With a spike in the number of mosquitoes testing positive for the West Nile virus, some local residents have been critical of what they characterize as a lackluster effort to control the proliferation of the insects at the height of the mosquito season.
Vector officials defended their efforts, denying their agency was sluggish in its response, selectively applying solutions for political or other untoward reasons or otherwise making an inadequate effort to suppress the disease-carrying pests.
West Nile virus is a mosquito-borne virus that is transmitted between species, first identified in the West Nile subregion in the East African nation of Uganda in 1937. Prior to the mid-1990s, West Nile virus occurred only sporadically and was considered a minor risk for humans. Beginning in the mid-1990s it began to spread beyond the confines of East Africa, and in 1999 made its way to the eastern United States. By 2003, the first cases of West Nile virus appeared in California.
The main mode of West Nile virus transmission is through mosquitoes, which are the prime vector, with birds being the most commonly infected animal and serving as the prime reservoir host. Not all birds infected with West Nile virus develop sufficient viral levels to transmit the disease to uninfected mosquitoes, and thus are not contributors in the chain of infection involving humans. Some birds, however, can become significant carriers of the disease and will in some cases eventually succumb to the disease itself. In mammals, West Nile virus can result in encephalitis or meningitis, and in extreme cases lead to death.
Roughly 80 percent  of West Nile virus infections in humans are subclinical, with no recognizable or significant symptoms. In roughly 19 percent of the cases, what is referred to as West Nile fever develops following infection and an incubation period of between two to 15 days. West Nile fever falls short of neurological infirmity, but can entail symptoms such as elevated temperature, headache, fatigue, muscle pain or aches, malaise, nausea, anorexia, vomiting, myalgias and rash. Only about one percent of West Nile virus cases are severe and cross into the province of neurological disease, i.e., impacting the central nervous system. The aged, the very young, or those with suppressed or compromised immune systems are susceptible to developing West Nile encephalitis, which entails inflammation of the brain; West Nile meningitis, which involves inflammation of the meninges, which are the protective membranes that cover the brain and spinal cord; West Nile meningoencephalitis, which causes inflammation of the brain and also the meninges surrounding it, and West Nile poliomyelitis, spinal cord inflammation, which results in a syndrome similar to polio, which may cause acute flaccid paralysis.
Currently, no vaccine against the West Nile virus infection is available.
In 2012, the deadliest year on record with regard to the West Nile virus in the United States, 286 people died as a consequence of the disease throughout the country. The disease has also manifested in burros and horses in San Bernardino County this summer and monitoring of dead birds indicates that the virus was present in at least 21 of those creatures within the confines of San Bernardino County.
By July, on the far west side of San Bernardino County, West Valley Mosquito and Vector Control District officials noted a significant uptick in the presence of the virus, largely through the trapping of infected mosquitoes. In the first part of July, 6.7 percent of the mosquitoes trapped in the district, 48 of 714, tested positive for West Nile virus. In the last two weeks of July, the percentage of infected mosquitoes caught in traps increased to 25 percent, i.e., 27 of 107.
A sampling of the data from around the district shows that on June 26 trapped mosquitoes near Campus and Riverside Drive in Ontario tested positive for the West Nile virus.
On July 2 trapped mosquitoes in northeast Ontario, as well as near Cypress and Riverside Drive in Ontario, on Vineyard and Philadelphia in Ontario and at Ramona and Walnut in Chino tested positive for the West Nile virus.
On July 10, mosquitoes trapped near Campus and Riverside Drive in Ontario tested positive for the West Nile virus.
On July 11, trapped mosquitoes on Fourth Street in northeast Ontario tested positive for the West Nile virus.
On July 16 trapped mosquitoes on Parco Street in south Ontario, on Phillips Avenue in the in unincorporated county area near Chino, and at Vineyard and Philadelphia  and near Campus Avenue in South Ontario tested positive for the West Nile virus.
On July 17, mosquitoes on Fourth Street in northwest Ontario,  Cox Street between Mills and Ramona streets in west Montclair and at the Terracina Apartments at Archibald and Riverside Drive in South Ontario tested positive for the West Nile virus.
On July 26 mosquitoes on Fourth Street and north of E Street in north Ontario, on Cox Street in west Montclair and on Bellevue in Ontario tested positive for West Nile virus.
On August 2, mosquitoes caught in traps on Camino Sur  in Rancho Cucamonga, Bonnie Brae Street in  Ontario,  Cottonwood in south Ontario and on Baker Avenue in  north Ontario tested positive for the West Nile virus.
In mid-August, a man from Victorville contracted the West Nile virus, requiring hospitalization. A week later, a second human case turned up in the county, this time a man living in south Ontario.
West Valley Mosquito and Vector Control District serves the cities of Ontario, Montclair, Chino, Chino Hills, Rancho Cucamonga and the nearby unincorporated county areas. The district’s manager is  Min-Lee Cheng.
Late this summer, the West Valley Mosquito and Vector Control District and Cheng came under fire by residents within the district, particularly in south Ontario and in Chino, for what those residents consider to be a less than energetic effort to deal with the West Nile virus threat.
Residents in south Ontario complain of swarming mosquitoes at nighttime, during which periods they say it is impossible for humans or pets to venture out without enduring mosquito bites. Some have reported cold-like or flu-like symptoms, such as fever, headaches, fatigue, and muscle pain and aches.
The area in and near south Ontario includes the former Chino Agricultural Preserve, which features active and shuttered dairies, upon which many collections or pools of  still water proliferate and which exist as ideal breeding grounds for mosquitoes.
There are four stages in the mosquito lifecycle: egg, larva, pupa, and adult or imago. Adult females lay their eggs in stagnant water. The length of the first three stages — egg, larva, and pupa — typically last five to 14 days, but in the summer heat that cycle can reduce to as few as three days. Adult males live for about a week. Females in the wild live for up to two weeks.
