Flystrike in Rabbits Signs, Treatment, and Prevention

Meaning

Myiasis, flystrike or blow flystrike in rabbits a serious parasitic maggot infestation caused mainly by a female Lucilia sericata, the green bottle fly species. The Lucilia sericata belongs to the blowfly or Calliphoridae family. The other type of fly that has been blamed for myiasis is the Calliphora vomitoria (the bluebottle fly) that also belong to the Calliphoridae family. [1]

Meiosis is common during warm, humid weather, especially during the start of summer and these flies are attracted to the urine (ammonia-rich) smell, feces, damp fur or skin, and a rabbit’s gland scent (pheromones). [2] While prevalent in rabbits housed outdoors, indoor ones are not immune to the condition.

Once they find a favorable host, these blowflies often lay eggs around a host’s rear or bottoms, especially near the inguinal gland and tail fold because feces often accumulate on the tail base and perineum. They can also lay eggs in areas vulnerable to urine scalding such as on medial thighs, central abdominal, and perineal skin.

The eggs that blowflies lay on a rabbit’s skin or coat will hatch within hours into maggots (larvae) that will burrow into and feed on rabbit’s flesh once they have finished the external debris. Besides eating the rabbit’s flesh, the maggots release dangerous toxins.

Prognosis will depend on factors such as the size of the lesion formed and how early, this problem is noticed and tackled.  

Risk factors

Although myiasis can affect healthy animals, some of the things that may predispose a rabbit to develop myiasis include the following:

• Obesity and being overweight
• Dental problems, make bunnies unable to groom themselves properly
• Old rabbits, those arthritic or disabled as they cannot groom themselves well
• Rabbits that have wounds
• Rabbit bottom problems like urine scald or diarrhea from the diet or enteritis as well as cecotrophs that may stick to the rabbit’s bottom.
• Dirty, smelly and damp hutches
• Those in hot and humid areas
• Breeds with long coat including the angora rabbits
• Female with skin folds around the abdomen or large dewlaps - they both make grooming difficult.
• Those with cystic calculi, accumulation of sludge in the bladder or crystals as well as other bladder infection may be prone to this condition as their hind will often be wet.

Signs and symptoms

Since myasis is fatal, you need to check your rabbit’s bottom, at least twice a day, especially during summer seasons. Some of the common symptoms you may notice include:

• Presence of the blowfly or their visible eggs
• Seizures from nerve reactions – itchy skin, seizures [3] as well as a possibility of toxic shocks
• Expect your pet to be listless, quiet, and depressed. Lethargy is also possible
• Anorexia (reduced appetite) and change in eating and drinking habits
• Tail fold and perineum soiling
• Dehydration
• Loss of fur and skin erosion that may progress to necrosis
• Diarrhea
• Weight loss
• Presence of eggs or hutched maggots
• The fetid smell from their hutches
• Digging into a corner caused by pain. Some may grind their teeth and thump their hind feet.

Diagnosis and assessment

To detect the early attack by Lucilia sericata maggot, you should carefully check on areas around the tail fold and inguinal gland. The smaller size, a few millimeters in length makes them hard to notice in their initial stages.

Additionally, check for any clumped eggs on your bunny often on the coat including on their bottoms, ears, nose, mouth, eyes and so on.

Before the eggs hatch, symptoms displayed will be the predisposing ones such as digestive system disease, dental disease, and so on.

If you leave the larvae (maggots) until they reach their second and third stages, expect some considerable damages to your rabbit’s soft tissues and trauma. They may attack the musculature and get into the abdominal cavity.

Treatment and recovery

Should you recognize any of the symptoms indicating your rabbit has flystrike, do not begin cleaning him yourself, call your vet immediately. This condition should be considered a serious emergency.

As you wait for your vet, remove any visible maggots using a tweezer, avoid putting your bunny in water, and shave the affected area including any fur clogs that are wet.

