Characterization of a Leishmania Isolate from the Rodent Host Neotoma Micropus Collected in Texas and Comparison with Human Isolates

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  • Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Biology Department, Youngstown State University, Epidemiology Division, US Air Force School of Aerospace Medicine, Washington, DC

We report the biological and biochemical parameters of Leishmania parasites (MNEO/US/90/WR972) isolated from a rodent host, Neotoma micropus, collected in Texas. Footpad inoculations of WR972 promastigotes into BALB/c mice and Syrian hamsters resulted in ulcerating lesions six and eight weeks post-inoculation, respectively. Using monoclonal antibody-stained touch preparations, amastigotes were found in the liver of both laboratory hosts. Infection of J774 macrophages with WR972 promastigotes supported the growth of amastigotes for 12 days at 35°C. The WR972 parasite was identified by enzyme electrophoresis as L. mexicana. Isozyme comparison of WR972 with 42 L. mexicana isolates (from humans and rodents) from four different endemic areas, including Texas, suggest that these parasite populations are identical for approximately 97% of their genetic loci. Pulse field gel electrophoresis (PFGE) of WR972 resolved 18 chromosomes with a size range of 300–>2,000 kb. The karyotype strongly resembles that of two other Texas L. mexicana isolates from humans. Taken together, the PFGE, hybridization, and isoenzyme data suggest that the wood rat isolate (WR972) is identical to parasites from human cutaneous lesions isolated in Texas and Central America. In addition, the biological characteristics of WR972, its infectivity of BALB/c mice and the Syrian hamster, and the potential of the isolate to infect, transform, and divide in J774 macrophages indicate that WR972 will be pathogenic in humans if transmission occurs. Health care providers should consider this possibility when studying the epidemiology and control of cutaneous leishmaniasis in Texas.

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