Trichinella Infection in Hedgehogs and Bears

Disease Summary

Alternative Names (Synonyms)

• Trichinelliasis. (J171.124.w1) [Infection with Trichinella spiralis]
• Trichinosis (B46, B213.w2)
• Trichinellosis (B24) (B208.15.w15)

Disease Type

Infectious/Non-Infectious Agent associated with the Disease

• Trichinella spiralis. (B228.9.w9); the coiled larvae are found in striated muscle while adults are found in the small intestine. (B46)
• Several different species of Trichinella are now recognised. These vary in the resistance of the larvae to prolonged freezing within muscle and may be separated by variety of biochemical, molecular biology and PCR techniques. (B208.15.w15)

In bears: 

• Trichinella spiralis has been found in Ursus americanus - American black bear, Ursus thibetanus - Asiatic black bear and Ursus maritimus - Polar bear. (B336.51.w51)
• Trichinella murelli has been found in Ursus americanus - American black bear. (B336.51.w51)
• Trichinella nativa has been found in Ursus maritimus - Polar bear. (B336.51.w51)
• Trichinella nativa was confirmed in Ursus americanus - American black bear meat tested after a human patient developed suspected trichinellosis. Viable larvae were recovered from the meat of the bear, which had been frozen at -20 °C for four months, and from frozen meat of black bear meat from southern Ontario, Canada and upstate New York, USA. Multiplex PCR confirmed the freezing-resistant species Trichinella nativa from all three bears; this species had not previously been reported form the continental USA. (J32.132.w1)
• Trichinella spp. infection detected in Ursus americanus - American black bear from Pennsylvania was confirmed by dot-blot analysis of genomic DNA to be Trichinella T5 rather than Trichinella spiralis. (J13.55.w1)
• Trichinella spiralis has been found in Ursus americanus - American black bear in Pennsylvania, USA and in Ursus arctos - Brown bear in Alaska, USA. (B208.15.w15)
• Trichinella nativa has been found in Ursus arctos - Brown bear from Estonia and in Ursus maritimus - Polar bear from Alaska, Canada, Greenland, and the Svalbard Islands of Norway. (B208.15.w15)
• Trichinella britovi has been found in Ursus arctos - Brown bear from Italy and the Slovakian Republic, and in Ursus thibetanus - Asiatic black bear from Japan. (B208.15.w15)
• Trichinella T5 has been found in Ursus americanus - American black bear in Pennsylvania, USA. (B208.15.w15)
• Trichinella T6 has been found in Ursus americanus - American black bear and Ursus arctos - Brown bear in Montana, USA. (B208.15.w15)

Infective "Taxa"

• --

Non-infective agents

Physical agents

References

Disease Author

Major References / Reviews

Code and Title List

Other References

Code and Title List

Detailed Clinical and Pathological Characteristics

• In the intestines infection may cause irritation and, with very heavy infections, enteritis with associated diarrhoea. 
• The larval form in the muscles may cause acute myositis (resulting in muscle pain and stiffness of affected muscles), also fever, eosinophilia, myocarditis, periorbital oedema, retroperitoneal pain, ascites, dyspnoea and hoarseness. 
• Paralysis of the respiratory muscles may lead to death.

• Experimental infection causes diarrhoea, sloughing of intestinal epithelium and local intestinal haemorrhage. (B208.15.w15)
• Fever, loss of appetite and arrested growth may occur in infected domestic animals. (B208.15.w15)

• During the intestinal phase: diarrhoea, nausea, vomiting and general malaise (signs of gastroenteritis). (B272.4.w4)
  • Diarrhoea in experimentally infected laboratory and domestic animals. (B208.15.w15)
• During the muscular invasion stage: pyrexia, facial oedema, muscular swelling and pain, dyspnoea and anorexia. (B272.4.w4)
  • In pigs, also weight loss, hair coat roughening, periorbital oedema and signs of muscle involvement in the legs, particularly the hind legs. (B272.4.w4)
  • In rodents (rats and mice), listlessness, sluggish movements, fur roughening, conjunctival erythema and eyelid adhesions. (B272.4.w4)
  • In dogs and cats: emaciation, fur roughening, increased salivation, severe muscle pain; the animal may be unable to walk. (B272.4.w4)
• With cardiac invasion during massive infection: signs associated with myocarditis. (B272.4.w4)
• With nervous tissue invasion during massive infection: signs of neuritis or CNS disorders. (B272.4.w4)
• During the convalescent stage: reduced pyrexia, reduced pain. In humans, continued loss of weight, tiredness, desquamation of the skin and continuation of other signs associated with the muscular invasion stage may occur. (B272.4.w4)
• Note: behaviour may be affected, particularly by heavy infections, but also by relatively low infection rates, in ways which increase susceptibility to predation and change reproductive success. (B208.15.w15)

