Lethargy in pigs and neonatal mortality have been attributed to Senecavirus A

Lethargy in pigs and neonatal mortality have been attributed to Senecavirus A.

Stay vigilant on Senecavirus

As if porcine reproductive and respiratory syndrome and porcine epidemic diarrhea virus aren’t enough for U.S. hog producers to worry about, they now have Senecavirus A weighing on their minds.

Senecavirus A, also known as Seneca Valley virus, has been identified in the United States since 1988. Cases were detected in June and October of 2014, and again starting in March of this year, with spikes in July and September. So far Alabama, Colorado, Florida, Georgia, Hawaii, Illinois, Iowa, Minnesota, Nebraska, North Carolina, Ohio, Oklahoma and South Dakota have identified herds with SVV.

According to Paul Sundberg, executive director of the Swine Health Information Center, there had been about 60 positive cases of SVV reported between June and Oct. 16 through the Veterinary Diagnostic Laboratories at Iowa State University, the University of Minnesota and South Dakota State University. Sundberg presents some caveats around these findings.

“I’m confident that this is under-reported, don’t know by how much,” he says. “These are not necessarily 63 individual farms; these are 63 individual cases.” Even with the potential underreporting, Sundberg says the SVV cases are concerning, considering “historically we’ve had fewer than 10 a year.”

Sundberg says these positive tests have originated at sow farms, nurseries and finishers, as well as some environmental contamination such as truck washes.

“Put this in perspective, though. There is no doubt we have more [positive cases] this summer, but keep in mind how many farms and thousands and thousands of pigs there are in the countryside, and we’ve got 63 positive cases,” he says. “This is not like the PED outbreak of 2013. It’s not anywhere close to an epidemic. There’s an increase in incidence, but we don’t know the prevalence.”

Although there was a spike in positive incidents this summer, Sundberg says the positive cases have dwindled since.

Producers are encouraged to closely monitor their swine herds for:

■ vesicles and coalescing erosions on the snouts and coronary bands

■ acute lameness in a group of pigs

■ ulcerative lesions on or around the hoof wall

■ anorexia, lethargy and/or febrile (In the early course of the disease, fevers up to 105 degrees F have been reported.)

If you see such signs, you are asked to immediately contact your herd veterinarian, who in turn needs to contact the state or federal animal health official. “That state or federal official will determine what steps need to be taken,” Sundberg says.

Though the presence of SVV on a farm isn’t good, it is imperative that proper procedures are followed to eliminate what is not present, since the symptoms listed above are also consistent with foreign animal diseases including foot-and-mouth disease, vesicular stomatitis and swine vesicular disease.

FMD has not been in the United States since 1929, but if found in the U.S. swine herd, it would be devastating to the industry.

Dustin Pendell, a Kansas State University economist, led recent research using a simulation model showing the impact of a potential FMD outbreak. According to a press release from K-State, “Although it is not a human health or food safety threat, FMD could lead to significant economic losses from depopulation of infected or potentially infected livestock and trade shutdowns.”

The release says, “Pendell used output from FMD spread models to examine the economic impact of an outbreak under 15 different emergency vaccination strategies in the U.S. Midwest. The models included economic linkages from different species of livestock and crop production all the way to the final consumer, including international trade partners.

“If an FMD outbreak were to occur in this region and no emergency vaccination program was implemented, the research found estimated losses to producers and consumers at approximately $188 billion and additional government losses at $11 billion due to controlling livestock movement and depopulating infected livestock.”

The release said that if an aggressive vaccination program were used, that financial impact could be reduced to $56 billion for producers and consumers and $1.1 billion in governmental costs. Those figures spell out the importance of making sure symptoms truly do present SVV and are not FMD.

A full report on Pendell’s work can be found online at agmanager.info/livestock/marketing/AnimalHealth/FMD_Vaccination.pdf.

Don't be 'the one'

With that in mind, “you don’t want to be the one to have FMD on your farm that could be detrimental to the industry,” Sundberg says.

