Feline leprosy
Mycobacteria cause a range of clinical symptoms in cats, ranging from localised skin conditions to disseminated, often fatal, infections. Mycobacteria are Gram-positive, aerobic, non-spore forming, non-motile members of the Actinomycetales order of bacteria. The high lipid content of the cell wall results in the retention of hot carbolfuschin stain after treatment with acid and alcohol, rendering the organisms acid-fast when stained with ZN of Fite's stain. Mycolic acid, the major lipid in the cell wall, plus cord factor and wax D are partly responsible for the capacity of the organism to survive within phagocytes, which gives rise to the typical granulomatous immune response by the host.
Conceptually, mycobacteria can be divided into three groups:
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those species that are obligate pathogens (e.g. tuberculous bacteria)
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those that cause leproid/tuberculous granulomata and cannot be cultured by routine laboratory methods (lepromatous mycobacteria)
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those that have pathogenic potential but are generally considered to be opportunistic saprophytes (rapidly growing and slowly growing mycobacteria)
Mycobacterium leprae, the aetiological agent of leprosy in humans, gives rise to a chronic granulomatous disease that affects primarily the skin and peripheral nerves, and secondarily some internal organs such as the testis and the eye; viscera are seldom involved. Depending on host resistance, leprosy may present as a benign disease (tuberculoid leprosy) or as a malignant disease (lepromatous leprosy), with a spectrum of intermediate stages appearing between the two. Immunity against leprosy depends on the cell-mediated immunity of the host, and this is severely compromised in the malignant (lepromatous) form of leprosy. Although culture of
M. leprae has never been achieved in artificial media, the bacterium may be grown in several experimental animals, including the armadillo, non-human primates, and to a certain extent, rodents. Naturally acquired leprosy has been reported in wild nine-banded armadillos (Dasypus novemcinctus) and in three species of non-human primates (chimpanzees [Pan troglodytes], sooty mangabey monkeys [Cercocebus atys] and cynomolgus macaques [Macaca fascicularis]), thus qualifying leprosy as a zoonosis.
Leprosy in cats
Feline leprosy comprises two different clinical syndromes, one tending to occur in young cats and caused typically by M lepraemurium and M. fortuitum/peregrinum group. 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 well on routine laboratory media. The clinical course of the disease is usually aggressive, with a tendency towards local spread, recurrence following surgery and development of widespread lesions over several weeks. Most affected cats tend to reside in both suburban and rural environments.
Treatment