November 7, 2017 Kim Krisberg 0Comment

In southern Texas, the city of Laredo hasn’t confirmed a single case of dengue in nearly 20 years. Just a short walk across the border into Mexico, the city of Nuevo Laredo has confirmed hundreds of cases of the mosquito-borne disease. Hector Gonzalez says the difference lays in the city’s robust commitment to public health-led mosquito control.

“If we can prevent just one baby born with birth defects (from mosquito-borne Zika virus) — you just can’t put a price on that,” said Gonzalez, director of health at the City of Laredo Health Department. “Health-wise, it’s certainly better to keep someone healthy than let them get sick. And it’s certainly cheaper too.”

When it comes to controlling the community’s mosquito population, the Laredo Health Department, which serves as the community’s vector control district, employs what’s known as an “integrated pest management” approach. That means officials focus on the source of the problem: reducing and eliminating mosquito breeding habitats. One method is using chemical larvicides to kill the insects before they reach adulthood. Officials also employ a natural larvicide technique — releasing up to 20,000 minnows into retention pools to eat the larvae that mosquitoes lay in standing water. The city also sprays in the spring during the heavy mosquito-breeding season. But two years ago, the city took a particularly innovative step to deny the disease-carrying pests one of their favorite breeding habitats: tires.

According to Gonzalez, the city has long had a problem with illegal dumping of tires. The litter is a boon to certain species of mosquitoes like Zika- and dengue-carrying Aedes aegypti, which can lay their eggs in a pool of water small enough to fit inside a bottle cap. Laredo already had an ordinance on the books that held tire shops to certain standards of tire storage, transport and disposal. But two years ago, local officials added an amendment to reduce the chance of tire dumping — when someone buys a new tire at a local shop, they have to leave their old one. If the customer is determined to keep their old tire, they pay a fee of $20. The result, Gonzalez says, is that the number of tires properly disposed of at the landfill has gone up by more than 50 percent. The public works sanitation truck that the city had dedicated to picking up dumped tires has gone from collecting about 250 in a day to about 30.

“This is a citywide source reduction effort,” Gonzalez told me. “Solid waste, parks, the health department — all of us are working together to enforce the message and make sure compliance is happening.”

And the efforts are working. Gonzalez reports that in the last two decades, Laredo has had just four cases of West Nile virus, no cases of chikungunya and six cases of Zika, which were all travel-related. Besides some Zika-related funding from the Centers for Disease Control and Prevention, nearly 100 percent of the Laredo Health Department’s mosquito control efforts are supported with general funds from the city.

Unfortunately, in the big picture of public health-led mosquito control, Laredo stands out as an exception, not the rule.

“Capacity at the local level is not where it should be in terms of vector control,” said Laura Hanen, interim executive director and chief of government affairs at the National Association of City and County Health Officials (NACCHO). “It’s eroded over time, even though we do — and will — continue to face threats as a result of mosquito-borne disease. We have to figure out how we’re going to support these activities going forward.”

In late October, NACCHO, in partnership with CDC, released a new study of local mosquito control capacity, finding that a majority of local jurisdictions are in need of improvements. Overall, the assessment — “Mosquito Control Capabilities in the U.S.” — received survey responses from more than 1,000 vector-control organizations, with 53 percent being local health departments, 20 percent mosquito control districts and 27 percent were other entities, such as public works or utility departments. (The entities in charge of mosquito control vary across communities, though it’s often the local health department that leads and oversees such efforts.) The NACCHO survey found that based on competencies developed by CDC and the American Mosquito Control Association, 84 percent of respondents were in need of improvement in at least one core competency area.

The top three areas that need improvement were pesticide-resistance testing, treating for mosquitos based on surveillance data, and routine mosquito surveillance and species identification. The survey found that only 54 percent of vector-control programs do routine surveillance for mosquitos. Though, of that 54 percent, 85 percent said they use the data to make vector control decisions. About half of vector-control programs perform larviciding and adulticiding, though about one-third don’t perform any chemical abatement activities. An overwhelming majority of vector-control programs surveyed — 86 percent — did not conduct pesticide resistance testing on mosquitos, a critical data point as mosquito-borne disease risks are only expected to increase.

The survey noted that while health departments are often on the front lines of mosquito-borne illness, there’s little data on their readiness for a mosquito-borne outbreak. In fact, the NACCHO survey report is the first nationwide baseline assessment of mosquito surveillance and control activities in the U.S.

“Our residents are fortunate because Harris County has local resources to support a robust vector-control program,” said NACCHO President Umair Shah, director of Harris County Public Health in Houston, Texas, in a NACCHO news release. “What the joint NACCHO and CDC survey has brought to light is that many of our local health departments are not so fortunate and federal support for these activities is paramount. Lives depend upon it and the health outcomes from mosquito-borne diseases, such as Zika, can be lifelong.”

Hanen at NACCHO noted there’s been erosion in federal funding for vector-borne disease support. In fact, federal proposals in Congress — such as repealing or raiding the ACA’s Prevention and Public Health Fund — could translate into a 12 percent cut in CDC’s overall budget, which would undoubtedly impact work on mosquito-borne disease at the state and local levels.

“One of our concerns is that Zika was a one-year emergency supplemental and when it ended, Congress didn’t act to shore up key CDC programs that support Zika response,” Hanen said. “One year in a crisis doesn’t allow for capacity building over time.”

In Memphis, Tennessee, the Shelby County Health Department is one of the luckier vector-control organizations supported with a local revenue fee that’s helped health officials slash mosquito-borne disease rates. According to Tyler Zerwekh, administrator of the health department’s Environmental Health Services Bureau, efforts began more than a decade ago when health officials were clocking dozens of West Nile cases per year. In response, they took the problem to the state legislature, which passed an additional 75-cent fee for utility payers in the county. That extra $9 per payer per year adds up to between $3.2 million and $3.6 million a year to support the health department’s vector control activities, including mosquito trapping and testing, larviciding and surveillance.

Before the new revenue fee, Zerwekh said the agency’s mosquito control was reactive or complaint-based. With the new funds, the agency could become proactive, trapping and testing mosquitoes year-round and spending the colder seasons focused on reducing mosquito-breeding habitats. The efforts have been a success, with West Nile cases declining from upwards of 40 cases in a year to a low of less than five. (Zerwekh reported that with so much rainfall this hurricane season, the health agency has documented eight cases this year.)

The county does have the option of raising the additional utility fee to $1 per month, and Zerwekh said that given the trajectory of emerging zoonotic disease, that may have to happen.

“With all the effects of climate change, it’s getting warmer and wetter and those are the two precursors to mosquito proliferation,” he told me. “I see this becoming a more pressing public health problem.”

His advice to other mosquito control districts and health officials is to “take your case” to state legislators. Show them examples like Shelby County, where a relatively small fee increase has resulted in dramatic disease reductions.

“We’ve been screaming at the top our lungs that other jurisdictions need to try this,” he said of the revenue fee. “Let the data drive the policy.”

For a copy of the new mosquito control survey, visit NACCHO.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for 15 years. Follow me on Twitter — @kkrisberg.

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