Mosquito behavior may be immune response, not parasite manipulation

May 22, 2013
This is a micrograph of a mature oocyst of a malaria parasite. Credit: Read Group, Penn State

Malaria-carrying mosquitos appear to be manipulated by the parasites they carry, but this manipulation may simply be part of the mosquitos' immune response, according to Penn State entomologists.

"Normally, after a female mosquito ingests a blood meal, she matures her eggs and does not take another one until the meal is digested," said Lauren J. Cator, postdoctoral fellow in entomology and a member of the Center for Infectious Disease Dynamics, Penn State. "If infected, however, mosquitos will wait to eat until the developing within the gut mature and migrate to the salivary glands."

It was thought that fasting until malaria could be transmitted was beneficial to the malaria parasite because if the was not feeding, she was not being swatted. The return of hunger seemed to correlate with the migration of parasites to the salivary glands. The hungrier the mosquitos are, the more they feed and the more chances to find new hosts.

Cator and colleagues who included Justin George, postdoctoral fellow; Simon Blanford, research associate; Courtney C. Murdock, postdoctoral fellow; Thomas C. Baker, professor of entomology; Andrew F. Read, professor of biology and entomology and alumni professor in biological sciences; and Matthew B. Thomas, professor of , used a and showed that indeed female mosquitos behaved in this way.

It was unclear if the malaria parasite caused the mosquitos' response or if something else was in play. The researchers also looked at how the infected mosquitos searched for meals and how they responded to the smell of humans. Although the mosquitos used were biting mice, they also look to humans for a meal.

This is a micrograph of malaria sporozoites being released from a mosquito salivary gland. Credit: Read Group, Penn State

George ran the experiments testing the mosquito's during various stages of parasite maturity and found that the mosquitos responded to human smell much more readily once the parasites were ready to transfer to their hosts. The same was found of the meal-seeking behavior of the mosquitos.

The researchers dissected the insects to determine the exact stage of the parasite in each mosquito they tested and what they found surprised them. They published their results in the Proceedings of the Royal Society B today (May 22).

"There were mosquitos that took an infected blood meal, but didn't get infected or fought off the infection," said Cator. "These mosquitos behaved in the same way as the infected mosquitos."

The researchers then injected mosquitos with killed E. coli to see the response. While the degree of fasting and food seeking was smaller, the noninfected, E. coli-challenged mosquitos behaved in the same way. They fasted for about the same time and then went searching for a meal. Their responses to human smell and meal searching behavior also mirrored that of malaria-infected mosquitos.

"Recently, a group from the Netherlands published in PLOS and while they were only looking at the mature parasites in the salivary glands, they found the same response to human odor," said Cator. "This supports that the response is a generalized response to a challenge rather than a manipulation by the and that our findings are probably relevant for human malaria transmission."

Explore further: Team publishes evidence for natural alternative to antibiotic use in livestock

More information: 'Manipulation' without the parasite: altered feeding behaviour of mosquitoes is not dependent on infection with malaria parasites: rspb.royalsocietypublishing.or… .1098/rspb.2013.0711

Related Stories

Recommended for you

Researchers capture picture of microRNA in action

Oct 30, 2014

Biologists at The Scripps Research Institute (TSRI) have described the atomic-level workings of "microRNA" molecules, which control the expression of genes in all animals and plants.

Blocking a fork in the road to DNA replication

Oct 30, 2014

A team of Whitehead Institute scientists has discovered the surprising manner in which an enigmatic protein known as SUUR acts to control gene copy number during DNA replication. It's a finding that could shed new light on ...

Cell division, minus the cells

Oct 30, 2014

(Phys.org) —The process of cell division is central to life. The last stage, when two daughter cells split from each other, has fascinated scientists since the dawn of cell biology in the Victorian era. ...

A new method simplifies the analysis of RNA structure

Oct 30, 2014

To understand the function of an RNA molecule, similar to the better-known DNA and vital for cell metabolism, we need to know its three-dimensional structure. Unfortunately, establishing the shape of an RNA ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.