Molecular detection of Mansonella mariae incriminates Simulium oyapockense as a potentially important bridge vector for Amazon-region zoonoses.

OBJECTIVE

To assess the emergent zoonotic disease risk posed by the voracious human-biting blackfly species Simulium oyapockense in the peripheral regions of an expanding urban centre situated deep in the Brazilian Amazon rainforest.

METHODS

We performed nine human landing catches at three periurban sites surrounding the Brazilian Amazon town of São Gabriel da Cachoeira. Using the detection of non-human primate filarial parasites as an indicator of the zoonotic disease threat posed by a biting insect, we screened 3328 S. oyapockense blackflies for the presence of zoonotic filarial DNA with an ITS-1 PCR assay and Sanger sequencing.

RESULTS

Between 98 and 100% of the biting insects captured during our nine collections were identified as S. oyapockense; at our three collection sites and during our three seasonally-distinct collections this species was captured at rates between 28 and 294 blackflies per hour. PCR screening of the march-collected S. oyapockense detected infectious-stage (L3) Mansonella mariae parasites (which are only known to infect non-human primates) in >0.15% of the tested head samples.

CONCLUSIONS

Our results show that residents of the periurban regions of São Gabriel da Cachoeira are routinely exposed to the bites of S. oyapockense blackflies which have previously fed on non-human primates.