Tuberculosis is a bacterial zoonosis that affects both human beings and animals. It is a disease that is feared by many people because of its high mortality rate if untreated. It is assumed that one third of the world’s population is infected with tuberculosis. Statistics show that new infections occur, though at a relatively low rate of one person per second. However, considering the fact that most of the infections result in death, this shows that the disease is rather severe.

For the purpose of this work, the study will be conducted on the following basis:

  • Aetiology
  • Sources
  • Epidemiology
  • Transmission
  • Signs and symptoms
  • Treatment and control
  • Diagnosis

Aetiology

Tuberculosis is caused by a bacterium called Mycobacterium tuberculosis. It is usually abbreviated as TB. The causative organism is a mycobacterium that occurs in human beings and domestic animals. These are acid-fast organisms that are resistant to a wide range of environmental conditions. Some pathologically important species of these organisms are of two species named bovis and avium. The former is found to be more prevalent in sheep, goats, cattle, and human beings. The latter affects poultry mostly. 

Sources

The causative organism is found in the environment where it is dropped by animals through urine, feces or milk. The organism may be found also in the air. This is caused by coughing or sneezing by human beings. For human beings, milk is a major source of the disease. The organism was the basis for the pasteurization process. It was investigated and found out that all pathogenic microorganisms in milk are vegetative in nature. It was also found out that these pathogens can be destroyed by mild heat treatment that preserved physical and chemical properties of milk. The challenge was to come up with a process that could ensure safety. In doing so, scientists managed to determine the most heat-resistant microorganism. This was found to be the causative organism responsible for TB. Consequently, this was made to be the basis for milk safety. Thus, it was assumed that if the most heat-resistant microorganism could be destroyed, all other pathogens could be destroyed as well.

Epidemiology

The disease affects both human beings and domestic animals. For human beings, it is a more severe case than for animals. In fact, the disease is unapparent in animals. This usually causes a difficulty in curbing the disease because when animals get the infection. It remains in an unapparent condition for a long time and during this period, they keep on discharging the organism to human beings and other animals without any identification. The treatment cannot be initiated after the illness is detected. In some human cases, the disease is also latent. Among these cases, about 10% of latent infections eventually result in active diseases. The disease has been found to be on the rise among immune-compromised individuals. There has therefore been a trend showing increasing prevalence of the disease among people with HIV and AIDS. The distribution of the disease is not uniform across the globe, with more positive cases being observed in less developed countries. In these countries, the disease is attributed to poverty which results in malnutrition. Associated with this is malnutrition and overcrowding. It is also a major risk for medical practitioners. This is because they may be in a very close association with patients who suffer from the disease.

Transmission

In animals, the major route of transmission is by coitus or sexual route. In human beings, the major route of infection is through inhalation of air contaminated with the spores or vegetative cells of the tubercle bacterium. The organisms usually affect the lungs and can be expelled with fluids from the respiratory tract. The sputum is the major route of exit of the organism from the host’s body. This is why it is mostly spread through inhalation. The process of transmission involves coughing or sneezing where the organism is released into the atmosphere. From here, it can be inhaled by other individuals.

Clinical signs and symptoms

The organism attacks the lungs mostly. In the lungs, it causes an acute inflammation of the lungs, which results in chronic pneumonia. The resultant signs are constant coughing, chest pains, and dyspnea (difficulty in breathing). In animals, the organism can localize in the uterus to cause damage to the endometrial walls. This results in release of pus through the vagina. In animals, it can also localize in the udder where it causes mastitis. In this form, it is very critical because it occurs in a latent condition and can continue to infect milk consumers if the milk is taken raw. From the lungs, the organism then gets to the blood to cause military TB. In this case, the organism forms tubercles. The disease in this form is very acute and the death is almost inevitable. In human beings, the injury of the lungs makes the sputum be bloodstained.

Diagnosis

The initial diagnosis is based on the pathognomonic signs. The signs such as difficulty in breathing and coughing are quite characteristic. These are followed by a confirmatory test carried out by culturing the organism in a selective medium from sputum. The organism can also be gram-stained where it stains weakly positive because it has an additional lipid layer compared to gram-positive organisms. A universally accepted method is the one that involves injecting an extract of the organism intradermally and if a reaction occurs, the test is considered positive.

Treatment and control

Treatment of animals that are intended to be used as human food is not allowed because necessary drugs can cause resistance to TB drugs in human beings. If the treatment is done in animals, products from such animals are withdrawn. The treatment for human beings and animals requires the use of the same drugs called isoniazid drugs. The treatment involves a long process that can take months.

Control of TB is done best by beginning with control in animals. In animals, frequent tuberculin tests are carried out. In case an animal is found to be positive, it is supposed to be isolated from the rest of the herd. In case of an outbreak, the treatment can be done followed by withdrawal of the products from sick animals. The best way to avoid spread during an outbreak is by imposing quarantine. In human beings, good hygiene can be practiced. This can involve avoiding overcrowding and proper milk pasteurization. The most acceptable way is, however, by vaccination. The vaccine is derived from Mycobacterium bovis in a weakened form. The vaccine is commonly known as BCG and is given to infants. It gives a life-long protection. Because of the high rate of infection and the risk involved, a very large campaign has been put forward by WHO. This has shown a positive result with a decrease in the rate of infection.

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