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Description
Canine brucellosis is caused by the intracellular gram negative bacteria B. canis. The disease predominantly affects the reproductive system causing abortion and infertility in females and epididymitis and infertility in males. Other systems can also be affected, causing uveitis, discospondylitis, dermatitis and osteomyelitis. Transmission to humans has been documented but is very rare.
Animals are infected when the organism gains entry to the body at mucus membranes: vaginal, oral and conjunctival. Macrophages then phagocytose B. canis which targets lymphoid and genital tissue. A transient lymphoid hyperplasia and hyperglobinemia develop in the early stages of infection followed by a bactereamia 1-4 weeks post initial infection which can persist for up to 5 years. Brucellosis is transmitted by females at oestrus, breeding, post abortion, transplacentaly and is shed in urine, faeces and milk. Males shed the organism in semen for up to 2 years and in urine for up to 3 months. A cell mediated immune response is needed to clear the organism, however non-protective antibody may develop which complicates diagnosis and treatment of the disease.
Signalment
The prevalence of brucellosis is relatively low (1-8% in the U.S); areas affceted include the U.S, Japan, South America, Spain, Tunisia and Germany. The disease is more common in stray animals and breeding kennels. There is no breed susceptibility reported but beagles are over represented in cases in the U.S. The disease usually affects sexually mature animals and females more than males.
Diagnosis
Clinical Signs
Female:
- Abortion
- Postabortion vaginal discharge
- Early embryonic loss
The usual clinical presentation is of abortion in late gestation of an otherwise healthy bitch which is non pyrexic. Infertility, early embryonic loss and small litters are also reported; if a pregnancy continues to term the puppies die in the neonatal period.
Male:
- Scrotal enlargement
- Epididymitis
- Seminal abnormalities
- Testicular atrophy
- Infertility
Laboratory Tests
The organism can be cultured from aborted tissuen or vaginal discharge following abortion, these tissues contain high concentrations of B. canis, if these are not available then culture can be attempted on blood, urine or semen but is more difficult. Culture is difficult because B. canis is slow growing and contamination with other bacteria will result in faster growing bacteria over growing B. canis.
Early infection can be detected by haemoculture as a bacteremia is high from 4 weeks to 6 months after which it declines.
The organism can be identified using Slide agglutination, ELISA, agar gel immunodiffusion and PCR.
Treatment
- Neuter infected animals
Prognosis
References
- Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial
- Nelson, R.W. and Couto, C.G. (2009) Small Animal Internal Medicine (Fourth Edition) Mosby Elsevier
- Tilley, L.P. and Smith, F.W.K.(2004)The 5-minute Veterinary Consult (Third edition) Lippincott, Williams & Wilkins