Biting and nuisance flies
The most common flies that affect rabbits include green bottles, house flies, face flies, stable flies, horn flies, horse flies and blow fly species. Some species, like blow flies, are attracted to moist decaying environments in which to lay their eggs. Other fly species such as face flies, flesh flies, screw worm flies and bot flies target living animal flesh, including drinking the tears of live animals, biting the animal for a blood meal, or reproducing by laying eggs under the animal’s skin.
Flies are insects that are characterised by a pair of wings. Their ability to fly gives them the ability to travel large distances in search for food or a suitable environment to reproduce.
Their keen sense of smell draws them to foodstuffs, decay, excrement and moisture, and these are frequently found around animals, this makes animals a prime target.
The fly’s extraordinary mobility makes infestation and disease transmission between animals a real concern.
One of the most common conditions resulting from fly infestation in rabbits is flystrike (a type of myiasis).
This condition begins when female flies are attracted to moist soiled fur where they lay eggs that hatch into voracious larvae (maggots). The larvae crawl and eat their way through the decaying excrement and broken down skin causing a rapidly expanding open wound that can be life-threatening.
Signs of flystrike include:
- moist matted fur
- hair loss
- reddened skin
- foul odour
- visible wounds
- the presence of eggs and larvae/maggots in the fur
The rabbit may act weak, depressed, lay on its side or have an abnormally hunched posture. It may have a reduced appetite, or be reluctant to move. In severe cases, it may even lose consciousness or experience seizures.
Treatment for fly strike involves physical removal of the larvae and soiled fur followed by careful wound care and attention to secondary infection and pain control. Treatment is not always successful in advanced cases where the wounds are large or deep.
To prevent flystrike it is essential that the rabbit has clean dry fur, especially during the warm summer months when flies are most active. It is imperative that the housing environment is free from excess moisture and that the area is regularly cleaned of faecal matter and soiled bedding. Screened enclosures can help prevent flies from entering the habitat. In addition, all rabbits should be checked each evening to ensure that the body, and especially the undercarriage and hind end is free from excess moisture and debris and that no eggs have been laid. Failure to do this can result in significant damage in just a few short hours as eggs hatch and larvae migrate over the body.
Rabbits most at risk of flystrike are those that are obese and unable to reach their hind end. It is important that the rabbit is able to reach its hind end to groom itself and to consume soft faecal pellets (caecotrophs) which are essential for digestive health. Lack of grooming can lead to fur becoming matted with debris and faecal matter. Additionally, failure to ingest caecotrophs can lead to poor health and diarrhoea, another leading cause for flystrike.
Good bodyweight and intestinal health in rabbits requires a high fibre diet. Rabbits should eat at least 80% quality grass or meadow hay (not alfalfa hay) supplemented with fresh dark green leafy vegetables and herbs and only about 5% high quality fresh rabbit pellets. Sweet vegetables and fruits should only be fed occasionally as a special treat as the high carbohydrates can negatively affect digestion.
Another type of myiasis is caused by parasitic flies that have larvae that burrow into the skin or tissue of the rabbit. The majority of these species belong to the Cuterebra family which are primarily found in North America.
Bot flies lay eggs in a variety of places including near open wounds or orifices. They can even lay in moist soil in an animal enclosure or on other insects to transmit the larvae to the host.
Once a larva is on a host, it can burrow under the skin where it will sit and develop using host tissue as a source of energy. Some of these larvae can travel to the respiratory or gastrointestinal tract, or into the eyes and nose.
Clinical signs of infestation can include swelling, pain, ulceration and discharge around the larval cyst with secondary bacterial and fungal infections being common. The wound can cause distress to the rabbit and in severe cases can cause depression, weakness and serious infection.
Treatment includes careful physical removal, followed by cleaning and treatment of the wound.
Prevention is difficult as the flies are attracted to the host, even in clean conditions, but screens can deter some. Regular daily inspections of the rabbit’s skin and fur can help detect problems before they become severe.
Flies can also transmit dangerous diseases; both viral haemorrhagic disease and myxomatosis are viruses that are spread by biting flies, and both diseases can prove fatal.
Clinical signs include swelling of the eyes, face and genital as well as blindness, difficulty eating, drinking and breathing.
Treatment for these diseases in not guaranteed with the majority of cases proving fatal, although early detection and intensive care can improve outcomes.
Prevention of fly transmitted viruses is relatively easy via vaccination.
Biting flies can still be a real nuisance to rabbits causing painful bites and wounds on the ears and face; screened enclosures can do wonders to help provide a safe and comfortable habitat.
It is also essential to provide a clean, dry enclosure for your rabbit which can decrease the incidence of attracting flies in the first place.