Infectivity, persistence and serological response of nine Trichinella genotypes in rats

Domestic and sylvatic Trichinella genotypes were evaluated for infectivity, muscle larvae persistence, and host antibody responses in rats. Groups of rats were inoculated with T. spiralis, T. nativa, T. britovi, three genotypes of T. pseudospiralis (from USSR, USA, and Australia), T. murrelli, Trichinella T6, and T. nelsoni, respectively. The muscle larvae intensity (larvae per gram), total larval burden (lpg x rat weight), and the antibody levels were determined at necropsy 5, 10, 20, and 40 weeks post inoculation. All Trichinella genotypes were established in the rats, but infectivity and persistence differed significantly: T. spiralis established and persisted in high numbers, the three T. pseudospiralis genotypes were also highly infective but differed significantly in persistence, T. britovi and T. nativa had limited infectivity and persistence, Trichinella T6 had low infectivity and very low persistence, and T. murrelli and T. nelsoni were almost non-infective. Except for T. spiralis, initial total muscle larval burdens declined significantly for other genotypes during the experiment. A high initial serological response was detected for all genotypes, but the antibody levels decreased rapidly in relation to decreasing larval burdens. After 20 w.p.i. the antibody levels remained high only in T. spiralis and T. pseudospiralis infected rats. The high infectivity and persistence of T. pseudospiralis in rats, suggests that in addition to T. spiralis, this species might be of significant importance in the domestic cycle of trichinellosis.