PCR Detection of Microbial Pathogens PCR Detection of Microbial ...

PCR Detection of Trichinella 299
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PCR-Derived Methods
for the Identification of Trichinella Parasites
from Animal and Human Samples
Edoardo Pozio and Giuseppe La Rosa
1. Introduction
Trichinella worms (family: Trichinellidae; phylum: Nematoda) are parasites
that mainly infect mammals, including humans, although they have been found
in birds and, recently, in African crocodiles (1,2). The main reservoir is represented
by carnivores with cannibalistic and scavenger behavior. These parasites
are widespread on all continents but Antarctica, from frigid to torrid zones.
The main distinguishing feature of their life cycle is that two generations occur
in the same host. The first generation (from L1 larva to adult) is present in the
gut and the second generation (from a newborn larva of 80 µm in length to an
infective larva of 0.6–1.0 mm in length) is present in the cell of striated muscles
that is modified by the larva (referred to as the nurse cell) (3,4).
Until 1972, Trichinella spiralis was the only known Trichinella species.
At present, seven species and three additional genotypes are known to exist
(Table 1) (2). An additional Trichinella genotype has been recently identified
in crocodiles from Zimbabwe, but its taxonomic status have yet to be
established. The individual species or genotypes cannot be distinguished on
the basis of morphological characters. Nonetheless, the species and genotypes
can be categorized into two groups based on whether or not a collagen
capsule surrounds the nurse cell in host muscles: when the collagen capsule
is present, the species or genotype is referred to as encapsulated; if absent,
the term nonencapsulated is used. The presence of the collagen capsule is
important for the long-term survival of the larva in decaying muscle tissue
(i.e., when the larva is not protected by the host homeothermy).
From: Methods in Molecular Biology, vol. 216: PCR Detection of Microbial Pathogens: Methods and Protocols
Edited by: K. Sachse and J. Frey © Humana Press Inc., Totowa, NJ
299