FECAL EGG AND OOCYST COUNTS IN DOGS AND CATS FROM ANIMAL SHELTERS FROM SOUTH DAKOTA

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1 Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) 227 FECAL EGG AND OOCYST COUNTS IN DOGS AND CATS FROM ANIMAL SHELTERS FROM SOUTH DAKOTA M.B. Hildreth, J.A. Bjordahl and S.R. Duimstra Departments of Biology & Microbiology and Veterinary Sciences South Dakota State University Brookings, SD ABSTRACT Dogs and cats serve as hosts to a variety of gastrointestinal parasites, some of which, can also infect humans. Little is known of the current prevalence and intensity of these parasites in dogs and cats from South Dakota. From 1994 to 1996, 580 dog fecal samples and 88 cat samples were collected from seven different animal shelters located in the following cities: Aberdeen (85 samples), Brookings (96 samples), Huron (49 samples), Pierre (28 samples), Sioux Falls (32 samples), Watertown (261 samples) and Yankton (29 samples). Samples were store at 4ºC until they were examined via a standard centrifugal sucrose flotation procedure. Parasites eggs were identified to the genus level when possible (i.e. Toxacara eggs, Strongyloides eggs, and Dipylidium eggs) or to the family level when necessary (Taeniidae or Ancylostomatoidea). Coccidian oocysts were not further identified to genus or family. At least one parasite was identified in 35.2% of the cat samples and 27.4% of the dog samples. Over 20% of the cats were shedding coccidian oocysts, and the most commonly identified helminth parasite was Toxacara cati (13.6%). Five cats were shedding Taeniidae eggs and only four cats were shedding hookworm eggs. The most commonly identified gastrointestinal parasite in dogs was Toxacara canis (9.1%). Coccidian oocysts were found in 7.9% of the dog samples, and hookworm (Ancylostomatoidea) eggs were found in 7.4%. Taeniid tapeworm eggs were found in 5.2% of the samples; only one dog was found to be infected with Dipylidium. No Trichuris whipworm eggs were found in any of the samples. Prevalences for several of the parasites in this study were significantly different from those reported in a recent national survey involving dogs from strictly urban sites. INTRODUCTION Dogs and cats serve as hosts to a variety of gastrointestinal parasites, some of which, can also infect humans. A recent national survey of dog parasites, based on fecal flotations analysis of samples from 2,322 dogs housed in urban animal shelters, found that almost 36% of the dogs harbored Toxocara canis, Ancylostoma caninum and/or Trichiuris vulpis nematodes (Blagburn et al., 1996). Toxocara canis and A. caninum juveniles are infectious to humans

2 228 Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) causing migrating larvae diseases (visceral larval migrans for T. canis; cutaneous larval migrans for A. caninum). Visceral larval migrans is a potentially lethal disease in children, while cutaneous larval migrans is simply a nuisance condition. Other potentially zoonotic parasites were also found in these dogs. The national survey found that only 0.6% of the dogs were excreting taeniidae tapeworm eggs (i.e. Taenia and Echinococcus). Echinococcus eggs from dogs are directly infectious to humans, but Taenia eggs are not. It is not possible to morphologically differentiate Taenia eggs from Echinococcus eggs, yet, it is very likely that most, if not all, of the dogs excreting Taeniidae eggs in the national survey were infected with a Taenia pisiformis because Taenia pisiformis is a cosmopolitan parasite of dogs, and Echinococcus (i.e. Echinoccus granulosus and E. multilocularis) has a much more restricted distribution and prevalence. An unusually high percentage of wild canids from South Dakota are infected with E. multilocularis (e.g. approximately 65% of the red foxes), and it is possible that dogs from this area are also becoming infected with this tapeworm (Hildreth et al., 2000). Cats can also become infected with E. multilocularis, however, it s growth is stunted, and egg production is very reduced (Crellin et al., 1981). Nothing is known of the current prevalence and intensity of E. multilocularis in dogs and cats from the United States Northern Plains (Hildreth et al., 1991). However, if the prevalence of taeniid eggs is as low in dogs throughout South Dakota, then this would suggest that the potential number of dogs excreting E. multilocularis eggs must be extremely rare. The central purpose of this study was to determine the prevalence of intestinal parasites in dogs and cats from South Dakota. This prevalence study was based upon identifying eggs and cysts of these parasites in fecal samples from dogs and cats housed in animal shelters located in eastern South Dakota. Focus was given to trematode, cestode and nematode helminths, and to coccidian protozoans. Eggs from A. caninum can be differentiated from Uncinaria stenocephala based upon the size of the egg, however, no attempts were made for this differentiation in this study. These eggs were simply reported as members of the family Ancylostomatoidea (i.e. hookworms). Potential protozoan parasites also found in dogs, such as Giardia and Cryptosporidium, were not included in this study. Special attention was given to determining factors affecting dogs excreting Taeniidae eggs. MATERIALS AND METHODS From June 1994 to July 1996, fecal samples were collected from 580 dogs housed at seven different animal shelters located in the following cities throughout South Dakota: Aberdeen (85 samples), Brookings (96 samples), Huron (49 samples), Pierre (28 samples), Sioux Falls (32 samples), Watertown (261 samples) and Yankton (29 samples). Within the 3 years of sampling, 29.2% of these samples were collected during 1994; 34.5% during 1995 and 36.2% during During 1995 and 1996, fecal samples were also collected from 88 cats. These samples were received from only 4 of the cities: Aberdeen (62 samples), Brookings (15 samples), Huron (10 samples) and Watertown (1

3 Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) 229 sample). All samples were shipped and stored at 4ºC until examined via a standard centrifugal sucrose flotation procedure (Bowman, 1995). For this procedure, 1.0 g of feces were added to 10 ml distilled water and stirred to suspend the material. The suspension was then poured through a filter funnel into a centrifuge tube, and centrifuged at 2,000 rpm in a clinical centrifuge for 10 minutes. The fluid was then decanted off of the pellet, and the tube refilled (within a couple cm of the lid) with an aqueous sucrose solution (specific.gravity 1.27). After stirring the pellet into the sucrose solution, the tube was again centrifuged at 1,500 rpm in a clinical centrifuge for 5 minutes. Additional sucrose solution was added to the centrifuge tube to form a meniscus at the top of the tube. A 22X22mm coverslip was added to top of the meniscus, and the eggs and oocysts were allowed to float to the top of the tube and adhere to the coverslip for minutes. The coverslip was then removed from the tube and placed on a microscope slide. Parasites eggs were identified to the genus level when possible (i.e. Toxacara eggs, eggs, Strongyloides eggs, and Dipylidium eggs) or to the family level when necessary (Taeniidae or Ancylostomatoidea). Coccidian oocysts were not further identified to genus or family. Egg and oocyst numbers were reported according to the following intensity scoring system: #1 RARE = 1-2 Eggs/Oocysts/Slide; #2 FEW = 2-10 Eggs or Oocysts/Slide; #3 MODERATE = Eggs or Oocysts/Slide; #4 MANY = Eggs or Oocysts/Slide; and #5 NUMEROUS = More than 100 Eggs or Oocysts/Slides. Personnel from each of the shelters also provided the following information on each dog: approximate age and predominant breed of the dog, and the date the fecal sample was taken. The various dog breeds were assigned to the seven dog groups identified by the American Kennel Club ( These groups include: Sporting Dogs (Group I), Hounds (Group II), Working Dogs (Group III), Terriers (Group IV), The Toys (Group V), Non-Sporting Dogs (Group VI), Hearding Dogs (Group VII), and Miscellaneous Dogs. Cochran-Mantel-Haenszel statistics were performed using SAS 6.12 to measure associations between host information (i.e. age of dog, the year and month samples were collected, city location of the animal shelters, and the American Kennel Club groups represented by each dog) and fecalevaluation