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A new tome traces the outsized effects the mosquito has had on human history

The Mosquito: A Human History of Our Deadliest Predator

Timothy C. Winegard
Dutton
2019
496 pp.
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Timothy Winegard’s entertaining new book, The Mosquito, chronicles the impact of mosquito-borne disease, principally malaria, throughout history. The majority of the book is dedicated to the mosquito’s impact on the rise and fall of empires.

Alexander the Great, we learn, pulled back from his Indian campaign when his armies were decimated by malaria. (He himself may have later died from malaria.) And the Pontine Marshes, which protected Rome from the attentions of Hannibal at the end of the second Punic War, later contributed to major annual summer epidemics of malaria. During this period, Romans prayed to the fever goddess Febris for relief, and Rome was described as a death trap with a fever-puffing subterranean dragon.

The historical journey continues with Genghis Khan, as Winegard documents the impact of malaria during the conqueror’s Eastern European campaign. A wet spring in 1241 increased malaria and decimated Khan’s army in the Hungarian plains. Wineguard speculates that Khan may have died through a “weakening of his immune system [due to] chronic malarial infection,” but the evidence base for this is minimal. Malaria did, however,
compromise Khan’s grandson Kublai Khan’s campaign in southern China and Vietnam and may have contributed to the eventual fall of the Khmer civilization.

As we move to the late 1500s and early 1600s, the narrative shifts to the slave trade and the role mosquitoes played in stopping Europeans from colonizing central Africa. Here, another historical figure, Sir Francis Drake—the English sea captain and slave trader—is added to the list of malaria’s notable victims in 1596.

Whereas Aedes mosquitoes, yellow fever viruses, and malaria parasites were transferred from West Africa to the Americas during this period, the Anopheles mosquitoes  transmitting malaria were not, although Winegard implies otherwise. There is also no evidence that the Aedes that arrived in the Americas “thrived…in its superiority to domestic species.” The invaders simply assimilated into the local mosquito fauna. New and Old World Anopheles are distinct to this day and, indeed, in the few accidental introductions of Anopheles gambiae that have occurred outside Africa—for example, in Brazil in the 1930s—the invasive mosquitoes were rapidly recognized and eradicated (1).

DDT and chloroquine reduced mortality from malaria in the second world war and subsequently became the bedrock of the World Health Organization’s malaria eradication efforts of the 1960s. Here, Winegard writes that “DDT [operates] by quickly scrambling the proteins and plasma of sodium ion channels and neurotransmitters,” a garbled and inaccurate representation of its true mode of action. (DDT directly binds the voltage-gated sodium channels in the insect’s nerves, forcing the channels to remain open and the nerves to fire repeatedly.)

Although eradication was possible on the geographical fringes of malaria transmission, it soon became apparent that DDT and chloroquine alone would not be enough to stamp out the disease in the African heartlands (2). The intensity of malaria transmission in many parts of the continent where the climate is optimal for the parasites’ survival and reproduction means that the vast majority of an often hard-to-reach rural population had to be protected with indoor residual spraying of DDT at huge cost.Symptomatic individuals also had to be rapidly treated with chloroquine if there was to be any chance of breaking the transmission cycle. The funding and political will required to take on this task were formidable. When resistance to both the insecticide and the drug started to appear, it became a near impossible task.

Readers might surmise that efforts to control malaria then stopped for decades, which is in part true for Africa—but not for the rest of the world. Winegard glosses over decades of rapidly evolving and effective malaria and arbovirus control, picking up his narrative when West Nile virus invaded New York in 1999. During this period, new insecticides replaced DDT, and indoor residual spraying of insecticide was joined by pyrethroid-impregnated bednets, which have saved many millions of lives globally.

The book concludes with an overview of new technologies under development to reduce malaria transmission, including CRISPR-Cas genome modification of the mosquito and deployment of a malaria vaccine. Winegard speculates that we might use these new interventions to eliminate
the mosquito altogether, but the focus of these projects is to reduce the ability of the mosquito to transmit the parasite, not to eradicate it.

Readers of this book will no doubt enjoy Winegard’s rapid journey through many of humanity’s major population movements, campaigns, and wars, but I, for one, remain skeptical of the direct involvement of mosquito-borne disease in the death of many of the familiar figures presented. For those wanting an authoritative work on mosquitoes and mosquito control, I would recommend A. N. Clements’s The Biology of Mosquitoes or Mike Service’s Medical Entomology for Students, respectively.

REFERENCES AND NOTES
1. G. F. Killeen et al., Lancet Infect. Dis. 10, 618 (2002).
2. J. A. Nájera et al., PLOS Med. 8, e1000412 (2011).

About the author

The reviewer is at the Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK.