RHDV2 epidemic in UK pet rabbits. Part 2: PCR results and correlation with vaccination status.

OBJECTIVE: To report PCR results and vaccination status of rabbits with rabbit haemorrhagic disease following an investigation into sudden or unexpected death. MATERIALS AND METHODS: PCR testing for RHDV2 and RHDV1 was performed on rabbit liver samples at two laboratories. Laboratory A reported results as positive or negative; Laboratory B reported results quantitatively as RNA copies per mg liver, categorised as negative, inconclusive or positive. The vaccination status of rabbits with both histopathological features of rabbit haemorrhagic disease and positive PCR test results were collated. RESULTS: PCR results matched histopathological findings in 188 of 195 (96%) cases. Seven individuals showed equivocal results, all of which had histopathological features of RHD but three tested PCR-negative and four results conflicted between laboratories. RHDV2 was the serotype detected in all PCR-positive cases. Histological features of rabbit haemorrhagic disease and PCR test results were positive in 125 rabbits; 51 unvaccinated, 56 in-date with Nobivac Myxo-RHD and 13 vaccinated against RHDV2 - although nine of these were vaccinated within 10 days of death. CLINICAL SIGNIFICANCE: PCR testing complements histopathology in cases of sudden death in rabbits by confirming the diagnosis and identifying virus serotype, but there can be false negatives. Although RHDV2 is currently prevalent in UK pet rabbits, vaccination against both RHDV1 and RHDV2 is recommended. Failures of RHDV2 vaccine are infrequent.

RHDV2 epidemic in UK pet rabbits. Part 1: clinical features, gross post mortem and histopathological findings.

OBJECTIVES: To report clinical features, gross post mortem and histopathological findings from an investigation into sudden or unexpected death in rabbits that was undertaken during an outbreak of rabbit haemorrhagic disease. MATERIALS AND METHODS: Using a standard protocol, veterinarians were invited to submit case histories and results of their post mortem examination of pet rabbits that died unexpectedly. Histopathological examination of heart, lungs, liver, spleen and kidney samples was collated with macroscopic appearance and clinical details. RESULTS: Hepatocellular necrosis, characteristic of rabbit haemorrhagic disease, was observed in 185 of 300 (62%) submissions, often accompanied by glomerular thrombosis and changes in other organs. Evidence of rabbit haemorrhagic disease was not apparent on histopathology in 113 of 300 (38%) rabbits. Gross post mortem examination by veterinary practitioners did not always reflect reported histopathological changes. No macroscopic abnormalities were seen in 78/185 (42%) of rabbit haemorrhagic disease cases. Rapid death and death of other rabbits in the household were common features of rabbit haemorrhagic disease. Ante mortem clinical signs included anorexia, collapse, lethargy, seizures, icterus, bleeding from the mouth, dyspnoea, hypothermia, pyrexia, bradycardia or poor blood clotting. CLINICAL IMPORTANCE: Rabbit haemorrhagic disease can be suspected from a history of sudden death, especially if multiple rabbits are affected. There is not always macroscopic evidence of the disease but histopathology is useful to support or refute a diagnosis of rabbit haemorrhagic disease and provide information about other causes of death.

Health survey of 167 pet rabbits (Oryctolagus cuniculus) in Finland.

Only a limited amount of information is available about health status of pet rabbits. The aim of this study was to obtain data about the health status of pet rabbits considered healthy by the owners in Finland. Physical examination and lateral abdominal and lateral skull radiography were performed on 167 pet rabbits of which 118 (70.7 per cent) had abnormal findings in at least one examination. The most common findings were acquired dental disease (n=67, 40.1 per cent), vertebral column deformities and degenerative lesions (n=52, 31.1 per cent), skin disorders (n=28, 16.8 per cent) and eye disorders (n=12, 7.2 per cent). Vertebral column angulating deformities were significantly more common in dwarf lop rabbits (P≤0.001). The prevalence of health disorders was significantly higher in rabbits over three years of age of which 51 (82.3 per cent) had findings in at least one examination (P<0.05). Rabbits as prey animals hide their illness, which cause difficulties to owners to recognise health problems. Because of the high prevalence of clinical and radiological findings in apparently healthy pet rabbits, regular physical examinations are advised, especially for animals over three years old.

Clinical value of blood glucose measurement in pet rabbits.

Blood glucose was measured with a portable glucose meter in 907 rabbits, including 238 clinically healthy ones. Blood glucose concentrations ranged from 1.2 to 30.1 mmol/l. Diabetes mellitus was not encountered. No significant effect of sex or sedation was found. Hypoglycaemia was seen in 16 rabbits including one with an insulinoma. There was a significant relationship between blood glucose, food intake, signs of stress and severity of clinical disease. Rabbits showing signs of stress had higher blood glucose than rabbits with no signs and rabbits that were totally anorexic had higher blood glucose values than those that were eating normally or those with reduced food intake. Severe hyperglycaemia (>20 mmol/l) was associated with conditions with a poor prognosis. Rabbits with confirmed intestinal obstruction had a mean blood glucose of 24.7 mmol/l (n=18). This was significantly higher than the rabbits with confirmed gut stasis, which had a mean value of 8.5 mmol/l (n=51). The conclusion of the study was that blood glucose is a measurable parameter that can be used to assess the severity of a rabbit's condition and help to differentiate between gut stasis and intestinal obstruction in rabbits that are anorexic.

Gastric dilation and intestinal obstruction in 76 rabbits.

