Antimicrobial resistance in Escherichia coli isolates from raccoons (Procyon lotor) in Southern Ontario, Canada

We conducted a cross-sectional study to determine the prevalence of antimicrobial resistance (AMR) in fecal Escherichia coli isolates from raccoons (Procyon lotor) living in Ontario, Canada. From June to October 2007, we trapped raccoons in three areas: one primarily urban site around Niagara, one primarily rural site north of Guelph, and one at the Toronto Zoo. In addition, we conducted a longitudinal study at the Toronto Zoo site to investigate the temporal dynamics of fecal E. coli and AMR in raccoons. Reduced susceptibility to ≥1 antimicrobial agent was detected in E. coli isolates from 19% of 16 raccoons at the urban site, 17% of 29 raccoons from the rural site, and 42% of 130 samples collected from 59 raccoons at the zoo site. Raccoons from the zoo site were significantly more likely to shed E. coli with reduced susceptibility to ≥1 antimicrobial agent than animals from the rural site (odds ratio [OR], 3.41; 95% confidence interval [CI], 1.17 to 12.09; P = 0.02). Resistance to expanded-spectrum cephalosporins (and the associated bla(CMY-2) gene) was detected in two animals from the zoo site and one animal from the rural site. Serotyping and pulsed-field gel electrophoresis analysis show that raccoons on the zoo grounds harbor a diverse assemblage of E. coli, with rapid bacterial turnover within individuals over time. Our study indicates that raccoons may shed resistant bacteria of public health significance and that raccoons have the potential to disseminate these bacteria throughout their environment.     

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.     

Epidemiology of Antimicrobial Resistance in Escherichia coli Isolates from Raccoons (Procyon lotor) and the Environment on Swine Farms and Conservation Areas in Southern Ontario

Antimicrobial resistance is a global threat to livestock, human and environmental health. Although resistant bacteria have been detected in wildlife, their role in the epidemiology of antimicrobial resistance is not clear. Our objective was to investigate demographic, temporal and climatic factors associated with carriage of antimicrobial resistant Escherichia coli in raccoons and the environment. We collected samples from raccoon paws and feces and from soil, manure pit and dumpsters on five swine farms and five conservation areas in Ontario, Canada once every five weeks from May to November, 2011–2013 and tested them for E. coli and susceptibility to 15 antimicrobials. Of samples testing positive for E. coli, resistance to ≥ 1 antimicrobials was detected in 7.4% (77/1044; 95% CI, 5.9–9.1) of raccoon fecal samples, 6.3% (23/365; 95% CI, 4.0–9.3) of paw samples, 9.6% (121/1260; 8.0–11.4) of soil samples, 57.4% (31/54; 95% CI, 43.2–70.8) of manure pit samples, and 13.8% (4/29; 95% CI, 3.9–31.7) of dumpster samples. Using univariable logistic regression, there was no significant difference in the occurrence of resistant E. coli in raccoon feces on conservation areas versus farms; however, E. coli isolates resistant to ≥ 1 antimicrobials were significantly less likely to be detected from raccoon paw samples on swine farms than conservation areas and significantly more likely to be detected in soil samples from swine farms than conservation areas. Resistant phenotypes and genotypes that were absent from the swine farm environment were detected in raccoons from conservation areas, suggesting that conservation areas and swine farms may have different exposures to resistant bacteria. However, the similar resistance patterns and genes in E. coli from raccoon fecal and environmental samples from the same location types suggest that resistant bacteria may be exchanged between raccoons and their environment.     

Acceptance of baits for delivery of oral rabies vaccine to raccoons.

During 1993-96 the Ontario Ministry of Natural Resources (Canada) implemented a research project to evaluate the efficacy of three candidate baits to deliver oral rabies vaccine to wild raccoons (Procyon lotor). Extensive field testing revealed that raccoon acceptance of Sugar-Vanilla baits (SV) at densities of 200/km2 and 400/km2, hand-placed in urban habitats of Scarborough (Ontario) during 1993, was 74% and 82%, respectively. Raccoon density in those areas averaged 11/km2. Aerial placement of SV baits in rural habitats in Barrie (Ontario) during 1993 and 1994, yielded raccoon acceptance levels of 58% with a density of 100 baits/km2, 59% at 75 baits/km2, and 47% at 50 baits/km2. Raccoon acceptance of SV baits was significantly lower in areas baited at the density of 50/km2. Acceptance of Cheese baits (CH) at a density of 75 baits/km2 was 52%. During 1996 trials in Barrie, modified SV baits with blister packs protruding through the matrix yielded raccoon acceptance values of 51% at a bait density of 54/km2, whereas acceptance of regular SV baits was 39% at a density of 51 baits/km2. Pooling of bait acceptance data for all years revealed that bait acceptance was highest for adult male raccoons. Raccoon density in rural habitats (Barrie, Ontario) where the studies took place, averaged 11-13/km2. Puncture and impact testing of blister packs in baits suggested that they would adequately serve as a vehicle to contain oral rabies vaccine for delivery to raccoons via baits.     

