Epidemiological Significance of Seasonal Variations in Rodent-Ectoparasite Distribution

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Abstract
The seasonal prevalence of the rodent-ectoparasites Xenopsylla cheopis (Siphonaptera) and Laelaps hawaiiensis (Acarina) frequently parallel the case incidence of endemic typhus fever of which X. cheopis is a potential vector. Employing monthly data for 1934, comparisons are made, using the correlation coeff., of parasite prevalence in Jacksonville, Fla., with typhus cases in Fla. and Ga.; of parasite prevalence in Mobile, Ala., with total Ala. typhus cases; and of parasite prevalence in Honolulu, T. H., with a 7-year average of reported typhus cases in Honolulu. Best results are obtained when a one-month lag is employed to compensate for the incubation period and a delay in reporting cases. In Jacksonville the two spp. were about equally abundant and both correlated with typhus incidence. In Mobile X. cheopis was the most abundant and was the only sp. correlated with typhus incidence. In Honolulu X. cheopis was negatively correlated with typhus incidence while L. hawaiiensis was much more abundant and exhibited a positive, although not significant, correlation. The low incidence of reported cases, making extrapolations necessary, and the fact that the vector potentialities of L. hawaiiensis are unknown forestall the drawing of definite conclusions, but it is suggested that X. cheopis is an important vector in Jacksonville and the major vector in Mobile, while it cannot be incriminated in Honolulu from available data.