Demographic, environmental and physiological predictors of gastrointestinal parasites in urban raccoons

Raccoons are host to diverse gastrointestinal parasites, but little is known about the ecology of these parasites in terms of their interactions with each other during coinfections, their interactions with host physiology and environmental factors, and their impact on raccoon health and survival. As a first step, we investigated the patterns of parasite infection and their demographic distribution in an urban-suburban population of raccoons trapped in the summers and autumns of 2018 and 2019. We collected faecal samples, demographic data, morphometric measurements, and blood smears, and used GPS data to classify trapping location by land cover type. Faecal floats were performed to detect and quantify gastrointestinal nematode eggs and coccidia oocysts, and white blood cell differentials were performed on blood smears to characterise white blood cell distributions. Data were analysed cross-sectionally and, where possible, longitudinally, using generalised linear models. Overall, 62.6% of sampled raccoons were infected with gastrointestinal nematodes, and 82.2% were infected with gastrointestinal coccidia. We analysed predictors of infection status and faecal egg count for three different morphotypes of nematode-Baylisascaris, strongyle, and capillariid nematodes-and found that infection status and egg count varied with Year, Month, Age class, Land cover, and coinfection status, though the significance of these predictors varied between nematode types. Gastrointestinal coccidia prevalence varied with Year, Month, Age class, strongyle infection status, and capillariid infection status. Coccidia oocyst counts were lower in adults and in October, but higher in females and in raccoons trapped in areas with natural land cover; furthermore, coccidia oocysts were positively associated with capillariid faecal egg counts. We found no evidence that gastrointestinal parasites influenced raccoon body condition or overwinter mortality, and so conclude that raccoons, though harbouring diverse and abundant gastrointestinal parasites, may be relatively tolerant of these parasites.

Helminths in Invasive Raccoons (Procyon lotor) from Southwest Germany

As hosts of numerous zoonotic pathogens, the role of raccoons needs to be considered in the One Health context. Raccoons progressively expand their range as invasive alien species in Europe. This study aimed to investigate the intestinal helminth fauna of raccoons in Baden-Wuerttemberg, Germany, as no such screening had ever been conducted there. In total, we obtained 102 animals from hunters in 2019 and 2020. Intestinal helminths were retrieved using the SSCT (segmented sedimentation and counting technique) and identified morphologically and by PCR-based Sanger sequencing. Fecal samples were assessed using the ELISA PetChek^TM IP assay (IDEXX, Germany) and flotation technique. The artificial digestion method was employed for analyzing muscle tissue. We detected species of four nematode genera (Baylisascaris procyonis, Toxocara canis, Capillaria spp., and Trichuris spp.), three cestode genera (Atriotaenia cf. incisa/procyonis, Taenia martis, and Mesocestoides spp.), and three trematode genera (Isthmiophora hortensis/melis, Plagiorchis muris, and Brachylaima spp.). Echinococcus spp. and Trichinella spp. were not found. The invasive behavior and synanthropic habits of raccoons may increase the infection risk with these helminths in wildlife, domestic and zoo animals, and humans by serving as a connecting link. Therefore, it is crucial to initiate additional studies assessing these risks.

The Raccoon (Procyon lotor) as a Neozoon in Europe

The raccoon (Procyon lotor) is a North American half-bear that is present in much of Europe and Asia as a result of both accidental and planned releases. In Europe, raccoons were introduced primarily as a source of fur for the fur industry. In the 1930s, raccoons were released into the wild in Central Europe. At the same time, animals from fur farms and private holdings continued to enter the wild. In the following decades, the raccoon spread over large parts of Europe. In addition to the invasive spread of the Central European initial population, individual releases of raccoons occurred frequently, mainly in Southern Europe. The high adaptability of the raccoon favors its expansion into new habitats. It has a high reproductive rate, is very mobile, and encounters few predators in Europe. Raccoons have recently become a topic of interest when large raccoon populations have colonized suburban and urban areas. Despite the proximity of raccoons and humans, however, there have been hardly any conflicts to date, unlike in North America. A significant negative impact on the native fauna has been suspected but not proven. Raccoons have been identified as vectors of zoonotic diseases. Nevertheless, monitoring of the increasing numbers of raccoons in Europe seems advisable.

