Litter oral fluid testing was more sensitive than bleeding the weakest pig in the litter (for PRRSV detection in suckling pigs)

Porcine Health Manag. 2019 Feb 19;5:8. doi: 10.1186/s40813-019-0115-z. eCollection 2019.

Monitoring PRRSV-1 in suckling piglets in an endemic herd using reverse transcriptase quantitative real time polymerase chain reaction: comparison of the rate of detection in serum and oral fluid samples and evaluation of pooling.

Lebret A1, Boulbria G1, Berton P1, Moalic PY2, Le Guennec J1, Bouchet F1, Auvigne V3, Normand V1.

Author information

1

Porc. Spective Swine Vet Pratice, Chene Vert Conseil veterinary group, ZA du Gohélève, 56920 Noyal-Pontivy, France.

2

Labofarm Finalab Veterinary Laboratory Group, 4 rue Théodore Botrel, 22600 Loudéac, France.

3

Ekipaj, 22 rue d'Assas, 49000 Angers, France.

Abstract

BACKGROUND: 

Defining shedding and exposure status for PRRSV is essential in herd stabilisation protocols and weaning-age pigs is a key subpopulation. Oral fluid (OF) sampling is a welfare-friendly and cost saving promising alternative to blood sampling. The first objective of our study was to compare the rate of detection of PRRSV-1 in individual serum sample, individual OF sample, litter-based OF sample, collected the day before weaning. The second objective was to evaluate the interest of pooling samples.

RESULTS: 

The study was performed on a 210-sows, PRRSV-1 exposed, with confirmed shedding, non-vaccinated against PRRSV, herd. 80 litters were sampled and 26 were viropositive and therefore included. The rate of detection of PRRSV-1 with RT-qrtPCR in blood samples, iOF and cOF was 67, 23 and 77%, respectively. The Ct values from RT-qrtPCR on collective OF were statistically lower if the serum of the piglet of the litter was positive. The lower the Cycle threshold (Ct) value of RT-qrtPCR on collective OF, the higher the probability that the serum sampled in the same litter was positive. Ability to detect PRRSV RNA after pooling was 67% for sera and 58% for cOF.

CONCLUSIONS: 

The rate of detection of PRRSV-1 was about the same in cOF and blood samples. Virus sequencing, if required, should be performed on individual serum samples. The smaller the Ct of a cOF sample from a litter, the greater the likelihood that the serum sample from a piglet of that litter is positive.A cost-effective and representative sampling protocol to monitor sow herds stabilisation of a sow batch could be: to collect both cOF and one serum sample per litter; to perform firstly RT-qrtPCR on pooled cOF; in case of negative results to consider the batch negative; in case of positive results in a unvaccinated herd or a killed vaccine vaccinated one to consider the batch positive; in case of positive result in a herd vaccinated with a modified live vaccine serum samples of litters with positive cOF should be tested for sequencing (selecting the litters with the lowest Ct for cOF).

KEYWORDS: 

Diagnostic; Oral fluid; PCR; PRRS; Pig; Pooling; Serum; Suckling piglets

PMID:

 

30820335

 

PMCID:

 

PMC6381726

 

DOI:

 

10.1186/s40813-019-0115-z