Clinical pathology:

• Eosinophilia may be present during the muscular invasion stage with moderate to heavy infections. (B272.4.w4)

Clinical Characteristics

• Trichinella sp. has been reported causing severe illness and death of Hemiechinus auritus collaris [Hemiechinus collaris] in India, after feeding on infected rat-tailed bats, Rhinopoma kinneari. (J178.53.w1)
• Signs included lethargy, anorexia, decreased responsiveness, severe ataxia, periodic violent trembling of the body, progressing to spasmodic breathing, liquid discharge from the nose and mouth, and death. 

(J178.53.w1)

Clinical signs, if present, may be similar to those seen in humans and in other carnivores: fever, facial oedema, muscular pain, dyspnoea, anorexia and eosinophilia. (B10.48.w43, B16.9.w9, B64.26.w5, D315.3.w3)

• In three Ursus maritimus - Polar bears at Basle Zoo and one Ursus arctos - Brown bear at Zurich Zoo, severe pruritus, with bears rubbing themselves on any object and scratching the skin with their claws sufficiently to draw blood, also increased rigidity of the forelimbs and the neck. (B214.3.4.w16)
• In a female Ursus maritimus - Polar bear, about 28 years old, at Knoxville Zoological Gardens
  • Partial anorexia and weight loss; progressive. (P36.1994.w6)
  • Stiff gait in the hind legs, progressing over about 18 months to non-weightbearing on one hind leg. (P36.1994.w6)
  • Non-regenerative anaemia, leucopaenia, hyperglobulinaemia and hyponatraemia. (P36.1994.w6)
• In European brown bears (Ursus arctos - Brown bear) in a Swedish zoo in 1976, there were no clinical signs reported. (B22.32.w15)
• It has been suggested that pain associated with larval migration could be a cause of abnormal behaviour occasionally observed in wild bears. (J345.3.w3)

Incubation

Mortality / Morbidity

• The prevalence of infection in Ursus maritimus - Polar bear increases with age. (B208.15.w15)

Pathology

• Intestinal: acute catarrhal enteritis. Mucosa thickened and hyperaemic, with punctate haemorrhages. In the intestinal wall, oedema and inflammatory cell invasion  with scattered monocytes, neutrophils and eosinophils. (B272.4.w4)
• Intestinal lymph nodes: large and soft. (B272.4.w4)

Muscular stage:

• Gross: 
  • Muscles firmer than normal. By about five weeks, in muscles greyish streaks may be visible. (B272.4.w4)
  • In rodents: diaphragm may have a pebbly appearance due to the cysts. (B272.4.w4)
• Histopathology:
  • Muscles: 
    • Initially (one or two days) basophilic granular degeneration of invaded fibres, loss of cross striations, loss of eosinophilia of fibres. (B272.4.w4)
    • After a few days: oedema of fibres, with swelling to about three times normal diameter by day 18, then reducing to normal by about five weeks post infection. (B272.4.w4)
    • Muscle fibres may be replaced by a network of granular threads. (B272.4.w4)
    • Leucocyte and lymphocyte invasion after about two weeks, then also macrophages. (B272.4.w4)
    • Coiling of larvae at about the 17th day of infection; larvae become surrounded by "a halo of homogenous and dens basophilic granular muscular detritus" which forms the inner part of the cyst, while the outer part is formed from the thickened sarcolemma. (B272.4.w4)
    • Marked increase in muscle nuclei, starting within a day of invasion and increasing by five days post infection to up to eight times normal numbers. These nuclei are oval are rounded, twice normal size, found near the interior of the muscle fibres, around the parasites, and remain trapped in the cyst for years. (B272.4.w4)
    • Neighbouring uninfected fibres may undergo hydropic degeneration or hyaline degeneration due to excess pressure, and cellular infiltration (neutrophils, eosinophils, lymphocytes and macrophages) may occur, particularly eosinophils, giving an eosinophilic myositis. (B272.4.w4)
    • Parasitised fibres degenerate, neighbouring fibres may regenerate to varying extents.
    • Interstitial connective tissue inflammation during the invasion may be replaced by fibrosis later. (B272.4.w4)
    • Calcification of cysts/trichinae by as soon as three months (usually 6-18 months in humans; in pigs sometimes as soon as six months but often not occurring even after two years). (B272.4.w4)

• In a Ursus maritimus - Polar bear: hundreds of encysted Trichinella larvae. (B10.48.w43)

