of the wandering larvae and the pharate pupae. Adult females were more susceptible to juvenile hormone mimics than males. Possible explanations for the variation in tolerance to juvenile hormone mimics of the differing stadia are discussed. None of the stages were susceptible to insect developmental inhibitor exposure. Analysis of catecholamines that are precursors of cuticle sclerotization and melanization were measured in the wandering larval through the pharate adult stages of the cat flea. N-acetyldopamine concentration was highest in the pupa stage when the flea had a hard, clear cuticle; N-beta-alanyldopamine concentration was highest during the production of the hard, dark cuticle of the pharate adult; and dopamine fluctuated throughout development but was highest in the pupal stage.

Ability of Musca autumnalis (Diptera: Muscidae) to acquire and transmit bovine herpesvirus-1.

Bovine herpesvirus-1 (BHV-1) was detected in Musca autumnalis De Geer after feeding on virus suspensions in bovine albumin or sucrose. Virus was detected for 48 h in flies fed an albumin suspension, with the highest titers recovered in crops (1.0 x 10(4) TCID50/ml) and whole-body (5 x 10(4) TCID50/ml/fly) specimens immediately after feeding; the level of virus declined rapidly thereafter. Virus titers in flies fed sucrose suspensions were 5 x 10(4) TCID50/ml in excised crops and 5 x 10(5) TCID50/ml in whole-body specimens; virus was not detected in flies 72 h after feeding. Four Hereford calves exposed for 4 h to BHV-1 fed flies did not develop any clinical symptoms related to BHV-1 transmission (i.e., elevated temperatures, ocular/nasal discharges, and labored breathing). Serum neutralization and plaque reduction tests did not show antibody production in calves exposed to BHV-1 infected flies. While we demonstrated that face flies retained BHV-1 for a short period of time, it does not appear that M. autumnalis is involved in either the mechanical or biological transmission of BHV-1.

Modulation of bovine lymphocyte response by salivary gland extracts of the stable fly, Stomoxys calcitrans (Diptera: Muscidae).

The effect of salivary gland extract of the stable fly, Stomoxys calcitrans (L), on bovine lymphocyte proliferation was determined, and antibody reactivity to salivary gland proteins was characterized in cattle exposed to stable flies. Salivary glands were dissected from male and female flies (4-8 d after eclosion), and protein extracts were made by freeze-thaw cycles. Salivary gland extract (SGE, 1 and 5 microg) significantly inhibited mitogen-driven proliferation of bovine lymphocytes, compared with 1 and 5 microg of identically prepared midgut extract (ANOVA, P < 0.05). Phytohemagglutinin A (PHA) stimulated lymphocyte responses were suppressed by 61.7 and 79.5% (mean values) with 1 and 5 microg of SCE, whereas concanvalin A (Con A) stimulated responses were suppressed by 62.9 and 77.1% (1 and 5 microg). In contrast, midgut extract (1 and 5 microg) minimally suppressed PHA (12.7% +/- 12.6 and 18.7% +/- 15.5) and Con A-driven responses (13.8% +/- 20.5 and 24.6% +/- 14.9), respectively. Viability studies using propidium iodide and flow cytometry demonstrated that SGE was not cytotoxic. Two-color immunofluorescence studies identified T and B lymphocytes as the nonviable cells in the cultures. Western blot analysis of serum collected from five dairy cows during periods of low and high fly exposure identified an immunodominant 27 kDa protein among the salivary gland proteins. These results indicate that exposure of cattle to stable fly saliva during blood feeding results in an antibody response to salivary proteins and that the saliva has a potential to modulate T lymphocyte function.

Emergence, survival, and fecundity of adult cat fleas (Siphonaptera: Pulicidae) exposed as pupae to juvenile hormone mimics.

Cat flea, Ctenocephalides felis felis (Bouché), adults exposed to sprays of methoprene, pyriproxyfen, or fenoxycarb as cocooned pupae emerged approximately 1 d earlier than adults from water-treated control pupae. Mortality of adult fleas, after exposure to juvenile hormone mimics as pupae, was increased over that of controls. Females had higher mortality than males within the first 48 h of feeding. Fecundity of females exposed as pupae to juvenile hormone mimics was not different from that of controls. Early emergence of preemerged adults from treated cocoons is discussed along with reasons for higher female susceptibility to juvenile hormone mimics.

The effect of sarcoptic mange on growth performance, leukocytes and lymphocyte proliferative responses in pigs.

The effects of a single artificial infestation with sarcoptic mite (Sarcoptes scabiei var. suis DeGeer) on weight gain and lymphocyte blastogenic responses were studied in untreated and fenvalerate-treated pigs. Average daily feed intake, average daily gain and feed efficiency were monitored for 5 weeks in 32 infested and 16 uninfested pigs. Total and differential leukocyte counts were determined and lymphocyte proliferative responses, using a mitogen-stimulated lymphocyte blastogenesis assay, were evaluated in 24 pigs. Sarcoptic mite infestation or treatment for sarcoptic mange did not affect total or differential leukocyte counts (P greater than 0.10). Differences were not observed in weight gain or lymphocyte blastogenic responses between infested and uninfested pigs.

Influence of sarcoptic mange and cold and ambient temperature on blastogenic responses of lymphocytes and serum cortisol concentrations of pigs.