results. RESULTS The average age of the cats was 1.4 years, and the average age of the dogs was 2.15 years. Forty-one percent (238) of the dogs included in the study were from Group I (Sporting Dogs), and most of these dogs (165) were Labrador retrievers or Lab-crosses. The remaining dogs were divided among the remaining groups according to the following: Group II (Hounds) %, Group III (Working Dogs) %, Group IV (Terriers) - 8.1%, Group V (The Toys) - 3.5%, Group VI (Non-Sporting Dogs) - 5.4%, Group VII (Herding Dogs) % and Miscellaneous Dogs - 3.1%. At least one parasite was identified in 35.2% of all of the cat samples (Table 1). Over 20% of the cats were shedding coccidian oocysts, and the infected

4 230 Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) Table 1. Dakota Prevalence and Intensity of Intestinal Parasites in Dogs and Cats from South Parasite Prevalence Intensity Prevalence Intensity Name in Dogs in Dogs in Cats in Cats Parasitized 27.41% % Ancylostomadae 7.41% 3.02 (1.32) 4.55% 3.50 (1.91) Toxocara 9.14% 3.61 (1.34) 13.64% 3.47 (1.39) Toxascaris 0.17% Trichuris 0.52% 1.00 (0) - Strongyloides 0.17% Taeniidae 5.17% 3.00 (1.53) 5.68% 3.60 (1.95) Dipylidium 0.17% 3.00 Coccidians 7.93% 3.30 (1.47) 21.59% 4.08 (1.38) cat was releasing many oocysts (i.e. mean intensity score of 4.08). The most commonly identified helminth parasite was Toxacara cati (13.6%). The average infected cat was releasing a moderate number of these eggs (i.e. mean intensity score of 3.47). Five of the cats were shedding Taeniidae eggs; the average cat was shedding moderate to many eggs (mean intensity score of 3.60). Hookworm eggs (Family Ancylostomadae) were found in the least number of cats (i.e. only 4.6%). At least one parasite was identified in 27.4% of all the dog samples (Table 1). The most commonly identified gastrointestinal parasite was Toxacara canis (9.1%). A moderate number of eggs (i.e. mean intensity score of 3.61) were being excreted by the average infected dog. Almost 40% of the infected dogs were releasing eggs (i.e. intensity score of MANY); 26.4% of the infected dogs were releasing numerous eggs (Fig. 1). One dog was infected with Toxascaris nematodes and had released a moderate number of eggs into the fecal sample. Coccidian oocysts were found in 7.9% of the dog samples. Over half of the infected dogs were excreting many or numerous numbers of oocysts, and the average intensity score was Hookworm eggs were identified in 7.4% of the samples. The average intensity score was 3.02, but the egg numbers were evenly distributed within the 5 scoring categories (Fig. 1). Three dog fecal samples contained Trichuris eggs, and each sample had an intensity score of 1. A moderate number of Strongyloides eggs were found in one of the dogs. Dipylidium tapeworm eggs were also only identified in one dog; this dog was also excreting a moderate number of eggs (Table 1). A total of 30 dogs (5.2%) were infected with Taeniidae tapeworms. No apparent pattern existed to the distribution of the scoring intensities (Fig. 1), but the average intensity score was The presence and intensity of Taeniidae infections did not correlate with the age of the dog or the year and month that the samples were taken (p> 0.1). Taeniidae infections were also not associat-

5 Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) 231 Figure 1. Intensity Distribution of Intestinal Parasites in Dogs from South Dakota. Rare or #1 = 1-2 eggs/oocysts per slide; Few or #2 = 2-10 eggs/oocysts per slide; Moderate or #3 = eggs/oocysts per slide; Many or #4 = eggs/oocysts/slide; and Numerous or #5 = more than 100 eggs/oocysts per slides. ed with the city location of the animal shelters. There was a general association between the American Kennel Club groups of dogs and the level of Taeniidae infection (p<0.01). Dogs grouped as herding dogs (Group VII) represented 46.7% of the 30 infected dogs (prevalence of 11.1% for that group). Sporting dogs (Group 1) possessed 23.3% of the infected dogs, but the prevalence for this group was only 4.0%. None of the 31 non-sporting dogs were infected with Taeniidae tapeworms. The remaining 9 infected dogs were distributed among the remaining groups of dogs. DISCUSSION