Rabbit Wellness 101: Understanding the Most Common Diseases Affecting Bunnies

Disease Rating

Mild these diseases are mild and can be treated easily.

Danger these diseases lead to complications.

Severe if not treated properly these diseases can end up fatal.

Fatal if contracted there is no cure for these diseases.

Breeds of rabbits the disease mainly affects

Ear Disease

Ear disease is common in rabbits. Vets find it a difficult condition to treat because there are not many licensed medications available.

Ear disease usually occurs more frequently in lop-eared rabbits because they cannot clean their ears properly. They have been selectively bred to have stenotic vertical ear canals which have a fold to enable the lop-eared look. This ear deformation causes cerumen build-up in the ear canals and ultimately causes ear disease.

Regular routine ear cleaning with a rabbit safe product can help reduce cerumen and should be a must in all lop breeds.

Signs of ear disease

• Ear scratching
• Head shaking
• gut stasis
• vestibular signs (head tilt, torticollis, nystagmus, ataxia, circling)

Otitis externa

Commonly caused by ear mites Psoroptes cuniculi, and leaves a crusty matter in the ear canal that extends into the pinna.

Otitis media

Otitis media is middle ear inflammation mainly caused by Pasteurella multocida, and the rabbit will be lethargic, be in pain, not want to eat and have gut stasis.

Otitis interna

Frequently occurs with Otitis media and rabbits will show vestibular signs like head tilt, which shows there is an issue in the inner ear. This can progress into other neurological signs, including severe nerve paralysis and Horner’s syndrome may occur.

Treatment

Sometimes treatment can be difficult because the underlying cause must be worked out and dealt with first.

Otitis externa is usually caused by ear mites, and the tick crust should not be removed because it can be panful and disfigure the ears. Rabbits should be treated with a licensed product that contains ivermectin.

Otitis media and otitis interna are usually connected, and the treatment options are difficult because of the lack of licensed products available.

Prevention

Using selamectin to kill ear mites before they settle in is beneficial for all rabbits.

Lop-eared rabbits must have their ears cleaned with a rabbit-safe product regularly.

Prevention is better than cure.

Coccidiosis

Coccidiosis is the infection caused by coccicia, is a very common worldwide parasitic disease of rabbits. It is transmitted through contaminated food or water, where the rabbit ingests the sporulated oocysts. The single-celled organism invades the mucosa in the intestine, liver and colon. There are around 12 species of coccician that can affect rabbits, and a rabbit can be infected by one or multiple species at the same time.

Oocyst is a hard, thick-walled cyst containing the zygote form of a parasite.

Sporulation is the non-infective coccidian oocysts that grow into mature, infectious forms. The time and way that sporulation occurs changes among the different coccidian parasites.

Coccidiosis is not zoonotic, which means it cannot transfer to humans. However, it can be found in infected dogs, cats, birds, chickens, cattle, goats, rabbits, mice, rats, guinea pigs, and many more animals humans live with.

The particular genus of coccidosis that rabbits can be infected with is called Eimeria. It is the same species of parasite that also affects guinea pigs, chickens, cattle, sheep, goats, and other domestic mammals. That means, rabbits might be able to contract the disease from these animals.

Eimeria

Eimeria is a genus of apicomplexan parasites which can cause coccidiosis in farm and small animals.

Apicomplexan parasites have a unique form of organelle that does not need to photosynthesise and it has spiral structures on the tapered (apical) end. Most apicomplexans are single-celled, spore-forming, and parasitic.

It is considered to be monoxenus because the parasite can complete its entire life cycle in a single host. It is also stenoxenous because the parasites tend to live in a single host, although exceptions have been identified.

Eimeria affects the following animals:

Contraction

Rabbits get coccicia from the environment, usually in places where many rabbits are kept in small confines, like in shelters and breeding establishments, where the rabbits are kept in commercial runs.

Rabbits can become infected by eating contaminated grasses, or young rabbits become infected by eating their infected parent’s or another infected rabbit’s feces.

