DISEASE SUMMARY PAGE

Cestode Infections in Bears

Summary Information
Diseases / List of Parasitic Diseases / Disease summary
Alternative Names Tapeworms in bears
Disease Agents
  • Taenia krabbei (B16.9.w9) = Taenia ovis krabbei (B208.7.w7)
    • Taenia krabbei uses cervids as intermediate hosts, with the cysts found in the muscles of the deer. (B64.26.w5)
  • Taenia hydatigena (B16.9.w9, B208.7.w7)
  • Diphyllobothrium latum (B16.9.w9)
  • Multiceps serialis (B16.9.w9)
  • Diphyllobothrium ursi were found in and first described from Ursus arctos middendorffi (Ursus arctos - Brown bear) around Karluk Lake-Uyak Bay on Kodiak Island, Alaska. (J11.40.w1)
  • Diphyllobothrium cordatum were found in a bear from Yellowstone Park, Wyoming, August 1932. (J11.19.w1)

  • Taenia saginata. (D274)

The life cycle of cestodes is indirect, with an intermediate host (e.g. rodents, ruminants) required. (B22.32.w15)

See also infections with larval forms:

Infectious Agent(s)
Non-infectious Agent(s) --
Physical Agent(s) --
General Description Infection is uncommon in captive carnivores, and clinical disease is rare. (B22.32.w15)

Adult tapeworms may cause: (B272.7.w7)

  • Intestinal blockage, if there are large or numerous strobila;
  • Toxic or allergic reactions (generalised);
  • Mechanical irritation of the intestinal mucosa,
  • Host deprivation of nutrients, particularly carbohydrates;
  • A means of bacterial invasion (where scolices are attached to the intestinal mucosa);
  • Loss of proteins and vitamins.

(B272.7.w7)

Note: the broad fish tapeworms Diphyllobothrium spp. are able to absorb large amounts of vitamin B12 from their host's gut, which could result in pernicious anaemia (this occurs in humans with Diphyllobothrium infections). (J345.3.w3)

Clinical signs 

  • Tapeworms such as Taenia spp. in carnivores may cause loss of body condition, diarrhoea or constipation, and anaemia. (B22.32.w15)
    • Clinical signs are most likely to be seen in young animals with heavy cestode burdens. (B22.32.w15)
  • A female Ursus americanus - American black bear shot as a nuisance near Yellowstone Lake, Yellowstone Park, was in poor condition. (J332.13.w1)
  • A nine-month-old (approx.) Ursus americanus - American black bear which had been experimentally infected with Diphyllobothrium s. from the upper Kenai Peninsula, Alaska, was found dead, 3.5 months after being experimentally infected with Diphyllobothrium sp. plerocercoid larvae. (J381.22.w1)

Gross pathology

In a female Ursus americanus - American black bear

  • General: poor physical condition for the time of year. (J332.13.w1)
  • GIT: In the intestines, one incomplete occlusion of the lumen and two complete occlusions, and two invaginations of the intestines. About 100 tape worms Diphyllobothrium latum, 46-84 cm long, were present in the intestines. (J332.13.w1)

In an experimentally infected Ursus americanus - American black bear cub

  • Pancreas: Enlarged. Necrotic lesion on the antero-ventral surface, 7 mm diameter, 5 mm deep. (J381.22.w1)
  • Duodenum: protruding from each of the two pancreatic ducts, the strobila of a Diphyllobothrium sp. cestode, with the scolices and anterior parts of the strobilae penetrating a considerable distance up the pancreatic ducts. The papillae of the ducts were enlarged and oedematous. (J381.22.w1)

Histopathology

In an experimentally infected Ursus americanus - American black bear cub.