More than one-third of the cat fecal samples tested in the present study contained one or more parasite eggs/oocysts. Fortunately, only a few of these cat parasites are typically infectious to humans. One-fifth of the cats were shedding coccidian oocysts. Lindsay and Blagburn (1991) list 5 genera of coccidian parasites commonly found in domestic cats. Three of these genera contain species that are infectious to humans (i.e.cryptosporidium parvum, Toxoplasma gondii and Sarcocystis spp.). It is likely that some of the oocysts found in the cats from this South Dakota study were Toxoplasma and Sarcocystis oocysts, but the special diagnostic tests needed to reliably diagnose Cryptosporidium infections was not used in this study. It s more likely that most of the oocysts were from the genus Isospora. Neither species of Isospora in-

6 232 Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) fecting cats (I. felis and I. rivolta) are zoonotic, but they can cause gastroenteritis in young and/or immunocompromised cats (Lindsay and Blagburn, 1991). Hammondia hammondi and the species of Besnoitia infecting cats are also not zoonotics, and only rarely cause intestinal problems in their feline host. The zoonotic significance of Toxocara cati is still being debated, but its importance to human heath is minor compared with T. canis (Roberts and Janovy, 2000) even though more that 10% of the cats from South Dakota were infected with this ascarid nematode. Only a few cats were shedding hookworm eggs. It is likely that any species of hookworm can cause cutaneous larval migrans, but Ancylostoma braziliense appears to be the most common agent (Schad, 1994). Most of the hookworm eggs seen in this study were probably Ancylostoma tubaeforme because A. braziliense is more restricted to the Gulf Coast region of the USA (Bowman, 1992). Very few Taeniidae eggs were found in cats from this study. By far, the most common cat taeniid tapeworm found throughout the world is the rat-cat tapeworm, Taenia taeniaeformis. This species is not infectious to humans, and is, very likely, the only species represented by the Taeniidae eggs present in the infected cats from this study. More than one-fourth of the dog fecal samples tested in the present study contained one or more parasite egg/oocysts. The most common and most zoonotically important parasite found in these dogs was T. canis. Toxocariasis is thought to be one of the most common human helminth infections, at least in the temperate climates of the world (Schantz, 1983). Roughly 98% of puppies and 20% of adult dogs in the United States are infected with T. canis (Roberts and Janovy, 2000). The recent national survey of dog parasites by Blagburn et al. (1996) found that 14.5% of the dogs were shedding T. canis eggs. Prevalence is obviously dependent on age, but results from the South Dakota study were similar to the national survey. The zoonotic potential of T. canis juveniles has been firmly documented, and this species is the primary agent for visceral larval migrans. Less than 10% of the dogs were shedding hookworm eggs. The majority of these eggs were a combination of A. caninum and U. stenocephala eggs, and both species can cause cutaneous larval migrans in humans. In the national survey, A. caninum was found in 19.2% of all the dogs tested in the survey, but its prevalence was strongly influenced by region, with 36.5% of the southeastern dogs being infected while only 2.6% of the western dogs were infected (Blagburn et al., 1996). Therefore, it is not surprising that the hookworm prevalence results from the present study were midway between that of the western dogs and the mid-western dogs. Only 1.0% of the dogs from the national study were infected with U. stenocephala, and this did not vary significantly with region. Therefore, the vast majority of hookworm eggs found in South Dakota dogs were likely A. caninum. Only 4 genera of coccidians are listed by Lindsay and Blagburn (1991) as parasitizing dogs. Since C. parvum was not included in this study, all of the oocysts found in the South Dakota dogs were members of either Isospora, Hammondia or Sarcocystis. Only the genus Sarcocystis has species that are zoonotic.

