Flystrike in Rabbits

Flystrike is a disease every rabbit owner should know about. Progressing rapidly, flystrike can make rabbits very unwell, and can even be fatal. Treatment is difficult so prevention is key. In this article, we will outline what flystrike is, how it is caused, how our vets go about treating it, and how you can prevent it in your rabbit.

What is Flystrike?

Flystrike, or myiasis, is a diseased caused by flies and their maggots. Flies (particularly green bottle flies) prefer to lay their eggs on damp, dirty, diseased or damaged skin. In rabbits, this commonly occurs around the rear end. The flies lay eggs which hatch in as little as 24 hours. The maggots that hatch out will then start to burrow into the tissue of the rabbit to feed. This causes intense pain and discomfort. If left untreated, secondary bacterial infections can spread in the bloodstream and lead to fatal sepsis.

What are the Risk Factors for Flystrike?

Any rabbit kept in any condition is at risk of flystrike, but certain factors make it more likely.

Since flies are often seasonal, incidents of flystrike tend to be more common in Spring and Summer. Different parts of the country, temperature and weather will also affect the number of flies, and thus the risk of flystrike. Due to being more exposed to flies and the environment, and sometimes because there is less monitoring by owners, outdoor bunnies can be more prone to flystrike, but indoor-only rabbits are not immune.

Most flystrike occurs around the rear end of rabbits, due to urine and faecal contamination. This can occur if a rabbit is kept in a dirty or infrequently cleaned environment, or due to disease. Common diseases that can cause urine scald include cystitis, urinary tract infections, bladder stones, and kidney disease. Conditions that can lead to faecal staining include parasitic or viral infections, poor diet, inappropriate use of antibiotics, and dental disease. Obesity, arthritis, gut stasis and other causes of pain can also cause dirtiness due to less self-grooming.

Other conditions, such as those that cause eye, ears or facial discharge, such as infections or dental disease, can lead to dirty fur and myiasis too. Overweight rabbits tend to have deep skin folds that can become wet and attractive to flies as well.

In almost all cases, the risk of flystrike is dramatically increased due to underlying factors which should be addressed. We would argue that flystrike is a preventable condition.

What Symptoms Does Flystrike Cause?

Flystrike progresses rapidly, with fly eggs hatching within hours of being laid – rabbits can become dangerously sick within 24 hours.

Once the maggots start to burrow into the skin, they cause painful open sores, wounds and inflammation. This can sometimes cause a foul smell too. Rabbits quickly become dehydrated due to blood and fluid loss, leading to lethargy, inappetence and depression. Some rabbits will hide or become withdrawn due to the pain, others may try to groom themselves – the latter can lead to further self-trauma.

In advanced stages, shock can start: your rabbit will become dull, limp or collapse. Their temperature may drop, and their ears and feet feel cold. Sudden death can occur at any time – this is a veterinary emergency, and your rabbit must see a vet immediately.

It is not always possible to see the maggots – when newly-hatched they are small, so don’t rely on this to identify flystrike.

Treatment of Flystrike

The success of the treatment of flystrike depends on how unwell the rabbit has become, how severe the tissue damage is, and other complicating factors. In severe cases, euthanasia may be the only kind option. This is often recommended if your rabbit is already starting to fade, if the maggots have entered the abdomen, if there are large areas of dying tissue, or if the damage is very deep. Large numbers of more mature maggots indicates that the flystrike has been ongoing for at least a day, and again may lead to euthanasia as the only reasonable option.

Stabilisation – Should treatment be recommended, our first priority will be to stabilise your rabbit – shock can quickly kill a bunny. This should start with inserting an intravenous catheter, commonly placed in the ear vein – this enables large volumes of warmed fluid to be given to your rabbit, to rapidly restore blood pressure and prevent further dehydration. Vets will commonly start with large volumes of fluid initially, then reduce this to lower levels once the rabbit is stable. Actively warming the rabbit can help with circulation too.

