Virus may act as ‘late-life-acting’ biopesticide against malaria

WASHINGTON - A naturally occurring virus in mosquitoes could act as a “late-life-acting” insecticide by killing older adult mosquitoes that are responsible for the bulk of malaria transmission, found researchers from Johns Hopkins University and the Johns Hopkins Malaria Research Institute, Baltimore, Maryland.

Malaria infects hundreds of thousands of people each year and is the cause of over a million deaths worldwide. Insecticides are one of the main strategies currently used to control malaria transmission, however, evolving resistance to such therapies continues to impact such efforts.

“Late-life-acting” insecticides (LLAIs) are now being examined as a new approach for controlling malaria as they selectively kill older mosquitoes that spread the disease, while younger mosquitoes survive just long enough to reproduce.

“Reproduction allows for relaxation of evolutionary pressures that select for resistance to the agent. If resistance alleles exert fitness costs, there are theoretical scenarios under which resistance is not expected to evolve, leading some to provocatively term LLAIs as ‘evolution-proof,’” said the researchers.

Densonucleosis viruses (or densoviruses [DNVs]) are naturally occurring parvoviruses that have been identified in multiple mosquito species.

Some DNVs typically infect during the larval stage and are lethal, however, in this study researchers suggest that the Anopheles gambiae densovirus (AgDNV) may infect at low levels during early life and replicate to lethal levels at adult age.

Analysis following infection showed that although AgDNV levels increased modestly during larval development they still replicated slower resulting in significantly decreased virus levels during this stage.

Additionally, virus levels greatly increased in 7-to-10-day-old adults.

“Ultimately, we expect that a properly engineered LLAI AgDNV can be deployed in the field to significantly modulate malaria transmission,” said the researchers.

A prior study showed that H5N1 could replicate in the skin cells of feathers and further suggested that those that drop off the body could potentially contaminate the environment.

Here, researchers evaluated the environmental risk posed by contaminated feathers by inoculating domestic ducks with H5N1, collecting feathers, feces and drinking water three days following, and then storing them at 39 degrees and 68 degrees Fahrenheit for 360 days.

Results showed that H5N1 persisted the longest in feathers at both temperatures.

“These results indicate that feathers detached from domestic ducks infected with highly pathogenic avian influenza virus (H5N1) can be a source of environmental contamination and may function as fomites with high viral loads in the environment,” said the researchers.

The study has been published in the latest issue of the Journal of Virology. (ANI)