Bovine tuberculosis is a chronic proliferative enteritis caused by Mycobacterium tuberculosis, which is distributed worldwide and is one of the most common chronic infectious diseases in cattle farms. After the outbreak of this disease, chemotherapy has no effect, so farmers can only strengthen prevention and control measures to reduce losses.
First, the pathogen
Bovine paratuberculosis is caused by Mycobacterium tuberculosis. This pathogen is similar to Mycobacterium tuberculosis and has anti-acid staining properties, no movement, no capsule, no spore, and Gram stain. This kind of pathogen mainly exists in the intestinal mucosa and intestinal mucosal lymph nodes of sick animals, and is discharged through feces. It is more resistant to external factors and has a greater impact on the surrounding environment. It can survive for months to a year in pastures and soil contaminated by sick cattle and can survive for 125 to 246 days in feces. Very resistant to disinfectants. It is easy to kill the bacteria by heating, and it can be killed in the environment of 65 °C for 30 min or 80 °C for 1~5 min.
Second, epidemiology
Paratuberculosis is mainly caused by cattle, especially cows, and occasionally in sheep, goats, pigs, horses, camels and deer. The main source of infection is sick animals and a large number of pathogens are continuously or intermittently excreted from the feces. Since the bacteria can survive for a long time in the outside world, they can be infected through the infected digestive tract through the infected pasture, forage and water. Pathogens are found in the blood of some sick animals and can be excreted with milk and urine. The disease can also be transmitted through the reproductive system. When the cow is infected, the uterine infection rate is above 50%, and the cow can be transmitted to the calf through the uterus. Paratuberculosis is sporadic or endemic. Young cattle are most susceptible to infection and have a long incubation period after infection, some even up to 12 months, often until 2 to 5 years old. Cows are also susceptible to infection at this stage due to lower body resistance during pregnancy, childbirth and lactation. In the same feed, the lack of minerals and the high density of feeding can cause the immunity of the cattle to decrease, which causes the disease to occur.
Third, the symptoms
There was no obvious clinical response to the normal mental, appetite and body weight at the beginning of the disease. In the early stage of the diseased cow, intermittent diarrhea develops into intractable diarrhea. The feces are thin with bubbles and mucus, and are often discharged in a spray form with malodor. As the disease progresses, the diseased cows become worse, their appetites are reduced, they become thinner, their bones are prominent, their skin is rough, their anemia, their eyes are sunken, their lactation is reduced or even stopped. A thick intestinal bowel can be touched during a rectal examination. A cow with a long course of disease will be light and heavy, and sometimes diarrhea will increase after it stops. Usually 3 to 4 months will die and some will be delayed to 3 to 5 years.
Fourth, pathological changes
The lesions are mainly in the intestinal and mesenteric lymph nodes, especially the changes in the ileum. The length of the intestinal tract is different, but it is mainly manifested in the thickening of the intestinal mucosa, and the formation of hard and curved folds into the cerebral gyrus; the intestinal mucosa is gray. Yellow or yellowish white, pleated bulge is often congested, mucus is attached to the mucosa; the lymph nodes of the intestine are swollen and the cut surface is moist. In some cases, the true stomach and rectum also have obvious lesions.
Fifth, diagnosis
The diseased cow can be initially diagnosed according to the clinical symptoms and pathological changes of the diseased cow. Bacteriological and allergic reactions can be used to examine them if necessary. The clinical manifestations of sick cattle are mainly manifested in persistent sputum with stench, mixed with bubbles and mucus. Progressive wasting and anemia occur, and some subcutaneous edema will occur. The small intestine, especially the ileum mucosa, is highly hypertrophic, forming obvious cerebral palpebral folds; mesenteric lymph nodes, lymphatics. Pathological biopsy revealed intestinal mucosal epithelial hyperplasia and macrophage infiltration. Bacteriological examination of sick cattle is carried out where necessary. Scrape the rectal mucosa, fecal mucus or take the smear of the dead or dead cows directly into the smear or smear after culture, and then perform microscopic examination after acid-fast staining. For a diseased cow that has no clinical symptoms or is not obvious, avian tuberculin can be used for quarantine.
Sixth, prevention
1, must pay attention to the ratio of feed, especially to the young cattle to give enough nutrition, can effectively improve their autoimmune disease resistance.
2. In the introduction of breeding cattle, it is necessary to choose from healthy cattle to prevent the purchase of sick or hidden cows. After purchasing cattle, it is still necessary to isolate and quarantine. It is necessary to confirm the breeding of the cattle before they can be mixed into the herd.
3, found in the herd of diarrhea cattle and long-term cure must be carefully examined, if necessary, take bacteriological examination or allergic reaction to determine whether the diseased cow has tuberculosis, if it is determined to have this disease should be eliminated in time.
4. In the area where the outbreak has occurred, regular quarantine must be carried out on time. The cattle that are infected with this disease and have low economic value should be eliminated immediately. For cattle houses, cattle pens, and pastures, they should be thoroughly disinfected and excrement and bedding should be removed in time. Since the pathogen has strong resistance to the external environment, it is necessary to put the sterilized cow house for 1 year before using it.
5. For the diseased cattle with higher economic value, they are treated with drugs under isolated conditions. At the same time, the feed should be adjusted to the high-quality grass of the diseased cattle, and the minerals should be supplemented to improve the immunity and recovery of the cattle.
6. The calves born in the sick cattle should be separated from the cows in time, and they should be fed artificial milk or sterilized milk after 3 to 5 days of artificial breast milk feeding. In the first, third and sixth months, avian tuberculin was quarantined once. Negative reactions are transferred to putative healthy herds for feeding. Positive reactions are placed in the diseased herd for rearing or elimination.
If the cow is sick or not, it will affect the economic benefits of the farmer. Therefore, the farmer should do daily management work and feeding work to prevent the disease from happening.
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