Cutaneous Mycobacteriosis in a Cat

Abstract

Background: Feline cutaneous mycobacteriosis is a dermatopathy caused by Mycobacterium spp., presenting different forms of manifestation according to the species involved. The so-called feline leprosy, caused by M. lepraemurium, is characterized by cutaneous and subcutaneous granulomas transmitted mainly by the bite of rodents. Diagnosis and treatment are challenging due to the specificities of the species. This study aimed to document a case of feline leprosy in Santa Catarina since there are no reports to date in the state. It also emphasized the theme’s relevance as a significant differential diagnosis in dermatological disorders.
Case: A female cat, without a defined breed, castrated, and at 4 years of age, with lesions at the base of the tail that persisted for over 1 month, even after an old treatment instituted with dexamethasone and local care, was attended at the Veterinary Clinic School of Santa Catarina Federal University (CVE/UFSC). On general physical examination, we verified an increase in the right popliteal lymph node, and, on specific examination, 3 lesions were observed at the base of the tail, with an increase in volume, purulent, and measuring about 2 to 3 cm in diameter. Mycobacteriosis was suspected after unsuccessful treatment with cephalexin for 7 days. A biopsy of 3 fragments of the lesions was performed with punch histopathological examination, revealing alcohol-acid resistant bacilli suggestive of M. lepraemurium. The material was sent for real-time PCR (qPCR) for mycobacteria of the complex Mycobacterium tuberculosis (Mtb) and non-tuberculous mycobacteria (NTMs), with amplification for NTMs, which allowed the definitive diagnosis of cutaneous mycobacteriosis in the feline patient. A new treatment was started with Doxycycline for 30 days. The animal returned 30 days after the end of the treatment, presenting total regression of the lesions and complete repilation, which was considered a clinical cure.
Discussion: Within the variety of presentation of the disease caused by M. lepraeumurium, the patient presented lesions similar to those of the tuberculous form. Although literature data report a prevalence of the location of lesions in limbs and the head, we assumed that their presence in the base region of the tail is linked to where the rodent had access to bite the animal. Diagnosing leprosy is difficult due to the demanding characteristics of the species. In bacteriological culture, for example, visualization of growth can take 2 to 3 months, with the possibility of a negative result even after visualizing bacteria in histopathological examination. PCR has been the best alternative, allowing quick detection of the agent with high specificity and sensitivity and, in this case, was essential for the definitive diagnosis. Regarding treatment, the best approach consists of complete surgical resection with adjuvant and prolonged therapy (3 to 6 months) of combining 2 or more antibiotics effective against slow-growing mycobacteria, as well as clarithromycin, clofazimine, rifampicin, fluoroquinolones, aminoglycosides, and doxycycline. Treatment with associated antibiotics should be initiated if surgery is impossible. Care is also needed regarding compliance with the treatment time, as interruption can lead to significant remission of the lesions and induction of resistance to the active ingredients. In this cat, remission of the lesions occurred after therapy with doxycycline alone. However, the duration was shorter than recommended in the literature.
Keywords: cat, Santa Catarina, dermatopathy, Feline leprosy, M. lepraemurium.

Título: Micobacteriose cutânea em uma gata

Descritores: gato, Santa Catarina, dermatopatia, Lepra felina, M. lepraemurium.