Spatio-temporal clustering of Baylisascaris procyonis, a zoonotic parasite, in raccoons across different landscapes in southern Ontario

Baylisascaris procyonis, the raccoon roundworm, is a parasite found throughout North America and parts of Europe. More than 150 species of mammals and birds including humans can develop neurological disease following infection with the larval stage of this parasite. To investigate whether B. procyonis infections in raccoons cluster in space, time, or space-time, we used data from 1353 Ontario raccoons submitted to the Canadian Wildlife Health Cooperative between 2013 and 2016. We identified a significant spatial cluster of increased infection prevalence in southern Ontario centered over a major metropolitan area, as well as a significant cluster of decreased infection prevalence in a primarily agricultural region in southwestern Ontario. Furthermore, we identified statistically significant temporal clusters in the fall in annual scans of data from 2014, 2015 and 2016. Examination of both Bernoulli and space-time permutation models for space-time analysis suggested that the purely spatial and temporal clusters were not explained by relatively short and spatially discrete events in space-time. The identified annual temporal clusters are consistent with previous research on the seasonality of B. procyonis infection in raccoons. Recognition of the spatial infection clusters will help identify potential geographic and anthropogenic factors associated with the occurrence of B. procyonis infection in raccoons. Given the zoonotic potential of this parasite, identification of a cluster of high infection prevalence in a major metropolitan area has implications for public education and risk management strategies.

Experimental comparison of Baylisascaris procyonis definitive host competence between domestic dogs and raccoons (Procyon lotor)

Domestic dogs can function as either paratenic or definitive hosts for the zoonotic raccoon roundworm Baylisascaris procyonis. However, factors leading to development of patent infections in dogs are under-studied. Here we compared infection dynamics of B. procyonis in dogs vs the natural raccoon host. Dogs and raccoons were inoculated 5000 or 500 B. procyonis eggs (n = 3 per dose) or were fed B. procyonis-infected laboratory mice (n = 3 per dose; mice inoculated with 1000 or 250 eggs). Fecal samples were analysed via flotation and a commercial coproantigen ELISA designed for detection of Toxocara spp. Two of 12 dogs (both received low dose larvae) developed patent infections; all 12 raccoons became infected with 10 developing patent infections. Compared with dogs, prepatent periods were shorter in raccoons and maximum egg outputs were much greater. Baylisascaris procyonis coproantigens were detectable via ELISA in all raccoons and the patently infected dogs. Finally, dogs spontaneously lost infections while all patently infected raccoons shed eggs until conclusion of the study. Our results demonstrate that dogs are clearly suboptimal hosts showing limited parasite establishment and fecundity vs raccoons. Despite the low competence, patently infected dogs still pose a risk for human exposure, emphasizing the importance of control measures.

The value of monitoring wildlife roadkill

The number of wildlife-vehicle collisions has an obvious value in estimating the direct effects of roads on wildlife, i.e. mortality due to vehicle collisions. Given the nature of the data—species identification and location—there is, however, much wider ecological knowledge that can be gained by monitoring wildlife roadkill. Here, we review the added value and opportunities provided by these data, through a series of case studies where such data have been instrumental in contributing to the advancement of knowledge in species distributions, population dynamics, and animal behaviour, as well as informing us about health of the species and of the environment. We propose that consistently, systematically, and extensively monitoring roadkill facilitates five critical areas of ecological study: (1) monitoring of roadkill numbers, (2) monitoring of population trends, (3) mapping of native and invasive species distributions, (4) animal behaviour, and (5) monitoring of contaminants and disease. The collection of such data also offers a valuable opportunity for members of the public to be directly involved in scientific data collection and research (citizen science). Through continuing to monitor wildlife roadkill, we can expand our knowledge across a wide range of ecological research areas, as well as facilitating investigations that aim to reduce both the direct and indirect effects of roads on wildlife populations.