Gross

• In a wild-caught Ursus maritimus - Polar bear at Melbourne Zoo, Australia :
  • Diaphragm: numerous white, spindle-shaped lesions, 0.3 - 0.5 mm long, similar to those seen with Sarcocystis infection. (J24.59.w1)

Histopathology

• In a wild-caught Ursus maritimus - Polar bear at Melbourne Zoo, Australia :
  • Diaphragm: encysted nematode larvae surrounded by degenerated muscle fibres. Cysts were elongated ovals, with a thick, homogenous, eosinophilic cell wall, sometimes calcifying, but larvae often appeared viable. Some proliferation of sarcolemma nuclei in nearby muscle fibres. A few lymphocytes were found around some cysts. (J24.59.w1)
• In a female Ursus maritimus - Polar bear, about 28 years old, at Knoxville Zoological Gardens:
  • Muscles: "moderate multifocal granulomatous myositis with intralesional encysted Trichinella sp."(P36.1994.w6)

Human Health Considerations

• Trichinellosis is an important zoonotic disease. The pork from the domestic pig is the most important species  from which humans acquire infection, as part of a synanthropic-zoonotic cycle involving primarily rats, pigs and mice. Human infection may also occur following consumption of  meat from wild animals. (B24, B46)
• Humans have been reported to be infected with trichinosis after consuming bear meat. (B336.51.w51)
• Animals become infected by ingestion of infected meat (predation, cannibalism, ingestion of carrion) or from ingestion of fresh faeces passed by an individual with a patent infection. (B46)
• Treatment is rarely required in animals. Both the adults and the larvae of Trichinella spiralis are susceptible to benzimidazole anthelmintics. (B46)
• Bear meat containing Trichinella larvae is a potential public health hazard. (J345.3.w2)
• Humans have acquired trichinosis from eating bear meat. (B336.51.w51)
• In northern Saskatchewan, Canada, an outbreak of trichinellosis occurred in two communities following consumption of infected bear meat, particularly dried meat. (J100.188.w3)
• In Thailand, an epidemic of trichinosis in a village in August 1967 was traced to consumption of raw Himalayan bear (Ursus thibetanus - Asiatic black bear) meat. (J98.1969i.w1)
• Meat from carnivores such as bears should be treated to destroy viable trichinae, by adequate cooking (e.g. to reach 137 °F for pork), or by freezing at - 20 °F for six days, or -10 °F for 10 days or 5 °F for 20 days. (B272.4.w4)
• Meat from bears should be thoroughly cooked before being eaten. (B16.9.w9, B64.26.w5)
• Note: Trichinella nativa and Trichinella T6 are able to survive prolonged freezing in muscle tissue at -5 to -18 °C. (J32.132.w1)
• In Alaska, human trichinosis, sometimes fatal, has occurred following consumption of meat from each of Ursus americanus - American black bear,  grizzly bear (Ursus arctos - Brown bear) and Ursus maritimus - Polar bear. (J11.42.w2)

Disease has been reported in either the wild or in captivity in:

• Trichinella sp. has been reported causing severe illness and death of Hemiechinus auritus collaris [Hemiechinus collaris] in India, after feeding on infected rat-tailed bats, Rhinopoma kinneari. (J178.53.w1)
• Trichinella spiralis larvae were recorded in the muscles of 3/8 West European hedgehogs Erinaceus europaeus during a survey in Belgium. (J171.124.w1) 
• Trichinella larvae, probably (using modern classification) Trichinella britovi have been isolated from hedgehogs Erinaceus europaeus in the Ukraine and from the Afghan hedgehog Hemiechinus megalotis [Hemiechinus auritus megalotis] in Afghanistan. (B208.15.w15)
• Trichinosis was identified in 4/52 (7.7%) hedgehogs Erinaceus europaeus [Erinaceus concolor] in the [former] USSR up to 1966. (B213.w2)

