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Prevalence of Baylisascaris procyonis in raccoon latrines in southern Ontario, Canada
Veterinary Parasitology: Regional Studies and Reports 20 (2020) 100392
Contents lists available at ScienceDirect
Veterinary Parasitology: Regional Studies and Reports journal homepage: www.elsevier.com/locate/vprsr
Short communication
Prevalence of Baylisascaris procyonis in raccoon latrines in southern Ontario, Canada
T
⁎
Grace L. Thorntona,b, Shannon K. Frencha,b, , Andrew S. Peregrinea, Claire M. Jardinea,b a b
Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada Canadian Cooperative Wildlife Health Centre, Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
A R T I C LE I N FO
A B S T R A C T
Keywords: Baylisascaris procyonis Latrine Ontario Procyon lotor Raccoon
Raccoon latrines represent sites of potential infection by the zoonotic parasite Baylisascaris procyonis for wildlife and humans. Our objective was to determine the prevalence of B. procyonis at raccoon latrine sites in southern Ontario. Thirty raccoon latrines were sampled between June – July 2018; multiple scats were collected and homogenized to form a representative sample of each latrine. To determine the presence or absence of B. procyonis eggs in each sample, we used the Cornell-Wisconsin centrifugal floatation technique. Twenty-three percent (7/30) of homogenized samples tested positive for B. procyonis. Eggs per gram of feces ranged from 1 to 388 (median = 1.28, IQR = 0.32–232.5). Baylisascaris procyonis positive latrines were found in conservation areas heavily used by people, which may represent a possible source of exposure for humans in these areas.
1. Introduction Raccoons (Procyon lotor) are common omnivores of the family Procyonidae and are found in urban and rural areas throughout their native home range of North America. As opportunistic scavengers, raccoons often live in close association with humans, and may live in high densities when food and other resources are available. For example, in urban parks and nature reserves, raccoons have been found in high densities and are regularly observed utilizing trash cans as a food source (Riley et al., 1998; Prange and Gehrt, 2004). Raccoons are capable of transmitting many pathogens to both animals and humans, and their close proximity to humans constitutes a potential increased risk of pathogen transmission between species (Rosatte et al., 2010). Raccoons are the definitive host of the zoonotic parasite Baylisascaris procyonis, the raccoon roundworm (Kazacos, 2016). Baylisascaris procyonis is found commonly in raccoons, with reported prevalence as high as to 86% in some areas of North America (Snyder and Fitzgerald, 1987). Infected raccoons can shed between 20,000 to 228,000 eggs per gram of feces (Snyder and Fizgerald, 1987; Kazacos, 2001) and eggs become infective after about two weeks in the environment (Sakla et al., 1989; Kazacos, 2016). Animals, including humans, that ingest the eggs may develop severe neurological disease if larvae migrate through the brain or spinal cord of these non-target hosts (Kazacos, 2016). Raccoons habitually defecate in specific locations, termed
⁎
“latrines”. Latrines may be used by one or more raccoons, accumulating feces over time, and are typically located on flat surfaces like fallen logs and stumps, crooks of trees, or abandoned human structures (Cooney, 1989; Page et al., 1998). Many individual raccoons may visit the same latrine, which creates a discrete location that can be contaminated with high numbers of B. procyonis eggs (Hirsch et al., 2013; Kazacos, 2016). These eggs display substantive resistance to freeze-thaw cycles and desiccation, and may remain viable in the environment for many years (Kazacos and Boyce, 1989; Shafir et al., 2011; Kazacos, 2016); latrine sites therefore act as long-term sources of infection for raccoons, and other animals as they forage for undigested food at latrine sites (Jacobson et al., 1982; Kazacos, 2016). Humans are also at risk of infection if they accidentally ingest infective eggs at latrines. In Ontario, mean raccoon densities have been reported between 3.4 and 13.6 raccoons per km2, with local densities as high as 53 raccoons per km2 in areas of Toronto (Rosatte et al., 2010). As a consequence of these high densities, there are growing concerns about increased risk of B. procyonis transmission to humans. The prevalence of B. procyonis in raccoons in southern Ontario is ~35% (French et al., 2019), but the prevalence of B. procyonis in raccoon latrines in Ontario has not been studied and may be a better indicator of the environmental risk of exposure for humans and other animals. Our objective was to determine the prevalence of B. procyonis at raccoon latrine sites in southern Ontario.
