Mosquitoes adapting to high altitudes as climate warms

Mosquitoes adapting to high altitudes as climate warms

Two years ago, on a cold November morning, Dal Bahadur BC spotted a mosquito on the wall of a toilet in Gulmi district. The sighting is still vividly etched in his mind.

The lab assistant at Epidemiology and Disease Control Division (EDCD) at Department of Health Services had never expected to find the injurious parasite survive in such a harsh winter weather above 2,500 meters above the sea level.

“It did not move, but I cannot say whether it was dead. The mosquito was black in color and of big size. I could not figure out its exact species. When I enquired about the presence of such mosquitoes with few other locals, they did not look surprised. In fact, they were used to seeing them around since quite sometime,” said BC.

Similar was the response of Dependra Rawal, a vector control inspector at Dadeldhura District Health Office (DHO). He revealed of seeing mosquitoes and their larva at Amargadhi and Jogbuda VDC and also at Safhebagar municipality area of Achham district.

Both districts are located above 2,000 meters above the sea level, where until a few years ago the presence of these mosquitoes would have been unheard of.

The above mentioned cases are just a tip of the iceberg. There are many similar incidents where surveyors and locals have spotted mosquitoes and their habitation in the hilly region and even near the icy cold mountains.

These changes clearly indicate that mosquitoes climbing upward and adapting to higher climes. The gradual rise in temperature resulting from the impact of climate change has created suitable weather condition for the mosquitoes to survive at higher altitudes.

At a time when government authorities have been trying their best to end the spread of Malarai in the Tarai belt, experts are now worried about how to control this disease at higher altitudes.

“Regional temperature is increasing annually and so is the rain pattern. This change has helped these mosquitoes survive even in the hills and the mountains. Now, the biggest threat is the spread of dangerous diseases they carry and it will turn into epidemic if people are not cautious about it,” said Dr Babu Ram Marasini, director general at Epidemiology and Disease Control Division (EDCD). Research says it all Several researches conducted by Meghnath Dhimal, chief research officer at Nepal Health Research Council (NHRC), clearly explain the impact of climate change and the shifting pattern of mosquito habitation towards higher altitudes.

“There is no doubt about the presence of mosquitoes in the hilly region now and we are yet to expand our research to the mountains, but I have heard of their increasing population there as well,” said Dhimal. “As per the previous national survey reports, we believed that mosquitoes were found only up to 1,200 meters above the sea level.

Now, this standard has changed as these parasites have been spotted at 2,000 meters and above,” he added. A recent survey conducted by a group of researchers including Dhimal clearly suggests the presence of malaria vectors like Anopheles Fluviatils, Anopheles Annularis and Anopheles Maculatus up in the Eastern hilly districts. The research was conducted at the Eastern part of the country located above 2000 meters from sea level. The malaria vectors were recorded from 70 meters to 1,820 meters above the sea level. The vectors of chikungunya and dengue virus, Aedes aegypti and Aedes albopictus, the vector of lymphatic filariasis, Culex quinquefasciatus, and that of Japanese encephalitis, Culex tritaeniorhynchus, were found from 70 to 2000 meters. Larvae of Anopheles, Culex and Aedes species were recorded up to 2,310 meters. The research was conducted twice, first during the post-monsoon season starting from the end of September to October, and again at pre-monsoon seasons from April to May.

“Nearly a decade ago, finding these parasites at high altitudes was rare. They were confined to the Tarai belt only, but not anymore. Their altitudinal shift does worry us about the spread of vector born disease at a massive scale,” said Dhimal. However, Dhimal attributed the altitudinal shift of mosquitoes not only to the climate change but also to human migration. According to him, mosquitoes simply followed humans when they migrated up hills in search of better food and shelter. “First, it is important to understand that mosquitoes and their larvae were carried to the hilly region and above by humans. They might have hitched a ride on their luggage, food carried by humans or anything else people can hardly imagine. Then came the impact of rising temperature, the climatic condition that helped them to survive and multiply,” said Dhimal.

Temperature rise a factor

One can hardly deny the impact of global warming and the gradual rise in temperature. The melting of glaciers, erratic rainfall and weather conditions are some of the significant indicators of climate change across the globe. Intergovernmental Panel on Climate Change (IPCC) predicts an increase in world average temperature by 1.4-5.8 degree Celsius in 2100. Report suggests a rise of 0.89 degree Celsius of temperature from 1983 to 2012.

During the last 32 years, 1.8 degree Celsius temperature has increased in Nepal from 1975-2005. Experts at Department of Hydrology and Meteorology (DHM) suggest Nepal experiencing an annual temperature increase of 0.04 degree Celsius. Mean average temperature has been projected to have increased by 0.5-2.0 degree Celsius.


“Climate change is heating up the globe and the impact has been realized in Nepal as well. Compared to other regions, rise in the temperature of Himalayan region is significantly higher and so is the threat of disasters that may come,” said Sarju Baidya, deputy director general at DHM.

Source: Republica