The topic of our conversation today is brucellosis in cows. This is an acute infectious disease caused by a special kind of bacteria - Brucella. The disease spreads extremely rapidly, affecting almost the entire herd in a short period of time. As a rule, infection occurs through common watering and feeding places, as well as through airborne droplets. Brucellosis affects not only cows, but also goats, horses, and pigs. In addition, a person who is in constant contact with animals or eats meat and milk from sick livestock is also able to get sick.
Properties of harmful bacteria
Another name for brucellosis is the Maltese fever. The disease was discovered and described by the British military doctor Bruce in 1887. Among the bacteria Brucella, there are four species - melitensis, bovis, suis and canis, which are dangerous to human health. In shape, they are rod-shaped bacteria. Further in the text we will talk mainly about Brucella bovis - bull brucella.
They are especially dangerous for cows and very tenacious, able to live in the soil for 110 days, in manure - from about one to two months. Cooling and freezing does not kill Brucella, but rather allows it to persist pending subsequent defrosting. Heating, up to 100 degrees Celsius, can kill these bacteria instantly, up to 60 degrees in half an hour. They also die under the influence of direct sunlight and with disinfectant treatment.
Infection spread mechanism
As a rule, brucellosis in cattle occurs when a cow enters from 10 bacteria. Among the ways of infection can be identified various microtrauma, mucous membranes, and, above all, the oral cavity, respiratory tract. Especially dangerous are cows who have survived a miscarriage. Brucella in large quantities contained in the amniotic fluid and placenta. The stillborn calf is also infected. It is highly likely that it will spread through common feeders, watering places, litter and items of care.
Brucella is found in the meat and milk of a sick animal, so eating them without prior treatment can be dangerous for humans. Also, through the smallest cuts and abrasions on the skin, representatives of the professions who are in direct contact with cattle can become infected. For example, milkmaids, shepherds, veterinarians, workers in slaughterhouses, meat processing plants and dairy industries.
The bacterium does not survive in the open air, therefore aerogenic distribution is excluded. A person can become infected with human brucellosis by direct contact with micro-injured skin (handshakes) or mucous membranes (kisses).
On the timing of the preservation of brucellosis infection and how to eliminate it
Brucellosis bacteria resist well to the external environment. In unpasteurized dairy products, bacteria live for more than 50 days, in frozen meat, sick cows are stored for at least 5 months, in skins and fur - about 3 months.
The reservoir is able to clear brucella for six months, the soil - for a period of at least 2 years.
It is possible to get rid of Brucella infection by heating the contaminated medium or by treatment with disinfectants for 10 minutes. The latter method is only suitable for tools and animal habitats.
Can meat and milk from cows infected with brucellosis be used for food? The answer is unequivocal - it is possible, but with caution. For eating, the patient's meat should be boiled for 3-4 hours, and the milk should be boiled for 10-15 minutes.
Only all the symptoms at once
In cattle, brucellosis cannot be diagnosed with a focus only on the symptoms, since they are not sufficiently pronounced. One of the signs of the disease can be frequent miscarriages of the entire herd. However, this happens in each cow, mostly once. Very rarely - two times and almost never - three times or more. In addition, if the infection occurred before the cow was mated with a bull, an abortion does not occur.
Signs of herd infection with brucellosis:
- a wave of abortions or the birth of weak calves quickly dying after birth;
- delaying the afterbirth miscarriage, diseases of the uterus of cows, purulent discharge from the birth canal;
- loss of appetite, weight loss, fever;
- purulent mastitis in cows;
- inflammation of the testes in bulls;
- tumors of the fore and hind limbs, arthritis.
It is important to note that none of these symptoms separately makes it possible to diagnose the presence of brucellosis in cows with a 100% probability.
Brucellosis is very similar in symptoms to tuberculosis, so before prescribing treatment, it is necessary to pass special tests to clarify the diagnosis.
