Weather variability affects abundance of larval Culex (Diptera: Culicidae) in storm water catch basins in suburban Chicago.

Culex pipiens L. (Diptera: Culicidae) and Culex restuans Theobald are the primary enzootic and bridge vectors of West Nile virus in the eastern United States north of 36 degrees latitude. Recent studies of the natural history of these species have implicated catch basins and underground storm drain systems as important larval development sites in urban and suburban locales. Although the presence of larvae in these habitats is well-documented, the influence of abiotic factors on the ecology of Culex larvae developing in them remains poorly understood. Therefore, we examined the effects of multiple abiotic factors and their interactions on abundance of Culex larvae in catch basins in the Chicago, IL, metropolitan area. Low precipitation and high mean daily temperature were associated with high larval abundance, whereas there was no correlation between catch basin depth or water depth and larval abundance. Rainfall was an especially strong predictor of presence or absence of larvae in the summer of 2010, a season with an unusually high precipitation. Regression tree methods were used to build a schematic decision tree model of the interactions among these factors. This practical, visual representation of key predictors of high larval production may be used by local mosquito abatement districts to target limited resources to treat catch basins when they are particularly likely to produce West Nile virus vectors.

Muellerius capillaris dominates the lungworm community of bighorn sheep at the National Bison Range, Montana.

Lungworm infections are common among bighorn sheep (Ovis canadensis) in North America, and the predominant species reported are Protostrongylus stilesi and P. rushi. The only records of another lungworm species, Muellerius capillaris, infecting bighorns come from South Dakota, USA. At the National Bison Range (NBR), Montana, USA we found that across six sampling periods, 100% of wild bighorn sheep surveyed were passing first-stage dorsal-spined larvae (DSL) which appeared to be consistent with M. capillaris. By contrast, only 39% or fewer sheep were passing Protostrongylus larvae. Using molecular techniques, we positively identified the DSL from the NBR bighorns as M. capillaris. This is the first definitive record of M. capillaris infection in a free-ranging bighorn sheep population outside of South Dakota.

Effects of supplemental feeding on gastrointestinal parasite infection in elk (Cervus elaphus): preliminary observations.

The effects of management practices on the spread and impact of parasites and infectious diseases in wildlife and domestic animals are of increasing concern worldwide, particularly in cases where management of wild species can influence disease spill-over into domestic animals. In the Greater Yellowstone Ecosystem, USA, winter supplemental feeding of Rocky Mountain elk (Cervus elaphus) may enhance parasite and disease transmission by aggregating elk on feedgrounds. In this study, we tested the effect of supplemental feeding on gastrointestinal parasite infection in elk by comparing fecal egg/oocyst counts of fed and unfed elk. We collected fecal samples from fed and unfed elk at feedground and control sites from January to April 2006, and screened all samples for parasites. Six different parasite types were identified, and 48.7% of samples were infected with at least one parasite. Gastrointestinal (GI) nematodes (Nematoda: Strongylida), Trichuris spp., and coccidia were the most common parasites observed. For all three of these parasites, fecal egg/oocyst counts increased from January to April. Supplementally fed elk had significantly higher GI nematode egg counts than unfed elk in January and February, but significantly lower counts in April. These patterns suggest that supplemental feeding may both increase exposure and decrease susceptibility of elk to GI nematodes, resulting in differences in temporal patterns of egg shedding between fed and unfed elk.