Feline Leprosy: Two Different Clinical Syndromes

Abstract

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 16S rRNA 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 6 microm (usually 2 to 4 microm). Mycobacterium lepraemurium was diagnosed in two cases based on the sequence of a 446 bp 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 8 microm (mostly 4 to 6 microm) which stained also with haematoxylin. A single unique sequence spanning a 557 bp fragment of the 16S rRNA 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. The same unique sequence was identified despite the use of different primers and PCR methodologies in the two laboratories. A very slow, pure growth of a mycobacteria species was observed on Lowenstein-Jensen medium (supplemented with iron) and semi-solid agar in one of three cases in which culture was attempted at a reference laboratory. Affected cats were domicile in rural or semi-rural environments. These infections could generally be cured using two or three of rifampicin (10-15 mg/kg once a day), clofazimine (25 to 50 mg once a day or...

Molecular Characterization of a Novel Fastidious Mycobacterium Causing Lepromatous Lesions of the Skin, Subcutis, Cornea, and Conjunctiva of Cats Living in Victoria, Australia

“…However, the indolent clinical course and multibacillary, lepromatous pathology are more typical of disease referable to the novel New South Wales and New Zealand Mycobacterium species (GenBank accession no. AJ294740 to AJ294746) (17), although lesions were not as numerous and cats of a wide age range were affected, in contrast to the older cohort of cats affected by the latter species.…”

“…Sequence analysis of these amplicons revealed that they were identical to each other (GenBank accession no. DQ873337) and to the sequence obtained from Nina (17). Database searches indicated that this sequence represents a novel mycobacterial species belonging to the M. simiae-related group, sharing an identical short helix 18, which is characteristic of this subgroup within the slow-growing mycobacteria (27) but distinct from the 16S rRNA gene sequence determined by Hughes et al (12) for the mycobacterium associated with CLGS (GenBank accession no.…”

“…From this case, a 2-year-old cat (named Nina) domiciled in rural Victoria, a further mycobacterial 16S rRNA sequence that did not match any database sequence was obtained (17). The lesions in this cat also were associated with numerous AFB (Table 1) (case 2 in reference 17).…”

“…AJ279017) (11), and another with a novel, fastidious, slow-growing mycobacterial species (GenBank accession no. AJ294740 to AJ294746) (13,17). The diseases caused by these mycobacterial species differed in a number of clinical and microscopic features.…”

Demographics and husbandry of pet cats living in Sydney, Australia: Results of cross-sectional survey of pet ownership

“…This intent was specifically to complement previous and ongoing investigations into renal disease ; infectious diseases caused by feline coronavirus (Norris et al 2005, Bell et al 2006 a and, feline leukaemia virus (Malik et al 1997), feline immunodeficiency virus (FIV) (Norris et al 1999, Gabor et al 2001, Norris et al 2007, Cryptococcus (O'Brien et al 2003), Nocardia and Mycobacterium (Malik et al 2002); as well as lymphosarcoma (Gabor et al 1998) and other cancers. In all of these studies, inferences concerning potential associations between disease, and age and/or gender, were based on reference populations of hospital patients, which were likely not representative of healthy normal cats.…”