To confirm or refute Brucella infection, a serological examination of the blood of a sick animal is carried out. Also after abortion, samples of amniotic fluid, placenta, tissue fragments of dead fetus organs such as the stomach and liver are collected and examined.
In necropsy animals, during necropsy, lymph nodes, joints and testicles are biopsied.
The meat and milk of sick cows is checked for the presence of brucella before being sent to food production. When taking samples for analysis, you should be safe from the penetration of infection into the body of the researcher using protective gloves, masks and full body clothing.
About laboratory studies of the disease
A study on brucellosis of the blood serum of an animal is performed on physiological saline solution. There are positive, dubious and negative reactions that differ in dilution. At the same time, agglutination is observed - bonding and precipitation from a homogeneous suspension of bacteria.
For cows, a positive sample is considered to be when agglutinated in a physiological solution with a dilution of 1: 100, questionable - with a dilution of 1:50, negative - with an even weaker breeding. In the case of a questionable sample, a second check is carried out. If the dilution does not increase and if there are no other symptoms of brucellosis, the sample is taken as negative.
Now let's talk about the allergy reaction. Animals vaccinated with abortion and expect a response from 24 to 72 hours. A cause for concern is swelling of a size not less than a bean. In the event that it does not disappear three days after the introduction of abortine, it is reddened and sore, there is a fever in vaccinated cows, then the reaction is defined as positive.
If these symptoms appear separately or the swelling disappears within the first 2 days from the moment of the introduction of abortin, then this reaction is not considered positive. A positive reaction makes it possible to unambiguously judge whether a cow is infected, but the recovered animals also give the same results, therefore additional research is required.
Methods of treating livestock
In the acute form of brucellosis in cows, the use of antibiotics is effective. In chronic form, antibiotics do not help. Then use the vaccine against brucellosis to relieve symptoms. In Switzerland, Kausit is used according to the instructions, but in other countries it is not certified. In the USA, most often for economic reasons, sick cows are sent for slaughter. It comes out cheaper than the cost of isolation, treatment and testing.
In the USSR, cases of mass spontaneous recovery of cows were repeatedly observed, which was confirmed by numerous checks. In isolated farms, up to 80% of cattle infected with brucellosis recovered.
To give the animal a chance for recovery or not is up to the owner to decide.
In order to prevent the spread of infection, sick cows are either slaughtered or isolated, and in separate quarantine farms. Experience has shown that incomplete isolation, when healthy and sick animals are kept in different parts of the barn or just in the same area, does not produce results.
About disease prevention
To prevent the breeding of Brucella bacteria, it is important to timely clean the manure and disinfect the places of keeping of cows with calves. Separate premises for childbirth and animals suspected of having brucellosis should be organized.
It is recommended to conduct a regular vaccination of the herd. Immunization carried out in this way greatly reduces the risk of disease.
Calves should be raised separately from adults to prevent infection. They should eat from special feeders, drink from special reservoirs to which no infected animals have access. A special litter should also be used for calves. They need to be vaccinated with a brucellosis culture to avoid future infection.
For the prevention of brucellosis in humans, it is recommended to use protective clothing, gloves and high rubber boots. In order to safely drink milk, it must be boiled, it is also better to eat cow’s meat after a long heat treatment.
Danger to humans
The incubation period of the disease ranges from 2 to 3 weeks. Brucellosis at first almost does not appear. But the invisible symptoms eventually become unbearable. Feelings grow gradually from mild ailment to extremely severe pain and aches throughout the body. The body temperature of the patient reaches 41 degrees Celsius. There is a sharp weight loss, an obsessive desire to drink.
In addition to the physical symptoms, the patient feels psychological. In the end, against the background of constant terrible pain, there is a loss of connection with reality and schizophrenia.
The disease rarely lasts longer than 4 months. Fatal outcome is unlikely, but a third of those who have been ill have severe injuries to the body and psyche, leading to disability.
Also found is the chronic form of brucellosis, in which the acute phase alternates with remission. Fatal outcome remains unlikely.
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