Mycobacterium bovis infection in human

In mammals, tuberculosis is caused by members of the Mycobacterium tuberculosis complex, which are Gram positive, acid-fast bacterial rods in the family Mycobacteriaceae.

In the United States, the majority of tuberculosis (TB) cases in people are caused by Mycobacterium tuberculosis (M. tuberculosis). Mycobacterium bovis (M. bovis) is another mycobacterium that can cause TB disease in people.

M. bovis is most commonly found in cattle and other animals such as bison, elk, and deer. M. bovis is a slow-growing (16- to 20-hour generation time) aerobic bacterium.

M. bovis is a member of the Mycobacterium tuberculosis complex, which includes M. tuberculosis. M. bovis can also jump the species barrier and cause TB in humans.

In people, M. bovis causes TB disease that can affect the lungs, lymph nodes, and other parts of the body. However, as with M. tuberculosis, not everyone infected with M. bovis becomes sick. People who are infected but not sick have what is called latent TB infection (LTBI).

Clinically, tuberculosis (TB) caused by M. bovis in humans is indistinguishable from TB caused by M. tuberculosis. Specific diagnosis of Mycobacterium infection may be achieved only by using a series of laboratory tests, including mycobacterial growth characteristics, biochemical properties, susceptibility to pyrazinamide (PZA), and molecular methods.

Bovine TB is not only a relevant zoonosis, with an important economic burden (up to hundreds of millions of euro annually in Europe), but also a relevant human health threat that can spread to humans through inhalation of infectious droplet nuclei and by ingestion of raw milk, than being relevant for public health.

The advent of pasteurization, followed by the establishment of control programs in cattle, have made clinical cases uncommon in many countries.
Mycobacterium bovis infection in human

Symptoms of tuberculosis

Tuberculosis is an airborne disease caused by the bacterium Mycobacterium tuberculosis. It is a contagious infection that usually attacks lungs and it can also spread to other parts of the body, like brain and spine.

M. tuberculosis is carried in airborne particles, called droplet nuclei, of 1– 5 microns in diameter. Infectious droplet nuclei are generated when persons who have pulmonary or laryngeal tuberculosis disease cough, sneeze, shout, or sing. Depending on the environment, these tiny particles can remain suspended in the air for several hours.

Symptoms are usually mild and tend to present over a period of weeks, months, or sometimes years. The classic symptoms of tuberculosis in the lungs include:
■ Cough lasting more than three weeks
■ Unexplained weight loss
■ Low-grade fever
■ Night sweats

Chest symptoms are often nonspecific, and can mimic virtually any respiratory condition: cough is almost always present, with sputum production, possibly chest pain and/or dyspnoea as accompanying symptoms.
Symptoms of tuberculosis

Mycobacterium africanum

Mycobacterium africanum, a member of the Mycobacterium tuberculosis complex, is endemic to West Africa. M. africanum causes up to half of human tuberculosis (TB) in West Africa. It was first described as a distinct subspecies within the Mycobacterium tuberculosis complex (MTBC) by Castets and colleagues in 1968, when it was isolated from sputum of a tuberculosis patent in Senegal.

The MTBC consists of M. africanum, M. bovis, M. canettii, M. microti, and M. tuberculosis. They are obligate pathogens and the etiologic agents of tuberculosis, so named because of the nodular lesions observed in lungs, which are termed tubercles.

Although all members of MTBC might cause disease in humans, M. tuberculosis and M. africanum are the primary cause of disease in humans globally, whereas M. bovis primarily causes disease in cattle.

The disease produced by M. africanum is similar to that caused by M. tuberculosis or M. bovis, and like M. tuberculosis, this organism is likely spread by aerosol transmission.
Mycobacterium africanum

Signs and symptoms of tuberculosis infection

Tuberculosis (TB) is a disease caused by germs that are spread from person to person through the air. TB usually affects the lungs, but it can also affect other parts of the body, such as the brain, the kidneys, or the spine. The disease caused by any one of a group of bacteria collectively known as the Mycobacterium tuberculosis complex. These mycobacteria include:
•M. tuberculosis (including subspecies M. canetti)
•M. bovis
•M. bovis BCG 
•M. africanum
•M. caprae 
•M. microti 
•M. pinnipedi 

When these bacteria enter the lungs, they are usually walled off into harmless capsules (granulomas) in the lung, causing infection but not disease. These capsules may later wake up weeks, months or decades later causing active TB disease.

The general symptoms of TB disease include feelings of sickness or weakness, weight loss, fever, and night sweats. The symptoms of TB disease of the lungs also include coughing, chest pain, and the coughing up of blood. Symptoms of TB disease in other parts of the body depend on the area affected.

TB disease can also involve multiple sites at once (disseminated TB disease). Other sites of non-respiratory TB disease include:
• Peripheral lymph nodes (TB lymphadenitis)
• Central nervous system (e.g., TB meningitis, tuberculoma)
• Abdominal cavity and/or digestive system
• Genitourinary system
• Bones and/or joints

Symptoms are usually mild and tend to present over a period of weeks, months, or sometimes years. TB disease symptoms are often initially mistaken for a smoker’s cough, allergies, or chronic bronchitis from a lingering cold or flu infection.
Signs and symptoms of tuberculosis infection

Mycobacterium tuberculosis

One third of all humans are thought to be infected with a causative organism, Mycobacterium tuberculosis. TB kills more women than any cause of maternal mortality.

