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 rots were inoculated with T. spiralis, T. nativa, T. britovi, three genotyp es of T pseudospiralis (from USSR, USA, and Australia), T. murrelli, Trichi nella T6, and T. nelsoni, respectively. The muscle larvae intensity (larvae pet 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 per sistence differed significantly: T. spiralis established and persisted in h igh numbers, the three T. pseudospiralis genotypes were also highly infecti ve 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-infec tive. Except for T. spiralis, initial total muscle larval burdens declined significantly for other genotypes during the experiment. A high initial ser ological response was detected for all genotypes, but the antibody levels d ecreased 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 i n rats, suggests that in addition to T. spiralis, this species might be of significant importance in the domestic cycle of trichinellosis.