Content
- What is bovine tuberculosis
- How is bovine tuberculosis transmitted
- Causes of bovine tuberculosis
- Stages of bovine tuberculosis
- Primary stage of bovine tuberculosis
- Post-primary stage
- bovine tuberculosis symptoms
- Diagnosis of bovine tuberculosis
- bovine tuberculosis treatment
Bovine tuberculosis is a chronic and slow disease that can affect cows and is very important in public health, as it is a zoonosis, that is, it has transmission capacity to human beings. Symptoms are mostly respiratory and characteristic of a pneumonic process, although digestive signs may also be observed. The responsible bacteria belong to the complex of Mycobacterium tuberculosis and can affect numerous animals, especially ruminants, herbivores and some carnivores.
Continue reading this PeritoAnimal article to know everything about bovine tuberculosis - causes and symptoms, what it consists of, how it is transmitted and much more.
What is bovine tuberculosis
Bovine tuberculosis is a chronic infectious contagious bacterial disease whose symptoms take a few months to appear. Its name comes from the nodular lesions it causes in affected cows, called "tubers", in the lungs and lymph nodes. In addition to cows, goats, deer, camels or wild boar, among others, can also be affected.
How is bovine tuberculosis transmitted
The disease is a zoonosis, which means that bovine tuberculosis can be transmitted to humans through aerosols or by ingesting contaminated or unsanitary dairy products. Is disease of mandatory notification to the official veterinary service, according to regulations of the Ministry of Agriculture, Livestock and Supply, and also to the World Organization for Animal Health (OIE), in addition to one of the most common diseases in cattle.
Causes of bovine tuberculosis
Bovine tuberculosis is caused by a bacterial bacillus from the complex of Mycobacterium tuberculosis, especially for Mycobacterium bovis, but also Mycobacterium caprae orMycobacterium tuberculosis much less often. They have very similar epidemiological, pathological and ecological characteristics.
Wild animals such as wild boar can serve as bacteria amplifiers and as a source of infection for the domestic vacuum.
The contagion occurs mainly through the inhalation of respiratory aerosols, by the secretions (urine, semen, blood, saliva or milk) or ingestion of fomites that carry it.
Stages of bovine tuberculosis
After infection, there is a primary stage and a post-primary stage.
Primary stage of bovine tuberculosis
This phase occurs from the infection up to 1 or 2 weeks when specific immunity starts. At this point, when bacteria reach the lungs or lymph nodes, cytokines start with dendritic cells that attract macrophages to try to kill the bacteria. The killing cytotoxic T lymphocytes then appear and kill the macrophage with the mycobacteria, resulting in debris and necrosis. The immune system directs more lymphocytes around the necrosis that become spindle-shaped, sticking together, forming tuberculous granuloma.
This primary complex can evolve to:
- Cure: usually not the most frequent.
- Stabilization: more frequent in humans, with calcification of the lesion to prevent the mycobacterium from escaping.
- Early generalization by blood: when there is no immunity. This can be rapid, with miliary tuberculosis occurring, with the formation of numerous tuberculous granulomas on all sides, small and homogeneous. If it occurs slowly, heterogeneous lesions appear because not all mycobacteria appear at the same time.
Post-primary stage
occurs when there specific immunity, after reinfection, stabilization or early generalization, where the bacterium that causes bovine tuberculosis spreads to adjacent tissues through the lymphatic route and through the rupture of the nodules.
bovine tuberculosis symptoms
Bovine tuberculosis may have a course subacute or chronic, and it takes at least a few months for the first symptoms to appear. In other cases, it can remain dormant for a long time, and in others, the symptoms can lead to the cow's death.
You most frequent symptoms of bovine tuberculosis are:
- Anorexia.
- Weight loss.
- Drop in milk production.
- Floating fever.
- Painful, intermittent dry cough.
- Lung sounds.
- Breathing difficulty.
- Pain in the ribs.
- Diarrhea.
- Weakness.
- Increased size of lymph nodes.
- Tachypnoea.
- caseous necrosis tuberculous lesions, with a pasty and yellowish consistency.
Diagnosis of bovine tuberculosis
The presumptive diagnosis of bovine tuberculosis is based on cow symptomatology. However, the symptomatology is very general and indicative of several processes that can affect cows, such as:
- Upper respiratory tract diseases.
- Lung abscesses due to aspiration pneumonia.
- Contagious bovine pleuropneumonia.
- Bovine leukosis.
- Actinobacillosis.
- Mastitis.
Therefore, symptomatology can never be a definitive diagnosis. The latter is obtained with laboratory tests. O microbiological diagnosis can be obtained by:
- Ziehl-Nelsen Stain: looking for mycobacteria in a sample with Ziehl-Nelsen staining under the microscope. This is very specific, but not sensitive, which indicates that if mycobacteria appear, we can say that the cow has tuberculosis, but if they are not seen, we cannot rule out.
- bacterial culture: it's not routine, just like checking as it's very slow. Identification is performed with PCR or DNA probes.
In turn, the laboratory diagnosis includes:
- Elisa indirect.
- Elisa post-uberculinization.
- Tuberculinization.
- Interferon-gamma release test (INF-y).
O tuberculinization test is the test indicated to detect it directly in the cow. This test consists of the injection of bovine tuberculin, a protein extract of Mycobacterium bovis, through the skin of the neck frame, and measurement 3 days after the injection site to change the thickness of the fold. It is based on comparing the thickness of the forceps in the area, before and after 72 hours of application. It is a test that detects type IV hypersensitivity in an animal infected with mycobacteria of the bovine tuberculosis complex.
The test is positive if the thickness is greater than 4 mm and if the cow has clinical signs, while it is doubtful if it measures between 2 and 4 mm without clinical signs, and is negative if it is less than 2 mm and has no symptoms.
Thus, the official diagnosis of bovine tuberculosis consists of:
- Culture and identification of mycobacteria.
- Tuberculinization.
bovine tuberculosis treatment
Treatment is not advisable. It is a notifiable disease. Unfortunately, every positive animal must be euthanized.
There is only treatment for human tuberculosis, and also a vaccine. The best prevention to avoid getting bovine tuberculosis is milk pasteurization of these animals before being ingested, as well as good management and control of cattle.
In addition to controlling the farms, a tuberculosis detection program with official diagnostic tests and inspection of visceral injuries at the slaughterhouse to prevent their meat from entering the food chain.
This article is for information purposes only, at PeritoAnimal.com.br we are not able to prescribe veterinary treatments or perform any type of diagnosis. We suggest that you take your pet to the veterinarian in case it has any type of condition or discomfort.
If you want to read more articles similar to Bovine Tuberculosis - Causes and Symptoms, we recommend that you enter our Bacterial Diseases section.