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.     

The role of medium-sized mammals as reservoirs of Borrelia burgdorferi in southern New York

The ability of raccoons (Procyon lotor), striped skunks (Mephitis mephitis) and opossums (Didelphis virginiana) to serve as reservoirs of Borrelia burgdorferi, the spirochetal agent of Lyme disease, was compared with that of white-footed mice (Peromyscus leucopus). Twenty-eight (28) medium-sized mammals and 34 white-footed mice were captured in Westchester County, New York (USA) in summer 1986. Animals were caged over pans of water for 1 to 2 days to recover engorged tick larvae (Ixodes dammini) that detached from the hosts after feeding. With the exception of mice, numbers of engorged tick larvae recovered exceeded those counted during initial examinations of the hosts by 30% (opossums) to nearly 90% (raccoons). Newly-molted nymphal ticks derived from the engorged larvae were examined for the presence of spirochetes by darkfield microscopy. Percentage infection was 5% (n = 22) for ticks from skunks and 14% (n = 191) for ticks from raccoons. None of 24 nymphs from larvae that fed on opossums survived long enough for spirochete examination. By comparison, 40% (n = 72) of nymphs from larvae which fed on white-footed mice were infected. Of the individual hosts from which molted nymphs had fed as larvae, 67% of mice, 33% of skunks, and 55% of raccoons produced spirochete-positive ticks.     

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.     

Epizootiology of an outbreak of cerebrospinal nematodiasis in cottontail rabbits and woodchucks

An epizootic of cerebrospinal nematodiasis in cottontail rabbits (Sylvilagus floridanus) and woodchucks (Marmota monax) caused by Baylisascaris procyonis larvae followed the establishment of an ascarid-infected raccoon (Procyon lotor) population in a woodlot. Five of seven raccoons examined from the woodlot harbored ascarids, with one heavily infected animal shedding approximately 27,500 eggs per gram of feces. A laboratory-reared cottontail rabbit developed neurologic disease due to larval migration 80 days after infection with B. procyonis eggs from the raccoons.     

Frequency of deposition and location of Baylisascaris procyonis eggs in raccoon feces

Baylisascaris procyonis is a large ascarid nematode found in the small intestine of raccoons (Procyon lotor). Infection with larvae of B. procyonis can produce visceral, ocular, and neural larval migrans in humans. Infected raccoons can shed millions of eggs a day in their feces. However, it is unknown whether eggs are consistently shed or whether eggs occur at irregular intervals by the population of female nematodes within a host. We trapped, infected, and collected daily fecal samples from 11 raccoons maintained in captivity. Eggs from B. procyonis were obtained from anterior, central, and posterior sections of raccoon feces, isolated by flotation, and quantified under 100× magnification. Naturally infected raccoons were collected and used as a comparison with the experimentally infected group. All raccoons in the experimental group (n=11) became infected with B. procyonis after consuming one infected mouse. Additionally, differential egg deposition rates were observed among individual raccoons from the experimental and naturally infected groups. Mean number of eggs per gram of feces (means±SE) was 16,563±4,321, which was less than previously reported for the species. However, no differences (F(2,30)=0.84, P=0.45) were noted in mean number of eggs per gram of feces among fecal sections. Wildlife biologists, veterinarians, health officials, and researchers of B. procyonis should collect daily fecal samples for a minimum of 3 days before identifying a raccoon as negative for B. procyonis infection. However, it does not matter where within the fecal matter the sample is obtained.     

Implications of raccoon latrines in the epizootiology of baylisascariasis.

Raccoons (Procyon lotor) frequently establish defecation sites, termed latrines, on large logs, stumps, rocks, and other horizontally oriented structures/surfaces. These latrines are important foci of infective eggs of Baylisascaris procyonis, a nematode parasite of raccoons which is pathogenic to numerous species of mammals and birds. To examine the role of raccoon latrines in this animal-parasite interaction, we documented animal visitations to raccoon latrines in two large forested tracts and two woodlots in Indiana (USA) during 1994 and 1995. Species richness of vertebrate visitors did not differ between sites or years, but species composition differed by site and year. Fourteen mammal and 15 bird species were documented visiting raccoon latrines. Small granivorous mammals, including white-footed mice (Peromyscus leucopus), eastern chipmunks (Tamias striatus), and tree squirrels (Sciurus carolinensis, S. niger, Tamiasciurus hudsonicus) were the most common visitors to latrine sites. White-footed mice, chipmunks, white-breasted nuthatches (Sitta carolinensis), and opossums (Didelphis virginiana) were photographed foraging on undigested seeds in raccoon feces. Active foraging at latrines also was shown experimentally; seeds embedded in raccoon feces were removed at a greater rate at latrine sites than at nonlatrines. We conclude that raccoon latrines are visited routinely by a variety of vertebrates, especially small granivorous rodents and birds which forage for seeds in raccoon feces, and that raccoon latrines are probable sites of transmission of B. procyonis to susceptible mammals and birds.     

