THE STRUCTURE AND SEASONALITY OF BAYLISASCARIS PROCYONIS POPULATIONS IN RACCOONS (PROCYON LOTOR).

Baylisascaris procyonis , the raccoon ( Procyon lotor ) ascarid, is a common roundworm parasite of raccoons that is also a well-recognized zoonotic pathogen, and a cause for conservation concern. The transmission dynamics of B. procyonis differ with host population attributes, season, and landscape. We examined how the parasite's population attributes change with season, parasite population structure, and host demographics. We examined 1,050 raccoon gastrointestinal tracts collected from 1996 to 2012. Of the 1,050 raccoons necropsied, 382 (36%) were infected with at least one B. procyonis (x¯=15.8 [95% confidence interval=13.39-18.26]; median=7; range 1-199 worms/host), and populations were overdispersed. There was a seasonal change in prevalence with a peak in October/November. Worm burdens decreased approximately 28% per month from January to June and increased approximately 31% per month from June to December. The sex structure of B. procyonis populations was female-biased (56% female). Host demographics did not impact parasite population attributes. This study provides evidence that B. procyonis populations exhibit a yearly cycle of loss and recruitment that may impact the transmission dynamics of the parasite.

Microgeographic Population Genetic Structure of Baylisascaris procyonis (Nematoda: Ascaroidae) in Western Michigan Indicates the Grand River Is a Barrier to Gene Flow.

Baylisascaris procyonis , the raccoon roundworm, is increasingly being recognized for its zoonotic and public health importance. Fine-scale analyses of the population genetics of this species have been hampered due to a lack of appropriate genetic markers. To this end, we developed 8 novel polymorphic microsatellites for B. procyonis and used these markers to elucidate microgeographic structuring of this parasite in a 500-km(2) study area in western Michigan. Our analyses revealed significant levels of genetic differentiation amongst the 74 worms collected from 10 different raccoons. Critically, Bayesian clustering indicated 2 genetically distinct groups, one on either side of the Grand River which bisects our study area. Estimates of F(ST), and results from AMOVA and isolation by distance, further corroborated a scenario whereby the river is acting as a barrier to gene flow, a rather unexpected finding given the high vagility of raccoons and microgeographic scale of the analysis. It is possible that the Grand River is a major dispersal barrier for B. procyonis because raccoons are most likely to disperse across the river when it is frozen, and worm burden in raccoons approaches zero during the winter.

EVALUATION OF ANTHELMINTIC FISHMEAL POLYMER BAITS FOR THE CONTROL OF BAYLISASCARIS PROCYONIS IN FREE-RANGING RACCOONS (PROCYON LOTOR).

Baylisascaris procyonis is a common gastrointestinal parasite of raccoons (Procyon lotor) and is a zoonotic helminth with the potential to cause severe or fatal infection. Raccoons thrive in human-dominated landscapes, and the fecal-oral transmission pathway and lack of effective treatment make B. procyonis a serious threat to public health. The distribution of medicinal baits has emerged as a socially acceptable and cost-effective method for managing disease in free-ranging wildlife. We assessed the suitability of a mass-producible anthelmintic bait for B. procyonis mitigation by evaluating the willingness of free-ranging raccoons to consume anthelmintic baits and determining whether bait consumption successfully cleared B. procyonis infections from raccoons. Anthelmintic baits were modified from standard fishmeal polymer baits, the food attractant commonly used in oral rabies vaccine baits, with the introduction of 220 mg of pyrantel pamoate into the fishmeal mixture. We captured 16 naturally infected raccoons, presented one anthelmintic bait, and monitored B. procyonis infection over 90 d by screening feces for eggs. Treatment cleared B. procyonis infections for nine of 12 raccoons that consumed >10 g of the 15 g bait. We used remote cameras to monitor in situ patterns of bait consumption for anthelmintic baits relative to standard baits. Both anthelmintic and standard baits were rapidly consumed, with no differences in the rate of consumption between bait types. However, after bait contact, raccoons demonstrated a greater willingness to consume standard baits while ignoring anthelmintic baits more frequently (P = 0.06). Initial trials of anthelmintic baits show promise, although refinement in both dose and palatability is needed. At mass production scales, the addition of pyrantel pamoate to fishmeal polymer baits would be inexpensive, potentially making anthelmintic baits a viable management option when coupled with an oral rabies vaccine or used independently for B. procyonis mitigation.

Development of an automated dispenser for the delivery of medicinal or vaccine-laden baits to raccoons (Procyon lotor).