  • Duodenum: 
    • Pancreatic ducts completely occluded by the strobilae and the associated inflammatory reaction. The ducts were necrotic, and contained many neutrophils. (J381.22.w1)
    • An abscess was present connected to one duct and had ruptured into the peritoneal cavity. The abscess cavity was filled with neutrophils; there was fibrinopurulent exudate over the surface of the organ and there were numerous eggs trapped in the exudate. (J381.22.w1)
  • Pancreas: Areas adjacent to the abscess showed chronic inflammation, with fibrosis, replacement of gland lobules, and localised hyperplasia of pancreatic duct epithelium. Many eggs were found distributed through the pancreas, some being deep in the tissue of lobules (mainly without much associated inflammatory reaction), while some were surrounded by dense connective tissue. There was local inflammatory reaction: eggs surrounded by macrophages and undergoing phagocytosis and degeneration. On the serosal surface of the pancreas, aggregations of escaped eggs were enclosed by a thin layer of neutrophils. (J381.22.w1)

Nutritional effects on cestodes

  • Development of some cestodes is enhanced by a carbohydrate-rich diet. (B272.7.w7)
  • Certain vitamin deficiencies reduce the ability of some cestodes to establish themselves and reproduce. (B272.7.w7)
  • In bears, seasonal dietary changes (e.g. from fish in summer to grass in fall) may have the effect of eliminating cestode burdens. (B272.7.w7, J332.13.w1)
Further Information

Diagnosis:

  • Examination of faeces for proglottids (diagnosis is usually by finding these) or eggs. (B16.9.w9, B22.32.w15, B64.26.w5)
  • Groups (e.g. Taenia spp.) or species are distinguished based on morphological characteristics of the eggs, proglottids and scolex. (B272.7.w7)

Treatment:

  • Praziquantel, 5 mg/kg subcutaneously or orally is the preferred treatment for tapeworms. (B22.32.w15, B407.w18)
  • For treatment of Taenia spp., other options are:
    • Fenbendazole, 50 mg/kg orally, repeated daily for a total of three doses. (B22.32.w15)
    • Niclosamide, 100 - 200 mg/kg orally, single dose. (B22.32.w15)
  • Bunamidine HCl (Scoloban, Cooper) at 100 mg/5kg body weight, maximum 800 mg can be used. (B16.9.w9)

Seasonality:

  • An analysis of faecal samples from Ursus americanus - American black bears in Quebec showed that the prevalence of eggs of Diphyllobothrium ursi was high in autumn (October and November) prior to denning (found in 70% of samples) but lower (21%) in spring (May), returning to higher levels (50%) by the following fall. This may indicate expulsion of adult egg-laying worms prior to bear hibernation, or that worms persist but destrobilate and resume proglottization in spring. (J1.14.w11)

Occurrence:

  • Relatively common in free-ranging bears, although less common than nematode infections. (B16.9.w9)
  • Low incidence in captive carnivores. (B22.32.w15)
  • In Yellowstone Park, at Yellowstone Lake in August 1931, Diphyllobothrium latum was found at necropsy in one female Euarctos americanus americanus (Ursus americanus - American black bear); capture and treatment of a further five bears, ranging in age from cub to adult, resulted in the cestodes being passed by three of the bears; no worms were passed, and no ova were detected in the faeces, of two large males. Similar testing by treatment of two black bears and three grizzlies from other locations in October did not reveal infection. (J332.13.w1)
  • Taenia krabbei has been found in Ursus arctos - Brown bear and Ursus americanus - American black bear (B64.26.w5, B272.7.w7)
  • Diphyllobothrium ursi were found in and first described from Ursus arctos middendorffi (Ursus arctos - Brown bear) around Karluk Lake-Uyak Bay on Kodiak Island, Alaska. Infection was induced in young Ursus americanus - American black bear by feeding plerocercoid larvae from cysts on the serosa of the stomachs of red salmon from streams tributary to Karluk Lake. (J11.40.w1)
  • Two of seven intestinal tracts from Ursus americanus - American black bears of Minnesota examined during the summer contained taeniid cestodes. The parasites from one bear were tentatively identified as Multiceps serialis Gervais, 1847; the usual intermediate host in Minnesota is Lepus americanus - snowshoe hare, and bears were observed scavenging on carcasses of these hares along roadsides. (J1.11.w11)
  • No faeces from black bears of Minnesota collected 1968-9 were found to contain Diphyllobothrium sp. strobilae. (J1.11.w11)
  • Taenia krabbei and Taenia hydatigena were found in 4% of Ursus americanus - American black bears during a study in Quebec, Canada, June 1971-November 1972. (J1.13.w11)
  • Diphyllobothrium ursi were found in 36% of Ursus americanus - American black bears during a study in Quebec, Canada, June 1971-November 1972. (J1.13.w11)
  • Taenia krabbei (gravid adults) were found in the small intestines of 10/91 Ursus americanus - American black bears (11%) during a study in northwestern Alberta, Canada, May 1976-September 1977. There were 1-30 (mean 7.9) adult cestodes per bear. (J1.15.w10)
  • Taenia hydatigena (gravid adults) were found in the small intestines of 3/91 Ursus americanus - American black bears (3.3%) during a study in northwestern Alberta, Canada, May 1976-September 1977. There were four to five of these worms per infected bear. (J1.15.w10)
  • Diphyllobothrium cordatum were found in a bear from Yellowstone Park, Wyoming, August 1932. (J11.19.w1)

