J. Parasitol., 93(5), 2007, pp. 1033–1035 ᭧ American Society of Parasitologists 2007 NEOSPORA CANINUM AND TOXOPLASMA GONDII ANTIBODIES IN DOGS FROM DURANGO CITY, MEXICO J. P. Dubey, C. Alvarado-Esquivel*, O. Liesenfeld†, R. G. Herrera-Flores‡, B. E. Ramı´rez-Sa´nchez‡, A. Gonza´lez-Herrera§, S. A. Martı´nez-Garcı´a*, L. A. Bandini, and O. C. H. Kwok United States Department of Agriculture, Agricultural Research Service, Animal and Natural Resources Institute, Animal Parasitic Diseases Laboratory, Building 1001, Beltsville, Maryland 20705-2350. e-mail: [email protected] ABSTRACT: Toxoplasma gondii and Neospora caninum are structurally similar parasites, with many hosts in common. The prevalence of antibodies to T. gondii and N. caninum was determined in sera from dogs from Durango City, Mexico. Using a modified agglutination test, antibodies to T. gondii were found in 52 (51.5%) of the 101 dogs with titers of 1:25 in 27, 1:50 in 11, 1:100 in 5, 1:200 in 4, 1:400 in 2, 1:800 in 2, and 1:3,200 or higher in 1. Antibodies to N. caninum were determined by the indirect immunofluorescent antibody test (IFAT) and the Neospora sp. agglutination test (NAT). Two of the 101 dogs had N. caninum antibodies; these dogs did not have T. gondii antibodies, supporting the specificity of the tests used. The N. caninum antibody titers of the 2 dogs were: 1:400 by IFAT and 1:200 by NAT in 1, and 1:25 by NAT and IFAT in the other. Results indicate that these 2 structurally similar protozoans are antigenically different. Toxoplasma gondii and Neospora caninum are related coc- nol were used as antigen and a titer of 1:25 or higher was considered cidians that can cause fatal infections in dogs (Dubey, Carpenter indicative of T. gondii exposure. Antibodies to N. caninum in canine sera were detected using the et al., 1988). Toxoplasmosis in dogs is of historical importance indirect fluorescent antibody test (IFAT) as described (Dubey, Hattel et because clinical toxoplasmosis was first diagnosed in a dog by al., 1988) and the direct N. caninum agglutination test (NAT) as de- Mello (1910), soon after the discovery of T. gondii in a rodent scribed (Romand et al., 1998). (Nicolle and Manceaux, 1909). Since then, there have been nu- Statistical evaluation merous reports of clinical toxoplasmosis worldwide and these have been summarized by Dubey (1985) and Dubey and Beattie Results were analyzed with the aid of the software Epi Info 6. For comparison of the frequencies among the groups, the Mantel–Haenszel (1988). After the discovery of N. caninum as a cause of paral- test, and when indicated the Fisher exact test, were used. The associa- ysis in dogs, several reports thought to be toxoplasmosis are tion of the animal characteristics and the T. gondii infection was as- now considered neosporosis (Dubey et al., 1989; Dubey and sessed by calculating the odd ratio with a 95% confidence interval. For Lindsay, 1996). age comparison among groups of dogs the Student’s t-test was used. A Little is known of T. gondii and N. caninum infections in P-value of less than 0.05 was considered significant. Mexican dogs. In the present report, we determined the prev- alence of T. gondii and N. caninum infections in dogs from RESULTS Durango City, Mexico and attempted to identify general char- Antibodies to T. gondii were found in 52 (51.5%) of the 101 acteristics of dogs associated with these infections. dogs with titers of 1:25 in 27, 1:50 in 11, 1:100 in 5, 1:200 in 4, 1:400 in 2, 1:800 in 2, and 1:3,200 or higher in 1. MATERIALS AND METHODS General characteristics of the 101 dogs studied are shown in Dogs Table I. The number of male and female dogs was comparable; All 101 unwanted dogs enrolled from August to November 2006 in however, male dogs had a higher frequency of anti-T. gondii the animal shelter in Durango City, Mexico were studied. The animal antibodies than females (59.6% vs. 40.1%; P ϭ 0.06). Age in shelter attends stray dogs captured by the municipality from the streets dogs was between 3 mo and 12 yr (mean 2.5 yr). The frequency of Durango City and unwanted pets given by the owners for adoption. of infection was comparable among dogs younger than 1 yr, General data, including age, breed, gender, health status, origin (stray ϭ or household), type of food eaten, and residence place for dogs were dogs between 1 and 2 yr (P 0.37), and dogs older than 2 yr obtained (Table I). (P ϭ 0.39). All dogs resided in urban areas. Most dogs were healthy, and the frequency of infection between healthy dogs Serological examination and sick dogs was similar (P ϭ 0.59). In