Bears

• Ursus americanus - American black bear, Ursus arctos - Brown bear (including the grizzly bear) and Ursus maritimus - Polar bear. (B272.4.w4)
• In Alaska, a survey detected Trichinella larvae in 52.9% of Ursus maritimus - Polar bear. (J11.42.w2)
• Trichinella spiralis were found in diaphragm muscle of 3/45 Ursus americanus - American black bears from New York (Adirondacks, plus five from Allegany State Park), 1956-1958. (J413.7.w1)
• Trichinella spiralis was NOT detected in the muscles of 25 bears examined by the compression and artificial digestion techniques, nor in 25 bears in which the diaphragm was examined by histopathology during a survey of black bears from six states in the southeastern USA, July 1973-November 1976. (J1.14.w10) 
• No Trichinalis spiralis were found in 28 diaphragms examined from hunter-killed Ursus americanus - American black bears in northern Wisconsin (1974-1975). (J1.14.w9) 
• Trichinella spiralis larvae were found in 61.3% of bears examined (98/160) during a study of grizzly bears (Ursus arctos - Brown bear) from Montana and Wyoming. Average intensity of infection was 51.1 larvae per gram of tongue (range 0.12-708). Older bears had higher prevalence of infection but lower intensity of infection than younger bears. [1976](J345.3.w3)
• Trichinella spiralis were found in 5/80 bears examined (6.3) during a study of Ursus americanus - American black bears from Montana and Wyoming. Average intensity of infection was 18.1 larvae per gram muscle (range 0.02-26.4 per gram). [1976](J345.3.w3)
• Trichinella spiralis has been found in Ursus americanus - American black bear, Ursus thibetanus - Asiatic black bear and Ursus maritimus - Polar bear. (B336.51.w51)
• Trichinella murelli has been found in Ursus americanus - American black bear. (B336.51.w51)
• Trichinella nativa has been found in Ursus maritimus - Polar bear. (B336.51.w51)
• In surveys, between 1% and 27.5% of Ursus americanus - American black bear have been seropositive for Trichinella spiralis. (B336.51.w51)
• In surveys, 3% to 58% of Ursus arctos - Brown bear from western Canada have been seropositive. (B336.51.w51)
• Trichinella spiralis have been found in wild Ursus americanus - American black bear in the US states of Alaska, Arizona, California, Colorado, Idaho, Michigan, Minnesota, Montana, New Mexico, New York, Oregon, Vermont, Wisconsin and Wyoming, and in New England. (J345.3.w2)
• Trichinella have been reported in wild Ursus maritimus - Polar bear from Alaska, Canada, Southampton Island (Canada), Greenland, Svalbard, the Norwegian and Barents Seas, Rudolph Land Island, north-eastern Siberia and "Palearctic". (J345.3.w2)
• Trichinella have been reported in wild Ursus arctos - Brown bear from Alaska, north-west Canada, Montana, California, USSR, north-east Siberia, eastern Siberia, the Caucasus mountains, Azerbaijan and Germany. (J345.3.w2)
• Trichinella infection has been reported in an Ursus thibetanus - Asiatic black bear from Thailand. (J345.3.w2)
• Trichinella spiralis larvae were fund in the diaphragms of 21/24 bears (87.5%) examined during a survey of grizzly bears (Ursus arctos - Brown bear) from northern Canada, 1965-196; four bears were from the Northwest territories. (J30.47.w1)
• A survey in the southwestern USA detected Trichinella spiralis in the tongue of one Ursus americanus - American black bear from Arizona and Trichinella murrelli (identified by multiple-PCR) in one of nine Ursus americanus - American black bear from New Mexico. (J11.87.w2)
• Trichinella nativa was confirmed by multiplex PCR in Ursus americanus - American black bear meat from three black bears from Plymouth, New Hampshire, southern Ontario, Canada and upstate New York, USA; this Trichinella species had not previously been reported form the continental USA. (J32.132.w1)
• Trichinosis has been reported in wild-born Ursus maritimus - Polar bear in captivity. (B336.51.w51)
• A survey carried out 1971-1976 detected Trichinella sp. in an Ursus maritimus - Polar bear shot on an ice floe in Trinity Bay, Newfoundland, but not in 51 Ursus americanus - American black bear from the Atlantic Provinces of Canada. (J240.42.w1)
• Antibodies to Trichinella sp. were detected by IHA or bentonite floculation test in 16/122 sera (13%) from Ursus americanus - American black bear from northcentral Idaho, 1971-1975. (J1.16.w12)
• A survey of tongue samples from hunter-killed Ursus americanus - American black bear in Arizona, 1978-1979, detected Trichinella sp. larvae in none of 21 samples collected in 1978 but larvae were found in two of 30 (7%) of samples collected during 1979. Samples from infected bears contained 406 trichinae per gram and 132 trichinae per gram; levels exceeding one trichinae per gram are considered capable of causing clinical infection in humans. (J1.17.w10)
