Feral hogs present potential disease risk for livestock, people
March 6, 2015
Feral hogs can carry numerous diseases of importance to commercial livestock producers and human health. As the nation's feral hog population increases, so does the rate of exposure to infected hogs and potential for disease transmission. Pathogens of most concern to livestock producers include brucellosis and pseudorabies virus. These pathogens can bring devastating impacts (e.g., decreased production, animal deaths, quarantine) if infections reach commercial livestock operations resulting in economic burdens to producers. Private and governmental agencies are continually collecting samples from feral hogs to monitor for various pathogens.
PRV is a herpesvirus, sometimes referred to as Aujeszky's disease or mad itch. PRV infects the nervous system of livestock, as well as many species of wildlife. In most species, infection rapidly leads to death with mortality rates approaching 100 percent. Only pigs are able to survive an acute infection and are the natural reservoir for the virus. Humans cannot contract PRV.
Brucellosis, also known as Bang's disease or undulant fever is usually caused by the bacterium Brucella suis in hogs and Brucella abortus in cattle. However, feral hogs are capable of contracting and transmitting both pathogens. Brucellosis is primarily a reproductive tract disease that causes abortions, infertility, inflammation of testicles, reduced milk production and lameness. Infected hogs are long-term carriers and can infect wildlife, livestock and humans.
Porcine Reproductive and Respiratory Syndrome (PRRS)
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The PRRS virus causes late-term reproductive failure and post-weaning respiratory disease in hogs. Transmission occurs through pig-to-pig contact, and some strains can aerosolize over short distances. The virus often is found in saliva, nasal secretions, urine, feces and semen. Indirect transmission can occur through external parasites. No evidence exists that humans can contract PRRS.
Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium Francisella tularensis. In most susceptible mammals, the clinical signs include fever, lethargy, loss of appetite, signs of sepsis and possibly death. Rodents, rabbits, white-tailed deer and feral hogs are capable of contracting and transmitting tularemia. Humans are most often infected by tick bite or through handling an infected animal.
Q fever is an infectious disease caused by the bacterium Coxiella burnetii. This organism may be found in hogs, cattle, sheep, goats and other domestic mammals. An infection results from contact with the milk, urine, feces, vaginal mucus or semen of infected animals. The disease can be tickborne. Humans are vulnerable to Q fever and may exhibit flu-like symptoms if infected.
Yersinia pestis is an anaerobic bacterium that is typically found in rodents. Humans and other mammals that get plague usually have been bitten by a flea carrying the bacterium or by handling an infected animal. Plague killed millions of people in Europe during the Middle Ages. Modern antibiotics are effective in treating plague, but without treatment, the disease can cause serious illness or death.
Population monitoring and research in south-central Oklahoma conducted by the Noble Foundation demonstrated the following feral hog exposure rates to these diseases: pseudorabies – 22 percent, brucellosis – 0.7 percent, PRRS – 0.3 percent, tularemia – 20 percent, Q fever – 3.4 percent, plague – 1.4 percent. The rates reflect the percentages of 283 animals tested with antibodies to these diseases detected in their blood.
Although most of these exposure rates are relatively low, it is important to exercise caution when handling feral hogs. Hunters that bag a few hogs a year may never encounter an infected animal in their lifetime, while trappers may catch enough animals to encounter one per month. Hunters and trappers should always wear gloves when handling feral hogs and cover any open cuts, scrapes or other wounds. Feral hogs can be excellent table fare, but when cooking wild pork for dinner, be sure to raise internal meat temperature to 165 F.
Some of the aforementioned diseases are of little concern to human health but are of a great concern to the health of livestock and wildlife. Prohibiting relocation of infected feral hogs to new areas is important for controlling the spread of livestock diseases. Additionally, the practice of providing small water points or supplemental feed for wildlife or livestock may increase the risk of transmission by concentrating other animals and feral hogs at these sites.