Eighty-four incidents of gastric dilation (bloat) were investigated in 76 pet rabbits, and an intestinal obstruction was confirmed in 64 of them. In 49 the obstruction was due to pellets of compressed hair, in four to locust bean seeds, in five to neoplasia, in two to postspay adhesions, and in one case each to carpet fibre, tapeworm cysts, a strangulated hernia and diverticulosis. In all but four cases, the obstruction was in the small intestine. The condition affected a variety of breeds fed on a variety of diets. Radiography was a useful diagnostic tool because gas and/or fluid in the digestive tract outlined the dilated stomach and intestines. Twenty-nine of the rabbits died or were euthanased without treatment, and 40 underwent exploratory surgery; of these, 10 died during surgery, three were euthanased because of intestinal neoplasia, eight died postoperatively and 19 recovered. Fifteen rabbits in which radiography indicated that a foreign body had passed out of the small intestine did not undergo surgery; of these, 13 recovered and two died.

Encephalitozoon cuniculi in pet rabbits.

The results of a serological test for Encephalitozoon cuniculi in 125 pet rabbits are reviewed, together with follow-up studies of clinical cases. Blood samples were taken from 38 asymptomatic rabbits and 87 rabbits showing neurological, renal or ocular signs suggestive of encephalitozoonosis. In the asymptomatic group, six of 26 (23 per cent) apparently healthy rabbits, sampled as part of a health screen, were seropositive; of the remaining 12 asymptomatic rabbits, sampled because they lived with seropositive companions, eight (66 per cent) were seropositive. Fifty-eight of the rabbits with clinical disease showed neurological signs, including head tilt, seizures, ataxia and swaying; three of them also showed renal signs and two showed ocular signs, and these five rabbits were all seropositive. Head tilt was the most common neurological sign in 21 of 23 (91 per cent) of the seropositive cases. All nine rabbits with ocular lesions were seropositive. In follow-up studies of clinical cases, the rabbits showed variable responses to treatment with albendazole, fenbendazole, antibiotics or corticosteroids, and some cases recovered without treatment.

Parathyroid hormone, haematological and biochemical parameters in relation to dental disease and husbandry in rabbits.

During a two-year period between 1995 and 1997, over 80 blood samples were collected from pet rabbits in order to investigate an apparent osteodystrophy affecting the skulls of rabbits with acquired dental disease. A series of haematological and biochemical analyses relating to calcium metabolism were performed and samples were taken for parathyroid hormone (PTH) assay. The rabbits were categorised according to the condition of their teeth and the manner in which the pets were kept. PTH concentrations were higher and calcium concentrations lower in hutch-kept rabbits with advanced dental disease in comparison with those kept in free-range conditions. No dental problems were detected in the free-range rabbits on radiological or clinical examination. During the course of the study, differences in haematological pictures and albumin values emerged among rabbits kept under the different husbandry regimes. Complete blood counts from free-range rabbits were comparable with laboratory reference ranges, whereas there were significantly lower red cell and lymphocyte counts in rabbits exhibiting advanced dental disease. Serum albumin values were significantly higher in rabbits kept in free-range conditions than in those with advanced dental disease or those unaffected by dental disease but kept in hutches. Rabbits kept in hutches showed trends towards anaemia and lymphopenia. Results indicated that acquired dental disease of pet rabbits is related to husbandry and is associated with alterations in calcium metabolism.

Preliminary investigation of the vitamin D status of pet rabbits.

The plasma concentrations of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) (vitamin D3) were measured in blood samples taken from one wild rabbit and 13 pet rabbits at different times of the year. Some pet rabbits had low or undetectable plasma concentrations of 1,25-(OH)2D3 especially if they were kept in hutches. Rabbits with more access to sunlight had higher concentrations of 1,25-(OH)2D3.

Calcium deficiency, diet and dental disease in pet rabbits.

Poor calcification of the teeth and the bones of the skull predisposes pet rabbits to dental disease. This study is a preliminary investigation into the dietary habits of pet rabbits. Owners were questioned about the feeding preferences of their pets. Manufacturers of rabbit foods were asked about the calcium, phosphorus and vitamin D content of their foods and how they had decided upon the formulation of their rations. Samples of rabbit food were analysed for calcium and phosphorus. Rabbits were found to be selective feeders. Rabbit food from pet shops consists of a mixed ration, of which the most commonly rejected ingredients were pellets and whole grain. The food manufacturers reported that calcium, phosphorus and vitamin D supplements are incorporated into the pellets. Food analyses demonstrated that rejection of the pellets and whole grain from the food can reduce a rabbit's calcium intake to below the minimum dietary requirement. The rabbit's unusual calcium metabolism is discussed. Calcium deficiency may cause osteomalacia but dietary excess may cause urolithiasis. Vitamin D deficiency may also exacerbate calcium deficiency. Recommendations are made for preventing calcium deficiency and dental disease in rabbits.

A review of clinical conditions in pet rabbits associated with their teeth.

Pet rabbits are frequently treated by veterinary surgeons but most of the literature is based on diseases encountered in laboratory or commercial rabbits. Many pet rabbits suffer from dental abnormalities and 40 clinical cases of diseases associated with teeth problems are reviewed. The clinical and radiological examination of the oral cavity of conscious and anaesthetised rabbits is described and the treatment of dental disorders is discussed. Post mortem studies of 20 of the skulls revealed bone of poor quality. Deformed teeth with little or no enamel were found during clinical examination and post mortem. The poor quality of the teeth and bone was not related to malocclusion. Distorted growth of the crowns led to lacerations to the tongue or inside the cheek, causing anorexia, weight loss and problems with grooming. Distorted growth of the roots resulted in penetration of the weakened bones of the maxillae, mandibles and orbits. Osteomyelitis, abscess formation or infections of the lacrimal duct or nasal cavity were a result of this disease process. The cause of the defective teeth and poor bone quality was not determined but preventative measures are proposed.