Corresponding author at: Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada. E-mail address: [email protected] (S.K. French).
https://doi.org/10.1016/j.vprsr.2020.100392 Received 25 September 2019; Received in revised form 21 February 2020; Accepted 21 February 2020 Available online 22 February 2020 2405-9390/ © 2020 Elsevier B.V. All rights reserved.
Veterinary Parasitology: Regional Studies and Reports 20 (2020) 100392
G.L. Thornton, et al.
Fig. 1. The proportion of latrines with at least one Baylisascaris procyonis egg identified by double centrifugation fecal flotation out of the total number of latrines sampled, between June and July 2018, at each of the eight study properties where latrines were found.
2. Materials and methods
3. Results
Areas within nine different conservation properties near Guelph, Ontario, Canada were surveyed for latrine sites in June and July 2018 (Fig. 1). These sites ranged from natural areas with trails to areas heavily used by people. We found latrine sites by strategically searching forested areas within the conservation areas, with emphasis on the base of trees, tops of fallen logs and stumps, and crooks of trees. A latrine was identified based on established characteristics including the length and colour of the feces, as well as the presence of > 1 scat (Kazacos, 2016). We recorded location, latrine type (i.e., base of tree, fallen log, tree stump), and distance to nearest trail/path for each latrine site. Only paved or gravel paths constructed by the conservation areas, were used for these measurements. Fecal samples were collected from each latrine and since multiple raccoons may use the same latrine, we collected and homogenized samples from multiple scats (2–5) at a latrine to create a representative sample. We used the Cornell-Wisconsin centrifugal floatation technique as described by Egwang and Slocombe (1982), with a specific gravity of 1.27, to determine the presence or absence of B. procyonis eggs. Eggs were identified morphologically on 40× magnification and measured on 100× magnification (Olympus BX45, eyepiece 10×) to help ensure accurate identification (Zajac and Conboy, 2012). We calculated eggs per gram of feces for each sample (Egwang and Slocomb, 1982); fecal samples ranged from 1 to 5 g, and we applied a standardization factor to each sample to determine eggs per gram. The limit of detection of this method under optimal conditions was 1 egg/5 g of feces (Egwang and Slocomb, 1982).
Thirty raccoon latrines were identified at eight of the nine conservation areas surveyed and included between one and seven latrines within each conservation area (Fig. 1). Positive latrines were identified in 44% of the conservation areas examined (4/9), and the number of positive latrines in a single conservation area ranged from zero to three. Baylisascaris procyonis eggs were detected at 23% (7/30, 95% Confidence Interval (CI): 11–43%) of the latrines sampled; egg counts in each positive latrine sample ranged from 1 to 388 eggs per gram of feces (median = 1.28, IQR = 0.32–232.5). Most raccoon latrines were found in less-dense, deciduous forest. Samples were collected as follows: 50% from the base of trees, 37% from the tops of fallen logs, and 7% from the tops of tree stumps; one latrine was identified on the ground, and one in an abandoned shed. The distance to a human-use trail ranged from 13 to 494 m (median distance = 53 m). 4. Discussion B. procyonis eggs were detected in 23% of latrine sites in our study area, comparable to latrine prevalence studies from the midwestern United States that recorded values ranging from 14 to 23% (Page et al., 1998; Page et al., 2009). The highest reported latrine prevalence was 100% (n = 800) in California and they reported a mean fecal count of 30,265 eggs per gram (Evans, 2002). Our fecal egg counts were lower than previously reported, but it is possible that our methods may have underestimated fecal egg counts (Levecke et al., 2012; Bosco et al., 2018), and lead to a subsequent underestimation of prevalence. 2
Veterinary Parasitology: Regional Studies and Reports 20 (2020) 100392
G.L. Thornton, et al.
