Infectious Diseases in Rabbits
There are four major infectious diseases seen in pet rabbits. Two serious diseases are caused by viruses rarely seen in indoor pets: myxomatosis and rabbit hemorrhagic disease. Because these diseases are viral, there are no effective treatments once the rabbit is infected.
Two other infectious diseases are encephalitozoonosis, caused by the microsporidian parasite Encephalitozoon cuniculi, and respiratory infection caused by the bacteria Pasteurella multocida. These two diseases are common in indoor pet rabbits. There is no sex predilection for any of these rabbit diseases.
This illness is caused by the myxoma virus, which is a member of the pox virus family. It is widely distributed in the wild rabbit population. The virus is spread through bites from mosquitoes, flies, fur mites, and fleas, so your rabbit can be infected with this disease, even if it never comes into direct contact with wild animals. Myxomatosis can also be acquired through injuries caused by contaminated thorns or thistles, or by direct contact with an infected rabbit.
It is found in North America (predominantly the west coast), South America, Europe, and Australia. Pet rabbits are more susceptible and more severely affected than wild rabbits, as wild rabbits have developed a better genetic resistance. Outdoor pet rabbits are at greater risk of getting this disease.
"Rabbits showing signs of myxomatosis should be seen by a veterinarian as soon as possible."
The incubation period is 1-3 days, and the first signs are development of puffy eyelids, purulent (pus- producing) conjunctivitis, and lethargy. Subcutaneous (under the skin) swelling extends around the eyes, ears, and genital region. Swelling can rapidly progress to skin hemorrhages, trouble breathing, decreased to no appetite, fever, and generalized skin tumors. Death is usually 1-2 weeks after infection, but occasionally animals survive, and signs will slowly regress over about three months. Rabbits showing signs of myxomatosis should be seen by a veterinarian as soon as possible. Treatment involves supportive care with fluids, syringe feeding, anti-inflammatory drugs, and pain relievers.
Vaccination may provide temporary protection, but a vaccine is not available in the United States. Pregnant animals should not be vaccinated, nor should rabbits less than six weeks old. Occasionally, vaccinated rabbits have a local reaction at the injection site, but compared with the lethal infection, this reaction is insignificant. Rabbits suspected of having myxomatosis should be quarantined as soon as possible. Examination by your rabbit’s veterinarian is critical.
If you live in an area where myxomatosis has been diagnosed, make sure you protect your rabbit against fleas, biting flies, and mosquitos. Do not let your rabbit go outside without using a veterinary recommended flea preventative. During mosquito season, keep your rabbit indoors or provide mosquito netting around its outdoor cage.
Rabbit hemorrhagic disease virus
Rabbit hemorrhagic disease (RHD), a calicivirus, is also called rabbit calicivirus (RCV) or viral hemorrhagic disease (VHD). This highly contagious disease is distributed almost worldwide. As of 2023, the RHD virus has been identified in rabbits’ deaths in over 32 states in the US. Incubation period is 3-5 days. Infected animals may die suddenly without any clinical signs or 3-9 days after showing signs.
The disease is transmitted by direct contact with infected rabbits, rabbit feces, urine or infected blood, rodents, and contaminated cages, dishes, and clothing. The virus can also transmit over short distances in moist air. Rabbits in close proximity to other rabbits (such as at breeders and rabbit shows) are at a greater risk. Rabbits that recover can become carriers of the virus and may shed virus for up to four weeks. The virus may remain stable in the environment for 3-7 months.
"Pet rabbits in areas where this disease is rampant should be vaccinated annually, or even as often as every six months."
Signs of infection include decreased to no appetite, fever, lethargy, and collapse. There may be convulsions and coma, difficulty breathing, or foaming at the mouth. The most significant symptom is bloody discharge from the nose, mouth, rectum, or urogenital region. Some animals survive this acute phase but die a few weeks later from liver failure.
Given the horrendous death experienced by affected rabbits, pet rabbits in areas where this disease is rampant should be vaccinated annually (or even as often as every six months). An RHDV vaccine has been available in Europe for several years and in the United States since 2022. Vaccines will not eradicate the disease but will reduce the number of deaths. Speak to your veterinarian about vaccine availability in your area and the risks and benefits of its use. New rabbits should be isolated from other rabbits for 30 days to minimize the risk of this infection.
