Malaria-carrying Mosquitoes May Have Been a Vector for Millions of Years
Mosquitoes may have been a vector of the parasite malaria far beyond the existence of humans, according to a new study.
Malaria, a mosquito-borne disease that only reproduces within insect vectors, kills an average of 400,000 people annually. In 2016 alone, there were 216 cases of malaria worldwide, and in 2017, those cases went up to 219 million—making it a progressively hard disease to contain and treat.
Currently, there are no vaccines for malaria and it is not usual for an individual to be naturally immune to the disease, but a researcher from Oregon State University may have uncovered some clues about malaria’s origin that could someday reveal ways of interrupting transmission of the disease that kills so many people annually.
The Oregon State researcher, George Poinar Jr., suggested that early lineages of the anopheline mosquito, which is one of the mosquitoes along with the protozoa species found to infect humans, were present 100 million years ago.
Poinar is an international expert in understanding biology and ecology of the past through plants and animals preserved in amber, who was the first to discover a 15 to 20-million-year-old fossil mosquito that contained the malaria strain, Plasmodium, that infects and kills humans. He is also a researcher at Oregon State University’s College of Science, and is the corresponding author of the study, published in the journal Historical Biology.
Although humans weren’t around 100 million years ago, the mosquitoes tended to bite birds, small mammals and reptiles—similar to what they bite today.
In this new study, Pionar and his team suggest that the early lineage of disease-vector anopheline mosquito was discovered in amber in the form of a new genus—Priscoculex Burmanicus. The amber was found in Myanmar and dates back to the Cretaceous period.
The characteristics between the anopheline mosquito and this newly discovered ancient genus are very similar and suggest that anopheline diversified from their ancestral species during the mid-Cretaceous period, according to the study.
“This discovery provides evidence that anophelines were radiating—diversifying from ancestral species—on the ancient megacontinent of Gondwana because it is now thought that Myanmar amber fossils originated on Gondwana,” Poinar said.
In previous research, Poinar revealed that the origin of malaria may have come from a vectoring insect over 100 million years ago, but the answer was unclear until this new discovery that showed mosquitoes were a vector for malaria during this period of time.
Pionar also noted potential insect vectors with pathogens that may have contributed to a significant event in the history of earth: the extinction of dinosaurs.
“Insects, microbial pathogens such as malaria, and other vertebrate diseases were just emerging around that time,” he said.
Although there were other factors involved in ending the dinosaurs, their slow decline towards extinction over thousands of years leads to the question of whether insect vectors, such as mosquitoes, could explain their slow decline.