Eradication Project of Bovine Mycoplasmosis in New Zealand

Post date:2019.06.19

To eradicate one infectious disease, which has occurred in one country, huge money and time are needed. And many failed cases have been shown throughout human history amidst the great effort to resolve it. To make these projects a success, a clear scientific evidence, well-prepared plans, and ample funds are essential. Also, the characteristics of the pathogens must be considered. Thus, if the government decides to take actions, it must be prepared to take a risk.

According to the Nikkei newspaper on May 29, 2018, the government in New Zealand (NZ) planned to slaughter Mycoplasma bovis infected cows to stamp out Bovine Mycoplasmosis in NZ. At least 128.000 cows were estimated to be the targets, and the government has planned to invest 886.000.000NZD for 10 years. The infection of M. bovis has been expanding since an infected cow had been found at Canterbury region in south NZ on Sept., 2017.

About 10 species of Mycoplasma are involved in the infection of cows, and M. bovis is considered to induce it mostly. The symptoms are pneumonia, middle otitis, arthritis, and mastitis, which is becoming a problem in recent years. Basically, it is difficult to treat it by antibiotics once cows develop it. In addition, it shows high fixation on some organs and can transfer to various tissues through the bloodstream. Calves are infected with it among each other, through the environment, by taking infected milk, and through humans. If there is only one developing calf in a herd, it can spread within a week, suggesting that it has extremely strong infectivity. Actually, Mycoplasma spp. can be detected from almost all places in farms, which keep infected cows. The fetal infection was also reported, and Mycoplasma spp. was detected in the brain, lungs, lymph nodes, liver, heart, and placenta of miscarriage fetus. The infection on the fetal period can bring the risk of the development after birth. The government in NZ may embark such bold measures due to those distinctive pathologies of infection.

Only two infectious diseases, smallpox in humans and bovine smallpox, had been already eradicated, even though there are many infections in the world, indicating that it is extremely difficult to destroy living things having the survival instinct. Livestock workers around the world might have been paid attention whether or not this challenge in NZ will become successful. In Japan, on the other hand, the positive rate of Mycoplasma in milk bulk tanks is under 5%. It is not a higher incidence compared with other countries, but the rate has been rising tendency in recent years. It is impossible that the Japanese government act the same measures as NZ, because mycoplasmosis is not designated as monitored infectious disease in the Act on Domestic Animal Infectious Disease Control. Considering the limit of treatment by antibiotics, the development of vaccine seems to be an urgent issue.