Encephalitozoonosis (Encephalitozoon cuniculi infection)
Encephalitozoon cuniculi is a microscopic, spore-forming, unicellular parasite (microsporidium) that must live within a host’s cell to survive. It can affect rabbits, mice, hamsters, dogs, cats, guinea pigs, and humans. It is spread in rabbits from mother to offspring in the uterus and from rabbit to rabbit through infected urine.
It usually causes a latent condition in rabbits, so a recently infected rabbit will show no symptoms of disease. When signs develop, the affected rabbit may develop dense, white, pustular material (hypopyon) in one or both eyes, while others may develop a head tilt, or may show more severe signs, such as twitching eyes (nystagmus), lack of appetite, difficulty walking, uncontrollable rolling over in one direction, tremors, and/or seizures. Confirmation of the disease is done by testing the blood for antibodies to the parasite.
Treatment involves administration of anti-inflammatory and anti-parasitic drugs for several weeks, along with supportive care such as syringe feeding and motion sickness medication in cases where rolling occurs. There are currently no medications that are guaranteed to clear the infection, and many rabbits continue to show signs even after treatment.
Encephalitozoonosis has been described in a few human cases, but its significance is poorly understood. Very young, elderly, and immunocompromised people are most at risk. Individuals with poorly functioning immune systems should not have contact with infected rabbits.
Pasteurellosis (Pasteurella multocida infection)
Pasteurella multocida is a bacterial organism that commonly causes abscesses, respiratory infections, and chronic inflammatory disease in rabbits. It can infect the nasolacrimal (tear) ducts, eyes, ears, and nose, and can cause abscesses in tooth roots, bones (particularly the jaw), skin, tissues under the skin, and internal organs. This organism commonly causes an upper respiratory tract infection called snuffles. Snuffles occurs more frequently in young rabbits.
Many cases of snuffles are mild, involving slight ocular or nasal discharge and sneezing and, if caught early, can be effectively treated or managed. If left untreated, this infection can become severe and may be fatal. A swab for bacterial culture and antibiotic sensitivity testing can be taken from ocular or nasal discharge to help guide treatment. Treatment usually involves either oral or injectable antibiotics, given for a minimum of 2-4 weeks. In some cases, treatment can be required for months, depending on the response.
Certain oral antibiotics, especially oral penicillin, amoxicillin, and similar drugs, can be fatal to rabbits. These antibiotics upset the normal gastrointestinal bacteria, leading to overgrowth of toxin-producing bacteria, diarrhea, dehydration, and death. These antibiotics should never be used in rabbits. There are safe oral and injectable antibiotics prescribed by veterinarians to treat this infection in rabbits.
"Using medications without consultation and advice of your veterinarian may cause antibiotic resistance and will make further treatment less effective."
A permanent cure may be difficult in chronic cases. Eye drops and nose drops, as well as oral anti-inflammatory drugs, may be used in conjunction with other antibiotics, as prescribed by your veterinarian. Do not medicate your rabbit yourself. Using medications without consultation and advice of your veterinarian may cause antibiotic resistance and will make further treatment less effective.
Rabbits with abscesses in or under the skin, in the jaw, or in an internal organ require surgery to surgically open and flush or surgically remove the abscess. Abscesses in the middle ear (causing balance problems), eyeball (causing blindness), or in bones or major organs are often difficult to treat and may recur, even with surgery.
All rabbits carry a certain number of Pasteurella organisms in their nasal passages, but only some rabbits manifest disease, as a rabbit with a healthy immune system will generally keep the organisms in check. Stresses may trigger clinical signs. Stresses may include poor nutrition, change in diet, introduction of a new pet or person in the house, overcrowding, environmental stresses, immunosuppression, or the presence of other disease.
Many rabbits are chronically infected. The disease is easily transmitted between rabbits, through direct contact with infected rabbits’ nasal or ocular discharge, contact with pus from an abscess, or contaminated items such as bedding, food and water bowls. New rabbits should be isolated for about one month before being introduced to other pets. Even with successful treatment, relapses may occur if your rabbit is exposed to stressful situations. Get your rabbit checked annually by a veterinarian to keep them as healthy as possible and minimize problems with pasteurellosis.
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