The aim of this study was to compare levels of stress proteins in four Trichinella species when exposed to different stressors. Heat shock protein (HSP) 60, 70 and 90 responses were evaluated in infective larvae (L(1)) of four classic Trichinella species following exposure to oxidative, anthelminthic and thermal stress. Larvae of T. nativa, T nelsoni, T. pseudospiralis and T. spiralis were exposed to peroxide shock (0.2%, 1%, or 2% H(2)O(2)for 2h), high temperatures (40 degrees C or 45 degrees C for 2h), or 0.1 microg/ml of the benzimidazole anthelminthics: mebendazole (MBZ), albendazole (ALB) or thiabendazole (TBZ) for 4h. Following exposures, the L(1) were tested for induced morphological changes. Those observed were: (i) no change (in all species exposed to 40 degrees C) (ii) aberrant forms (in all species exposed to anthelminthics, in T. nativa, T. nelsoni and T. spiralis exposed to 45 degrees C, and in T. spiralis and T. nelsoni exposed to 0.2% H(2)O(2)) and (iii) severe degradation or death (in T. nativa and T. pseudospiralis exposed to 0.2% H(2)O(2), and in all species at 1% and 2% H(2)O(2)). In Western blot analyses, L(1) proteins were probed with monoclonal antibodies (mAbs) specific for the three HSPs. Greater changes in HSP levels occurred following H(2)O(2) exposure than with other stresses in all Trichinella species, while accumulation of a 50 kDa HSP was only observed in T. spiralis and T. pseudospiralis. Anthelminthic stress only caused decreased HSP levels in T. nativa. Thermal stress caused no significant changes in the HSP response of any species. It is suggested that other stress proteins (e.g., glucose-regulated proteins) may be involved in adaptation to thermal stress.