Malaria parasites can manipulate the body odour of mice, research in the journal Proceedings of the National Academy of Sciences suggests.

Researchers believe parasites may change odours in order to help them with a key stage in their reproduction.

And scientists found the altered scent persists at a critical time when mice have no symptoms but remain infectious.

They are working on further trials to determine whether parasites can affect human smell too.

Scientists from the Swiss Federal Institute of Technology and Pennsylvania State University in the US studied the odour of mice with and without malaria for 45 days.

They found the scent of infected mice was markedly different to non-infected ones. 'Complex life-cycle'

The parasite did not completely alter the smell of the individual - instead it changed the level of compounds already present in mouse odour

And this was particularly noticeable in mice which were still infectious but no longer showed any symptoms of the disease - corresponding to a crucial time in the life cycle of the parasite.

Prof Consuelo De Moraes of Pennsylvania State University and one of the lead authors of the research said: "There appears to be an overall elevation of several compounds that are attractive to mosquitoes."

The study showed mosquitoes were most attracted to mice when the parasites in their bodies were at a key point in their development - a stage when they needed to be passed back to a mosquito in order to reproduce.

Malaria parasites have a complex life-cycle with several stages. They need to develop and mature in both humans and mosquitoes.

Scientists believe parasites may manipulate the host's smell in order to ensure continued survival. 'Attractive to mosquitoes'

Researchers are now working on trials to see if this pattern of odour change can be traced in humans too.

Professor Mark Mescher of Pennsylvania State University who was also involved in the research told the BBC: "One of the major potential values of this research is if it can help us identify people who do not show symptoms of the disease.

"Without symptoms people carry the disease without treatment and still transmit it.

"But there is still a long way to go. In mice we have a very controlled environment. In humans there are so many different factors at play - from diverse environments to diverse genes."

Dr James Logan of the London School of Hygiene and Tropical Medicine who was not involved in the research said:

"This is one of the first convincing studies that demonstrates a significant change in odour compounds from malaria-infected mammals can affect mosquito behaviour.

"The strength of this paper is in the experimental approaches used, combining analytical chemistry, statistical analyses and mosquito behaviour.

"However, this demonstration is in an animal model which may or may not relate to human beings infected with malaria."