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Pasteurella: A Ubiquitous Bacteria—Its Health Effects in Rabbits
Readers who are unfamiliar with Pasteurella may find some of the information contained in this article to be rather frightening—enough so that they may worry about their rabbit. I want to assure readers immediately that I have rabbits who are infected with Pasteurella, and they continue to be lively little beings. They hop around the house, eat and drink as normal, and are as inquisitive as the others!
Please keep in mind that the purpose of this article is to let you know what can happen to a rabbit, not what necessarily will. Having an understanding of Pasteurella can create the basis for positive action.
Pasteurella refers to a genus of various species of bacteria, some of which may be part of your rabbit’s normal flora. Concerns arise with Pasteurella multocida (P. multocida) because it can cause a variety of diseases (referred to generally as pasteurellosis). Although the bacteria can cause abscesses, it is best known in association with respiratory disorders.
While P. multocida can have far-reaching health affects, many rabbits have strong immune systems that fight and destroy the bacteria or at least keep it under control so it does not cause disease. In addition, not all strains of P. multocida have serious consequences, and many of the rabbits who exhibit signs of it live to old age. Furthermore, the fact that rabbits receive better veterinary care these days means that the bacterium is often dealt with in the early stage. There are ways to assist your rabbit in maintaining health, some of which are mentioned in this article.
Pasteurella multocida (P. multocida)
P. multocida affects various animals, including rabbits, domestic livestock, and poultry. United Kingdom veterinarian Dr. Anna Meredith, who has published extensively about rabbits and is Head of Exotic Animal Service at the University of Edinburgh, reports:
It is important to realize that signs indicative of Pasteurella may actually be caused by something else. For example, nasal discharge could result from other bacteria (such as Bordetella bronchiseptica) or it could be symptomatic of a dental problem. This underscores the importance of obtaining a diagnosis from a rabbit-knowledgeable vet.
Some rabbits may not exhibit any signs of P. multocida. In the Textbook of Rabbit Medicine, Dr. Frances Harcourt-Brown wrote, “In rabbits, P. multocida can reside in the nasal cavity without causing disease.”
Further clarification is provided by Dr. Meredith: “Many rabbits are sub-clinical carriers of Pasteurella. Development of clinical disease is usually triggered by stressors such as unhealthy diet, unclean living conditions, and illness from another cause.”
Dr. Thomas Donnelly reported in the article “Application of Laboratory Animal Immunoassays in Exotic Pet Practice”: “Housing, particularly air quality, is important; chemical injury to the respiratory mucosa through exposure to ammonia increases susceptibility of rabbits to P. multocida infection.” Other respiratory irritants include cigarette smoke, dust, mold (bedding, hay), perfumes, bleach, and cleaning solutions.
The above information emphasizes the importance of regular prevention practices, including feeding appropriate foods, keeping litter boxes and other living areas sanitary, and ensuring clean air.
Health Conditions Associated with P. multocida
Diseases related to the upper respiratory system—The most common disease associated with P. multocida is snuffles (rhinitis), an upper respiratory tract infection. Sneezing, coughing, discharge from the nostrils (clear to thick, white pus), and noisy breathing are signs of the disorder. While grooming, the nasal discharge may be transferred to the front paws and to the sinuses, eyes, and tear ducts (causing sinusitis, conjunctivitis, and dacryocystitis, respectively). It’s important to note again that there are other causes of respiratory illness.
Genital infections—Both male and female rabbits can host an infection, including orchitis (inflammation of the testes) and pyometra (uterine infection).
Inflammation of the ear—P. multocida can spread from the nasal passages to the middle ear via the eustachian tubes, causing otitis media—often signaled by the rabbit scratching the base of the ear. Even if the infection is eliminated from the nostrils, the ears may remain infected. Pus may form in the deep recesses of the ear and can result in vestibular disease, evidenced by neurological signs such as rolling, nystagmus (rapid, involuntary movements of the eyeball), or tilting of the head. [Note that though P. multocida may be associated with torticollis (wry neck or head tilt), Encephalitozoon cuniculi may also be the cause.] Another serious result of the ear infection can be the loss of muscular coordination (ataxia).
Unilateral facial paralysis, sometimes referred to as Bell’s palsy—If the infection impinges on the facial nerve on one side, the resulting muscle weakness may give the rabbit a rather distorted, slipped-on-one-side look. The condition seems more cosmetic than serious. Two of my rescued rabbits have Bell’s palsy and appear to have no difficulties associated with it.
