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Studying Mosquito Parasites

District staff are assisting in a collaborative study on a mosquito parasite that is spearheaded by researchers from Stanford University and the University of Innsbruck in Austria. The parasite is a ciliate type of protozoa, Lambornella clarki, which is a single-celled animal that lives in water. Lambornella clarki is found in water that collects in tree holes, and can enter the body of the mosquito larvae of Aedes sierrensis, the western tree-hole mosquito. Inside the mosquito larvae, it multiplies and kills the hosts. If the host is not killed and develops into an adult mosquito infected with the ciliate, the females are not able to lay eggs. Lambornella clarki does not cause disease in humans and has been studied for its potential for biological control of mosquitoes.

Lambornella clarki ciliates were historically found in tree holes in the bay area, including some areas of San Mateo County. Dr. Jan Washburn, a trustee for Alameda Mosquito Abatement District and retired University of California Berkeley professor, has studied the organism extensively and trained Stanford researchers how to identify the ciliates and infected mosquito larvae. He is also familiar with sites where Lambornella clarki has been historically present.

San Mateo County MVCD technicians are collecting samples of water and larvae from tree holes, as are technicians from the Marin-Sonoma Mosquito and Vector Control and Alameda County Mosquito Abatement Districts. These samples have been submitted to the study to determine where the ciliates are still present. Lambornella clarki has been detected in a few samples so far. Ultimately, the researchers hope to study this parasite to better understand the evolution of disease.

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