• A survey of grizzly bears (Ursus arctos - Brown bear) (bears shot by hunters, or due to livestock depredations, or following human maulings, plus three road-killed bears) in Alberta, Canada, recovered Trichinella sp. larvae from only one of 35 bears. All bears killed from areas around the Rocky Mountains were negative; the single positive bear was from southwest Alberta. (J1.20.w10)
• A survey based on peptic digestion of tongue or diaphragm samples from 2,056 Ursus americanus - American black bear killed by hunters in Pennsylvania 1981-1983 detected Trichinella spiralis larvae in 37 bears (16 males, 21 females), giving an overall prevalence of 1.8%. The geometric mean density of larvae per gram of muscle tissue in infected bears was 7.8, and high densities, 300-913 larvae per gram) were detected in some bears, providing a basis for potential single-source outbreaks of severe human trichinosis. (J1.22.w7)
• A survey of tongue and diaphragm samples from Ursus americanus - American black bear from Labrador and Newfoundland, Canada, detected Trichinella spiralis in one of 96 bears from Labrador and none of 62 from Newfoundland. Black bears do not appear to be involved in the sylvatic cycle of Trichinella spiralis in eastern Canada. (J1.28.w14)
• ELISA of sera collected from 878 grizzly bears Ursus arctos - Brown bear in seven areas of Alaska, 1973-1987, detected antibodies in 87% (194/224) of bears from Northwest Alaska, 78% (161/206) of bears from northeast Alaska 26% (40/153) of bears from southcentral interior Alaska, 22% (22/99) of bears from central interior Alaska, 22% (4/18) of bears from the Alaska Peninsula, 15% (4/27) of bears from the southeastern Islands and 1% (2/151) of bears from Kodiak Island. (J1.33.14)
• Antibodies to Trichinella spp. were detected by a modified ELISA in 55.6% of Ursus maritimus - Polar bear from the Beauford and Chukchi seas, from samples collected 1982-1999. The prevalence of antibodies to Trichinella spp. increased with age. (J3.156.w2)
  Antibodies to Trichinella spiralis were detected by latex particle agglutination in 18/141 sera (13%) from Ursus americanus - American black bear from California, USA. [1982](J4.181.w4)
• Trichinella larvae were found in 10 of 20 grizzly bears (Ursus arctos - Brown bear) from Alaska (1949-1953), at 0.1 - 45.6 larvae per gram of muscle (average 12.4 per gram). (J11.42.w2)
• Trichinella larvae were found in five of 23 Ursus americanus - American black bear from Alaska (1949-1953)(21.7 %), with 0.5 - 400 larvae per gram, average 81 per gram. (J11.42.w2)
• Trichinella larvae were found in nine of 17 (52.9%) polar bears Thalarctos maritimus (Ursus maritimus - Polar bear) from Alaska (1949-1953), but infections were light, 0.4 - 4.0 larvae per gram, average 1.6 per gram. (J11.42.w2)
• Trichinella larvae were found in the tongues of two of 544 Ursus americanus - American black bear (0.37%) from New Brunswick, eastern Canada, 1989-1991. Both infected animals were adult males, 5.5 years old; infection intensity was 3.3 larvae/gram for one bear, 30.7 larvae/gram for the other. (J11.80.w1)
• A survey in Finland detected Trichinella infection in 14/150 brown bears (Ursus arctos - Brown bear) (9%), with a median of 2.8 larvae per gram, range 0.05-72. Identification of species revealed Trichinella nativa in the three brown bears tested. (J11.88.w1)
• Using ELISA, Trichinella spp. infection was detected in six of 319 bears (1.8%) in Ursus americanus - American black bear from Pennsylvania. (J13.55.w1)
• In a wild-caught Ursus maritimus - Polar bear at Melbourne Zoo, Australia. (J24.59.w1)
• A study in Germany detected Trichinella spiralis in meat from a grizzly bear from Alaska. Trichinella nativa was detected in a polar bear from Berlin Zoo. (J32.87.w1)
• Trichinella infection in Ursus maritimus - Polar bear is found throughout the Arctic region (holarctic distribution). (J32.93.w1)
• Trichinella spiralis has been found in Ursus americanus - American black bear in Pennsylvania, USA and in Ursus arctos - Brown bear in Alaska, USA. (B208.15.w15)
• Trichinella nativa has been found in Ursus arctos - Brown bear from Estonia and in Ursus maritimus - Polar bear from Alaska, Canada, Greenland, and the Svalbard Islands of Norway. (B208.15.w15)
• Trichinella britovi has been found in Ursus arctos - Brown bear from Italy and the Slovakian Republic, and in Ursus thibetanus - Asiatic black bear from Japan. (B208.15.w15)
• Trichinella T5 has been found in Ursus americanus - American black bear in Pennsylvania, USA. (B208.15.w15)
• Trichinella T6 has been found in Ursus americanus - American black bear and Ursus arctos - Brown bear in Montana, USA. (B208.15.w15)
• Trichinella spp. have been detected in Ursus americanus - American black bear from Pennsylvania, West Virginia, Minnesota and New England. (B208.15.w15)
• Trichinella infection occurred in European brown bears (Ursus arctos - Brown bear) in fenced enclosures in a Swedish zoo in 1976. (B22.32.w15)
• Trichinae were NOT detected in two Ursus americanus - American black bear and one Ursus maritimus - Polar bear (captive) during a survey of wildlife in Iowa. (J101.90.w1)

