Leishmanial excreted factor (EF) serotypes in Sudan, Kenya and Ethiopia

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Abstract
Sudanese, Kenyan and Ethiopian leishmanial isolates from human visceral, cutaneous and diffuse cutaneous cases, various wild animals and sandflies were serotyped by diffusing their excreted factors (EF) in gel against a battery of rabbit antisera. The EF and antisera of an Israeli Leishmania tropica strain and an Indian L. donovani strain served as control markers of 2 defined serotypes; A and B, respectively. Most strains typed as serotype B strains irrespective of source, including 3 lizard strains. The EF of a strain from a Kenyan ground squirrel reacted with both control antisera, marking it a serotype AB strain. The EF of 2 Kenyan strains from gerbils did not cross-react with either control antiserum, although 2 other Kenyan strains from gerbils typed as serotype B strains. None of the strains typed exclusively as serotype A strains. By testing EF against an antiserum raised against a French L. infantum strain, serotype B strains could be separated into 2 subserotypes, B1 and B2. The Kenyan and Ethiopian strains typed as either subserotype B1 or subserotype B2 strains, with cutaneous and diffuse cutaneous strains and isolates from animals and sandflies caught in endemic regions of cutaneous leishmaniasis typing as subserotype B1 strains and the visceral strains and isolates from animals and sandflies caught in endemic regions of visceral leishmaniasis typing as the subserotype B2 strains. The Sudanese strains all typed as subserotype B2 strains irrespective of source. An Ethiopian, human, simple cutaneous isolate that typed as a subserotype B1 strain was clearly dermatotropic in Syrian hamsters following the intrasplenic inoculation of culture promastigotes. An Ethiopian, human, visceral isolate that typed as a subserotype B2 strain was clearly viscerotropic in hamsters. Two Ethiopian, human, diffuse cutaneous isolates that also typed as subserotype B1 strains were uniformly negative when administered intrasplenically, and only 1 was very weakly infective by way of the skin. The dissemination of amastigotes to the various organs of hamsters was monitored by necropsy at regular intervals. Leishmanial serotypes in Sudan, Kenya and Ethiopia, as defined by the gel diffusion of leishmanial excreted factors, generally match the trends shown by the epidemiology and clinical symptomatology of leishmaniasis in these countries. This overall serotypic picture with strains typing as serotype B strains irrespective of source differs from that seen in the Middle East, where the majority of strains tested have typed as serotype A strains irrespective of source.

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