Metabolic balancing between mosquito and malaria parasites

December 13, 2019
A hungry mosquito is not a good host for malaria parasites. Elena Levashina's team at the Max Planck Institute for Infection Biology in Berlin showed that both, mosquito and parasite, tap into the same resources for their reproduction. The parasites enter the mosquito with a blood meal that is meant to serve to mosquito ovary development. Inside the mosquito, the parasites reproduce and develop, for which they draw energy from the mosquito's nutrient resources. However, if the mosquito consumes many nutrients for its ovary development, little remains for the parasites. The researchers have proven that the duration of nutrient consumption during mosquito egg maturation is decisive for the development of parasites. This could answer the question of why some mosquito species are better at transmitting malaria than others. The results have now been published in Nature Communications.

A female mosquito bites humans to secure nutrients for its own egg production. The blood meal not only nurtures the eggs, but also makes mosquitoes dangerous vectors of infectious diseases. Blood-borne pathogens such as the malaria parasite use the mosquito’s biting behavior to be transferred from one to the next individual.

Only few malaria parasites are taken up with a mosquito blood meal. Therefore, parasites need to multiply in the mosquito to increase the chances of being transmitted to another person. The parasites get necessary fats, sugars and amino acids from the mosquito. However, the mosquito consumes most of the nutrients for its own reproduction. It is essential for parasites that the mosquito does not exhaust their nutrient storage for its own egg production. In an earlier publication, Elena Levashina and her team showed that malaria parasites mainly use the surplus nutrients of the hosting mosquito after it had completed its own reproductive cycle.

In the current work, the researchers took a closer look at what will happen to the parasites if the mosquito exhausts its resources during egg development. By identifying a decisive controlling factor, micro-RNA-276, they increased the duration of mosquito nutrient consumption. In the absence of miR-276, nutrient degradation for egg production lasted longer. As expected, directing more nutrient to reproduction, increased mosquito fertility. However, this increase in fertility counteracted the development of malaria parasites. As a consequence, fewer transmissible forms of the parasite were generated for the next mosquito bite.

So far, little is known about the mosquito factors that influence transmission of malaria parasites. "By linking mosquito metabolism and parasite development our study offers an insight into why some mosquitoes transmit more parasites than others. This information is important in the fight against malaria," says Lena Lampe, first author of the study.  Mosquito metabolism could therefore be a promising target for malaria control. 

Mosquitoes are fed donated blood in the laboratory. The mosquitos use the nutrient-rich blood meal for their egg production - but malaria parasites are also the beneficiaries of this nutrient supply.

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