Neospora caninum infection in stray and farm dogs: seroepidemiological study and oocyst shedding.

In a previous study, farm and stray dogs were considered potential high risk populations of Neospora caninum infection in Spain. Consequently, we decided to investigate the significance of N. caninum infection in these populations. Specific antibodies were detected in 120 out of 275 dog sera (43.6%), with titres ranging from 1:50 to 1:800. Differences in seroprevalence between farm (47.5%, 67/141) and stray (39.5%, 53/134) dogs were not significant (P>0.05; χ(2) test), but farm dogs showed significantly higher titres (P<0.01; Student's t-test). N. caninum seroprevalence in farm dogs was associated with increasing age (P<0.01; χ(2) test) and dogs with free access to the farm were more likely to be seropositive than controlled-dogs (P<0.05; χ(2) test). The presence of anti-N. caninum antibodies was more often detected in dogs from farms with 5-20% N. caninum within-herd seroprevalence (56.9%, 37/65) than those from farms with 0-5% seroprevalence (38%, 23/60) (P<0.05; χ(2) test). We microscopically observed N. caninum-like oocysts in the faeces from one farm dog, but the number of oocysts was very low, and the aetiology could not be confirmed. Also, parasite isolation was attempted from fresh neural tissue from stray dogs but was unsuccessful.

Detection of Echinococcus coproantigens in stray dogs of northern Spain.

An enzyme-linked immunosorbent assay (ELISA) was assessed for its suitability to diagnostically detect Echinococcus coproantigens in fecal samples of dogs infected with E. granulosus. The specificity of the test was determined by investigating fecal samples from 177 Echinococcus-free dogs infected with Taenia spp., 41 dogs with non-taeniid helminths and 24 dogs free of helminth infections. An overall specificity of 97% was determined. The diagnostic sensitivity was in close association to the worm burden of infected individuals: when dogs harboured less than 100 worms, six from 21 samples (29%) were found to be positive in coproantigen ELISA, whereas sensitivity was much higher (23 ELISA-positive from 25 samples = 92%) when dogs had more than 100 worms. Despite the relatively low average sensitivity (63%), the test enabled detection of more than 90% of the biomass of adult Echinococcus present in the respective dog populations. Conclusively, coproantigen detection allows diagnosis of most individual intestinal Echinococcus infections relevant for the egg contamination of the environment and is therefore a valuable tool to determine the relative prevalence of adult stage E. granulosus prevalence in a given endemic area.

Detection of Echinococcus coproantigens by enzyme-linked immunosorbent assay in dogs, dingoes and foxes.

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of Echinococcus coproantigens in fecal samples from dogs, dingoes or foxes infected with either E. granulosus or E. multilocularis. The ELISA was based on protein-A-purified polyclonal antibodies [anti-E. granulosus excretory/secretory (E/S) antigens]. The specificity of the assay as determined in 155 samples derived from carnivores that were free of helminth infection (n = 37) or infected with non-Echinococcus cestodes (n = 76) or with various nematodes (n = 42) was found to be 98% overall. The diagnostic sensitivity was strongly dependent on the homologous worm burden. All 13 samples from foxes harboring greater than 1,000 E. multilocularis worms and 13 of 15 (87%) samples from dogs or dingoes containing greater than 200 E. granulosus worms were ELISA-positive, whereas 34 of 46 samples from foxes harboring less than 1,000 E. multilocularis and 9 of 10 samples from dogs or dingoes bearing less than 200 E. granulosus tested negative. Experimental prepatent infections of dogs with E. granulosus revealed positive ELISA reactions within the prepatent period (10-20 days post-infection) for six animals bearing greater than 1,000 E. granulosus each; a low worm burden (less than 1,000 tapeworms/animal) resulted in ELISA positivity in only 2 of 3 animals at 30 days post-infection at the earliest. All five dogs that had been experimentally infected with E. multilocularis tested positive in the coproantigen ELISA as early as on day 5 post-infection.