Brucellosis (with notes on Bears and Lagomorphs)

Summary Information
Diseases / List of Bacterial Diseases / Disease description:

This disease page is currently predominantly used in Wildpro to link different data types and demonstrate inter-relationships. Whilst basic information is available, It does not contain detailed information.

Alternative Names Undulant fever (in humans)
Disease Agents
  • Brucella spp. bacteria. Small Gram-negative rods; non-motile, non-spore-forming and partially acid-fast (B21).
  • The species isolated from marine mammals in recent years have not yet been identified to species. (B209.22.w22)

In Lepus europaeus - Brown hare

  • Brucella suis is usually the species that is isolated from Lepus europaeus - Brown hare (B614.8.w8, J514.1.w1); however, Brucella abortus and Brucella melitensis have been recovered as well. (B614.8.w8)
  • Brucella suis biovar 2 is reported to largely occur in wild hares in continental Europe; it is of low virulence in humans. (B209.22.w22)
Infectious Agent(s)
Non-infectious Agent(s) --
Physical Agent(s) -- Indirect / Secondary
General Description

Brucellosis is an important infectious disease of mammals including humans. It primarily affects cattle, pigs, sheep, goats and dogs (B101, B209.22.w22). 

  • The information below has been collated due to the significance of brucellosis as a potential health hazard (zoonosis) to wildlife rescue workers dealing with marine mammals.

Clinical signs
In various mammal species
  • Usually involves the reproductive tract.
  • In females, characteristically causes abortion.
    • Abortion usually occurs mid-gestation or later.
    • Abortion usually occurs only on initial infection.
    • Birth of non-viable offspring may occur; apparently normal neonates (born infected, but with the infection being of only limited duration) may also be born.
  • In males, orchitis, epididymitis and infertility may result.

(B21, B101, B209.22.w22). 

In humans
  • Undulant fever: acute illness, prostration, weakness, with fever in the afternoon and evening, chills and night sweats with the fever subsiding until the next day.

  • After a few days symptoms may disappear, then reappear after a variable interval.

  • The acute form may reappear several times.

  • Debility, weakness, low-grade remittent fever, joint pains.

  • May also be sweating, lassitude and malaise, gastritis, abdominal pain, skin rashes, headache, irritability, depression, insomnia, arthritis, backache.

(B21, B47)

In Bears

Clinical signs
Gross Pathology
  • Seroprevalence for Brucella suis type 4 was studied in free-ranging grizzly bear (Ursus arctos horribilis) (Ursus arctos - Brown bear) populations of Alaska that are associated with the Arctic or Porcupine caribou (Rangifer tarandus - Reindeer) herds; seroprevalences for samples taken in 1971 were approximately 90% and 30% respectively for bears associated with the two herds. (J1.11.w10)

  • Antibodies to brucellosis (Brucella abortus) were detected by tube agglutination test in 18/332 sera (5%) from 265 Ursus americanus - American black bear from northcentral Idaho, 1971-1975. (J1.16.w12)
  • Antibodies to Brucella abortus were detected by rapid slide agglutination test in 1% of 283 sera from Ursus americanus - American black bear from Alberta, Canada, 1976. (J1.17.w11)
  • Antibodies to Brucella spp. were detected by the standard plate test and card test in sera from 6/122 (5%) grizzly bears (Ursus arctos - Brown bear) from southcentral Alaska, 1978-1981 (but from none of 28 Ursus americanus - American black bear) . (J1.19.w9)
  • A retrospective serological study in California from 1977 to 1989 showed a seroprevalence of 0.6% (one out of 180) for Brucella sp. in Ursus americanus - American black bear. (J1.28.w13)

  • A study conducted at Svalbard and the Barents Sea, late March to mid May, 1990-1999, revealed a seroprevalence of 5.4% for Brucella sp. from 297 Ursus maritimus - Polar bears sampled. No evidence of clinical disease was found. (J1.37.w7)

