Trichinella species are present throughout most of the world in over 150 different hosts (Dick et al., 2001). In
addition to T. spiralis, 7 other species in 4 genotypes, all of which are more commonly found in wild animals than in
domestic pigs . T. spirals is cosmopolitan, this species is also the most important etiological agent to cause disease in
humans (Pozio et al., 2006). In the domestic cycle, pork scraps from T. spiralis-infected pigs are the main source of
infection for synanthropic animals (e.g., rats, horses, stray cats, and dogs). Conversely to the domestic cycle, the sylvatic
cycle of T. spiralis includes a broad range of wild carnivores, which may, however, become the origin of a life cycle
beginning into a domestic host population (Dick, 2001). Trichinella native is found in Arctic and subarctic areas of
America, Asia, Europe. Trichinella genotype T6 is also found in Canada, Alaska, Rocky Mountains, and Appalachian
Mountains in the United States (Pozio, 2001). Trichinella britovi is found in the temperate areas of Europe and Asia,
Northern and Western Africa, Trichinella T8 is found in South Africa and Namibia. Trichinella murrelli is found in the United
States and Southern Canada, Trichinella genotype T9 Japan, T. nelsoni Eastern-Southern Africa, and Trichinella genotype
T12 is found in Argentina, and all the above are encapsulated while the below are non-capsulated. Those are T.
pseudospiralis which is cosmopolitan in Palearctic, Nearctic, Ocean land (Pozio, 2001) Cosmopolitan , T. papuae is found
in the Papua New Guinea, Thailand and T. zimbabwensis which is found in Zimbabwe, Mozambique, Ethiopia, South Africa
The epidemiology and systematics (i.e., the study of the diversification) of this zoonosis are now recognized to
involve in addition to T. spiralis, 7 other species in 4 genotypes, all of which are more commonly found in wild animals
than in domestic pigs (Pozio, 2009). T. spiralis is found in the Domestic and sylvatic mammal, while Trichinella T8, T.
murrelli, Trichinela genotype T9. Trichinella native and Trichinella genotype T6 is found in the sylvatic carnivores. Another
species, T. britovi is found in the Sylvatic mammals and seldom domestic pigs, while T. nelson in the Sylvatic mammals.
Trichinella genotype T12, T. Pseudo spiralis Sylvatic mammals and birds, domestic pigs, T. papuae Wild pigs, salt water
crocodiles and T.zimbabwensis which is found in the Nile crocodiles, monitor lizards (Gottstein, 2009).
Main source of infection in human
Domestic pigs and wild boars were the major sources of Trichinella spp. infection for humans, but in recent years
new infection sources, particularly from exotic hosts, have emerged (Boireau, 2000). The main source of infection in
human, T. spiralis is found in the Domestic and sylvatic swine horses, while T. native is found in Bears, walruses. Others
like Trichinella genotype T6 is found in Carnivores T. britovi is found in the Wild boars, domestic pigs horses, foxes, jackals
T. zimbabwensis, Trichinella genotype T12, Trichinella genotyp T8 and Trichinella genotype T9. Trichinella murrelli in
Bears, especially horses while T. nelson is found in the Warthogs, bush pigs Warthogs, bush pigs, T. papuae is found in the
Resistance of larvae in frozen muscle
Most of them are not resistance to the frozen muscle. Trichinella T8, T. murrelli, T.pseud ospiralis T. papuae and
T.zimbabwensis, while others are T. spiralis resistance in horse muscles. T. native are resistance in carnivore muscles.
Trichinella genotype T6 is resistance in carnivore muscles, T. britovi are resistance in carnivore and horse muscles and
Trichinella genotype T12 Unknown (Gottstein, 2009). The epidemiology of trichinellosis is summarized as below in table 1.
The usual source of trichinosis in humans is from eating pork products or meat from horses, dogs, or a variety of
wildlife species, including wild pig, bear, walrus, and seal. Trichinella spp. is transmitted by two specific cycles, the
The domestic cycle is prevalent on small farms where disease control is not a primary objective in food production.
Areas where infection is endemic are found throughout the world (Dupouy- Camet, 2000). The domestic cycle of
transmission is primarily involves T. spiralis in a cycle of pig-to-pig transmission, and humans enter the cycle through
eating pork. The infection can be highly pathogenic in humans. Synanthropic rats, mice, cats, dogs, and horses, as well as
many wildlife species, also contribute to the cycle in many areas. Pigs maintain the cycle by eating pieces of infected
meat scraps, eating infected rats or mice, biting the tails of infected pigs, cannibalizing dead pigs, ingesting feces from
The sylvatic cycle of transmission predominantly involves predation, cannibalism, or scavenging behaviours of
species of carnivorous wildlife. Trichinella spp. are transmitted when fresh, frozen, or decomposing carcasses or meat
scraps are eaten (Dupouy-Camet, 2000). The species of Trichinella associated with the sylvatic cycle are T. nativa, T.
britovi, T. murrelli, T. nelsoni, T. pseudospiralis, T. papuae and T. zimbabwensis. T. spiralis can also affect wildlife in
temperate and tropical regions, but it does not survive in arctic and subarctic regions because larvae do not survive in a
The severity of the clinical course depends firstly on parasitic factors, such as the species involved and the number
of infective larvae ingested, and secondly on host factors, such as sex, age, and immune status (Bruschi and Murrell,
Citation: Yayeh M, Yadesa G , Erara M, Fantahun S, Gebru A and Birhan M (2020). Epidemiology, diagnosis and public health importance of Trichinellosis. Online J.