• Antibodies to Trichinella spp. were detected by ELISA in 277/568 (49%) Ursus arctos - Brown bear and 11/76 (14.5%) Ursus americanus - American black bear in Alaska (samples collected1988-1991). (J64.17.w1)

• ELISA of serum samples from hunter-killed Ursus americanus - American black bears from North Carolina, 1996-1997,  failed to detect antibodies to Trichinella spiralis in 143 individuals. (J11.84.w3)

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

Host Species List

• Erinaceus europaeus - West European Hedgehog
• Erinaceus concolor - East European hedgehog
• Hemiechinus auritus - Long-eared hedgehog
• Hemiechinus collaris - Indian long-eared hedgehog
• Ursus americanus - American black bear
• Ursus arctos - Brown bear
• Ursus thibetanus - Asiatic black bear
• Ursus maritimus - Polar bear

(List does not contain all other species groups affected by this disease)

Disease has been specifically reported in Free-ranging populations of:

• Trichinella spiralis larvae were recorded in the muscles of 3/8 West European hedgehogs Erinaceus europaeus during a survey in Belgium. (J171.124.w1) 
• Trichinella larvae, probably (using modern classification) Trichinella britovi have been isolated from hedgehogs Erinaceus europaeus in the Ukraine and from the Afghan hedgehog Hemiechinus megalotis [Hemiechinus auritus megalotis] in Afghanistan. (B208.15.w15)
• Trichinosis was identified in 4/52 (7.7%) hedgehogs Erinaceus europaeus [Erinaceus concolor] in the [former] USSR up to 1966. (B213.w2)