Medicinal baits are distributed to manage zoonotic diseases, including raccoon (Procyon lotor) rabies, but efficient distribution strategies are needed for suburban environments. We developed an automated dispenser that transfers fishmeal polymer baits at user-specified intervals from a magazine to a receptacle fitted with a filter that exploits raccoon dexterity to limit consumption by nontarget species. We introduce the concept of automated dispensers and describe bait removal success rates for raccoons versus nontarget species. We monitored visitation with remote cameras after deploying a dispenser, programmed to present two baits per night, in three disjunct forest patches in northwest Indiana. Raccoons removed 72% of baits; nontarget, white-footed mice (Peromyscus leucopus) removed 11%; Virginia opossums (Didelphis virginiana) removed 9%. Bait removal success varied significantly between raccoons (76%) and opossums (21%), improving bait delivery specificity relative to hand baiting. Accumulation of baits in receptacles resulted in excess (more than one) bait consumption (39% of baits consumed by raccoons were excess), suggesting design improvements are needed to present additional baits only after previous baits have been consumed. Automated dispensers successfully sustained bait availability throughout the operational period. Subsequent research is needed to determine whether a sustained availability of baits achieved with automated dispensers is more effective for the treatment of raccoons in suburban environments than traditional distribution methods.

Surveillance for Baylisascaris procyonis in raccoons (Procyon lotor) from Wyoming, USA.

Baylisascaris procyonis is a common roundworm of raccoons that causes severe clinical disease in many vertebrates, including humans. The distribution of B. procyonis in the US is poorly documented in portions of its range and has not been reported from Wyoming. Our objectives were to determine the statewide distribution and prevalence of this parasite in raccoons in Wyoming, using intestinal and fecal examinations. We examined 363 raccoons from 23 Wyoming counties in 2009-11, testing the reliability of two methods (intestinal extrusion and incision) to determine worm burdens. We found 163 raccoons (45%) positive for B. procyonis. The two methods of examination did not differ, although extrusion missed some infections. Neither age nor sex affected apparent prevalence or worm burdens. Prevalence did not differ with land use, yet burden was highest among rural raccoons. Fecal examination revealed that juvenile raccoons had a higher proportion of patent infections than adults, but neither sex nor location were indicators of prevalence. Egg density (eggs per gram of feces) did not differ by sex or age; however, rural raccoons had higher egg densities than urban/suburban animals. Understanding the distribution and prevalence of B. procyonis in Wyoming, especially in and around highly populated areas, is an important step in educating the general public and medical community on the potential risks of raccoon roundworm infection.

Use of experimental translocations of Allegheny woodrat to decipher causal agents of decline.

Translocations are an important tool for wildlife conservation, although progress in the field of reintroduction biology has been hindered by the ad hoc and opportunistic nature of many translocations. We used an experimental translocation to elucidate the role of raccoon roundworm (Baylisascaris procyonis) and inbreeding depression in the decline of the Allegheny woodrat (Neotoma magister), an endangered species. We translocated woodrats from genetically diverse populations in the core of the species range to 4 previously occupied sites (reintroductions) and 2 sites supporting genetically depauperate populations (reinforcements) in Indiana (U.S.A.). In 2 reintroduction sites and 1 reinforcement site, we distributed anthelmintic baits to passively deworm raccoons and reduce the risk of woodrat exposure to roundworms. The remaining sites served as controls. We used raccoon latrine surveys and fecal flotation to monitor temporal variability in roundworm prevalence and effect of treatment. We used live trapping and microsatellite genotyping to monitor the demographic and genetic response of translocated populations over the following 54 months. At the conclusion of the study, 4 of 6 translocations were successfully maintaining abundance through local recruitment. The distribution of anthelmintic baits reduced levels of roundworm contamination, but levels of contamination were also low in 2 of 3 control sites. Reintroductions failed at control sites, one of which was due to high roundworm exposure. The other failed control reintroduction was likely attributable to demographic stochasticity and limited reproductive potential following initial mortality within the first 4 months. In both control and treatment reinforcements, increases in both allelic richness and heterozygosity were accompanied by increases in abundance, which is suggestive of genetic rescue. Our results demonstrate that mitigation of roundworm exposure through the distribution of anthelmintic baits can facilitate woodrat recovery and that diversity within genetically depauperate populations can be restored through the introduction of a limited number of individuals.

Effects of urbanization on prevalence of Baylisascaris procyonis in intermediate host populations.

Baylisascaris procyonis is an intestinal parasite of raccoons (Procyon lotor) that can also infect humans and a wide range of wildlife species. Prevalence of B. procyonis in raccoon populations appears to decrease as the landscape urbanizes, but less is known about prevalence in the small-mammal intermediate hosts of the parasite. We measured prevalence of B. procyonis in populations of mice (Peromyscus spp.) in forest preserves along a gradient of urbanization in Illinois. Prevalence in the mouse intermediate host exhibited a trend opposite raccoons: prevalence increased as surrounding human population density increased. This counterintuitive result may be due to higher overall environmental loads of B. procyonis in urban areas due to higher raccoon densities. Our results emphasize the need to understand fully the transmission dynamics of B. procyonis in its definitive and intermediate hosts in order to design and implement effective strategies to mitigate zoonotic risks to humans.

Prevalence of Baylisascaris procyonis in habitat associated with Allegheny woodrat (Neotoma magister) populations in Indiana.

