Mosquitoes May Have Killed up to 54 Billion Humans Over 200 Millennia

How about this for perspective:

Mosquitoes are our apex predator, the deadliest hunter of human beings on the planet. A swarming army of 100 trillion or more mosquitoes patrol nearly every inch of the globe, killing about 700,000 people annually. Researchers suggest that mosquitoes may have killed nearly half of the 108 billion humans who have ever lived across our 200,000-year or more existence.

mosquitoThe author of the piece is Timothy C. Winegard, author of the forthcoming book The Mosquito: A Human History of Our Deadliest Predator.

Each year, about 400,000 people die of malaria alone, with another 300,000 dying from other mosquito-borne diseases.

It is worth noting that the failure to eliminate malaria globally is primarily a function of state weakness.

Is malaria responsible for underdevelopment in Africa?

According to a paper by Depetris-Chauvin and Weil, the answer is no.

Here is the abstract:

We examine the effect of malaria on economic development in Africa over the very long run. Using data on the prevalence of the mutation that causes sickle cell disease, we measure the impact of malaria on mortality in Africa prior to the period in which formal data were collected. Our estimate is that in the more afflicted regions, malaria lowered the probability of surviving to adulthood by about ten percentage points, which is twice the current burden of the disease. The reduction in malaria mortality has been roughly equal to the reduction in other causes of mortality. We then ask whether the estimated burden of malaria had an effect on economic development in the period before European contact. Using data at the ethnic group level, we find little evidence of a negative relationship between malaria burden and population density or other measures of development.\

And here’s a summary of the main finding:

With estimates of the extent of malaria mortality in hand, we then turn to look at the impact of the disease on economic development. We present regressions of a number of measures of development within Africa on a malaria burden measure that we create based on sickle cell prevalence. Of particular note, we apply our analysis to a data set measured at the level of ethnic groups as an alternative to more common country-level analyses. We present simple OLS results, as well as results in which we instrument for malaria burden, using an index of climactic suitability for malaria transmission. The result of this statistical exercise is that we find no evidence of malaria burden negatively affecting historical economic development.

Read the whole paper here.

And here, here, and here are related posts on mosquitoes and malaria.

Can African states eliminate malaria?

Southern Africa has an ambitious plan to eliminate malaria by 2030. According to the FT:

Under the Elimination8 plan, the idea is to end malaria by 2020 in four so-called frontline states where transmission levels are already low — below 10 per 1,000. These are Botswana, Namibia, South Africa and Swaziland. Four higher-transmission, “second line” countries — Angola, Mozambique, Zambia and Zimbabwe, where transmission rates can climb as high as 400 per thousand — have until 2030 to get the job done.

Kenya presents a less sanguine but still somewhat positive story. The country reported 8.3 million cases of malaria in 2018, a decline of 12% from 2012. And out of these cases, 16,000 fatalities were reported. Contrast this with China which in 2017 reported a grand total of 2,672 malaria cases, all of which were due to infections while abroad. China’s population is 1.4 billion. Kenya’s population is 49 million. 40 years ago China reported more than 24 million malaria cases annually.

So how did China do it?

Screen Shot 2018-04-24 at 9.08.41 PM.pngThrough a combination of vector control, human behavioral change (including use of treated bed nets), and treatment. All three approaches are important. For instance, while the malaria mortality rate of 0.09% in Kenya is not super high (thanks to treatment), it still means that each year millions of work hours are lost due to illness. It is also a significant drain on the healthcare system. In addition, while treated bed nets have been shown to save lots of lives, we should still work towards complete elimination of the disease.

And that will require an aggressive form of vector control, something that is glaringly missing from most malaria programs on the Continent.

Interestingly, the international community used to take vector control seriously, which resulted in some significant results (see map):

 In 1955, the UN committed to ending the scourge of malaria. It was optimistic because it thought there were effective tools. The pesticide DDT had been found to kill the mosquitoes that were spreading the disease in US army camps in the Pacific during the second world war. Widespread use of DDT and the drug chloroquine drove malaria out of many countries in the Americas, Europe and parts of Asia.

But it all fell apart. There was no real attempt to tackle malaria in sub-Saharan Africa because it was thought to be too difficult. Elsewhere, elimination fell foul of the problem that has bedevilled all malaria control efforts: resistance of the malaria parasite to drugs and of the mosquitoes to pesticides. Then in 1962, Rachel Carson’s blockbuster Silent Spring was published, alerting the world to the environmental devastation wreaked by DDT. The UN’s malaria eradication plan was officially scrapped in 1969.

The over-correction arising from Carson’s paradigm-shifting findings meant that much of the world was willing to sit on their hands as more than 400,000 people died each year of malaria. The WHO only dabbles in vector control through treated bed nets. Sadly, resistance to its choice of insecticides stood at 81% in 2016.

That translates to over 200 million people infected each year, over 400,000 of whom die.

Even Bill Gates agrees that complete eradication of malaria is the most sustainable solution:

“Eradication is the only sustainable solution to malaria,” Bill Gates said on the release of the report his foundation produced with the UN last September. “The alternative would be endless investment in the development of new drugs and insecticides just to stay one step ahead of resistance. The world can’t afford that approach.”