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.     

Raccoon Density and Movements After Population Reduction to Control Rabies

ABSTRACT Population reduction (PR) and trap-vaccinate-release (TVR) were used to control an outbreak of the raccoon (Procyon lotor) variant of rabies in Ontario, Canada, during 1999. Raccoon density declined significantly following PR; however, density increased significantly 9–10 months post-PR. Recolonization of PR areas with raccoons marked in TVR areas was very low with only 1.8% (32/1,759) of those raccoons dispersing into PR areas during 1999–2000. In addition, the number of raccoons dispersing from TVR areas into PR areas was not significantly greater than the number of raccoons dispersing into treatment areas where population reduction had not been implemented during 1999–2000. Raccoon movements in this study, determined by mark-recapture, averaged < 4.0 km during 1999–2000 and did not differ among treatments (with or without PR). In summary, there was not a mass exodus of raccoons from TVR areas to PR areas during 1999–2000, suggesting there was not an immediate, dramatic, vacuum effect drawing raccoons into areas devoid of raccoons due to PR. However, one year post-PR, raccoon populations were near or above pre-PR densities (due to a high reproductive rate of resident raccoons), suggesting that PR would have to be an annual event if rabies is not eliminated from an area.     

Land use associations and changes in population indices of urban raccoons during a rabies epizootic

Land use associations and changes in population indices were assessed for an urban population of raccoons (Procyon lotor) in Baltimore, Maryland (USA), from January 1984 to December 1987. Records were examined for 1,458 raccoons trapped alive and removed dead from city streets during, and after, the peak of a rabies epizootic. The distribution of raccoons was associated with single-unit residential areas primarily along the northern and western perimeter of the city. Beginning in March 1985 an ending in May 1987, an epizootic of raccoon rabies spread through Baltimore, ultimately resulting in the identification of 95 rabid raccoons. Within the study interval, annual numbers of trapped raccoons remained stable from 1984 to 1986, before showing a marked decline in 1987. The number of raccoons removed as vehicle mortalities (road-kills) varied little from 1984-1985 but declined in the last 2 yr of study. Numbers of other road-killed species did not decrease concurrently, suggesting a specific decrease in the urban raccoon population. The rabies epizootic, in conjunction with the increased city and private control, appears to have contributed to a decline in the number of raccoons in Baltimore.     

Landscape modelling spatial bottlenecks: implications for raccoon rabies disease spread

A landscape genetic simulation modelling approach is used to understand factors affecting raccoon rabies disease spread in southern Ontario, Canada. Using the Ontario Rabies Model, we test the hypothesis that landscape configuration (shape of available habitat) affects dispersal, as indicated by genetic structuring. We simulated range expansions of raccoons from New York into vacant landscapes in Ontario, in two areas that differed by the presence or absence of a landscape constriction. Our results provide theoretical evidence that landscape constriction acts as a vicariant bottleneck. We discuss implications for raccoon rabies spread.     

Behavior, movements, and demographics of rabid raccoons in Ontario, Canada: management implications

During 1999-2003, 127 cases of raccoon variant rabies were reported in raccoons (Procyon lotor) and striped skunks (Mephitis mephitis) in Ontario, Canada. Raccoons accounted for 98% (125/127) of the reported cases with behaviors/conditions including aggression, fighting with dogs, ataxia, vocalizations, appearance of being sick, and the presence of porcupine (Erethizon dorsatum) quills. Seventy-eight percent of the rabid raccoons were adults. Juveniles were underrepresented (22%) compared with the adult/juvenile ratios found in nonrabid Ontario raccoon populations. Of the known aged raccoons, 83% were < or = 3 yr of age, and 22% of the rabid adult female raccoons had evidence of having had a litter during the year in which they were found to be rabid. The majority of rabid raccoons were reported during the fall, winter, and spring, suggesting a relationship between raccoon behavioral activities such as denning and breeding and the timing of rabies outbreaks. Multiple cases of raccoon rabies occurred at several barns, suggesting that those structures serve as focal points of rabies transmission as a result of denning activities. Movements of five rabid raccoons (range 1,564-4,143 m) were not different from movements of nonrabid raccoons in Ontario. Sixty-six percent of the rabid animals were submitted by government staff, stressing the importance of those agencies in rabies control and surveillance operations. Increased knowledge of the behaviors of rabid raccoons should assist in the development of management strategies for rabies.     

