A few days after an autumn picnic near Los Peñasquitos Lagoon, a local grade-schooler comes down with the flu. Fever, chills, headache, and he can’t bring himself to get out of bed. His mother worries, but since it’s flu season…
Three days go by. The boy doesn’t seem to be getting any better. The mother begins to worry more. She wonders whether she should make an appointment at the doctor’s.
The next morning, the little boy is lying in bed with a blank stare. He’s unresponsive, and the mother panics, calling 911. The boy suddenly begins to talk about algebra and dinosaurs and baseball, all in the same garbled sentence. Then he doesn’t recognize his mother.
At the hospital, the doctor knows the symptoms. He’s seeing more cases like this one lately. He runs a blood test. Sure enough.
West Nile virus.
In the past, there were never more than 15 human cases of West Nile virus in a calendar year in San Diego County. So far in 2008, we’re at 23 cases, and climbing. Since the disease is often fatal to birds, dead birds are a sure sign that West Nile is around. Before this year, the highest number of birds that tested positive in a calendar year was 162. This year? Over 500. Four horses in the county are dead from the disease. Of the 40 “sentinel chickens” used for early detection, 13 have converted to West Nile, including all 10 in Los Peñasquitos Lagoon, 2 in Oceanside, and 1 in the Tijuana River Valley. In the past, no more than 1 chicken had converted. Of the 240 batches of mosquitoes that have been tested by the Department of Environmental Health, 37 are positive for West Nile, a higher percentage than ever before. In fact, we’ve never had more than 7 positive batches of mosquitoes in the past.
“West Nile virus is vectored from the bird world to the human world by mosquitoes,” says Chris Conlan, supervising vector ecologist for the Department of Environmental Health. “And this year has been worse by major magnitudes.”
THIS PARK IS CLEAN
A few hundred yards past the entry to Rose Canyon Open Space Park, along a dirt road off Genesee Avenue, Mary Dice spots a swollen area in a creek. “Standing water,” she says, stopping her white Department of Environmental Health truck. “It’s moving at this end and at that end, but there’s stagnation in the middle.”
Dice climbs out of the cab, heads around back, and pulls from her gear what looks like — and, as it turns out, is — a golf club with a ladle soldered onto where the head of the club should be.
“Golf courses have a lot of water features that need to be treated,” Dice says. “So once we get to know the guys, we ask for some of their old clubs. And then we saw off the head and solder a ladle on instead — voila!” She laughs, brandishing the handy tool. “High-tech mosquito-control instrumentation.”
Dice, 57, is a wiry, outdoorsy-looking woman with short, gray hair. A senior technician for the Department of Environmental Health, she’s worked there for over 18 years.
Dice’s department treats public lands — rivers, creeks, ponds, sewage spills — in an attempt to eradicate disease-carrying creatures such as rats and mosquitoes.
“Mosquitoes lay their eggs in standing water,” Dice explains. “It takes about a week, depending on temperature, for the eggs to hatch. The larvae go through four growth stages for the next week or so, before they turn into pupae. Then the adult mosquito emerges from the pupa and goes out looking for a blood meal.”
So the best way to find hundreds of mosquitoes in one place is to seek out their breeding grounds.
“Moving water actually drowns the larvae,” Dice says. “They have a siphon on their back ends, and they have to breach the surface with that siphon and take in oxygen on a regular basis. If the water’s moving a lot, then they’ll have to use more energy than they can take in. That’s not what larvae do. They rest up, and then go after food, and then they rest again. So that’s why mosquitoes lay their eggs in standing water.”
At least 25 species of mosquito live and bite in San Diego County. Only 4 species carry West Nile, but the others need to be watched as well, according to Dice. “At this time,” she says, “we don’t have dengue fever here. But it’s become common in Mexico and Texas, so we’re on the lookout.”
Dice and 14 other vector-control technicians are assigned to different areas in the county for monitoring and treatment. “We’re responsible for all the known sites in our areas,” Dice says, “and we’re responsible for finding additional sites. We try to make sure that the larvae aren’t around long enough to become adults and then fly off and bite people.”
Dice covers “five Thomas Guide pages” in her area, from just east of the Department of Environmental Health office on Hazard Way, near Tierrasanta, all the way to the coast, then north to Del Mar and south to Mission Bay Park. Her jurisdiction encompasses roughly 150 natural mosquito-breeding sites.
But lately, this area has also begun to include hundreds of algae-filled swimming pools that require treatment as well.
“This year’s been just hellacious,” Dice says. “And it’s mostly because of all the foreclosures. I mean, there must have been thousands of green swimming pools that we treated.”
The county health department has even started using its helicopter to spot potential mosquito pools in backyards.
“People are usually pretty surprised when we show up at their front door with a picture of their pool.” Dice chuckles. “But we operate on the principle of helping people. So if you have a green pool, and our helicopter spots it, and I find your house, then I’m not there to give you a lecture or citation or problem. I’m there to help you. If your pool filter’s broken, and you’re looking at thousands of dollars of repairs, and you can’t do it, we’ll be happy to provide you with mosquito-eating fish, and we’ll put them in your pool for you, and we’ll give you a card with a number to call if your fish die off for any reason. Or if you’re getting your pool repaired, then we’ll come fish them out and use them elsewhere.”