New World Zika Exchange

Common marmoset in northeast region of Brazil

Carmem A. Busko/Wikimedia Commons

In Africa, non-human primates act as natural reservoirs of infection for Zika virus (ZIKV), a mosquito-borne illness that causes congenital brain abnormalities (including microcephaly) and can trigger neurological disorders in humans. ZIKV was introduced to South America in 2013 and reached epidemic proportions by 2015. Understanding whether New World primates in South America could also act as ZIKV reservoirs is critical to disease management. The authors of a new study report finding ZIKV in urban and peri-urban populations of marmosets (Callitrichidae) and capuchin monkeys (Cebidae) in southeast Brazil.

Monkey carcasses collected in and around the city of São Paulo during a severe outbreak of yellow fever in 2016 and 2017 provided virologist Maurício Lacerda Nogueira of the São José do Rio Preto School of Medicine and his team the opportunity to also investigate for ZIKV. While assessing cause of death, they reported that a portion of the monkeys had died not from yellow fever but from attacks by humans and domestic pets. “It didn’t make sense,” says Nogueira. “It’s not easy to get a marmoset—they’re really fast animals.”

The team hypothesized that the monkeys were being captured because they were sick. Nearly 40 percent of the yellow fever-free carcasses tested positive for ZIKV. When Nogueira and his team experimentally infected four black-tufted marmosets, Callithrix penicillata, with ZIKV, they observed lethargy that he says would make the monkeys “easy to catch.” Mosquitoes collected from areas near ZIKV-positive monkey carcasses also tested positive for ZIKV, suggesting that mosquitos may be transmitting ZIKV to monkeys.

Having confirmed the presence of ZIKV in urban and peri-urban monkey populations, Nogueira says the next step is to figure out if these monkeys are transferring the virus to wild monkeys, with the potential to create a ZIKV reservoir. If the Zika virus establishes in wild populations, “It will be probing the [human] population all the time,” says Nogueira. “As soon as the herd immunity goes down, there will be an outbreak.” (Nature Scientific Reports)