MSU Extension Pork

Any farmer that raises livestock will tell you that one of the biggest challenges is the threat of disease and illness in their herd. Specifically, swine farmers have been very proactive when it comes to managing disease, the implementation of different biosecurity practices to help keep their animals healthy and focus on keeping disease out of their herds. If not prevented, respiratory diseases can affect pig growth rate and lead to variation in market weights, if not managed well. Swine influenza is an example of a respiratory disease that affects all types of production, including commercial herds and exhibition pigs.  

Most often in pork production the concern is with influenza outbreaks during the late fall and winter months of the year but as we approach the mid-summer months in Michigan when we typically have county fairs happening, influenza can become a problem. This happens mainly because some of the strains of the virus are zoonotic and can be transferred between pigs and people.

Swine Influenza in pigs

Swine influenza is a respiratory disease of pigs caused by type A influenza virus, which is routinely dealt with in pork production. Once an outbreak occurs, it is easily circulated throughout the herd. There are various different types and strains of the swine influenza virus, with the most prominent strains in the U.S. being H1N1, H3N2, and H1N2 in recent years. Since swine influenza is a virus, there is no treatment for it. The best and only course of action are preventative measures like vaccination programs and treating the symptoms of the virus.

Although swine influenza can cause high levels of illness in herds, where the infected animal gets pretty sick for a few days, infected animals are expected to fully recover. Signs of swine influenza in pigs are coughing, discharge from the nose or eyes, sneezing, labored breathing, refusal to eat, lethargic and fever. While the normal body temperature of a pig is around 102.5 ^ₒF, fevers associated with influenza can get fairly high from 105-107 °F. Once an animal is infected, the virus must run its course, typically in just a few days and there is no treatment available.

Influenza virus can be spread a few different ways including nose-to-nose contact, from contaminated objects or equipment moving between infected and uninfected animals and from water droplets with virus being expelled into the air from the coughing or sneezing of an animal. Because of the strains of this virus are considered zoonotic and they can be transferred between pigs and people, it is important to take care when around livestock, follow proper biosecurity measures and practice good hygiene.

Influenza in people

People, like pigs, can get influenza and like pigs there are different types of influenza viruses that can infect people. Specific swine influenza viruses do not always infect people, however there have been cases where pigs and people can have common influenza virus types. When this infection occurs the virus is zoonotic and shared between pigs and people. These viruses are called variant viruses and labeled with “v” after the virus type (H3N2v).  

When people become infected with a variant virus of influenza their symptoms are known to mimic those of seasonal influenza and the symptoms expressed by pigs. They may experience coughing, sneezing, feel tired or lethargic, lack of appetite and have a fever. At times they may also have runny nose and eyes, sore throat, vomiting and diarrhea. In most cases, people are expected to fully recover once the virus has run its course. Those with underlying health issues, such as immunosuppression, the very young, the elderly and pregnant women should be cautious when exposed to influenza virus as the effects of the virus may be more extreme in those cases. If you do believe you have been infected with the influenza virus after having contact with animals, it is important to talk to a medical professional. Influenza infections can be confirmed with a simple nasal swab (within 4 -5 days of shedding) and several antiviral medications are available that have been known to shorten the amount of time you are affected.

Variant influenza viruses can be spread from pigs to people and from people to pigs and in some instances from people to people. In most cases, infection occurs after a person has been around pigs, like livestock exhibitions at fairs. Typically, the virus is spread through the air, when a pig coughs or sneezes and expels the water droplets infected with virus. People can also become infected when virus gets on their hands and they touch their mouth or nose. Pigs can become infected from a person carrying the virus and expelling virus particles around the animals.

Like people there are vaccines available for pigs to help prevent influenza infections. The tricky part about influenza in both pigs and people, is when the virus strains are constantly changing and mutating. This means that the vaccines that are available may not directly prevent that particular strain that a population has been exposed to, however just receiving the vaccine will go a long way in decreasing the clinical signs (sneezing and coughing) that are expressed by the animal or person that has been vaccinated. This in turn, will decrease the spread of the disease in both pig and human populations, and when exposed they may only have mild illness or show no signs of infections.

As with any livestock, it is important to practice good hygiene, especially when coming into contact with pigs. People should make sure to wash their hands with soap and water or use an alcohol-based hand sanitizer after coming into contact with animals. They should also avoid eating, drinking or allowing small children to use toys or items, like pacifiers that go into the mouth, in barns or around animals.  Taking the proper precautions when you are around livestock can go along way to prevent illness.  It is also important to understand that people cannot get influenza from eating properly prepared pork products or handling pork, as influenza is not transferred through the meat.