No hog in the United States has been diagnosed with the Novel H1N1 2009 influenza virus — at least not at the time of this writing. However, it would be naïve to think that will remain the case.
“As the virus reaches deeper into the human population, it would be very unlikely for it not to reach the pig herd,” says Liz Wagstrom, DVM, assistant vice president of science and technology with the National Pork Board. “We need to prepare that there will be positive pigs.”
Given the $1.256 billion loss that the Novel H1N1 virus is projected to have on the U.S. pork industry by year’s end, the thought that any pig could test positive is chilling. It’s certainly understandable that you might have some uneasiness about how a herd and the producer would be affected; after all, the first positive herd, identified in Canada, was eventually culled.
While there’s still much to discover about the Novel H1N1 virus’ impact on people and pigs, the Animal and Plant Health Inspection Service has developed “Guidelines for Novel H1N1 2009 Virus in Swine in the United States.” It is a response plan that was pro-duced through the collaboration of industry, animal-health, food-safety and public-health representatives, and has been distributed to state veterinarians, who will oversee it.
“APHIS has been very measured in how it developed the plan. It is a reasonable, workable plan,” Wagstrom says.
In essence, it follows protocols that the industry already practices to address swine influenza viruses currently in the U.S. herd. Canada has implemented a similar plan, and both countries accommodate World Health Organization recommendations.
It’s not a quarantine program, but the APHIS response plan does monitor pig movement. “Currently, if you have a barn go down with influenza, you wouldn’t move sick pigs, so this would be handled the same way,” Wagstrom notes.
If sick pigs need to be moved due to space or other requirements, it will be handled under veterinary supervision to determine how and where to move the pigs. “Through this plan, the producer would work with the state veterinarian through his herd veterinarian,” she adds.
Within the response plan is a surveillance plan that USDA released in July. It is a voluntary program involving three surveillance streams — diagnostic laboratory submissions, sick pigs sampled at first point of concentration and pigs associated with hu- man influenza cases. It requires the producer and herd veterinarian to sign a notice of participation. The goals are to:
Indentify new influenza virus strains that may pose a threat to human and/or swine health.
Develop improved reagents for influenza diagnostic tests.
Indentify influenza viruses against which candidate vaccine viruses are needed.
If a new influenza virus is identified that causes a significant increase in swine-health problems, or causes a significant new public-health threat, USDA and Centers for Disease Control and Prevention will work together to provide additional guidance and policy, and to share influenza viruses between animal-health and public-health authorities for vaccine development.
“This surveillance is not intended to support a regulatory eradication or control program,” APHIS notes. “Instead, it will provide critical information to support the common animal-health and public-health interests in overall influenza planning and preparedness.”
Confirmation of the virus will need to come from the National Veterinary Services Laboratories as they have the polymerase chain reaction tests that can differentiate between “normal” SIV and Novel H1N1, and follow with gene sequencing of the virus. This is necessary because current serology tests cannot distinguish between vaccinated swine, those infected with normal SIV and the Novel H1N1 strain. Specific diagnostic tests to identify the novel strain are still in the works.
Should Novel H1N1 be detected in a U.S. swine herd, the primary goal is to prevent additional spread of the virus to pigs and people, APHIS says. The exact strategies in this effort will be case-specific and involve the producer, the herd veterinarian and the state veterinarian.
Biosecurity is among the strategies, and it includes protocols that the industry uses to address current SIV issues — operating all-in/all-out; controlling animal, people and equipment flow within and between swine facilities; and cleaning and disin- fecting rooms and buildings between pig groups. Influenza A viruses are susceptible to heating, drying and disinfectants. The Environmental Protection Agency has more than 500 disinfectant products registered for use on hard, non-porous surfaces to address these viruses. For an up-to-date list, go to porkmag.com/health.
If hogs linked to a human infection involving SIV, including Novel H1N1, show no signs of influenza-like illness, actions may be limited to enhancing biosecurity to prevent any on-going exposure of swine to the human illness, APHIS notes.
For hogs linked to a human infection that do show signs of influenza-like illness, nasal swabs and/or tissue samples of the animals would be collected and sent to NVSL with the producer’s cooperation and under the supervision of a veterinarian.
If those test samples show no signs of Novel H1N1, the production site can resume normal operations. If tests confirm Novel H1N1, then a state animal-health official will monitor and direct animal movement as needed.
In all cases, contact between sick hogs and people or between sick and unexposed hogs needs to be monitored.
Hogs at concentration points (such as markets and fairs) identified with influenza- like illness upon arrival cannot be unloaded. Hogs exhibiting illness once unloaded will be isolated and held until a veterinarian has determined they’ve recovered or have been tested and found negative. Or, the hogs could be relocated, under a veterinarian’s direction, to an offsite location where they can be isolated, cared for and allowed to recover.
