BIOLOGICAL DIVERSITY OF PARASITES WITHIN THE GENUS TRICHINELLA
AND THEIR TRANSMISSION IN DIFFERENT CLIMATIC ZOONES.
The nematodes in the genus Trichinella are among least host-specific helminths found. It has
been demonstrated from both experimental and epidemiological studies that Trichinella spp.
are able to infect most mammalian host species and that Trichinella pseudospiralis
additionally is able to infect birds. Thus, Trichinella spp. show a cosmopolitan distribution
from the poles to the tropics, infecting primarily mammals with scavenger and cannibalistic
behaviour. Adaptation to carnivores have favoured the long-term survival of Trichinella
larvae in host muscle tissue, the development of the a mechanism changing the host muscle
cell into a protective “nurse cell”, and for most of the genotypes the formation of a cyst wall
(capsule) around the nurse cell. Furthermore, anaerobic metabolism of encysted larvae
facilitates its survival in a decaying carrion, and some species are additionally able to tolerate
freezing, other slightly elevated temperature within the meat. Such adaptations have favour
the survival in hot and cold climates, respectively.
Because of the wide host spectrum, the direct life cycle, and the wide geographical
distribution, Trichinella has a high potential for interspecific transmission, but since the
different hosts have remarkably different susceptibility to the individual Trichinella genotypes
the epidemiology has become much more complex to evaluate.