Canine Distemper Virus, CDV
The canine distemper virus (causative agent of Carré's disease, Canine Distemper Virus, CDV) from the family Paramyxoviridae (genus Morbillivirus) is closely related to the measles virus of humans. Despite this relationship, the disease is not dangerous to humans. Canine distemper virus occurs not only in dogs but also in wild carnivores such as foxes, martens, badgers, polecats, weasels, raccoons and otters. Especially in the case of the red fox, an increase in distemper infection has also been observed in Austria in recent years.
The distemper virus is spread worldwide. In Spain, four cases of dogs with neurological symptoms were described in 2014. Three animals were vaccinated annually against distemper, one animal had the last vaccination 4 years ago. Apparently, the three animals were weak antibody producers and thus inadequately protected against field infection. In Denmark, the entry of CDV infection via wild canids into a fur farm was revealed. In 2013, a CDV outbreak in raccoons in urban areas was reported in Germany. In the red fox, an increase in distemper infections has been observed in Austria in recent years. Affected wild animals lose their shyness towards humans and often show movement disorders, which are an important differential diagnosis to rabies.
Transmission occurs via saliva, nasal and eye secretions, faeces and urine of sick animals or clinically healthy permanent carriers. Transmission is mainly by direct contact, but also indirectly by ingestion of infected food or water. In general, young dogs are more susceptible than older ones; the highest susceptibility is between four and six months of age.
Depending on which organs are affected, different courses are described. In most cases, a systemic infection occurs, which is initially accompanied by gastrointestinal and/or respiratory symptoms and later develops into a neurological disease.
The incubation period in dogs is between 3 and 7 days. Initially, the virus multiplies in the throat and bronchial lymph nodes. Subsequently, the viruses migrate into the bone marrow, lymphatic and nervous tissue. Depending on the organs affected, various symptoms can be observed, such as diarrhoea, vomiting, coughing, shortness of breath as a result of primary interstitial pneumonia, nasal discharge and even conjunctivitis. There may also be keratinization of the nasal and toe pad epithelium (hard pad disease). In addition, there is usually a high fever and exhaustion.
Canine distemper disease can vary in severity depending on the immune status. If the nervous system is affected, signs of brain disease appear and the chances of survival are very low or permanent nervous damage develops (distemper tick).
Mandatory vaccination, especially for hunting and guard dogs, helps to control this contagious viral disease. It is important to vaccinate dogs consistently at a young age and to refresh this core vaccination accordingly. This can almost completely eliminate the risk of distemper in susceptible domestic dogs.
Increased puppy trade with Eastern European countries increases the risk of disease introduction. Illegal imports to or through Austria represent a lasting trauma for the puppies, which are often far too young and not sufficiently vaccinated and socialised. In the period from 01.01.2014 to 30.09.2015, 51 animals from all over Austria were examined for distemper in the veterinary institutes of the AGES. In 34 cases, a diagnosis could be made by means of immunohistochemical examination for canine distemper antigen. The positive animals were 27 foxes, three dogs, two martens, one badger and one ferret.
In Tyrol, distemper was diagnosed in three dogs, two foxes and one ferret within one month in summer 2015. Clinical signs in one dog were rhinitis, pneumonia, epileptiform seizures, fever. Despite therapy, the animal showed no improvement and died. The anamnesis revealed an origin from an Eastern European animal shelter.
In recent years, increased local cases of distemper (epidemics) have been observed in wild carnivores in Austria.
Canine distemper virus can be detected, for example, in epithelial cells of numerous organs, nerve cells and lymphocytes; this can be detected in the form of intracellular inclusions or also nuclear inclusions in the histological preparation of organs by means of haematoxilin-eosin staining or, more sensitively, by immunohistochemical examination.
As a rule, a tentative diagnosis is made in pets and companion animals on the basis of clinical symptoms. The clarification can be made by means of a swab (paryngeal, conjunctival swab samples) and further analysis (PCR) in the laboratory.
Last updated: 10.10.2023