Feeding – In many cases, rabbits that become unwell go off their food. This can lead to dangerously low blood sugar, a condition called hepatic lipidosis, or gut stasis, all of which can be fatal. Ensuring they eat is critical, so many require intravenous sugar solutions, or oral syringe feeding until they will eat by themselves. Pro-motility drugs can also encourage appetite. Ensuring they have appropriate energy levels may take priority over dealing with the wounds.

Pain relief – Pain relief is also critical, as flystrike is intensely painful for rabbits. Strong opioid medications like buprenorphine are often given, with other drugs like meloxicam if there are no signs of kidney damage or severe dehydration.  Local anaesthetics applied over wounds can provide pain relief too. In some cases, vets may want to use drugs like ketamine or midazolam as part of a sedation or general anaesthetic to better stabilise and treat the rabbit.

Antibiotics – Due to contamination, most flystrike wounds will become infected with bacteria. Thus, most rabbits will be given antibiotics to protect them. This will often start intravenously or via injection at first, then progress to oral once the rabbit is well enough to go home. Ideally, antibiotic choice should be based on culturing the bacteria from a swab of the wound, but this takes time and is not always possible.

Cleaning the wounds – Once a rabbit is stable and has sufficient pain relief and nutrition, managing the wounds can begin. Initially, as many fly larvae as possible should be removed, to prevent further damage. This can be done using forceps, or flushing them away using sterile saline. Any visible eggs should be carefully brushed out using a comb too. It is important that the rabbit be given anti-parasitic drugs now, to prevent further hatching of remaining eggs. The wound should then be cleaned to remove gross contamination, such as urine and faeces. Any dead necrotic tissue can be removed with a scalpel blade. Antiseptics, like iodine solutions, will help kill bacteria and any remaining maggots. When the wound is clean, gel or fabric dressings will be applied to protect the wounds and provide the right environment for healing. Wounds can take weeks to heal, so repeated dressing changes and examinations will be needed.  Some rabbits will need to stay in hospital for a period too, until they are well enough to go home.

Prevention of Flystrike

Preventing flystrike is imperative, given how difficult treatment can be and how much suffering the condition can bring. There are a number of things every rabbit owner should do to reduce the risk of flystrike.

Check – First you should check your rabbit at least twice a day, particularly their back end, looking for signs of flystrike or any soiling. Remember flies are attracted to dirty skin, so make sure any dirtiness is promptly addressed. Check their environment too, spot cleaning dirty litter daily and replacing it roughly every week. You may want to check your rabbit more frequently in summer, if they have any underlying disease, or any wounds. If you notice your rabbit starting to soil itself, please take them to the vet as it is likely a sign of underlying disease like those listed above. Larger environments spread messiness out and reduce build-up, so large hutches or runs are ideal.

Repel flies – All rabbits should be treated during the Spring and Summer with a topical fly repellent. Products containing cyromazine are some of the few licensed drugs for this purpose. Applied down your rabbit’s back, it protects them for up to 10 weeks from flies. They will not be completely immune however, so other management is still important. You can further reduce the incidence of flies by removing any rotting food, rubbish, or poo in the nearby environment.

Grooming – Some rabbits should receive extra care, such as those with naturally long hair like Angora rabbits. These rabbits struggle to groom themselves adequately, leaving the fur prone to dirtiness and flystrike. Any rabbits like these should be groomed daily, any matting carefully clipped away, and their rear ends washed if dirty. Any rabbit that is overweight or arthritic may also not groom themselves enough, and need human intervention – in these cases, please bring your rabbit to the vet for assistance in managing these conditions.

Good health – Prevention of underlying disease is important too, such as the arthritis or obesity mentioned above. Diet and exercise are big factors, so ensuring these are appropriate is important. This will also help prevent dental disease, gastrointestinal disorders and eye disease that can also lead to flystrike. You should visit your vet at least once a year for their annual vaccinations, although all our members receive a vet check every 6 months – this can help identify any underlying disease that might predispose them to flystrike