Predicting the Risk of Lyme Disease: Habitat Suitability for Ixodes scapularis in the North Central United States

The distribution and abundance of Ixodes scapularis were studied in Wisconsin, northern Illinois, and portions of the Upper Peninsula of Michigan by inspecting small mammals for ticks and by collecting questing ticks at 138 locations in state parks and natural areas. Environmental data were gathered at a local level (i.e., micro and meso levels), and a geographic information system (GIS) was used with several digitized coverages of environmental data to create a habitat profile for each site and a grid map for Wisconsin and Illinois. Results showed that the presence and abundance of I. scapularis varied, even when the host population was adequate. Tick presence was positively associated with deciduous, dry to mesic forests and alfisol-type soils of sandy or loam-sand textures overlying sedimentary rock. Tick absence was associated with grasslands, conifer forests, wet to wet/mesic forests, acidic soils of low fertility and a clay soil texture, and Precambrian bedrock. We performed a discriminant analysis to determine environmental differences between positive and negative tick sites and a regression equation to examine the probability of I. scapularis presence per grid. Both analyses indicated that soil order and land cover were the dominant contributors to tick presence. We then constructed a risk map indicating suitable habitats within areas where I. scapularis is already established. The risk map also shows areas of high probability the tick will become established if introduced. Thus, this risk analysis has both explanatory power and predictive capability

Quantitative Factors Proposed to Influence the Prevalence of Canine Tick-Bourne Disease Agents in the United States

The Companion Animal Parasite Council hosted a meeting to identify quantifiable factors that can influence the prevalence of tick-borne disease agents among dogs in North America. This report summarizes the approach used and the factors identified for further analysis with mathematical models of canine exposure to tick-borne pathogens

Quantitative Factors Proposed to Influence the Prevalence of Canine Tick-Borne Disease Agents in the United States

The Companion Animal Parasite Council hosted a meeting to identify quantifiable factors that can influence the prevalence of tick-borne disease agents among dogs in North America. This report summarizes the approach used and the factors identified for further analysis with mathematical models of canine exposure to tick-borne pathogens

County-Level Surveillance of White-Tailed Deer Infestation by \u3ci\u3eIxodes scapularis\u3c/i\u3e and \u3ci\u3eDermacentor albipictus\u3c/i\u3e (Acari: Ixodidae) Along the Illinois River

From 1998 to 2003, 4,935 hunter-killed deer in northern and central Illinois were examined for ticks; 4,066 blacklegged ticks, Ixodes scapularis Say, and 6,530 winter ticks, Dermacentor albipictus (Packard) (Acari: Ixodidae), were collected. I. scapularis was the predominant tick species in the northern portion of the study area, with a decreasing north-to-south prevalence gradient. In contrast, D. albipictus was more common in the south with a decreasing south-to-north prevalence gradient. Compared with previous studies, the geographic range for both species expanded into the central portion of the Illinois River. Prevalence and intensity of both tick species were greater on bucks, and infested bucks were geographically more widespread than infested does and fawns. These findings indicate that blacklegged tick and winter tick distributions remain dynamic in the north central United State

Dispersal of Synanthropic Diptera: Lessons from the Past and Technology for the Future

The impact of aerial invasion of new habitats by dispersal of synanthropic arthropods on human society is one of the most important topics in the entomological world. A review is presented of important advances in the knowledge of dispersal of a number of dipteran species that cause damage to, or serve as vectors for diseases of, humans and associated animals. The components of aerial dispersal are delineated, and forms of dispersal are defined in the context of interactive forces that result in dispersal by synanthropic Diptera. Migratory flights by black flies are put into ecological perspective, as are the wind-borne movements of ceratopogonid vectors of viruses. Dispersal by house flies, screwworms, and stable flies are specifically addressed to trace the changes in technology used to detect and quantify aerial dispersal during the 20th century and to propose new ways to use current technology

Long-term reduction of \u3ci\u3eTrypanosoma cruzi\u3c/i\u3e infection in sylvatic mammals following deforestation and sustained vector surveillance in northwestern Argentina

Long-term variations in the dynamics and intensity of sylvatic transmission of Trypanosoma cruzi were investigated around eight rural villages in the semiarid Argentine Chaco in 2002–2004 and compared to data collected locally in 1984–1991. Of 501 wild mammals from 13 identified species examined by xenodiagnosis, only 3 (7.9%) of 38 Didelphis albiventris opossums and 1 (1.1%) of 91 Conepatus chinga skunks were infected by T. cruzi. The period prevalence in opossums was fourfold lower in 2002–2004 than in 1984–1991 (32–36%). The infection prevalence of skunks also decreased five-fold from 4.1–5.6% in 1984–1991 to 1.1% in 2002–2004. Infection in opossums increased with age and from summer to spring in both study periods. The force of infection per 100 opossum-months after weaning declined more than six-fold from 8.2 in 1988–1991 to 1.2 in 2002– 2004. Opossums were mainly infected by T. cruzi lineage I and secondarily by lineage IId in 1984– 1991, and only by T. cruzi I in 2002–2004; skunks were infected by T. cruzi IId in 1984–1991 and by IIc in 2002–2004. The striking decline of T. cruzi infection in opossums and skunks occurred in parallel to community-wide insecticide spraying followed by selective sprays leading to very low densities of infected Triatoma infestans in domestic and peridomestic habitats since 1992; to massive deforestation around one of the villages or selective extraction of older trees, and apparent reductions in opossum abundance jointly with increases in foxes and skunks. These factors may underlie the dramatic decrease of T. cruzi infection in wild reservoir hosts

Spatiotemporal Patterns of Host-Seeking \u3ci\u3eIxodes scapularis\u3c/i\u3e Nymphs (Acari: Ixodidae) in the United States

The risk of Lyme disease for humans in the eastern United States is dependent on the density of host-seeking Ixodes scapularis Say nymphal stage ticks infected with Borrelia burgdorferi. Although many local and regional studies have estimated Lyme disease risk using these parameters, this is the first large-scale study using a standardized methodology. Density of host-seeking I. scapularis nymphs was measured by drag sampling of closed canopy deciduous forest habitats in 95 locations spaced among 2° quadrants covering the entire United States east of the 100th meridian. Sampling was done in five standardized transects at each site and repeated three to six times during the summer of 2004. The total number of adults and nymphs of the seven tick species collected was 17,972, with 1,405 nymphal I. scapularis collected in 31 of the 95 sites. Peak global spatial autocorrelation values were found at the smallest lag distance (300 km) and decreased significantly after 1,000 km. Local autocorrelation statistics identified two significant high-density clusters around endemic areas in the northeast and upper Midwest and a low-density cluster in sites south of the 39th parallel, where only 21 nymphs were collected. Peak nymphal host-seeking density occurred earlier in the southern than in the most northern sites. Spatiotemporal density patterns will be combined with Borrelia prevalence data as part of a 4-yr survey to generate a nationwide spatial risk model for I. scapularis-borne Borrelia, which will improve targeting of disease prevention efforts