0806 PD: Mycoplasma in young dairy calves

Craig Jones Published on 07 August 2006

Diseases caused by mycoplasma continue to emerge and remain frustrating to all segments of the dairy industry. In cows, several species of mycoplasma can cause mastitis, pneumonia, arthritis, abortion, and other disease syndromes. Mycoplasma bovis is the most common cause of mycoplasma mastitis and is one of the leading causes of contagious mastitis. In young stock, mycoplasma may cause a variety of disease syndromes as early as two to three weeks after birth.

Mycoplasmas are the smallest, free-living organisms known to cause disease in animals. They are found as part of the normal flora of the upper respiratory tract of healthy cattle. They are unique “bacteria.” They have a very small genome, lack a cell wall and have an exposed plasma membrane on their surface. The lack of a cell wall makes mycoplasmas resistant to certain classes of antibiotics, such as penicillins and cephalosporins, which have activity on the cell wall.



Although Mycoplasma dispar, M. californicum and other mycoplasma species can cause disease in young calves, Mycoplasma bovis is the most common mycoplasma pathogen in young stock. In young dairy calves, mycoplasma can cause pneumonia, conjunctivitis, ear infections, abscesses and arthritis. Mycoplasma is commonly associated with pneumonia as a secondary infection to other viruses or bacteria, but in some cases it may be a primary cause of pneumonia.

Calves may be infected by direct contact with the dam at birth, by ingestion of contaminated milk, through nose-to-nose contact with other calves, by ingestion of the organism from contaminated nipples and buckets and through the environment. Following infection, the organism attaches to epithelial cells lining the mucosal surface, invades the mucosa- utilizing proteins on the surface of the organism and enters the bloodstream.

The organism is spread to various tissues in the body where it may cause disease. Conjunctivitis, head tilts and droopy ears (middle ear infections) are commonly the first signs of a mycoplasma infection in young calves. Often times these are seen in conjunction with, or just prior to, a pneumonia outbreak. In severe cases, the organism may be spread through blood to the joints and result in polyarthritis. In heifers, the organism can spread to the udder, and they may freshen with mycoplasma mastitis.

Treatment of mycoplasma infections in young calves can be frustrating. Treatment should be started early, at the first signs of disease. If treatment is delayed and severe pneumonia, polyarthritis or mastitis results, recovery is difficult and animals may become chronically infected. Due to the nature of the organism, many antibiotics are ineffective at treating mycoplasma. Tetracyclines, tylosin, tilmicosin, florfenicol or spectinomycin may be beneficial. A complete laboratory workup, including isolation of the organism and antibiotic susceptibility testing, can be useful in selecting an antibiotic.

Operations with calves from multiple sources may have several mycoplasma organisms causing disease, and antibiotic susceptibility may vary between organisms. Depending on the antibiotic utilized, treatment should be administered by injectable or oral route to provide antibiotic coverage for a period of 10 days.

Management and biosecurity are keys to the prevention and control of mycoplasma infections in young calves. Tips for preventing mycoplasma include:

1. At birth, feed high-quality colostrum to provide immunity against respiratory diseases and scours. Prevention of these diseases may decrease secondary mycoplasma infections.
2. Do not feed calves milk from known mycoplasma cows.
3. Pasteurize discarded waste milk before feeding to calves.
4. Following birth, minimize contact between cow and calf.
5. Improve ventilation in calf barns.
6. Manage calf housing to provide all-in, all-out.
7. Clean and disinfect hutches or barns between calves or groups of calves.
8. Minimize calf-to-calf contact.
9. Provide a dry environment for calves.
10. Prevent contact between young calves and sick animals. If possible, isolate sick animals.
11. Clean and disinfect pails, nipples, etc.
12. Treat infected calves promptly.
13. Vaccinate against respiratory disease due to other viruses and bacteria. PD

References omitted due to space but are available upon request.

—From 8th National Dairy Calf & Heifer Conference Proceedings

Craig Jones, DVM, MS