Understanding Fly Strike in Cattle & How to Prevent It

Fly strike in cattle is a serious and painful condition that can severely impact the health, comfort, and productivity of a herd.¹ Caused by flies laying eggs on an animal’s skin, fly strike can lead to maggot infestation that feeds on living tissue. For livestock owners, early detection and proactive prevention are essential to keeping animals safe, especially during warmer months when fly populations surge. The best strategy will combine regular monitoring with clean environments and the use of effective wound care and fly control products. Below, we’ll explore everything you need to know about fly strike in cattle, including how and why it happens, which animals are most at risk, and how to recognize the early signs. Most importantly, we’ll take a look at prevention and treatment strategies that can protect your herd's health all year long.

Fly strike in cattle, also known as myiasis, occurs when certain species of flies lay their eggs on an animal’s skin. When the eggs hatch, the larvae (maggots) burrow into the skin and start feeding on the animal’s tissue. They also release toxins that can cause inflammation and severe tissue damage. If not caught in the early stages, fly strike can lead to serious complications, including sepsis, necrosis, or death.

Fly strike in cattle usually occurs under a predictable set of conditions, most often involving:

• Warm, humid weather – Flies thrive in these conditions, causing populations to spike in late spring and through early fall.²
• Open wounds or abrasions – Injuries, surgical sites, or even insect bites can all attract flies.³
• Soiled or damp areas – Manure, urine scalding, or general lack of hygiene can lead to areas of moist skin that are ideal for egg-laying.
• Folds of skin or thick coats – These can trap moisture and go unnoticed, providing shelter for flies and maggots.
• Immobility or illness – Cattle that are immobile or unable to groom themselves are particularly at risk.

When it comes to treating fly strike, early detection is critical. A fly strike cow may show subtle signs at first, but the condition can worsen rapidly. Common symptoms to look out for include³:

• Restlessness or irritation – Cattle may stamp, flick their tails, or seem agitated.
• Excessive licking or biting at one area – The animal may attempt to groom the affected spot.
• Lethargy or decreased appetite – As the infestation progresses, the animal’s overall condition will decline, resulting in lethargy or a decrease in appetite.
• Fever or signs of systemic illness – Severe cases may lead to generalized infection.
• Foul odor – The wound or infested area often emits a strong, unpleasant smell.
• Discolored or necrotic skin – Tissue may appear blackened, moist, or sloughing off.
• Visible maggots – In more advanced cases, you may be able to see maggots moving in the wound or lesion.

Checking cattle daily during peak fly season can help you catch the condition before it advances.

While fly strike can affect any cow, certain animals and conditions make infestation more likely. Understanding these risk factors allows for more focused monitoring and prevention.

• Calving cows or recently castrated calves – Fresh wounds from birthing or castration create ideal sites for flies to lay their eggs.⁴ These areas are often moist and hard for the animals to reach or clean.
• Animals with diarrhea or urine scalding – Moisture and waste buildup around the hindquarters can also attract flies, and the skin in these areas may already be irritated or broken.
• Cattle with long or matted hair – Thick or tangled hair traps moisture and can hide small wounds or early signs of infestation. It also makes grooming more difficult, reducing the cow’s ability to keep flies away.
• Overweight or immobile cattle – Cattle that cannot stand or move easily have a harder time grooming themselves. This makes it easier for flies to land and infest unnoticed.⁵
• Poor hygiene and overcrowding – Unclean, crowded environments promote fly breeding and increase the risk of contact with infected animals. For this reason, regular cleaning and spacing can help reduce exposure.

By recognizing and addressing these risk factors early, you can take targeted steps to reduce the likelihood of fly strike, ensuring your cattle stay comfortable and healthy throughout the season.

While “blowflies” are the most commonly cited cause of fly strike, several fly species are capable of laying eggs that result in maggot infestation, including:

• Green Bottle Fly – This species is strongly attracted to moist wounds or soiled areas and is a leading cause of cutaneous myiasis in cattle.
• Black Blowfly – Known for rapid egg-laying, these flies often appear in early spring and are highly aggressive toward open wounds.
• Blue Bottle Flies – These flies tend to appear during cooler seasons and often infest surgical sites.⁶

Identifying the fly species common in your region can help tailor your prevention strategy, especially when selecting larvicides, repellents, or fly traps.

