The danger of human transmission is determined by the relative frequency of two mosquito species.
Malaria is transmitted by mosquitos, however not all malaria-infected mosquitos are the same. In a new study, an international team lead by Elena Levashina of Berlin’s Max Planck Institute for Infection
Biology discovered that some mosquito species are better at transferring Plasmodium parasites than others. Thousands of mosquitos were collected by the researchers in four African countries.
They demonstrated that the dynamics of malaria parasites during a rainy season are influenced by species composition rather than the total number of mosquitoes using econometric methods.
What is malaria?
Malaria is a dangerous disease that spreads when a human is bitten by an infected mosquito. Mosquitoes can be infected by tiny parasites. The mosquito injects malaria parasites into the person’s bloodstream when it bites.
Malaria is caused by a parasite called Plasmodium, which is transmitted to people via mosquitoes. Only a few mosquito species are capable of transmitting the parasites. Some species, in particular, have a high probability of transmitting the parasite and are therefore regarded particularly harmful.
Elena Levashina identified the TEP1 gene in mosquitoes eighteen years ago in a lab environment. It renders mosquitoes more or less resistant to the parasite, depending on the type, and thereby reduces the mosquito’s ability to transmit the deadly disease. It’s been unclear whether this laboratory observation can be transferred to nature until now.
Elena Levashina’s team conducted a field study in Africa to verify that TEP1-resistant mosquitoes exist in nature. For four years, the worldwide team collected and evaluated thousands of mosquitoes alongside researchers in Mali, Burkina Faso, Kenya, and Cameroon.
The researchers discovered the same variants of the TEP1 gene in wild mosquito species as they did in the lab. Surprisingly, the resistant variant of the gene was found only in Anopheles coluzzii and not in Anopheles gambiae, two mosquito species that are otherwise closely related.
How common is malaria?
Malaria is very common in hot and humid tropical areas. Every year, roughly 2,000 people in the United States contract malaria. Malaria affects around 220 million people worldwide each year. Africa and South Asia account for the vast bulk of these cases. Every year, over 450,000 individuals die as a result of the disease.
The researchers used a novel strategy to collect thousands of mosquito samples over the course of two rainy seasons.
Following this achievement, the team turned its attention to a collection site in Mali’s Sahel zone, where the two species breed together.
They noticed that the size and species mix of the mosquito population changed during the season and sought to test how variations in mosquito populations affected Plasmodium abundance using a system developed for predicting stock prices.
This test was utilized by Markus Gildenhard, a scientist in Elena Levashina’s team, to develop a model for predicting the amount of mosquitos infected with parasites.
The researchers next looked to see if characteristics like temperature, total number of mosquitoes, and mosquito species ratios could help predict parasite abundance.
Species composition determines parasite abundance
Only the ratio between the two sympatric species was predictive of parasite abundance, which was a complete surprise. Until today, A. coluzzi and A. gambiae were both thought to be hazardous malaria parasite carriers.
The model, on the other hand, anticipated that increasing the percentage of A. coluzzi, a mosquito species that carries the TEP1 resistant variant, would reduce the number of infected mosquitos.
An increase in the susceptible A. gambiae, on the other hand, increased the number of infected mosquitos. The rise of infected mosquitoes will have a direct influence on human Plasmodium parasite exposure.
This type of model is critical for predicting how swiftly changing climate conditions would affect regional malaria incidence in Africa and around the world.
Because the genetic makeup of mosquito populations influences malaria transmission, more research into the variables that shape mosquito populations is needed.
Who might get malaria?
More than 90% of malaria deaths occur in Africa. The virtually majority of the victims are children under the age of five. Malaria is extremely uncommon in the United States. Infected people who travel to the United States can transfer the disease to others if a mosquito bites them and then bites someone else.
Researchers must identify and target the local mosquito species. That promote Plasmodium spread in order to develop instruments for genetically-based control methods.
The use of gene drive technology in mosquitos could provide a new and appealing malaria-fighting technique. Researchers have devised a way for introducing desired genes into mosquito species.
However, as Elena Levashina’s research demonstrates, the effectiveness of the intervention is determined by the mosquito species targeted.
If the inappropriate malaria mosquito (for example, Anopheles coluzzii in the Mali study site) is removed from an environment. The more hazardous Anopheles gambiae will quickly take its place, posing a serious threat to human health.