Life Cycle

Eimeria has an exogenous phase, when oocysts are excreted into the environment. It also has an endogenous phase where the ingested parasite grows in the hosts intestine. While in the endogenus phase, several rounds of asexual reproduction occurs and the gametes differentiate into male and female, and fertilisation occurs.

Parasites are passed out of the hosts body through feces and tissue, and ingested when other animals eat the flesh or the feces, or food that has been placed on the feces and the animals eat it from the ground. It usually happens when animals are kept in a dirty, messy, small space.

An infected host will release oocysts into the environment in their unsporulated form. They contain a multi-layered cell wall which makes them highly resistent to environmenatal pressures. Once released, the unsporulated oocysts start meiosis when in contact with oxygen and moisture. This is called sporulation, and takes between 2-7 days to become infectious.

The sporulated oocyst is thought to be tetrasporic, which means it carries 4 sporocysts.

Once ingested, the oocysts start changing through excystation, where thousands of sporozites are released into the lumen of the intestine. Some species of Eimeria will bury into the walls of the intestine to develop further.

Visible Symptoms

In a nutshell:

• soft, sausage-like poops
• lethargy (lack of energy)
• weakness
• not eating/lack of appetite
• weight loss
• dehydration/not drinking

Rabbits bred in small, unclean areas, are most likely to have coccidiosis. It is noticable when young don’t grow very well, or die unexpectedly. Young rabbits are the most susceptible.

Eimeria infection in rabbits is usally noticable with lack of appetite, weight loss, dehydration and diarrhoea. Other signs are lethargy, depression, ascites, jaundice and reduced grooming behaviour.

Diarrhoea may be bloody due to the intestinal epithelium dying off when a large number of oocysts and merozoites burst out of the cells.

Severity depends on how many Eimeria oocysts were ingested. In minimal infections, gut damage might be repaired once the parasite has been irradicated. More severe infections, when the intestine epithelial layer has been irreprably damaged, will cause the release of blood, fluid and electrolytes into the intestine.

Some rabbits will have a rough coat.

Infected young rabbits are underweight and have a pot-bellied appearance.

Once severely infected, rabbits will usually die within a month.

Usually, rabbits only get a mild infection, and no signs will be seen. Although, intestional leisions will be created.

Diagnosis

Fecal tests are conducted under the microscope to check if there are oocysts and coccicia eggs.

Hepatic (liver) coccidiosis results in bilary obstruction and an enlarged fibrotic liver.

Infection can be seen in the ileum and jejunum and can be diagnosed after death (post mortem) with intestinal mucosa scrapings.

Narcropsy (after-death autopsy)

Small yellowish-white nodules are found throughout the hepatic parenchyma. These leisions help predict how long the rabbit was infected. Early leisions have milky content; while older ones are more cheese-like.

Hepatic parenchyma are cells in the liver that perform the metabolic functions.

When the lesion is put under a microscope, it is possible to see the oocysts.

It is also possible to see the oocysts in feces; however, sometimes the oocysts can be mistaken for normal yeast (Cyniclomyces guttulatus) which is commonly seen in fecal examinations.

Prevention

• clean dry litter in the litter box
• clean water bowls
• clean food dishes
• no feces in food or water
• no eating off a dirty feces covered floor
• move the pen around the garden every 2-3 days
• Leave toys and items in the sun for a while

Make sure the living areas and equipment of your rabbits are clean, and they have dry hay and litter to toilet into. Disinfect areas regularly. Make sure you don’t have too many rabbits in a small area.

With outdoor pens, move it around so the rabbits aren’t on the same place for more than three days in a row. if that is difficult, tidy up the excretia left beind daily, and make sure the sun gets onto those places, as UV kills the unsporulated oocysts and disinfect the ground to destroy coccician eggs.

Elimination of fecal matter in food containers and in water bowls will help prevent the fecal-oral transmission.

Wire-bottomed hutches should be cleaned, brushed with a wire brush and disinfected frequently to remove feces. This helps break the life cycle of the protozoa.

Ammonia (10%) solution is lethal to oocysts and is the best choice to use to disinfect all of the rabbits equipment that has been exposed to fecal matter.

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Prevention

Treatment is difficult and dangerous, so it is recommened to prevent and control it, rather than want a cure.

