The insect that changed Nepal’s history

since 1900, who has most significantly changed the flow of events? Many people would point to influential political actors like Chandra Shumshere or King Mahendra, even Prachanda.

My answer: the Anopheles minimus mosquito.

Although mountains loom large on Nepal’s horizon, much of the country’s history has been shaped by a lowland disease: malaria. One visitor to Nepal in the 1920s (somewhat dramatically) called malaria ‘a name which hums an undertone of death throughout the chronicles of Nepal’.

Malaria has long plagued the Tarai, but also, places like Pokhara in the hills. Just as malaria shaped Nepal’s past, its almost complete removal in the 1960s and 1970s has shaped Nepal’s present, launching vast demographic, environmental, and political changes that are still playing out.

Anopheles minimus was a central actor in these stories. It carried the country’s most dangerous malaria and its susceptibility to chemical spraying hastened the decline of the disease. Had this little mosquito possessed different habits, Nepal’s history would have unfolded very differently: malaria would have killed fewer people, and its removal would not have been so quick and complete.

Many people think of malaria as a Tarai disease that originates in dirty, stagnant water during the monsoon. In fact, Nepal’s malaria was several different diseases, came mostly from clean water, declined during the height of the monsoon, plagued the hills as well as the Tarai, and affected various parts of the Tarai differently. ‘The whole of the Tarai,’ one scholar has noted, ‘was not equally malarious.’

Malaria is not just one disease, but ‘a kaleidoscope of different infections’. Nepal had two types of malaria: vivax (‘the great debilitator’) and falciparum (‘the deadly killer’). Falciparum often caused anemia, and if untreated, brought epilepsy, blindness, brain misfunctions—and even coma and death.

It was most likely falciparum that Father Giuseppe de Rovato described in 1868: ‘At the foot of the hills, the country is called ‘Teriani’; and there the air is very unwholesome from the middle of March to the middle of November: and people in their passage catch a disorder called in the language of that country Aul, which is a putrid fever, and of which the generality of people, who are attacked with it, die in a few days.’

“Mosquitoes are justifiably unloved, but unjustifiably understudied by historians.” John McNeill Historian

Two mosquito species carried malaria in Nepal: Anopheles fluviatilis and Anopheles minimus. Both preferred to breed near clean water in Nepal’s two main malarial zones: hill valleys, and the forest belt on either side of the Chure Range.

‘No elevation short of 3,000 to 4,000 feet above the sea,’ British resident Brian Hodgson noted in the mid nineteenth century, ‘suffices to rid the atmosphere of the low Himalaya from malaria.’

This was mostly vivax, not falciparum, but it still had big impact: hill communities generally placed their settlements above 3-4,000 ft and only partially cultivated the fertile land of valley floors.

Another surprise: not all of the Tarai had bad malaria. Indeed, by the 1960s, the southern belt along the Indian border between Nepalganj and Biratnagar had very little malaria. This shocked government entomologists who searched for malaria-carrying mosquitos but found neither An. minimus nor An. fluviatilis.

It was the forest belt that harboured the country’s most dangerous malaria. Straddling the Chure hills, this strip included Inner Tarai valleys like Chitwan, Sindhuli and the undisturbed northern parts of the Tarai.

Here, the main carrier of the most lethal form of malaria (falciparum) was the Anopheles minimus. Because it was very small and bit softly and mostly at night, it often went undetected, making it particularly dangerous. Shirtless men sitting in the evening air for an hour or two could get 25-30 bites.

But the minimus was easily wiped out by insecticides like DDT. This was because, as a Nepali entomologist once told me, minimus acted ‘like a king’. It had refined tastes. Unlike other mosquitos, it preferred not animal but human blood, and after feasting sought out comfortable accommodations — resting inside houses, not outside. DDT was easiest to spray on walls inside houses, exactly where minimus liked to hang out.

During the 1950s and 1960s, the World Health Organisation and United States led a global campaign to wipe out malaria in scores of countries around the world, including Nepal. Many of these efforts fell far short of the goal, mostly because the mosquito carriers proved hard to eliminate or they developed resistance to insecticides and medicines. 

In Nepal, however, despite manpower shortages and a daunting geography, eliminating the Anopheles minimus proved relatively easy. Although never reaching complete eradication, Nepal’s program proved far more successful than most.

The near complete removal of malaria in a country whose history had been moulded by the disease brought dramatic changes: vast movements of people from the hill ridges to valley floors and to the Tarai, as well as movement north from the plains. There was large-scale deforestation and habitat loss, and tumultuous social and political reconfigurations. Almost everyone was affected, but especially the Tharu, one of Nepal’s largest ethnic groups, who lived primarily in or near the forest belt.

These changes would probably never have come, at least not in exactly the same form, had the Anopheles minimus possessed slightly different habits. Indeed, if it had not liked resting exactly where DDT was sprayed, malaria might still be a dominant force in Nepali life.

This little non-human actor deserves a big place in Nepal’s history books alongside the much better known political movers and shakers. 

Tom Robertson is an environmental historian and Executive Director of Fulbright Nepal. A longer version of this article will appear in this month’s Journal of American History.

Read also:

Learning from Malaria, Bjørn Lomborg

The return of the parasites, Hemlata Rai