Previous studies have found similar prevalences of B. procyonis eggs at raccoon latrines as in the feces of live-trapped raccoons from the same area (Jacobson et al., 1982). The infection prevalence we identified in our sampled latrines is similar to what has been found in postmortem studies of raccoon intestinal infections in southern Ontario (38%, 95% CI: 30–47%; Jardine et al., 2014, French et al., 2019). Seasonality of B. procyonis infections in raccoons, including a late summer/fall increase in prevalence, has been described in both raccoon necropsy and fecal collection studies (Cottrell et al., 2014; Jardine et al., 2014; Page et al., 2016). However, seasonality in the prevalence of B. procyonis at raccoon latrine sites is not clearly established (Greve, 1985; Sexsmith et al., 2009). By sampling only during a two-month period, we are unable to evaluate the possibility that seasonal trends are present at latrines, or if site contamination and fecal egg counts are consistent year round. A longitudinal study of raccoon latrines would allow one to better understand the seasonal persistence of B. procyonis at latrine sites under natural conditions. The sites evaluated in this study ranged from areas that were primarily forested with unmaintained hiking trails to areas where forests were in close proximity to picnic and camping sites. Although most positive latrines were identified in more natural sites, the two latrines with the highest egg per gram counts were detected in conservation areas commonly used by people. People may leave posted trails with their animals or children and inadvertently contact latrines while exploring. The presence of B. procyonis eggs in human-use areas has been observed in many urban environments in North America and carries implications for possible occurrences of baylisascariasis in humans (Gavin et al., 2005; Wise et al., 2005; Page et al., 2009). In addition, although it is rare, domesticated dogs can act as hosts for B. procyonis and may potentially transmit the parasite to their owners through close personal interaction (Kazacos, 2016; Yabsley and Sapp, 2017). There are also reports of young dogs becoming fatally infected with the larval stage of the parasite following exposure to raccoon feces (Heller et al., 2019). Our sample size and area were small; however, latrine sampling is more efficient than sampling live-trapped raccoons or performing necropsies (Page et al., 2005; Smyser et al., 2010) and focuses on a potential source of exposure in the environment, giving a more accurate understanding of the potential risk of infection to people. Moving forward, increasing our sample size with a focus on repeat sampling over multiple seasons will offer an effective way to monitor the prevalence of B. procyonis in the region, and estimate the potential risk of infection to humans. Where raccoons are common, education of the public and potential removal of latrines may be necessary to decrease human-latrine interactions (Gavin et al., 2005; Kazacos, 2016).
sheep faeces by three methods. BMC Vet. Res. 14 (1), 7. Cooney, T.A., 1989. Environmental Contamination With Baylisascaris procyonis in an Urban Park. M.S. thesis. Purdue University, West Lafayette, Indiana (125 pp). Cottrell, W.O., Heagy, R.L., Johnson, J.B., Marcantuno, R., Nolan, T.J., 2014. Geographic and temporal prevalence of Baylisascaris procyonis in raccoons (Procyon lotor) in Pennsylvania, USA. J. Wild. Dis. 50, 923–927. Egwang, T.G., Slocombe, J.O.D., 1982. Evaluation of the Cornell-Wisconsin centrifugal flotation technique for recovering Trichostrongylid eggs from bovine feces. Can. J. Comp. Med. 46, 133–137. Evans, R.H., 2002. Baylisascaris procyonis (Nematoda: Ascaridoidea) eggs in raccoon (Procyon lotor) latrine scats in Orange County, California. J. Parasitol. 88, 189–190. French, S.K., Pearl, D.L., Shirose, L., Peregrine, A.S., Jardine, C.M., 2019. Demographic and environmental factors associated with Baylisascaris procyonis infection of raccoons (Procyon lotor) in Ontario, Canada. J. Wild. Dis (In Press). Gavin, P.J., Kazacos, K.R., Shulman, S.T., 2005. Baylisascariasis. Clin. Microbiol. Rev. 18, 703–718. Greve, J.H., 1985. Raccoon ascarids pose public health threat. Iowa State Univ. Vet. 47, 13–14. Heller, H.B., Arnold, S., Dreyfus, J.L., 2019. Baylisascaris procyonis central nervous system infection in a four-month-old Gordon setter dog. J. Am. Anim. Hosp. Assoc. 55 (3) (e553-01). Hirsch, B.T., Prange, S., Hauver, S.A., Gehrt, S.D., 2013. Raccoon social networks and the potential for disease transmission. PLoS One 8, 75830. Jacobson, J.E., Kazacos, K.R., Montague, F.H., 1982. Prevalence of eggs of Baylisascaris procyonis (Nematoda:Ascaroidea) in raccoon scats from an urban and a rural community. J. Wildl. Dis. 18, 461–464. Jardine, C.M., Pearl, D.L., Puskas, K., Campbell, D.G., Shirose, L., Peregrine, A.S., 2014. The impact of land use, season, age, and sex on the prevalence and intensity of Baylisascaris procyonis infections in raccoons (Procyon lotor) from Ontario, Canada. J. Wildl. Dis. 50, 784–791. Kazacos, K.R., 2001. Baylisascaris procyonis and related species. In: Samuel, W.M., Pybus, M.J., Kocan, A.A. (Eds.), Parasitic Diseases of Wild Mammals. Iowa State University Press, Ames, Iowa, pp. 301–341. Kazacos, K.R., 2016. Baylisascaris larva migrans, Circular 1412. (Reston, VA. 122pp). Kazacos, K.R., Boyce, W.M., 1989. Baylisascaris larva migrans. J. Am. Vet. Med. Assoc. 195, 894–903. Levecke, B., Rinaldi, L., Charlier, J., Maurelli, M.P., Bosco, A., Vercruysse, J., Cringoli, G., 2012. The bias, accuracy and precision of faecal egg count reduction test results in cattle using McMaster, Cornell-Wisconsin and FLOTAC egg counting methods. Vet. Parasitol. 188 (1–2), 194–199. Page, L.K., Swihart, R.K., Kazacos, K.R., 1998. Raccoon latrine structure and its potential role in transmission of Baylisascaris procyonis to vertebrates. Am. Midl. Nat. 140, 180–185. Page, L.K., Gehrt, S.D., Titcombe, K.K., Robinson, N.P., 2005. Measuring prevalence of raccoon roundworm (Baylisascaris procyonis): a comparison of common techniques. Wildl. Soc. Bull. 33, 1406–1412. Page, K.L., Anchor, C., Luy, E., Kron, S., Larson, G., Madsen, L., Kellner, K., Smyser, T.J., 2009. Backyard raccoon latrines and risk for Baylisascaris procyonis transmission to humans. Emerg. Infect. Dis. 15, 1530–1531. Page, K.L., Delzell, D.A.P., Gehrt, S.D., Harrell, E.D., Hilben, M., Walter, E., Anchor, C., Kazacos, K.R., 2016. The structure and seasonality of Baylisascaris procyonis populations in raccoons (Procyon lotor). J. Wildl. Dis. 52, 286–292. Prange, S., Gehrt, S.D., 2004. Changes in mesopredator-community structure in response to urbanization. Can. J. Zool. 82, 1804–1817. Riley, S.P.D., Hadidian, J., Manski, D.A., 1998. Population density, survival, and rabies in raccoons in an urban national park. Can. J. Zool. 76, 1153–1164. Rosatte, R., Ryckman, M., Ing, K., Proceviat, S., Allan, M., Bruce, L., Donovan, D., Davies, J.C., Da, J.C., 2010. Density, movements, and survival of raccoons in Ontario, Canada: implications for disease spread and management. J. Mammal. 91, 122–135. Sakla, A.A., Donnelly, J.J., Khatami, M., Rockey, J.H., 1989. Baylisascaris procyonis (Stefanski and Zarnowski, 1951) Ascarididae: Nematoda. I. Embryonic development and morphogenesis of second stage larvae. Assiut. Vet. Med. J. 21, 68–76. Sexsmith, J.L., Whiting, T.L., Green, C., Orvis, S., Berezanski, D.J., Thompson, A.B., 2009. Prevalence and distribution of Baylisascaris procyonis in urban raccoons (Procyon lotor) in Winnipeg, Manitoba. Can. Vet. J. 50, 846–850. Shafir, S.C., Sorvillo, F.J., Sorvillo, T., Eberhard, M.L., 2011. Viability of Baylisascaris procyonis eggs. Emerg. Infect. Dis. 17, 1293–1295. Smyser, T.J., Page, K.L., Rhodes, O.E., 2010. Optimization of raccoon latrine surveys for quantifying exposure to Baylisascaris procyonis. J. Wildl. Dis. 46, 929–933. Snyder, D.E., Fitzgerald, P.R., 1987. Contaminative potential, egg prevalence, and intensity of Baylisascaris procyonis–infected raccoons (Procyon lotor) from Illinois, with a comparison to worm intensity. Proc. Helminthol. Soc. Wash. 54, 141–145. Wise, M.E., Sorvillo, F.J., Shafir, S.C., Ash, L.R., Berlin, O.G., 2005. Severe and fatal central nervous system disease in humans caused by Baylisascaris procyonis, the common roundworm of raccoons: a review of current literature. Microbes Infect. 7, 317–323. Yabsley, M.J., Sapp, S.G., 2017. Prevalence of Baylisascaris in domestic dog coprological examinations in the United States, 2013–2016. Vet. Parasitol. Reg. Stud. Rep. 9, 65–69. Zajac, A.M., Conboy, G.A., 2012. Fecal examination for the diagnosis of parasitism. In: Zajac, A.M., Conboy, G.A. (Eds.), Clinical Veterinary Parasitology. John Wiley & Sons, Inc, Chichester, West Sussex, pp. 58–60.
