PCR for Ovine Parainfluenza-3 Virus
Parainfluenza-3 virus is one of the most common viral infections of the respiratory tract of domestic ruminants (cattle, sheep, and goats).
Parainfluenza-3 virus is a single stranded, enveloped RNA virus belonging to the Paramyxovirus family of viruses. Historically it was thought that the bovine strain of parainfluenza-3 virus was responsible for infections and disease in sheep and goats. However, new molecular techniques indicate that sheep and goats have their own strains of the virus.
The virus infects calves, lambs and kids when grouped together for any reason, i.e., weaning, husbandry procedures, transport. Transmission is by aerosol droplets or by fomites contaminated with respiratory secretions from infected animals.
Infection spreads rapidly and within a few days many or most animals have fever, clear nasal and ocular discharge, heavy breathing and may be coughing. Usually, infection runs a brief clinical course of three to four days, followed by complete recovery.
Outbreaks can be so mild that no clinical signs are evident.
However, serious disease and pneumonia can occur, particularly if the animals have underlying disease such as chronic respiratory Mycoplasma infection, co-infection with other viruses or are stressed due to poor weather, inadequate nutrition, transport, crowding or unhygienic conditions.
Pneumonia is widespread in Australian sheep.
I have recently completed an abattoir survey to provide information on the prevalence of the common ovine respiratory pathogens circulating in sheep flocks in southern Australia.
The project was a non-blinded, cross-sectional, observational study with sample collection at sheep abattoirs in Australia. Twenty-four abattoir visits were completed between October 2020 and December 2021.
Abattoirs bring together animals from farms and sale yards across a wide geographic area. This provides an invaluable opportunity for animal disease surveillance and means that new farm animal diseases are likely to be first noticed at meat processing plants.
As part of the abattoir survey, I collected samples (bronchial swabs) from 1095 sets of lungs representing 253 abattoir lots.
The bronchial swabs were tested for ovine parainfluenza using an in-house PCR based on the F gene sequence of the virus.
Five of the 253 abattoir lots (2.0%) sampled during the 24 abattoir visits tested positive for ovine parainfluenza-3 virus, including one abattoir lot from New South Wales, one abattoir lot from Tasmania and three abattoir lots from Western Australia.
Four of the abattoir lots positive for the virus were lambs and one was adult sheep.