"By eight days post-infection, head lice had killed or contained the invading B. quintana, whereas the bacteria were still proliferating and spreading in body lice," the researchers reported.
The team cannot yet say why head and body louse immune responses differ from one another, but Pittendrigh hypothesizes that the body louse has a reason to be more tolerant of bacterial infection.
"Head and body lice have beneficial bacteria living inside them," he said. "These bacteria make vitamins that the lice need to grow and survive. Body lice tend to grow larger than head lice. It may be that a suppressed immune system allows body lice to grow more of the bacteria that make the vitamins they need, and they grow larger."
The body louse's dampened immune response would allow other invading bacteria, such as those that cause disease in humans, to also survive in its gut, he said.
"So body lice may grow bigger, but they also are more likely to get sick with the trench fever bacteria and pass the disease to humans," Pittendrigh said.
The study team also includes researchers from Purdue University, Seoul National University, the University of California at San Francisco, the University of Massachusetts and the University of Illinois department of animal biology.
|Contact: Diana Yates, Life Sci Editor, U. of I. News Bureau|
University of Illinois at Urbana-Champaign