Leishmania tropica

Leishmania tropica (Wright, 1903) Lühe, 1906

ETYMOLOGY: Named for the tropics

SYNONYMS:Helicosoma tropica Wright, 1903; Herpetomonas tropica Patton, 1912; Herpetomonas furunculosa (Wright, 1903) Patton, 1922.

HISTORY: The first person to describe the organism was Wright in 1903 who saw them in the cutaneous lesion of an Armenian patient undergoing treatment in Boston. The sandfly was shown to be the vector of this parasite by Sergent et al (1921).

GEOGRAPHIC DISTRIBUTION: This organism is found in North Africa, Southern Europe, and the Middle East through India into western China. It is considered that this is mainly a human disease that on occasion also infects animals.

LOCATION IN THE HOST: In the mammalian host, the only stage that is present is the amastigote that is found within histiocytes and macrophages in the skin.

DIAGNOSIS: For cutaneous lesions a diagnosis by identifying organisms within cells on aspirate cytology (Wright’s or Giemsa stain) or histopathology of excised lesions is the method of choice. Although not reported in cats, PCR tests on infected tissues should be very sensitive and specific.

IDENTIFICATION OF THE PARASITE: The amastigote stage of Leishmania tropica is indistinguishable morphologically from other Leishmania spp. and that of the Trypanosoma cruzi. The amastigote stage is round to oval, is 1.5 to 4.0 m in diameter, and contains a large nucleus and a smaller kinetoplast. The amastigotes appear slightly larger in impression smears than in histologic sections due to flattening and the different methods of fixation.

LIFE CYCLE: Within the mammalian host the parasite grows and multiplies within macrophages and histiocytes of the skin at the site of the bite by the sandfly vector. Leishmania tropica is transmitted between hosts by the bite of infected sandflies of the genus Phlebotomus. Within the sandfly are found the flagellated promastigote forms of the parasite that are similar to the stage found in cell-free cultures.

CLINICAL PRESENTATION AND PATHOGENESIS: There is a report of two clinical cases of lesions of the Leishmania tropica type in cats in Iraq (Machattie et al, 1931). These two cats were found to have ulcers and organisms that were identified as probably being due to Leishmania tropica. The cats appeared thin, but healthy. One cat had an extensive lesion on the nose, a small ulcerating sore on the left eyelid, and three papules on the left ear. The other cat had a single sore on its nose. Postmortem examination of the cats revealed no organisms within the deeper tissues. A cat from Marsellaise was found at autopsy to have numerous skin lesions that contained numerous organisms that were called Leishmaniainfantum (Dunan et al., 1989). The cat had presented to a local veterinarian with lesions that had began as erythematous lesions that later developed pustules. The lesions were on the top of the head and on the neck. After three months following anti-inflammatory and antibiotic therapy, the cat was euthanatized at the request of the owner. Only the skin lesions were submitted, thus, it was not possible to ascertainif there were organisms present in other body tissues.

TREATMENT: There are no reports of attempted treatment of infected cats.

EPIZOOTIOLOGY: Overall, very few cats have been examined for the presence of Leishmania tropica. It has been considered that they do not play a major role as mammalian hosts of this parasite, and at this time, it is believed that human beings serve as the major reservoir of infection.

HAZARDS TO OTHER ANIMALS: Transmission to other animals is unlikely. Transmission could occur by direct inoculation of the organisms, but under most circumstances, this would probably not occur.

HAZARDS TO HUMANS: Cats could serve as sources of human infection, but currently humans are considered to be major reservoirs of this parasite. However, personnel need to be protected from possible accidents that could introduce the organisms into their skin.

CONTROL/PREVENTION: Control and prevention of the disease in cats would, in part, be based on reducing the number of cases within the human reservoir of infection.

REFERENCES:

Dunan S, Mary C, Garbe L, Breton Y, Olivon B, Ferrey P, Cabassu JP. A propos d’un cas de leishmaniose chez un chat de la region Marseillaise. bull Soc Fran Parasitol 7:17-20.

Machattie C, Mills EA, Chadwick CR. Naturally occurring oriental sore of the domestic cat in Iraq. Trans Roy Soc Trop Med Hyg 25:103-332.

Sergent E, Sergent E, Parrot LM, Dinatien AL, Béguet ME. 1921. Transmission do clou de Biskra par le phlébotome (Phlebotomus papatasi Scop.). Compt Rend Acad Sci 173:1030-1032.

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