Allegheny woodrat (Neotoma magister) populations have been in decline across their range since the late 1970s. Hypotheses proposed to explain these declines include habitat fragmentation and loss, decreased food availability, and increased mortality from infection with Baylisascaris procyonis. We investigated the prevalence of B. procyonis at raccoon (Procyon lotor) latrines in woodrat cliff habitats (n = 18) along the Ohio River in southern Indiana in 1995. We located 275 latrines (mean = 15.3/site; range, 6-34) and found B. procyonis in 13 (4.7%) latrines across all sites. When present at a site, B. procyonis occurred, on average, at 11.1%of latrines (range, 3-36%). Woodrat abundance, determined through a concurrent live-trapping program, was significantly higher (χ(2) = 5.12, df = 1, P = 0.024) at sites where B. procyonis was not found (9.5 ± 2.52) than at sites with B. procyonis (3.7 ± 2.2). Our analyses support the hypothesis that this parasite could contribute to declines in woodrat abundance. Because woodrats cache nonfood items, including raccoon feces, and are highly susceptible to the parasite, they are at increased risk for B. procyonis infection, which could be deleterious, especially to small populations.

Optimization of Raccoon latrine surveys for quantifying exposure to Baylisascaris procyonis.

Raccoon (Procyon lotor) latrine surveys are an efficient and cost-effective method to quantify Baylisascaris procyonis exposure risk for intermediate hosts. Nevertheless, current methodologies may introduce bias by homogenizing scats collected within latrines and estimating exposure risk at the latrine scale. The objective of this study was to examine the potential for raccoon latrine size to bias estimates of risk of exposure when utilizing current methodologies that pool scats prior to analysis. We accomplished this by evaluating correlation of the presence of B. procyonis eggs among scats collected within latrines. Specimens were collected in southern Indiana during November and December of 2006. Raccoon scats collected within latrines exhibited no correlation with the presence of B. procyonis eggs. Accordingly, to eliminate the bias introduced by pooling scats within latrines, scats rather than latrines should be treated as the sampling unit for estimating risk of exposure for intermediate hosts. Further, evaluation of exposure risk based on individual scats has the potential to greatly reduce the time and expense associated with obtaining precise estimates of B. procyonis exposure risk.

The relationship between Baylisascaris procyonis prevalence and raccoon population structure.

Parasite transmission is a dynamic process that can be affected by factors including host and parasite population dynamics. Raccoons ( Procyon lotor ) are the definitive host of Baylisascaris procyonis , an intestinal roundworm. Transmission of this parasite has been linked to raccoon behavior and human land-use patterns; however, we do not know the importance of host population structure. Therefore, the objective of this study was to determine the relationship between raccoon population attributes and prevalence of B. procyonis. We necropsied 307 trapped or road-killed raccoons collected during 2000-2006 from the Chicago area. In addition, we examined, via fecal samples (n  =  433), the patterns of B. procyonis prevalence as they relate to population dynamics among 3 subpopulations within the larger study. Baylisascaris procyonis was seen in 39% of 307 necropsied raccoons. There were differences in prevalence as a function of host age and sex. Baylisascaris procyonis was observed in 18% of 433 fecal samples obtained from live-trapped raccoons, and there were differences according to age, but not by sex. We found that the host populations consistently differed in density across study areas, but were similar regarding sex and age structure. Differences in host density were associated with differences in prevalence, suggesting that possible differences between populations, as well as ecological differences in sites and raccoon behavior, may have influenced parasite prevalence.

Land-use effects on prevalence of raccoon roundworm (Baylisascaris procyonis).

The raccoon (Procyon lotor) is the definitive host of Baylisascaris procyonis, a large intestinal roundworm that is zoonotic and can result in fatal or severe central nervous system disease in young children. Prevalence of infection among raccoon populations often is high, and in the midwestern United States, B. procyonis has been reported in 68-82% of raccoons. Raccoon populations have increased in response to changes in human land use, and often reach higher densities in urban and suburban landscapes than rural landscapes. However, shifts in foraging behavior among urban raccoons could impact the transmission of B. procyonis if small vertebrate intermediate hosts are not a significant part of the raccoon diet. The objective of this study was to compare prevalence of B. procyonis infection between urban and rural raccoon populations on a regional scale. Necropsy was done on 204 raccoons collected from September through February during 2000-2005 from seven states across the Midwest (regional sample). Baylisascaris procyonis was found in 54% of examined raccoons. Prevalence differed between land-use types (chi2=11.56, df=1, P=0.0007), and was higher among animals collected from rural locations (65%) than those collected in urban locations (41%). Intensity of infection also differed (F=5.52, df=1, P=0.02), with rural raccoons having greater worm burdens (x=29.63+/-36.42) than urban raccoons (x=13.85+/-18.47). Despite high densities of raccoons in urban landscapes, fewer urban raccoons were infected with B. procyonis, suggesting decreased dependence on intermediate hosts as a food source. This possible explanation was supported by a similar trend in prevalence among subsamples of raccoons collected from three Chicago-area populations (local samples) with differing levels of urbanization, population densities, and foraging behavior that had been intensively monitored during 1995-2002. Decreased transmission of B. procyonis in urban landscapes may be due to decreased predation of intermediate hosts, and contact of juvenile raccoons with B. procyonis eggs may be an important factor in maintaining infections within such populations.