bovis - Articles
Skin tuberculosis
Synonym(s): tuberculosis, atypical, mycobacteria, acid-fast
Introduction
- Cause: atypical mycobacteria, occasionally M. bovis.
- Signs: papules and nodules on the distal limbs.
- Diagnosis: acid fast bacteria seen in stained smear preparations of pus and in dermal macrophages.
- Treatment: usually not undertaken.
- Prognosis: tend not to heal but little effect on animal.
Presenting signs
- Lesions usually take the form of nodules in subcutaneous tissues, but they may involve the skin and are occasionally confined to the skin.
- Skin tuberculosis lesions are usually confined to the lower limbs.
Acute presentation
- Mycobacteriosis due to atypical mycobacteria including M. fortuitum and M. kansasii may produce infection in the lymph nodes of calves.
- Usually no superficial lesions but could result in enlarged lymph nodes.
Geographic incidence
- Worldwide.
Public health considerations
- Some of these bacteria can infect man.
- Difficulties in interpretation of the comparative intradermal tuberculin test. M. bovis Mycobacterium bovis not thought to be a cause but presence of atypical mycobacteria may sensitize animals to tuberculin.
- Animals infected with skin tuberculosis react to the intradermal tuberculin test, but not so markedly as those infected with true bovine tuberculosis.
Special risks
M. bovis and some atypical mycobacteria are zoonotic.Pathogenesis
Etiology
- Likely skin contamination of wounds is the entry site for acid fast organisms.
- Atypical mycobacteria are ubiquitous environmental saprophytes.
Predisposing factors
General
- Poor housing.
- Rough pasture.
Pathophysiology
- Acid-fast bacteria stimulate the body's production of nodules as a walling-off mechanism.
- Nodules result from massive infiltration of inflammatory cells into the dermis and subcutis often neutrophilic in character possibly with histiocytes and giant cells and contain thick creamy to grey pus.
- Lymph vessels may be thickened.
Epidemiology
- M. fortuitum.
- M. kansasii.
- M. bovis Mycobacterium bovis.
- Majority of cases defy attempts to isolate and identify causal organism although they are gram positive and acid-fast.
- Modern bacterial culture techniques usually identify the casual organism although in practice this is not often done, they are gram positive and acid-fast.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed Papers
- Recent references from PubMed and VetMedResource.
Other sources of information
- Andrews A H (1997) Lecture notes from Royal Veterinary College for Skin Diseases of Farm Animals.
- Blowey R W & Weaver A D (1991) Colour atlas of diseases and disorders of cattle. Wolfe.
- Scott D W (1988) Large Animal Dermatology. W B Saunders.