'Unfortunately, the West Nile virus decomposes rapidly. We have about a 24-hour window to get the bird in here and get it tested," says supervising vector ecologist for the County of San Diego Vector Control Program, Chris Conlan. "Sometimes you get lucky and the bird happened to die in a spot where it stayed cooler. But [most likely] after 24 hours it was either out cooking in the sun, got ripped apart by a neighborhood cat, or eaten by ants -- ants can shred that thing fast; very often it's a race to see who gets there first." On Friday, January 27, a representative from Conlan's department will host "West Nile Virus in San Diego: Straight Talk for Birders" for the San Diego Audubon Society.
According to the Center for Disease Control, the "West Nile virus was first isolated from a febrile [or feverish] adult woman in the West Nile District of Uganda in 1937." The virus causes "severe human meningitis or encephalitis," or inflammation of both the spinal cord and brain.
In 1999 the virus appeared in the United States for the first time; it did not show up in California until 2002. As stated on westnile.ca.gov, "927 individuals from 40 counties have been infected with WNV [West Nile virus] in 2005." During this same year in San Diego there were five times as many birds (162, says Conlan) that tested positive for the virus than in 2004.
"Almost any bird can get it," Conlan says of the virus, "but certain birds are more likely to die from it. The list [of birds that are likely to die from the virus] is over a couple of hundred bird species long." The list includes birds from the family Corvidae, like crows, ravens, and blue jays. "Birds of prey also have a high death rate."
To keep the West Nile virus at bay, the Vector Control Program focuses on eliminating the only creature that can transmit the virus to humans: mosquitoes. "We have got a number of folks whose sole job it is to go out and kill mosquitoes," says Conlan. "We find the place [mosquitoes] breed: standing water. We need cooperation from the public in controlling all those small sources in the backyard -- the buckets, the kiddie pools, or an actual swimming pool that people don't want to take care of anymore [that] turns into a swamp."
To detect such breeding grounds in areas to which they do not have access, members of vector control patrol neighborhoods in a helicopter. From a helicopter, Conlan says, "We can see pools that [have] turned icky green. If a homeowner doesn't want to take care of it, or can't afford to, we'll throw mosquito fish in there and turn it into a pond [for free]."
When asked if people would benefit from removing birdfeeders and draining birdbaths, Conlan responds, "That's an overreaction. You cannot contract West Nile virus from direct contact with a bird that has it. Most [birds] get [the virus] and get over it quickly. Some might be ill for a few days, but once they are over it, they are no longer infected. I focus more on mosquito control."
But, as Conlan points out, only a small portion of local mosquitoes carry the virus. In fact, the San Diego Vector Control Program has not been able to locate one mosquito that tested positive for the virus. "We know it's here, because we're finding lots of positive birds, but we haven't found one. We've tested almost 150 pools of mosquitoes." A "pool" is 50 mosquitoes mashed together. "We take 50 mosquitoes, put them in a tube and smoosh the crap out of them and use the resulting mush to run the test, [which tells us] if there's any virus in the mix. If you did them one at a time, you'd go crazy."
Two species of mosquito on the West Coast are most likely to transmit the virus to humans. One is Culex tarsalis, commonly known as the Western encephalitis mosquito, and the other is Culex quinquefasciatus, or the Southern house mosquito. According to Conlan, there are two dozen species of mosquito in San Diego.
One method used to determine the presence of West Nile virus requires chickens. "Chickens are resilient. They get over [viruses] so fast, sometimes you never know they were sick. They have a strong and rapid antibody response, so that's what we look for in their blood. We poke them in the comb on top of their heads to get a drop of blood -- that's all you need -- and check for the presence of antibodies. Should any of these tests come back positive, you know the virus is circulating in this area."
Two people in San Diego were diagnosed with the West Nile virus last year. The state assigns cases to the counties in which they were diagnosed, not contracted. "Most probably, these are people who got [the virus] while traveling outside the county but did not fall ill until they got home," says Conlan. "We're almost certain they were not contracted here." -- Barbarella
"West Nile Virus in San Diego: Straight Talk for Birders"
Friday, January 27
Tecolote Nature Center (Tecolote Road/Sea World Drive exit from I-5, east on Tecolote Road. The Nature Center is at the end of Tecolote.)
Info: 619-682-7200 or www.sdfightthebite.com