addition, the number The sera were transported by courier from Mexico to Beltsville, of stray and household dogs was comparable, and the frequency Maryland, where serology was performed. Two-fold serial dilutions of infection among these groups was similar (P ϭ 0.94). Sim- were made (1:25 to 1:3,200) and tested for T. gondii antibodies with a modified agglutination test (MAT), as described previously (Dubey and ilarly, the prevalence of infection in household male dogs was Desmonts, 1987). Whole formalin-fixed tachyzoites and mercaptoetha- comparable with that observed in household female dogs (58.3% and 42.9%, respectively; P ϭ 0.30). Most dogs were cross-breeds and the prevalence of infection in this group of Received 2 April 2007; revised 11 April 2007; accepted 12 April ϭ 2007. dogs was similar to that found in purebred dogs (P 0.5). The * Facultad de Medicina, Universidad Jua´rez del Estado de Durango, prevalence of infection in dogs that obtained their food from Dgo Mexico, Avenida Universidad y Fanny Anitua. 34000 Durango, garbage was comparable with that observed in dogs that ate Dgo. Mexico. commercially available (P ϭ 0.79) or homemade food (P ϭ † Institute for Microbiology and Hygiene, Campus Benjamin Franklin, Charite´ Medical School Berlin, Hindenburgdamm 27, D-12203 Berlin, 0.68). Germany. ‡ Animal Shelter Municipal Office of Public Health and Environment. DISCUSSION Durango, Mexico. Carretera a Mexico s/n. Durango, Dgo. Mexico. § Secretary of Health, Durango, Mexico. Cuauhtemoc 225 norte, 34000 In the present study, most dogs seropositive for T. gondii (27 Durango, Dgo. Mexico. of 51) had only a low MAT titer of 1:25. The MAT is consid- 1033 1034 THE JOURNAL OF PARASITOLOGY, VOL. 93, NO. 5, OCTOBER 2007 TABLE I. General characteristics of the dogs and prevalence of anti-T. considered a primary pathogen in dogs and most fatal infections gondii antibodies. reported are in those immunosuppressed, particularly coinfected with canine distemper virus (Campbell et al., 1955; Capen and Dogs studied Dogs seropositive Cole, 1966; Dubey, 1985; Dubey et al., 1989, 2003). To our Characteristics No. % No. % knowledge, there is no confirmed report of congenital toxo- plasmosis in dogs. We are aware of only 1 report of clinical Gender canine toxoplasmosis or neosporosis in Mexico. De Aluja Male 57 56.4 34 59.6 (1971) found T. gondii-like organisms in a dog that had gen- Female 44 43.6 18 40.1 eralized infection; whether this case was toxoplasmosis or neos- Age groups (yr) porosis is uncertain now because the material has not been test- Ͻ1 16 15.8 7 43.8 ed retrospectively for N. caninum infection. Roch and Varela 1–2 55 54.5 31 56.4 (1966) found dye-test T. gondii antibodies in 38.3% of 60 dogs Ͼ2 30 29.7 14 46.7 from Mexico; no other details were given. Residence area The domestic dog is a definitive host for N. caninum and the Urban 101 100 52 51.5 oocysts shed in canine feces are considered essential in the epidemiology of this parasite (McAllister et al., 1998; Dubey, Health status Schares, and Ortega, 2007). Neospora caninum is one of most Healthy 91 90.1 47 51.6 important cause of abortion in cattle worldwide and dogs are Ill 10 9.9 5 50 an important risk factor for N. caninum infection in cattle. Origin Therefore, there have been many surveys for N. caninum in- Stray 56 55.4 29 51.8 fections in dogs worldwide and these were recently summarized Household 45 44.6 23 51.1 (Dubey, Schares, and Ortega, 2007). Breed Sa´nchez et al. (2003) compared N. caninum seroprevalence Pure breed 7 6.9 4 57.1 in city dogs versus farm dogs from a dairy region of Tizayuca, Cross-bred 94 93.1 48 51.1 Hidalgo, Mexico. Antibodies to N. caninum found in more farm Food dogs (51% of 27) than found in the city (20% of 30) using an Commercial 62 61.4 33 53.2 ELISA. These N. caninum seroprevalences in dogs from Hi- Homemade 66 65.3 36 54.5 dalgo were higher than the 2% seroprevalence in animals from Garbage 57 37.6 29 50.8 the Durango city in the present study. How dogs become in- fected with N. caninum is unknown (Dubey, Schares, and Or- tega, 2007). Whether dogs can become infected by ingesting sporulated N. caninum oocysts has not been demonstrated and ered specific for T. gondii at a serum dilution of 1:25 or higher the parasite has not been isolated from the small mammals or on the basis of experimental studies in animals and a validation birds that dogs may hunt for food. Unlike cattle, N. caninum is study in naturally infected pigs (Dubey et al., 1995; Dubey, not likely to be sustained in nature by transplacental transmis- 1997).