Prevention is the best approach to managing fly strike in cattle. An effective prevention strategy combines environmental cleanliness, regular inspection, and the use of veterinary-approved products. Here’s how to keep flies off cattle and reduce the risk of fly strike:

Maintaining a clean environment is essential to reducing fly populations. Remove manure frequently and dispose of it away from areas where cattle graze or rest. Additionally, eliminate standing water and muddy patches; they provide ideal breeding sites for flies. You can also introduce fly control tools like traps or parasitic wasps to help limit fly numbers naturally.

Keeping your cattle clean and dry makes them less appealing to flies. Regular grooming, especially trimming long or matted hair around the tail and hindquarters, helps reduce the risk of infestation. Clip and frequently examine dirty areas for signs of skin irritation, injury, or moisture buildup.

Any wound, even a small one, can quickly attract flies. For this reason, you should clean and treat all cuts and abrasions as soon as you notice them. Vetericyn® Antimicrobial Utility Spray allows you to safely and effectively clean your animals’ wounds, setting the stage for faster healing. For larger wounds, consider protective coverings to keep flies off and daily monitoring of the healing process.

During high-risk seasons, fly control products must be regularly applied. Pour-in treatments or sprays are useful in repelling flies, while placing back rubbers or dust bags in areas where cattle gather can provide additional protection. It’s also a good idea to consult with your veterinarian to select the best insecticides or larvicides based on your local fly resistance patterns.

As mentioned, certain animals, like freshly castrated calves and dehorned cattle, need extra attention. You’ll want to check these animals multiple times a day during peak fly season to ensure they’re staying clean and comfortable. If you notice early signs of fly strike, quick action is crucial. Isolate the affected animal to prevent further spread throughout your herd and start treatment right away (more on this below).

Whenever possible, schedule high-risk procedures like castration, dehorning, or tagging during cooler months when flies are less active. If these procedures must take place during summer or early fall, you can use fly tags to deter flies from landing on cattle, offering ongoing protection during these most vulnerable periods.

If one of your cows becomes infested, immediate intervention is necessary. Here’s how to treat fly strike in cows effectively:

1. Restrain the animal safely – Use proper handling techniques to secure the animal for a thorough inspection.
2. Clip and clean the affected area – Shave or clip away matted hair to expose the wound and maggots. Gently cleanse the area using an antimicrobial wound wash.
3. Remove maggots – Use sterile forceps or a blunt instrument to remove all visible maggots. This step is crucial, as maggots will continue to cause damage if left behind.
4. Apply a topical treatment – Apply an antimicrobial gel to further disinfect and protect the wound. Vetericyn® Antimicrobial Utility Gel offers a powerful yet non-toxic formula that adheres to the wound site, provides a protective barrier, and promotes healthy tissue. In cases where maggots are found near the eye, a pink eye spray may be used alongside gel-based solutions for additional ocular protection.
5. Monitor and reapply – Inspect the area daily, reapplying treatment and watching for signs of reinfestation or infection.

In severe cases, your veterinarian may recommend injectable antibiotics or anti-inflammatory medications to support the animal’s recovery.

While you can manage mild cases of fly strike in cattle at home with prompt action, more serious or widespread infestations require veterinary intervention. Call your vet if you observe any of the following:

• Poor response to home treatment
• Signs of systemic illness (fever or listlessness)
• Deep or necrotic wounds
• Maggots near the eyes, ears, or genitals

Early vet involvement can be the difference between successful recovery and costly complications.

Though fly strike is most common in the summer, prevention efforts should span all seasons. Late fall cleanup, winter wound management, and spring parasite control all help reduce the risk before fly season peaks. A fly strike cow suffers physically and can quickly become a source of infestation for others. That’s why maintaining a clean environment, using fly control products proactively, and keeping an eye on your herd’s health throughout the year is so important.

Fly strike in cattle is a painful condition that can compromise animal welfare, reduce productivity, and result in veterinary intervention or even loss of life. Fortunately, with the right knowledge and a proactive approach, fly strike doesn’t have to be an issue for your herd. When it comes to preventing fly strike in cattle and managing wounds safely, Vetericyn offers a line of trusted, vet-recommended livestock care solutions. By prioritizing prevention, you’re not just safeguarding your animals—you’re also strengthening your operation and improving your herd’s overall resilience. Set your livestock up for long-term health and success with Vetericyn.