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.

 

Torremorell PEDV biosecurity 2017

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.

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

Reducing the likelihood of a piglet reservoir when dealing with influenza in swine herds

Drs. White, Torremorell and Craft from the University of Minnesota recently published an article in Preventative Veterinary Medicine regarding practices that can decrease the likelihood of creating an endemic piglet reservoir in the case of an infection by swine influenza. Indeed, a stochastic model was developed considering that the pigs were in one of the following categories: Susceptible, Exposed,  Infectious, Recovered, or Vaccinated. Loss of immunity over time and differences between naturally infected and vaccinated animals were taken into account. Several scenarios were evaluated regarding their impact on piglet prevalence: timing of gilt introductions, gilt separation, gilt vaccination upon arrival, early weaning, and sow vaccination strategies.

In this model, homologous mass vaccination and early weaning were the most efficacious interventions. By combining frequent homologous mass vaccination, early weaning, gilt separation, gilt vaccination and longer periods between gilt introductions reduced endemic prevalence overall by 51% relative to the null scenario and the endemic prevalence in piglets by 74%.

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Abstract: Recent modelling and empirical work on influenza A virus (IAV) suggests that piglets play an important role as an endemic reservoir. The objective of this study is to test intervention strategies aimed at reducing the incidence of IAV in piglets and ideally, preventing piglets from becoming exposed in the first place. These interventions include biosecurity measures, vaccination, and management options that swine producers may employ individually or jointly to control IAV in their herds. We have developed a stochastic Susceptible-Exposed-Infectious-Recovered-Vaccinated (SEIRV) model that reflects the spatial organization of a standard breeding herd and accounts for the different production classes of pigs therein. Notably, this model allows for loss of immunity for vaccinated and recovered animals, and for vaccinated animals to have different latency and infectious periods from unvaccinated animals as suggested by the literature. The interventions tested include: (1) varied timing of gilt introductions to the breeding herd, (2) gilt separation (no indirect transmission to or from the gilt development unit), (3) gilt vaccination upon arrival to the farm, (4) early weaning, and (5) vaccination strategies of sows with different timing (mass and pre-farrow) and efficacy (homologous vs. heterologous). We conducted a Latin Hypercube Sampling and Partial Rank Correlation Coefficient (LHS-PRCC) analysis combined with random forest analysis to assess the relative importance of each epidemiological parameter in determining epidemic outcomes. In concert, mass vaccination, early weaning of piglets (removal 0–7 days after birth), gilt separation, gilt vaccination, and longer periods between introductions of gilts (6 months) were the most effective at reducing prevalence. Endemic prevalence overall was reduced by 51% relative to the null case; endemic prevalence in piglets was reduced by 74%; and IAV was eliminated completely from the herd in 23% of all simulations. Importantly, elimination of IAV was most likely to occur within the first few days of an epidemic. The latency period, infectious period, duration of immunity, and transmission rate for piglets with maternal immunity had the highest correlation with three separate measures of IAV prevalence; therefore, these are parameters that warrant increased attention for obtaining empirical estimates. Our findings support other studies suggesting that piglets play a key role in maintaining IAV in breeding herds. We recommend biosecurity measures in combination with targeted homologous vaccination or vaccines that provide wider cross-protective immunity to prevent incursions of virus to the farm and subsequent establishment of an infected piglet reservoir.

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Airborne transmission of highly pathogenic avian influenza during the 2015 outbreak in the Midwest

In 2015, the Midwestern part of the United States was the theater of an outbreak of a highly pathogenic strain of avian influenza. Drs. Torremorell, Alonso and Davies from the University of Minnesota were involved during the epidemic and just published in Avian Diseases and their findings concerning the airborne transmission of the virus were just published in Avian Diseases.

The study showed that the air exhausted from an infected poultry facility was a source of contamination for the environment but also a risk of transmission for Highly Pathogenic Avian Influenza (HPAI) that needs to be seriously taken into consideration. Indeed, live and infectious virus was found at a distance up to 70m (76.5 yards) from the farm facilities.

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Abstract: We investigated the plausibility of aerosol transmission of H5N2 highly pathogenic avian influenza (HPAI) virus during the 2015 spring outbreaks that occurred in the U.S. midwest. Air samples were collected inside and outside of infected turkey and layer facilities. Samples were tested to assess HPAI virus concentration (RNA copies/m3 of air), virus viability, and virus distribution by particle size. HPAI virus RNA was detected inside and up to 1000 m from infected facilities. HPAI virus was isolated from air samples collected inside, immediately outside, up to 70 m from infected facilities, and in aerosol particles larger than 2.1 lm. Direct exposure to exhausted aerosols proved to be a significant source of environmental contamination. These findings demonstrate HPAI virus aerosolization from infected flocks, and that both the transport of infectious aerosolized particles and the deposition of particles on surfaces around infected premises represent a potential risk for the spread of HPAI.

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Persistence of Influenza A

Dr. Torremorell, director of the Swine Disease Eradication Center published a new study on the persistence of Influenza A virus in air and on surfaces of swine production facilities.

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Abstract: Indirect transmission of influenza A virus (IAV) in swine is poorly understood and information is lacking on levels of environmental exposure encountered by swine and people during outbreaks of IAV in swine barns. We characterized viral load, viability and persistence of IAV in air and on surfaces during outbreaks in swine barns. IAV was detected in pigs, air and surfaces from five confirmed outbreaks with 48% (47/98) of oral fluid, 38% (32/84) of pen railing and 43% (35/82) of indoor air samples testing positive by IAV RT-PCR. IAV was isolated from air and oral fluids yielding a mixture of subtypes (H1N1, H1N2 and H3N2). Detection of IAV RNA from air was sustained during the outbreaks with maximum levels estimated between 7 and 11 days from reported onset. Our results indicate that during outbreaks of IAV in swine, aerosols and surfaces in barns contain significant levels of IAV potentially representing an exposure hazard to both swine and people.

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