Owner Information

Feline Tuberculosis

What are the signs of feline tuberculosis?

Any anatomical site may be involved, but typically cats with tuberculosis present with skin lumps or draining wounds, especially around the head and on the limbs. The lymph nodes draining these areas are also often enlarged.

Internal organ involvement has become less common, as less cats are now infected via the oral route, but may be manifested as abdominal lymph node enlargement and involvement of the intestines, spleen and/or liver. Cats with systemic disease often have inappetance/anorexia and weight loss. The infection may also spread to the lungs via the blood stream, causing breathing difficulties and/or cough.

How is feline tuberculosis treated?

Medical treatment is usually instituted with clarithromycin (or azithromycin), rifampicin, pradofloxacin (or moxifloxacin) for the first 2-3 months. Then consolidation treatment without rifampicin for at least another 4 months, depending on response to therapy.

Modifications to the treatment regimen may be made based on drug susceptibility data, response to therapy or the development of side effects necessitating drug cessation (e.g. hepatotoxicity). If drug resistance develops, treatment may include ethambutol, dihydrostreptomycin, isoniazid or pyrazinamide, however these drugs are typically more toxic than the ‘first-line’ agents mentioned above. M. bovis is resistant to pyrazinamide.

Surgical excision of skin nodules may be helpful if practicable.

Further information about feline TB can be found at www.icatcare.org/advice/cat-health/mycobacterial-diseases-cats-tuberculosis

Environmental Mycobacterial infections

How do cats with environmental mycobacterial typically present?

The disease syndromes in cats caused by the environmental mycobacterial are different depending on whether the causative species is in the ‘rapidly growing’ group (those that grow in the laboratory within 3-7 days) or in the ‘slowly growing’ group (those species that take longer than 7 days to grow).

‘Rapidly growing’ species tend to cause diffuse infection of the skin and subcutaneous tissue of the belly and side of the cat, particularly in overweight individuals. These lesions have a distinctive appearance, as demonstrated in the images below. Rarely, cases of pneumonia have occurred after suspected inhalation. The skin infections do not usually spread internally.

Click on the images below to view cats with ‘rapidly growing’ mycobacteriosis.

Any anatomical site may be involved with infections caused by the ‘slowly growing’ species (usually M. avium) but mostly these organisms cause internal disease, particularly involving the abdominal lymph nodes intestines, spleen and/or liver.  Lung involvement with or without accompanying clinical signs is common with M. avium infections. Skin lumps or draining wounds can be caused by these mycobacterial species, but this is a less common presentation.

Click on the images below to view cats with ‘slowly growing’ mycobacteriosis.

How are these infections treated?

Medical treatment of the ‘rapidly growing’ organisms is instituted with two of the following drugs: ideally pradofloxacin (or moxifloxacin) or a second generation fluoroquinolone (marbofloxacin or orbifloxacin) depending on availability and/or owner finances, plus doxycycline if in Australia or clarithromycin if in USA. Modifications to the treatment regimen are then made depending on drug susceptibility data and/or response to therapy. Wide surgical excision of granulomatous tissue is recommended if lesions are no longer reducing in size with medical therapy.

Treatment of the ‘slowly growing’ organisms is instituted with clarithromycin (or azithromycin) and one or two of the following: rifampin, pradofloxacin (or moxifloxacin)or clofazimine, depending on availability and/or owner finances. Modifications to the drug regimen are then made depending on species ID, susceptibility data, response to therapy, or the development of side effects, which may require drug cessation (e.g. hepatotoxicity). Surgical excision of cutaneous nodules is advised if practicable. Typically medical treatment is required for 4-6 months in the case of localized skin infection, and usually 6-12 months for internal infections. It is recommended that treatment be continued for 2 months past resolution of all clinical signs or evidence of disease on x-rays or ultrasound.

Feline Leprosy infections

How do cats with feline leprosy typically present?

Most cats with feline leprosy have one or more skin lumps. These may be intact or ulcerated and are usually not painful unless they have become secondarily infected. Some cats may also have lesions on the cornea or involving the conjunctiva of the eye.

Click on the images below to view cats with feline leprosy.

 

How is it treated?

Definitive treatment guidelines for each of the organisms that cause feline leprosy are yet to be established, because their antibiotic susceptibility is mostly unknown.  Recent work on M. lepraemurium suggests that the organism is highly susceptible to rifampicin and clofazimine.

A combination of two to three of the following drugs; rifampicin, clofazamine, clarithromycin, or pradofloxacin/moxifloxacin, ideally with surgical resection of skin lesions, appears to be the most effctive treatment.

Subjectively, some cases of feline leprosy caused by one of the novel organisms appear to respond favorably to a second-generation fluoroquinolone such as marbofloxacin or orbifloxacin.

It is recommended that medical therapy be continued for 2 months past resolution of clinical signs (in most cases 4-6 months or more of therapy is required).

Even if all visible skin lesions have been removed surgically, it is recommended that medical therapy be instituted for 2 months, as recurrence at the same or distant anatomical sites is relatively common.

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