Declarations of Competing Interest None. Acknowledgements We thank Chris Early, Lesley McDonell, and Jenna Quinn for help finding raccoon latrines. We thank the Hamilton Conservation Authority, rare Charitable reserve, the University of Guelph Arboretum, and the City of Guelph for allowing research on their properties. Jacob Avula, Joyce Rousseau, and Tami Sauder provided lab assistance. SF was supported by an OVC PhD Scholarship and the Estill Family Graduate Scholarship in the Arboretum. References Bosco, A., Maurelli, M.P., Ianniello, D., Morgoglione, M.E., Amadesi, A., Coles, G.C., Cringoli, G., Rinaldi, L., 2018. The recovery of added nematode eggs from horse and
3
Contents lists available at ScienceDirect
Veterinary Parasitology: Regional Studies and Reports journal homepage: www.elsevier.com/locate/vprsr
Short communication
Prevalence of Baylisascaris procyonis in raccoon latrines in southern Ontario, Canada
T
⁎
Grace L. Thorntona,b, Shannon K. Frencha,b, , Andrew S. Peregrinea, Claire M. Jardinea,b a b
Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada Canadian Cooperative Wildlife Health Centre, Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
A R T I C LE I N FO
A B S T R A C T
Keywords: Baylisascaris procyonis Latrine Ontario Procyon lotor Raccoon
Raccoon latrines represent sites of potential infection by the zoonotic parasite Baylisascaris procyonis for wildlife and humans. Our objective was to determine the prevalence of B. procyonis at raccoon latrine sites in southern Ontario. Thirty raccoon latrines were sampled between June – July 2018; multiple scats were collected and homogenized to form a representative sample of each latrine. To determine the presence or absence of B. procyonis eggs in each sample, we used the Cornell-Wisconsin centrifugal floatation technique. Twenty-three percent (7/30) of homogenized samples tested positive for B. procyonis. Eggs per gram of feces ranged from 1 to 388 (median = 1.28, IQR = 0.32–232.5). Baylisascaris procyonis positive latrines were found in conservation areas heavily used by people, which may represent a possible source of exposure for humans in these areas.
