Mycobacterial protocol for cats

In the UK, the majority of mycobacterial infections in cats are caused by tuberculous mycobacteria. The initial large culture study showed ~35% of infections to be caused by (~20%) or (~15%) (Gunn-Moore , 2011ab), with ~50% of cases failing to grow. However, further, as yet unpublished work using the more sensitive polymerase chain reaction (PCR) approach found a similar proportion of cases caused by , but a higher proportion caused by (~35%) (Gunn-Moore and O’Halloran, unpublished data). The most common non-tuberculous mycobacteria (NTM) are in the complex (MAC), and a wide range of NTM can infect cats.

It is important to consider the factors below before undertaking treatment:

  • – the disease may be caused by a member of the tuberculosis (TB) complex. All members of the affected cat's household must be considered. It is important to determine any potentially immunosuppressed individuals (e.g. people with human immunodeficiency virus or who are undergoing chemotherapy). Treatment is not advised where such individuals may be exposed. Treatment is also not advised if the affected cat has generalized disease, cavitating lesions within the respiratory tract or extensive draining cutaneous lesions as these may increase the risk of transmission
  • – this can be difficult to maintain given patient non-compliance, the inherent toxicity of some of the drugs and the financial costs involved. In some cases, the drugs may at best suppress disease and indefinite treatment may be required (Sieber-Ruckstuhl , 2007; Greene and Gunn-Moore, 2011). Uncomplicated cutaneous cases with or without diffuse pulmonary changes carry the most favourable prognosis. Placement of a feeding tube may be required to improve compliance
  • – pending a definitive diagnosis, interim therapy with a fluoroquinolone is recommended in cases of localized cutaneous infection (Gunn-Moore , 2010). Pradofloxacin (or moxifloxacin) is recommended as it is more effective against mycobacteria than the older fluoroquinolones, such as marbofloxacin (Govendir , 2011). With more extensive disease, double or triple therapy is advised (Greene and Gunn-Moore, 2011); i.e., start with pradofloxacin and azithromycin, pending confirmation, then add rifampin when TB is confirmed.

Previously, anti-tuberculosis treatment was given in an initial and then a continuation phase (Greene and Gunn-Moore, 2011); however, it is now known that it is better to give all three drugs for 4–6 months, depending on the extent of disease, and always for at least 2 months following complete resolution of the lesions. In those cats where triple therapy is not feasible, treatment should still involve two drugs and should be given for a minimum of 6–9 months. Extensive clinical experience supports using rifampin, pradofloxacin and azithromycin as a starting point; however, NTM infections may need different combinations. 

Drug Uses Dose (mg/kg) Effects of toxicity
Pradofloxacin First-line treatment for TB, NTM  3–5 p.o. q24h Reversible neutropenia, seizures in cats with CNS disease
Rifampin First-line treatment for TB, MAC, NTM 10–15 p.o. q24h

Side effects in ~40% of cases, with severe side effects in ~5%. Poor palatability, nausea, discoloration of body fluids, generalized erythema and pruritus, hyperaesthesia, CNS signs, hepatotoxicity, anaphylaxis




First-line treatment for TB, MAC, FLS,  NTM

7–15 p.o. q12h

5–15 p.o. q24h

Possible pinnal or generalized erythema, hepatotoxicity, possible GI signs


Second-line line treatment for TB

Prophylaxis for TB

10–20 p.o. q24h

10 p.o. q24h

Hepatotoxicity, peripheral neuritis, seizures, acute renal failure
Ethambutol Second-line treatment for TB 10–25 p.o. q24h Optic neuritis
Pyrazinamide Second-line treatment for TB 15–40 p.o. q24h Hepatotoxicity, GI signs
Dihydrostreptomycin Second-line treatment for TB 15 i.m. q24h Ototoxicity
Clofazimine Treatment for FLS, NTM

4–8 p.o. q24–48h

Max. 25 total

Hepatotoxicity, GI signs, discoloration of body fluids, photosensitization, pitting corneal lesions




Second-line treatment for NTM, MAC

5–10 p.o. q12–24h

10–15 i.v., i.m., s.c. q24h

20–30 i.v., i.m., s.c. q6–8h

GI signs, oesophagitis

Nephrotoxic, ototoxic

Pain on i.m., s.c. injection

Potentially useful drugs for the treatment of feline mycobacterial disease. Second-line treatments for tuberculosis should be reserved for resistant infections. Ensure all aspects of cascade prescribing have been considered before using drugs only authorized for human use. Data from Kaufman , 1995; Gelatt , 2001; Bennett, 2007; Sieber-Ruckstuhl , 2007. FLS = feline leprosy syndrome; MAC =-intracellulare complex; NTM = non-tuberculous mycobacteria; TB = tuberculosis.The authors do not recommend enrofloxacin as it has been associated with retinal degeneration; other than the newer fluoroquinolones (pradofloxacin and moxifloxacin), most others are not effective against MAC infections. These drugs may cause potentially serious side effects (e.g. hepatotoxicity or nephrotoxicity); it is advisable to monitor use closely, including routine haematology and serum biochemistry 2 weeks after starting treatment and again following any change in the cat’s demeanour. and some NTM, potentially including MAC infections, can have inducible resistance genes to macrolides, meaning they appear susceptible but are resistant ; where possible (limited by GI signs), use higher doses to reduce the risk of resistance. Particularly useful when treating MAC infections. Not effective against infection. Can be difficult to obtain. Give with food or give water after the medication to avoid oesophageal injury.