Some forms of coccicia are resistent to the drugs. Also, the drugs can affect the meat if given to rabbits used for consumption.

Depending on the severity, the vet may hospitalise the rabbit and provide care until it is well enough to go home.

If the rabbit;s diarrhoea changes from moderate (mushy poops) to severe (runny poops) the rabbit will have a low chance of surviving, so it is important to see a rabbit-savvy vet when the symptoms first appear.

For mild infections, vets prescribe an oral medication called toltrazuril. It is usually givn for a course of 2 days, then repeated 5 days later. At the end of the treatment, a fecal sample is then retested to see if the infection is no longer shedding coccicia eggs.

For severe infections of E. stiedae, vets may provide Sulfaquinoxaline to be added to the rabbit’s drinking water, which helps prevent the signs of hepatic coccidiosis. It will not always prevent leisions. Sulfaquinoxaline may also be given in the feed for a period of time, but feed-grade sulfaquinoxaline can be difficult to get, liquid sulfaquinoxaline is more commonly used. To lower the count of fecal oocysts, vets may prescribe sulfadimethoxine. After the infection has been treated successfully, rabbits are generally immune to further infections.

Other methods of prevention are being explored, in vaccines, but it has to be a live attenuated vaccine. Which means the rabbit has to be injected with some live parasites to build up an immunity. This method has been developed since the 1950’s, but is not widely used and is defintiely not a popular choice.

Vaccinations have shown that it gives the rabbit life-long immunity with that particular Eimeria species, but it does not give cross-protection against other Eimeria species.

Rabbits are corophagic, which means they eat their own poops, which means they can reinfect themselves. It is extremely important to continually clean the rabbit’s area and litter box to eliminate reinfection.

Treatment will not be successful if the rabbit’s enclousures, pens, hutches, equipment, litter box, fabrics, toys, everything is not sanitised and disinfected properly and frequently throughout the treatment period and for a month after coccicia has been eliminated.

Horner Syndrome

Horner syndrome is rare in rabbits, but it is well known in other domestic pets, like cats and dogs.

It typically constricts the pupil (miosis) and droops the upper eyelid (ptsosis).

Horner syndrome is caused by an interruption to the nerve supply to the eye. The rabbit’s hindbrain is where the three-neuron pathway starts. The first (central) neuron starts at the hypothalamus and goes down the spinal cord. The second (preganglionic) neuron starts in the first 3 thoracic spinal cord segments and travels through the thorax and cervical region until it synapses at the cranial cervical ganglion. The third (postganglionic) neuron travels from the same ganglion through the middle ear and into the eye.

If the nerve is damaged at any point along the pathway, the rabbit will show signs of Horner syndrome. Middle ear disease is the most common cause.

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Signs of Horner syndrome

• drooping upper eyelid
• pupil is constricted, the affected pupil is smaller than the unaffected pupil
• the white of the eye is red
• enlarged third eyelid, covering part of the eye
• rabbit has been rubbing eye a lot and it has soreness around it
• gut stasis my occur due to the stress and pain

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Diagnosis

Your vet will suggest an MRI to scan the damaged nerve.

If the cause is middle-ear disease, the vet will suggest treating the pain.

If the cause is a tumor, cancer, cyst etc, the vet will know an appropriate treatment, which could be surgery on the middle ear, drainage options or medical management.

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Who described Horner syndrome?

The syndrome is named after a Swiss ophthalmologist, Johann Friedrich Horner, but he wasn’t the one who first found it.

Back in 1727, François Pourfour du Petit reported ptosis, miosis and enophthalmos after cutting the sympathetic nerve in dogs. Later, Edward Selleck Hare reported similar signs in a letter published in the London Medical Gazette in 1838.

French physiologist Claude Bernard, in 1852, experimented on rabbits, which ultimately led to the connection between the cervical sympathetic fibres and Horner syndrome. So, the French call it Bernard-Horner syndrome.

In 1864, Silas Weir Mitchell described similar issues when he got a gunshot wound to the neck. Later in 1869, Johann Friedrich Horner published a more thorough report about the syndrome which contained detailed descriptions.