Diarrhea Example of Pig Disease Complexity

Since last year China's swine farms have been having serious problems with diarrhea. A recent article describes the symptoms and treatment in much more detail than you want to know (unless you are a veterinarian working on a pig farm in China). The description of the disease is an example of the trend toward more complex diseases that are not only increasing in prevalence but are hard to treat.

The highest incidence and highest mortality rates of diarrhea are among young piglets. Newborn pigs stop nursing, become listless, and then their body temperature drops. They develop serious diarrhea: yellow, white, yellow-green, gray and watery, smelly. Some pigs have vomiting, weight loss, pale skin. Some get purple orchid-shaped spots on their skin and purple ears. Piglets can start dying two days after exhibiting symptoms. Piglets 15 days older or less have a very high death rate, some pig farms 100%. Diseased pigs are thin, their hair is dull, and their skin is white.

Sows and finishing pigs are affected too, but the symptoms tend to be minor and they often recover within a week. While sows have less severe symptoms, their lactation is affected.

There is no fixed pattern to the outbreaks. In some farms only piglets are affected; in others both piglets and sows are sick. In some farms 100% of finishing hogs are affected by the disease but they generally recover.

The onset of the epidemics is rapid, they spread widely and can last a long time. Sometimes the mortality rate is high; sometimes it is low. Farms with weak management that pay scant attention to biosecurity and immunizations have the highest infection rates and major economic losses. However, large scale farms with good management also have the disease. The infection commonly reoccurs after innoculation, sometimes minor, sometimes major with high mortality.

Another article appearing last month sounds an alarm bell over the increasing number, diversity, and complexity of swine diseases. The author asks rhetorically why the number and complexity of pig diseases in increasing, not decreasing. Why are there diseases we can't explain or understand? What are we to do?

Pathogens are mutating, diversifying and the causes of disease are more complex. He gives examples. "Everybody knows 'blue ear disease,'" he says. The author also cites a recent spread of Torque teno virus and the recent diarrhea outbreak. He says there is a crest virus "closely related" to the diarrhea epidemic, but its role is not understood.

When diseases appear, he says, there are usually multiple pathogens present and secondary infections. This leads to clinical complexity and makes accurate clinical and laboratory diagnosis difficult and control is difficult. What is a farm to do when there are two, three or more pathogens and secondary infections. What medication should be used? What immunization?

Another difficulty is the presence of latent infections in carrier animals and sub-clinical symptoms. Pigs can appear healthy but spread a virus like PRRS, pseudorabies, or classical swine fever. It is difficult for a farm to claim with certainty that its pigs are completely free of pathogens, healthy and clean. Building new, large-scale farms is viewed by agriculture officials as an important measure for controlling the spread of disease. However, the author declares that disease problems are escalating on large-scale farms. Disease pressures are becoming greater and greater.

The author applauds the Ministry of Agriculture for its recent announcement of a program to monitor disease on 100 seed-stock breeding farms. Breeding pigs are the key to controlling the spread of disease.