Trichinella zimbabwensis n.sp. (Nematoda), a new non-encapsulated species from crocodiles (Crocodylus niloticus) in Zimbabwe also infecting mammals.

Since 1995, Trichinella larvae have been detected in 39.5% of farmed crocodiles (Crocodylus niloticus) in Zimbabwe. Morphological, biological, biochemical and molecular studies carried out on one isolate from a farmed crocodile in 2001 support the conclusion that this parasite belongs to a new species, which has been named Trichinella zimbabwensis n.sp. This species, whose larvae are non-encapsulated in host muscles, infects both reptiles and mammals. The morphology of adults and larvae is similar to that of Trichinella papuae. Adults of T. zimbabwensis cross in both directions with adults of T. papuae (i.e. male of T. zimbabwensis per female of T. papuae and male of T. papuae per female of T. zimbabwensis), producing F1 offspring which produce very few and less viable F2 larvae. Muscle larvae of T. zimbabwensis, like those of T. papuae, do not infect birds. Three allozymes (of a total of 10) are diagnostic between T. zimbabwensis and T. papuae, and five are diagnostic between T. zimbabwensis and Trichinella pseudospiralis, the third non-encapsulated species. The percentage of the pairwise alignment identity between T. zimbabwensis and the other Trichinella species for the cytochrome oxidase subunit I gene, the large subunit ribosomal-DNA (mt-lsrDNA) gene and the expansion segment five, shows that T. zimbabwensis is more similar to the two non-encapsulated species T. papuae (91% for cytochrome oxidase I; 96% for mt-lsrDNA; and 88% for expansion segment five) and T. pseudospiralis (88% for cytochrome oxidase I; 90% for mt-lsrDNA; and 66-73% for expansion segment five) than to any of the encapsulated species (85-86% for cytochrome oxidase I; 88-89% for mt-lsrDNA; and 71-79% for expansion segment five). This is the first non-encapsulated species discovered in Africa. The finding of a new Trichinella species that infects both reptiles and mammals suggests that the origin of Trichinella parasites dates back further than previously believed and can contribute to understanding the phylogeny and the epidemiology of the genus Trichinella.