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Pulmonary tuberculosis
Synonym(s): Pulmonary TB, active tuberculosis/TB
Introduction
- Rare primary disease in dogs.
- Dogs primarily develop respiratory form of disease.
- Cause: infection with Mycobacterium tuberculosis. Mycobacterium bovis may also occasionally be isolated.
- Signs: weight loss, cough, depression, lymphadenopathy (local or generalized), anorexia. Occasionally dyspnea.
- Diagnosis: biopsy with histology and special stains, culture/PCR and diagnostic imaging.
- Treatment:
- Euthanasia. Always indicated for M. tuberculosis infections due to risk to public health.
- Long-term and potentially toxic chemotherapy can be used for TB complex infections other than M. tuberculosis. Often not attempted.
- Prognosis: guarded or poor.
Presenting signs
- May be no clinical signs for long periods after infection.
- Weight loss.
- Depression.
- Anorexia.
- Cough.
- Dyspnea.
- Abdominal distension.
Geographic incidence
- Present in all parts of Europe, Africa and USA but variations in incidence.
Age predisposition
- Mainly young animals.
Breed/Species predisposition
- No reported breed predisposition.
Public health considerations
- Infected dogs produce organism in sputum.
- Zoonotic transmission, and reverse zoonotic transmission have both been documented in the UK and USA.
- If a diagnosis is made of active tuberculosis in a dog, human health professionals should be informed.
Cost considerations
- Long-term therapy (6-9 months) with chemotherapy and appropriate monitoring is very expensive.
Special risks
- Risk of transmission to humans.
- Most canine cases are probably acquired from human carrier.
If canine case is identified screen all in-contact humans for presence of carrier.
Pathogenesis
Etiology
- Infection with Mycobacterium tuberculosis Mycobacterium tuberculosis or another member of the mycobacterium tuberculosis-complex, usually M. bovis.
Predisposing factors
General
- Contact with human case. Also (but more rarely) contact with other sources, eg cattle or wildlife.
- Immunocompromise, although evidence for this in dogs is anecdotal.
Pathophysiology
- Dogs are usually infected with mycobacteria via inhalation of infective agent and so tend to develop respiratory disease.
- Wildlife infections can occur by inoculation into the skin via bite wounds and so result in skin granulomas.
- Most canine cases are the result of contact with human carriers or, occasionally, other sources.
- Organism multiplies locally inducing granuloma (or tubercle) formation.
- Infection will be spread to local lymph nodes.
- Immune system activation at this stage may result in a degree of regression of lesions.
- Lesions may progress over time to have a degree of central cavitation with cessation.
- If cell mediated immune response fails or wanes, infection may spread or generalize.
Timecourse
- Chronic disease with insidious onset over months.
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.
- Aranaz A, Liébana E, Pickering X, Novoa C, Mateos A & Domínguez L (1996) Use of polymerase chain reaction in the diagnosis of tuberculosis in cats and dogs. Vet Rec 138 (12), 276-280 PubMed.
- Clercx C et al (1992) Tuberculosis in dogs - a case report and review of the literature. JAAHA 28 (3), 207-211 VetMedResource.
- Trujillo-Rojas R A (1967) Pulmonary tuberculosis in dog diagnosed by a positive culture of Mycobacterium tuberculosis from laryngeal swab. Am Rev Respir Dis 95 (4), 674-675 PubMed.
Organisation(s)
- Clinical advice: Professor Danielle Gunn-Moore, Royal (Dick) School of VeterinaryStudies, University of Edinburgh, UK. Email: companion.animalTB@ed.ac.uk.
- Regional Center for Mycobacteriology (PHLS), Llandough Hospital, Penlan Road, Renarth, Cardiff CF64 2XX, UK. Tel: +44 (0)2920 716408.
- Mycobacteria Unit, City Hospital, Edinburgh EH10 5SB, UK.
- Mycobacteria Unit, St James Hospital, St James Street, Dublin 8, Ireland.