Canine circovirus was first detected in canine blood samples in the USA in 2012/2013 and was described in a dog with necrotising vasculitis and granulomatous lymphadenitis. In a subsequent study, it was mainly found in faecal samples from dogs with diarrhoea. In 2014, it was detected in Italy and in 2015 in Germany as well. Circoviruses can also be found in healthy dogs; further studies will be necessary to clarify questions on the pathogenesis and epidemiology.
Dog circovirus should be considered in the differential diagnosis in case of diarrhoea/vomiting, fatigue, hepatic diseases, haemorrhage and vasculitis. Co-infections with other, mainly enteropathogenic agents are frequently observed. Similarly, an infection with canine circovirus can further complicate other infectious diseases.
Psittacine Beak and Feather Disease (PBFD)
PBFD is characterised by an impaired growth of the beak, the feathers and the claws. The disease is globally distributed; more than 40 species of macaws, agapornis, grey parrots, amazons and parakeets are affected.
Nestlings mostly die peracutely, while the course of the disease is acute in fledglings. Animals show clinical signs of lethargy, loss of appetite as well as vomiting and/or diarrhoea. Death is possible within 1 – 2 weeks. Changes in the developing feathers are pathognomonic – but usually only visible in chronic forms. Symmetric feather loss occurs or the feathers get stuck in the shaft and will then break off. Lesions on the beak and, rarely, on the claws will only occur later on.
Transmission of the virus mainly takes place horizontally. The virus is spread with the faeces, the shedding of developing feathers and with the crop content of feeding parent birds. Thus, nestlings can be infected very early on. Vertical transmission is also possible, but of secondary importance. Here, hatching birds are infected through egg shells that are contaminated with circoviruses.
Pigeon Circovirus (PiCV)
Circovirus infections mainly occur in pigeons aged 6 weeks to 12 months (young pigeon disease syndrome). The clinical picture is non-specific; signs include lethargy, anorexia, diarrhoea, wasting and PBFD-like changes in the feathers. The disease is accompanied by immune suppression, and organ alterations occur, particularly in the central immune system and the spleen. In addition to the clinically manifest form especially in young pigeons, there is also a high number of subclinically or persistently infected animals.
Porcine Circovirus 2 (PCV-2)
Porcine circovirus type 2 (PCV-2) is associated with the so-called post weaning multisystemic wasting syndrome (PMWS). PMWS is usually observed in weaners and less frequently in suckling piglets. Affected animals show a progredient loss of weight as well as respiratory disorders with coughing, which are often complicated by secondary bacterial infections. PCV-2 can be detected in the tissue of infected piglets by means of PCR. In conjunction with PMWS, co-infections of PCV-2 with porcine parvovirus or PRRSV are being discussed.