Diagnostic doses and times for Phlebotomus papatasi and Lutzomyia longipalpis sand flies (Diptera: Psychodidae: Phlebotominae) using the CDC bottle bioassay to assess insecticide resistance.

BACKGROUND: Insecticide resistance to synthetic chemical insecticides is a worldwide concern in phlebotomine sand flies (Diptera: Psychodidae), the vectors of Leishmania spp. parasites. The CDC bottle bioassay assesses resistance by testing populations against verified diagnostic doses and diagnostic times for an insecticide, but the assay has been used limitedly with sand flies. The objective of this study was to determine diagnostic doses and diagnostic times for laboratory Lutzomyia longipalpis (Lutz & Nieva) and Phlebotomus papatasi (Scopoli) to ten insecticides, including pyrethroids, organophosphates, carbamates, and DDT, that are used worldwide to control vectors. METHODS: Bioassays were conducted in 1,000-ml glass bottles each containing 10-25 sand flies from laboratory colonies of L. longipalpis or P. papatasi. Four pyrethroids, three organophosphates, two carbamates and one organochlorine, were evaluated. A series of concentrations were tested for each insecticide, and four replicates were conducted for each concentration. Diagnostic doses were determined only during the exposure bioassay for the organophosphates and carbamates. For the pyrethroids and DDT, diagnostic doses were determined for both the exposure bioassay and after a 24-hour recovery period. RESULTS: Both species are highly susceptible to the carbamates as their diagnostic doses are under 7.0 µg/ml. Both species are also highly susceptible to DDT during the exposure assay as their diagnostic doses are 7.5 µg/ml, yet their diagnostic doses for the 24-h recovery period are 650.0 µg/ml for Lu. longipalpis and 470.0 µg/ml for P. papatasi. CONCLUSIONS: Diagnostic doses and diagnostic times can now be incorporated into vector management programs that use the CDC bottle bioassay to assess insecticide resistance in field populations of Lu. longipalpis and P. papatasi. These findings provide initial starting points for determining diagnostic doses and diagnostic times for other sand fly vector species and wild populations using the CDC bottle bioassay.

Distribution and Habitat of Ixodes pacificus (Acari: Ixodidae) and Prevalence of Borrelia burgdorferi in Utah.

Knowledge about the distribution and abundance of the western black-legged tick, Ixodes pacificus Cooley and Kohls, in Utah is limited. Recent concerns over tick-borne diseases in Utah, primarily Lyme disease, have reinvigorated the need to understand the distribution and habitats favored by this tick species. We surveyed 157 sites throughout Utah to examine the distribution, abundance, and habitat of I. pacificus. In total, 343 adult ticks were collected from 2011 to 2013. Specifically, 119 I. pacificus, 217 Dermacentor andersoni Stiles, six D. albipictus Packard, and one D. hunteri Bishopp were collected. Overall, tick abundance was relatively low in the areas evaluated in Utah. I. pacificus collections were limited to sites above 1700 m. Ninety-two percent of I. pacificus were captured in the Sheeprock Mountains in Tooele County. I. pacificus positive collection sites were characterized by Gambel oak (Quercus gambelii Nuttall), juniper (Juniperus spp. L.), big sagebrush (Artemisia tridentata Nuttall) and black sagebrush (A. nova Nelson), and mixed grass habitat. All I. pacificus ticks were tested for the presence of Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt, and Brenner, sensu stricto) using real-time PCR. All ticks tested negative for B. burgdorferi. The likelihood of encountering I. pacificus and acquiring Lyme disease in the areas evaluated in Utah is considerably low due to low tick abundance and limited distribution, as well as low prevalence (or absence) of B. burgdorferi in Utah.