Phenotypic and molecular typing of Salmonella strains reveals different contamination sources in two commercial pig slaughterhouses

This study aimed to define the origin of Salmonella contamination on swine carcasses and the distribution of Salmonella serotypes in two commercial slaughterhouses during normal activity. Salmonellae were isolated from carcasses, from colons and mesenteric lymph nodes of individual pigs, and from the slaughterhouse environment. All strains were serotyped; Salmonella enterica serotype Typhimurium and Salmonella enterica serotype Derby isolates were additionally typed beyond the serotype level by pulsed-field gel electrophoresis (PFGE) and antibiotic resistance profiling (ARP); and a subset of 31 serotype Typhimurium strains were additionally phage typed. PFGE and ARP had the same discriminative possibility. Phage typing in combination with PFGE could give extra information for some strains. In one slaughterhouse, 21% of the carcasses were contaminated, reflecting a correlation with the delivery of infected pigs. Carcass contamination did not result only from infection of the corresponding pig; only 25% of the positive carcasses were contaminated with the same serotype or genotype found in the corresponding feces or mesenteric lymph nodes. In the other slaughterhouse, 70% of the carcasses were contaminated, and only in 4% was the same genotype or serotype detected as in the feces of the corresponding pigs. The other positive carcasses in both slaughterhouses were contaminated by genotypes present in the feces or lymph nodes of pigs slaughtered earlier that day or from dispersed sources in the environment. In slaughterhouses, complex contamination cycles may be present, resulting in the isolation of many different genotypes circulating in the environment due to the supply of positive animals and in the contamination of carcasses, probably through aerosols.     

Age,but not Sex or Genetic Relatedness,Shapes Raccoon Dominance Patterns

Raccoons are generally regarded as solitary, yet several studies have found that raccoons frequently form social affiliations. One benefit to sociality in many mammal species is that relatives and close associates can form coalitions against third parties during agonistic encounters. We tested whether raccoon dominance patterns were influenced by age, sex, genetic relatedness, and association patterns at two anthropogenic feeding stations in an urban forest. We found that genetic relatedness had no significant effect on patterns of agonism at one of the feeding stations. At the second feeding station, raccoons were more likely to act aggressively toward close relatives, which is opposite of the predicted pattern. However, when we controlled for the number of times raccoons arrived at feeding stations in close proximity, the effect of relatedness on dominance patterns was not significant at either feeding station. These results suggest that relatedness plays little or no role in shaping dominance patterns of raccoons. Older raccoons were ranked significantly higher in the dominance hierarchies regardless of sex. This pattern leads us to conclude that age is the primary factor driving the outcome of aggressive interactions in raccoons at our study site. Despite frequent social interactions at the study site, the patterns of raccoon dominance more closely resemble patterns found in solitary animals. To confirm the generality of these results and to better understand the evolution of raccoon social behavior, similar studies need to be undertaken in other raccoon populations.     

Differential permeability of rivers to raccoon gene flow corresponds to rabies incidence in Ontario, Canada

The correlation of landscape features with genetic discontinuities reveals barriers to dispersal that can contribute to understanding present and future spread of wildlife diseases. This knowledge can then be used for targeting control efforts. The impact of natural barriers on raccoon dispersal was assessed through genetic analysis of samples from two regions, Niagara ( N  = 666) and St. Lawrence ( N  = 802). These areas are transected by major rivers and are at the northern front of a raccoon rabies epizootic. Genetic clusters were identified in each region using Bayesian clustering algorithms. In the Niagara region, two clusters were identified corresponding to either side of the Niagara River. For the St. Lawrence region, spatially congruent clusters were not identified, despite the presence of the intervening St. Lawrence River. These genetic data are consistent with raccoon rabies incidence data where rabies has been detected across the St. Lawrence River in Ontario while no cases have been detected in Ontario across the Niagara River. This is despite expectations of rabies incidence in Niagara before the St. Lawrence based on the progression of rabies from New York. The results from the two regions suggest different permeabilities to raccoons between New York and Ontario that may be attributed to the rivers. However, other factors have also been explored that could contribute to this difference between these study sites including the shape of the landscape and resource distribution.     