Is anyone out there investing in research on environmentally-safe insecticides?

 

 

How to Eliminate Malaria

Sri Lanka is the latest country to be declared malaria free by the WHO.

How did they do it?

According to the New York Times:

In 2000, outside the rebel-controlled areas in the northeast, malaria cases began dropping as the government, with donor help, deployed a mix of indoor spraying, bed nets, rapid diagnostic kits and medicines that combined artemisinin, an effective treatment, with other drugs.

The government also screened blood samples drawn — for any reason — in public clinics and hospitals for malaria infection, and officials established a nationwide electronic case-reporting system.malariaeradication

In war-torn areas, the disease retreated more slowly, although the Tigers often cooperated with malaria-control teams because their villages and fighters also suffered.

Nonetheless, in a population of 20 million, it took years to get rid of the last few hundred annual cases. Most were soldiers and itinerant laborers, often from India, who worked in remote slash-and-burn farming areas and in logging and gem-mining camps.

Someone tell African policymakers that bed nets and behavior change are not enough.

Every other region of the world appears to be willing and able to combine vector (mosquito) control with other strategies of containing malaria with success (and enthusiastic donor support). But for some reason mosquito control is still lagging in Africa, even in otherwise strong and stable states. In some instances this has been due to environmental concerns while in others it has been due to the misplaced priorities of public health officials, donors, development agencies, and academic researchers.

The result:

About 3.2 billion people – nearly half of the world’s population – are at risk of malaria. In 2015, there were roughly 214 million malaria cases and an estimated 438 000 malaria deaths. Increased prevention and control measures have led to a 60% reduction in malaria mortality rates globally since 2000. Sub-Saharan Africa continues to carry a disproportionately high share of the global malaria burden. In 2015, the region was home to 89% of malaria cases and 91% of malaria deaths. 

214 million malaria cases amount to lots and lots of lost productivity. Also, losing one Miami every year in deaths is simply unacceptable.

More on this here. 

What if we killed all the mosquitoes?

It appears that a malaria vaccine will not be available for some time. According to Reuters,

“The world’s first potential malaria vaccine proved only 30 percent effective in African babies in a crucial trial, calling into question whether it can be a useful weapon in the fight against the deadly disease.”

Reading this reminded me of my own illness with malaria at the end of summer.

Back in September I contracted malaria while on a short trip back home in Kenya. Due to malaria’s incubation period I only started feeling sick after I was back in Palo Alto. My illness set off a total freakout at the Stanford Hospital. No less than four medical students, besides the crowd from the infectious disease unit at the hospital, passed by my hospital bed to ask the EXACT same questions. And of course they wanted to keep me overnight. They had an IV drip already installed in my arm. I tried my best to tell the doctor that I didn’t think I needed to be hospitalized to no avail.

The nurse who took my vitals put a mask on her face the moment I told her that I had malaria. I had to restrain myself from reminding her that malaria is not airborne.

A week later the Santa Clara County infectious disease office called me to get my details and ask me if I was feeling better. The government wanted to know where and how I got malaria. The grad student in me was fascinated by the level of state capacity in Santa Clara.

A few weeks before my Kenya visit I was in Fort Worth, TX. This was at the height of the West Nile virus outbreak that killed dozens of people. At the time health authorities in the Dallas-Fort Worth area were in the middle of spraying the area to kill all the vectors (mosquitoes). My girlfriend reminded me of the fact that as recent as when her parents were growing up in Grand Prairie, TX much of the American South still had to be sprayed regularly (with DDT) to get rid of disease-bearing mosquitoes.

The reason I recounted these stories is to illustrate the fact that there is an alternative to pouring tons on money on vaccine research or bed nets. Yes, these may result in cool scientific discoveries or provide excellent opportunities for social scientists to get published on their RCT findings. But the reality is that millions of people are still dying.

Instead of asking those living in high disease burden environments to change their behaviors and sleep under mosquito nets, how about we get rid of the mosquitoes??

If it worked in the American South, and many other places, why can’t it work in Africa?

I would very much love to live in a place free of malaria. Because of my age and health, my malaria infection at the end of summer was a mere nuisance – mild aches and fatigue. But for millions of children and post-natal mothers across much of tropical Africa malaria is a fatal disease.

But is DDT the answer? Haven’t we been made to internalize the evils of DDT?

It turns out that what we know about DDT might not be the whole truth. As Gourevitch argues, the environmental impact of DDT might have been overblown by the environmentalists.

Writes Gourevitch:

“Around the same time, the U.S. government launched an ambitious DDT-centered malaria eradication project which by the early ’60s had virtually eliminated malaria from Southern Europe, the Caribbean, and parts of East and South Asia. (In India, for example, annual deaths went from 800,000 to zero.) At the time, DDT was thought to be such an effective and useful substance that in 1948, Muller received a Nobel Prize in medicine. “To only a few chemicals does man owe as great a debt as to DDT,” declared the National Academy of Sciences in a report in 1970. “In little more than two decades, DDT has prevented 500 million human deaths, due to malaria.””

