• Megan Silveira, assistant editor

Four External Parasites Cattlemen Should Be Aware Of

Identifying the type of fly bugging cattle can help improve herd productivity.


Summer brings warm weather, sunshine and an excuse to enjoy ice cream more frequently. Although for livestock producers, this time of year also brings an abundance of flies.

While the buzzing pests can easily be swatted down by your family, livestock don’t have the same luxury. Sonja Swiger, Texas A&M University associate professor and veterinary and medical entomologist extension specialist, described flies as external parasites that affect all livestock.

“The impact of these insects can be well over $2 billion annually,” she said during a webinar, “Don’t Bug Me: Pest Control,” hosted by the National Cattlemen’s Beef Association (NCBA). Flies can fall into three families, but Swiger identifies “filth flies” as the group posing the biggest threat to the livestock industry. She said this group of flies is known to have a preference for laying their eggs in organic substrates, including latrines, household garbage, manure and manure-soiled animal bedding.

“Flies create stress and discomfort in animals and hinder their performance,” added Paul Kropp, national account manager for Central Life Sciences. “There’s a number of issues that come into play with a heavy dose of flies. We want to control flies to maximize herd efficiency and comfort to improve revenue potential.”

Swiger described the top four filth flies producers should be aware of, as well as traits and characteristics of each pest for identification purposes.


1. Horn Fly (Haematobia irritans)

Kropp said the horn fly is one of the largest concerns for pasture cattle located in North America. With fly counts potentially reaching into the thousands per individual animal, these pests pose a big problem. Annually, Kropp said losses from horn flies are similar in amount to losses from bovine respiratory disease (BRD).

This small insect is one Swiger said cattlemen should not take for granted, and she encouraged investment in a regular management program. Cattle are the top-choice in hosts for this fly, as their eggs are laid exclusively in fresh cattle manure.

The adult horn fly is between 3 to 5 millimeters in length, and Swiger said they are the smallest of the four flies on this list.

Despite their smaller stature, Swiger said the horn fly possesses piercing/sucking mouthparts that allow for both males and females to take in many small bloodmeals from their host. The horn fly will, on average, take 30 to 40 bloodmeals each day, she added.

Swiger said cattle will react to bites from horn flies by licking their backs, twitching their flanks, switching their tails and kicking their bellies. Frequency of these actions indicate a horn fly issue is present, she said.


2. Stable Fly (Stomoxys calcitrans)

The stable fly, like the horn fly, is heavily associated with cattle, Swiger said, but can find a host in any large animal.

“The stable flies are 5 to 7 millimeters long,” she describes. “Both males and females again are going to feed on blood, but they take a single meal a day.”

These flies lay their eggs in wet, decomposing matter, such as straw, wet hay or grass clippings. Swiger said these pests are associated more with vegetation than manure.

These flies can be physically identified by stripes on their thorax and the checkered pattern on their abdomen. Swiger said stable flies bite the belly and all four legs of an animal.

“The main characteristic that will let you know you’re dealing with stable flies is the animals will stamp or kick,” she said. Cattle bothered by stable flies will also often bunch into groups, which Swiger said can be detrimental to the animals as it can lead to increase in body temperature and a decrease in feed intake.


3. Face Fly (Musca autumnalis)

Swiger said the face fly comes in as the largest fly on the list, with adults reaching between 7 to 8 millimeters in length. She said they are very similar to the next fly on the list, the house fly.

“It’s actually quite hard for most people to tell the difference between a house fly and a face fly out in nature,” she explained.

While house flies typically are found in dwellings like houses or barns, Swiger said flies out in pastures are more likely a face flies. She lists gray-black abdomens and four thoracic stripes as distinct physical characteristics of face flies.

She said this particular pest is also typically seen more often in temperate zones, as they do not like the heat. Adult females feed on animal secretions, while males prefer nectar and dung liquids. Eggs of face flies are often laid in newly deposited manure.

The biggest concern with face flies, Swiger said, is their ability to transmit eye diseases and parasites as the pests gather on facial features of livestock, specifically the eye region.


4. Housefly (Musca domestica)

The final pest feeds on the same secretions (blood, sweat, tears and saliva) as the face fly, but possesses different habits, Swiger said. These flies can be identified by the same four stripes on their thorax, but Swiger points to their yellow abdomens as the factor that distinguishes them from the face fly.

Houseflies have diverse locations where their young develop. Swiger said they can call garbage dumps, livestock manure, open privies, poultry litter, soiled bedding, and fruit and vegetable waste home.

“The concern with these houseflies,” she said, “is that they can pick up a lot of different pathogens when they’re feeding on these different substrates.”

Animals respond to these pests by flapping their ears, shaking their head and avoiding their pens.

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