Leishmania braziliensis and Leishmania mexicana

Leishmania braziliensis and Leishmania mexicana

ETYMOLOGY: Named for the location in New World tropics

SYNONYMS: Leishmania tropica var. americana Laveran & Nattan-Larrier, 1912.

HISTORY: Spanish explorers soon discovered after conquest that in areas of the Andes their was the possibility of developing lesions of the nares that could prove disfiguring (Weiss, 1943). It is now believed that the lesions of this type are due to several species of leishmaniasis inducing organisms that are indigenous to the New World.

GEOGRAPHIC DISTRIBUTION: These organisms are found in the southern United States, Mexico, and Central and South America.

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. Some species seem to have a predilection for mucocutaneous areas of 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 these species of Leishmania are indistinguishable morphologically from other Leishmania spp. and that of the Trypanosama 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. New World leishmaniasisis transmitted between hosts by the bite of infected sandflies of the genus Lutzomyia. 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 have been a few reports of cutaneous leishmaniasis in cats in the New World. Craig et al. (1986) reported on lesions in the ear of a four-year-old long-haired domestic cat in Texas. The cat had no signs of systemic disease and was returned to its owners after a radical pinnectomy. Three other cats (1 male and two females) were found to have lesions in Venezuela (Bonfante-Garrido et al., 1991). On the male cat, the lesions occurred on the nose and ears; on the female cats lesions were confined to the nose. In all cases, organisms were observed in impression smears of the lesions.

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

EPIZOOTIOLOGY: Overall, very few cats have been reported to be infected with dermal leishmaniasis. It is believed that small rodents serve as the major reservoirs of infection with this species in the New World.

HAZARDS TO OTHER ANIMALS: Transmission to other animals could occur through direct inoculation of the organisms, but this would probably be unlikely.

HAZARDS TO HUMANS: Cats could serve as sources of human infection, but they are not 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, need to be directed at preventing the cats from coming into contact with infected flies. However, because both the cats and the flies are hunting the same small rodent that serve as reservoirs of this infection, it is likely that it will not be possible to prevent cats that hunt from becoming infected.

REFERENCES:

Craig TM, Barton CL, Mercer SH, Droleskey BE, Jones LP. 1986. Dermal leishmaniasis in a Texas cat. Am J Trop Med Hyg 35:1100-1102.

Bonfante-Garrido R, Urdaneta I, Urdaneta R, Alvarado J. 1991. Natural infection of cats with Leishmania in Barquisimeto, Venezuela. Trans Roy Soc Trop Med Hyg 85:53.

 

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