Characterisation of Trichinella isolates from Bulgaria by molecular typing and cross-breeding

Trichinella spp. larvae were collected from domestic and wild-life animals in association with 15 human trichinellosis outbreaks registered between 1999-2002 in Bulgaria. Furthermore, Trichinella spp. isolates were obtained from 62 naturally infected wild animals and of a rat. All isolates were subjected to speciation by both multiplex PCR and cross-breeding experiments. Epidemiological and clinical data were collected and analysed using standard protocols for epidemiological surveillance and control of outbreaks. Only two species were identified-Trichinella britovi and Trichinella spiralis. Results obtained by molecular typing fully matched those of cross-breeding. More specifically, parasite isolates obtained upon 15 epidemic outbreaks revealed the predominance of T. britovi (n = 10) when compared to T. spiralis (n = 5). With regard to host origin, the predominant species detected among wild boar was T. britovi (n = 4), and T. spiralis was identified in one wild boar sample only. Among the isolates obtained from domestic pig products, T. britovi was found in five cases and T. spiralis in four cases, respectively. In the naturally infected wild animals not related to epidemics, only T. britovi was demonstrated. The present results provide a strong indication that both T. britovi and T. spiralis operate within domestic and sylvatic cycles in Bulgaria. Geographically, the distribution of T. britovi appears to include Central, Southern, Eastern and Western parts of the country, and wildlife animals from the Mid Balkan Mountains and Mid Sredna Gora Mountains, T. spiralis was found in Western and Southwestern Bulgaria, only.