Diagnosis, treatment and prevention of Malaria

Diagnosis, treatment and prevention of Malaria

Introduction

Since at least the mid-Pleistocene, thousands of generations of humans have been parasitized by the plasmodia. It is certain that human malaria originated in the Old World, but there has been some debate about the timing of its appearance in the Western Hemisphere. Some have suggested that malaria was present in the New World long before European contact, but a strong case exists that the hemisphere was malaria-free until the end of the fifteenth century. Malaria could have reached the New World before 1492 only by traveling overland from northeast Asia or via seaborne introductions. The possibility that humans brought malaria into North America from Siberia can almost certainly be discounted; conditions in the far north for malaria transmission were and are unsuitable (Suh, et al. 2004). It is equally unlikely that the Vikings could have introduced malaria in the centuries before Columbus. They came from northern regions presumably free of malaria at the time and seem to have visited only coasts that were north of any possible anopheline mosquito populations. Similarly, voyagers from the central or eastern Pacific could not have transported the parasites because that region is free of anopheline vectors and thus of locally transmitted malaria. Voyagers reaching American coasts from eastern Asia could conceivably have introduced malaria, but this possibility too is remote (Williams, 2009).

Moreover, colonial records strongly indicate that malaria was unknown to indigenous Americans, and some areas that had supported large populations soon became dangerously malarious after European contact. The absence in aboriginal American populations of any blood-genetic polymorphisms associated with malaria is another kind of evidence that the Western Hemisphere remained free of the disease until contact. After 1492, malaria parasites must have been introduced many times from Europe and Africa (Conway, Roper, Oduola, et al. 1999). Native American anopheline vectors were at hand, and together with smallpox, measles, and other infectious diseases from the Old World, malaria soon began to contribute to the depopulation of the indigenous peoples. From its early, usually coastal, sites of introduction, malaria spread widely in North, Central, and South America, limited principally by altitude and latitude - factors controlling the distribution of vector mosquitoes. By the nineteenth century in North America, the disease was prevalent in much of the Mississippi Valley, even in the northernmost areas. Malaria transmission extended into the northeastern United States, well north in California, and far to the south in South America. By the eighteenth and nineteenth centuries, malaria had also become established in the American subtropics and tropics (Williams, 2009).

Malaria was of some importance in the centuries of Roman domination of Europe and the Mediterranean basin. However, it was probably much less destructive than it has been more recently, primarily because P. falciparum was absent or rare and the other species were less intensely transmitted. It is suggested that Anopheles atroparvus, basically a zoophilic species, was a poor vector for the human parasites (Conway, Roper, Oduola, et ...