By Jeremy Clarke NAIROBI, March 22 (Reuters) - Dire living conditions in Africa's crowded slums are encouraging the spread of a multi-drug resistant strain of tuberculosis that kills nearly half of those treated, an aid agency said on Thursday. Tuberculosis, which kills an estimated 1.5 million Africans a year, is spread through the air like the common cold, and health workers say poor ventilation and lack of sunlight dramatically increase infection rates. The highly resistant strain, MDR-TB, has flourished in shanty towns where many live in dark, crowded huts, the aid agency Medecins Sans Frontieres (MSF) said. MDR-TB does not respond to the two most powerful TB drugs available, so patients are forced to take a cocktail of up to 30 tablets a day, MSF staff added, speaking at a media event in a Nairobi slum ahead of global World Tuberculosis Day on Saturday. The extra medicines cause vomiting, diarrhoea and severe depression in many cases, they said. Mathare slum on the outskirts of the Kenyan capital Nairobi is "the perfect breeding ground" for TB in general and for the multi-drug resistant strain in particular, the agency said. "No windows and five or six people to a room. Not enough light and no ventilation -- 70 to 80 percent of our patients live like this," the MSF head of mission in Kenya, Christine Genevier, told reporters at their Mathare clinic. The clinic is treating 600 patients for TB. Most are also infected with HIV, the virus that causes AIDS. "When our classical treatment for TB fails, we have to treat for MDR-TB using drugs developed nearly 50 years ago," Genevier said. Around 45 percent of patients who undertake the 18-24 month programme do not live to complete it, MSF said in a report. The World Health Organisation estimates there are up to 1.5 million cases of MDR-TB in the world today, with 420,000 new infections and 116,000 deaths per year.