Prevalence and intensity of Angiostrongylus cantonensis in freshwater snails in relation to some ecological and biological factors

The purpose of the study was to record different intermediate hosts of A. cantonensis and to determine the infection prevalence and intensity of this parasite in freshwater snails in relation to some ecological and biological factors. The study was conducted at Al-Salam irrigation Canal and Al-Abtal village (north Sinai) for one year, from March 2004 to February 2005. Thirteen species of freshwater snails of nine families were examined for A. cantonensis infection. Six species were found infected with A. cantonensis larvae. These species were L. carinatus, C. bulimoides, C. cyclostomoides, B. alexandrina, L. natalensis and M. tuberculta. The infection prevalence of A. cantonensis in the examined snails ranged from 0.63 to 2.24%. L. carinatus snail had the highest prevalence, mean abundance and mean intensity of A. cantonensis infection. Positive correlations were found between both prevalence and mean abundance of A. cantonensis and host size in L. carinatus and M. tuberculata. Negative correlations were detected between salinity and prevalence, mean abundance and mean intensity of larvae of A. cantonensis. The results demonstrated seasonal and spatial variation in the prevalence, mean abundance and mean intensity of infection among examined snails. In this study, A. cantonensis larvae were found in a wide range of freshwater snails and M. tuberculata snail was recorded as a new intermediate host for the first time. In conclusion, further investigations in other areas and controlled laboratory experiments of infection approaches are required to evaluate the possible threat of this parasite on humans.     

Distribution, prevalence, and genetic characterization of Baylisascaris procyonis in selected areas of Georgia

Baylisascaris procyonis is an intestinal nematode of raccoons (Procyon lotor) that can cause fatal larval migrans in numerous species of birds and mammals, including humans. Although this parasite has historically been absent in the southeastern United States, it has been found in isolated regions in the Appalachian Mountains and was recently documented in DeKalb County, Georgia. The first objective of the current study was to investigate the distribution and prevalence of B. procyonis in selected populations of raccoons in Georgia. Intestinal tracts of 312 raccoons from 25 Georgia counties were examined for B. procyonis. The only county where B. procyonis was detected was Clarke County, where 12 of 116 (10.3%) raccoons were infected. In Clarke County, significantly more juveniles (P = 0.049) were infected compared with adults, and no differences in prevalence were noted by sex, season of capture, or land use (rural vs. urban); however, significantly (P = 0.0370) higher worm burdens were found in infected raccoons from urban/suburban locations compared with rural areas. In addition, Toxascaris leonina , a morphologically similar ascarid, was found in 3 raccoons from Clarke County (n = 2) and Morgan County (n = 1). A second objective was to determine if sequence polymorphisms were associated with B. procyonis from different geographic regions. Because sequences from a single worm from Japan had been entered into GenBank, we obtained nematodes from Kentucky and Texas for comparison with our samples from Georgia. Sequence analysis of the 18S and 5.8S rRNA genes and the internal transcribed spacer (ITS) -1 and ITS-2 regions confirmed Georgia samples were B. procyonis. Although several polymorphic bases were observed within both ITS regions, none was associated with a particular geographic location. These data indicate that the distribution of B. procyonis within Georgia is increasing and only limited genetic variation is present in the rRNA and ITS gene regions among B. procyonis from the southern United States and introduced populations in Japan.     

