There has been a recent re-emergence of feline strains of parvovirus in Australia. Parvovirus expert and feline specialist Dr Vanessa Barrs says vaccination for the highly contagious viral illness is a serious consideration for animal shelters and requires further legislative action.
“Within the carnivore proto-parvovirus 1 (CPV-1) species there are different dog and cat adapted strains. Feline panleukopenia virus is a cat adapted strain while the dog adapted strains are canine parvoviruses. These are all very closely related strains,” Vanessa says.
“The feline panleukopenia virus has been around for at least one hundred years, however, canine parvovirus emerged as a new infection in dogs in the late 1970s. Within a year, canine parvovirus mutated and became what’s known as the CPV-2a strain, which is able to infect both dogs and cats.”
The virus has further mutated into strains referred to as CPV-2b and CPV-2c, with CPV-2c reported for the first time in Australian in May this year. Vanessa says the recent emergence of CPV-2c in dogs in Australia has raised concerns because of the severity of clinical disease caused by that particular strain.
Vets should not be alarmed because CPV-2c emerged in Europe in the year 2000 and, overall, vaccines containing CPV-2 or CPV-2b confer protection against the new strain and reports of vaccine failures are rare. But Vanessa warns that the re-emergence of feline panleukopenia is more troubling.
“In 2014, panleukopenia re-emerged in cat shelters in Melbourne causing mass fatalities in shelter-housed cats. This is very interesting as for the past 30 years there have been very few clinical cases of panleukopenia reported by vets around Australia,” Vanessa says.
“The outbreaks were caused by a strain that is fully protected by vaccination – that’s good news. But we still have a problem with our shelters. There is currently no legislative requirement for shelters to vaccinate cats, which is a leading reason why the disease has re-emerged.”
Although the pressure on shelters not to euthanise stray or abandoned cats is a positive change, Vanessa says without action to ensure cats are vaccinated the trend will likely pose higher risk of viral outbreak.
“There is immense public pressure on shelters not to euthanise cats, which is great and what we want to see. But that’s actually translating to longer individual cat stays per shelter, which means that each cat is more likely to be exposed,” Vanessa says.
Vanessa says cats younger than one year old are most susceptible to infection, especially around the time of waning maternal antibodies, which contributes to a potential immunity gap in vaccinated kittens.
“Even if those cats have been vaccinated, the presence of maternal antibodies at a low level can interfere with the vaccine. Furthermore, the maternal antibody level may not be high enough to provide protection against infection. It’s an immunity gap that means vaccinated animals are still susceptible to disease,” she says.
The presentation of parvovirus in cats includes high fever, lethargy and loss of appetite, which is followed by vomiting and diarrhoea. Dogs present with similar symptoms, but the gastrointestinal signs are often much more severe, including the presence of haemorrhagic diarrhoea.
“In an unvaccinated animal, diagnosis is relatively uncomplicated. The simplest way of achieving diagnosis is using a faecal antigen test to detect the presence of parvovirus in the faeces,” Vanessa says.
“But false negative results can occur early on when viral loads are low and a negative test result doesn’t rule out infection. In animals with suspicious clinical signs, the faecal antigen test should be repeated 12 to 24 hours later, or a faecal PCR should be performed.”
Vanessa warns that diagnosing vaccinated animals can be more complicated.
“If a puppy of a kitten has been vaccinated, it may still be within the immunity gap where it could be vaccinated but also infected,” Vanessa says.
“Animals vaccinated with modified live vaccines will shed the virus in their stools for around 3 weeks. This means that if you get a positive faecal antigen test, you may just be detecting vaccine virus. In that situation, you need to rely on clinical signs and supporting blood test results, such as the presence of panleukopenia or severe neutropenia on full blood count.”
Vanessa will be presenting on the re-emergence of feline panleukopenia in Australia at the upcoming the 2017 FASAVA Congress held on the Gold Coast from 11 – 14 August.
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