Infectious diseases of cows can cause significant harm to livestock production, as they worsen the health of animals and can lead to death. Let's consider the causes and signs of bovine paratuberculosis, methods for diagnosing the disease and preventive measures that need to be taken to reduce the likelihood of the infection spreading on your farm.
What is paratuberculosis
Bovine paratuberculosis is a chronic infectious disease of ruminants.The causative agent is the bacteria Mycobacterium paratuberculosis, obligate parasites that are resistant to the negative effects of external factors and disinfectants. The disease occurs predominantly in a latent form, that is, without pronounced symptoms; in the clinical course, the disease can result in the death of the animal in 2-4 months.
Sources and routes of infection
Bacteria enter the body of cows with food, which becomes infected with fecal matter and secretions of sick animals, since in cows with paratuberculosis the intestines are affected. Mycobacteria can end up on animal care equipment and can contaminate pastures, water sources, fodder and premises. Calves become infected through milk from sick mothers, and can also be born already infected.
Isolation of parasites from the body of sick animals begins 3-5 months after infection. Paratuberculosis is dangerous because many animals are asymptomatic, which is why they do not differ in appearance from healthy ones, but are carriers of bacteria.
Outbreaks of paratuberculosis can occur at any time of the year. A large number of diseases are recorded in regions where there are acidic, wet or saline soils, which is explained by the fact that plants grown on such soils are poor in calcium and phosphorus salts.
The likelihood of developing paratuberculosis increases when cows are fed acidic feed, such as silage, with helminthic infestations, or after hypothermia or overheating of animals. Cows can become ill during the acclimatization period or when kept in unusual conditions.
Symptoms of the disease
The incubation period of paratuberculosis can last from several months to 1 year.Latently ill cows are stunted, lose weight, and their fatness is not restored. Those animals that have good body resistance and that eat normally and receive good care can recover on their own. A latent disease becomes clinical for various reasons that reduce the resistance of the cow’s body.
Clinical signs of paratuberculosis appear mainly in young animals 3-5 years old, which have already had 1 or 2 calvings.
Paratuberculosis can be identified by its first signs, such as a decrease in milk yield, the appearance of swelling under the jaw and in the chest area, and progressive exhaustion. From time to time, animals experience diarrhea, which becomes persistent over time. Feces have a liquid consistency, have an unpleasant odor, lumps of mucus can be seen in them, and rarely blood and gas bubbles. Animals eat normally and do not lose their appetite, but due to dehydration, they begin to drink more water. There is no increase in temperature or pain.
The cow loses weight and muscle mass decreases, especially on the croup and hind legs. This reduces the economic value of the animal.
Diagnosis of the disease
The diagnosis - paratuberculosis - is made according to epizootic and clinical signs, according to the results of allergy tests and laboratory bacterioscopic studies for the presence of the pathogen. Additionally, another test is used - the complement fixation reaction.
Pathological changes in paratuberculosis affect the small intestine and its posterior part.Characteristic symptoms are 5-10-fold thickening of the mucous membrane in the affected areas. There is a narrowing of the intestinal lumen, clearly visible on the cross section. The longitudinal one shows obvious longitudinal and transverse folding; when stretched, the folds do not disappear. The lymph nodes on the mesentery and ileocecal valve are enlarged, elastic, moist when cut, and gray-yellow in color.
Some sick animals may experience swelling of the serous membrane of the mesentery and intestines, enlargement of the lymph nodes, partial enlargement and partial atrophy of the intestinal villi.
Treatment of paratuberculosis in cattle
No specific treatment for paratuberculosis has been found; therapy for the disease is considered ineffective, since recovery does not occur. Sick animals are slaughtered, damaged organs are disposed of, and the meat can be eaten. According to the instructions, animals that have a positive reaction to tuberculin are separated from the general herd and raised separately. The young animals obtained from them can be raised for meat, but they are not suitable for breeding.
Prevention
In areas unaffected by paratuberculosis, cows are periodically examined. Animals with visible symptoms are sent for slaughter. All others who are already 1.5 years old are diagnosed using RSC. Those with positive tests are also sent for slaughter; those with negative results are left in the herd. These cows are then examined using the same method twice a year.
Calves up to 1.5 years old are raised separately from the rest of the herd. They are fed milk from healthy animals or milk from those that have positive tests, but there are no clinical signs of paratuberculosis. This milk is pre-pasteurized.
It is necessary to purchase new animals to complete the herd only from farms that are free from this disease, because it is not always clear that a cow or calf is sick. Animals must be fed and cared for in accordance with zoohygienic requirements. After manure is collected, it must be dried and burned or biothermally disinfected in compost heaps.
Disinfect the premises where cows are kept, equipment and milking equipment. Slaked lime, sodium hydroxide, a solution of formaldehyde, creolin, and phenol can be used as disinfectants. Barns are disinfected after inspection of the livestock and after calving. A farm is considered free from paratuberculosis if sanitary treatment has been carried out on it, and no sick animals have been identified within 3 years after the last case of the disease.
Cattle paratuberculosis cannot be treated; sick animals either die or are slaughtered. To prevent the spread of the disease within the farm, it is necessary to conduct livestock inspections, do tests, and make sure that cows can be raised separately from the general herd, if necessary.