As summer has progressed this year and with the rising heat and humidity of August and now September descending upon the Inland Empire, the mosquitoes proliferated. Critics of the West Valley Mosquito and Vector Control District maintain the district is attacking the problem in south Ontario less aggressively than the crisis dictates should be done.
Specifically, it is alleged that Cheng did not adequately prepare for the problem the district is now facing by hiring seasoned and experienced staff members ahead of time, but waited until August to bring in seasonal workers, an accusation critics say is backed up by the district’s employees’ time cards. Nor has the district carried out an effective prevention and eradication program in the environs of the dairy land or its surroundings, which would have entailed using helicopters to do a continual aerial survey to find stagnant water accumulations and conducting extensive ground operations to search out hidden water pools and then drain them or treat them.
Nor has the district carried out an effective spraying program or any spraying program in south Ontario or Chino. This is contrasted with the district’s repeated spraying in north Ontario this summer.
Critics suggested the northwest Ontario spraying was done by Cheng as part of a strategy to placate the district’s political leadership.
The West Valley Mosquito and Vector Control District’s board consists of elected and appointed leaders from the cities and county area within its jurisdiction.
The board is chaired by Chino Councilman Glenn Duncan. The other board members are Ontario Mayor Paul Leon, Montclair Councilwoman Carolyn Raft, Chino Hills Councilwoman Cynthia Moran, Rancho Cucamonga Public Works Director William Wittkopf and county representative William Sitton.
The area around Leon’s home in northwest Ontario was sprayed on July 10, July 23, July 25, August 1, and August 6. No spraying occurred this summer in south Ontario. Residents of that area suggested the district had shown more care and concern in northwest Ontario because Cheng was seeking to placate the leadership on the board, in particular Leon and Raft, who live most proximate to the area that had been treated with the pyrethin fog. Those sprayings took place at night, when the mosquitoes are most active and have taken to the air.
Cheng discounted those accusations, saying the district is working assiduously to deal with the West Nile virus threat and that the high incidence of infected mosquitoes in  the northwest Ontario and northeast Montclair areas drove the district’s action.
“We had a new record of West Nile virus infestation this summer,” Cheng acknowledged. “It  broke our previous record, set in 2008. We had a record number of mosquitoes with the virus in our traps. In 2008 we had 141 mosquitoes test positive for the virus. As of last week, we had 169 and that number continues to grow. It is very alarming, with fifteen percent testing positive for the West Nile virus overall in our district. In addition, we have eight chicken coops in the district where we test. Chickens make excellent sample subjects. When the mosquitoes bite chickens they do not get sick because they produce a huge amount of antibodies. Of the eight coops, five tested positive. Another alarming indicator is that as of today [September 11] we had 14 dead birds which tested positive in our district. Within our district so far this year only one human case has been confirmed by the health department. We have done fly-overs to look for swimming pools that may be mosquito-breeding grounds. We discovered a lot of pools we did not know about or which were recently put in above the 60 Freeway. We have begun processing the data and have begun contacting the owners of those pools and have had a quick response from people to get them cleaned. We have a lot of areas in backyards where we cannot see and have to rely on aerial surveillance to detect these breeding places.”
As to the spraying effort in northeast Ontario, Cheng said “two thirds” of the mosquitoes trapped in the northwest section of Ontario and the northeast section of Montclair tested positive for the West Nile virus. “I have never seen this high of an infestation,” he said.  He said the area had been sprayed on two occasions, to no avail. “We sprayed in the nighttime,” he said. “We did it twice. It was very unsuccessful. The weather conditions were not favorable. Spraying did not work for us the last time we used it, in 2005, and it failed this time. When you spray, you are concentrating on the adults. It is much more effective to focus on the larvae, spot them and kill the mosquitoes before they become adults. That is the way we are trying to do this. Killing adults is the least effective way to do it.”
At this point, Cheng said, the district is seeking to “discover and uncover more sources like rain gutters that get clogged up by leaves and create breeding grounds for mosquitoes even in the summer. Many of these breeding grounds are created by humans without their realizing it. It is amazing how we nurture mosquitoes that transmit disease to us. We are the ones who create problems for ourselves.”
Leon told the Sentinel that for both technical reasons and ones of public perception, the district has shied away from spraying to eradicate the pests.
“We were not getting the results we wanted and were not doing an effective job with the low pressure spraying,” the Ontario mayor said. “We did spray in the northwest corner of Ontario on a few occasions but I am told that when they sprayed, the wind conditions were wrong. When you spray on an east-west street like Fourth Street, you want the wind blowing so it traverses the street, blowing north or south. But the wind at night blows in the same direction as the street and the [insecticide] fog never makes it to where the stagnant water is and just blows away.”
In any event, Leon said, the public, or a large segment of it, is averse to the spraying. “What we’re doing is spraying with a geranium-based, naturally occurring biodegradable insecticide that has little if any danger to humans or animals, but just the very nature of spraying something that kills insects puts fear in the minds of people. The public is not in favor of us using this insecticide fog in their neighborhoods.”
Leon said that as a board member, he is confident “West Valley Vector Control is doing a good job of finding green pools through aerial surveillance and then drying up or eradicating these mosquito breeding grounds. We are pushing for environmentally friendly solutions like introducing a type of fish into the green water that will eat the mosquito larvae. I’m talking about pools that have been abandoned or deep ditches with water in them. The other option that we are pursuing is educating people to protect themselves. This is a new problem that is growing. Ten years ago was the first time we had West Nile virus in California.  We have a very proactive vector control district here. All a member of the public has to do is call and an investigation will begin. Once the presence of mosquitoes is confirmed, eradication will begin.”