Lower respiratory infection, including pneumonia—Fatigue, lethargy, or reluctance to move around may be signs of lower respiratory tract disease. Other signs are depression, anorexia, and weight loss. This is a very serious condition that can be fatal; sometimes a rabbit’s only sign may be a breathing problem. (One of my little rescues was infected with P. multocida, leading to pneumonia. The necropsy showed that one lung was completely abscessed and that the other had multiple lesions.)
Abscesses—This localized collection of pus (formed by disintegrating tissue surrounded by an inflamed area) can occur anywhere on or in the body. Although P. multocida is often the cause, many other organisms (e.g., Staphylococcus aureus) can also trigger the condition. In rabbits, the collection of pus is usually very thick and tumor-like (unlike abscesses in humans, dogs, and cats) and must generally be surgically removed. Facial abscesses are frequently associated with dental disease; however, P. multocida is not commonly found in dental abscesses.
Wounds—Because P. multocida is often present in the nasal cavity, licking and grooming can spread the bacteria to a wound, resulting in an abscess or sometimes in cellulitis (inflammation of subcutaneous or connective tissue). In the article “Pasteurella multocida Infection in Rabbits,” the late Dr. Barbara Deeb indicated that cellulitis “is more difficult to treat than an abscess, and antibiotic sensitivity testing becomes even more important.”
Bones—P. multocida can result in osteomyelitis (infection of the bone). For example, rabbits with severe rhinitis can have destruction of the small bones (turbinates) within the nasal cavity.
Bacteria in the blood (bacteremia)— Once the bacterium is established, the infection can spread to surrounding tissues and through the blood to other parts of the body, resulting in a generalized disease condition as well as abscesses in other organs of the body. The rabbit may develop fever and die suddenly. Bacteremia is most often associated with the more virulent strains of P. multocida.
A rabbit-savvy vet will perform diagnostics to determine the cause of illness. A faulty assumption that P. multocida is the cause of a disease could result in inappropriate treatment since something other than the bacterium could be causing the problem. Bacterial resistance to particular antibiotics is also a consideration to be addressed.
In addition to signs reported by the caregiver, the vet will take the bunny’s temperature, determine any weight loss, and note the texture and color of the mucous membranes and of any discharge. Dried pus (which may look like wax) may need to be removed from the ears. Listening to the heart and lungs will determine whether abnormal respiratory sounds are heard during inhalation or exhalation.
A definitive determination of cause cannot be made solely on the presenting signs of disease. The vet may recommend bacterial culture and bloodwork (CBC, chemistry, bacterial/viral disease screening), which can indicate problems such as liver or kidney disease, metabolic problems, infection or inflammation, anemia, or electrolyte imbalance. Radiography (X-rays), ultrasound, CT scans, or MRIs may also be used.
Culture and Sensitivity, PCR, and Serological Tests
A culture and sensitivity test can help a vet determine if the infectious agent is Pasteurella. However, there are difficulties with this test. Sedation will most likely be required, and it can be difficult (sometimes impossible) to obtain a bacteria sample. The bacteria may be far back into the nasal passage, sometimes resulting in a false negative. In addition, P. multocida does not survive well outside the host and may not grow in the lab; or if the culture is positive for the bacterium, it may not be possible to determine the strain. Despite these apparent drawbacks, a veterinarian experienced in treating rabbits will provide the best advice for your particular bunny.
Are there alternatives? Dr. Meredith discusses two additional tests:
Antibiotics are necessary for the treatment for P. multocida conditions. Ideally, the culture and sensitivity test will determine which to prescribe. Antibiotics that are effective against Pasteurella include enrofloxacin (Baytril®), trimethoprim sulfa, chloramphenicol, and penicillin G. Though there are no published reports of its use for pasteurellosis in rabbits, Dr. Meredith confirms that azithromycin has been successfully used to treat respiratory infections in rabbits.
In some cases, the antibiotic will rapidly clear the infection. In other cases, especially if the infection is chronic or deep-seated, antibiotics may be required for long-term use. A probiotic may also be prescribed to help maintain gut flora balance.
Additional treatments may include anti-inflammatory drugs, flushing of the nasolacrimal duct, nebulization therapy, ear and eye drops, administration of fluids, or surgery.
