Trichinella patagoniensis n. sp. (Nematoda), a new encapsulated species infecting carnivorous mammals in South America

Until a few years ago, Trichinella spiralis was the only taxon of the genus Trichinella detected in both domestic and wild animals of South America. Recently, a new genotype, named Trichinella T12, was identified in cougars (Puma concolor) from Argentina, on the basis of molecular studies using mitochondrial and nuclear ribosomal markers. In the present study, cross-breeding experiments indicated that Trichinella T12 is reproductively isolated from all other encapsulated Trichinella spp. and suggested that it is biologically more similar to Trichinella britovi and Trichinella murrelli than to the other encapsulated species/genotypes. Biological assays revealed that the reproductive capacity index of Trichinella T12 was ∼4 and >2000 times lower than those of T. spiralis in mice and rats, respectively. The reproductive capacity index of Trichinella T12 in domestic pigs ranged from 0.0 to 0.05. Larvae parasitising the muscles of carnivores were infective to mice after freezing at −5 °C for 3 months, but they lost infectivity after freezing at −18 °C for 1 week. The region within the rDNA, known as the expansion segment V, showed a unique sequence which differs from those of all other known Trichinella spp./genotypes. The biological, geographical and molecular data support the classification of the genotype Trichinella T12 as a new species widespread in the Neotropical region, for which we propose the name Trichinella patagoniensis n. sp.

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► Further isolates of Trichinella T12 collected from cougars in Argentina were studied.
► Trichinella T12 showed reproductive isolation from the other encapsulated species.
► The sylvatic genotype displayed low infectivity to domestic pigs and laboratory rats.
► Trichinella T12 was resistant to freezing in cat muscles at −5 °C but not at −18 °C.
► We propose classification of this genotype as a new species, Trichinella patagoniensis n. sp.