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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Virus and Prion Research » Research » Publications at this Location » Publication #333687

Title: Comparative pathogenesis and characterization of contemporary 1-7-4 PRRSV isolates in weanling age piglets

item VAN GEELEN, ALBERT - Orise Fellow
item Faaberg, Kay
item DAS, PHANI - Orise Fellow
item MONTIEL, NEXTOR - Orise Fellow
item Miller, Laura
item KULSHRESHTHA, VIKAS - Orise Fellow
item BUCKLEY, ALEXANDRA - Orise Fellow
item Lager, Kelly

Submitted to: American Association of Swine Veterinarians Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 9/9/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Porcine respiratory and reproductive syndrome (PRRS) continues to be an economically important disease affecting commercial pig production in the United States and worldwide. It is caused by PRRS virus (PRRSV) which has remarkable sequence and antigenic variation, which contributes to limited protection offered by current vaccine options, that impedes our abilities to control PRRS. Recently, PRRSV isolates of 1-7-4 lineage have been associated with severe clinical cases frequently recognized as dramatic abortion "storms." The genomic sequences of 22 ORF5 restriction fragment length polymorphism (RFLP) 1-7-4 PRRSV isolates were analyzed by next-generation sequencing. We sought to further examine the comparative pathogenesis of 4 contemporary 1-7-4 isolates, selected based on genetic diversity, and one PRRSV isolate of known moderate pathogenicity in weanling age piglets. Eighty-five 4-week-old piglets were divided into 6 treatment group and received an intranasal inoculation with one of the viruses (5 x 10E4 TCID50) or sham inoculum. The isolates were 87.4% to 95.1% identical in genomic sequence for ORFs2-7, but there was considerable difference in pathogenicity between these isolates. Pathogenicity was determined by analyzing average daily gain (ADG), pyrexia measured by intramuscular temperature probe, viral titers in serum and bronchiolar-alveolar lavage (BAL) and gross lung lesions. We identified two isolates that caused more severe disease than our reference pathogenic isolate. Both of these 1-7-4 isolates caused 14% mortality within 2 weeks. The group of pigs infected with NADC-34 isolate had the highest average body temperatures of 41C on 5, 8 and 9 days post infection (dpi), a decrease in ADG of 98.4%, peak serum titers of 10E2.9 TCID50/ml at 4 dpi and 10E4.9 TCID50/ml BAL titer. Isolate ISU/2014/3 with peak serum viral titers at 7 dpi of 10E3.7 TCID50/ml and 10E5.4 TCID50/ml BAL titer, caused a 63.2% decrease of ADG, and reached peak temperatures of 40.5 to 40.7 between 5-8dpi. On the other hand, isolate ISU/2014/2 caused no pyrexia, had a 4.6% decrease in ADG but still had peak serum viral titers of 10E2.6 TCID50/ml at 7dpi and BAL titer of 10E2 TCID50/ml. This study shows that there is considerable difference in disease outcome caused by PRRSV isolates grouped under the 1-7-4 lineage and that other parameters of pathogenicity remain to be identified for future evaluation of disease.