1. Introduction Raccoons (Procyon lotor) are common omnivores of the family Procyonidae and are found in urban and rural areas throughout their native home range of North America. As opportunistic scavengers, raccoons often live in close association with humans, and may live in high densities when food and other resources are available. For example, in urban parks and nature reserves, raccoons have been found in high densities and are regularly observed utilizing trash cans as a food source (Riley et al., 1998; Prange and Gehrt, 2004). Raccoons are capable of transmitting many pathogens to both animals and humans, and their close proximity to humans constitutes a potential increased risk of pathogen transmission between species (Rosatte et al., 2010). Raccoons are the definitive host of the zoonotic parasite Baylisascaris procyonis, the raccoon roundworm (Kazacos, 2016). Baylisascaris procyonis is found commonly in raccoons, with reported prevalence as high as to 86% in some areas of North America (Snyder and Fitzgerald, 1987). Infected raccoons can shed between 20,000 to 228,000 eggs per gram of feces (Snyder and Fizgerald, 1987; Kazacos, 2001) and eggs become infective after about two weeks in the environment (Sakla et al., 1989; Kazacos, 2016). Animals, including humans, that ingest the eggs may develop severe neurological disease if larvae migrate through the brain or spinal cord of these non-target hosts (Kazacos, 2016). Raccoons habitually defecate in specific locations, termed
⁎
“latrines”. Latrines may be used by one or more raccoons, accumulating feces over time, and are typically located on flat surfaces like fallen logs and stumps, crooks of trees, or abandoned human structures (Cooney, 1989; Page et al., 1998). Many individual raccoons may visit the same latrine, which creates a discrete location that can be contaminated with high numbers of B. procyonis eggs (Hirsch et al., 2013; Kazacos, 2016). These eggs display substantive resistance to freeze-thaw cycles and desiccation, and may remain viable in the environment for many years (Kazacos and Boyce, 1989; Shafir et al., 2011; Kazacos, 2016); latrine sites therefore act as long-term sources of infection for raccoons, and other animals as they forage for undigested food at latrine sites (Jacobson et al., 1982; Kazacos, 2016). Humans are also at risk of infection if they accidentally ingest infective eggs at latrines. In Ontario, mean raccoon densities have been reported between 3.4 and 13.6 raccoons per km2, with local densities as high as 53 raccoons per km2 in areas of Toronto (Rosatte et al., 2010). As a consequence of these high densities, there are growing concerns about increased risk of B. procyonis transmission to humans. The prevalence of B. procyonis in raccoons in southern Ontario is ~35% (French et al., 2019), but the prevalence of B. procyonis in raccoon latrines in Ontario has not been studied and may be a better indicator of the environmental risk of exposure for humans and other animals. Our objective was to determine the prevalence of B. procyonis at raccoon latrine sites in southern Ontario.
Corresponding author at: Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada. E-mail address: [email protected] (S.K. French).
https://doi.org/10.1016/j.vprsr.2020.100392 Received 25 September 2019; Received in revised form 21 February 2020; Accepted 21 February 2020 Available online 22 February 2020 2405-9390/ © 2020 Elsevier B.V. All rights reserved.
Veterinary Parasitology: Regional Studies and Reports 20 (2020) 100392
G.L. Thornton, et al.
Fig. 1. The proportion of latrines with at least one Baylisascaris procyonis egg identified by double centrifugation fecal flotation out of the total number of latrines sampled, between June and July 2018, at each of the eight study properties where latrines were found.
2. Materials and methods
3. Results
Areas within nine different conservation properties near Guelph, Ontario, Canada were surveyed for latrine sites in June and July 2018 (Fig. 1). These sites ranged from natural areas with trails to areas heavily used by people. We found latrine sites by strategically searching forested areas within the conservation areas, with emphasis on the base of trees, tops of fallen logs and stumps, and crooks of trees. A latrine was identified based on established characteristics including the length and colour of the feces, as well as the presence of > 1 scat (Kazacos, 2016). We recorded location, latrine type (i.e., base of tree, fallen log, tree stump), and distance to nearest trail/path for each latrine site. Only paved or gravel paths constructed by the conservation areas, were used for these measurements. Fecal samples were collected from each latrine and since multiple raccoons may use the same latrine, we collected and homogenized samples from multiple scats (2–5) at a latrine to create a representative sample. We used the Cornell-Wisconsin centrifugal floatation technique as described by Egwang and Slocombe (1982), with a specific gravity of 1.27, to determine the presence or absence of B. procyonis eggs. Eggs were identified morphologically on 40× magnification and measured on 100× magnification (Olympus BX45, eyepiece 10×) to help ensure accurate identification (Zajac and Conboy, 2012). We calculated eggs per gram of feces for each sample (Egwang and Slocomb, 1982); fecal samples ranged from 1 to 5 g, and we applied a standardization factor to each sample to determine eggs per gram. The limit of detection of this method under optimal conditions was 1 egg/5 g of feces (Egwang and Slocomb, 1982).
