Four-Legged Animals Help the Contra Costa Mosquito & Vector Control District Get to the Bottom of a Possible Source of Mosquitoes

It’s not every day you have to call upon a goat to help you do your job, but during this year’s West Nile virus season, that’s exactly what happened.  Why goats? Well the answer actually starts with the fact that all mosquitoes need water. Females lay their eggs in water and all mosquitoes have to complete their life cycle in water.

In many areas like oceans, lakes and rivers, water is very visible, but in other areas including ponds and wetlands, the water can be obscured by vegetation. Tules and other foliage can grow numerous in these locations allowing water to accumulate and attract mosquitoes; but the thick plant life can make it very challenging for vector control inspectors to gain efficient access to the water for surveillance and treatment. That’s where the goats come in.

During this year’s very busy West Nile virus season, the Contra Costa Mosquito & Vector Control District focused much time and effort on finding the source of mosquitoes in Brentwood, because the majority of Contra Costa County’s mosquitoes and birds that tested positive for the virus in 2012 came from the town. District employees provided inspections, treated underground catch basins, and canvassed neighborhoods by going door to door, but birds and mosquitoes continued to test positive for West Nile virus. The infected mosquitoes raised the possibility people could become ill, so the District fogged the area seven times in an effort to knock down the adult mosquitoes before they could transmit disease to nearby residents.

One particular area the District’s state-certified inspectors suspected could be producing mosquitoes was a storm water detention basin located near Heron Park in the eastern section of the town. The dense vegetation in the basin created a major challenge for district employees who had a difficult time accessing the floor of the pond to look for and treat any water. So, after multiple efforts to conduct efficient surveillance of the entire pond that instead produced limited results, the District turned to Brentwood officials, County Flood Control officials, and property developers to find a way to clear the vegetation. Using machinery to clear the area was the first consideration, however the soggy ground made it likely the equipment could get stuck. That’s when Flood Control officials called in the goats to clear the way.

“We worked closely with city and county officials for several months to find a way to clear out the plant life. When they decided to bring in Goats R Us, we thought this just might work because we’d seen what the goats could do in other areas,” says the District’s Operations Manager Carlos Sanabria.

The goats got to work, needing seven days to clear the basin, before moving to on another detention basin nearby. The goats’ efforts succeeded in making the area accessible to District inspectors. With easier access, district employees could treat the pond with a time-release bacterial public health pesticide that kills young mosquitoes in the water, but does not harm other insects or animals in the water.  Soon the number of infected mosquitoes the District caught in traps near the pond started to decrease, suggesting the goats had succeeded in allowing proper surveillance and treatment in that particular area.

Not far from Heron Park however, West Nile virus continued to show up in neighborhoods providing evidence residential sources were still producing mosquitoes. That prompted District employees to encourage citizens to dump or drain standing water and reduce excess irrigation because it was causing mosquitoes to be produced in the runoff.

The District is getting a head start on 2013’s West Nile virus season by encouraging officials to take necessary steps to maintain the detention basins to prevent a re-occurrence of the same mosquito issues next year. It just goes to show we are all in this war against West Nile virus together; a war that requires unique strategies and in this case even called for an army of four-legged goats to fight the bite.

October, 2012