Louisiana’s West Nile, Zika Concerns Grow

Louisiana’s West Nile, Zika Concerns Grow

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Residents of flooded areas in south-central Louisiana are at risk for mosquito-borne West Nile disease, health officials warned last month. Orleans Parish remains vigilant about West Nile but is at greater risk now from travel-related Zika. Meanwhile, the city is on the lookout for mosquitoes carrying Zika, especially after Florida officials last week found the first batch of them in the continental United States.

Parts of south-central Louisiana have standing water now after a deluge that began on Aug. 12. An immediate, short-term reduction in the region’s mosquitoes was expected after flood waters drowned bug populations. But as that water recedes, mosquitoes are returning, and their numbers will start to grow in any remaining, standing water, according to Frank Welch, medical director of community preparedness at the state’s Department of Health. Recent floods increase the risk of West Nile virus, he said.



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An adult Aedes aegypti mosquito having a blood meal 


As people in south-central Louisiana empty their homes and dash outdoors, they’re in contact with mosquitoes.

In areas that flooded last month, West Nile virus transmission is a greater concern than Zika, Kristen Healy, LSU AgCenter medical entomologist, said last week. She’s working with others involved in Louisiana’s Zika-control efforts. Mosquitoes spread West Nile from infected birds to humans. The state’s primary vector or agent for West Nile virus is the southern house mosquito or Culex quinquefasciatus. “These southern house mosquitoes lay eggs, especially in more permanent water sources, and the emergence of adults is continuous throughout the state’s mosquito season,” she said. Late summer is the peak period for West Nile.

In recent years, the state’s West Nile cases have declined, however, according to Louisiana’s Office of Public Health. In 2012, 160 cases were reported after an outbreak from summer to fall. This year, the state’s West Nile cases totaled eight as of Aug. 20, and all of those were reported before the August flood, with three in Calcasieu Parish and two in Caddo Parish. One case was in West Baton Rouge Parish, with none in Orleans. In late August, the Department of Health said 14 cases of West Nile had been reported in the state this year, but none were related to the flood event.

Following the recent deluge, great numbers of floodwater mosquitoes, which haven’t been shown to transmit Zika virus, have appeared in south-central Louisiana. “Floodwater mosquitoes are often more of a nuisance than a health threat,” Healy said. “During flooding, their eggs hatch at the same time, and then very large numbers of adults emerge, seeking blood meals. They actively bite humans. Their role in West Nile virus transmission is limited, however.”

Meanwhile, all of Louisiana’s reported Zika cases have been travel related, with no known local transmissions, and the majority have occurred in Orleans Parish, Healy said. New Orleans is a travel hub, and the parish also hosts a population of Aedes aegypti, the yellow-fever mosquito that carries Zika. Fortunately, Orleans Parish has an excellent mosquito control program, she said.

“Zika risks are higher where you get Aedes aegypti the most and where there are lots of people and also lots of travel,” Claudia Riegel, director of the New Orleans Mosquito, Termite and Rodent Control Board, said last week. The city meets all three criteria. Signs are posted at Louis Armstrong Airport to raise travelers’ awareness about Zika, she said.

Orleans, Jefferson, St. Bernard, Plaquemines, St. Charles and St. Tammany are the only parishes in the state with stable populations of Aedes aegypti mosquito, which is Zika’s best vector or agent, Samantha Faulkner, spokeswoman for the state’s Department of Health said. If local transmission of Zika occurs, it’s likely to be in these parishes.

On Aug. 3, Mayor Mitch Landrieu said $500,000 was being added to city budgets to aggressively target two species that carry Zika—Aedes aegypti and the Asian Tiger mosquito. The city already had an annual budget of $3.5 million to monitor and control mosquitoes, termites and rodents. The control board’s work includes mosquito-population surveillance, public education, source reduction, eliminating breeding sites, biological control and pesticide use. Spray trucks and airplane spraying are used as needed.

Mosquitoes breed in standing water, Riegel said. Orleans residents are urged to dispose of tires and containers in yards; to turn over buckets, wading pools, trash cans and pet dishes; and to remove clutter. “They don’t necessarily do this now, and reminders are helpful,” she said.

In April, the city released a plan addressing Zika’s threats. The mosquito control board and the New Orleans Health Department are working with other groups to distribute information and make door-to-door home visits. The city is partnering with the state’s Department of Health, the federal Centers for Disease Control and Prevention, Tulane University School of Public Health & Tropical Medicine and the Louisiana Mosquito Control Association.

So far this year, 26 cases of Zika were reported in Louisiana as of Aug. 31, including 11 in Orleans Parish, four in Jefferson, four in St. Landry and two in Livingston. Eighteen of those victims were female and eight were male. Infected residents had visited one or several countries in the Caribbean and Central and South America.

In comparison, Florida had 507 travel-related cases and 35 locally acquired cases as of Aug. 31. Puerto Rico had 50 travel-linked cases and a staggering 13,791 cases that were locally acquired. New York had 625 travel-related cases.

Last Thursday, Florida agriculture officials said three mosquito samples in Miami Beach had tested positive for carrying Zika.

So is there any relationship between income and Zika? On the one hand, high-income people travel more, putting them at risk for contracting it. But lower-income residents of, say Puerto Rico or along the Gulf Coast, are less likely to have air conditioning and window screens, putting them in contact with mosquitoes.

Earlier this year, the Obama administration asked that $1.9 billion be approved to combat Zika. Congress adjourned this summer without okaying those funds. Meanwhile, the administration moved $589 from other projects, mainly Ebola fighting, to address Zika. As of early September, the CDC had dedicated most of the $222 million that’s available for its Zika work.

On Sept. 6, the U.S. Senate is expected to vote on a $1.1 billion Zika bill as Congress returns from recess.

“The CDC has awarded us three grants to fight Zika,” Faulkner at Louisiana’s Department of Health said. The largest grant was $200 million for epidemiology and laboratories, while $400,000 each was allocated to preventing Zika-related birth defects and to emergency health preparedness. “Also the state has spent about $2 million to combat Zika,” she said.

In addition, “the Louisiana Health Department has devoted $250,000 of its epidemiology budget to non-Zika diseases, including West Nile,” Faulkner said. “Mosquito abatement, meanwhile, is funded at the parish and local level.”

As for West Nile, fatalities from it peaked nationally at 286 in 2012, according to the CDC. Federal funding for West Nile and other insect-borne diseases has declined in the last decade, however. And that’s true even though instances of chikungunya and dengue viruses have grown in mosquito-infested parts of the nation.

People can develop Zika when they’re bitten by an infected Aedes species mosquito. Aedes aegypti is more likely to spread Zika than is Aedes albopictus. Infected individuals pass on the disease to their sex partners. Zika infection during pregnancy can cause severe defects in the developing fetus. Less serious complaints among those affected are fever, rash, joint pain and red eyes. Many infected people have no apparent symptoms, however.

After it was identified in Uganda in 1947, the Zika virus spread to equatorial Asia and then to the South Pacific, South America, Central America and the Caribbean. To date, no vaccine for Zika exists. And no human vaccine for West Nile has been approved.

In June, Pennsylvania-based Inovio Pharmaceuticals announced with GeneOne Life Science in South Korea that they’d been green-lighted to start a human trial to evaluate Inovio’s Zika DNA vaccine.

This year, Mayor Landrieu has urged Congress to appropriate money for Zika vector control and local preparedness. In May, he testified about those needs before a U.S. House of Representatives committee.