Global trends in infectious diseases of swine

Dr. Kim VanderWaal and Dr. John Deen from the University of Minnesota co-authored a new publication available now in the Proceedings of the National Academy of Sciences of the United States of America.

The objectives of this study were to identify priority swine pathogens, characterize temporal and geographic trends in research priorities.

57,471 publications covering 40 swine pathogens, compiled from 3 major database searches and dating from 1966 to 2016 were included in this analysis.

The top 10 pathogens published on were:

  • Salmonella spp.
  • Escherichia coli
  • Influenza
  • Pseudorabies
  • Foot and Mouth Disease
  • Porcine Reproductive and Respiratory Syndrome
  • Classical Swine Fever
  • Actinobacillus pleuropneumoniae
  • Trichinella spp.
  • African Swine Fever

The number of publications on swine infectious diseases increased over time as the hog production intensified. However, 8 pathogens increased faster than expected, particularly in the past 15 years: hepatitis E virus, Nipah virus, influenza, Streptococcus suisLawsonia intracellularis, porcine circovirus 2, PRRS, and PED.

On the contrary, some diseases had a slower growth in number of publications than expected. These included pseudorabies, Pasteurella multocida, Actinobacillus pleuropneumoniae, Brachyspira hyodysenteriae, and transmissible gastroenteritis virus. All of these pathogens were production diseases whose importance to the industry had declined in recent decades due to better control or even regional eradication.

Differences among world regions were identified except for influenza virus which appeared in the top 5 in most regions of the world. Southern regions where extensive hog production may still be the norm, tended to focus more on parasitic infections compared to Northern areas. Western Europe centered more on pathogens related to zoonotic and foodborne concerns compared to Northern America.

Read more about the evolution of publications on swine infectious diseases around the world.

Abstract

Pork accounts for more than one-third of meat produced worldwide and is an important component of global food security, agricultural economies, and trade. Infectious diseases are among the primary constraints to swine production, and the globalization of the swine industry has contributed to the emergence and spread of pathogens. Despite the importance of infectious diseases to animal health and the stability and productivity of the global swine industry, pathogens of swine have never been reviewed at a global scale. Here, we build a holistic global picture of research on swine pathogens to enhance preparedness and understand patterns of emergence and spread. By conducting a scoping review of more than 57,000 publications across 50 years, we identify priority pathogens globally and regionally, and characterize geographic and temporal trends in research priorities. Of the 40 identified pathogens, publication rates for eight pathogens increased faster than overall trends, suggesting that these pathogens may be emerging or constitute an increasing threat. We also compared regional patterns of pathogen prioritization in the context of policy differences, history of outbreaks, and differing swine health challenges faced in regions where swine production has become more industrialized. We documented a general increasing trend in importance of zoonotic pathogens and show that structural changes in the industry related to intensive swine production shift pathogen prioritization. Multinational collaboration networks were strongly shaped by region, colonial ties, and pig trade networks. This review represents the most comprehensive overview of research on swine infectious diseases to date.

Science Page: Illegal importation of meat derived food products through passenger airline carriers and possibility of disease introduction

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 article by the MSHMP team regarding the impact of illegal meat product importation on disease introduction.

Key Points:

  • Commercial airplane passengers bring illegal food imports
  • These illegally imported food products are an overlooked but important disease introduction source
  • The illegal importation by commercial travelers happens more frequently then generally assumed

Illegally imported products are a likely source of disease introduction

The recent African Swine Fever (ASF) outbreaks in China have created concern in the US swine industry over the possible introduction of the disease into the US, thus making Foreign Animal Disease (FAD) a primary topic of concern. One of the most pressing concerns about FADs in general, and ASF in particular, is what are the likely sources of entry, and how the associated risks can be mitigated. Illegally imported products, carried by commercial air passengers are often overlooked as a minor introduction source. Several studies around the world show that commercial air passengers do represent a likely source of disease introduction. Outbreaks of ASF, Classical Swine Fever (CSF) and Foot and Mouth Disease (FMD) have been attributed to feeding imported waste meat to domestic pigs (Falk, et al., 2013).

Thousands tons of illegal food products are found at airports

It is difficult to estimate the total amount of illegal food products entering a single country each year. A study conducted in Germany in 2015 at two major airports tracked seizures for three months, including an intensive 10 days of special controls where higher numbers of passenger luggage was searched. Based upon that data they estimated that each year 2,800 tons of illegal food products were brought in via the Frankfurt airport alone. The most commonly imported foods were meat and meat products, including raw, home cooked, preserved, and packaged foods (Beutlich, et al., 2015).

Another study, conducted in Switzerland estimated that the total volume of non-intercepted meat products were 8.6 tons for bush meat, and 1,013 tons for other meat products (Falk, et al., 2013).

Illegal food products contain pathogens; airports are risky ports of entry

A key point to understand the risk of improperly imported foods is knowing how often they contain pathogens and whether these have the capability of remaining infectious. In the German study, out of 474 samples tested, 5% of them contained food borne pathogens (Beutlich, et al., 2015). In a similar study conducted in Spain 67 out of 122 samples tested at an airport contained human noroviruses, and hepatitis E (Rodriguez-Lazaro, et al., 2015).

