13 July 2011
By Kounteya Sinha
Port Blair, India
A mutant strain of Hepatitis B – a viral infection that causes chronic liver failure, and is 50 to 100 times more infectious than the HIV – has been isolated from the ancient and dwindling Nicobarese tribe of the Andaman and Nicobar Islands.
Scientists from the ICMR’s Regional Medical Research Centre (RMRC) in Port Blair have found the deadly virus in some members of the tribe even after they were vaccinated against the disease. Some were re-infected with Hepatitis B after vaccination. The mutant strain is highly virulent and resistant to all vaccines, which could spell doom for this ancient tribe, if not immediately controlled.
The RMRC researchers, therefore, collected fresh blood samples from around 800 Nicobarese (250 of whom have been vaccinated, and the rest unvaccinated) from the two villages of Tamalu and Lapathy in last September and June to document the extent of the mutation.
RMRC director Dr Palaru Vijayachari told ToI that the prevalence of Hepatitis B infection has always been alarmingly high among the Andaman and Nicobar Islands’ tribes.
Studies conducted between 2000-2003 found a 24% prevalence of Hepatitis B infection among the Nicobarese, and nearly 66% infection among the Jarawa tribes. A mutant strain is more of a worry, he said.
Researcher Haimanti Bhattacharjee added: "The samples will tell us how much protection the vaccine has given to those who were vaccinated earlier and also how many are carrying the vaccine escaped mutant. Hepatitis B’s transmission among these tribes is mainly via tattoos and sharing of needles, sexual transmission and through mother and child transmission. If the mutant strain is found to be widespread among the tribe members, it would be highly dangerous."
Dr Vijayachari said 1,800 Nicobarese children were vaccinated against Hepatitis B after 2005. Three years later, it was found to have a 97% protection. However, the protection rate reduced to 85% after another three years.
"The fresh blood samples will also pinpoint how much protection rate is right against Hepatitis B among those vaccinated earlier. A real time PCR test will pick up infections more precisely," Bhattacharjee said.
Dr Vijayachari plans to start genetic studies, including sequencing of the isolated mutant Hepatitis virus after August, to know its weakness.
The Andaman and Nicobar Islands is home to six indigenous population groups. The indigenous tribes account for about 8% (30, 000 of 350, 000) of the islands’ population. The Nicobarese constitute more than 95% (29, 000 of 30, 000) of the population.
"Since Hepatitis B prevalence is very high among the tribes in Andaman and Nicobar, they end up becoming long time carriers of the virus. We are carrying out studies on estimation of viral load among chronic carriers and treating high-risk persons with antiviral drugs to prevent chronic squeal," Dr Vijayachari said.
About 2 billion people worldwide have been infected with the virus, and about 350 million live with chronic infection. An estimated 600, 000 die each year due to the acute or chronic consequences of Hepatitis B. About 25% of adults who become chronically infected during childhood later die from liver cancer or cirrhosis (scarring of the liver) caused by the chronic infection.
Hepatitis B virus (HBV) is transmitted between people by contact with blood or other body fluids of an infected person. Modes of transmission are the same for the HIV. Howeverunlike the HIV, the HBV can survive outside the body for at least seven days.
During that time, the virus can still cause infection, if it enters the body of a person who isn’t infected.
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