A team of scientists from Edinburgh University found that well-fed water fleas were more contagious than those given less to eat.
Their study, published in the journal Biology Letters, found that some of the well-fed fleas also lived longer, giving them more time to multiply and spread infection.
Nutrition may also play an important role in the spread of disease, said scientists, adding that the finding may lead to new ways to monitor the spread of infections in large populations.
"If we have an idea of which individuals transmit a lot of disease, we will be better able to stop its spread," the paper quoted Dr Pedro Vale, of Edinburgh's School of Biological Sciences, who led the study, as saying.
"We know that contact between individuals is important; but now we know that, for some animals at least, nutrition may also play an important role in the spread of disease," he added.