Again, the APHIS plan does not call for quarantines. “Quarantine of a farm would not be necessary or helpful,” says Rodney “Butch” Baker, DVM, Iowa State University and American Association of Swine Veterinarians’ president. “From a public-health standpoint, there would be little or no value in quarantining a farm in the case that Novel H1N1 is discovered in pigs.”
As for a vaccine to protect the swine herd from Novel H1N1 virus, the Center for Veterinary Biologics released the master seed to companies in early August. “It will likely be the end of the year before commercial vaccines will be available,” Wagstrom says. “We don’t know what impact a vaccine would have in terms of protecting the pigs or on consumers’ perceptions.”
The National Pork Board will conduct consumer research this month to find out how consumers would react to Novel H1N1 exposure in pigs and more. “It appears that consumers in Australia and Canada have not been afraid,” Wagstrom notes. “We’re hoping the reaction would be similar here.”
Other points that APHIS addresses in its plan include:
The Novel H1N1 2009 virus is not spread by food, so a person cannot get it from eating pork, pork products or other foods. U.S. and global animal-health and public-health officials want to drive that point home. The Novel H1N1 virus, as with any influenza virus, is a respiratory illness and in no way is spread through pork or any food products.
Clinical signs observed in pigs affected by Novel H1N1 virus are not different from those observed in pigs affected by other influenza viruses commonly detected in swine herds.
At this time, animals (including swine) are not playing a significant role in the spread of the Novel H1N1 virus in the general human population.
USDA operates a food inspection system that ensures the safety and wholesomeness of the U.S. food supply. Existing safeguards and procedures prevent sick pigs from entering the food supply.
For more details on APHIS’ response plan, contact your state veterinarian or state pork producer association. “Based on research with the virus, it has been determined that it is infectious to pigs and will spread if it does get into pigs,” Baker emphasizes.
So, it’s best to be informed and prepared, because it is a matter of when.
Refresh Your Knowledge
While the clinical signs of Novel H1N1 2009 in pigs are unknown, research so far suggests that it will react similarly to normal swine influenza virus — as an acute upper-respiratory disease, with nasal discharge, sneezing and a barking cough. SIV has an incubation period of one to three days, it can infect any age pig, and pigs can shed the virus within 24 hours of infection and for up to 10 days.
Morbidity can run 100 percent, but mortality is seldom an issue and most pigs recover in five to seven days unless secondary infections take hold. If the secondary challenge is bacterial, antibiotics are a treatment option.
In the breeding herd, influenza viruses can affect reproductive performance. A boar’s semen quality and output can decline. A sow’s return to estrus may be delayed, and depending on when in the gestation cycle the sow was exposed, it can negatively affect litter size and piglet viability.
In some cases, sows can abort litters, develop a high fever (105 degrees F or higher) and go off feed. The abortions can reach as high as 10 percent but typically subside in less than two weeks. Milk production in lactating sows can drop, which further challenges litters. However, infected sows develop immunity and pass protection on to litters.
Long term, “we don’t know if it (Novel H1N1) would become endemic or an occasional infection,” says Liz Wagstrom, DVM, National Pork Board’s assistant vice president of science and technology.
Don't Overlook Flu Season
Novel H1N1 2009 has been designated a pandemic and U.S. and global health officials look for a resurgence of the virus this fall and winter as the Northern Hemisphere begins its typical flu season. “It’s certain there will be more cases and more deaths,” says Shin Young-soo, the World Health Organization’s Western Pacific director. As of late August, the WHO reports that the H1N1 influenza virus is responsible for just 1,800 human deaths worldwide.
While everyone is on guard, Ann Moen, an influenza expert with U.S. Centers for Disease Control and Prevention, notes that if current trends continue, it is possible that the Novel H1N1 flu pandemic will not be worse than what occurs during a severe flu season. Among the rea- sons is that it appears to affect younger people who may be better able to fight the illness.
Work is underway to expedite vaccine production for humans and is expected to be available anytime from October to December. Rodney “Butch” Baker, DVM, American Association of Swine Veterinarians’ president, believes the pork industry should be a priority to receive the human vaccine when it becomes available. Of course, many groups will feel the same way.
Access to the seasonal flu vaccine will start this month, and all pork production personnel (including office staff) should get their shots. It appears that the Novel H1N1 virus will require a two-shot vaccination, likely spaced a couple of weeks apart. (To find out more, go to porkmag. com/health.) Put the Novel H1N1 vaccination on your staff priority list as well. Because people may have the virus for 24 hours before feeling symptoms and because it has been mild, “it could be difficult to prevent exposing pigs to the virus,” Baker says.
The important thing is for each farm to develop a plan on how to deal with the impending flu season, review it with employees and implement it sincerely.