ISLAMABAD: Two Siblings , a three-year-old boy and seven-year-old girl have been killed after a snake bit them while they were sleeping outside their house.According to a private news channel, the people in their area said that they had spotted two poisonous snakes in the fields after heavy monsoon rains.The snakebite remains a significant problem of rural areas.Every year around 50,000 people die in Pakistan due to snake-bite.Only five to six per cent anti-venom vaccine is prepared by the National Institute of Health (NIH) against the required 150,000 vaccines per annum and that too is not easily available in the markets.