In February 2004 I was charged with a challenging mission to Sudan.
To travel up north in the Saharan desert, find malaria mosquitoes there, and bring them back alive to Austria. I know this sounds crazy, but that’s what medical entomologists like myself do. We needed those mosquitoes for research purposes.
The journey from Khartoum to Dongola took us the whole day. Through a landscape void of water. The further north we drove, the less vegetation I saw. When the air-conditioning in our battered project vehicle gave up, it became unbearable within minutes. Outside temperature soared over 45 degrees. Sweat evaporated from my skin before I could see it.
It took us (a team of four Sudanese and myself) two full days of intensive searching to find a small puddle of water that contained larvae of malaria mosquitoes (see picture below). The water, it turned out, was sourced from an underground broken waterpipe. All sources of water you see out there are man-made, pumped up from the Nile. Broken watertanks, leaking irrigation canals. It rains a mere 8 mm per year up there.
We were thrilled to find mosquitoes at last and frantically started collecting the larvae and pupae in our empty plastic water bottles. ‘Mission accomplished’, I thought to myself. Hundreds of larvae were transported back to the make-shift field station over the next two days.
But, no matter how hard we kept searching the surroundings of our ‘positive’ site, we didn’t find any more larvae. Nowhere. House after house we searched for adult mosquitoes, but I did not see even one during the two weeks I was there.
Early on the fourth morning, when the sun was not yet high enough to remove the coldness of the desert night, we stood there, watching over our only source of mosquitoes. The little waterpipe puddle. I then got a plan.
I asked all of the six of us to walk away from the puddle in different directions. And search, search, search. For water with larvae. For at least a 2 km radius from where we were. We’d all get back to our puddle after two hours.
When we all returned, nobody had found any traces of water, let alone mosquito larvae.
‘Right’, I said. ‘Let’s do some malaria control here. Where can I get a shovel?’ They all looked at me as if I had had too much sun the day before. But within minutes a shovel turned up. Then, in front of the team, it took me less than a minute to shovel enough sand into our puddle that it was hard to notice any water left in it.
It is only now that a discussion on the potential of larval control for malaria elimination is underway, that I realise that our puddle may have been the sole source for malaria in a 12,6 square kilometre area (radius of 2 km, squared, times pi).
A shovel was all that was needed. Would the next 12,6 km2 have looked the same? With one, two, or maybe three breeding sites that could easily be dealt with?
I don’t know. My mission was to bring mosquitoes back from Africa. Not to control malaria out there.
Now I wonder what would have happened if I had just stayed and continued shovelling sand into breeding sites with my Sudanese colleagues…