Maybe one of the health companies will soon be registering something like “stopped” as a commercial name for a vaccine to fight the porcine epidemic diarrhea (PED) virus in swine herds. Or, if they do not like that as a vaccine name, they might try “PEDal” or “PEDestal” or even “zapPED.” Whatever the choice, you can bet that a name of some sort will be needed shortly for a PED virus vaccine as it is prepared for marketing in response to the storm of cases in North America in recent months.
The animal health industry can move fast when the need arises – just look at how quickly a crop of vaccines appeared against the porcine circovirus type 2 (PCV2) that was causing havoc with postweaning multisystemic wasting syndrome (PMWS) and related symptoms.
On this occasion, there is also history to help. Experimental PED virus vaccines were produced as long ago as the 1980’s, when the virus was identified that had hit British herds about 10 years earlier before spreading rapidly throughout the rest of Europe and parts of Asia.
But the case for vaccinating was weaker then, as most of us considered PED virus to be little more than a nuisance, because it could be confused with transmissible gastro-enteritis (TGE). It stopped susceptible weaned pigs from growing, certainly, but it did not often kill them, and (initially, at least) it did not appear to strike at other ages in the pig population.
The first description of PED virus in 1972 happened to coincide with the date of the first of the modern series of biennial congresses of the International Pig Veterinary Society (IPVS), following an inaugural event in 1969. The latest manifestation of the disease, not least in North America, is sure to provide plenty of conversation between the veterinary experts at the IPVS Congress coming to Mexico in June 2014.
The virologists will want to discuss whether the virus in North American herds differs in any way from PED virus agents encountered on other continents and whether its means of entry into the U.S. and Canada can be identified. Recent studies associating its spread with the transport and marketing of pigs, in fact, add little to the story because that much was known years ago, as was the ability of the virus to ride into a new herd inside carrier infected pigs.
Blaming an explosive spreading of cases on an extra-virulent or hot form of the virus may also be wide of the mark, on past experiences. All PED virus ever needed was access to a population of pigs that did not already possess a protective immunity against it. Outbreaks were invariably explosive in susceptible populations of that type.
The main response in the past was, therefore, to create an immunity before the challenge of the virus occurred. Usually this meant infecting sows artificially, provided they were not due to farrow in the next two weeks. Soon now, as IPVS 2014 in Mexico is sure to hear, the process of creating an immunity is more likely to involve vaccinating – once vaccines are accepted for the market and have been given an appropriate name!