To coax the intruder out their air supply has to be cut off, sending them gasping to the surface of the skin. The sand fly also saddles those it lands on with a minute parasite. Water can carry everything from diarrhoea bugs to the bacteria which causes the much-feared disease cholera. Dr Barnish says utmost care should be taken and recommends the use of bottled water for drinking and teeth cleaning. Even paddling in an inviting looking lake can land you up the creek.
Schistosomiasis is a slow, debilitating infection caught from fresh water in Africa.
It comes from worms which live around the human bladder and intestine. Water can transmit many diseases These centimetre-long worms, once released from the body, infect water snails. The second generation hatch and hunt out another human host, entering through the skin. Maturing in the person's liver, the worms can get lost on their journey back to the bladder or intestine, causing untold damage if they reach the brain or spine. While lassa fever is incredibly rare, with only a dozen cases in America and Europe in 30 years, keeping healthy while travelling is a growing concern.