Dr Annie Labuscagne, CS Vet
Porcine Epidemic Diarrhoea virus (PEDv) has made headlines in recent months – especially in the USA where it is having a major impact on production. PEDv has been around for some time. It was first reported in the United Kingdom in 1971.
The disease was characterised by severe enteritis, vomiting, watery diarrhoea, dehydration, and a high mortality rate among pigs. Subsequently, the causative agent of PED was identified as porcine epidemic diarrhea virus (PEDv), which belongs to the family Coronaviridae. A close family member is TGE (transmissible gastric enteritis). PED is endemic in Europe and Asia, but it has only been introduced into the United States in the spring of 2013. The disease is not present in South Africa at this stage.
When PEDv is first introduced into a naïve herd, the impact is devastating. After introduction it takes approximately four to five days for clinical signs to appear. The virus is shed for seven to nine days.
Clinical signs include vomiting, sudden profuse watery diarrhoea (veterinarians in the US said it was so watery that they could not use a spoon to collect samples, they had to use paper towel to blot samples), and loss of appetite in pigs of all ages within susceptible breeding herds or integrated premises. Morbidity approaches 100 percent.
Suckling piglets will have a watery diarrhoea and dehydration. Piglets younger than three weeks can have up to 100% mortality.
Growers will have diarrhoea, anorexia, depression with a high morbidity, but low mortality (1 – 3%) PED is introduced into a herd via faecal-oral contact with infected pigs, but it can also be introduced via contaminated equipment, fomites or personnel. Infected pigs, manure or anything that carries manure may transfer the virus. It is known that a large amount of PEDv is carried in a small amount of manure. PEDv can survive for an extended period in manure.
Currently a lot of research is being done on this disease in the United States. Some of this research focus on identifying factors that seem to be common on farms that test positive for PEDv that differ from farms in the same area that are testing negative. They have identified the following trends (this might change as more data is collected and analysed):
PEDV-positive sites had approximately double the frequency of feed-truck deliveries when compared to negative sites.
PEDV-positive sites had approximately triple the frequency of trucks visiting to remove pigs of any age from positive sites compared to negative sites.
There were approximately five times as many trash pickups from positive sites compared to negative sites.
Approximately double the percentage of positive sites had dead stock removal vehicles on the premises in the two weeks preceding infection.
Sanitation and good biosecurity are the best means of protection. The following principles should be strictly adhered to:
- Make use of an all-in all-out system
- If you make use of transporters, outside maintenance contractors or any service supplier, make sure that they understand your farm’s biosecurity protocol and that they implement it.
- Where possible stock a site with the necessary maintenance equipment to prevent the disease from entering on a dirty tool.
- Anybody entering the unit must shower in.
- If possible no truck must enter your unit, but if a truck must enter, make sure that it is clean and dry.
Several disinfectants have been demonstrated to effectively inactivate PEDv, such as formalin, sodium carbonate, lipid solvents, and strong iodophors in phosphoric acid. Vaccines have been tried, but have been historically ineffective.
Currently the disease is being eliminated by the quick and complete exposure of the entire population to the virus. Elimination in a breeding herd generally uses immediate feedback of infected material with herd closure followed by sentinel testing. All replacement gilts necessary for a period of four to six months should be in the farm during the feedback exposure period. Sentinel animals may be used to determine if the virus has been eliminated prior to resumption of replacement flow (introduction of naïve animals). Feedback material consists of faecal material of infected animals or the intestinal tracts of scouring piglets.
The South African pig herd is naïve and the introduction of PEDv into this country could have a similar impact on our industry than what it is having on the US industry. It is everybody’s responsibility – on national, provincial and producer level – to prevent this disease from entering the country. Every pig producer must be sure that his biosecurity protocols can prevent his herd from becoming PEDv positive.
Porcine Epidemic Diarrhea, Diagnosis and Elimination; Jerome O. Geiger, DVM, MS, Joseph F.Connor, DVM, MS.
Powerpoint presentation: Practitioner perspective when faced with PEDv; Matt Ackerman, DVM
Time to fine-tune biosecurity basics, Lora Berg, www.nationalhogfarmer.com
www.pork.org PEDv Resources