Allozyme analysis of Trichinella isolates from various host species and geographical regions.

Allozyme analysis was carried out on 152 Trichinella isolates from synanthropic and wild animals and from humans; the isolates were collected from 5 continents. The analysis, involving 27 enzymes, revealed the presence of 8 distinct gene pools, termed T1-T8. Four of the genetic groups represent the 4 previously proposed species: Trichinella spiralis sensu stricto (T1), Trichinella nativa (T2), Trichinella nelsoni (T7), and Trichinella pseudospiralis (T4). The other 4, T3, T5, T6, and T8 are distinct from previously described species. The absence of allozymic hybrid patterns among even sympatric groups indicates a lack of gene flow among the groups. Principal component analysis and the unweighted pair group method of analysis were used to assemble allozyme patterns of the 152 isolates into discrete groups and to show their relative relationships. Both analyses indicated the presence of 8 primary clusters that correlated with the gene pools revealed by direct allozyme profile analysis. The absence of evidence of gene flow among the gene pools and the high level of allozymic differentiation between the cluster groups support the concept that the genus Trichinella is composed of several sibling species.