Clostridium welchii in dairy cows is mainly caused by pollution of the environment, drinking water, feed and so on. When dairy cows are fed, bacteria or spores will enter the intestinal tract and multiply in large quantities, resulting in the occurrence of Clostridium welchii. Besides, sudden changes in climate and feeding environment, or sudden changes in feed, will weaken the body's resistance, at this time intestinal flora disorder, leading to the intestinal tract itself, Clostridium welchii began to multiply in large numbers, but also prone to disease.
Cattle of any breed and age (including dairy cattle, yellow cattle, buffalo, etc.) can be infected with the disease and can occur in any season throughout the year. Dairy cows and calves are more likely to develop the disease in April-May and October-November, farming cattle are more likely to develop the disease in April-June, yaks are more likely to develop the disease in July-August. The duration of the course varies from a few minutes to several hours in a short time to 3-4 days or longer in a long time. When the disease occurs, it can concentrate in the same circle or near the cowshed, and it can also occur in a jump mode. The disease has different onset intervals, sometimes several days or more, sometimes several months apart. Besides, the mortality rate of the disease is also different, such as 70% - 100% in dairy cows and 93% - 100% in cattle. Dairy cows are usually high-yielding and susceptible to disease. Calves and cattle are usually fat and strong.
Diseased cattle often suffer from the acute disease without any precursor symptoms, and the duration of the disease is short. It is difficult to detect and treat the disease early. The diseased cattle mainly showed rapid lying up, abdominal pain, loss of appetite or abandonment, obvious weakening of rumination, or even complete cessation, stomach, stomach, and rumen had accumulated food, rumen was expanded. Limbs weakness, walking shaking or lying on the ground, muscle tremor, frequent urination, but less urine. The end of the ear and nose are cold with foam or saliva coming out of the mouth. Bilateral jugular veins are markedly enlarged and the heartbeat is accelerated, usually more than 100 beats per minute. Heart rate is irregular. Heart sounds are weak or hyperactive. Some of them are accompanied by intracardiac murmurs. Difficulty in breathing, exhaling odorous gases, there is a distinct wet beep in the lungs. The body temperature increases at the beginning and decreases at the later stage. Muscle tremors, convulsions, shaking, and eventually fall to the ground and die. 30-60 minutes after death, abdominal swelling, tongue protruding from the mouth and anal valgus were found.
The dead cattle were in good appearance and nutritional condition, with enlarged liver, slightly brittle texture and sometimes focal necrosis. The spleen is enlarged, brittle and fragile. Hemorrhagic inflammation with emphysema occurs in the lungs to varying degrees. The kidneys were swollen and congested, and a few of them had bleeding spots. There are a lot of bleeding spots and spots in the auricle, endocardium, and epicardium, and the thymus has hemorrhagic lesions. The true gastric mucosa was exfoliated, the lower layer was hemorrhagic inflammation, and the other three stomachs had different degrees of inflammation. Hemorrhagic inflammation occurs in the intestine. There are a lot of blood stasis infiltration areas in the mesentery and omentum, and sometimes there are bubbles on the mesentery. Systemic lymph node enlargement occurs in varying degrees, with some accompanied by hemorrhage.
Morphological observation. The intestinal contents, mucosal scrapes and liver and spleen tissues of diseased cattle were taken for smears under sterile conditions and examined by Gram staining and microscopy. The results showed that a Gram-positive strain of E. coli existed in capsules, arranged in single or double rows. Parts form spores, often at one end of the fungus.
Separation culture. The contents of diseased cattle intestines were taken under sterile conditions and bathed in warm water at 80 ~C for 15 minutes, then centrifuged at a speed of 2000 r/min for 15 minutes. The supernatant was inoculated into the anaerobic broth for meat liver and agar plate for 20-24 hours at 37 ~C. Then the supernatant was cultured on agar plate of sheep fresh blood and agar plate of the common agar plate. Linear inoculation was carried out, and isolation and culture were carried out in a 37 C temperature box. At the same time, organs were inoculated in meat liver soup, cultured under anaerobic conditions, then cultured on agar plate of sheep blood, and then single colonies were selected for pure culture and staining microscopy. The results showed that no bacteria grew on the agar plate, and the anaerobic broth would become a uniform suspension after 18 hours, and paraffin with a length of 2 cm was attached to the wall of the test tube near the liquid side above the liquid surface. Large gray-white disc-shaped colonies grew on the agar plate. The surface was wet and smooth, some of them had radial stripes, and hemolytic rings appeared on the blood agar plate. When the bacteria were cultured in pure culture, Gram-positive Escherichia coli was found, and spores were formed in a few cases.
Emergency treatment. The diseased cattle could be subcutaneously injected with 20 mL sodium caffeine injection and slowly intravenously dripped with a mixture of 1 000 mL 10% glucose injection, 2 000 mL glucose saline, 500 mg hydrocortisone, 15 16 million penicillin potassium, and 10 ml sodium caffeine injection. Diseased cattle can also be intramuscularly injected with 20 2 ml amikacin sulfate injection, 20 80,000 gentamicin sulfate injection and 10 2 ml hemostasis.
Immunization in time. In the season of the high incidence of the disease and the areas where it is easy to occur, Clostridium welchii inactivated vaccine should be used to immunize susceptible animals in time to promote the formation of specific immunity of the body, to resist Clostridium welchii infection. It is better to use the vaccine prepared with the same serotype as the local epidemic strain or the local isolate strain, which has a better immune effect. Besides, because the exotoxin produced by Clostridium welchii is the main cause of the disease, but different serotypes secrete different exotoxins, it is better to use the multivalent vaccine for preventive injection.