The Guilty Gilt Guide was written with a clear objective – to maximize the whole-herd performance of pig populations by helping gilts to reach their full reproductive potential and produce healthy pigs that reach their full genetic potential during grow-finish.
The open reading frames (ORF)5 represents approximately 4% of the porcine repro- ductive and respiratory syndrome virus (PRRSV)-2 genome (whole-PRRSV) and is often determined by the Sanger technique, which rarely detects >1 PRRSV strain if present in the sample.
Porcine reproductive and respiratory syndrome virus (PRRSV) is an important swine pathogen affecting the global swine industry.
Mycoplasma hyopneumoniae (M. hyopneumoniae) infections continue to result in significant respiratory challenges in the swine industry worldwide. Vaccination for M. hyopneumoniae is commonly utilized, as reduction in bacterial loads and clinical severity in vaccinated pigs have been shown. However, the effect of M. hyopneumoniae vaccination on transmission across different pig populations has been minimally investigated.
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Twenty-eight hundred and seventy-two cases of respiratory disease in pigs were analyzed for their etiologic agents. Two or more pathogens were detected from 88.2% of the cases, indicating that porcine reproductive and respiratory syndrome virus (PRRSV) or swine influenza virus (SIV) combined with other bacterial agents was a common cause for porcine respiratory diseases in the mid-western USA.
The aim of this study was to compare the pathogenicity of single or dual infections with type 1 and type 2 porcine reproductive and respiratory syndrome virus (PRRSV) in pigs. Pigs were inoculated intranasally with type 1 or type 2 PRRSV or both viruses together. Pigs infected with type 1 and type 2 PRRSV together had significantly (P <0.05) fewer genomic copies of type 1 PRRSV than did pigs infected with type 1 PRRSV alone. Pigs infected with type 2 PRRSV alone or type 1 and type 2 PRRSV together had significantly (P <0.05) higher gross and microscopical lung lesion scores than did pigs infected with type 1 PRRSV alone. Pigs infected with type 2 PRRSV alone or type 1 and type 2 PRRSV together had significantly (P <0.05) higher scores for PRRSV-positive cells in the lung than did pigs infected with type 1 PRRSV alone. Pigs infected with type 1 PRRSV alone had significantly (P <0.05) higher scores for type 1 PRRSV-positive cells in the lung than did pigs infected with both types of PRRSV together. Pigs infected with both types of PRRSV together developed similar clinical disease and lesions as pigs infected with type 2 PRRSV alone. Significant differences in virulence were not observed between pigs infected with type 2 PRRSV alone and pigs infected with both types of PRRSV together in terms of viraemia, lung lesion score and virus distribution within lung lesions.
A better understanding of the differences in the infection patterns of the virus in growing pig batches would help to develop cost-effective surveillance methods and disease control and elimination programs. Therefore, field studies documenting growing pig productivity according to the patterns of wild-type-PRRSV (wt-PRRSV) detection in the field are needed. This study was conducted with the objectives to (1) characterize patterns of wt-PRRSV-1 and wt-PRRSV-2 RNA detection over time in modified-live virus (MLV)-vaccinated batches of growing pigs raised in pig-dense regions of the USA; (2) compare wean-to-finish mortality among batches of growing pigs characterized with the different patterns of wt-PRRSV-1 and wt-PRRSV-2 detection; and (3) compare wean-to-finish mortality among batches of growing pigs characterized with the different patterns of wt-PRRSV-2 detection and vaccinated with two different doses of PRRS MLV vaccine.
Eighty-one batches of growing pigs were originated from PRRSV positive-stable and unstable sow farms and vaccinated with two different doses of PRRS MLV vaccine. All batches were monitored for wt-PRRSV by testing six oral fluids every three weeks from weaning to marketing. Diagnostics were conducted to detect wt-PRRSV-1 and wt-PRRSV-2 by RT-qPCR testing and ORF-5 region sequencing. K-means clustering analysis was applied to identify batches sharing similar patterns of wt-PRRSV detection over time. Regression analyses were used to compare mortality among batches of growing pigs characterized with different patterns of wt-PRRSV detection over time.
Thirty-eight percent of batches were detected with wt-PRRSV-1 during the growth phase, with three different patterns of detection. Detection of wt-PRRSV-1 was not associated with significant increase on mortality. Ninety-one percent of batches were detected with wt-PRRSV-2 during the growth phase, with four different patterns of detection. Batches originated from PRRSV positive-unstable farms had highest mortality rate (p < 0.0001) and were characterized as Unstable wt-PRRSV-2 detection pattern. Batches characterized with Early wt-PRRSV-2 detection pattern had higher mortality than batches characterized by Mid, Late and No wt-PRRSV-2 detection during the growth phase (p < 0.0001). Batches with Mid wt-PRRSV-2 detection had higher mortality than batches characterized with Late wt-PRRSV-2 detection (p < 0.0124). Mortality rate of batches characterized with Unstable and Early wt-PRRSV-2 detection patterns was lower when pigs were vaccinated with two doses of PRRS MLV vaccine, compared to batches that received only one dose.
Results presented in this study suggested that early wt-PRRSV exposure on pig populations was associated with higher wean-to-finish mortality. Additionally, results suggested that vaccination with two PRRS MLV doses was associated with lower mortality rate, when growing pig populations had early wt-PRRSV exposure.
Porcine reproductive and respiratory syndrome virus (PRRSV) isolates are classified in two different genotypes, based on genomic heterogeneity: type 1, which comprises European type isolates, and type 2, which includes North American type isolates. It is believed that members of both genotypes differ in some biological properties including pathogenicity, however extensive studies comparing isolates of both genotypes have never been carried out. The objective of the present study was to compare the pathogenic properties of six different PRRSV isolates, three of type 1 and three of type 2, in a young pig infection model. For this purpose, a total of 105 3-week-old piglets were divided in 7 groups of 15 animals that were exposed on day 0 of the experiment to one of the six isolates tested or were mock infected (negative control group). Clinical signs and rectal temperatures were recorded daily and blood samples were taken on days 3, 6, 9, 12, 15, 18 and 21 of the experiment. On days 7, 14 and 21 post-inoculation five animals per group were sacrificed, macroscopic lung lesions were evaluated and different tissue samples were collected to determine viral organic distribution. The results obtained indicate that type 2 isolates are more pneumovirulent than type 1 isolates, as demonstrated by the recording of respiratory clinical signs only in pigs exposed to type 2 viruses and by the severity of macroscopic and microscopic lung lesions in those pigs. However, no clear differences could be established between genotypes in systemic clinical signs or viral load and viral distribution after challenge. These results support the general idea that type 2 isolates induce more severe respiratory disease than type 1 isolates.