Some complementary treatments may also be helpful. Dr. Hillary Cook, a Virginia (USA) veterinarian certified in veterinary acupuncture and the use of traditional Chinese herbs, shares the following:
Corticosteroids are contraindicated for pasteurellosis. As of this writing, there is no vaccine available for prevention of the disease in rabbits.
Treatment at Home
Your vet will prescribe a home-care treatment plan. If your rabbit has chronic runny eye, warm compresses will help keep the skin from becoming inflamed. If the bunny is not eating or drinking as normal, interventions such as syringe-feeding and subcutaneous fluids will be necessary.
As adjuncts to the healthcare regimen, your vet may discuss the importance of appropriate diet, stress-free environment, and physical and mental stimulation. Also note and discuss with your vet any new symptoms, changes in behavior, or lumps on the body.
Transmission to Other Rabbits
It should be somewhat comforting to know that the contagion of pasteurellosis is a greater concern for rabbit colonies (some animal shelters and the breeding, laboratory, fur, and meat industries) than for our household rabbits. However, we may not know where our rabbit came from or the conditions in which he lived. For example, as Dr. Deeb pointed out, “Rabbits available at pet stores are not likely to be from Pasteurella-free colonies.”
Transmission of pasteurellosis from an infected rabbit is through direct contact with nasal secretions, including transmission through the air when the infected rabbit sneezes. The spread can also occur through licking open wounds; sharing water and food bowls, litter boxes, and toys; and carrying the bacteria on caregiver’s skin or clothing. The disease can be shared during mating (genital infections), and a mother rabbit can pass infection to her kits.
Each rabbit is unique, and it’s impossible to predict how a bunny will react to the presence of P. multocida. To paraphrase Dr. Meredith: some rabbits will resist infection, others will succumb; some rabbits will expel the bacterium, others will become carriers; some rabbits will develop a less serious chronic condition, others will suffer from acute disease.
When there is more than one group of rabbits in a home, keeping the groups separate may be recommended, especially if one group is predisposed to pasteurellosis. It’s been shown that a separation of as little as four feet can slow transmission. If possible, separating the groups into different areas of the house will be helpful. Remember that we, as caregivers, can spread the bacteria from one group to another.
Concern for Family Members
Caregivers naturally want to know if a disease—especially one as infectious as pasteurellosis—can be transmitted to other members of the family. Dr. Cook offered these thoughts:
Prevention and Disease Control
Considering the serious health conditions that can result from P. multocida, it is a relief that many rabbits carry the bacteria in their bodies but most are not sick. It’s important to put Pasteurella and all serious diseases into perspective. Yes, your bunny can become very ill from the bacteria. However, it’s more likely that a rabbit will suffer ill health due to poor diet and other stressors. Optimizing a rabbit’s health will enable his or her body to fight pathogens such as P. multocida as well as recover more rapidly from illness or injury.
Prevention begins with providing appropriate basic care, including proper diet; clean living spaces; and plenty of exercise, mental stimulation, and companionship. Keeping your rabbit happy and healthy translates into reduced stress and a stronger immune system. Here are some methods to support your rabbit’s immune system:
Caregivers should not lose heart if their rabbit is diagnosed with pasteurellosis; it’s possible for a rabbit to live a happy life with the condition. Because I generally take in only unadoptable bunnies, some are quite old and most arrive with health issues. I frequently remind myself that the quality of their life is what’s most important. Rabbits at my house live uncaged (unless there is a medical reason to do otherwise), making it easy for them to exhibit the joie de vivre that seems so inherent in their nature. When given the freedom to express themselves, they do!
One of my greatest joys is seeing a rabbit who previously knew only a caged existence suddenly realize what it is to have freedom. Prince Edouard was such a rabbit. When he arrived, his old body was emaciated and he was extremely ill with Pasteurella infection and abscesses. He’d been caged for so many years that he didn’t even react when the door to his condo was left open. I finally had to remove him from the abode—and after that, he reveled in freedom! Frail though he was, Prince Edouard would head down the hall; when he tired, he’d sleep wherever he landed. When he had to use the litter box, he’d make his way back to the condo and use the box, sometimes settling into the soft hay. Other times he’d hop back out and do his ungainly shuffle down the hall again. I was privileged to know and care for this very special French lop, and this article is written as a tribute to him.
Warm thanks to the vets who shared their expertise for this article.
A shortened version of this article was published in Issue 7, Fall/Winter 2008, of Bunny Mad ("The magazine for bunny mad people!"), a United Kingdom publication. www.bunnycreations.co.uk. Used with agreement by the publisher.