Taxonomic Revision of the Genus Trichinella

Abstract

The analysis of genetic, biochemical, and biological data on about 300 Trichinella isolates, reported in the literature, allows a taxonomic revision of this genus. We propose the recognition of 5 sibling species, Trichinella spiralis (Owen, 1835) sensu stricto; Trichinella nativa Britov and Boev, 1972; Trichinella pseudospiralis Garkavi, 1972; Trichinella nelsoni Britov and Boev, 1972 sensu stricto; and Trichinella britovi n. sp., on the basis of biochemical and biological characteristics. Trichinella britovi n. sp. is characterized by distribution in the Palaearctic Region; newborn larvae (NBL) production in vitro of 35-55 NBL/72 hr; nurse cell development time (NC d.t.) between 24 and 42 days postinfection (d.p.i.); low reproductive capacity index (RCI) in mice, rats, and pigs; low resistance to freezing; 1 unique marker allozyme; and moderate pathogenicity for humans. The new species is most similar to Trichinella nativa but differs from it in 4 allozymes, in having less resistance to freezing, in having a different pattern of major ribosomal DNA fragments after endonuclease digestion, and in distribution area. Trichinella nativa is characterized by a holarctic distribution; hosts that are sylvatic mammals; NBL production in vitro 28-54/72 hr; NC d.t. between 20 and 30 d.p.i.; low RCI in mice, rats, and pigs; high resistance to freezing; 2 unique marker allozymes; and moderate to severe pathogenicity for humans. Trichinella spiralis sensu stricto is characterized by a cosmopolitan distribution in domestic pigs, associated wildlife, and humans; high NBL production in vitro (greater than 90 NBL/72 hr); NC d.t. between 16 and 37 d.p.i.; high RCI in mice, rats, and pigs; no resistance to freezing; 6 unique marker allozymes; and high pathogenicity for humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Infectivity, persistence and serological response of nineTrichinellagenotypes in rats

“…and specific antibody titres remained above cut-off level for the duration of the study (Fig. 2) (Ooi et al, 1986;Pozio et al, 1992a;Pozio et al, 1992b;Yao et al, 1997). The high reproductive capacity of T. spiralis in rats, as found here, support the general perception that pigs and rats are the most important hosts in the domestic cycle of infection (Schad et al, 1987;Leiby et al, 1988;Pozio et al, 1996).…”

“…However, findings of natural infections in rats, suggest that moderate infectivity and persistence of T. britovi makes this genotype quite successful in infecting rats, though it cannot be maintained in the domestic cycle . A different situation is observed in Africa where T. nelsoni is the etiological agent of sylvatic trichinellosis Pozio et al, 1992a;Pozio et al, 1997 …”

“…Besides T. spiralis, T. britovi and T. pseudospiralis have been detected in naturally infected rats in Europe and Asia (Pozio et al, 1996;Britov, 1997;Pozio, 2000). Prior to the recognition of multiple species in the genus (Pozio et al, 1992a) . 1963;Kozar & Kozar, 1965;Nelson et al, 1966;Siddiqi & Meerovitch, 1976a;Siddiqi & Meerovitch, 1976b;Belosevic & Dick, 1980;Ooi et al, 1986;Leiby & Bacha, 1987).…”

Study of the 49 kDa excretory-secretory protein gene of Trichinella nativa and Trichinella spiralis

“…Although there are no significant differences in morphology by scanning electron microscopy (Lichtenfels et al, 1983), the two gene types have different host specificity (Smith, 1985;Song et al, 1998;Kapel, 2000;Oivanen et al, 2002). Moreover, T. spiralis and T. nativa have different biological and biochemical characteristics (Pozio et al, 1992b;Song et al, 1994). A recent study showed that T. spiralis and T. nativa induced distinguishable histopathologic and humoral responses in raccoon dogs, there are also significant differences in the shapes and structures of the encapsulated cysts of these two parasites .…”

Fractioning of Protein Extracts of Six Trichinella Isolates by the Methods of Isoelectrofocusing and Silver Staining

“…The different numbers of the polypeptide fractions, the different electrophoretic mobility, different pI, as well as the studies of Pozio et al [ 14 ] give as grounds to assume that the water-soluble proteins of the isolates: ISS03, ISS13, ISS10, ISS02, ISS029, ISS035, belong to the species: T. spiralis, T. pseudospiralis, T. nativa, T. britovi, T. nelsoni and T. murrelli and display both common protein components as well as ones typical of the individual isolates and can be successfully implemented in the identification of various strains and isolates from the Trichinella genus.…”