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Effect of Modified-Live PRRS Virus Vaccine on Shedding of Wild-Type Virus from Pigs

10 June 2016

Global PRRS Solutions - Boehringer Ingelheim

A clear way to reduce the risk of infection (or reinfection) of a farm by PRRSv is to reduce the presence of virus in the environment. This study was designed to determine if the use of a PRRS modified-live virus vaccine (MLV) reduced the viral shedding into the air and therefore potentially contribute to a better outcome of a regional control program on the field.

How is it done?

Two thousand and fourteen 3-week old PRRSv-free piglets were used. They were housed in two independent (with separate air spaces) finishing barns (1000 piglets approximately per barn).  At 8 weeks of age, 10% of the pigs of each room (2-3/pen) were inoculated with PRRSv. At 8 and 36 days post infection, all pigs of one of the rooms (challenge-vaccine group) were vaccinated with 2 ml of Ingelvac® PRRS vaccine, while the pigs in the other room received 2 ml of saline solution.

Blood and oral fluid samples were collected from each room at 0, 8, 36, 70, 96 and 118 dpi for PRRSv RNA and antibodies detection using PCR and ELISA.

Also, air samples were collected 6 times per week from 0 to 118 dpi and were tested for PRRSv RNA using qPCR assay.

What are the results?    

The challenge-vaccine group had significantly less PRRSv shed and PRRSv-positive oral fluids compared to the non-vaccinated piglets.

The following diagram illustrates the air sample results with qRTPCR. The vaccine piglet group had a significant reduction in the total number of days that PRRSv RNA was detected in air samples (14 days, p = 0.0004). Also, they had a shorter period of time (25 days) that had air samples positive for PRRSv RNA.

What implications does this paper have?

This study shows for the first time that using a PRRS MLV is an effective tool to reduce the PRRSv load in oral fluids and in the air produced by PRRSv infected pig populations.

These results supported vaccination in infected pig populations with PRRSv MLV vaccine to enhance the success of PRRSv regional control.

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