Epidemiology – Page 18 – Swine in Minnesota

Mycoplasma hyorhinis prevalence varies based on pigs’ age

Summary

Mycoplasma hyorhinis can cause polyserositis and arthritis in post-weaning pigs.
To study M.hyorhinis‘ prevalence based on age, nasal swabs were taken from pigs at 1, 7, 14, 21, 28, 35, 42, 49, 56, 63, 70 and 77 days as well as from sows, in 3 different Minnesotan herds (A, B, and C).
8.8% of the sows were positive for M.hyorhinis in herds A and B whereas 3.3% of the sows were positive in herd C.
The percentage of positive piglets (<21 days of age) was low: between 0 and 10% depending on the herds.
At 28 days of age, the prevalence of M.hyorhinis in pigs increased dramatically to around 50% in herd A and 100% in herd B. After 42 days of age, the prevalence in those herds stayed above 95%.
The prevalence in herd C stayed close to 0% until the pigs reached the age of 77 days, time at which the prevalence increased to 100%.

Did you see our Science page on Mycoplasma hyorhinis and swine conjunctivitis?

Mhyorhinis prevalence baed on age Rovira 2017

Abstract

Mycoplasma hyorhinis is one of the causative agents of polyserositis and arthritis in postweaning pigs. Knowledge regarding colonization frequency and age distribution in modern pig production is lacking. The objective of this study was to estimate the prevalence of M hyorhinis colonization in different age groups across three commercial pig populations. Nasal swabs were collected from sows, piglets and nursery pigs of different ages. Oral fluids were collected from nursery pigs. Necropsies were performed to assess the presence of M hyorhinis-associated disease. M hyorhinis was detected in 5/60 sows in herd A, 3/60 in herd B and none in herd C. In herd A and B, the prevalence was low in preweaning piglets (∼8 per cent) and high in postweaning pigs (∼98 per cent). A total of 7/8 oral fluids tested PCR positive in herds A and B, while 1/8 tested positive in herd C. In herd C, the preweaning and postweaning prevalence was low. In herds A and B, necropsied pigs had polyserositis lesions where M hyorhinis was detected by PCR. This study showed that prevalence of M hyorhinis colonization varies with pig age and across farms. Information generated will aid in the design and implementation of control and prevention strategies.

Link to the full paper

Can biosecurity measures prevent PEDV transmission?

Summary:

Porcine Epidemic Diarrhea virus is highly contagious.

The 2013 Porcine Epidemic Diarrhea virus’ (PEDV) outbreak in the USA taught the swine industry that the virus is highly contagious. This event forced producers and veterinarians to review and upgrade their biosecurity procedures.

Drs. Torremorell, Cheeran, and Goyal from the University of Minnesota evaluated some of these measures and how they can prevent PEDV transmission.

Changing Personal Protective Equipment (PPE) and showering before entering a new room prevented contamination.

Among the measures included in this study were the use and change of PPE as well as showering in and out of a facility. In the low biosecurity setting, personnel went from a room with PEDV positive pig straight to a room with naive pigs, contaminating them after the very first movement. In the medium biosecurity setting, personnel washed their hands and face and change their PPE before being in contact with the naive pigs. In this situation, pigs stayed negative for PEDV but two personnel hair/face swabs came back positive for viral genetic material. On the contrary, personnel showered before getting in contact with the high biosecurity group. Those pigs as well as all personnel tests remained negative for PEDV during the study.

Abstract

Background:

The effectiveness of biosecurity methods to mitigate the transmission of porcine epidemic diarrhea virus (PEDV) via farm personnel or contaminated fomites is poorly understood. This study was undertaken to evaluate the effectiveness of biosecurity procedures directed at minimizing transmission via personnel following different biosecurity protocols using a controlled experimental setting.

Results:

PEDV RNA was detected from rectal swabs of experimentally infected (INF) and sentinel pigs by real-time reverse transcription polymerase chain reactio n (rRT-PCR). Virus shedding in INF pigs peaked at 1 day post infection (dpi) and viral RNA levels remained elevated through 19 dpi. Sentinel pigs in the low biosecurity group (LB) became PEDV positive after the first movement of study personnel from the INF group. However, rectal swabs from pigs in the medium biosecurity (MB) and high biosecurity (HB) groups were negative during the 10 consecutive days of movements and remained negative through 24 days post movement (dpm) when the first trial was terminated. Viral RNA was detected at 1 dpm through 3 dpm from the personal protective equipment (PPE) of LB personnel. In addition, at 1 dpm, 2 hair/face swabs from MB personnel were positive; however, transmission of virus was not detected. All swabs of fomite from the HB study personnel were negative.

Conclusions:

These results indicate that indirect PEDV transmission through contaminated PPE occurs rapidly (within 24 h) under modeled conditions. Biosecurity procedures such as changing PPE, washing expose d skin areas, or taking a shower are recommended for pig production systems and appear to be an effective option for lowering the risk of PEDV transmission between groups of pigs.

Link to the full text

Characterizing Canadian rotavirus A strains and their similarity to a commercial vaccine

Summary:

Rotaviruses A are genetically diverse.

Rotaviruses are responsible for increased mortality in neonatal swine populations. They are different genetically and more studies are needed to characterize their diversity. This is the objective of this study coordinated by Dr. Marthaler’s lab focusing on rotaviruses strains found in Canada.

Viral proteins 7 and 4 are used for rotavirus A classification.

Rotaviruses are classified based on two viral proteins (VP) found on their outer capsid called respectively VP7 and VP4. Those two proteins are also essential to induce an efficient immune response against the virus. This project characterized VP7 and VP4 sequences in 136 Canadian samples and compared them with the strains used in a rotavirus commercial vaccine.

The VP7 (n=32) and partial VP4 (n=25) were analyzed, identifying the G3P[13], G5P[7], G5P[x], G9P[7], G9P[13], G9P[19], and G9P[x] genotypes.
Minimal differences in the antigenic epitopes for the G5, G9, and P[7] strains were identified.
Major differences in the antigenic epitopes of the G3, P[13], and P[19] may question the effectiveness of the ProSystems RCE RVA.

Abstract

Surveillance of Rotavirus A (RVA) infections in North America swine populations are limited and not performed over a significant time period to properly assess the diversity of RVA strains in swine. The VP7 (G) and VP4 (P) genes of 32 Canadian RVA strains, circulating between 2009 and 2015 were sequenced, identifying the G3P[13], G5P[7], G9P[7], G9[13], and G9[19] genotype combinations. The Canadian RVA strains were compared to the RVA strains present in the swine ProSystems RCE rotavirus vaccine. The comparison revealed multiple amino acid differences in the G and P antigenic epitopes, regardless of the G and P genotypes but specifically in the Canadian G3, P[13] and P[19] genotypes. Our study further contributes to the characterization of RVA’s evolution and disease mitigation among swine, which may optimize target vaccine design, thereby minimizing RVA disease in this economically important animal population.

Link to the full article

Air samples successful in detecting on-farm PRRSV, PEDV, and high-path avian influenza virus

Summary:

From Dr. Torremorell’s lab at the University of Minnesota, College of Veterinary Medicine
Porcine Reproductive and Respiratory Syndrome virus (PRRSV), Porcine Epidemic Diarrhea virus (PEDV), and High-Path Avian Influenza virus (HPAIV) are transmitted via aerosols.
Air samples taken out of positive farms were successful in isolating HPAIV and PEDV 61% and 69% of the time respectively whereas PRRSV was found 8% of the time.
For all three viruses, higher quantity of genetic material was found when the size of the particle was larger.

More articles on air samples as a method to study respiratory pathogens

Alonso 2017 Assessment of air sampling methods ans size distribution of virus-laden aerosols

Abstract:

Swine and poultry viruses, such as porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), and highly pathogenic avian influenza virus (HPAIV), are economically important pathogens that can spread via aerosols. The reliability of methods for quantifying particle-associated viruses as well as the size distribution of aerosolized particles bearing these viruses under field conditions are not well documented. We compared the performance of 2 size-differentiating air samplers in disease outbreaks that occurred in swine and poultry facilities. Both air samplers allowed quantification of particles by size, and measured concentrations of PRRSV, PEDV, and HPAIV stratified by particle size both within and outside swine and poultry facilities. All 3 viruses were detectable in association with aerosolized particles. Proportions of positive sampling events were 69% for PEDV, 61% for HPAIV, and 8% for PRRSV. The highest virus concentrations were found with PEDV, followed by HPAIV and PRRSV. Both air collectors performed equally for the detection of total virus concentration. For all 3 viruses, higher numbers of RNA copies were associated with larger particles; however, a bimodal distribution of particles was observed in the case of PEDV and HPAIV.

Link to the full article

Beneficial but variable effect of vaccination to control Salmonella in pigs

In this meta-analysis conducted by the Center for Veterinary Health Surveillance (Madrid, Spain) in collaboration with Drs. Conrado, Perez, and Alvarez from the University of Minnesota, the efficacy of vaccination to control Salmonella infection in pigs was evaluated. The meta-analysis reviewed a total of 44 studies focusing on Salmonella typhimurium or Salmonella choleraesuis. Included protocols were using either inactivated (killed) or live-attenuated vaccines.

Results showed that both vaccine types had a similar efficacy and that the most successful control strategies among the ones reviewed were using killed vaccines to control Salmonella choleraesuis.

Abstract: Consumption or handling of improperly processed or cooked pork is considered one of the top sources for foodborne salmonellosis, a common cause of intestinal disease worldwide. Asymptomatic carrier pigs may contaminate pork at slaughtering; therefore, pre-harvest reduction of Salmonella load can contribute to reduce public health risk. Multiple studies have evaluated the impact of vaccination on controlling Salmonella in swine farms, but results are highly variable due to the heterogeneity in vaccines and vaccination protocols. Here, we report the results of an inclusive systematic review and a meta-analysis of the peer-reviewed scientific literature to provide updated knowledge on the potential effectiveness of Salmonella vaccination. A total of 126 articles describing the use of Salmonella vaccines in swine were identified, of which 44 fulfilled the inclusion criteria. Most of the studies (36/44) used live vaccines, and S. Typhimurium and S. Choleraesuis were the predominant serotypes evaluated. Vaccine efficacy was most often measured through bacteriological isolation, and pooled estimates of vaccine efficacy were obtained as the difference in the percentage of positive animals when available. Attenuated and inactivated vaccines had similar efficacy [Risk Difference = − 26.8% (− 33.8, − 19.71) and − 29.5% (− 44.4, − 14.5), respectively]. No serotype effect was observed on the efficacy recorded for attenuated vaccines; however, a higher efficacy of inactivated vaccines against S. Choleraesuis was observed, though in a reduced sample.

Results from the meta-analysis here demonstrate the impact that vaccination may have on the control of Salmonella in swine farms and could help in the design of programs to minimize the risk of transmission of certain serotypes through the food chain.