Mainly two types of diseases afflict pigs: enteric diseases and respiratory diseases. Enteric diseases, such as swine dysentery and colitis, cause lack of appetite and diarrhea. Respiratory diseases, such as enzootic pneumonia, infect the pig’s lungs, causing a decline in growth and even death. Not only do these diseases cause the animal pain, but also reduce their value.
The bacteria Brachyspira hyodysenteriae causes swine dysentery (SD) by inflaming the large intestine with bloody diarrhea. Swine dysentery generally doesn’t affect female pigs but can severely affect piglets. Their diarrhea may or may not have blood or mucous in it, and they can begin to waste away. Weaner and grower pigs first show signs of infection when their diarrhea becomes runny and mucus-filled and discolors the skin under their anuses. The affected animal displays a minor reddening of its skin, decline in appetite, tail twitching and poor growth of its flanks. As the disease develops, the pig's feces will turn dark, its face emaciated and sudden death can occur. Pigs contract swine dysentery by eating infected feces.
Both a pig’s nutrition and an infection can cause colitis. Both affect the pig’s ability to digest feed, which results in an inflammation of the large bowel. Colitis does not affect adult pigs and sucker pigs (pigs still suckling who are meant for slaughter) but does infect weaner and grower pigs (pigs fed to be slaughtered) between the ages of 6 and 14 weeks who are fed a high density diet. Symptoms of colitis include: runny diarrhea, dehydration, and meager growth. The death rate of colitis is low.
Though enzootic pneumonia (EP) is widespread among pig populations, it only mildly affects the pig and without serious complications. However, when the animal is ill with another disease, such as actinobacillus pleuropenumonia (App), Pasterurella or the swine influenza virus, enzootic pneumonia can have severe complications. EP infects the lower lobes of both lungs causing heavy breathing, extended coughing, dehydration, fever and respiratory distress after a two to eight week incubation period. This disease affects all breeds and ages of pigs. The transportation of carrier pigs usually transmits the disease to other herds, but when the climate is just right, EP can become wind-borne.