Feline leprosy: two different clinical syndromes

• Published in: Journal of feline medicine and surgery 2002-03, Vol.4 (1), p.43-59
• Main Authors: Malik, R, Hughes, MS, James, G, Martin, P, Wigney, DI, Canfield, PJ, Chen, S CA, Mitchell, DH, Love, DN
• Format: Article
• Language: English
• Subjects: Animals; Case Report; Cat Diseases - drug therapy; Cat Diseases - pathology; Cats; Clarithromycin - therapeutic use; Clofazimine - therapeutic use; Female; Leprostatic Agents - therapeutic use; Leprosy, Lepromatous - pathology; Leprosy, Lepromatous - veterinary; Male; Mycobacterium - classification; Mycobacterium - genetics; Mycobacterium - isolation & purification; Polymerase Chain Reaction - veterinary; Rifampin - therapeutic use; RNA, Ribosomal, 16S - genetics
• ISSN: 1098-612X; 1532-2750
• DOI: 10.1053/jfms.2001.0151

Feline leprosy refers to a condition in which cats develop granulomas of the subcutis and skin in association with intracellular acid-fast bacilli that do not grow on routine laboratory media. In this study, the definition was extended to include cases not cultured, but in which the polymerase chain reaction (PCR) identified amplicons characteristic of mycobacteria. Tissue specimens from 13 such cases from eastern Australia were obtained between 1988 and 2000. This cohort of cats could be divided into two groups on the basis of the patients' age, histology of lesions, clinical course and the sequence of 16SrRNA PCR amplicons. One group consisted of four young cats (less than 4 years) which initially developed localised nodular disease affecting the limbs. Lesions progressed rapidly and sometimes ulcerated. Sparse to moderate numbers of acid-fast bacilli were identified using cytology and/or histology, typically in areas of caseous necrosis and surrounded by pyogranulomatous inflammation. Organisms did not stain with haematoxylin and ranged from 2 to 6μm (usually 2 to 4μm).Mycobacterium lepraemurium was diagnosed in two cases based on the sequence of a 446bp fragment encompassing the V2 and V3 hypervariable regions of the 16S rRNA gene a different sequence was obtained from one additional case, while no PCR product could be obtained from the remaining case. The clinical course was considered aggressive, with a tendency towards local spread, recurrence following surgery and development of widespread lesions over several weeks. The cats resided in suburban or rural environments. A second group consisted of nine old cats (greater than 9 years) with generalised skin involvement, multibacillary histology and a slowly progressive clinical course. Seven cats initially had localised disease which subsequently became widespread, while two cats allegedly had generalised disease from the outset. Disease progression was protracted (compared to the first group of cats), typically taking months to years, and skin nodules did not ulcerate. Microscopically, lesions consisted of sheets of epithelioid cells containing large to enormous numbers of acid-fast bacilli 2 to 8μm (mostly 4 to 6μm) which stained also with haematoxylin. A single unique sequence spanning a 557bp fragment of the 16SrRNA gene was identified in six of seven cases in which it was attempted. Formalin-fixed paraffin-embedded material was utilised by one laboratory, while fresh tissue was used in another. Th