Adding that:

“But over the years, mainstream scientific opinion has absolved DDT of many of its supposed sins. Indeed, the Stockholm Convention partially backfired because it brought to light a slew of studies and literature reviews which contradicted the conventional wisdom on DDT. Like nearly any chemical, DDT is harmful in high enough doses. But when it comes to the kinds of uses once permitted in the United States and abroad, there’s simply no solid scientific evidence that exposure to DDT causes cancer or is otherwise harmful to human beings……

Not a single study linking DDT exposure to human toxicity has ever been replicated.”

But even assuming that the effects were as bad as they were claimed to be, shouldn’t we as humans be able to decide on the relative importance of human lives versus bald eagles?

How many children should be allowed to die so that bird watchers can better enjoy their Sunday afternoons?

the cost of malaria, and the continent’s disease burden

Academics have already established that the economic costs of malaria and Africa’s general disease burden are not trivial. Think of lots of man-hours wasted due to illness and government expenditures on medication, time and money that could be used to build roads and what not.

To illustrate the point, not anyone is immune from Malaria. Drogba, the illustrious Ivorian forward, got malaria and had to take a few days off from his duties at the London club, Chelsea.

“He has this virus and, obviously, he lost power and training.”

“He lost his condition. He’s had treatment and now he’s OK. He’ll come back immediately in the best condition.”

sunday roundup

Easterly goes to church in Ghana.

This post has pictures on some interesting way to use bed nets…. It seems like the only way we shall ever eliminate malaria on the Continent is by getting rid of all the mosquitoes. Other tropical places have done it. Why can’t it be done on the Continent, at least in the urban areas??

And lastly, I found this video clip totally cool.

Happy Sunday!

JAMBO!

“the town seemed to exist only for sickness and death”

Time has this story about the “most malarial town on earth,” Apac in Uganda. The pictures tell it all, life in Apac appears to be singularly harsh.

The story also reports that malaria steals away 1.3 percentage points off Africa’s annual growth rate. It is encouraging, though, to know that the fight to eradicate malaria is not yet lost because “the logistics of such a plan are less complex than they seem, because while malaria affects half the world’s countries, just seven — the Democratic Republic of Congo, Ethiopia, Kenya, Nigeria, southern Sudan, Tanzania and Uganda — account for two-thirds of all cases.”

As is the case with most failures on the Continent, failure to eradicate malaria can be attributed to bad leadership and state incapacity. Time reports:

What do these failures have in common? Bad government.

To paraphrase Achebe, the trouble with Africa is STILL simply and squarely a failure of leadership. There is nothing basically wrong with the African character. There is nothing wrong with the African land or climate or water or air or anything else. The African problem is the unwillingness or inability of its leaders to rise to the responsibility, to the challenge of personal example which are the hallmarks of true leadership . . . . in the meantime, millions on the Continent continue to die of treatable illnesses while tens of millions more live like it’s still 1600.

low grade anti-malarials found in a number of african countries

This might be why the last time I was down with malaria – back in the summer of 2007 in Uganda – none of the medication I got from a clinic in the capital Kampala helped me out. I had to go back home in Nairobi, Kenya before I got medication that completely cleared the plasmodium parasites off my system.

This finding means that someone is profiting from cheap anti-malarial drugs while at the same time increasing the disease’s resistance against existing medication. Now the next step should be to quantify the number of deaths that can be directly linked to these low quality drugs, round up those guilty and have them pay for their crime. People should never be allowed to play games with the lives of others.

malaria is still around, you know

Researchers have discovered a trend in the habits of mosquitoes. The little insects are feeding on human blood earlier than they used to. This means that more and more people get bitten earlier in the evening before they get to sleep under bed nets – which in turn translates into higher malaria infection rates. Bed nets lower infection rates by a whole 40%. Now researchers are urging people to use mosquito repellents. Personally, I don’t think this will fly. I for one do not like the “tourist smell” of repellents (I still don’t get how tourists stand themselves smelling like that!). I would advocate for a more aggressive approach to eliminating mosquitoes. DDT is bad, I know. But can’t we find other means of doing this? Plus malaria deaths, lost man hours because of disease burden and expenditures on anti-malaria medication may outweigh the cost of eliminating mosquitoes – thereby making the latter the more rational option.

Meanwhile, the WHO in a 2003 report says that malaria is still alive and well and continues to kill 2000 African children every day. That translates to 0.73 million children every year. I need not even add the figures for people over the age of 5.

some good and bad news

The good news first. According to UNICEF, the global under five mortality dropped by about 28% between 1990 and 2008. In other words, 10,000 less children are dying daily worldwide than was the case in 1990.

But that is as good as it gets. The sorry fact is that millions of children under the age of five still die every year from treatable illnesses – malaria, pneumonia and diarrhea being the top child-killers. Last year alone saw the loss of 8.8 million children under the age of five. India, the DRC and Nigeria were the worst hit – together reporting 40% of all under-five deaths. Africa and Asia, combined, reported 93% of global under five deaths.