If suspicious lesions or blisters are found on pigs, and the proper state or federal animal health officials have been notified, a foreign animal disease investigation will be initiated. An FAD diagnostician will take samples from the lesions or blisters to be tested at a state laboratory that is part of the National Animal Health Laboratory Network. Another part of the same sample will be sent to Plum Island Animal Disease Center in New York. Results from the NAHLN could come back quickly, and if FMD is not detected, the hog producer can proceed as normal, within reason. “If there are lesions or blisters, let them heal before shipping the hogs to market,” Sundberg says. “If there are scabs, contact your packer to inform them of the situation.”

Sundberg advises to follow the directions of the state or federal animal health official about movement of people and animals while waiting for the results to come back from the lab. “We are talking with USDA, APHIS [Animal and Plant Health Inspection Service] and FSIS [Food Safety and Inspection Service] about timing,” he says. “Turnaround time is critical; it needs to happen as quickly as possible so the producer can go about business as usual. If it is delayed and becomes a bad experience, then we could get into a spot where the producer won’t report it because they assume it’s SVV and they don’t want to put up with a delay in production.” Sundberg says currently the NAHLN results are expected to be returned within 24 hours. Results from the Plum Island laboratory may take longer, but Sundberg says history has shown the Plum Island results confirm the NAHLN lab’s results.

If a producer ships affected animals with visible signs to market, that could bring that processing plant to a screeching halt, until test results are confirmed. “Be proactive on this,” Sundberg advises producers. “If you see signs on your pigs, don’t ship them to market before getting a test result and letting the lesions heal.”

Where did it come from?

Confirming that a farm has SVV and not FMD does not answer the question of why SVV is occurring at the rate that it has been.

Brazil experienced an SVV spike during its last summer (our winter), and Sundberg says that virus and the virus found in U.S. pigs appear to be closely related, and a parent virus probably was in Canada at some point. “What’s interesting is that this virus sequence is different than the historical virus sequence,” he says. “It appears to have started to change in 2011, but why did it change?”

Best theories point to some stressor or cofactor that may be related to SVV causing clinical lesions. Sundberg says some pigs in the countryside that have SVV appear normal, while others show the lesions and blisters, and researchers are trying to find out why it presents differently. “Some feel transportation could be a stressor, and we don’t know about other infectious cofactors, but it will be investigated … there is much more that we don’t know than what we do know, but we’re trying to figure it out,” he says.

To go along with the varied appearance, Sundberg says there is also a wide range of clinical presentations, ranging from 5% of the herd affected and the pigs recover within 10 days, up to 80% of the herd affected, with SVV going through the herd and taking up to three weeks to resolve.

Neonatal impact

A recent report from the Veterinary Diagnostics Laboratory at Iowa State University highlighted that SVV has been attributed to neonatal mortality.

The neonatal losses syndrome affected pigs of 0-7 days of age. Piglets of 0-3 days of age had a high fatality rate (40% to 80%). Piglets from 4-7 days of age showed a moderate fatality rate (0 to 30%). Affected sow farms had a sudden onset (increase) of neonatal mortality and recovered to baseline mortality levels within four to 10 days. Because of those characteristics, this syndrome has been referenced as epidemic transient neonatal mortality.

The ISU VDL continued, “At this point it is not completely understood how Senecavirus A disseminates between pig populations. There were a few affected breeding herds that were relatively well isolated, without recent history of animal introduction (i.e., closed for at least 180 days), which suggests that epidemic transient neonatal losses were transmitted by routes other than pig movement.

Senecavirus A is another example that the livestock industry must be prepared for pathogen and disease emergence. Strict biosecurity measures must be implemented at all times, regardless of the farm health status. In other words, herds that are ‘already’ positive for PRRSv or Mycoplasma or influenza are ‘still’ free of many other infectious agents and should implement all applicable biosecurity practices 7/24/365.”

The entire column on the ISU VDL report, which appeared in a National Hog Farmer Weekly Preview newsletter in September, can be found at nationalhogfarmer.com/health/senecavirus-impacting-neonatal-mortality.

SHIC has funded research with ISU, U-M and SDSU to gather more information on SVV, with results coming in mid-November. Research results will be available on the SHIC website, under the Research tab.  

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