Entomologist Rebekah Kent's tale of death and life at the end of malaria season
One morning last April, I was riding shotgun in a truck in southern Zambia. Two Dixie cups of Anopheles mosquitoes in my hands and a dying boy in the back seat.
My colleagues and I had been in Mufwafwi village collecting mosquitoes as part of my dissertation research on the dynamics of malaria transmission. Complex and minute, anopheline mosquitoes are fascinating creatures. They also carry the malaria parasite that kills 1 million children each year in Africa alone.
As we were jovially piling into the truck to leave the village after a successful morning hunting "monzenyas," a man came running up to us with a limp child in his arms. A distraught woman followed close behind. Frederick looked about 3 years old and was completely comatose; only the whites of his eyes showed through partially cracked lids. None of us present was a physician, but the seriousness of his condition was clear. If he was going to have a chance of surviving, he needed a doctor as soon as possible. "Get in," we said. "Let's go."
April is the tail end of malaria season in southern Zambia. I'd seen many children sick with malaria in the Macha Mission Hospital, which is adjacent to the Johns Hopkins Malaria Research Institute's field station where my entomological research was based. Whether Frederick had malaria or some other infectious disease, we were clearly racing against time. Reaching the hospital is a big deal out there. We were a good 45-minute drive away, including 3 kilometers of bush paths before we would even get to the main road.
The mother held her sick child in the back seat. His breathing was raspy. I was terrified for him.
The truck bounced as quickly as safety permitted down eroded footpaths through tall grass. In my lap, I cradled the enemy. Topped by mesh held with rubber bands, each cup contained a dozen or so blood-laden anopheline mosquitoes that we had just collected. Some were from the very house in which little Frederick lived. With each bump the mosquitoes were jostled off their resting place on the side of the cup. Their threadlike hind legs arched up gracefully behind their bodies, and their fine, black and white dappled wings became gray blurs as they struggled to regain their footing. I tried to cushion them as much as possible.
Behind me, I heard Frederick alternate from uneven gasps to no sound at all. I gazed out the window and tried to concentrate on the pretty yellow and orange flowers that lined the roadside, on the bright sunlight that had just broken loose from an oppressive cloud cover. I caught a glimpse of the anguished father in the rearview mirror and clenched my jaw and swallowed hard to keep from crying. Please, let us get there on time.
I looked back down at the mosquitoes in my lap and marveled that these tiny, delicate creatures could be the menaces responsible for some of the world's deadliest scourges. Any one of these mosquitoes I held in my hands could be harboring thousands of wriggling, microscopic parasites.
When a mosquito takes an infectious blood meal, the parasite burrows into the mosquito's midgut, where it encysts itself for about a week. Seemingly inert inside this oocyst, the parasite is rapidly multiplying into tens of thousands of minute infectious stage parasites called sporozoites. If the oocyst survives attack from the mosquito's immune defenses, it ruptures and releases the sporozoites into the mosquito's body cavity, where they penetrate the salivary glands. From there, they are injected into a host upon the next blood feeding.
Mathematically, it is amazing that malaria transmission happens at all. Assuming the mosquito's very first blood meal was infected, she must live about 16 to 18 days in order to transmit the parasites. (Mosquitoes lucky enough to escape predation by birds, bats or raptorial insects may live about a month.) In the case of Anopheles arabiensis, the critical transmission time is the fourth or fifth blood meal. If this critical meal is taken on a cow, dog or chicken, the transmission cycle is broken. Likewise, if the first blood meal is taken from these animals or an uninfected person, the mosquito might not live long enough to become infectious. But, as Jeff Goldblum's character puts it in Jurassic Park, "Nature will find a way." And nature had found its way into the back seat of our 4x4 Toyota Hilux.
Please, please, let us get there on time. The road seemed endless. I no longer heard breathing behind me.
Finally, we pulled into Macha and stopped at the hospital's front door. Later, Dr. Phil Thuma, a pediatrician and the executive director of the Malaria Institute at Macha, told us that Frederick had cerebral malaria and a +4 malaria smear—a lethal level. "I'm not sure he's going to make it," Thuma told us.
Over the next few days, Frederick responded well to intravenous quinine. He recovered, even managing to avoid the deafness and blindness often caused by cerebral malaria. To my relief and joy, the eyes that were once white slits gazed back at me, suffusing me in their deep brown, captivating warmth.
My happiness over Frederick's recovery was tempered, however, by my knowledge of malaria's grim reality in Africa. On that same April day that Frederick recovered, 3,000 other African children weren't as lucky. The malaria parasite found its way to them, and they died.
We just didn't get to them in time.