FOOD FOR THOUGHT

Tuberculosis

by: Chita Heap

There are currently more cases of tuberculosis or TB in the world than at any other time in history. In 1993 the World Health Organization (WHO) declared TB a global health emergency, and introduced a global plan to stop tuberculosis with the aim of saving 14 million lives between 2006 and 2015. With the recent emergence of new drug resistant strains of TB, this target represents a real challenge.

TB (short for tubercles bacillus) is a common and in some cases deadly infectious disease which usually attacks the lungs, but which can also affect other parts of the body. When the disease becomes active, 75% of the cases comprise pulmonary TB which infects the lungs.

TB is spread through the air when others who are suffering from an active form of TB cough, sneeze, or spit. Every time a person sneezes they can release into the air up to 40,000 droplets, each of which is capable of spreading the disease. In an enclosed space these droplets can remain in the air for several days, such that people in close contact have an estimated infection rate of 22%. A person who has active but untreated TB can infect between 10 and 15 other people per year.

This disease can also be transmitted by sharing a glass or sharing a toothbrush, both of which can transmit infected saliva.

Most infections in humans result in an asymptotic or latent infection, with one in ten of such cases eventually progressing into an active disease, which if left untreated, kills more than 50% of its victims.

The classic symptoms are a chronic cough which may last for more than three weeks, blood in the saliva, fever, night sweats, weight loss and also fatigue. The main problem with TB diagnosis arises from the difficulty of culturing this slow growing organism in the laboratory. This can take from 4 to 12 weeks to complete.

Treatment is difficult and requires a long course of multiple antibiotics, whilst close contacts such as family members need to be screened too and given treatment if required. A complete medical evaluation for TB should include a medical history, a physical examination, a chest X-ray, microbiological smears, and cultures, and a microscopic examination of body fluids.

It may also be necessary to include a tuberculin skin test or serological test. Tuberculin skin tests can prove unreliable in the presence of various other conditions such as malnutrition, but most notably the presence of the active form of tuberculosis itself. A more reliable conclusion can be procured from a blood test.

New tests have recently been developed that are both fast and accurate. One such molecular diagnostics test gives results in 100 minutes and is currently being offered to 116 low and middle income countries at a discounted rate with support from the World Health Organization.

Children can be vaccinated to protect them both from TB and also from more serious forms of TB such as meningitis. No vaccine is available however to provide reliable protection for adults. In 1993 some 85% of infants were immunized in 172 countries throughout the world, though in South Africa which has the highest rate of TB, all children under the age of three are vaccinated.

Antibiotic resistance is becoming a growing problem particularly in the case of multi-drug-resistant tuberculosis. Prevention relies mainly upon screening programs and vaccination.

Effective TB treatment is difficult due to the unusual structure and chemical composition of the bacteria, and treatment over a period of 6 to 24 months is often required to completely eliminate mycobacteria from the body. Latent TB is often treated with a single antibiotic, whilst an active TB disease is best treated with a combination of several antibiotics.

Some patients can go on to develop a drug resistant form of TB during therapy due to inadequate treatment, to not taking the prescribed regimen appropriately, or through using low quality medication. Drug resistant TB is a public health issue in many developing countries since treating the disease takes longer and requires the use of more expensive drugs.

One third of the world’s population is thought to be infected with tuberculosis, and new infections occur at a rate of about one per second. In 2007 there was an estimated 13.7 million chronic active cases, 9.3 million new cases, and 1.8 million deaths which occurred mostly in developing countries like the Philippines.

In addition more people in developed areas of the world contracted TB due to a compromise of their immune system due to higher exposure to immunosuppressive drugs, substance abuse, and AIDS. Some people with other conditions such as diabetes and leukemia are at higher risk than others, as are those with a low body weight. Those with an increased body weight are at lower risk.

Others at increased risk are intravenous drug users who share needles, those with a history of inadequately treated TB, and those who suffer from AIDS. It has been found that 30 to 40% of AIDS patients also have TB.

The distribution of TB is not uniform across the globe. Some 80% of the population in many Asian and African countries tested positive in tuberculin tests, whilst only 5 to 10% of people in the US tested positive. This is in part due to a better standard of hygiene, better education, and less crowded living conditions. Hereditary factors also play a part resulting in a higher resistance to the disease in people of European origin.
Most agree that there is an urgent need to develop a newer more effective vaccine that would prevent all forms of TB, including drug resistant strains. Several new vaccines are being developed to prevent TB infection, some of which can be effectively administered without needles. These vaccines have already been tested successfully in humans and are now undergoing extended testing in TB endemic regions.

Basic preventative measures to limit the transmission of TB include ensuring that your house is well ventilated, covering your mouth with your hand or else with a tissue whenever you sneeze or cough, and by avoiding spitting. In the UK spitting in public incurs a penalty of 1,000 pounds, or P.65, 000 in Philippines money, which gives some indication of how seriously this health hazard is regarded in the west./TE