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Black flies, also called buffalo gnats, are a biting fly that tend to swarm around your head and face.

Gnats have been particularly nasty this season, so much so that the flying pests have killed chickens on farms across the Felicianas this spring.

Experts and residents aren’t sure why the gnats are so bad this year, but there's speculation flooding along the Mississippi River has contributed. Talk to almost anyone who’s hunted, hiked or just been outside in the area – especially around St. Francisville — and they’ll liken it to a plague.

“The gnats always hit quickly and when they do, they hit with a vengeance,” LSU AgCenter county agent for horticulture Jessie Hoover said.

Hoover said farmers have reported the presence of the black flies, or Buffalo gnats, for the last two weeks. The AgCenter says multiple poultry farmers have reported gnats killing some their stock, and Hoover said that, in her own travels, it's become almost intolerable to be outside.

“They are worse the closer you get to the Mississippi River, they tend to be worse at people’s houses and waterways,” she said. “When I come to Clinton they’re not bad at all, a few here or there but the further west you go the worse they get, like in St. Francisville.”

Though buffalo gnats bite humans and other animals — and all livestock is potentially at risk — poultry have turned out to be particularly susceptible this year. The gnats typically cluster in an animal’s airway in such high numbers that it suffocates them or releases their toxins into the animal's esophagus.

Animal Health Services veterinarian Sonya Brouillette, based in St. Francisville, said she’s received reports from six farms in the area about chicken deaths, and has heard of gnat-bitten horses suffering from irritated or infected ears. 

North of the state line, researchers at Mississippi State University’s Extension Service caution farmers annually about buffalo gnats. In addition to suffocation, animals could stampede and trample smaller animals, and some gnats can transmit viruses among turkeys, geese, ducks and occasionally chickens.

Professor Jerome Goddard, who wrote the Mississippi extension service’s information sheet on the insect, said this year’s swarm almost certainly has to do with flooding and the high level of the Mississippi River, but researchers haven’t pinpointed exactly how that occurs. The Mississippi River has been at or above flood stage for several months in south Louisiana.

The gnats breed and live on moving water, he said, which could have caused eggs laid farther north to travel downstream and become a nuisance in lower Mississippi and Louisiana.

“They’re emerging pretty bad out of the Mississippi River, and when you have flood years that seems to trigger these emergences,” he said. “I would say it’s certainly a bad year, but I don’t know if it’s the worst we’ve had.”

LSU AgCenter entomologist and professor Lane Foil said that while he's heard anecdotal reports about the gnat influx, it doesn't seem to be at outbreak level. But, he said, researchers generally don't officially keep track year-to-year on gnat numbers, animal deaths and resident reports about large swarms.

Foil and Goddard did have some good news, though, in that a gnat's life cycle is not very long, so they should die out in the next two to four weeks. It’s just that it will be a nuisance being outside until then.

“If they can just bear it for two or three weeks it’ll go away, they’ll fizzle out,” Goddard said. “It’s a miserable couple of weeks but they’ll go away.”

For insects that are such a problem to people and animals, they're fairly easy to protect against. Gnats won't fly into enclosures or under any kind of overhang, they aren't strong enough to fly into a headwind and they're kept well enough at bay with insecticide.

There are also tales of dermatological products Skin So Soft or Victoria's Secret Amber Romance — or even vanilla — to repel gnats, though Hoover warned those haven't been scientifically tested.

Brouillette said that, at her own home, even the open porch provides enough of a roof to make sure the bugs stay away. She said they’re the worst at dusk and dawn, and almost completely inactive at night, so if pet owners can keep animals in a barn or some other type of enclosure with fresh water available and under a fan it’s likely to stop bites or swarms.

Follow Emma Kennedy on Twitter, @byemmakennedy.