  • Diphyllobothrium sp. were found in 24.2% of bears (16/66) during a study of grizzly bears (Ursus arctos - Brown bear) from Montana and Wyoming. Average intensity of infection was 49.6 ml of tapeworm biomass (range 0.1-379 ml).[1976](J345.3.w3)
  • Taenia sp. were found in 21.2% (14/66) of bears during a study of grizzly bears (Ursus arctos - Brown bear) from Montana and Wyoming. Average intensity of infection was 71.5 ml of tapeworm biomass (range 15.5-145 ml).[1976](J345.3.w3)
  • Diphyllobothrium sp. tapeworms were found in the small intestines of 2/30 bears (6.6%) during a study of Ursus americanus - American black bears from Montana and Wyoming. Average intensity of infection was 11.5 mL of cestode biomass per bear (range 0.2-20 mL). [1976](J345.3.w3)
  • Taenia sp. were found in in the small intestines of 2/30 bears (6.6%) during a study of Ursus americanus - American black bears from Montana and Wyoming. [1976](J345.3.w3)
  • Taenia krabbei were found in the small intestines of three of 12 intestinal tracts (25%) examined from Ursus americanus - American black bear from New Brunswick, eastern Canada, 1989-1991. Intensity of infection was range three to six, mean four cestodes per bear. (J11.80.w1)
  • Diphyllobothrium ursi were found in three of 21 bears during a survey of grizzly bears (Ursus arctos - Brown bear) from northern Canada, 1965-1967, including one bear from northwest British Columbia and two from southwest Yukon. (J30.47.w1)
  • Taenia krabbei were found in two bears during a survey of grizzly bears (Ursus arctos - Brown bear) from northern Canada, 1965-1967; one of the bears was from the Northwest Territories (J30.47.w1)
  • Taenia krabbei were found in 2.4% of 83 bears examined during a survey of Ursus americanus - American black bears in central Ontario, Canada, 1975-1977. (J30.56.w4)
  • Diphyllobothrium sp. were detected in 18% of 56 faecal samples from grizzly bears (Ursus arctos - Brown bear) collected from the central Canadian Arctic spring and summer 1995 and 1996. (J1.35.w7)
  • Taenia krabbei were detected in a single examined Ursus arctos - Brown bear in Siberia. (B208.7.w7)
  • Taenia ovis krabbei were detected in grizzly bears Ursus arctos - Brown bear in Montana. [1986](B208.7.w7, J381.53.w1)
  • Echinococcus granulosus was detected in 3.1% of 32 Ursus arctos - Brown bear in Romania. (B208.7.w7)
  • A study of 177 wild Ursus americanus - American black bear in spruce-fir forest noted that Taenia saginata were collected occasionally from scats of black bears in the Big Creek area. The source of infection was thought probably to be beat scraps eaten at the Ranger station and at trapsites. (D274)
  • Tapeworms have been found in Ursus maritimus - Polar bears fed salmon. (D315.3.w3)
Associated Techniques
Host taxa groups /species

Return to top of page