In comparison with the relatively recent past, salmonellosis of calves in our country is now much less common. However, it is still too early to relax. The economic damage from this disease is still in serious numbers. Small businesses and households are especially hard hit where young animals are less often vaccinated or not vaccinated at all. Next, we will step by step analyze what the etiology of the disease is, what causes it, and most importantly, how to deal with various forms of the disease.
It is believed that in 1885, the scientist Salmon and his colleague Smith, working on pig diseases, identified the first representative of this group, later called the Salmonella suipestifer. Considering this merit, in 1934 the international community of microbiologists suggested naming all pathogens of this group as Salmonella.
The entire group of Salmonella microorganisms is part of a fairly large bacterial family called Enterobacteriaceae. Specifically, salmonellosis calves most often causes Salmonella dublin. In about 20-30% of cases, the cause of the disease can be a form of Salmonella typhimurium. Diagnosis of other species in calves occurs, but extremely rare.
All members of the group are alike. Visually, these are rods with rounded edges 1–4 µm long and 0.5 µm thick. Microorganisms are gram-negative, can be stained with aniline dyes. Bacteria do not encapsulate and do not create spores. It is best to multiply in a normal nutrient medium from 7.2 to 7.6 pH at 37 degrees above zero.
The disease in calves is most often recorded in the spring during the period of mass calving. The reason is a significant drop in the overall body resistance in cattle. The risk group includes calves aged 10 days to 2 months.
The first are ill, poorly developed calves and animals born with pathology. If time does not take action, then all the livestock of young animals, regardless of their physical condition, can get sick and die within 2-3 weeks.
In calves, infection occurs alimentary, that is, during the feeding of young calories with milk, or skimming, from animals that are carriers. Sick calves acquire immunity, but they continue to spread the disease with feces, saliva and other secretions.
Interestingly, adult cows can be carriers of the disease throughout life without any harm to themselves.
Pathogenesis in young
With salmonellosis, the calf usually suffers from the bowels first. After all, after passing through the mouth, the infection gets there and immediately begins to actively multiply. It is at this stage that the initial symptoms and the characteristic signs of the disease appear.
Bacteria as such are not dangerous. But as a result of their vital activity and with active reproduction, microorganisms secrete endotoxins, which are a terrible poison for the body of the calf.
If you do not start treating the disease in time, then when the critical mass is reached, the endotoxins break through the protective layer of the intestine and enter the blood and lymphatic systems of the animal.
This stage is already called paratyphoid septicemia, and it is the most dangerous in case of salmonellosis in calves. In the circulatory system, exudative changes lead to red blood cell diapedesis, which, in turn, causes abundant hemorrhages and leads to the defeat of the mucous membranes, as well as serous integuments.
General symptoms of the disease
The course of the disease can be acute or severe, subacute and chronic. But in all three types of diagnosis almost the same symptoms determine. On average, incubation (the period from infection to the appearance of the first signs of illness) ranges from 1 to 3 days. For physically strong calves, incubation can be delayed up to 7 days.
It all starts with an increase in temperature, depending on the form of the disease, it ranges from 39 ° C to 41 ° C. There is general apathy, the baby loses interest in what is happening around and constantly lies, throwing his head back or lowering it on his chest. When you try to put him on his feet rises reluctantly, but almost immediately falls back.
Approximately in 3-4 days at a calf the intestines are upset, the liquid chair or a frank diarrhea is observed. Appetite is not stable, in some cases, the animal completely refuses to eat.
Acute or severe form
In this form, the temperature rises sharply to a maximum. Against the background of heat, cardiovascular activity is disturbed, - manifested in an increase in pulse rate up to 150 beats with a pronounced arrhythmia. Auscultation of heart pushes spilled.
The kid sharply and often begins to breathe, an average of 60-80 breaths per minute. Also, with increasing temperature, symptoms of serous conjunctivitis appear, that is, tears constantly flow, and purulent rhinitis develops.
No later than 3 days of illness, intestines upset. Vidkom feces are observed grayish mucous clots with bubbles, and later bloody inclusions appear. All secretions are not characteristic and very sharp smell.
In this form, an intestinal disorder is followed by kidney damage. Urination becomes frequent and, as a rule, painful. In the urine protein appears, red blood cells and other not characteristic blotches. Approximately 5-10 days of illness, due to sharp losses in weight, the calf dies.
The symptoms of the subacute form are almost the same. They are expressed somewhat weaker, but this disease does not become less dangerous. The temperature of the calf is kept between 40-41 degrees.
Apathy is, but such calves do not refuse food. Conjunctivitis is not so acute, and serous-mucous discharge from the nose may not have any purulent patches at all. The stool is fluid, but diarrhea is periodic, without bloody threads or clots. Obvious kidney damage is not visible, although the urine may be turbid, indicating an inflammatory process in this area.
The calf appears primary signs of pulmonary infection. On palpation in the area of the larynx in an animal, attacks of a sharp and strong cough begin. During auscultation, wheezing and vesicular heavy breathing are clearly heard in the lungs. The anterior lobes of the lungs may become dull.
