V. Evaluation of Cross-Immunity against Type 1 Dengue Fever in Human Subjects Convalescent from Subclinical Natural Japanese Encephalitis Virus Infection and Vaccinated with 17D Strain Yellow Fever Vaccine
The initial results of a coordinated field and laboratory investigation of the ecologic factors associated with the maintenance, distribution, and dispersion of R. rickettsii indicate the widespread occurrence of spotted-fever infection in the indigenous wild fauna of Virginia and Maryland. Seven strains of spotted-fever rickettsiae were recovered from six species of native wild mammal trapped in Virginia: one from a cottontail rabbit, one from an opossum, and five from four species of wild rodent. Spotted-fever-group antibodies were detected in the sera of 15 different species of mammal included among five different orders. Similarly, complement-fixing antibodies were found in 18 species of bird belonging to three different orders, mostly to Passeriformes. These findings amply indicate the complexity of the ecosystem in which R. rickettsii is maintained and also identify some of the communities within the ecosystem involved in this tick-borne rickettsiosis.
Department of Rickettsial Diseases, Walter Reed Army Institute of Research, Washington, D. C. 20012.
Bureau of Insect and Rodent Control, Department of Health, Commonwealth of Virginia, Norfolk, Virginia. Present address: Department of Microbiology, University of Maryland School of Medicine, Baltimore, Maryland 21201.