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.

Development of the skeleton and feathers of dusky parrots (Pionus fuscus) in relation to their behaviour.

A clutch of five dusky parrots (Pionus fuscus) was observed from hatching to fully grown. They were examined radiographically from 16 to 45 days of age, a few days before the cessation of bone growth, and the development of their feathers and their behaviour were also studied. It was observed that when growing birds were removed from the nest and placed singly on a flat surface they would stand up and walk about until restrained; normally these birds would move very little and lie in an intertwined huddle that supported their relatively weak growing skeletons. At 50 days old they would climb to the nest entrance, retreating if scared. From day 51 the parrots flapped their wings vigorously inside the nest box, and they emerged at 53 days old when nearly all their large feathers had finished growing. These findings may help to explain the high rate of juvenile osteodystrophy in hand-reared parrots; premature exercise could lead to pathological deformity of the long bones, especially the major weight-bearing bone, the tibiotarsus.

Prevalence of mycoplasmas in eggs from birds of prey using culture and a genus-specific mycoplasma polymerase chain reaction.

Mycoplasmas are commensals and pathogens of different avian species, especially poultry and passeriforms. The role of mycoplasmas in raptors has not yet been completely determined, and especially not the possibility of vertical transmission. Therefore 424 raptor eggs were examined for the occurrence of mycoplasmas using culture, and 155 of these eggs with a Mycoplasma genus-specific polymerase chain reaction (PCR) assay. This PCR was tested for its sensitivity and specificity, especially for use in a bird population of unknown mycoplasma status (prevalence and species). The size of the amplified PCR product was large (1013 base pairs) to enable use of the product for species differentiation by sequencing. Culture and PCR yielded only one positive result, in an egg of a Northern Goshawk (Accipiter gentilis). The isolate was identified as Mycoplasma lipofaciens using an immunobinding assay, as well as by sequencing part of its 16S rRNA gene.

Microsporidian infection in lovebirds (Agapornis spp.).

In a naturally occurring outbreak in which all clinically affected birds died, microsporidian infection was confirmed by histological examination and electron microscopy. The parasites were identified in the kidney, liver and small intestine. A severe nephropathy was accompanied in some cases by liver lesions. The inflammatory response in both tissues was minimal and none was observed in the intestine.