Dealing with malaria in the last 60 years is seen by the author in the perspective of his own experience. His malaria work, which began in 1941, covered the study of the habits of the mosquitoes dwelling in the savanna country of Eastern Colombia and the effect on malaria transmission of the newly introduced DDT residual spraying. The success of the campaign he later directed in Sarawak and Brunei contributed to the launching by WHO of its global malaria eradication campaign. Further successful work in Uganda showed the possibility of effective control and even eradication in highland country but left unsolved the problem of how to interrupt transmission of holoendemic malaria in Africa. The author's work with WHO in the Middle East showed to what extent social and economic conditions could influence the course of a malaria campaign. This was also the experience in America, both in Colombia in the author's early work and later in Mexico during an evaluation of the national malaria programme. Development of insecticide resistance was also encountered in his career and the refractoriness of the European vectors was also observed in his work as a malariologist.
Following the discovery of mosquito transmission of malaria, the theory and practice of malaria control by general and selective removal of specific vector populations resulted particularly from Malcolm Watson's empirical work in peninsular Malaysia, first in the urban and peri-urban areas of Klang and Port Swettenham and subsequently in the rural rubber plantations, and from the work of N.H. Swellengrebel in nearby Indonesia on the taxonomy, ecology and control of anophelines. They developed the concept of species sanitation: the selective modification of the environment to render a particular anopheline of no importance as a vector in a particular situation. The lack of progress along these lines in India at that time is contrasted with that in south-east Asia. The extension of species sanitation and related concepts to other geographical areas and to other vector-borne disease situations is outlined.
Human dirofilariasis due to Dirofilaria (Nochtiella) repens is a common zoonotic infection in Sri Lanka. Todate 70 cases are on record, and they include 3 expatriates from Russia, England and Korea, who were undoubtedly infected in Sri Lanka. Around 30-60% of dogs are infected with D. repens in various parts of the country and the mosquito vectors are Aedes aegypti, Armigeres subalbatus, Mansonia uniformis and M. annulifera. Unlike in other countries of the old world infection is most common in children under the age of 9 years, the youngest being 4 months old and the scrotum, penis and perianal regions of male children appear to be frequent sites for the worms. Dirofilaria (Dirofilaria) immitis is not present in Sri Lanka though it is present in neighbouring countries like India, and Malaysia.
The documented history of malaria in parts of Asia goes back more than 2,000 years, during which the disease has been a major player on the socioeconomic stage in many nation states as they waxed and waned in power and prosperity. On a much shorter time scale, the last half century has seen in microcosm a history of large fluctuations in endemicity and impact of malaria across the spectrum of rice fields and rain forests, mountains and plains that reflect the vast ecological diversity inhabited by this majority aggregation of mankind. That period has seen some of the most dramatic changes in social and economic structure, in population size, density and mobility, and in political structure in history: all have played a part in the changing face of malaria in this extensive region of the world. While the majority of global malaria cases currently reside in Africa, greater numbers inhabited Asia earlier this century before malaria programs savored significant success, and now Asia harbors a global threat in the form of the epicenter of multidrug resistant Plasmodium falciparum which is gradually encompassing the tropical world. The latter reflects directly the vicissitudes of economic change over recent decades, particularly the mobility of populations in search of commerce, trade and personal fortunes, or caught in the misfortunes of physical conflicts. The period from the 1950s to the 1990s has witnessed near "eradication" followed by resurgence of malaria in Sri Lanka, control and resurgence in India, the influence of war and postwar instability on drug resistance in Cambodia, increase in severe and cerebral malaria in Myanmar during prolonged political turmoil, the essential disappearance of the disease from all but forested border areas of Thailand where it remains for the moment intractable, the basic elimination of vivax malaria from many provinces of central China. Both positive and negative experiences have lessons to teach in the debate between eradication and control as alternative strategies. China has for years held high the goal of "basic elimination", eradication by another name, in sensible semi-defiance of WHO dictates. The Chinese experience makes it clear that, given community organization, exhaustive attention to case detection, management and focus elimination, plus the political will at all levels of society, it is possible both to eliminate malaria from large areas of an expansive nation and to implement surveillance necessary to maintain something approaching eradication status in those areas. But China has not succeeded in the international border regions of the tropical south where unfettered population movement confounds the program. Thailand, Malaysia and to an extent Vietnam have also reached essential elimination in their rice field plains by vigorous vertical programs but fall short at their forested borders. Economics is central to the history of the rise and fall of nations, and to the history of disease in the people who constitute nations. The current love affair with free market economics as the main driving force for advance of national wealth puts severe limitations on the essential involvement of communities in malaria management. The task of malaria control or elimination needs to be clearly related to the basic macroeconomic process that preoccupies governments, not cloistered away in the health sector Historically malaria has had a severe, measurable, negative impact on the productivity of nations. Economic models need rehoning with political aplomb and integrating with technical and demographic strategies. Recent decades in Chinese malaria history carry some lessons that may be relevant in this context.