22 The Business of Canadian Hog Farming Better Pork | February 2024 In the last issue of Better Pork, we discussed how some Mycoplasma bacteria can cause lameness. Today, we are exploring a different species, Mycoplasma hyopneumoniae or M. hyo for short, that causes respiratory disease. As a review, Mycoplasma is a group of bacteria that are very small and lack the cell wall that is present in most types of bacteria. As the name might suggest, Mycoplasma hyopneumoniae (M. Hyo) causes pneumonia, often termed “enzootic pneumonia”. This term comes from the fact that M. hyo typically moves slowly throughout a herd and is difficult to get rid of once it is established in a barn. Pigs may continue to carry the bacteria and cause occasional “flare ups” in affected farms. In other words, it becomes “enzootic”, which is the animal equivalent of the human term “endemic”. Uncomplicated infection On its own, Mycoplasma hyopneumoniae typically causes a mild dry, non-productive cough, “thumping”, difficulty breathing and/or a rapid respiratory rate. It can also cause reduced feed efficiency, slower growth and poor uniformity in a pig herd. Mortality rates are usually low in uncomplicated infections. Disease associated with M. hyo is most common in grower or finisher pigs over about three months of age due to its long incubation period. It usually takes about two to three weeks for exposed pigs to begin to show clinical signs. M. hyo typically spreads slowly from pig to pig through direct contact or through the air. Complicated infection While infection by itself is often mild, M. hyopneumoniae predisposes pigs to secondary infections with other pathogens (viruses and bacteria). It infects and damages cells in the airways that are normally responsible for shunting debris and pathogens out of the lungs. This makes the pig much less able to fight off other bacteria and viruses. Therefore, “co-infections” of M. hyo with other respiratory pathogens are very common. Cases of M. hyo that are complicated by other bacteria or viruses may come with additional symptoms such as a productive (“wet”) cough, fever, depression and increased mortality. Many external factors can also increase the severity of Mycoplasma pneumonia. These include poor air quality, overcrowding, cleanliness of the barn and whether the barn is all-in-all-out or continuous flow. Some strains of M. hyo also cause more severe disease than others. Diagnosis If Mycoplasma is suspected, your veterinarian may want to perform a necropsy/post-mortem examination on a few affected pigs to see if there are signs of pneumonia in the lungs. Some abnormalities associated with M. hyo are collapsed areas of purple or red lung tissue and enlarged lymph nodes in the chest. Regular bacterial culture may not show Mycoplasma as a culprit in a case of pneumonia because it takes a very long time to grow. Therefore, PCR testing is another option that your veterinarian may use to more quickly identify whether Mycoplasma is present in affected pigs. Some samples that can be used to test for M. hyo are lung and airway tissue and respiratory secretions in the trachea or nose. Serology, or the measurement of antibodies against Mycoplasma in the pigs’ blood, may also be helpful. These tests can have a high rate of false negative results but a low rate of false positives. This means that they are most MYCOPLASMAL PNEUMONIA Mycoplasma hyopneumoniae has a big impact on the swine industry. By Hayley Bowling HERD HEALTH Mycoplasma hyopneumoniae causes pneumonia or inflammation in the lungs. Note the affected areas of dark purple lung surrounded by more normal areas of light pink lung. Dr. Jessica Law photo
RkJQdWJsaXNoZXIy NTc0MDI3