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Lab Monitors West Nile Virus in CA
Based on tests performed in the laboratory of UCD Entomology Professor and Director of the Center for Vectorborne Diseases John Edman, the California Department of Health Services announced in August the first evidence for West Nile Virus (WNV) in the State of California this year. The tests conducted at UCD were performed on mosquitoes collected in the Imperial Wildlife Area on the southeast rim of the Salton Sea. Tests on sentinel chickens in the same area indicate that they too were likely carrying WNV.

The UCD Center for Vectorborne Diseases has the largest West Nile research and testing programs in the state, and plays a critical role in the monitoring and diagnosing of the disease in California. During the 2003 season, researchers at the Center tested more than 5,000 groups of 1 to 15 mosquitoes each. They also maintained and tested populations of "sentinel chickens", which are housed outdoors and therefore likely to be bitten by mosquitoes. The group also tested tissue samples from other birds and mammals in an ongoing monitoring program.

In another Entomology laboratory, Professor Thomas Scott and his students discovered previously that C. tarsalis is the one species of mosquito (out of approximately 200 found in the U.S.) that is most effective at transmitting the disease to hosts such as birds, horses and people. Their work indicates that this species is especially likely to pass the virus through its eggs to its offspring, making it a particularly dangerous vector of WNV and related diseases. One of the goals of the research in the Scott laboratory is to improve the surveillance and control of mosquito transmitted diseases.

Entomology Professor Helps Find Key to Honey Bee Sex Determination
Researchers at UCD, along with their colleagues in Germany and Norway, have discovered a key genetic signal that helps determine maleness and femaleness in honey bees. The finding was published in the August 22 issue of the journal Cell.

For over 150 years scientists have understood that male Hymenoptera develop from unfertilized eggs, and therefore have half as many genes as females who develop from fertilized eggs; females get one set of genes from both their mother and their father. Yet the actual genes and mechanisms involved in the expression of each sex was not well understood.

Robert Page and Kim Fondrk of the Entomology Department of UCD, along with Marty Beye and Martin Hasselmann from the Martin Luther University of Halle/Wittenberg in Germany, isolated a gene in the honey bee that they call the complementary sex determiner, or csd. There are at least 19 variants of the csd gene, and female honey bees always have two different versions of the gene. Males, with only one set of chromosomes, will always have one variant of the gene.

When the scientists inhibited one of the two genes in females, she developed male gonads. Inhibiting the expression of the gene in males had no effect. The researchers concluded that the proteins made by the two different versions of csd work together to form a single molecule that acts to express "femaleness" in the bee. If only one copy of the gene is present, this complex molecule is not formed, and the bee develops into a male.

This research helps explain why inbred colonies produce fewer female workers and more males - with less genetic diversity fertilized eggs are more likely to have two identical copies of csd, which acts as though it is a single gene, and the egg is destined to become a male. Understanding sex determination in bees will help beekeepers select for desirable traits in female worker bees without suffering the consequences of increased male production.