The role of monkeys, mosquitoes, and humans in the occurrence of a yellow fever outbreak in a fragmented landscape in south Brazil: protecting howler monkeys is a matter of public health

A recent (2008-2009) outbreak of sylvatic yellow fever caused the death of seven people and over 2,000 howler monkeys (black-and-gold, Alouatta caraya, and brown, A. guariba clamitans) in the state of Rio Grande do Sul, Brazil, spreading panic among the population. The fear of the disease and the misinformation about its relationship with howler monkeys led inhabitants of several regions to exterminate these primates from the forests near their homes. In this paper we describe the theoretical background supporting the idea that howler monkeys play an important role in fighting yellow fever via the surveillance of virus circulation and stress that they are not responsible for the re-emergence of this African infectious disease, its transmission, or its fast spread through the highly fragmented landscape of the state of Rio Grande do Sul. We also describe how this scientific information has been used in the campaign "Protect our Guardian Angels" that was launched to inform the public and the media about the actual relationship of these regionally threatened species to the disease. The campaign is run and supported by educational, scientific, governmental (health- and environment-related) and religious institutions, and NGOs, an alliance in favor of biodiversity conservation and public health that has been effective in changing the quality of the news media, but that still requires a great effort to achieve the necessary level of population awareness.