Thirty raccoon latrines were identified at eight of the nine conservation areas surveyed and included between one and seven latrines within each conservation area (Fig. 1). Positive latrines were identified in 44% of the conservation areas examined (4/9), and the number of positive latrines in a single conservation area ranged from zero to three. Baylisascaris procyonis eggs were detected at 23% (7/30, 95% Confidence Interval (CI): 11–43%) of the latrines sampled; egg counts in each positive latrine sample ranged from 1 to 388 eggs per gram of feces (median = 1.28, IQR = 0.32–232.5). Most raccoon latrines were found in less-dense, deciduous forest. Samples were collected as follows: 50% from the base of trees, 37% from the tops of fallen logs, and 7% from the tops of tree stumps; one latrine was identified on the ground, and one in an abandoned shed. The distance to a human-use trail ranged from 13 to 494 m (median distance = 53 m). 4. Discussion B. procyonis eggs were detected in 23% of latrine sites in our study area, comparable to latrine prevalence studies from the midwestern United States that recorded values ranging from 14 to 23% (Page et al., 1998; Page et al., 2009). The highest reported latrine prevalence was 100% (n = 800) in California and they reported a mean fecal count of 30,265 eggs per gram (Evans, 2002). Our fecal egg counts were lower than previously reported, but it is possible that our methods may have underestimated fecal egg counts (Levecke et al., 2012; Bosco et al., 2018), and lead to a subsequent underestimation of prevalence. 2
Veterinary Parasitology: Regional Studies and Reports 20 (2020) 100392
G.L. Thornton, et al.
Previous studies have found similar prevalences of B. procyonis eggs at raccoon latrines as in the feces of live-trapped raccoons from the same area (Jacobson et al., 1982). The infection prevalence we identified in our sampled latrines is similar to what has been found in postmortem studies of raccoon intestinal infections in southern Ontario (38%, 95% CI: 30–47%; Jardine et al., 2014, French et al., 2019). Seasonality of B. procyonis infections in raccoons, including a late summer/fall increase in prevalence, has been described in both raccoon necropsy and fecal collection studies (Cottrell et al., 2014; Jardine et al., 2014; Page et al., 2016). However, seasonality in the prevalence of B. procyonis at raccoon latrine sites is not clearly established (Greve, 1985; Sexsmith et al., 2009). By sampling only during a two-month period, we are unable to evaluate the possibility that seasonal trends are present at latrines, or if site contamination and fecal egg counts are consistent year round. A longitudinal study of raccoon latrines would allow one to better understand the seasonal persistence of B. procyonis at latrine sites under natural conditions. The sites evaluated in this study ranged from areas that were primarily forested with unmaintained hiking trails to areas where forests were in close proximity to picnic and camping sites. Although most positive latrines were identified in more natural sites, the two latrines with the highest egg per gram counts were detected in conservation areas commonly used by people. People may leave posted trails with their animals or children and inadvertently contact latrines while exploring. The presence of B. procyonis eggs in human-use areas has been observed in many urban environments in North America and carries implications for possible occurrences of baylisascariasis in humans (Gavin et al., 2005; Wise et al., 2005; Page et al., 2009). In addition, although it is rare, domesticated dogs can act as hosts for B. procyonis and may potentially transmit the parasite to their owners through close personal interaction (Kazacos, 2016; Yabsley and Sapp, 2017). There are also reports of young dogs becoming fatally infected with the larval stage of the parasite following exposure to raccoon feces (Heller et al., 2019). Our sample size and area were small; however, latrine sampling is more efficient than sampling live-trapped raccoons or performing necropsies (Page et al., 2005; Smyser et al., 2010) and focuses on a potential source of exposure in the environment, giving a more accurate understanding of the potential risk of infection to people. Moving forward, increasing our sample size with a focus on repeat sampling over multiple seasons will offer an effective way to monitor the prevalence of B. procyonis in the region, and estimate the potential risk of infection to humans. Where raccoons are common, education of the public and potential removal of latrines may be necessary to decrease human-latrine interactions (Gavin et al., 2005; Kazacos, 2016).
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Declarations of Competing Interest None. Acknowledgements We thank Chris Early, Lesley McDonell, and Jenna Quinn for help finding raccoon latrines. We thank the Hamilton Conservation Authority, rare Charitable reserve, the University of Guelph Arboretum, and the City of Guelph for allowing research on their properties. Jacob Avula, Joyce Rousseau, and Tami Sauder provided lab assistance. SF was supported by an OVC PhD Scholarship and the Estill Family Graduate Scholarship in the Arboretum. References Bosco, A., Maurelli, M.P., Ianniello, D., Morgoglione, M.E., Amadesi, A., Coles, G.C., Cringoli, G., Rinaldi, L., 2018. The recovery of added nematode eggs from horse and
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