Latent Tuberculosis: Indian TB germ not aggressive, says expert

By Syed Akbar
Hyderabad, April 23: If the Lancet's recommendation on latent TB is to be implemented by the UK and other developed nations like the USA, every Indian, who wants to visit these countries, may have to undergo nine-month-long medication for latent TB.
According to bacteriologists, since 75 per cent of latent TB cases are difficult to be detected or likely to be mis-diagnosed, as a precautionary measure every Indian suspect would be made to consume latent TB medicines. This will put a heavy financial burden on individuals and create unnecessary resistance to TB, if the person does not carry latent TB germs. Moreover, even active TB germ in India is "shy" in the sense that it does not spread as aggressively as its counterparts in other countries.
"Suggesting that a person undergo tests for latent TB and putting him on medication is a gross violation of human rights. Unless you find the bacteria in the sputum or the lung damaged, you cannot ask him or her to take medication, which is highly toxic and cause harm to liver. Moreover, diagnosis and treatment of latent tuberculosis are both difficult and uneconomical," warns Dr Niyaz Ahmed, senior pathobiologist and Professor (adjunct), Institute of Life Sciences, University of Hyderabad.
Lancet's recommendation is easily said than implemented. A number of ethical and medical issues are involved in treating people with latent TB. According to Dr Niyaz Ahmed, the Monteux test based on skin reaction to mycobacterial protein components is seriously cross-reactive and could produce false positive and false 
negative results in case of 70 per cent of the Indians. Similar difficulties could be encountered with another test called Interferon-gamma test.
India has so far not experienced any institutionalised outbreak as against the famous fatal outbreaks of New York and Kwazulu Natal. That means the Indian strains are less aggressive and controllable. Indians enjoy a distinct natural protection from latent TB due to the facts that their genetic makeup is different, their strains are different and their immune system is already primed due to a saprophytic antigenic background and/or by 
Helicobacter infection.
The UK should therefore, not be worried for Indians. They should in fact be worried about the Pakistanis and Sri Lankans, who do not have the ancestral strains of TB bacteria (TbD1+) in their countries and could proceed to full blown TB more rapidly than Indians, he said.
Anti TB drugs are poisonous to liver in long course and low dosage or short course could select out drug resistant bacteria. Stating that it has become a fashion in the West to project India as a source of infection, he said the story is worst in case of countries that are dubiously known for their highly virulent multi-drug resistant and extremely drug resistant strains such as South Africa, Russia and the countries of the former USSR.
"In fact, the UK should happily give immigrant status to Indians because it is proved already that the Indian strains of Mycobacteria are of ancestral type (genotype TbD1+) and the treatment success rates of up to 95 per cent have been recorded under the DOTS program. These strains are theorised as ‘shy’ in terms of dissemination as compared to some of the very aggressive genotypes such as Beijing, Africa and Haarlem," Dr Niyaz Ahmed said.