Aedes albopictus can establish rural or intermediate yellow fever transmission cycle, alerts Dr. Pedro Vasconcelos

The Aedes albopictus could be the link between urban and wild cycles by establishing an intermediate or rural cycle, or even by transmitting in urban áreas

A novel finding in the world should open a new front of studies about yellow fever transmission in Brazil. According do Doctor Pedro Vasconcelos, virology physician and director of the Evandro Chagas Institute, in Pará, the next steps include collecting more mosquitoes to verify the minimum infection rate in nature; if they are found infected again, perform studies to verify the vector’s competence, necessary viral load for becoming infected and transmitting the yellow fever virus in nature, and many others involving laboratory animals to assess their ability to transmit the yellow fever virus in experimental (laboratory) conditions for these animals (rodents and non-human primates).

To the virologist, the Aedes albopictus, also called Asian tiger, can contribute to increase the risk of yellow fever urbanization. The most important thing is that it can even establish a rural or intermediate transmission cycle, he alerts. Dr. Vasconcelos stresses that the Aedes albopictus is the dengue transmitter in Asia (where the vector is secondary), and Chikungunya, where since 2004 it became an important transmitter in the Indian Ocean, Southeast Asia and Europe (outbreaks in France and Italy). This ability to transmit was associated to a mutation in the virus envelope protein (protein E); there are no records of natural infections by Zika virus involving this mosquito. In the New World, it had not been yet demonstrated the Aedes albopictus role as an arbovirus transmitter, even after 30 years after the species became endemic in Brazil after being introduced in the Country. Since the three viruses (dengue, chikungunya and zika) have been circulating in Brazil for some time, it would be no surprise if they infected the Aedes albopictus in nature. Experimental studies have demonstrated this ability, he adds.

Last July, the paper Potential risk of re-emergence of urban transmission of Yellow Fever virus in Brazil facilitated by competent Aedes populations, that counted with Dr. Vasconcelos, was published in the international journal Scientific Reports. By that time, the risk of re-emergence of urban transmission of the yellow fever virus in Brazil was already considered plausible. Asked if we are closer to this, the specialist stresses the risk has increased, because now it is known that the yellow fever virus can replicate in this species in nature. And this mosquito can act as a bridge vector, i.e., a link vector between the urban and wild cycles by establishing an intermediate or rural cycle, or even itself transmitting in urban areas, what would be less likely, he adds.

To the virologist, the presence of the virus in Aedes albopictus could have originated either from infected monkeys or humans living in these intermediate areas (rural areas) in the early stages of infection (viremia period), when the virus is circulating in the bloodstream and can infect mosquitoes. Since the albopictus lives mainly in these regions, it is quite possible the mosquitos infection was acquired from humans who were infected in the forest. But we cannot rule out the possibility of the infection being acquired from monkeys, he admits.

Dr. Vasconcelos also stresses Dr. Ricardo Lourenço de Oliveiras collaboration, director of the Oswaldo Cruz Institute (IOC), and adds he should be included in the upcoming researches. He is also performing similar studies in Rio de Janeiro with Aedes albopictus specimens collected in his State. He is a fantastic entomologist. Therefore, we should gather efforts in order to speed up these studies, he ensures.…