Anopheles, a genus of mosquitos, is best known as being the primary vector of the deadly disease called Malaria. While it was previously known that the female anopheles carries the virus responsible for malaria a new study has revealed that the Anopheles species is also a vector for another virus, the Mayaro.The Anopheles has aided in the rapid spread of the virus across the Americas and the Caribbean.
The emerging Mayaro virus got its name from the place of its first discovery i.e. Mayaro county located in Trinidad. Since its first discovery, dating back to 1954, there have been sporadic outbreaks of the Mayaro and the virus has been causing fever, muscular pains, eye pain, headache, nausea, diarrhea, an ache in joints, rash and vomiting in several South and Central American states.
In recent reports cases of patients affected with the Mayaro has been reported in foreign countries as well. As the reports suggest the virus has spread to the Netherlands, France, Switzerland, and Germany among others.
Jason Rasgon, a senior researcher and co-author of the study said, “Because the symptoms of Mayaro infection are similar to those caused by other arboviruses [arthropod-borne virus] such as dengue and chikungunya, its prevalence in areas where these other viruses circulate may be higher than reported,”. Mr. Rasgon is also a professor of entomology and disease epidemiology at the College of Agricultural Sciences, Pen State University.
Rasgon further explained that before this study it was thought that the Hemagogus, a canopy-dwelling genus of mosquitoes, was primarily responsible for carrying and spreading the Mayaro virus. Human infections are infrequent and irregular, he said, mainly because the Hemagogus species dwells in areas which are close to the forests and the mosquito tends to feed on primates.
Humans are understood to be non-preferred prey of the Hemagogus genus. When the mosquito introduces the virus into the humans, it can quickly trigger an epidemic as other mosquito species could assist with the spread and the disease could become uncontrollable.
“With the recent increase in imported cases, there are invasion concerns similar to those associated with Zika and chikungunya viruses,” Rasgon said.
“But little is known about the range of mosquito species that are capable vectors of Mayaro, so our aim was to address that knowledge gap.” The researchers in this study tested the behavior of 6 species of mosquitoes—Aedes aegypti, Anopheles freeborni, An. gambiae, An. quadrimaculatus, An. stephensi and Culex quinquefasciatus.
The tests were aimed to investigate the ability of each species regarding the transmission of two strains of the Mayaro virus. The four Anopheles species were selected to and tested in different geographical areas: North America (An. freeborni and An. quadrimaculatus), Africa (An. gambiae) and Southeast Asia (An. stephensi).
Virus-infected human blood was used in the study and the mosquitoes fed on the infected blood through a glass feeder. Each species was assessed on a weekly and fortnightly basis after the introduction of the infection.
The results were broken down into 4 classes;infection rate (change in the number of mosquitoes with infected bodies), dissemination rate (change in the number of mosquitoes with infected legs among those with positive bodies), transmission rate (change in the number of mosquitoes with infectious saliva among those with positive legs), and transmission efficiency (change in the number of mosquitoes with infectious saliva among the total number analyzed) were noted.
It was discovered from the obtained results that the Aedes aegypti and Culex quinquefasciatus were inefficient vectors of the Mayaro virus as the infection and transmission rates were very poor. However, in a separate and more recent study that is published in PLoS Neglected Tropical Diseases, demonstrated that all four Anopheles species were competent laboratory vectors of the virus.
“The transmission cycle of Mayaro involves mostly nonhuman primates and birds, although there is some evidence of circulation in rodents and marsupials,” he said.
It is notable that according to researches the Anopheles genus feeds on blood very frequently between their egg-laying cycles and this high frequency of bites increases the chance of virus transmission.
“Our results suggest that Anopheles species may be important vectors driving the emergence and invasion of Mayaro virus across geographically diverse regions of the world, and more research is needed on their epidemiological role in virus invasions,” Rasgon said.