Blood samples from sarcoptic mite-infested pigs were evaluated for effects of mite infestation and cold and ambient temperatures on lymphocyte blastogenic responses and for effects of mite infestation on serum cortisol concentrations. In experiment 1, sarcoptic mite-infested and noninfested pigs were housed in cold (5 to 15 C fluctuating) and thermoneural (25 C) environmental chambers for 5 weeks. Differences were not observed (P greater than 0.10) in blastogenic responses to phytohemagglutin or pokeweed mitogen between lymphocytes from infested and noninfested pigs on postinfestation days (PID) 7, 21, 28, and 35 in either environmental chamber. When lymphocytes from noninfested pigs were cultured with sera from infested pigs, alterations of blastogenic responses were not detected. Cortisol values were higher (P less than 0.05) in sera from sarcoptic mite-infested pigs, compared with those from noninfested pigs, at 4 PM on PID 14 and 4 AM and 10 AM on PID 15. Cortisol values were higher (P less than 0.05) in sera obtained at 10 AM on PID 14 and at 10 AM on PID 15 from pigs housed in cold chambers, compared with those from pigs housed in thermoneutral chambers. Interactive effects between sarcoptic mite infestation and cold ambient temperatures were not observed. At 4 AM on PID 15 (experiment 2), cortisol values were higher (P less than 0.05) in sera of infested pigs, compared with those in noninfested pigs. Seemingly, sarcoptic mange in pigs did not alter mitogen-induced lymphocyte blastogenic responses, but did increase serum cortisol concentrations, indicating that sarcoptic mange may be a stressor in pigs.

Mechanisms underlying sawtoothed grain beetle (Oryzaephilus surinamensis [L.]) (Coleoptera: Silvanidae) infestation of consumer food packaging materials.

The sawtoothed grain beetle, Oryzaephilus surinamensis (L.), is an extremely destructive pest of packaged consumer food products. The beetle is not believed to chew directly through packaging materials, but to use openings or flaws in damaged or improperly sealed packages to gain entry. We investigated the behavioral mechanisms by which the sawtoothed grain beetle infests packages with flaws. Significantly more sawtoothed grain beetles infested consumer food packages that had been punctured with 0.4 mm diameter holes, to simulate packaging flaws that preclude adults, than when packages had no flaws. In a test arena, females laid more eggs into or near the hole in a plastic packaging film, when they were able to contact the food through the hole than when they could not contact the food. First instar larvae placed either 1 mm or 1 cm away entered holes when food was present, indicating that packages could become infested if eggs were laid near holes. In the absence of food, neither adults nor larvae responded to holes. This study has shown the importance of sound packaging in preventing insect infestation.

Pupation site selection of cat fleas (Siphonaptera: Pulicidae) in various carpet types and its influence on insecticide efficacy.

Pupation sites of cat flea, Ctenocephalides felis (Bouché), larvae were determined in three styles of nylon and one style of wool carpet. Nylon saxony carpet had 59.3% of pupae at the top of the pile and 40% at the base of the pile. In nylon contract carpet, 55.2% of pupae were found at the top, 42.6% in the middle, and only 2.2% at the base of the pile. Nylon loop carpet contained 59.2% of pupae at the base, 25.5% in the middle, and 15.3% in the top of the pile. Wool loop carpet had 92.4% at the base and 3.8% both in the middle and top of the pile. Bioassays comparing the control of pupae manually placed at the base of carpets to that in carpets with natural pupation showed that control of pupae in the latter was 39-68% higher. Pupal control after natural pupation was greatest in nylon saxony and nylon contract carpets and lowest in nylon loop and wool loop carpets. Additional studies demonstrated that vacuuming provided the same level of pupal control on nylon saxony carpet as a spray application of permethrin to the carpet surface. Therefore, pupae that survived chemical and mechanical control treatments in nylon saxony carpet probably pupated away from the surface of the pile. Application of permethrin to the base of nylon saxony carpet did not significantly increase control. Future bioassays with cat flea pupae in carpet should be performed after natural pupation and consider carpet make and style.

Severe flea infestation in dairy calves.

An investigation was conducted of a severe flea infestation in Holstein dairy calves. Inspection of the dairy revealed hundreds of cat fleas, Ctenocephalides felis, on 23 calves, and thousands of fleas in the barn where the calves were housed. During the investigation, > 92,000 fleas were collected from the barn. The barn also was inhabited by 30 to 35 flea-infested domesticated and feral cats. Several calves appeared emaciated, and analysis of blood samples from 10 calves revealed that 8 were anemic. A control program was initiated, consisting of insecticide and insect-growth regulator treatment of calves and premises, along with removal of straw bedding from the barn. In addition, domesticated cats were to be treated and feral cats were to be removed by live trapping. Nine weeks after a complete control program was initiated, fleas were not evident on calves or in the barn.

Dispersal of stable flies (Diptera: Muscidae) from larval development sites in a Nebraska landscape.

Seven mark-recapture studies were conducted over 3 yr to assess dispersal of newly emerging adult stable flies, Stomoxys calcitrans L., from larval development sites in a mixed agricultural environment in northeastern Nebraska. Infested hay debris piles were marked by dusting their surfaces with fluorescent pigments, adults were captured with surrounding grids of Alsynite sticky traps, and specimens were dissected to determine feeding histories and reproductive age. Distances and directions of 3,889 marked specimens indicated males and females dispersed equally and in all directions. Midguts of males and females were equally likely to contain blood-meal remnants. Percentage with blood remnants and percentage of females with yolk increased with distance from mark origin, indicating survival and spread were positively associated with host finding success. A time-integrated diffusion model fit to results from the seven studies indicated 50% of stable fly adults had dispersed beyond 1.6 km of their natal site, but only 5% had dispersed beyond 5.1 km. These results indicate that stable fly adults on cattle in a given area are most likely to have originated from larval development sites within an ≈ 5 km radius of the subject cattle.