Use a warm, damp towel can encourage maggot to come to the surface. However, some sources encourage rinsing rabbits in water [5]

What your vet may do

• After assessing the maggot damage, your vet may sedate your rabbit (using medications such as medetomidine and midazolam) and remove the second and third stage maggots, clean, and disinfect wounds using an antiseptic
• In severe cases, he or she may consider hospitalization, IV fluids (in case of dehydration until the pet can freely drink water again).
• The vet may also consider forced feeding to avoid the risk of hepatic lipidosis if your rabbit cannot eat. This will include syringe feeding with critical diets for herbivores such as Oxbow Animal Health Critical Care, and Lafeber’s EmerAid Herbivore for tube feeding cases.
• Give them analgesic medications including NSAIDs like meloxicam and carprofen or buprenorphine to relieve pain.
• Give them antibiotics such as Enrofloxacin and trimethoprim in case of secondary bacterial infections.
• Use products that will treat and prevent myasis by killing the larvae or affecting their growth and metamorphosis such as cyromazine, fipronil, permethrin and cypermethrin, nitenpyram, ivermectin and selamectin among others
• Finally, your vet will deal with treating the resultant wounds in cases where myiasis is severe.

There may be also extensive surgery in severe cases to remove tissues that have maggots.

Flystrike rabbit death and Euthanasia

Myiasis is a fatal condition as these maggots can “eat into your rabbit’s flesh within 24 hours, which can cause death in a very short time.” [6] This is why emergency treatment is often recommended.

In some instances, euthanasia may be recommended such as in the cases of moribund where rabbits are terminally injured and succumbed to the blowfly attack or there is extensive damage to the soft tissue including body cavities and so on.

How to prevent flystrike in rabbits

Daily checks

Always, check your rabbit’s bottom twice a day for any signs of maggots or eggs since the eggs hutch after as little as two hours [8]

A healthy diet and dental care

Provide your bunnies with a healthy diet to reduce instances of gastrointestinal upsets including diarrhea.

The diet should also have an unlimited amount of hay that will help not only improve gut health but dental health too. Overgrown teeth especially incisors, and molar spurs may make grooming very difficult. Therefore, ensure you regularly check them and provide the right diet to help wear them down as well as some chew toys. 

Be careful in case of a diet change as it can cause diarrhea or loose stool that might be stuck in your rabbit’s fur and attract these flies. Excessive veggies can trigger diarrhea.

Finally, avoid overfeeding your rabbits as this can trigger diarrhea and increase the chances of flystrike.

Proper hutch hygiene

Remove any wet or soiled rabbit bedding, keep the hutch dry and disinfect it at least once a week. Hutches should also be well ventilated.

Consider spraying hutches anti-fly sprays such as ‘Xenex’ [8], and others that have cypermethrin or permethrin. The F10 Germicidal Wound Spray that has insecticide may also help.

Physical barriers and fly killers

Install fly screens in your rabbit runs and hutches. Also, try the various methods of killing flies including fly stick papers, fly strips, zappers and fly traps.  

Preventive measures such as rearguard for rabbits

Discuss with your vet on various preventive measures to stop the possibility of myiasis occurring. For instance, you can use a rearguard which is applied to a rabbit using a sponge and it can prevent myiasis for over two months. This product will stop maggot maturation to the stages where they become dangerous.

Also, try flystrike sprays for rabbits such as Johnson's Vet Fly Strike Protector for Small Animals.

Use fly repellant including plants and herbs

Try dried pyrethrum flowers, balm, chamomile, hemp, lavender, mugwort, peppermint, nigella, pennyroyal, rue, rosemary, santalina, green oregano, shoo fly, basil, and so on. They will help repel flies. You can put their pots on top of the hutches, hang them on sides, and so on.

Help your rabbits groom

In case it is unable to groom well due to one or the other reason, you should help it and ensure it does not have any soiled fur. Consider keeping the fur around their bottoms short if they are vulnerable to being soiled.

Try external cleansers such as Nolvasan Otic solution that can be used on hindquarters. However, it is mainly used for making earwax lose. Instead, ChlorhexiDerm Flush may help for cleaning the urine-soaked bottom or urine scald. 

Finally, manage obesity in your rabbit, keep wounds clean and dry. Let any urinary problems and any other conditions that may cause motility and groom problems, including arthritis treated by your vet.