Swine Resources - Diseases

August 2023

Two recent studies on the devastating impact of an African swine fever outbreak in the United States underscore the importance of biosecurity for pork producers.

A May 2023 Iowa State University working paper showed that an outbreak of the disease in the United States would result in as much as $75 billion in losses to the industry, including a cut of 60,000 jobs. Pork prices would plummet between 50% and 60% and stay low for three years.

May 2023

Abstract:

Swine disease elimination programs for Mycoplasma hyopneumoniae are commonly applied in the North American swine industry and may include the aerosolization of medium containing lung tissue to achieve population exposure prior to start. Field data has indicated M. hyopneumoniae PCR detection in pigs beyond 240 days post-herd closure (dphc; planned end of an elimination program) and is thought to contribute to disease elimination programs' failure. Here, the duration of M. hyopneumoniae detection in sows and replacement gilts following aerosolized lung homogenate exposure, as part of a dual disease elimination program, was determined. A subset of sows and gilts from a commercial sow herd and off-site gilt development unit were longitudinally sampled to collect deep tracheal catheter secretions at various times post-exposure. Samples were tested for M. hyopneumoniae using a species-specific real-time PCR. A proportion of 58, 51, 52, 19, and 2% females were detected positive at 30, 60, 120, 180 and 240 dphc, respectively. Noteworthy, a greater proportion of gilts exposed at the off-site GDU were detected PCR positive for M. hyopneumoniae at each sampling event, compared to sows. In this study, assaying for genetic material in live female pigs showed extended detection of M. hyopneumoniae until at least 240 dphc. This data suggests persistence of M. hyopneumoniae longer than previously reported and highlights the importance of performing diagnostic testing to confirm negativity to the bacterium, prior to opening sow herds, especially late in the herd closure timeline.

McDowell E, Pieters M, Spronk T, et al.
Duration of Mycoplasma hyopneumoniae detection in pigs following purposeful aerosol exposure
[published online ahead of print, 2023 Apr 24]. Vet Microbiol. 2023;282:109758. https://doi.org/10.1016/j.vetmic.2023.109758

March 2023

Abstract:

Japanese encephalitis (JE) is an infection that occurs predominantly in Asia and the Pacific Islands. It is transmitted by mosquito bites, with the main vector being Culex tritaeniorhynchus, and is maintained in enzootic cycles involving pigs, wild birds and mosquitoes. JE is caused by infection with Japanese encephalitis virus (JEV), a zoonotic pathogen that also causes disease in mammals such as pigs and horses. In humans, most symptoms are mild or flu-like but can progress to encephalitis. Pigs are considered amplification hosts, and sows may have gestational complications. Horses may exhibit neurological signs. Detection of the virus can be confirmed by serological or molecular laboratory tests. Vaccination offers protection against JEV infection in humans, pigs and horses. Whilst there is no effective treatment of JE, human cases may require hospitalization for supportive therapy, which may include administration of fluids, oxygen and medication to treat symptoms.

Sewgobind S, Johnson N, Mansfield KL. JMM Profile: Japanese encephalitis virus: an emerging threat. J Med Microbiol. 2022;71(12):10.1099/jmm.0.001620. https://doi.org/10.1099/jmm.0.001620

August 2022

Summary

This commentary reviews results obtained in France and North America with different air filtration systems to prevent porcine reproductive and respiratory syndrome virus (PRRSV) infection. Most systems installed in France use high-efficiency particulate air (HEPA) filters and positive-pressure ventilation systems, while those in North America initially used mainly negative-pressure ventilation systems and filters with minimum efficiency rating values of 14 to 16. Major reductions in PRRSV cases were observed in most studies where the latter were used. Installing HEPA filters resulted in an almost complete elimination of PRRSV cases. No cases were recorded in 95% of farms where they were used.

Robert Desrosiers, DVM, DABVP; Vincent Cousin, Agric Eng

Full Article from American Association of Swine Veterinarians

February 02, 2023

For years, researchers have been working to develop a safe, effective, and commercially available vaccine for African swine fever as it continues to spread in Russia and most of Europe and Asia, including China. Millions of pigs have been depopulated around the globe because of this highly contagious, deadly disease that affects both domestic and feral pigs and has no cure. But there is some hope.

Recently, the agriculture secretary of the Philippines, William Dar, said the first trials of an ASF vaccine candidate were being conducted on 10 farms. Vietnam’s deputy minister of agriculture and rural development, Phung Duc Tien, said Vietnam plans to produce and commercialize an ASF vaccine in the third quarter of this year.

In addition, an ASF vaccine candidate developed by researchers at the Harbin Veterinary Research Institute at the Chinese Academy of Agricultural Sciences have reportedly seen promising results in clinical trials conducted on 3,000 pigs.

The successful development of safe and effective modified live vaccines represents a new frontier in protecting swine from African swine fever.

