JOHANNESBURG, 21 January 2008 (IRIN) - Two cases of extensively drug-resistant tuberculosis (XDR-TB) have been confirmed in Botswana, health officials said.

"The two cases were picked up during a routine survey for multidrug- resistant TB (MDR-TB)," Setshwano Mokgweetsinyana of the Department of Public Health, told IRIN. The survey also confirmed 100 cases of MDR-TB.

MDR-TB strains cannot be treated by at least two of the main first-line TB drugs, while XDR-TB is resistant to most first and second-line drugs, severely limiting treatment options. According to the World Health Organisation (WHO), XDR-TB strains have now been detected in 41 countries, including South Africa and Mozambique. Most southern African countries lack the laboratory facilities to detect XDR-TB.

Patients usually develop MDR-TB as a result of not completing treatment for an earlier bout of TB; failure to complete the lengthy MDR-TB treatment creates the risk that they will develop XDR-TB.

The two XDR-TB cases were admitted to the national referral centre, Princess Marina hospital in the capital, Gaborone. Mokgweetsinyana said one of the cases had been a mineworker in South Africa, while the other had never been out of the country. "Their immediate relatives have been isolated and are being tested for XDR-TB."

Botswana has been conducting periodic tests for MDR-TB since research published in 2005 in the British medical journal, The Lancet, indicated that the incidence of resistance to anti-TB drugs in the country had been increasing since 1995, said Mokgweetsinyana

The research, led by Lisa Nelson, of the Centers for Disease Control and Prevention, Atlanta, USA, found that resistance to at least one drug in new TB patients rose from 3.7 percent in 1995 to more than 10 percent in 2002, and that 60 percent of the group tested were also infected with HIV.

Mokgweetsinyana said Botswana has a high incidence of TB, with 500 cases per 100,000 people reported every year. "It is a very serious problem, as most of those who are infected also have HIV."

People with immune systems compromised by HIV are 50 times more likely to develop active TB, but the sputum tests most commonly used to detect TB often fail to recognise it in HIV-infected patients. According to UNAIDS, Botswana has one of the world's highest HIV prevalence rates - 24.1 percent among people aged 15 to 49.

XDR-TB strains have already killed over 200 people in South Africa, and pose a serious threat to this part of the continent, where HIV prevalence is the highest in the world

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