  • Antibodies to Brucella sp. were detected, using a buffered acidified card test and rapid automated presumptive test, in 5% of Ursus maritimus - Polar bear from the Beauford and Chukchi seas, from samples collected 1982-1999. (J3.156.w2)

  • A yearling Ursus americanus - American black bear infected intraperitoneally with 108 - 109 cfu (colony forming units) Brucella suis, and two 10-month old grizzly bears (Ursus arctos horribilis) (Ursus arctos - Brown bear) which were experimentally infected orally (1.3 x 109 cfu Brucella suis on canned dog food) with Brucella suis type 4, showing very high levels of antibodies titres within the first two months of infection. The animals were euthanased on day 83. The black bear, at necropsy, showed enlarged axillary lymph nodes and Brucella suis organisms were isolated from various lymph nodes as well as the spleen and urine. The Ursus arctos - Brown bears were not necropsied. (J1.17.w9)

  • Ursus americanus - American black bears have been experimentally infected with Brucella abortus strain RBN51 in order to asses the safety and efficacy of the oral vaccine. The vaccination did not appear to cause any clinical signs or affect the reproductive performance and was found to induce an ineffective immunologic response. (J1.40.w6)

  • Antibodies to Brucella spp. were detected by the buffered acidified card antigen test in 84/568 (15%) Ursus arctos - Brown bear and 1/76 (1.3%) Ursus americanus - American black bear in Alaska (samples collected1988-1991); only 1/40 samples from grizzly bears from inland Alaska (where all the black bears were from) were positive. (J64.17.w1)

In Lagomorphs

In Lepus europaeus - Brown hare:

  • Liver, spleen and reproductive organs: multifocal chronic granulomatous inflammation.

    • The lesions contain a central area of caseous necrosis that is surrounded by histiocytes and occasionally Langhans giant cells. (B614.8.w8)

  • Reproductive tract and associated lymph nodes: multiple necrotising pyogranulomas. (J514.1.w1)

Further Information Brucella spp. are isolated regularly from seals and cetaceans and serum samples from these animals are often Brucella positive. (D49)
  • Direct or indirect contact with infected animals excreting Brucella sp. organisms
  • Ingestion is a common route of infection.
  • Venereal transmission also occurs.
  • Infection in utero, by inhalation or via the conjunctiva occurs less commonly.
  • (B21)
  • In wild Lepus europaeus - Brown hares, mainly venereal but also orally, via the conjunctiva and percutaneously. (J514.1.w1)
Prevention of disease in humans
  • General hygiene; wear protective clothing and gloves when handling marine mammals.
  • Avoid contact with aerosols from marine mammals, e.g. respiratory discharges from the blow-holes of cetaceans.
  • (J15.20.w1, D14)
In Bears
  • The following have been used to confirm experimental infection:

    • Seroconversion (agglutination titres). (J1.17.w9)

    • Isolation from blood by haemoculture. (J1.17.w9)

    • Isolation of Brucella suis from spleen, urine, and mandibular, medial, retropharyngeal, paratoid, superficial cervical, axillary, mediastinal, mesenteric, external iliac and popliteal lymph nodes. (J1.17.w9)

Vaccination in bears
  • Ursus americanus - American black bears have been experimentally infected with Brucella abortus strain RBN51 in order to asses the safety and efficacy of the oral vaccine (intended for use in cattle and bison). The vaccination did not appear to cause any clinical signs nor to affect the reproductive performance. It did not induce an effective immunologic response: there was no significant increase in antibody titre in the bears following vaccination. it was possible to isolate the organism at necropsy from one of six bears in one study but none of six bears in a second study. (J1.40.w6)

Techniques linked to this disease
Host taxa groups /species 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). Bears (Ursidae - Bears (Family))


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

Disease Author Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referees Aidan Raftery MVB CertZooMed CBiol MIBiol MRCVS (V.w122)

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