UC Riverside publishes research on mosquitoes, ticks


April 14, 2023

LOGO: UC RIVERSIDENew research from Riverside branch of the University of California (UC Riverside) finds that proteins responsible for activating mosquito sperm can be shut down, preventing them from swimming to or fertilizing eggs.

The study could help control populations of Culex pipiens, the common house mosquito, which can transmit brain-swelling encephalitis and West Nile Virus.

“During mating, mosquitoes couple tail to tail, and the males transfer sperm into the female reproductive tract. It can be stored there awhile, but it still has to get from point A to point B to complete fertilization,” Dr. Cathy Thaler, UC Riverside cell biologist and the study’s first author, said in the news release.

Key to completing that journey are the specialized proteins secreted during ejaculation that activate the sperm flagella, or “tails,” that power their movement.

“Without these proteins, the sperm cannot penetrate the eggs. They’ll remain immotile, and will eventually just degrade,” said Dr. Richard Cardullo, UC Riverside biology professor and corresponding author of the new study.

The study, detailed in the journal PLOS ONE, details a full portrait of all the proteins in the insect’s sperm, allowing researchers to find the specific ones that maintain the quality of the sperm while they’re inactive, and that also activate them to swim.

To get this detailed information the research team worked with a team of graduate and undergraduate students who isolated as many as 200 male mosquitoes from a larger population. They then extracted enough sperm from the tiny reproductive tracts for mass spectrometry equipment to detect and identify the proteins.

Previously, the team determined that sperm need calcium upon entering a reproductive tract to power forward motion.

“Now we can look in the completed protein profile we’ve created, find the calcium channel proteins, and design experiments to target these channels,” Dr. Cardullo said.

This kind of protein profiling offers a path toward controlling mosquitoes that is more environmentally friendly than other methods that can have unintended, toxic effects.

“We’ve given up on spraying pesticides all over, because that kills everything, good insects and bad, and harms other animals,” Dr. Thaler said.

“Our work sets the foundation for a form of biological control, which most would agree is preferable,” Dr. Cardullo said.

The operative word is control, rather than eradicate. Even though immobilizing the sperm would be 100% effective for the treated mosquitoes, it is not possible or desirable to kill all mosquitoes. This technology would change the proportion of fertile to infertile males in a given mosquito population, rather than wiping them all out.

Researchers warn of tick-borne diseases

The tick that spreads babesiosis is called Dermacentor albipictus. Photo shows female (left) and male adults. (U. Wisconsin/Susan Paskewitz)

The tick that spreads babesiosis is called Dermacentor albipictus. Photo shows female (left) and male adults. (U. Wisconsin/Susan Paskewitz)

Now that spring has arrived and temperatures are on the upswing and so is hiking. But with hiking come insect bites and on the increase in North America is babesiosis, a malaria-like disease spread especially between May and October by the winter tick, Dermacentor albipictus.

Indeed, recent research suggests an increase in the incidence of diseases transmitted by ticks around the world, not just the United States and Canada, due likely to climate change and other environmental factors. Among the tick-borne pathogens, Babesia parasites, which infect and destroy red blood cells, are considered a serious threat to humans and animals. All cases of human babesiosis reported in the United States have been linked to Babesia microti, B. duncani or a B. divergens-like species.

Now a research team led by scientists at the UC Riverside and Yale University reports the first high-quality nuclear genome sequence and assembly of the pathogen B. duncani. The team also determined the 3D genome structure of this pathogen.

“Our data analysis revealed that the parasite has evolved new classes of multigene families, allowing the parasite to avoid the host immune response,” said Dr. Karine Le Roch, a professor of molecular, cell and systems biology at UC Riverside, who co-led the study.

B. duncani mostly infects deer, which serve as the reservoir host during the pathogen’s asexual development. The parasite’s sexual cycle occurs in the tick after the tick bites the infected deer. When this tick bites humans, infection begins.

Dr. Le Roch urges people to be mindful of ticks when they go hiking.

“Check yourself for tick bites,” she said. “When you see your physician don’t forget to let them know you go hiking. Most physicians are aware of Lyme disease but not of babesiosis.”

About the Author

Ellen Wagner is a former digital editor for PMP magazine.

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