Male hosts are responsible for the transmission of a trophically transmitted parasite, Pterygodermatites peromysci, to the intermediate host in the absence of sex-biased infection

Field studies have identified that male-biased infection can lead to increased rates of transmission, so we examined the relative importance of host sex on the transmission of a trophically transmitted parasite (Pterygodermatites peromysci) where there is no sex-biased infection. We experimentally reduced infection levels in either male or female white-footed mice (Peromyscus leucopus) on independent trapping grids with an anthelmintic and recorded subsequent infection levels in the intermediate host, the camel cricket (Ceuthophilus pallidipes). We found that anthelmintic treatment significantly reduced the prevalence of infection among crickets in both treatment groups compared with the control, and at a rate proportional to the number of mice de-wormed, indicating prevalence was not affected by the sex of the shedding definitive host. In contrast, parasite abundance in crickets was higher on the grids where females were treated compared with the grids where males were treated. These findings indicate that male hosts contribute disproportionately more infective stages to the environment and may therefore be responsible for the majority of parasite transmission even when there is no discernable sex-biased infection. We also investigated whether variation in nematode length between male and female hosts could account for this male-biased infectivity, but found no evidence to support that hypothesis.     

Land Use and Wetland Spatial Position Jointly Determine Amphibian Parasite Communities

Land use change is one of the most commonly cited contributing factors to infectious disease emergence, yet the mechanisms responsible for such changes and the spatial scales at which they operate are rarely identified. The distributions of parasites with complex life cycles depend on interactions between multiple host species, suggesting the net effects of land use on infection patterns may be difficult to predict a priori. Here, we used an information-theoretic approach to evaluate the importance of land use and spatial scale (local, watershed, and regional) in determining the presence and abundance of multi-host trematodes of amphibians. Among 40 wetlands and 160 hosts sampled, trematode abundance, species richness, and the presence and abundance of pathogenic species were strongly influenced by variables at the watershed and regional scales. Based on model averaging results, overall parasite richness and abundance were higher in forested wetlands than in agricultural areas; however, this pattern was influenced by a wetland's proximity to the Mississippi Flyway at the regional scale. These patterns likely reflect the activity of trematode definitive hosts, such as mammals and especially birds, such that infections decreased with increasing distance from the Mississippi River. Interestingly, despite lower mean infections, agricultural wetlands had higher variances and maximum infections. At the wetland scale, phosphorus concentrations and the abundances of intermediate hosts, such as snails and larval amphibians, positively affected parasite distributions. Taken together, these results contribute to our understanding of how altered landscapes affect parasite communities and inform further research on the environmental drivers of amphibian parasite infections.     

Spatial and temporal dispersion of immature Ixodes dammini on Peromyscus leucopus in northwestern Illinois.

Infestation by immature Ixodes dammini and infection by Borrelia burgdorferi of the white-footed mouse Peromyscus leucopus were studied in Castle Rock State Park in northwestern Illinois during June-October 1990. Prevalence and intensity of infestation of larvae on mice were highest in August with a smaller peak in early June. The distribution of larvae on mice was highly aggregated during each of the sampling periods. Aggregation appears to be the result of a series of nonrandom successful attachments by single larvae, rather than of simultaneous attachment by clumps of larvae. Infection rate of mice by B. burgdorferi averaged 21.4% with a peak of 28.6% in August. A comparison of the numbers of attached immature ticks collected from mice and of questing ticks collected through dragging indicated that the larvae-to-nymph ratio was higher on mice than on drags. Given the low total numbers of nymphs collected from mice, this suggests a potential role for other hosts of I. dammini nymphs in northwestern Illinois.     

First outbreak of Baylisascaris procyonis larva migrans in rabbits in Japan

A syndrome of progressive neurological signs was noticed in rabbits (Oryctolagus cuniculus) kept in a small wildlife park in mid-July 2000. Three out of 12 common raccoons (Procyon lotor) kept in this park were infected with Baylisascaris procyonis, and the larvae were found from affected rabbits. This outbreak is the first proven B. procyonis larva migrans in Japan, and the potential risk of serious zoonosis by this ascarid species should be considered by pet owners, veterinarians, physicians and public health authorities in this country as in North America where raccoons are endemic.     

Survey of raccoons on Key Largo, Florida, USA, for Baylisascaris procyonis

Numbers of the endangered Key Largo woodrat (KLWR; Neotoma floridana smalli) have been declining for at least 25 yr. The raccoon (Procyon lotor) roundworm, Baylisascaris procyonis, has been found to have an adverse effect on the survival of Alleghany woodrats (N. magister). High densities of raccoons can exacerbate this problem by increasing the amount of feces containing viable eggs of B. procyonis available to woodrats. In 2002, 64 fecal samples were collected and examined for eggs of B. procyonis from >32 raccoons within the KLWR's known range on Key Largo, Florida, USA. All samples were negative for eggs of B. procyonis. Raccoon density in this area was approximately 0.62 raccoons/ha. Despite this high density of raccoons, B. procyonis does not appear to be a threat to the KLWR population.     