A modeling study focused on estimating the risk of introduction of ASF and CSF into the US using airport and customs data. The study identified specific airports (i.e.Washington-Dulles, George Bush-Houston, JFK-Queen, Warwick, Sanjuan, West Palm Beach, Charlotte, Ft. Lauderdale, Newark and Cleveland) as ports of entry with the highest risk for both ASF and CSF introduction. This work also identified the months of May through July as the months with the highest risk (Jurado, Paternoster, Martínez-López, Burton, & Mur, 2018).

Only a fraction of illegal imports are intercepted

It is estimated that only between 10-50% of improperly imported products are intercepted at customs (Jurado, Paternoster, Martínez-López, Burton, & Mur, 2018).One study’s sensitivity analysis showed that for both ASF and CSF, the likelihood of detecting illegal products was highly correlated with the final risk of disease introduction.This means that an increase in customs detection of products brought by commercial passengers largely reduces the risk of a CSV or ASF introduction into the US (Jurado, Paternoster, Martínez-López, Burton, & Mur, 2018).

Pork products were seized recently in the USA and Japan

Recently, on October 15th, 2018 a customs and border protection beagle found a whole roasted pig in the luggage of a traveler from Ecuador(Lieu, 2018) at the Hartsfield-Jackson Atlanta airport. Ecuador as any other South American country is ASF negative, but CSF continues to be present in the country. It is unknown whether the smoked pig has been tested for CSF, but the case is a perfect example of the variety of products that are being transported to the US.

On October 1st, Japanese customs officials confiscated a pork sausage from a Beijing traveler. The sausage tested positive for ASF (Reuters). African Swine Fever has also been found at a South Korean airport in pork products brought in a commercial passenger airline from China (Reuters). All of these examples highlight the reality of the risk illegally imported products carried by commercial travelers play in FAD introduction.

It is important for the swine community to be aware of these risks, to be aware of what food products are being brought to their sites by people, and to push for effective prevention methods. It also highlights the need of the swine community to communicate this risk to the non-swine community to raise awareness and thus contribute to protecting the industry. By using research that helps identify where the highest risks lie spatially and temporally, as well as flights from which countries represent risk, better prevention methods can be developed and implemented.

What if African Swine Fever came to Minnesota?

The Center for Food Animal Health and Food Safety at the University of Minnesota released a new video on African Swine Fever and what the consequences would be if it ever came to Minnesota. Dr. Marie Culhane from the University of Minnesota and Dr. Beth Thompson, executive director of the Minnesota Board of Animal Health discuss how the state prepared for this eventuality.

Click on the video to listen to their exchange. (14:56 min)

 

Best of Leman 2018 series #1: Dr. Noelle Noyes – AMU and AMR: How will we ever understand it?

We launched a new series on the blog last year. Once a month, we are sharing with you a presentation given at the Allen D. Leman swine conference, on topics that the swine group found interesting, innovative or that lead to great discussions.

We can find all of the presentations selected from last year’s conference on the blog here.

Our first presenter to kick off this year’ selection is Dr. Noelle Noyes who recently joined the University of Minnesota to bring her expertise in Antimicrobial Resistance in human and livestock. The Center for Animal Health and Food Safety wrote a great article on how Dr. Noyes plans to bring her research to the farms and help producers solve their issues.

Click on the image below to watch her presentation at the conference:

Noyes Leman 2018 AMR understanding

The effect of season on PRRS time-to-stability in the Midwestern United States

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.

Key Points

  • Seasonal conditions may effect the time to stability of a farm
  • Understanding seasonal effects on time to stability can help producers and veterinarians plan herd closures

This week, we are sharing a report by the MSHMP team in collaboration with Dr. Andreia Arruda from the Ohio State University regarding the impact of seasons on PRRS time-to-stability.

The time needed between an outbreak and consistently weaning porcine reproductive and respiratory (PRRS) virus PCR negative pigs is referred to as time-to-stability (TTS). In this analysis we describe differences in TTS according to the season when the PRRS outbreak occurred in farms located in the Midwestern United States.

161 PRRS outbreaks in 82 sow farms were classified based on the date of the outbreak:

  • March 21st to June 20th: Spring
  • June 21st to September 20th: Summer
  • September 21st to December 20th: Autumn
  • December 21st to March 20th: Winter

TTS was calculated as the time from the reported PRRS outbreak to the time of the last PRRS PCR negative result in wean-age pigs.

A significant difference was detected in TTS among seasons. The median TTS was higher in spring and summer, compared to autumn and winter.

An explanation for the observed TTS difference among seasons may be found in environmental survivability of the virus as for PRRS outbreaks that occur during spring or summer, the last phase of the stability process coincides with the arrival of winter where the reduced ventilation and decreased temperature within the farm may favor PRRS survival resulting on a lower likelihood of elimination during this time.

PRRS time to stability season