Mycoplasma pneumonia is caused by Mycoplasma bovis. It can also cause otitis media, arthritis and mastitis. It is often difficult to diagnose because animals may show different symptoms when infected. However, it is a major cause of otitis media, so if calves show signs of ear infections, such as tilted heads or drooping ears, their chances of being infected by Mycoplasma bovis are quite high. This microorganism is being actively studied because there are still many unknown factors about how it causes disease, how it spreads in animals, and how it spreads between animals.
Mycoplasma bovis is highly contagious and can be spread through respiratory aerosols, respiratory secretions, nose-to-nasal contact, feed, water, bedding materials, feeding equipment and workers. If Mycoplasma bovis is spread in dairy herds, then close to 100% of calves will be infected. However, they may not develop clinical disease or show signs of birth disease. In a population of healthy calves that have not experienced environmental stress, Mycoplasma bovis can be cultured from the lungs of up to 7% of calves. The highest incidence is usually the calves that live in groups, which are under environmental pressure, especially cold stress factors.
This microorganism has many properties and can invade tissues, cause infections and cause clinical diseases. It can easily attach to the mucous membrane of the respiratory tract. This is why calf pneumonia caused by mycoplasma is usually the most common disease. It can also spread through the blood from the lungs to other parts of the body, such as joints. Animals with subclinical infection act as a new source of infection, and the microorganisms can be discharged into the environment for many years without developing into clinical diseases. This excretion may be continuous or intermittent. Animals with clinical symptoms of disease will release large amounts of mycoplasma into the environment.
Path of infection
Animals as subclinical carriers keep mycoplasma stable in cattle by continuously releasing mycoplasma into the environment. Animals suffering from chronic respiratory diseases will excrete a large number of bacteria, increasing the incidence of respiratory diseases, especially in crowded enclosures. The continuous excretion of mycoplasma makes it almost impossible to eliminate the microorganism from the environment.
Newborn calves can easily become infected in the delivery room through contaminated bed rest, low-quality ventilation, and sterile cows. Mycoplasma bovis can be cultured directly from the air in the calf barn and is an important source of infection for newborn calves. In the past, mycoplasma was considered to be a rather fragile microorganism, unable to survive for a long time outside the body due to the lack of cell walls. However, recent studies have shown that mycoplasma can survive in the environment for a long time, especially in a cool and humid environment. A published study showed that Mycoplasma bovis survived in recycled sand bedding for more than 6 months.
Mycoplasma has many virulence factors, making it easy to cause animal infections and cause diseases. As mentioned earlier, it has the ability to adhere to the upper respiratory tract mucosa, invade tissues and reproduce rapidly. In order for the immune system to respond to invading pathogens, it must recognize certain antigens (usually located on the surface of the pathogen). Mycoplasma has the ability to change or modify these antigens, so the immune system must restart to produce antibodies against these new antigens. Mycoplasma can also produce a "biofilm" on the surface of the tissue to protect it from the animal's immune system. As mycoplasma grows, it can produce metabolites that are toxic to the tissue it infects.
Mycoplasma bovis is often grown from the lungs of animals infected with other pneumonia pathogens. Mycoplasma was isolated from 82% of cases of Mannheimia hemolytic pneumonia. It can also be isolated from cases of pneumonia caused by histotrophic bacteria and Pasteurella multocida. A general theory is that mycoplasma invades lung tissues and causes lung inflammation, which in turn makes animals susceptible to infection by the above-mentioned pathogens, which can quickly cause serious diseases.
When Mycoplasma bovis causes an infection in an animal, an antibody response alone usually does not cure the infection. Since Mycoplasma bovis can change the immune response, it has a strong tendency to develop into a chronic infection. Infected animals require multiple treatments and often become permanent "weak" in the group. A large part of these animals must be eliminated from the herd.

Early diagnosis and treatment is essential

It is extremely important to detect and treat new cases of mycoplasma pneumonia as early as possible. A large part of the antibiotics used in cattle farms work by inhibiting cell wall synthesis, and because mycoplasma has no cell wall, it will not work on it. Once Mycoplasma is diagnosed, it is important to develop an effective treatment plan, using specific antibiotics that are effective for Mycoplasma bovis.
Studies have shown that oxytetracycline, spectinomycin, florfenicol, turramycin, and gamidycin can effectively treat primary Mycoplasma bovis infection.
Record the calf's body temperature when appetite decreases, runny nose, watery eyes, drooping ears, or increased breathing rate. Immediate treatment with appropriate antibiotics is necessary to eliminate the infection before the cattle become chronically infected. On a cattle farm with a very high incidence of pneumonia, it may be worth checking the temperature of all calves in a specific age group with the highest incidence of pneumonia. Before any clinical symptoms of pneumonia are observed, it is common for body temperature to rise, and treatment at this time will greatly increase the chance of a cure for mycoplasma infection.
It is important to continue treatment until the animal has fully recovered from the infection. The plan should include appropriate antibiotics, course of treatment, route of injection, and withdrawal time after treatment.