7 Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) 233 The prevalence of taeniid tapeworms were almost ten times higher in the present study from South Dakota dogs than from the national survey. Taeniid infections originate in dogs from the consumption of infected mammalian intermediate hosts (e.g. lagamorphs, rodents or ungulates). Because the national survey focused on dogs from large cities (Lindsay and Blagburn, 1991), many of these dogs would likely have limited access to the intermediate hosts of taeniids. The higher prevalence of taeniid infections in the South Dakota dogs may have resulted from the fact that dogs from small cities and surrounding rural areas were used in this survey, and these dogs would likely have greater access to the intermediate hosts. This idea is supported by the predominant types of dogs included in the South Dakota study. Almost 63% of these dogs were classified either as sporting dogs or herding dogs. These breeds are very capable of catching and killing rabbits and rodents. Another potential explanation for the higher prevalence of taeniid infections in South Dakota dogs relates to the added possibility of E. multilocularis infections in this area but not nationally. This possibility illustrates the need for additional studies specifically evaluating the prevalence of E. multilocularis in dogs from this region. Recent developments in the creation of a coproantigen diagnostic test for E. multilocularis based upon dog fecal samples should greatly facilitate this type of survey (Deplazes et. al, 1999). ACKNOWLEDGEMENTS Special thanks are given to the personnel at the various animal shelters who provided access to the fecal samples. Additional thanks to Keith Mertz and Darlene Buschenfeld who provided technical assistance during this project. This project was supported in parts by Miles, Inc. and by the South Dakota Graduate Research Fund. LITERATURE CITED Blagburn, B.L., D.S. Lindsay, J.L. Vaughan, N.S. Rippey, J.C. Wright, R.C. Lynn, W.J. Kelch, G.C. Ritchie, and D.I. Hepler Prevalence of canine parasites based on fecal flotation. Compend. Contin. Educ. Pract. Vet. 18: Bowman, D.D Hookworm parasites of dogs and cats. Compend. Contin. Educ. Pract. Vet. 14: Bowman, D.D Georgis Parasitology for Veterinarians. W.B. Saunders Company, Philadelphia p. Crellin, J.R., A.A. Marchiondo, and F.L. Andersen Comparison of suitability of dogs and cats as hosts of Echinococcus multilocularis. Am. J. Vet. Res. 42: Deplazes, P., P. Alther, I. Tanner, R.C.A. Thompson, and J. Eckert Echinococcus multilocularis coproantigen detection by enzyme-linked immunosorbent assay in fox, dog, and cat populations. J. Parasitol.:85(1):

8 234 Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) Hildreth, M.B., M.D. Johnson, and K.R. Kazacos Echinococcus multilocularis: A zoonosis of increasing concern in the United States. Compend. Contin. Educ. Pract. Vet. 13: Hildreth, M.B., S. Sriram, B. Gottstein, M. Wilson, and P.M. Schantz Failure to identify alveolar echinococcosis in trappers from South Dakota in spite of high prevalence of Echinococcus multilocularis in wild canids. J. Parasitol. 86: Lindsay, D.S. and B.L. Blagburn Coccidial parasites of cats and dogs. Compend. Contin. Educ. Pract. Vet. 13: Roberts, L.S. and J. Janovy Foundations of Parasitology. McGraw Hill Co. Inc., Boston Schad, G.A Hookworms. Pets to humans. Ann. Intern. Med. 120: Schantz, P.M. Emergent or newly recognized parasitic zoonoses. Compend. Contin. Educ. Pract. Vet. 5: