Stability of Porcine Epidemic Diarrhea Virus on Fomite Materials at Different Temperatures

Today, we are presenting a paper published by Dr. Maxim Cheeran‘s lab in Veterinary Sciences regarding the stability of PEDV on fomite materials at different temperatures.

The full article is available in open access on the journal’s website.

Porcine Epidemic Diarrhea virus and its transmission

Porcine epidemic diarrhea virus (PEDV) causes highly contagious viral enteritis in swine. In May 2013, a PEDV strain, genetically related to a Chinese strain, was introduced in the US and spread rapidly across the country causing high mortality in piglets. Over eight million pigs were killed during this outbreak, leading to an estimated loss of 1.8 billion US dollars.

Transmission of PEDV primarily occurs by the fecal-oral route, but indirect transmission can occur when an animal comes in contact with inanimate objects (fomites) contaminated with the feces of PEDV-infected animals.


200 μL of virus containing 2.1 × 106 TCID50/mL was applied on various fomite material: Styrofoam, nitrile gloves, cardboard, aluminum foil, Tyvek® coveralls, cloth, metal, rubber, and plastic. The virus-contaminated fomites were then stored at either 4◦C or at room temperature. Samples were then taken at 0,1 2, 5, 10, 15, 20 and 30 days post-contamination to test for virus stability.

PEDV survival on fomites Cheeran et al


Infectious PEDV was recovered from fomite materials for up to 15 days post application at 4◦C; only 1 to 2 logs of virus were inactivated during the first 5 days post application. On the other hand, PEDV survival decreased precipitously at room temperature within 1 to 2-days post application, losing 2 to 4 log titers within 24 h as can be seen on the figure above.

Immunoplaque assay was used to identify positive fomites after 20 days of storage at 4◦C. Immunoplaque assay is much more sensitive than PCR and can detect virus as low concentration as 24 focus forming units/mL. Titers of approximately 1 × 10^3 FFU/mL were observed in eluates from Styrofoam, metal, and plastic, representing a 3-log virus inactivation after 20 days. The surviving virus on Tyvek® coverall and rubber surfaces was moderately above detection limit (24 FFU/mL).


Indirect transmission of porcine epidemic diarrhea virus (PEDV) ensues when susceptible animals contact PEDV-contaminated fomite materials. Although the survival of PEDV under various pHs and temperatures has been studied, virus stability on different fomite surfaces under varying temperature conditions has not been explored. Hence, we evaluated the survival of PEDV on inanimate objects routinely used on swine farms such as styrofoam, rubber, plastic, coveralls, and other equipment. The titer of infectious PEDV at 4 °C decreased by only 1 to 2 log during the first 5 days, and the virus was recoverable for up to 15 days on Styrofoam, aluminum, Tyvek® coverall, cloth, and plastic. However, viral titers decreased precipitously when stored at room temperature; no virus was detectable after one day on all materials tested. A more sensitive immunoplaque assay was able to detect virus from Styrofoam, metal, and plastic at 20 days post application, representing a 3-log loss of input virus on fomite materials. Recovery of infectious PEDV from Tyvek® coverall and rubber was above detection limit at 20 days. Our findings indicate that the type of fomite material and temperatures impact PEDV stability, which is important in understanding the nuances of indirect transmission and epidemiology of PEDV.

Science Page: Geographic distribution and genetic diversity of PCV3 from clinical samples in US swine farms

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week, we are sharing a report by Zhen Yang a DVM/MS candidate at the UMN, regarding the Geographic distribution and genetic diversity of PCV3 from clinical samples in US swine farms.

Key Points:

  • PCV3 is widespread in the U.S.
  • Abortion cases in the study had a high rate of PCV3 positivity.
  • PCV3 found in association with lesions in an abortion case suggesting causality.

The study looked at 730 cases from the UMN Veterinary Diagnostic Laboratory with a positive sample for PCV3, received between Feb 2016 and Jan 2018.

Yang PCV3 US location genetic diversity

Out of 22 states, 18 states were PCV3 positive. PCV3 was detected in pigs from all ages.

The positive rate among fetus, piglets, nursery and finishing pigs ranged from 15% to 20%. The PCV3 rate in adults was 35%.

PCV3/PCV2 co-infection rate was 5.2%, and PCV3/PRRSV coͲinfection rate was 7.6%.

In our data, we had 67 abortion cases, and 40% of them were PCV3 positive. In one abortion case investigation, histological lesions were observed in lung tissue of aborted fetus and PCV3 in-situ hybridization showed presence of PCV3 in the lesion.

Seven PCV3 whole genome sequences were obtained. Current PCV3 genomes in the U.S shared over 98% nucleotide identities. U.S strains did not cluster together and were grouped with PCV3 sequences obtained in other countries.

AASV 2018: A successful meeting in San Diego

The UMN CVM students did a fantastic job at the 2018 American Association of Swine Veterinarians (AASV) meeting last week. Zhen Yang presented an update on his research regarding PCV3 and got the second place in the student oral competition.
Taylor Homann received a prize for her poster presentation. Marjorie Schleper was awarded one of the 10 student scholarships given by Merck Animal Health. Hunter Baldry was recognized for the most downloaded podcast: her interview of Dr. Clayton Johnson.

Dr. Montse Torremorell shared the initiatives undergoing at the University of Minnesota in the honor of Dr. Bob Morrison.

Lastly, Dr. Juan Sanhueza received one award given by Boehringer Ingelheim to advance the research on swine respiratory pathogens for his project: “Evaluation of parity as a delaying factor to reach PRRSv stability in sow farms”. Dr. Perle Boyer received a research grant from the AASV Foundation to develop Day 1 competencies for swine veterinary graduates.

Congratulations to all!

Science Page: Swine Global Surveillance Project: update and future steps

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week, we are sharing an update on the Swine Global Surveillance Project, lead by the Center for Animal Health and Food Safety in collaboration with the UMN Veterinary Diagnostic Laboratory, the UMN swine group and the Swine Health Information Center (SHIC).

 Key Points:

  • It is a public, private and academic partnership to implement a system for near real time global surveillance of swine diseases.
  • The output of the system is a report of hazards identified and subsequently scored that may represent a risk for the US pork industry.
  • Developing systems to provide situational awareness to stakeholders in near-real time can facilitate the coordination between government agencies and the industry with the ultimate objective of preventing or mitigating the impact of diseases epidemics.
  • The reports are available at:

The system of near real time global surveillance of swine diseases is based on an online application.  Initially focused on three main potential
threats: Classical Swine Fever (CSF), African Swine Fever (ASF), and Foot and Mouth Disease (FMD), it will expand to other exotic swine diseases in the US in the near future. A report, distributed on a monthly basis by SHIC, includes a list of identified hazards that may represent a risk for the US.

Swine global surveillance process steps

Several steps are needed to build the Swine Global Surveillance report as shown in the figure above.

  1. Screening/Filtering phase: Multiple official data sources and soft data sources are systematically screened to build a raw repository. After that, an Include/exclude process is undertaken under a crowdsourcing model.
  2. Scoring phase: A multi-criteria rubric was built based on: credibility, scale and speed of the outbreak, connectedness, local capacity to respond and potential financial impact on the US market. Each event is score independently by a group of experts.
  3. Quality assurance (QA)/building: Its aim being to ensure that the design, operation, and monitoring of processes/systems will comply with the principles of data integrity including control over intentional and unintentional changes to information. The monthly report is put into a PDF document automatically from the app after the scoring process is finalized. At last, assembly of figures and proofreading is done before sending it to SHIC for monthly publication.

Next steps

  • Complete automation of event capture into the database
  • Expansion of the list of diseases in the report
  • Shrinking the gap between Search/Filter phase and Final Publication – (1 week)
  • Expanding scoring experts panel
  • Process documentation – Quality assurance compliance

OptisampleTM: Open web-based application to optimize sampling strategies for active surveillance activities at the herd level illustrated using PRRS

This past Saturday during the 49th AASV annual meeting, Dr. Rovira presented OptisampleTM, an online open-access tool to determine sample strategies for disease surveillance.

Did you miss this presentation? Click here to see the schedule of our talks during the 2018 AASV meeting!

Dr. Ana Alba who created this tool published an open-access article on how to use Optisample for PRRS active surveillance.

Several inputs are needed to use this web-based application: herd size, frequency of testing, minimum prevalence to detect…

3 different herd examples are then shown to test for PRRSV surveillance. The input and outputs of those examples are show in the figure below:

If you want to try out OptisampleTM, click here.


Porcine reproductive and respiratory syndrome virus (PRRSv) infection causes a devastating economic impact to the swine industry. Active surveillance is routinely conducted in many swine herds to demonstrate freedom from PRRSv infection. The design of efficient active surveillance sampling schemes is challenging because optimum surveillance strategies may differ depending on infection status, herd structure, management, or resources for conducting sampling. Here, we present an open web-based application, named ‘OptisampleTM’, designed to optimize herd sampling strategies to substantiate freedom of infection considering also costs of testing. In addition to herd size, expected prevalence, test sensitivity, and desired level of confidence, the model takes into account the presumed risk of pathogen introduction between samples, the structure of the herd, and the process to select the samples over time. We illustrate the functionality and capacity of ‘OptisampleTM’ through its application to active surveillance of PRRSv in hypothetical swine herds under disparate epidemiological situations. Diverse sampling schemes were simulated and compared for each herd to identify effective strategies at low costs. The model results show that to demonstrate freedom from disease, it is important to consider both the epidemiological situation of the herd and the sample selected. The approach illustrated here for PRRSv may be easily extended to other animal disease surveillance systems using the web-based application available at

Science Page: Influenza herd-level prevalence and seasonality in Midwestern sow farms

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week, we are sharing a report from Dr. Fabian Chamba regarding influenza herd-level prevalence and seasonality in the Midwest.

Key points:

  • Influenza is endemic and seasonal in piglets from sow farms in the Midwest with higher infections in winter and spring.
  • Influenza seasonality was partially explained by outdoor air absolute humidity and temperature trends.
  • Influenza genetic diversity was high and co-circulation of more than one genetically distinct virus was common.

To study influenza levels over time and its seasonality, monthly testing data of piglets at weaning from 34 sow farms during ~5 years were analyzed.

There were 28% of positive submissions with a median influenza herd-level prevalence of 28%. Genetic diversity was significant with 10 genetically distinct clades of contemporary US swine influenza viruses as shown below. Furthermore, 21% of farms had 3 genetically distinct viruses circulating over time; 18% had 2, 41% had 1 and 20% had no isolates available.

In summary, influenza herd-level prevalence in Midwestern sow farms had a seasonal pattern with higher levels in winter and spring. This is important to better allocate influenza control strategies such as vaccination in sow farms. Influenza seasonality was partially explained by outdoor air absolute humidity and temperature although other factors such as immunity and new introductions may play a role in the observed seasonality.

Read the full story at