Southern California and range-wide raccoon gastrointestinal helminth database

Local and global measurements of parasite prevalence and abundance are critical for understanding the dynamics that underlie the diversity, distribution, and evolution of infectious diseases. Here, we present a data set of gut helminths found in (1) raccoons throughout their range, based on primary literature from 1925-2017 and (2) raccoons in Santa Barbara County, California, USA surveyed from 2012 to 2015. The range-wide data set has 1,256 parasite entries from 217 literature sources across three continents and 32 states in the USA. This data set includes a list of all recorded raccoon gut helminths (n = 100) and their presence and prevalence in surveyed raccoon populations. The Santa Barbara data set includes gut helminth data from 182 raccoons from one Southern California County. In addition to the presence and abundance data for 13 parasite species, this data set includes measurements of 7,465 individual raccoon roundworms (Baylisascaris procyonis). For both range-wide and Santa Barbara data sets, we include information on parasite site of infection in host, sampling method, and sample size. We also provide geographic coordinates for infected raccoon populations (range-wide database) and individuals (Santa Barbara). In the associated metadata, we include sampling methods and summary figures for both the range-wide and Santa Barbara raccoon gut helminth records. There are no copyright or proprietary restrictions for research and/or teaching purposes. S. B. Weinstein and J. C. Van Wert contributed equally to this manuscript and are shared first authors.

Infection at an ecotone: cross-system foraging increases satellite parasites but decreases core parasites in raccoons

Ecotones can increase free-living species richness, but little is known about how parasites respond to ecotones. Here, we use parasite communities in raccoons (Procyon lotor) to test the hypothesis that parasite communities can be divided into core and satellite species, each with fundamentally different responses to ecotones. We used published parasite surveys to classify parasites as common core or rare satellite species, and then surveyed raccoons in coastal California to examine how proximity to two aquatic ecotones altered parasite communities. Raccoons near ecotones had more satellite and fewer core parasite species. Specifically, the marine ecotone increased parasite diversity by adding satellite species to a persistent core community, whereas the freshwater ecotone shifted the community from core to satellite species without a net change in parasite richness. We hypothesize that increased parasite richness at the marine ecotone resulted from increased diet diversity, but that raccoons were sinks for some parasites. Increased exposure to rare parasites at ecotones has implications for wildlife health and provides insight into observed associations between ecotones and emerging disease.

Baylisascaris procyonis infection in raccoons: A review of demographic and environmental factors influencing parasite carriage

Baylisascaris procyonis, the roundworm of raccoons (Procyon lotor), is an emerging helminthic zoonosis in North America. Since the larval form is capable of causing neurological disease in more than 150 species of birds and mammals including humans, understanding factors that influence carriage of the parasite by raccoons is important for mitigating risk. This review examines the current literature to identify major demographic and environmental risk factors associated with B. procyonis carriage in wild raccoons. Raccoon age and season of sample collection were most commonly identified as risk factors, with increased prevalence found in juvenile animals and when sample collection occurred in the fall. Human urbanization and agricultural land use were also observed as potential risk factors; however, there are inconsistencies in the direction of influence these risk factors have on the prevalence of infection. Further investigation into the role of environmental risk factors is required to better understand how human activities influence parasite carriage in raccoons. Additionally, future research using multivariable statistical models guided by epidemiological principles to control for confounding variables and identify interaction effects will help clarify the effect of these demographic and environmental factors. Developing a better understanding of the primary risk factors for parasite carriage in raccoons will help identify areas of higher risk for environmental contamination and will aid in the development and refinement of education and management programs to reduce the risk of human exposure.

Molecular phylogenetics and species-level systematics of Baylisascaris

Nucleotide sequences representing nine genes and five presumptive genetic loci were used to infer phylogenetic relationships among seven Baylisascaris species, including one species with no previously available molecular data. These genes were used to test the species status of B. procyonis and B. columnaris using a coalescent approach. Phylogenetic analysis based on combined analysis of sequence data strongly supported monophyly of the genus and separated the species into two main clades. Clade 1 included B. procyonis, B. columnaris, and B. devosi, species hosted by musteloid carnivores. Clade 2 included B. transfuga and B. schroederi from ursids, B. ailuri, a species from the red panda (a musteloid), and B. tasmaniensis from a marsupial. Within clade 2, geographic isolates of B. transfuga, B. schroederi (from giant panda), and B. ailuri formed a strongly supported clade. In certain analyses (e.g., some single genes), B. tasmaniensis was sister to all other Baylisascaris species rather than sister to the species from ursids and red panda. Using one combination of priors corresponding to moderate population size and shallow genetic divergence, the multispecies coalescent analysis of B. procyonis and B. columnaris yielded moderate support (posterior probability 0.91) for these taxa as separate species. However, other prior combinations yielded weak or no support for delimiting these taxa as separate species. Similarly, tree topologies constrained to represent reciprocal monophyly of B. columnaris and B. procyonis individuals (topologies consistent with separate species) were significantly worse in some cases, but not others, depending on the dataset analyzed. An expanded analysis of SNPs and other genetic markers that were previously suggested to distinguish between individuals of B. procyonis and B. columnaris was made by characterization of additional individual nematodes. The results suggest that many of these SNPs do not represent fixed differences between nematodes derived from raccoon and skunk hosts.

