Japanese scientists have developed a genetically modified mosquito that vaccinates as it bites and could help prevent the spread of malaria.

The research team has created an insect producing a natural vaccine protein in its saliva, which is injected into the bloodstream when it bites.

The 'prototype' mosquito carries a vaccine against Leishmania, another potentially fatal parasite disease spread by sand flies, reports dailymail.co.uk.

Leishmania infection can cause painful sores, fever and weight loss and if untreated may destroy the liver and spleen.

The findings revealed that mice bitten by the vaccinating insect generated antibodies against the Leishmania organism, indicating immunisation.

'Following bites, protective immune responses are induced, just like a conventional vaccination but with no pain and no cost,' said study leader professor Shigeto Yoshida, from Jichi Medical University in Shimotsuki, Japan.

'What's more, continuous exposure to bites will maintain high levels of protective immunity, through natural boosting, for a life time. So the insect shifts from being a pest to being beneficial,' Yoshida added.

Scientists are still working on developing an effective malaria vaccine, so Yoshida's study was very much a 'proof of concept'.

However, ethical considerations may also get in the way of using 'flying vaccinators' to control malaria, he said.

The study was published in the journal Insect Molecular Biology.