Does DON Reduce PRRS Vaccine Efficacy? By Clint Lichty from South West Ontario Veterinary Services

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The level of contamination with mycotoxins such as deoxynivalenol (DON, “vomitoxin”) can vary from year to year depending on field management, growing conditions and grain storage. Pigs are quite sensitive to the toxicity of DON. Toxic levels of DON can lead to a marked decrease in feed consumption. It is also known that DON has a negative effect on the pig’s immune system. These German researchers wanted to assess the effect of various levels of  DON on the pigs ability to control porcine reproductive and respiratory syndrome virus (PRRSV). Three-week-old piglets were divided into four groups. Groups I, II and III (10 animals/group) were vaccinated with a PRRSV modified live vaccine and 2 weeks later challenged with a heterologous field strain of PRRSV.

  • Group I was not supplemented with DON but was vaccinated
  • Group II received DON at a low dose DON (40 µg DON/kg body weight per day corresponding to approx. 1 mg DON/kg feed) for 4 weeks prior to PRRSV challenge
  • Groups III received DON at a high dose DON (80 µg DON/kg body weight per day, corresponding to approx. 2 mg DON/kg feed for 4 weeks prior to PRRSV challenge
  • Group IV received no DON and were unvaccinated but were given a challenge with field strain PRRSV.

The researchers found the following :

  • Group I  vaccinated animals mounted an efficient PRRSV-specific antibody response within 2 weeks. When challenged with PRRSV all Group I pigs were protected from clinical signs.
  • Group II vaccinated animals mounted an efficient PRRSV-specific antibody response within 2 weeks. When challenged with PRRSV all Group II pigs were at least partially protected from clinical signs.
  • Group III  vaccinated animals had 20% of the animals that failed to respond to the MLV vaccine. Clinical signs in group III receiving the higher dose of DON were as severe as in the (unvaccinated, not DON exposed) control group IV. The animals of group III also displayed lower antibody titres compared with the animals in group I and II.
  • Group IV (Control) as expected showed more severe clinical disease when PRRSV challenged

Take Home Messages:

  • Exposure of pigs to DON for a period of 4 weeks prior to heterologous PRRSV challenge reduces the protection against clinical disease provided by an MLV vaccine.

Submitted by Clint Lichty, DVM

Reference:  Antje Rückner  Lisa Plagge , Kristin Heenemann , Maxi Harzer , Bastian Thaa , Janine Winkler , Sven Dänicke , Johannes Kauffold , Thomas W Vahlenkamp The mycotoxin deoxynivalenol (DON) can deteriorate vaccination efficacy against porcine reproductive and respiratory syndrome virus (PRRSV) at subtoxic levels  Porcine Health Manag . 2022 Mar 20;8(1):13. doi: 10.1186/s40813-022-00254-1.