Prevalence of tetracycline and rabies virus antibody in raccoons, skunks, and foxes following aerial distribution of V-RG baits to control raccoon rabies in Ontario, Canada

More than 3.6 million baits containing a recombinant vaccinia virus-rabies glycoprotein (V-RG) oral rabies vaccine were aerially or hand-distributed during 1999-2006 in an approximate 4,000-9,000 km(2) area of eastern Ontario, Canada, as part of a multitactic approach to control the raccoon variant of rabies. The efficacy of the program was assessed through the collection and testing of > 6,900 animals for bait acceptance and rabies virus-specific antibodies. Raccoon acceptance of rabies vaccine baits was significantly greater (71-83% ) in areas baited at a density of 150 baits/km(2) compared to areas baited at 75 baits/km(2) (26-58% ), and more raccoons consumed vaccine baits in areas baited with a flight line spacing of 0.75 km (45.3% [321/708]) than with a spacing of 1.5 km (33.8% [108/320]). In addition, greater numbers of raccoons consumed vaccine baits during a drop in September (52.7% [213/404]) as opposed to a June bait drop (34.6% [216/624]). Seropositivity rates for raccoons ranged between 7% and 28% in areas baited at 75/km(2) and 10% to 27% in areas baited at 150/km(2) with statistical differences varying among years and treatments. The last case of raccoon-variant rabies reported in Ontario was in September 2005. The control of raccoon rabies in Ontario has resulted in an estimated $6M to $10 M Cdn annual savings in rabies-associated costs.     

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.     

Prerequisites for oral immunization of free-ranging raccoons (Procyon lotor) with a recombinant rabies virus vaccine: study site ecology and bait system development.

A model baiting system suitable for the delivery of an oral rabies vaccine to free-ranging raccoons (Procyon lotor) was developed and tested on barrier islands in South Carolina (USA). Features of barrier island physiography and ecology were studied relative to selective bait deployment and site biosecurity. Capture-mark-recapture data were obtained from 228 raccoons. Raccoon density estimates, using a modified census assessment technique, were one raccoon per 1.8 to 2.7 ha. Mean (+/- SE) and range home area estimates of radio-collared raccoons were 84 (+/- 15.6) ha (27 to 176 ha) by a minimum convex polygon method and 138 (+/- 22.8) ha (43 to 241 ha), by a harmonic mean transformation method. Habitat utilization determinations of radio-collared raccoons were conducted to identify study areas to potentially maximize selectivity of bait towards raccoons and to reduce the absolute number of baits deployed. Island raccoons showed a habitat preference for maritime forest, maritime shrub and marsh areas. Additionally, there was no evidence of inter-island or mainland exchange of ear-tagged or radio-collared raccoons. A disease and mortality survey was conducted to identify baseline pathology and incidental lesions in the target raccoon population, prior to actual vaccination initiation. Thirty-eight percent of 30 clinically suspect raccoons sampled had intracytoplasmic eosinophilic inclusions diagnostic of canine distemper; no other lesions suggestive of viral etiologies were found. Serological surveys for raccoon poxvirus and rabies virus antibodies were negative. Antibody titers to canine adenovirus 1 and 2 indicated a moderate level of exposure (approximately 10 to 16%) in the raccoon population. Overall, 93 to 100% of placebo baits were consistently disturbed by 7 days post-bait deployment, and bait acceptance rates by raccoons ranged from 49 to 85%, by using a modular systems approach to select the optimum combination of bait attractant, biomarker, matrix, density, and distribution. These results suggest that a large proportion (up to 85%) of a free-ranging island raccoon population can be selectively and safely targeted, marked and monitored utilizing a proposed oral bait delivery system for recombinant or other rabies vaccines.     

Rabies in vaccinated raccoons from Ontario, Canada

From 1999 to 2006, 132 cases of raccoon rabies, caused by the raccoon variant of rabies virus, were confirmed in eastern Ontario, Canada. Trap-vaccinate-release (TVR) and point infection control (PIC) programs were implemented to control the disease; 43,014 raccoons (Procyon lotor) were vaccinated against rabies by injection (Imrab3) during that period. Two vaccinated raccoons were diagnosed with rabies at 6 mo and at 2 wk postvaccination. One may have been due to a vaccination failure. The other was likely due to the animal being in the late stages of incubation for rabies at the time of vaccination. This information will be useful to wildlife rehabilitators and agencies that hold raccoons in captivity in that a vaccinated raccoon is not necessarily immune to rabies.     