Mycobacterium tuberculosis is a rod-shaped, slow growing, gram positive bacterium. The Mycobacterium tuberculosis cell wall has a high fatty acid content, which makes it hydrophobic and resistant to noral fluid.

The cell wall absorbs a methylene-blue dye and maintain a red color despite attempts at decolorization, hence the name acid-fast bacilli.

Mycobacterium tuberculosis

In patients with active tuberculosis, Mycobacterium tuberculosis bacilli from granulomas are released into the bronchi and are spread through coughing. The aerosols produced contained droplet nuclei and survive for quite long period of time outside the body.

It is estimated that each infected person infects on average 20 other individuals. Once involved with cycle of infection and disease, the only escape leading to no further disease is by death, by modern scientific chemotherapy of active disease or by preventive therapy in the absence of current disease.

Generally, a cough with a progressive increase in production of mucus, coughing up blood, fever, loss of appetite and weight loss are common symptoms of tuberculosis.
Mycobacterium tuberculosis

Short History of Tuberculosis

Short History of Tuberculosis
In the Paleolithic period, people lived as wanderers, did not settle in villages or permanent locations, and do not congregate in large groups.

While tuberculosis may have occurred sporadically, it an other infections disease probably did not occur in epidemic form.

Beginning in about 8000 BC, humans developed primitive agricultural techniques that allowed settlement in permanent sites and with this development came the domestication of cattle, swine and sheep.

In all probability, tuberculosis occurred more frequently in this setting, but it nevertheless remained rare.

Tuberculosis probably occurred as an endemic disease among animals long before it affected humans. Mycobacterium bovis was the most likely infecting organism and the first human infections may have been with Mycobacterium bovis.

Since Mycobacterium tuberculosis infects all primate species, it is also possible that this species existed in subhuman primates before it became established in humans.

Tuberculosis probably occurred as a sporadic and unimportant disease of humans in their early history. Epidemic spread began slowly with increasing population density.

This spread and the selective pressure it has exerted have occurred at different times around the globe.

The epidemic slowly spread worldwide as a result of infected European travelling to and colonizing distant sites.

In the 1700s and early 1800s tuberculosis prevalence peaked in Western Europe and the United States and was undoubtedly the largest cause of death.

100 to 200 years later it had spread in full force to Eastern Europe, Asia, Africa and South America.

1.6 millions death worldwide due to tuberculosis in year 2002 alone. Currently tuberculosis kills 1.8 million people each year. However scientist believed that can be averted by 2050 with better testing, drugs and vaccines.

Treatment from 1995 to 2008 saved six millions lives. However 36 millions infected with tuberculosis during 1995-2008 were cured and incidence of the lung wasting disease has begun to regress, but only by about one percent per year.
Short History of Tuberculosis

Mycobacterium tuberculosis

Mycobacterium tuberculosis
Mycobacteria are aerobic and nonmotile bacteria that are characteristically acid-alcohol fast. Mycobacterium tuberculosis, along with M. bovis, M. africanum, and M. microti all cause the disease known as tuberculosis (TB) and are members of the tuberculosis species complex.

Each member of the TB complex is pathogenic, but M. tuberculosis is pathogenic for humans while M. bovis is usually pathogenic for animals. Mycobacterium tuberculosis, then known as the "tubercle bacillus," was first described on March 24, 1882 by Robert Koch. Mycobacterium tuberculosis is the etiologic agent of tuberculosis in humans. Humans are the only reservoir for the bacterium.

Mycobacterium tuberculosis is known as "acid-fast bacilli" because of their lipid-rich cell wall, which is relatively impermeable to various basic dyes unless the dyes are combined with phenol. Only about 10% of people infected with M tuberculosis ever develop tuberculosis disease. Many of those who suffer TB do so in the first few years following infection, but the bacillus may lie dormant in the body for decades.

Although most initial infections have no symptoms and people overcome them, they may develop fever, dry cough, and chest x-ray abnormalities. Tuberculosis (TB) is the leading cause of death in the world from a bacterial infectious disease. The disease affects 1.8 billion people each year which is equal to one-third of the entire world population.

In the United States Tuberculosis is on the decline. In 2007 a total of 13,293 cases were reported. The TB rate declined to 4.4 cases per 100,000 populations, the lowest recorded rate since national reporting began in 1953. Despite this overall improvement, progress toward tuberculosis elimination has slowed in recent years; the average annual percentage decline in the tuberculosis rate slowed from 7.3% per year during 1993--2000 to 3.8% during 2000--2007. Also, since 1993 there has been a gradual decline in the number of tuberculosis patients with co infection with HIV, and the number of cases of multiple drug-resistant tuberculosis has gradually dropped.
Mycobacterium tuberculosis