A Hierarchical Analysis of Habitat Selection by Raccoons in Northern Indiana

Abstract: Although numerous studies have examined habitat use by raccoons (Procyon lotor), information regarding seasonal habitat selection related to resource availability in agricultural landscapes is lacking for this species. Additionally, few studies using radiotelemetry have investigated habitat selection at multiple spatial scales or core-use areas by raccoons. We examined seasonal habitat selection of 55 (31 M, 24 F) adult raccoons at 3 hierarchical orders defined by the movement behavior of this species (second-order home range, second-order core-use area, and third-order home range) in northern Indiana, USA, from May 2003 to June 2005. Using compositional analysis, we assessed whether habitat selection differed from random and ranked habitat types in order of selection during the crop growing period (season 1) and corn maturation period (season 2), which represented substantial shifts in resource availability to raccoons. Habitat rankings differed across hierarchical orders, between seasons within hierarchical orders, and between sexes within seasons; however, seasonal and intersexual patterns of habitat selection were not consistent across hierarchical orders of spatial scale. When nonrandom utilization was detected, both sexes consistently selected forest cover over other available habitats. Seasonal differences in habitat selection were most evident at the core-area scale, where raccoon selection of agricultural lands was highest during the maturation season when corn was available as a direct food source. Habitat use did not differ from availability for either sex in either season at the third-order scale. The selection of forest cover across both seasons and all spatial orders suggested that raccoon distribution and abundance in fragmented landscapes is likely dependent on the availability and distribution of forest cover, or habitats associated with forest (i.e., water), within the landscape. The lack of consistency in habitat selection across hierarchical scales further exemplifies the need to examine multiple biological scales in habitat-selection studies.     

Large-scale patterns of host use by parasites of freshwater fishes

Organisms that are abundant locally in a habitat patch are commonly observed to be frequent regionally, or among patches. In parasites, species present in high numbers in host individuals are also present in many individuals in the host population. On a larger scale, however, when host species are considered as patches, we may expect the opposite pattern because of the cost of producing mechanisms to evade the immune responses of several host species. Thus parasite species exploiting many host species may achieve lower average abundance in their hosts than parasite species exploiting fewer host species. This prediction was tested with data from 188 species of metazoan parasites of freshwater fish, using a comparative approach that controlled for study effort and phylogenetic influences. A negative correlation was found between the number of host species used by parasites and their average abundance in hosts, measured as either prevalence or intensity of infection. There was no evidence that parasite species fall into distinct categories based on abundance patterns, but rather that they fall along a continuum ranging from a generally low abundance in many host species, to a generally high abundance in few host species. These results applied to both ecto- and endoparasites. The pattern observed suggests the existence of a trade-off between how many host species a parasite can exploit and how well it does on average in those hosts.     

Observations on the seasonal prevalence, pathology and transmission of Dracunculus insignis (Nematoda: Dracunculoidea) in the raccoon (Procyon lotor (L.) in Ontario.

Lesions due to Dracunculus insignis in the legs of raccoons (Procyon lotor) in southern Ontario occur seasonally as most larvigerous females emerge in the spring and early summer (April-June). The pathology of dracunculiasis in the raccoon is described and the transmission of the parasite in the wild is discussed with respect to seasonality and local agricultural practices. Crayfish, fishes and frogs (including tadpoles) were given infective third-stage larvae of D. insignis to test their suitability as paratenic hosts. Most of the larvae fed to adult Rana pipiens and R. clamitans were recovered from the somatic musculature. Larvae had increased in size and were highly infective to raccoons.     

Fear of feces? Tradeoffs between disease risk and foraging drive animal activity around raccoon latrines

Fear of predation alters prey behavior, which can indirectly alter entire landscapes. A parasite‐induced ecology of fear might also exist if animals avoid parasite‐contaminated resources when infection costs outweigh foraging benefits. To investigate whether animals avoid parasite contaminated sites, and if such avoidance balances disease costs and foraging gains, we monitored animal behavior at raccoon latrines – sites that concentrate both seeds and pathogenic parasite eggs. Using wildlife cameras, we documented over 40 potentially susceptible vertebrate species in latrines and adjacent habitat. Latrine contact rates reflected background activity, diet preferences and disease risk. Disease‐tolerant raccoons and rats displayed significant site attraction, while susceptible birds and small mammals avoided these high‐risk sites. This suggests that parasites, like predators, might create a landscape of fear for vulnerable hosts. Such non‐consumptive parasite effects could alter disease transmission, population dynamics, and even ecosystem structure.     

