TRICHINELLA ZIMBABWENSIS – THE FIRST KNOWN SPECIES OF THE GENUS TRICHINELLA INFECTING COLD-BLOODED ANIMALS: A REVIEW

Abstract

Trichinellosis is a meat-borne zoonotic disease caused by nematodes belonging to the genus Trichinella. These nematodes are among the least host-specific helminths. To date, 10 different Trichinella species have been described, including the encapsulating species Trichinella spiralis, Trichinella nativa, Trichinella britovi, Trichinella nelsoni, Trichinella murrelli, Trichinella chanchalensis, Trichinella patagoniensis and three genotypes whose taxonomic status remains unstipulated - Trichinella T6, T8 and T9 exclusive to mammals, and three non-encapsulating species Trichinella papuae, Trichinella pseudospiralis - infecting mammals and birds, and Trichinella zimbabwensis – infecting both mammals and reptiles. Muscle larvae of T. zimbabwensis, like those of T. papuae, do not infect birds. The morphology of adults and larvae is very similar to that of Trichinella papuae. These two species can cross between each other in both directions (i.e. female of T. zimbabwensis per male of T. papuae and female of T. papuae per male of T. zimbabwensis) producing F1 offspring which produce very few and less viable F2 larvae. These two nematodes cause similar degenerative patterns in the muscles. To summarize, the presence of different species which infect reptiles, mammals or birds in the genus Trichinella strongly suggests the possibility of this nematode group being ancient and it have evolved with the evolution of reptiles into mammals and birds (i.e. from poikilothermic to homoiothermic vertebrates).