Yellow fever epizootics in non-human primates, São Paulo state, Brazil, 2008-2009

Abstract

Since 2000, the expansion of Sylvatic Yellow Fever (YF) has been observed in the southeast of Brazil, being detected in areas considered silent for decades. Epizootics in non-human primates (NHPs) are considered sentinel events for the detection of human cases. It is important to report epizootic events that could have impact on the conservation status of susceptible species. We describe the epizootics in NHPs, notified in state of São Paulo, Brazil, between September 2008 to August 2009. Ninety-one epizootic events, involving 147 animals, were reported in 36 counties. Samples were obtained from 65 animals (44.2%). Most of the epizootics (46.6%) were reported between March and April, the same period during which human cases of YF occurred in the state. Biological samples were collected from animals found dead and were sent to Instituto Adolfo Lutz, in São Paulo. Two samples, collected in two counties without an indication for YF vaccination, were positive for the virus. Another 48 animals were associated with YF by clinical-epidemiological linkage with laboratory confirmed cases. Because the disease in human and NHPs occurred in the same period, the detection of the virus in NHPs did not work as sentinel, but aided in the delineation of new areas of risk.

What Does the Future Hold for Yellow Fever Virus? (I)

“…First, the susceptibility to YFV of South American NHPs. In contrast, YFV is known to be far less pathogenic for African NHPs [2,103,104,148]. Taken together with the historical evidence described earlier this is wholly consistent with the concept that the virus was relatively recently introduced into the New World and evolution towards decreased disease severity has not yet reached the levels seen in Africa.…”

“…), squirrel monkeys (Saïmiri genus) and howler monkeys from the genus Alouatta [65][66][67][68][69][70]102]. Importantly, in these species, lethality was reported, reaching degrees of severity that were never observed in monkeys from the African continent [103,104]. Such susceptibility to severe YFV infection may reflect the relatively recent introduction of the virus into the Americas [2].…”

“…In this case, the virus would be likely to evolve towards a decreased pathogenicity in these species. In the meantime, as they often precede the occurrence of human cases, epizootics amongst NHPs are known to serve as a surveillance or early warning system [2,63,104].…”

“…On the other hand, as in Africa, even when considering the possibility of vertical transmission, viral amplification by the vector population alone is rather unlikely. Hence, YFV would need to spread into several species of NHPs with diverse susceptibility and mobility patterns [104]. Thus, it would persist and circulate in specific sylvatic regions of South America.…”

Distribución geográfica del mono aullador rojo (Alouatta seniculus) y la fiebre amarilla en Colombia

“…Sin embargo, no hay estudios detallados sobre la presencia de los primates no humanos como un factor de riesgo para la fiebre amarilla en Colombia, lo cual va más allá de la descripción de epizootias en el curso de brotes de la enfermedad en humanos. Por otro lado, son más comunes los estudios que se basan en los análisis de riesgo y en la priorización de las poblaciones humanas que deben someterse a la vacunación que en el uso de los primates no humanos como centinelas de la circulación viral en el ámbito selvático (5,15,17).…”