66 (126)

6: Bacterial dermatoses

antibiotics have been used in the treatment of atypical mycobacterial infections: kanamycin, gentamicin, amikacin, tetracyclines, potentiated sulphonamides and enrofloxacin³. In our experience, orał doxycycline (5 mg/kg SID for 6-8 weeks), selected from antibiotic sensitivity testing, is the antibiotic treatment of choice. This can be followed by broad surgical excision and cutaneous reconstruction techniąues^l8. From the time of surgical excision, intravenous injections of gentamicin (4 mg/kg) should be given every 8 hours for 3-4 days. Orał enrofloxacin (5-20 mg/kg SID) can then be given for 2-4 months (Table 6:1).

Feline leprosy

Aetiopathogenesis

Feline leprosy is a rare and mainly cutaneous infection, probably caused by Mycobacterium lepraemurium, the agent of leprosy in rats ^I9. Penetration of naturally infected tissue causes skin lesions within 2-5 months. The condition may also be transmitted by rat bites, and possibly by mosąuitoes, fleas and ticks ³. Feline leprosy is a ubiąuitous condition reported in the United States, Canada and Australia as well as in Great Britain, the Netherlands and France. No breed or sex predilection has been seen. However, feline leprosy is reported mainly in cats aged between 1 and 3 years³.

Clinical features

Dermatological signs are characterised by single or multiple, ulcerated or non-ulcerated alopecic nodules, seen mainly on the face, limbs and sometimes the trunk (Figs 6 : 9,10). Ulcers and draining tracts may be seen ^l9,2°.

Systemie signs are rare. Regional lymphadenopathy is seen in some cases. Systemie involvement is extremely rare in the cat³.

Diagnosis

The diagnosis is based mainly on lesion distribution and suggestive skin biopsies.

Histopathological examination of deep skin biopsies usually reveals a “lepromatous” reaction, characterised by a granulomatous dermatitis, rich in macrophages and giant cells (Fig. 6 : 11) and numerous intracelluląr well-stained bacilli, arranged in strips (Fig. 6 : 12). Much morę rarely, a “tuberculoid” reaction is seen, characterised by the presence of epithelioid granulomas, surrounded by lymphocytes, with only a few bacteria in the centre ^l9-²¹.

Bacterial culture is difficult and often negative on standard mycobacterial culture media. In vitro growth is very slow (about 3 months). Special media (e.g. Ogawa egg yolk medium and a medium enriched in cytochrome C and alpha-ketogluratate) can be used³.

Molecular biological techniques (e.g. amplification) can now be used to identify mycobacteria. Treatment

Surgical excision is probably the treatment of choice for single nodules although post-surgical recurrence may be seen.

Orał clofazimine (2-8 mg/kg SID) gives good results²¹. It comes as a capsule which may need to be punctured to allow correct dosage. Gloves should be wom when handling the capsules due to the red colouration of the antibiotic. Treatment may stain the skin and mucous membranes orangy-red. Following use of this product, a moderate inerease in the level of hepatic enzymes has been reported in the cat.

Other combination therapies involving dapsone (1 mg/kg SID), clofazimine and rifampicin (10-20 mg/kg BID), given orally, are sometimes necessary in cases refractory to standard treatment²¹ (Table 6:1).

6.7