For calves, chronic salmonellosis is often an undertreated acute or subacute form of the disease. Here, the manifestations are more like pneumonia than an internal disorder caused by the Salmonella bacillus.
Diarrhea either subsides or stops altogether. In this case, the calf's appetite is normalized completely. The cough is dry and rare at first, but gradually it develops into a hysterical, moist and often painful for a baby.
In the lungs, fine-bubble and large heart rales are heard. Rhinitis becomes acute. From the calf's nose constantly flows, and the discharge is purulent. As the disease progresses in the animal, the carpal, knee and hock joints become inflamed, they feel hot and painful to the touch.
The chronic form of the disease can last up to 2-3 months, but in any case, if the animal is not treated, it dies.
If the baby "caught" the infection at an older age, then everything can be done with a little diarrhea and a slight cough, after which he recovers. But this happens only with strong calves.
The pathoanatomical signs of salmonellosis in cattle in general and in calves in particular are characterized by intestinal as well as general septic abnormalities. The spleen with rounded edges and greatly enlarged, has a grayish-red, sometimes almost black color.
The vessels under the spleen are filled with blood, and there may be numerous ruptures and hemorrhages. The mucous membrane of the stomach is reddened and swollen. Especially strongly inflammations are traced on all sorts of folds. Hemorrhages can be noticed.
The small intestine is strongly affected, point or streak hemorrhages are clearly visible on the mucous membrane. In the severe form, the large intestine is affected approximately as well.
If the disease has progressed rapidly in an acute form, then the liver may not be affected. But the calf clearly shows severe damage to the lungs, manifested in the form of congestive hyperemia and edema, characteristic of catarrhal bronchopneumonia.
Antibiotics in the treatment of salmonellosis
Upon detection of the first signs of disease, the animal is immediately isolated from the herd and transferred to a moderate diet. Antibiotics are considered the main weapon against all forms of the disease. But before the appointment it is necessary to check the reaction of the calf to certain drugs.
Levomitsetin appointed at the rate of 0.04 g per 1 kg of calf weight. The drug is mixed into the water and given to the animal 3 times a day. The course of such therapy lasts 2-3 days.
The dose of synthomycin ranges from 0.02 to 0.04 g per 1 kg of calf weight. The drug is given 3 times a day, but the drug is mixed into the milk, and the course can take up to 5 days, depending on the form of the disease.
Tetramycin, or chlortetracycline, at a dosage of 0.02 g per 1 kg of weight is given 3 times a day. The course can last up to 6 days.
With obvious signs of pneumonia and the chronic form of the disease, neomycin can be administered at a dosage of 10 thousand units. per 1 kg of calf weight.
In the fight against such a dangerous disease of young cattle, alternative and, as a result, less aggressive drugs that have fewer contraindications are widely used.
Thus, antitoxic polyvalent serum against calf salmonellosis has been used for quite some time. This drug is able to treat both mild forms of the disease and prevention.
The drug is administered intramuscularly calf. In the prevention of disease, the dose ranges from 5 to 10 cubic meters. cm per day. In the treatment of salmonellosis, it rises to 20 cubic meters. see. The injection is done in the middle third of the baby's neck.
It is important that the daily volume of the drug was distributed to 3 injections, which are made to the calf at intervals of about 4 hours. In the open state, the serum is not stored. The opened bottle needs to be used within a day. If this is not possible, the drug is considered defective and destroyed.
How the flock is vaccinated
Concentrated salmonellosis vaccines are considered to be perhaps the most effective means to prevent all forms of the disease. For example, a formolkvastsovy vaccine in its effectiveness and reliability is almost 2 times higher than the above-mentioned means.
Ideally, serum formulkvastsovy against salmonellosis should be injected deep under the skin of pregnant cows 50-60 days before calving. Animals should be vaccinated in 2 runs. The interval between injections is 8-10 days. The volume of the first injection is 10 cc, for the second injection 15 cc is taken.
If the herd of salmonellosis is safe, then vaccination of cows for prevention is quite enough. In a dysfunctional economy, it is necessary to vaccinate newborn calves. It also needs a double subcutaneous injection. The first injection is done no later than 2 days after birth, and the second after 3-5 days. The interval depends on the general physical condition of the baby and is determined by the veterinarian.
Disease prevention measures
Salmonellosis in cattle is a real win. The main preventive measures are deservedly considered good, regular, and most importantly, good nutrition of the whole herd and cleanness on farms. There have been cases when even vaccinated animals with poor nutrition developed the disease.
The main source of infection are sick animals and carriers of the disease. If it is impossible to isolate the carriers from the herd, then it is necessary to remove pregnant cows and young animals in a separate room. The following solutions are used for disinfection of farms:
- bleach in which contains 25% of active chlorine;
- Slaked lime in a concentration of 20% (walls are whitened with it);
- caustic soda - concentration in solution 4%;
- formalin - concentration in solution 2%.
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