One of Taiwan's many extraordinary features is that it is entirely malaria-free, and has been since 1965. In view of the fact that the disease is prevalent in much of the rest of Asia, even 8,000 feet up in the Himalayas, Taiwan's eradication of the disease remains a considerable achievement.
Mosquito, a new and masterly overview of what the authors call "mankind's deadliest foe," is both fascinating and disturbing. It's a tribute to a valiant struggle over 100 years (the mosquito was only confirmed as a source of disease in 1897), and a reminder of what still remains to be done.
Ten percent of the world's population suffers from malaria every year, and mosquitoes can also carry dengue fever, yellow fever, filariasis, West Nile fever -- as found in New York City in 1999 -- and a host of deadly encephalitis viruses. (Six cases of Japanese encephalitis, for example, have been confirmed in Taiwan this summer).
It was the West Nile fever outbreak that really brought the threat from mosquito-borne diseases home to modern, urban humankind. To this day, no one knows for certain how it arrived in New York from Africa. The authors accept, however, that the disease is now established in the US and is destined to spread across the country in the years to come.
Time and again in this book, it is the action of a single individual that proves decisive. The 1999 New York outbreak, for instance, had originally been thought to be closely related to St Louis fever, but the fact that horses as well as birds were dying of it led to the eventual correct diagnosis. A single medical researcher donned a spaceman-like suit, walked across a field to were a dead horse lay, cut open its skull and extracted its brain. West Nile fever was confirmed.
Taiwan features for other reasons than because of its continuing malaria-free status. One crucial discovery was first made in Kaohsiung in the 1870s. A Dr Patrick Manson was researching the filariasis worm that, in its most extreme and terrible manifestation, causes the gigantic swelling of the lower leg and, in males, the scrotum, in what is known as elephantiasis. Though autopsies were then a crime, Manson secretly opened the bodies of several people who had died of this disease and discovered thread-like female worms, the length of a human arm, tightly coiled round their male counterparts in the victim's lymph nodes. The grotesque swellings were caused by the immune system's reaction to these copulating worms.
But how did these worms get into people? Manson acquired a microscope, and with this looked at the blood of his gardener. It proved to be teeming with tiny filarial parasites, and the hapless gardener agreed to sleep in a screened room in the company of mosquitoes. Manson subsequently dissected these insects and found that they had ingested the parasites, and that these then grew inside their systems before being introduced into other humans through later bites.
Throughout the post-World War II period DDT was central to the fight against malaria. The disease had, for instance, been endemic in Rome for centuries, causing some former popes to flee the city. Control had been achieved by draining the marshes, but the Germans had destroyed these defenses as they retreated at the end of World War II, and the malarial mosquitoes were quick to return.
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