Taking the viral diarrhea disease of beef cattle in 2020 as an example, this paper analyzes and discusses the disease from the aspects of the incidence of the disease, the epidemic status, the main diagnostic methods, and the feasible prevention and control measures, in order to improve the technical level and effectiveness of the comprehensive prevention and treatment of viral diarrhea disease in beef cattle in the grass-roots cattle industry in our province.
First, the incidence of the disease
At the beginning of April 2020, a rural beef cattle farm in Tongyu County responded to the local veterinary department with an epidemic of stubborn diarrhea in beef cattle, the duration of the disease of cattle was between 3 days and 5 days, and the abnormal symptoms initially found were reduced appetite, mental and malaise, individual cattle wasted hunger strike, the cattle commonly had jet-like watery diarrhea, some of the cow's water-like feces contained mucosal tissue fragments and blood, observed the body of the cattle, there was a rapid emaciation change, some of the cattle with cattle appeared ulcerated on the nose mirror, stopping rumination behavior, Maintain body temperature around 40 °C. After the discovery of the disease, the technical staff of the cattle farm took antibiotic pre-treatment measures for the cattle, the effect was not obvious, the cattle farm continued to increase the number of cattle, reported to the veterinary station after the discovery of the disease 4 days later, after the professional and technical personnel of the veterinary station on-site observation, the epidemic was initially diagnosed as a beef cattle viral diarrhea disease, the scene of the cow feces collection, after the laboratory carried out RT-PCR testing, and finally confirmed the epidemic as bovine viral diarrhea, took corresponding treatment measures, and quickly controlled the disease. Avoid more losses on the farm.
Second, the current situation of the epidemic
Bovine viral diarrhea disease of the source of infection is not a single, suffering from cow nose secretions, eye secretions, milk, blood, urine, feces have a certain content of virus, can become the medium of infectious diseases, in addition to the virus of beef cattle are also infectious, may pollute the entire cattle farm feed, drinking water, environment, healthy cattle in the virus spread pollution, can be through the feeding, drinking water, breathing infected with viral diarrhea diseases, research cases can be found that the main transmission route for the digestive tract and respiratory tract, Note that the disease can be transmitted vertically to calves by infection by cows. Beef cattle of all ages and breeds are likely to be infected with viral diarrhea diseases, the susceptible group is calves between the ages of 6 months and 18 months, if the cattle farm has not established a standardized feeding management model, the calf colostrum intake after the cow is not timely, the cattle growing environment is cold, the pen is humid, the number and density of each pen feeding are too large, the level of cleanliness and hygiene is poor, and the disinfection measures are incomplete, which may become the cause of disease. In general, acute onset is common in new epidemic areas, basically about 5% of the incidence, but with 90% to 100% of the very high case fatality rate, the old epidemic area of viral diarrhea disease mortality, morbidity is not high, and acute incidence is very rare, but there are more than 50% of the hidden infection rate needs to be noted, outbreaks mostly appear in fully enclosed cattle farms.
Third, the diagnostic method
The diagnosis of viral diarrhea disease in beef cattle is basically divided into three steps, first observing clinical symptoms, second combining pathological changes, and finally combining laboratory test results.
3.1. Clinical symptoms
Chronic clinical symptoms are mainly manifested as: fever is not obvious, only a few patient cattle body temperature exceeds the level standard, more secretions flow out of the eyes of the affected cattle in a serous state, the nasal mirror has a continuous erosion phenomenon, the incisors are more common redness changes, skin erosion and necrosis problems often occur between the toes, more accompanied by symptoms of hoofitis, the skin is more serious, dander-like skin, of which the obvious parts are the elder, neck, and behind the ears, most of the cattle disease develops between 2 months and 6 months of disease and death, and some suffer from cattle disease for more than 1 year. Because of the prolonged course of the disease, the affected cattle continue to excrete the virus to the external environment, so it is the main source of chronic beef cattle viral diarrhea disease.
Acute clinical symptoms are mainly manifested as: the incubation period of cattle infected with the virus is 7 days to 10 days, the onset is very sudden, the body temperature rises rapidly, basically between 40 ° C and 42 ° C, the appetite is rapidly reduced, the spirit is too weak, individual cattle have a stun condition, after the development of the disease for about 3 days, the oral necrosis area of the cattle is increased, the diarrhea is severe and may die due to acute dehydration, the course of the disease begins to appear in about 7 days, and the cattle with poor physique may die after 2 days.
3.2. Pathological changes
Dissecting sick and dead cattle can find the following major pathological changes: lesions in the digestive tract and lymphoid tissue, ulceration and erosion problems in the gums, palate, nasoscope, and mucous membrane of the nostrils, erosion problems in the mucosa of the esophagus with different sizes, erosion phenomena have straight line characteristics, and necrotizing, ulcerative, and hemorrhagic verification problems in the jejunum, cecum, colon, and small intestine. When the cow is a newborn calf, there is water accumulation in the ventricles on both sides, the cerebellar development is seriously incomplete, and when the cow is a pregnant cow, the probability of miscarriage increases, and ulcers and blood spots appear in the true stomach, esophagus, trachea, and oral cavity after the fetus is excreted.
3.3. Laboratory testing
Laboratory staff will be sick and dead cattle under sterile conditions for intestinal contents extraction operations, and then the appropriate addition of normal saline, and then began to grind on ice, after a certain period of time, the supernatant was negatively stained operation, began electron microscopic detection, can observe the presence of viral particles in a round shape in large quantities, about 60nm diameter, particle surface has 10nm to 20nm circular subunits and capsules.
4. Prevention and control measures
First of all, farms should complete the beef cattle immunization procedure on time, and the appropriate vaccination time can be carried out before and after the weaning of the calves, which can reduce the chance of the calves being infected with viral diarrheal diseases. Before the breeding measures are carried out, the cow and bull need to implement another immunization procedure to achieve the effect of collective enhancement of the immunity of the cow, bull and calf.
Secondly, timely isolation and replacement of cattle, the farm found suspected cattle immediately isolated, close observation, increase the frequency of daily body temperature monitoring, make a record of the cow feces, to ensure that healthy cattle, suspicious cattle, preliminarily confirmed cattle can be raised and managed alone, so as to facilitate the control of the spread and development of the disease.
Third, to strengthen the disinfection measures, cattle farms can use 100 poison solution (1:500 times dilution) to strengthen the disinfection and spraying operation, the frequency starts at 1 time / day, and after seven consecutive days, it can be carried out according to the frequency of one time / week.
Finally, symptomatic treatment, although there is no specific drug to treat beef cattle viral diarrhea disease at this stage, but timely inactivated tissue fluid therapy, serum therapy can have good therapeutic effect. In addition, intravenous injection of ceftiofurode sodium, vitamins, calcium gluconate, coenzyme A, ATP, glucose saline, etc., can alleviate the severe disease of cattle and accelerate the recovery speed of cattle.
Author: Yang Zhitao Veterinarian Tang Jianguo2