Bears

• Ursus americanus - American black bear, Ursus arctos - Brown bear (including the grizzly bear) and Ursus maritimus - Polar bear. (B272.4.w4)
• Trichinella spirallis were found in diaphragm muscle of 3/45 Ursus americanus - American black bears from New York (Adirondacks, plus five from Allegany State Park), 1956-1958. (J413.7.w1)
• In Alaska, a survey detected Trichinella larvae in 52.9% of Ursus maritimus - Polar bear. (J11.42.w2)
• Trichinella spiralis was NOT detected in the muscles of 25 bears examined by the compression and artificial digestion techniques, nor in 25 bears in which the diaphragm was examined by histopathology during a survey of Ursus americanus - American black bear from six states in the southeastern USA, July 1973-November 1976. (J1.14.w10) 
• Trichinella spiralis has been found in Ursus americanus - American black bear, Ursus thibetanus - Asiatic black bear and Ursus maritimus - Polar bear. (B336.51.w51)
• Trichinella murelli has been found in Ursus americanus - American black bear. (B336.51.w51)
• Trichinella nativa has been found in Ursus maritimus - Polar bear. (B336.51.w51)
• In surveys, between 1% and 27.5% of Ursus americanus - American black bear have been seropositive for Trichinella spiralis. (B336.51.w51)
• In surveys, 3% to 58% of Ursus arctos - Brown bear from western Canada have been seropositive. (B336.51.w51)
• Trichinella spiralis have been found in wild Ursus americanus - American black bear in the US states of Alaska, Arizona, California, Colorado, Idaho, Michigan, Minnesota, Montana, New Mexico, New York, Oregon, Vermont, Wisconsin and Wyoming, and in New England. (J345.3.w2)
• Trichinella have been reported in wild Ursus maritimus - Polar bear from Alaska, Canada, Southampton Island (Canada), Greenland, Svalbard, the Norwegian and Barents Seas, Rudolph Land Island, north-eastern Siberia and "Palearctic". (J345.3.w2)
• Trichinella have been reported in wild Ursus arctos - Brown bear from Alaska, north-west Canada, Montana, California, USSR, north-east Siberia, eastern Siberia, the Caucasus mountains, Azerbaijan and Germany. (J345.3.w2)
• Trichinella infection has been reported in an Ursus thibetanus - Asiatic black bear from Thailand. (J345.3.w2)
• A survey in the southwestern USA detected Trichinella spiralis in the tongue of one Ursus americanus - American black bear from Arizona and Trichinella murrelli (identified by multiple-PCR) in one of nine Ursus americanus - American black bear from New Mexico. (J11.87.w2)
• Trichinella nativa was confirmed by multiplex PCR in Ursus americanus - American black bear meat from three black bears from Plymouth, New Hampshire, southern Ontario, Canada and upstate New York, USA; this Trichinella species had not previously been reported form the continental USA. (J32.132.w1)
• Trichinella larvae were found in the tongues of two of 544 Ursus americanus - American black bear (0.37%) from New Brunswick, eastern Canada, 1989-1991. Both infected animals were adult males, 5.5 years old; infection intensity was 3.3 larvae/gram for one bear, 30.7 larvae/gram for the other. (J11.80.w1)
• Trichinosis has been reported in wild-born Ursus maritimus - Polar bear in captivity. (B336.51.w51)
• A survey carried out 1971-1976 detected Trichinella sp. in an Ursus maritimus - Polar bear shot on an ice floe in Trinity Bay, Newfoundland, but not in 51 Ursus americanus - American black bear from the Atlantic Provinces of Canada. (J240.42.w1)
• A survey of tongue samples from hunter-killed Ursus americanus - American black bear in Arizona, 1978-1979, detected Trichinella sp. larvae in none of 21 samples collected in 1978 but larvae were found in two of 30 (7%) of samples collected during 1979. Samples from infected bears contained 406 trichinae per gram and 132 trichinae per gram; levels exceeding one trichinae per gram are considered capable of causing clinical infection in humans. (J1.17.w10)
• A survey of grizzly bears (Ursus arctos - Brown bear) (bears shot by hunters, or due to livestock depredations, or following human maulings, plus three road-killed bears) in Alberta, Canada, recovered Trichinella sp. larvae from only one of 35 bears. All bears killed from areas around the Rocky Mountains were negative; the single positive bear was from southwest Alberta. (J1.20.w10)
• A survey based on peptic digestion of tongue or diaphragm samples from 2,056 Ursus americanus - American black bear killed by hunters in Pennsylvania 1981-1983 detected Trichinella spiralis larvae in 37 bears (16 males, 21 females), giving an overall prevalence of 1.8%. The geometric mean density of larvae per gram of muscle tissue in infected bears was 7.8, and high densities, 300-913 larvae per gram) were detected in some bears, providing a basis for potential single-source outbreaks of severe human trichinosis. (J1.22.w7)
• A survey of tongue and diaphragm samples from Ursus americanus - American black bear from Labrador and Newfoundland, Canada, detected Trichinella spiralis in one of 96 bears from Labrador and none of 62 from Newfoundland. Black bears do not appear to be involved in the sylvatic cycle of Trichinella spiralis in eastern Canada. (J1.28.w14)
• ELISA of sera collected from 878 Ursus arctos - Brown bears in seven areas of Alaska, 1973-1987, detected antibodies to Trichinella in 87% (194/224) of bears from Northwest Alaska, 78% (161/206) of bears from northeast Alaska 26% (40/153) of bears from southcentral interior Alaska, 22% (22/99) of bears from central interior Alaska, 22% (4/18) of bears from the Alaska Peninsula, 15% (4/27) of bears from the southeastern Islands and 1% (2/151) of bears from Kodiak Island. (J1.33.14)
• A study in Germany detected Trichinella spiralis in meat from a grizzly bear from Alaska. Trichinella nativa was detected in a polar bear from Berlin Zoo. (J32.87.w1)
• Trichinella infection in Ursus maritimus - Polar bear is found throughout the Arctic region (holarctic distribution). (J32.93.w1)
• Using ELISA, Trichinella spp. infection was detected in six of 319 bears (1.8%) in Ursus americanus - American black bear from Pennsylvania. (J13.55.w1)
• Trichinella spp. antibodies were detected in 6/319 sera (1.8%) from Ursus americanus - American black bear from Pennsylvania, in muscle digests from 2/63 bears and on histological examination of muscles in 3/162 bears. (J13.55.w1)
• ELISA of serum samples from hunter-killed Ursus americanus - American black bears from North Carolina, 1996-1997,  failed to detect antibodies to Trichinella spiralis in 143 individuals. (J11.84.w3)

Further information on Host species has only been incorporated for  species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

Host Species List

• Erinaceus europaeus - West European Hedgehog
• Erinaceus concolor - East European hedgehog
• Hemiechinus auritus - Long-eared hedgehog
• Ursus americanus - American black bear
• Ursus arctos - Brown bear
• Ursus thibetanus - Asiatic black bear
• Ursus maritimus - Polar bear