Reduce exposure
The key to preventing and controlling pneumonia caused by Mycoplasma bovis is to reduce animal exposure to this microorganism. After the calf is born, the calf should be taken out of the delivery room as soon as possible and placed in a separate enclosure that has been cleaned after the previous calf was born. Using a separate calf pen to prevent nose-to-nose contact between calves will greatly reduce contact infections. If possible, prevent contact between the fence and the fence. This is especially important in ward pens, which should not be in contact with uninfected calf pens.
The stocking density of group feeding pens also plays an important role in the spread of mycoplasma. Ideally, each calf in the enclosure should have at least 28 square feet of space. Overcrowded enclosures will lead to more direct contact and increase the density of mycoplasma in the air, greatly increasing the chance of infection of the calf.
Proper ventilation of the calf barn plays a vital role in preventing and spreading calf pneumonia. Dr. Ken Nordlund of the University of Wisconsin has done a lot of work on the ventilation system of the calf barn. This has had a significant impact on the industry, greatly reducing the incidence of calf pneumonia. Good ventilation will greatly reduce the concentration of pneumonia pathogens in the air and reduce exposure. To
Large-scale dairy farms and calf farms that can quickly fill up the calf barn within a week or two have reduced the incidence of pneumonia by implementing the "all-in, all-out" management method. In this case, the calves stay on the specific calf island until they are all weaned, ready to move out to the first herd cattle barn. This prevents the introduction of new animals into the calf herd, thus preventing exposure to infection.
The sanitary conditions such as feeding utensils, buckets, stomach tubes, feeding bottles, and calf islands are extremely good, which can significantly reduce the chance of calves being exposed to pneumonia pathogens. When treating sick calves, workers should wear gloves and change gloves between calves. Calves should be treated after feeding to prevent pathogens from being transmitted to healthy calves through feeding after treatment of sick calves. In large dairy farms and calf farms, it is best to have a separate team that is not involved in feeding and is responsible for the treatment of sick animals. To
Since Mycoplasma bovis can also cause mastitis in dairy cows, unpasteurized colostrum or milk from cows infected with Mycoplasma bovis should not be given to calves. Colostrum should be pasteurized at 60°C for 60 minutes. There are good commercial pasteurizers that can be used for the pasteurization of bovine colostrum, which can maintain the correct temperature, circulate the colostrum to ensure uniform heating, and then cool the colostrum after pasteurization. High-temperature instant pasteurizers are more common in the processing of large amounts of colostrum.
Dairy farms known to have mycoplasma mastitis should identify infected cows and it is best to remove them from the herd. For cattle farms that have serious problems with mycoplasma mastitis in adult animals, even if pasteurization is used, it is difficult to make good progress in reducing the incidence of mycoplasma pneumonia in calves.
Cattle farms should set up a good biosecurity plan to prevent diseases from being introduced from outside or spreading within the cattle farm. Serological testing can now identify whether a cow is positive for Mycoplasma. Some cattle farms that have adopted this test have realized that most of the cattle they introduced to cattle farms have been exposed to Mycoplasma bovis, so the importance of combining biosafety and other preventive measures is particularly emphasized.
Ear tissue sampling is a good procedure to identify and eliminate any persistent bovine viral diarrhea (BVD-PI). There are also some tests that can be carried out on large cans of milk, which are very sensitive and can detect a BVD PI cow in 3000 animals. The BVD virus has an immunosuppressive effect, and it is very common to increase the incidence of respiratory diseases in cattle herds with BVD-PI animals.
The importance of nutrition and environmental factors to the immune system
Good nutrition is absolutely necessary for the normal functioning of the animal's immune system. Unfortunately, calves are often fed insufficient milk, preventing them from gaining weight based on their genetic potential. Insufficient nutrient intake also prevents the immune system from obtaining the necessary nutrients in order to produce an effective immune response to invading pathogens. Calves should consume at least 20% of their birth weight every day to achieve the nutrient intake required for growth and maintain a healthy immune response.
We usually see an increase in calves' respiratory diseases during and after weaning. Calves are usually suddenly reduced in milk, and they are expected to get enough energy and protein from low-protein calf diets and low-quality hay. A good weaning plan requires the calves to gradually complete the transition while feeding enough nutrients to maintain a stable growth rate.
Cold stress is one of the important factors that increase the incidence of mycoplasma pneumonia in dairy cows. Spreading thick straw on the calf island is one of the best ways to alleviate the cold stress of calves. The straw mat should be deep enough so that the calf is not visible when lying down. In addition, using a calf vest in the first 30 days after birth helps calves maintain their body temperature and reduces the loss of body heat in cold weather. The calf island door should be placed in a place where there is little air and severe convection.
The wet straw cushion in the calf island will cause bacteria to multiply and produce ammonia, which will stimulate the calf's respiratory tract and make it susceptible to respiratory diseases. This is also suitable for group feeding fences. Wet wood chips, wood shavings and straw provide a good environment for bacterial proliferation and ammonia production. To
Mycoplasma pneumonia is a common problem on dairy and calf farms. Facility design, ventilation, sanitation, nutrition, stress management, early disease detection and treatment, and biosafety are all important aspects of prevention and control programs to reduce the incidence of mycoplasma pneumonia in dairy cows. A good prevention and control plan can lead to a healthier reserve herd, increased daily gain, and higher milk production after entering the lactation period.