More than 35 countries are now impacted by the disease, including the Dominican Republic and Haiti, which reported their first confirmed ASF cases in 2021. In China, outbreaks since August 2018 have killed millions of pigs, with estimates from the American Society for Microbiology suggesting the losses were as high as 225 million pigs.

The successful development of safe and effective live attenuated vaccines represents a new frontier in protecting swine from ASF.

“Developing a live attenuated virus vaccine is a complex process depending on a variety of factors, and it could take several years to develop and license a vaccine for ASF,” said Christina Lood, senior director of sustainability and innovation communications at Zoetis.

Scientists at the University of Connecticut and the U.S. Department of Agriculture have developed a new ASF live attenuated vaccine. This candidate was licensed for commercial development by Zoetis in September 2019.

Dr. Guillermo Risatti, professor of pathobiology at UConn’s College of Agriculture, Health, and Natural Resources and director of the Connecticut Veterinary Medical Diagnostic Laboratory, collaborated with USDA Agricultural Research Service scientists Dr. Manuel Borca and Douglas Gladue, PhD, to develop the vaccine candidate, called ASFV-G-ΔMGF. The CVMDL is one of UConn Extension’s active service centers that works with federal and state veterinary agencies to enhance disease surveillance and response.

The ARS previously announced in May 2021 that Drs. Borca and Gladue had developed the ASFV-G-∆I177L vaccine candidate. The candidate does not rely on live pigs and their cells for vaccine production, which allows for the production of an ASF vaccine on a commercial scale.

Building on that work, researchers from Zoetis and the Friedrich Loeffler Institute in Germany conducted trials of ASFV-G-ΔMGF, also a live attenuated vaccine in edible bait for wild boars and intramuscular injection for domestic pigs. According to UConn, both routes demonstrated efficacy against ASF.

Lood of Zoetis said the studies demonstrated that this is a promising candidate. She said: “However, more research is needed to better understand safety aspects. Finding the right balance between efficacy and safety is the essential and most challenging aspect of live attenuated vaccines.”

By Coco Lederhouse

September 2021

Summary:

Senecavirus A (SVA) has been demonstrated to be a causative agent for vesicular disease in swine. It is clinically indistinguishable from other agents that cause vesicular disease such as foot-and-mouth disease virus (FMDV), which is a reportable foreign animal disease (FAD). Thus, an investigation is initiated to rule out FMDV every time a vesicle is observed. Senecavirus A has now been reported across the Americas and Asia, and it appears the ecology of this virus has changed from sporadic infections to an endemic disease in some areas. In addition to vesicular disease, there have also been reports of increased neonatal mortality on affected sow farms. Knowledge about the pathogenesis of SVA in swine can provide many benefits to the swine industry. Understanding how long the virus can be detected in various sample types after infection can aide in choosing the correct samples to collect for diagnosis. In addition, the duration of virus shedding can help determine measures to control virus spread between animals. Prevention of SVA infection and disease with an efficacious vaccine could improve swine welfare, minimize SVA transmission, and reduce the burden of FAD investigations.

Full Article

Alexandra C. Buckley, DVM, PhD; Kelly M. Lager, DVM, PhD

January 2022

A resurgence of the F18 strain of Escherichia coli (E. coli) in weaned pigs on a growing number of hog farms is causing a rise in mortality and a reduction in performance, according to Doug Powers, DVM, Four Star Veterinary Service.

October 2021

A U.S. Department of Agriculture–developed vaccine protected pigs against African swine fever in a second study.

September 2021

Last month, the Swine Health Information Center (SHIC) offered a reminder for continued reporting of traveler experiences while going through customs entering the US. That morning, a report of international travelers not being diverted to Customs and Border Protection agriculture specialists for secondary screening after they indicated on their Customs form that they had had animal contact at their African swine fever (ASF) and foot-and-mouth disease (FMD) endemic destination was shared. After getting this report, a Customs and Border Protection contact immediately responded saying, “…flights from that area of the world should be a tactical focus and there will be follow up with the agents at that airport.”

September 2021

Further Mitigation of Feed Import Risks Identified as Priority Area of Focus

Ames, Iowa, Sept. 7, 2021 – A new year-long study to identify U.S. pork industry gaps in biosecurity defenses against foreign animal diseases, funded by the Pork Checkoff and the Swine Health Information Center (SHIC), found no major areas have been overlooked in efforts to prevent the introduction of African swine fever (ASF) to the United States. With ASF confirmed in the Dominican Republic, the first time it has been in the western hemisphere in 40 years, this work provides reassurance the U.S. pork industry and government agencies have identified the major routes of potential domestic introduction. The study, conducted by EpiX Analytics, LLC, reinforced the importance of continued on-farm biosecurity diligence for known pathways and identified feed and feed ingredient imports risks as a critical opportunity to bolster defenses against ASF.