Combatting emerging coronaviruses
Porcine epidemic diarrhea virus (PEDV) is a significant swine disease worldwide that emerged in the U.S. in the spring of 2013.
To learn more about this important development, we talked with Christa Goodell, DVM, MS, PhD, who serves as the worldwide swine marketing manager for IDEXX.
IDEXX: Christa, what exactly is PEDV and what animals does it affect?
Goodell: PEDV is a nonzoonotic swine disease. It causes an acute, epidemic diarrhea, often with vomiting, in pigs of all ages with essentially a 100% mortality rate in preweaning piglets without immunity. It takes approximately 3–6 weeks for maternal antibodies to kick in, but even then, preweaning mortality may remain as high as over twice the normal rate for weeks or even months. Elimination of the virus has proven difficult and the timeline for eradication in a herd has ranged from 4 months to over 8 months. Unfortunately, even once the disease has been eliminated, herds have become reinfected.
IDEXX: Clearly, PEDV is a concern for swine producers and their veterinarians. Could you outline the reasons for concern?
Goodell: Of course. There are several:
- PEDV causes significant mortality and, therefore, loss of pig production. For example, a 2,500-sow farm should wean approximately 1,100 pigs a week. During a PEDV outbreak, due to the 100% mortality at the outset of the outbreak, no pigs would be weaned for the first 3 weeks and over a period of 8–10 weeks, the farm will likely lose 6,500–7,000 pigs. If the disease is not brought under control using strict herd and health management measures, these losses can continue.
- Control and eradication of the virus has proven difficult for several reasons:
- Only a very small amount of virus is needed to cause clinical disease.
- There is a prolonged shedding period of small amounts of infectious virus.
- The virus is very stable, particularly in cool to very cold and damp or wet settings.
- It appears that immunity is not long-lived and that maternal antibodies may not be completely protective. For example, piglets can be overwhelmed by exposure to PEDV, so even those born from previously exposed and technically “immune” sows have succumbed to the disease.
- The virus is very infectious and spreads quickly and easily. It doesn’t take much to cause disease in a pig or on a farm, nor for the disease to disseminate to other farms via manure; mechanical means, such as boots, feed or air during field application of nutrients; contaminated trucks or other fomites.
- The U.S. industry alone has estimated losses of over eight million pigs each year since the first outbreak in April 2013.