At a minimum, use of a fluoroquinolone is suggested while waiting for PCR or culture results. The new fluoroquinolones (e.g. pradofloxacin or moxifloxacin) are recommended as they have an extended spectrum of activity, which includes some NTM, and they are even effective against MAC infections (Govendir , 2011). 

MAC infections are particularly difficult to treat (Jordan , 1994). Clarithromycin should be included (Piersimoni , 1995), ideally in combination with rifampin (Tomioka , 2002) ± another antibiotic according to culture and susceptibility testing, such as doxycycline (Baral , 2006) or, from human studies, ethambutol (Esteban , 2012).

Pyogranulomatous panniculitis requires long-term antibiotics and radical well planned surgery: e.g., doxycycline for several weeks, then radical surgical excision and local reconstruction plus parenteral gentamicin perioperatively for 3–5 days, followed by a prolonged course (3–6 months) of a new fluoroquinolone (White , 1983; Malik , 1994, 2000, 2004). Non-surgical cases may require double or triple therapy.

Feline leprosy-type infections (feline leprosy syndrome; FLS) can usually be treated with surgical removal of small nodules, which may be curative. Where medical management is needed, clarithromycin, pradofloxacin and rifampin or clofazimine are recommended. Doxycycline, fluoroquinolones and aminoglycosides may also be useful (Mundell 1988; Malik , 2002, 2006a; Courtin , 2007; Malik , 2013). Dapsone is considered too toxic for use in cats (Hamanda , 1991) and is antagonistic to clofazimine. Treatment should be continued until the lesions have completely resolved, and ideally for a further 2–3 months to reduce the risk of recurrence; however, some cases require life-long clarithromycin to prevent recurrence (Malik , 2013).

Mycobacterial species Susceptibility Generally resistant

Clarithromycin, rifampin, doxycycline, ethambutol, pradofloxacin, clofazimine, amikacin

clarithromycin or azithromycin + rifampin + another drug

Older fluoroquinolones, cefovecin

Potentially inadvisable to give just a new fluoroquinolone + clarithromycin or azithromycin

pradofloxacin + amikacin (100%), cefoxitin (94%), older fluoroquinolones (75%), clarithromycin (~75%), clofazimine, rifampin, gentamicin or doxycycline (29%)

Trimethoprim ± sulphonamide, cefovecin, clarithromycin

Fluoroquinolones, tetracyclines, gentamicin, trimethoprim ± sulphonamide, clofazimine

pradofloxacin + doxycycline

Clarithromycin, cefovecin

Amikacin (100%), cefoxitin (94%), ciprofloxacin (75%), clarithromycin (71% a), pradofloxacin, clofazimine

azithromycin or clarithromycin + another drug

Many oral medications, including doxycycline + older fluoroquinolones

Do not give pradofloxacin or moxifloxacin with azithromycin or clarithromycin

Fluoroquinolones, clarithromycin, rifampin, clofazimine  
Rifampin, clarithromycin, fluoroquinolones, amikacin, clofazimine  
Rifampin, doxycycline, clarithromycin  
Clarithromycin, azithromycin, ethambutol  
Clarithromycin, fluoroquinolones, ethambutol  

Susceptibility and resistance of mycobacterial species to potential drugs for the treatment of NTM in cats. Data from Studdert and Hughes, 1992; Malik , 1994, 2000, 2004, 2006ab; Michaud, 1994; Kiehn , 1996; Foster , 1999; Smith , 2000; Jang and Hirsh, 2002; Tomioka , 2002; Dietrich , 2003; Govendir , 2011; Cho , 2012; van Ingen , 2012; Bennie , 2014.Other studies have shown these drugs to be either more or less effective.

Cats may suffer side effects while receiving treatment for mycobacterial infections, especially with rifampin. While side effects can be concerning to owners and veterinary professionals, this drug is essential for optimizing the outcome of treating cats with TB and is the only drug in the triple therapy approach with activity against non-replicating bacteria.

To help manage dermatological side effects such as pruritus, oedema and erythema, chlorphenamine is advised (2–4 mg/cat p.o. q8–12h). Focal pruritic lesions can also be managed with topical hydrocortisone aceponate spray.

Hepatotoxicity is another possible side effect of rifampin, which may manifest clinically as hyporexia, nausea or vomiting, or may be identified with increased enzymes on serum biochemistry.-Adenosylmethionine (SAMe) (20 mg/kg p.o. q24h) is one hepatoprotectant agent that is widely used in cases of drug-induced liver toxicity, as well as in cases of liver disease.

An intriguing alternative agent is -acetylcysteine (NAC) (600 mg/cat p.o. q12h); while pharmacological data are lacking for its use in cats, it is safe and well tolerated. NAC has an unpleasant taste and smell, so giving whole capsules is usually advised. Nausea and vomiting are potential side effects, and drooling occurs when the capsule content is mixed with too little food. Since NAC can cause bronchial spasm, it should be used with caution in animals with asthma. NAC helps to restore blood glutathione concentrations and thus antioxidant capacity. It has also been shown to reduce bacterial counts and the severity of lesions. Restoration of antioxidant capacity helps reduce the toxic side effects of anti-TB drugs such as rifampin and isoniazid, which are mediated by oxidant-driven damage to the liver. Short-term studies have also shown that NAC has some direct anti-mycobacterial activity and can reduce growth of bacteria both and .

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