Clinical case: A PRRS Case

The farm is located in the northeast of the Iberian Peninsula. It has 3,000 sows producing piglets until 6 kg. The case was presented in April 2011. Until the appearance of the case, in March, production was pretty good; the results were as follows:

The farm has a conventional health status: positive for PRRS, M. hyo, S. suis, mange, atrophic rhinitis. The farm purchases semen and does its own replacement gilts, among grandmothers.

Regarding the farms’ vaccine plan, they practice the following:

Quarantine:

• Parvo + erysipelas
• AD
• AR
• Live PRRS
• Influenza

Gestation:

• AR + Colibacillosis
• AD live every 3 months
• Live PRRS (blanket vaccines twice per year)

Lactation:

• Parvo + erysipelas

This case starts with abortions that occur dramatically in April. They begin on Saturday the 23rd and during the following week continue until reaching 34 abortions. Mid week, before the dramatic increase in abortions, it was decided to draw blood from 16 sows among those that aborted and those that hadn’t. The abortions occurred at 91 days of gestation.

The results of the analysis are as follows:

Also, 4 pools of 4 pigs each were made to test for PRRS by PCR; 2 resulted positive and two negative.

Additional data

To detect influenza the INFLUENZA CIVTEST was done with reference values NEG 0-10, 10-20 DUD, POS> 20.

For Leptospira, plate agglutination tests was carried out.

For erysipelas, MR CIVTEST, with reference values NEG <30, DOUB 30-40, POS >40.

For porcine parvovirus, hemoagglutination inhibition (PPV) with the reference values POS> 1 / 8 contact with virus > = 1 / 256

The interpretation of these results leads them to an "emergency" vaccination against PRRS, vaccinating all sows with a live vaccine on 6 May.

Four days later, on May 10th, there are 13 abortions and 21 on the 11th. The dramatic increase in abortions lasts until late May, totaling 127 abortions to date at 99 days of gestation.

Finally on June 1st it was decided to do another analysis. In this case, 6 sera samples from 6 sows were sent to the laboratory.

Additional data

For Leptospira plate agglutination tests were carried out.
For erysipelas, MR CIVTEST with reference values NEG <30, DOUB 30-40, POS >40.

For porcine parvovirus, hemoagglutination inhibition (PPV) with the reference values POS> 1 / 8 contact with virus > = 1 / 256

Before attempting to come to conclusions about the case and what may have happened we can take a look at the following results:

It is not easy in "hindsight" to know for sure what happened on April 23; the only clear symptoms were the abortions, a few sows with anorexia and nothing else. If we review the serology done on April 27, we can see 100% were positive for influenza, 90% were positive for erysipelas, 86% were positive for PRRS and 75% were positive for parvo. Was it an outbreak of influenza that took an effect or was it PRRS? By looking in depth at the PCR for PRRS we can see how, in the pools of the 8 sows that were negative, 7 were sows that had aborted, whereas in the 8 that were positive only 3 had aborted. With this extra information we cannot ensure that, at the time, PRRS was the cause of the outbreak.

What it is evident is that the effect of the vaccination was worse than the outbreak itself. They went from 4% of abortions to almost 20%. The mistake was in vaccinating sick animals.