The Investigation of a Sylvan Yellow Fever Epizootic on the North Coast of Honduras, 1954

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Abstract
Summary and Conclusions 1. Howling monkeys (Alouatta) died of histopathologically proven yellow fever in July and early August, 1954, on the coastal plain near La Masica, Honduras, in an ecological situation unlike that of epizootics experienced during the preceding five years in Panama and lower Central America. No naturally proven vector mosquitoes could be found on the coastal plain where the monkeys died. 2. Small numbers of Haemagogus spegazzinii falco, a proven natural vector in South America, were taken on mountain slopes in the tropical rain forest some 10 to 20 kilometers or more from the place where the monkeys died, but no evidence could be obtained of monkey mortality there. The authors believe the north coast of Honduras to be at or near the northern limit of the range of H. spegazzinii falco. 3. Haemagogus equinus, which has been shown to be capable of transmitting yellow fever in the laboratory, but from which virus has never been certainly recovered in the field, was the only Haemagogus species recovered at the place where the monkeys died near La Masica. This species which is widespread in Middle America has been taken by us in the Atlantic drainage as far north as the southwestern corner of the Mexican state of Tamaulipas which borders Texas on the Gulf Coast. 4. Aside from the predominantly ground-level biting Psorophora and Mansonia, which are not considered to be involved in the yellow fever transmission, the commonest arboreal mosquito was Trichoprosopon magnus. The ability of this mosquito to transmit virus is unknown. Another sabethine mosquito whose status as a vector is also not known, Sabethes chloropterus, was present in moderate numbers. This species has been present at other recent yellow fever episodes in Panama and lower Central America. 5. No human cases of yellow fever were recognized in the immediate area of the epizootic during, or in the months following the monkey fatalities.