The elimination of raccoon rabies from Wolfe Island, Ontario: animal density and movements

During 1996 to 1998, an average of 52% to 55% of the raccoon (Procyon lotor) population on Wolfe Island, Ontario was vaccinated against rabies during proactive trap-vaccinate-release (TVR) operations. However, during 1999, the percent of the population vaccinated declined to 39% and an outbreak (6 cases) of raccoon rabies occurred on the island from December 1999 to January 2000. The raccoon population on Wolfe Island declined dramatically (71% reduction) from 1,067 raccoons (mean density = 8.4/km(2) [6.4-12.4, 95% CI]) during 1999 to 305 raccoons (mean density = 2.4/km(2) [0.87-4.1, 95% CI]) in the spring of 2000. Raccoon density immediately following the outbreak was significantly lower in cells with rabies cases, suggesting that rabies had a negative effect on population size. However, raccoon density had doubled by 1 yr following the outbreak. Movement of raccoons on Wolfe Island was as great as 24 km. Male raccoons moved greater distances than females. Movements to surrounding islands were also noted for raccoons ear tagged on Wolfe Island which indicates the island could serve as a focus for greater geographic rabies spread. Point infection control (PIC) during 2000, TVR during 2001-02, and the aerial distribution of Vaccinia-Rabies Glycoprotein (V-RG) baits during 2000 and 2003-05 were used to eliminate rabies from Wolfe Island. No cases have been detected since late January 2000 (to February 2007).     

Raccoons (Procyon lotor) in Germany as potential reservoir species for Lyssaviruses

Raccoons can be found almost everywhere in Germany since their first successful introduction in 1934. Although the animal is a well-known reservoir species for rabies in the USA, during the last European fox rabies epizootic, only a few rabid raccoons were reported from Germany. In recent years, the raccoon population density has increased tremendously, especially in (semi) urban settings. Presently, Germany is free of terrestrial wildlife rabies. To assess the potential risk that the raccoon population in Germany could act as a reservoir species upon reemergence of rabies, the susceptibility of the local raccoon population was investigated. Wild-caught animals were inoculated with the most likely lyssavirus variants to infect the local population. It was shown that the raccoons were fully susceptible for a dog and raccoon rabies virus isolate. Also, five of six raccoons inoculated with a fox rabies virus isolate showed clinical signs. However, none of the raccoons infected with European Bat Lyssavirus type 1 succumbed to rabies; meanwhile, all these raccoons seroconverted. It is concluded that the highest risk for the raccoon population in Germany to become infected with lyssaviruses is through the importation of rabies infected dogs.     

Contact rates of raccoons (Procyon lotor) at a communal feeding site in rural eastern Ontario

Intra- and interspecific contact rates of 12 adult (five females, seven males) raccoons (Procyon lotor) were recorded while these animals fed at a rural garbage dump 40 km north of Kingston, Ontario, Canada from 15 June to 5 September 1995. While raccoons were being observed, they bit, and were bitten, by their conspecifics an average of 0.99 (+/- 0.21) and 1.28 (+/- 0.21) times per hour, respectively, while feeding. Based on mean nightly contact rates (which included time when raccoons were not observed), raccoons bit one of their conspecifics once every 3 nights while feeding. The mean rate of bites made and received per hour for males was not significantly different from lactating females. There was no detectable difference between the mean rate of bites made and received per hour for raccoons which regularly versus occasionally fed at the dump. No interspecific contacts were observed, though raccoons and striped skunks (Mephitis mephitis) often fed at the dump concurrently. The contact rates in this study are the first to be calculated for raccoons directly from field data and will be useful as a point of reference for modeling rabies spread in raccoons in areas with similar site characteristics.     

Detection of antibodies reactive with Ehrlichia chaffeensis in the raccoon

Antibodies reactive with Ehrlichia chaffeensis were detected in raccoon (Procyon lotor) serum samples by using an indirect immunofluorescence assay. Samples from 411 raccoons trapped in the southeastern United States from 1977 to 1999 were tested. Serologically reactive samples with reciprocal titers of > or =16 were detected from 83 raccoons (20%) from 13 of 16 counties in eight states, indicating that raccoons are commonly exposed to E. chaffeensis. Samples collected as early as 1977 were positive. A polymerase chain reaction assay specific for E. chaffeensis failed to detect the presence of ehrlichial DNA in serum samples from 20 representative seroreactive raccoons. Because of serologic cross-reactivity among antigens derived from different Ehrlichia spp., additional immunologic, molecular, or culture-based studies will be required to confirm E. chaffeensis infections of raccoons in the southeastern United States.