cause of a disease
The pathogen of this disease is Mycobacterium tuberculosis, slender and slightly curved, Gram-positive bacteria, without spores and capsules, unable to move. Generally, acid-fast staining is used, and the bacteria are red. People, birds and cows can all infect cows. Mycobacterium bovis is the most pathogenic to cattle, which often causes typical tuberculosis lesions and death in cattle.
Tuberculosis can be excreted with the gas exhaled by sick cows, including sputum, feces, urine, vaginal secretions, saliva, wound secretions or milk. In most cases, cows get sick by inhaling tiny dust particles containing mycobacterium tuberculosis in the air. It is also common to become infected with mycobacterium tuberculosis through stuttering, that is, through respiratory tract and digestive tract infection. In addition, the risk of diseases transmitted by other animals can not be ignored. Therefore, narrow and crowded pens, poor ventilation, humidity, insufficient light and poor feeding management can all contribute to the occurrence and spread of this disease.
Calves are mainly infected by milk, and their susceptibility to mycobacterium tuberculosis is generally higher than that of old cows, but the prevalence rate of calves is much lower than that of old cows. This is because calves rarely recover from illness, and most of them are old sick cows. Cows are the most common, followed by cattle and yaks.
clinical features
According to different organs, it can be divided into the following categories.
(1) Tuberculosis
The lesions mainly occur in the lungs, and its symptoms are chronic progressive bronchopneumonia. Some are accompanied by pleurisy. If the lesion is mild, the symptoms are not obvious. With the development of the disease, mental deterioration, loss of appetite, emaciation, anemia, dry hair. What started as a brief dry cough gradually turned into a painful purulent wet cough, especially in the morning, late at night, after exercise, after drinking water and when the weather suddenly changed. Some nasal mucus or purulent yellow nasal mucus. With the aggravation of cough, the number of breaths increases and severe asthma appears; Exhaled gas sometimes smells like fish; There are rales and pleural friction sounds in lung auscultation. For example, due to cheese-like changes in lung tissue, cheese-like substances are strongly coughed and discharged, and the lungs form cavities, and the percussion is hollow; If the pulmonary capillaries rupture, it will cause hemoptysis, and there will be voiced sound during percussion, causing cough; Body temperature is generally normal or low fever, such as diffuse tuberculous pneumonia or systemic miliary tuberculosis; When the body temperature rises above 40℃, it shows relaxation heat or retention heat.
(2) Peritoneal tuberculosis
No obvious clinical symptoms.
(3) Breast tuberculosis
The clinical symptoms are not obvious. Breast nodules There are local or diffuse painless induration on the breast, and the surface is uneven. Some of them form tuberculous abscess, commonly known as cold abscess. Once the abscess is ruptured, the wound will not heal for a long time. Reduced milk production, milk as thin as water, can cause breast atrophy and stop lactation.
(4) Superficial lymph node nuclei
Lymph nodes under the ear, on the side of the neck and in front of the shoulder are swollen, such as fists or even bowls, and there is no pain. Rarely seen.
(5) Tuberculosis of reproductive organs
When the reproductive organs are invaded, the estrus of sick cattle is frequent or stopped, the pregnancy rate is low, and it is easy to abort after pregnancy. Pathological anatomy showed different combined nodules.
(6) Intestinal tuberculosis
It is more common in calves. In the early stage, it is characterized by loss of appetite, indigestion, alternating diarrhea and constipation, and in the later stage, it is characterized by intractable diarrhea, with mucus and pus mixed in feces, and the weight loss is rapid.
preventive measure
Because the disease harms people and animals, spreads widely and can be inoculated with sterile vaccine, the significance of purifying bovine tuberculosis is far greater than treating the disease. The quarantine of bovine tuberculosis must be carried out twice a year in spring and autumn, and the cattle found to be positive must be dealt with according to relevant laws and regulations. When replenishing cattle, strict quarantine should be carried out on the spot. When sick cattle are found, immediately isolate the whole herd. Slaughter open cows with obvious symptoms, destroy or bury internal organs, and the meat can be eaten after high temperature treatment or full cooking. If the number of cattle positive for tuberculin is small, it is suggested to eliminate them; If the number is large, you can concentrate on cultivating healthy calves in remote places. The method is that after the calf is born, the whole body is disinfected with 2% ~ 5% Lysol solution and immediately separated from the cow. Feed the colostrum of biological cattle (artificial milking) for the first 5 days, and then feed other healthy milk or sterilized milk. Calves aged 20 ~ 30 days, 100 ~ 120 days, and 180 days were quarantined for three consecutive times, all of which were negative for tuberculin and could be mixed with healthy calves. Positive calves will be eliminated immediately. The milk of positive cows can only be transported out after disinfection, and the feces can only be used after fermentation. Strengthen disinfection, fully disinfect 2 ~ 4 times a year, and disinfect feeding utensils once a month.
In addition, tuberculosis patients are not allowed to raise cattle and manage cattle. Employees should protect themselves.
Diagnosis and treatment
The diagnosis of the disease can be made according to clinical symptoms, staining microscopy, isolation and culture and animal inoculation. The most commonly used diagnostic method in cattle farm is tuberculin test.
The commonly used drugs to treat this disease are streptomycin, diammonium salicylate (PAS) and isoniazid. These drugs can be used alone or in combination. Isoniazid can also be used to prevent cattle from being threatened by infection. Lincomycin and amikacin also have good curative effects, and can be used in combination with the above drugs, but pregnant cows should be used with caution or forbidden.