Fly strike, also called flystrike or blowfly strike, is a condition where flies lay eggs on a living animal and the hatching maggots feed on the animal’s skin and flesh. It progresses rapidly, often within hours, and can be fatal. In pet rabbits, nearly 45% of confirmed cases end in death or euthanasia, making it one of the most serious warm-weather threats to small animals and livestock alike.
How Fly Strike Happens
Fly strike begins when certain species of blowflies or bottle flies are attracted to moisture, warmth, or odor on an animal’s body. The flies land and deposit eggs directly on the skin or in nearby fur and wool, typically in areas that are damp, soiled, or wounded. The eggs can hatch into maggots in as little as 12 hours under warm conditions.
Once hatched, the larvae begin feeding. Some species only feed on dead or decaying tissue in existing wounds, but others are far more destructive. Screwworm flies, for instance, are obligate parasites of living flesh, meaning their larvae actively burrow into healthy tissue. These maggots can migrate from the skin surface deeper into the body, causing extreme tissue damage as they go. In less aggressive species, feeding is still painful and dangerous because it creates open wounds that invite infection and attract more flies, compounding the problem quickly.
Which Animals Are Most at Risk
Sheep and rabbits are the animals most commonly affected, though fly strike can happen to dogs, cats, poultry, and other mammals. Any animal with a wound, soiled fur, or matted coat is vulnerable. In dogs, bite wounds are common initial infection sites, and in newborn puppies, the healing umbilical cord stump can attract egg-laying flies.
Several health conditions make an animal more susceptible:
- Diarrhea or loose stool that soils the fur around the hindquarters
- Dental problems that prevent grooming, especially in rabbits, leading to matted and soiled fur
- Obesity or arthritis that limits an animal’s ability to clean itself
- Open wounds or skin infections of any kind
- Urine scalding from incontinence or mobility issues
Rabbits deserve special attention because healthy rabbits are fastidious groomers. A dirty bottom on a rabbit is never normal. Rabbits also produce soft droppings called caecotrophs that they eat directly. If a rabbit can’t reach them (due to pain, obesity, or dental disease), these sticky droppings accumulate on the fur and create an ideal environment for flies.
Signs to Watch For
Fly strike can go from invisible to life-threatening in less than a day. Early signs are subtle: restlessness, loss of appetite, or a pet that seems unusually quiet or withdrawn. You might notice your animal straining, digging at its hindquarters, or sitting in an unusual posture.
As the infestation progresses, signs become more obvious. You may see visible maggots on the skin, a foul smell, or patches of wet, damaged skin. Affected animals typically develop rapid breathing, a drop in body temperature, and severe weakness. Left untreated, the toxins released by tissue destruction lead to shock and death, sometimes within 24 to 48 hours of the eggs being laid.
What Veterinary Treatment Looks Like
Treating fly strike is an emergency. The immediate priority is removing every maggot from the animal’s body. A veterinarian will clip away surrounding fur to fully expose the affected area, then carefully remove larvae and flush the wound with saline solution. This process can take significant time depending on how far the infestation has spread.
After the maggots are removed, the wound is assessed for depth and tissue damage. Many animals need pain relief, fluids to treat shock, and antibiotics to fight secondary infection. Severely affected animals, particularly rabbits, sometimes have damage too extensive to recover from, which is a major reason the fatality rate is so high.
Recovery depends on how early the condition was caught. Animals treated in the first few hours, before significant tissue loss, have a much better outlook than those found after maggots have been feeding for a full day or more.
Preventing Fly Strike
Prevention is far more effective than treatment. For pet rabbits and other small animals, the most important step is keeping their living area clean and checking them at least twice daily during warm months, paying close attention to their hindquarters. Any animal with loose stools, a dirty coat, or a wound needs immediate cleaning and monitoring.
For sheep, chemical preventatives applied to the fleece are the standard approach. Insect growth regulators are among the most widely used. These work by preventing fly larvae from developing through their normal growth stages. Applied as a spray or backline treatment after shearing, they can protect sheep for 11 to 24 weeks depending on the product and wool length. Other options include synthetic compounds that paralyze insect nervous systems, applied through jetting or dipping.
Timing matters. Protection should be in place before fly season peaks, typically during warm, humid weather from late spring through early autumn in temperate climates. A single application at shearing may not last the entire risk season, so some animals need a second treatment.
Some sheep farmers in the UK are now experimenting with a graduated approach: starting with plant-based repellents containing citronella or tea tree oil during low-risk periods, then escalating to chemical treatments only when fly pressure increases or animals are in a vulnerable state. This aligns with recent guidance from the British Veterinary Association encouraging targeted rather than blanket use of chemical parasite treatments.
Practical Steps for Pet Owners
If you keep rabbits, the single most effective thing you can do is check your rabbit’s rear end every day during fly season. Part the fur and look at the skin. Address any underlying condition that causes soiling, whether that’s a diet too low in hay (which causes soft droppings), dental disease, or joint pain that limits grooming. Fly screens on outdoor enclosures add a layer of protection but are not a substitute for daily checks.
For dogs, keep wounds clean and covered, and don’t let matted, feces-soiled fur persist, especially in long-coated breeds or older dogs with mobility problems. Any visible maggots on a pet warrant an immediate veterinary visit, not a wait-and-see approach. The speed of this condition is what makes it so dangerous: a small patch of eggs in the morning can become a critical infestation by evening.