THIRUVANANTHAPURAM: Thousands of residents in the state capital are under the threat of water-borne diseases with the Kerala Water Authority supplying contaminated water infested with blood worms and coliform bacteria. KWA officials confirmed the presence of blood worms in the water pumped from the Vellayani Lake which caters to a large section of residents at Nemom, Karamana, Kalliyoor, Venganoor, Vizhinjam, …