Anim. Pract. (1975) 16, 563-567.
Skin granuloma of cats associated with acid-fast bacilli M. R O B I N S O N Department of Veterinary Pathology, The University, Liverpool
ABSTRACT Six cases of cats with skin granulomata containing large numbers of acidfast organisms are reported and described. Two cats were destroyed and examined post-mortem, and three cats were treated surgically and with antibiotic therapy and there was no recurrence in 7 months. Follow-up information was not available on the sixth case. INTRODUCTION There have been several reports of non-tuberculous acid-fast granulomatous skin lesions in cats during the past 15 years from New Zealand, Australia, Great Britain and Canada (Brown et al., 1962; Lawrence& Wickham, 1963; Wilkinson, 1964; Schiefer et al., 1974). Attempts to grow organisms in vitro from the lesions have so far failed and there is only one report of successful transmission to laboratory animals (Lawrence & Wickham, 1963). During the past 3 years the author has encountered several cases of a disease closely resembling the previously reported condition and because of the paucity of reports of the disease in this country the clinical and pathological findings of six cases are recorded here. MATERIALS AND METHODS. Of the six cases, post-mortem examinations were performed on two and material was removed surgically and examined pathologically from four cases. Tissue blocks for histological examination were fixed in 4% buffered formaldehyde solution and embedded in paraffin wax, and sections were cut at 4 pm. They 563
M. R O B I N S O N
were stained with haematoxylin and eosin and selected material was stained by the Ziehl-Neelsen method. Material from the skin lesions of two cats was ground to a paste with sterile sand and sterile normal saline. Each specimen was divided into two aliquots. T o one an equal volume of 6% oxalic acid solution was added and left for 2 hours at room temperature and normal saline was added to the other. After decanting to remove the sand the tissue was centrifuged at 3,000 rpm for 15 min and the deposit re-suspended in saline to remove the oxalic acid. Many acid-fast organisms were present in both suspensions. Material from both suspensions was inoculated on to the following media in duplicate : Lowenstein-Jensen slopes, Stonebrinks (pyruvate medium) slopes, Dorset egg slopes, glycerol agar slopes, Dubos solid medium slopes, Dubos fluid medium and blood agar and nutrient agar plates. One set of cultures was incubated at 37°C and the other set at room temperature. All cultures were left for 14 weeks with regular inspection for growth. Subcutaneous inoculations of material from both suspensions were made into two young adult mice, a young adult rat, a young adult guinea pig and a 3-monthold kitten. These animals were allowed to survive for 4 months and were then destroyed and post-mortem examinations performed. RESULTS
Clinical jindings All our cases were presented as cats in reasonably good health with skin lesions. In some cats the lesions were thickened subcutaneous areas up to 1 cm in diameter with a cutaneous discharge of purulent material. I n others the lesions were pale tumour-like nodules protruding from the skin and showing loss of skin over their surface (Fig. 1). The site of the lesions varied and involved the head, neck, hind and forelimbs or the flank. I n three animals the lesions were multiple and in three single lesions were observed. T h e precise length of time the lesions had been in existence was not known in all cases. I n one cat the lesion had been present for 3 weeks, in another for several months. I n the case where the lesion had been in existence the longest, the lesion was the largest and measured 3 x 3 x 2 cm. The age of affected cats varied from 14 months to 5 years. Two were females and four were males. I n three cases which were treated surgically with subsequent antibiotic therapy there was no recurrence of the lesions after 7, 10 and 10 months respectively. No information is available on the fourth case. Pathology I n one animal which came to post-mortem, the only significant lesions were in the skin and drainage lymph nodes. Affected lymph nodes were slightly enlarged, pale and oedematous. T h e second animal showed in addition lesions of chronic nephritis. Histopathological examination of skin lesions from all the cases showed a
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similar picture. The nodules and subcutaneous thickened areas were granulomatous in appearance and were composed of a diffuse mixture of fibroblasts, polymorphonuclear leucocytes, lymphocytes, macrophages, epithelioid cells, and an occasional Langhans-type giant cell (Fig. 2). Caseation and calcification were not features of any of the lesions. Sections stained by the Ziehl-Neelsen method showed many of the epithelioid cells to be packed with acid-fast rods (Fig. 3). The organisms were mainly intracellular. Enlarged lymph nodes showed marked lymphoid hyperplasia. I n only one case were acid-fast organisms seen in the lymph node. These were in small numbers within macrophages in the sinusoids. Little cellular reaction was associated with these organisms in lymph nodes.
FIG. 1. Cat showing head lesion.
Cultures The media inoculated with the untreated suspension showed contamination with Gram negative organisms at 48 hours. No acid-fast organisms were observed in the media inoculated with the treated or untreated suspensions during the 14-week period.
Animal Inoculation Post-mortem and histological examination of all the experimental animals
FIG.2. Section of skin nodule showing Langhans-type giant cell. H. & E.
FIG.3. Section of skin nodule showing large numbers of acid-fast bacilli. ZN x 188.
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did not show any significant lesions at the end of 4 months and no acid-fast organisms were recovered from inoculation sites.
DISCUSSION The clinical and pathological findings reported here closely resemble previous cases from Great Britain and elsewhere (Brown et al., 1962; Lawrence & Wickham, 1963; Wilkinson, 1964; Scheifer et al., 1974). The failure to grow the causal organism in uitro agrees with other workers and the failure to transmit the disease agrees with other workers except for Lawrence & Wickham (1963), who successfully transmitted the disease to rats and guinea pigs. Passage back to cats from rats was not highly successful although mild lesions were observed in one animal. Their cats were 3 days old at the time of inoculation whereas our cat was 3 months old. The age of affected animals in our cases suggests that infection can occur after the neonatal period. The route of infection is unknown although it seems likely to be via the skin. Five of our cases were referred to us from the same veterinary practice but the animals were from different owners living in different parts of Merseyside. Apart from the finding of an occassional Langhans-type giant cell and the presence of acid-fast organisms the lesions are fairly non-specific and unless critically examined the diagnosis may easily be missed. These factors suggest the disease may be more common than is indicated by the literature. Our findings in the three follow-up cases indicate that the disease can be treated by surgery and antibiotic therapy and destruction of affected animals is not necessary. At the present time there is no evidence that animals should be destroyed on public health grounds. From our study the relationship between this disease and murine leprosy is, if any, unclear. More transmission experiments and serological work are required to elucidate any possible relationship. ACKNOWLEDGMENTS
The author would like to thank Professor D. L. Hughes for help, advice and criticism of the manuscript, Messrs R. Weinberg and D. R. Highet for providing the case material, Mr K. Bell and Mrs M. W. Harling for technical assistance and Mrs P. Jenkins for the photography. REFERENCES BROWN,L.R., MAY, C.D. & WILLIAMS, S.E. (1962) N.5. vet. 3. 10, 7-9. LAWRENCE, W.E. & WICKHAM, N. (1963) Aust. uet. 3. 39, 390-393. SCHIEFER, B., GEE,B.R. & WARD,G.E. (1974) 3. Am. Vet. Med. Ass. 165, 1085-1087. WILKINSON, J.T. (1964) Vet. Rec. 76, 777-778.