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Diagnosis and Control of Calf Colibacillosis
Release time:
2020-09-14
With the continuous improvement of people's consumption level in recent years, the demand for dairy products in daily life has been increasing, which has also promoted the development of dairy farming industry and established many cattle breeding bases. The basis of the healthy and normal operation of these bases is the breeding of calves, and the diarrhea disease of E. coli is one of the important threat factors to the survival of calves before weaning.
With the continuous improvement of people's consumption level in recent years, the demand for dairy products in daily life has been increasing, which has also promoted the development of dairy farming industry and established many cattle breeding bases. The basis of the healthy and normal operation of these bases is the breeding of calves, and the diarrhea disease of E. coli is one of the important threat factors to the survival of calves before weaning.
Calf colibacillosis, also known as calf dysentery, is an acute infectious disease caused by a certain serotype of Escherichia coli. E. coli is widely distributed in nature, and animals can enter the gastrointestinal tract with milk or other food a short time after birth. Newborn calves can cause the disease when their resistance is reduced or digestive disorders occur. The causes of the disease are environmental factors, feeding and management factors. The main route of transmission is through the digestive tract infection, intrauterine infection and umbilical cord infection. The disease was diagnosed by clinical diagnosis, laboratory diagnosis and serotype identification.
The causes of Escherichia coli diarrhea are also various, and the common ones are acute and chronic infectious diseases caused by enterotoxigenic Escherichia coli. Once the disease occurs, there may be an epidemic trend, and if the sick cattle are not treated in time, they will die due to dehydration. Therefore, in this paper, the etiology, clinical symptoms, autopsy changes, diagnosis and prevention of Escherichia coli diarrhea in pre-weaning calves are briefly described as follows.
1 Causes
The factors causing E. coli diarrhea in calves are complex and diverse, mainly including environmental factors and feeding management.
1.1 environmental etiology
The totality of natural and social factors that exist around livestock that can directly or indirectly affect livestock. Such as the farm disinfection is not complete, the calf house is narrow, the density of cattle is too large, the cow house is dark and humid, the sunlight is insufficient, the cold protection condition is poor, the calf cold and so on can cause the calf colibacillus diarrhea disease.
1.2 feeding management
The reasons for feeding management are that when the breeders do not feed colostrum in time as required or the feeding amount is insufficient, the calves themselves are difficult to be protected by maternal antibodies, and then they are sensitive to many diseases, and diarrhea is caused by feeding spoiled and rancid milk. Or not according to the requirements of the umbilical cord disinfection of calves will also be in the house of E. coli. Secondly, the disease can also occur when newborn calves are mistakenly put into the enclosure already suffering from the disease. If the cow is weak during pregnancy, malnutrition, mineral and vitamin deficiencies and deficiencies can also cause the disease.
2 Clinical symptoms
The sick cow's body temperature is generally not high, and there is no obvious change in spirit and appetite at the beginning of the disease, and then it will discharge gray-white porridge-like feces. After a period of time, the diarrhea is watery, and the feces are mixed with foam and blood clots, and there is a sour smell. Calves show fever, lack of energy, due to dehydration, hair matte, the condition deteriorated sharply, after 2 to 3 days of failure and death. Another part of the sick calves initial temperature rise up to about 40 ℃, a few hours after the start of diarrhea, and the body temperature dropped to normal. The stool is like porridge, yellowish white at first, waty later, mixed with clotting, curd and foam, and has a rancidity odor. In the later stage, sick cows have lost appetite, are thin, their body temperature drops, they are lying on the ground, and die of failure. However, most calves die 1 to 3 days after the onset of the disease. The long course of the disease lasts for about 7 days, and symptoms such as pneumonia and arthritis appear. And growth retardation after cure. Individual calves had no obvious symptoms and died suddenly.
3 Change of necropsy
Dissecting the dead calf, it was found that there was a large amount of yellowish-gray liquid in the abomasum, containing curd, mucosal congestion and edema, catarrhal inflammation in the duodenum and small intestine covered with gelatinous mucus, mucosal congestion, thin intestinal wall, exfoliation of some mucosal epithelium, and scattered needle-like bleeding points in the folds. Rectal mucosa also has congestion or bleeding symptoms, intestinal contents are often mixed with blood and bubbles or even filled with watery substances, smell foul. The liver and kidney are pale and sometimes have bleeding spots, and there are bleeding spots of different sizes under the capsule, and the liver is fragile, and the gallbladder is filled with thick dark green bile. The macroscopic lesions were hemorrhagic inflammation of different degrees in mesentery, enlarged lymph nodes, dirty fluid in part of large intestine, small bleeding spots in endocardium, and other lesions were not obvious.
4 Diagnosis
4.1 clinical diagnosis
Cattle colibacillosis in 1~2 weeks of age within the most susceptible to disease, the abomasum, small intestine and rectal mucosa congestion, bleeding and other catarrhal inflammatory changes, liver and kidney sometimes bleeding, combined with the characteristics of defecation can make a preliminary clinical diagnosis.
4.2 laboratory diagnostics
Smear examination, take diarrhea feces and diseased cattle rectal cotton swab smear, gram staining microscopy, visible a large number of gram-negative bacilli.
Inoculate the diseased material on McConkey agar or eosin methylene blue agar, culture at 37 ℃ for 24 hours, select red colonies on McConkey agar, or colonies with dark blue and black in the center and metal flash on eosin methylene blue agar, and carry out pure culture.
Biochemical identification of the obtained pure culture inoculated with tri-sugar iron agar medium fermenting lactose or sucrose to make the slant and the bottom turn yellow, not fermenting lactose or sucrose, fermenting only glucose, the bottom turn yellow, the slant turn red and regular biochemical item identification.
Serotype identification. Application of anti O, K, H antigen standard serum for serological typing [1].
References:
[1] Lu Chengping. Veterinary Microbiology [M]. China Agriculture Press, 2007.8:100-107.
5 Prevention
Strengthen and improve the management of pregnant cows and calves, keep the cattle house dry and clean, well ventilated. When the cow is in labor, wash the dirt around the breast with warm soapy water, and then wash and dry with light salt water. Insist on spraying and disinfecting the cowshed, utensils and excrement with 5% lysule, eradicate the topsoil on the floor of the cowshed, and disinfect the floor with flame.
Immediately after birth, the calves were transferred to a new barn 200 meters away for isolation and artificial feeding. To prevent calves from being hit by damp and cold wind, drinking dirty water is forbidden. Let the normal calves after birth as soon as possible to make up colostrum, in order to enhance its resistance. An important precaution is to also inoculate a specific serotype of E. coli fire extinguishing vaccine.
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