Capillaria procyonis (Nematoda: Trichuroidea) eggs from the tongue of the raccoon (Procyon lotor)

During an investigation to determine the prevalence and intensity of larvae of Trichinella spiralis in raccoons (Procyon lotor), unembryonated capillariid-type eggs were found routinely in the sediment resulting from 1% pepsin-HCl acid digests of the tongue. The sediment from 36 (90%) of the 40 tongue digests examined contained these capillariid-type eggs. Mean measurements of egg width and length were 25 +/- 2 microns and 62 +/- 2 microns, respectively. In addition, the surface of the egg shell had a pitted appearance. Adult parasites were not found in any of the tongue digests. The egg measurements and surface topography agree with what has been described previously and are tentatively identified as Capillaria procyonis. The detection of C. procyonis eggs in the present report indicates that this parasite inhabits the epithelial lining of the raccoon tongue, in addition to the esophagus, and that eggs expelled by females are deposited in the tracts these parasites create as they migrate.     

The arrangement of resources in patchy landscapes: effects on distribution, survival, and resource acquisition of chironomids

The spatial arrangement of resources in patchy habitats influences the distribution of individuals and their ability to acquire resources. We used Chironomus riparius, a ubiquitous aquatic insect that uses leaf particles as an important resource, to ask how the dispersion of resource patches influences the distribution and resource acquisition of mobile individuals in patchy landscapes. Two experiments were conducted in replicated laboratory landscapes (38×38 cm) created by arranging sand and leaf patches in a 5×5 grid so that the leaf patches were either aggregated or uniformly dispersed in the grid. One-day-old C. riparius larvae were introduced into the landscapes in one of three densities (low, medium, high). In experiment 1, we sampled larvae and pupae by coring each patch in each landscape 3, 6, 12, or 24 days after adding larvae. In experiment 2, emerging adults were collected daily for 42 days from each patch in each landscape. In aggregated landscapes, individuals were aggregated in one patch type or the other during a particular developmental stage, but the ”preferred” type changed depending on developmental stage and initial density. Adult emergence was lower by about 30% in all aggregated landscapes. In dispersed landscapes, individuals used both types of patch throughout their life cycles at all initial densities. Thus, patch arrangement influences the distribution of mobile individuals in landscapes, and it influences resource acquisition even when average resource abundance is identical among landscapes. Regardless of patch arrangement, high initial density caused accumulation of early instars in edge patches, 75% mortality of early instars, a 25% increase in development time, and a 60% reduction in adult emergence. Because mortality was extremely high among early-instar larvae in high-density treatments, we do not have direct evidence that the mechanism by which patch arrangement operates is density dependent. However, the results of our experiments strongly suggest that dispersion of resource patches across a landscape reduces local densities by making non-resource patches available for use, thereby reducing intraspecific competition. Received: 20 July 1999 / Accepted: 28 January 2000     

Lost and found: Helminths infecting invasive raccoons introduced to Italy

North American raccoons (Procyon lotor) have been introduced to several European countries, where they may represent a sanitary threat as hosts of several pathogens such as the zoonotic ascarid Baylisascaris procyonis. We carried out parasitological analysis on raccoons introduced to Italy to verify whether the species had carried along B. procyonis or any other gastro-intestinal helminths that may threaten humans, livestock or native wildlife. We examined 64 raccoons culled in Northern Italy during control activities and 3 roadkills opportunistically sampled from a separate population located in central Italy. Helminths were collected from the gastro-intestinal tract through standard parasitological techniques and identified based on a combination of morphology and molecular methods. Overall, examined raccoons showed a poor parasitic fauna, with almost 30% of individuals free of any helminth infection. The most prevalent species were the nematodes Strongyloides procyonis (26.9%), Aonchotheca putorii (25.4%) and Porrocaecum sp. (19.4%). Plagiorchis sp. trematodes were also common (13.4%), whereas cestodes were scarcely represented. With the exception of S. procyonis introduced from North America, all the other identified taxa have either a Eurasian or a wide Holarctic distribution. Despite not finding any B. procyonis in the examined raccoons, passive surveillance for this parasite should be implemented, especially in Tuscany, since the limited host sample examined in the present survey does not allow to exclude its presence.