(List does not contain all other species groups affected by this disease)

General Information on Environmental Factors/Events and Seasonality

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Regions / Countries where the Infectious Agent or Disease has been recorded

• This parasite is found almost worldwide: it appears not to be present in Australia. (B46)

Regions / Countries where the Infectious Agent or Disease has been recorded in Free-ranging populations

• Trichinella infection in Ursus maritimus - Polar bear is found throughout the Arctic region (holarctic distribution). (J32.93.w1)
• Distribution of Trichinella spp. is probably underestimated. There are records from North America, South America, Eurasia, Greenland and Africa. (B208.15.w15)

General Information on Investigation / Diagnosis

• Detection of trichinae in muscles using the compression method, artificial digestion or microscopic examination. (B272.4.w4)
• Examination of peptin muscle digests: 250 ml of 0.52% HCl-pepsin solution added to a muscle sample (10-50 g) which had been homogenised with 0.85% NaCl (saline) in a blender, the mixture then being incubated at 37 C in a shaking water bath for one hour. After settling for 20 minutes, supernatant was aspirated to leave 50 ml which was poured into a gridded petri dish and examined at 20 x magnification using stereomicroscopy. (J13.55.w1)
• Detection by examination of histological sections of muscle. (J13.55.w1)
• Pieces of striated muscle, usually from the diaphragm, tongue or intercostals, are compressed between glass slides and examined using a dissecting microscope. (B208.15.w15)
• Muscle can be digested in 1% HCl pepsin for several hours at 37 C, the digest filtered through a fine metal screen (number 80 mesh) and larvae counted to give larvae pr gram of muscle. (B208.15.w15)
• Note: Trichinella pseudospiralis larvae do not encyst and are more difficult to detect. (B208.15.w15)
• Adult Trichinella nematodes in the intestines may be detected microscopically, associated with epithelium and mucus, but are present for only about 10-12 days. (B208.15.w15)

In the live host:

• Haematology: eosinophilia, detectable from about 10-14 days post infection, peaking at three to four weeks then declining over several months. Eosinophils may increase to 10-15% of wbc or with heavy infections even to 30-50%. There is often also a leucocytosis. (B272.4.w4)
• Serological tests (antibodies detectable by about three weeks of infection) such as the complement fixation test, precipitin test, fluorescent antibody test, latex agglutination test, indirect haemagglutination test, bentonite flocculation, charcoal agglutination, cholesterol flocculation. (B272.4.w4)
  • Note: Different tests vary in their effectiveness in different species. (B272.4.w4)
• ELISA can be used to detect Trichinella spp. infection in a range of species including humans, horses, domestic pigs, Ursus americanus - American black bear and Ursus maritimus - Polar bear. (J1.33.14)
• ELISA can be used to detect Trichinella spp. infection in Ursus americanus - American black bear. (J13.55.w1)

• Suspect in an individual with muscle pain and eosinophilia. (B16.9.w9, B64.26.w5)
• Confirmation by detection of larvae on microscopic examination of a skeletal muscle biopsy. (B16.9.w9, B64.26.w5)

• History & Documentation
• Physical Examination of Mammals
• Necropsy of Mammals
• Environmental Assessment
• Treatment and Care
• Chapter 2 - B36 Field Manual of Wildlife Diseases - Specimen Collection and Preservation
• Chapter 3 - B36 Field Manual of Wildlife Diseases - Specimen shipment
• Appendix A - B36 Field Manual of Wildlife Diseases - Sample specimen history form

Similar Diseases (Differential Diagnosis)

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Specific Medical Treatment

• Thiabendazole, 25 - 50 mg/kg. (B16.9.w9, B64.26.w5)
• In humans, albendazole or mebendazole are used. (D315.3.w3)
• Steroids may be useful to reduce muscle pain. (B16.9.w9)

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General Nursing and Surgical Techniques

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Preventative Measures

• Thiabendazole has been found to be effective used prophylactically in pigs and in laboratory animals. (B272.4.w4)

• Preventative Medicine for Mammals

Environmental and Population Control Measures

• Carcasses of meat-eating species should be buried or otherwise made unavailable to scavengers. (B272.4.w4)
• Replace open garbage dumps with other types of dumps such that meat scraps are not available to scavengers. (B272.4.w4)
• Around open garbage dumps, employ rodent control and fence the area to prevent larger mammals from scavenging. (B272.4.w4)

BEARS

• Avoid feeding meats which could contain the parasite, or cook the meat. (D315.3.w3)

• Environmental and Population Management - General