| Abstract: | The annual prevalence of Leishmania mexicana in Neotoma micropus from South Texas was studied by testing 192 N. micropus from 16 localities for L. mexicana. Forty-six Sigmodon hispidus from four of these localities also were tested. Seasonal transmission was investigated through trap-recapture studies at three localities and evaluation of infections in juveniles. Eighteen N. micropus from four localities tested positive for L. mexicana. Annual prevalence at these localities ranged from 5.6% to 54%. This range of prevalence supports the hypothesis that N. micropus is a reservoir of L. mexicana in Texas. Infections were most frequently transmitted in the fall; transmission also occurred in the spring. No S. hispidus tested positive. A simulation model of transmission of L. mexicana among N. micropus by Lutzomyia anthophora was developed to predict the threshold vector density below which L. mexicana would be eliminated from a population of N. micropus within two years. Model results also supported the hypothesis that N. micropus is a reservoir of L. mexicana. Leishmania mexicana could be maintained in a focus with an initial annual prevalence of 5.7%, which approximated the lowest non-zero prevalence found in this study, and a peak annual vector density of only 11 female sand flies/woodrat. At a peak density of 3 flies/woodrat, the prevalence approached zero at the end of two years. Simulations indicated that if the initial prevalence of infection were 54%, the highest annual prevalence found in field studies, prevalence would remain above zero (2.5%) after two years even if there were no sand fly activity whatsoever. |
|---|