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A phylogenetic hypothesis for Baylisascaris species was produced using nine genes.

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Genetic data was generated for two new species- B. devosi and B. tasmaniensis.

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Baylisascaris devosi and B. tasmaniensis were part of a monophyletic Baylisascaris.

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B. procyonis (raccoon) and B. columnaris (skunk) could not be reliably distinguished.

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Established SNPs may not be diagnostic for Baylisascaris from raccoons and skunks.

Seroprevalence of Baylisascaris procyonis Infection among Humans, Santa Barbara County, California, USA, 2014-2016

Baylisascaris procyonis (raccoon roundworm) infection is common in raccoons and can cause devastating pathology in other animals, including humans. Limited information is available on the frequency of asymptomatic human infection. We tested 150 adults from California, USA, for B. procyonis antibodies; 11 were seropositive, suggesting that subclinical infection does occur.

Genetic polymorphism of Baylisascaris procyonis in host infrapopulations and component populations in the Central USA

Baylisascaris procyonis is a nematode of significant concern to public and domestic animal health as well as wildlife management. The population genetics of B. procyonis is poorly understood. To gain insights into patterns of genetic diversity within (infrapopulation level) and among (component population level) raccoon (Procyon lotor) hosts, and specifically to assess the relative importance of indirect and direct transmission of the parasite for explaining observed population structure, we collected 69 B. procyonis from 17 wild raccoons inhabiting five counties in Missouri and Arkansas, USA. Informative regions of mitochondrial (CO1, CO2) and nuclear (28S, ITS2) genes were amplified and the distribution and genetic variability of these genes were assessed within and across raccoons. Concatenation of the CO1 and CO2 mtDNA sequences resulted in 5 unique haplotypes, with haplotype diversity 0.456 ± 0.068. The most common haplotype occurred in 94% of raccoons and 72.5% of B. procyonis. Sequences for 28S rDNA revealed four unique nuclear genotypes, the most common found in 100% of raccoons and 82.6% of B. procyonis. ITS2 genotypes were assessed using fragment analysis, and there was a 1:1 correspondence between 28S and ITS-2 genotypes. Infrapopulation variation in haplotypes and genotypes was high and virtually all hosts infected with multiple sequenced nematodes also harbored multiple haplotypes and genotypes. There was a positive relationship between the size of the analyzed infrapopulation (i.e., the number of nematodes analyzed) and the number of haplotypes identified in an individual. Collectively this work emphasizes the importance of indirect transmission in the lifecycle to this parasite.

Introduced Rats and an Endemic Roundworm: Does Rattus rattus Contribute to Baylisascaris procyonis Transmission in California?

The introduced black rat, Rattus rattus, occurs throughout the native range of the raccoon roundworm, Baylisascaris procyonis, and might incorporate into its life cycle if rats consume parasite eggs, acquire viable infections, and are eaten by raccoons. Although rats forage at raccoon latrines, their role in B. procyonis transmission remains unknown. Here I tested the potential for rats to amplify B. procyonis transmission in California by surveying wild rodents for B. procyonis and conducting scavenger trials with the use of motion-activated cameras. Rattus rattus were infected with B. procyonis at intensities more than 100 times greater than that of co-occurring native Reithrodontomys megalotis and Peromyscus maniculatus. Rodent carcasses were scavenged by opossums, skunks, and raccoons, suggesting that these rodents, particularly R. rattus, contribute to B. procyonis transmission in this coastal California ecosystem.