Anopheles leucosphyrus, an important vector of human malaria in Sarawak, Borneo, was shown to be infected with Plasmodium inui in Malaya by the inoculation of sporozoites into an uninfected rhesus monkey. The mosquito was caught while biting a man, thus demonstrating that it would be possible for a monkey infection to be transmitted to man in nature.
Although mosquitos of the Anopheles umbrosus group have long been recognized as important vectors of human malaria in Malaya, there have been doubts about the origin of some of the malaria infections found, especially in A. umbrosus and A. letifer. Investigations have accordingly been carried out in the Malayan swamp-forest, in conjunction with laboratory studies, into the nature of malaria infections in wild-caught mosquitos, the biting behaviour of anophelines and the presence of malaria infection in man and animals. The authors conclude from the results reported in this paper that A. umbrosus is a vector of mouse deer malaria and rarely, if ever, transmits primate malaria; that A. letifer transmits both human and mouse deer malaria; and that A. baezai and A. roperi are probably vectors of mouse deer malaria.
The mosquito Anopheles balabacensis balabacensis has been identified as a natural vector of at least two species of simian malaria in the monsoon forests of the northern Malay States. This mosquito is also a serious vector of human malaria from Viet Nam to northern Malaya. This is the first report of a mosquito which transmits both human and simian malaria in nature.
During the past decade outbreaks of a severe haemorrhagic disease caused by dengue viruses of multiple types have been reported in the Philippines, Thailand, Malaysia, Viet-Nam and eastern India. In many of these outbreaks chikungunya virus, a group A arbovirus, was simultaneously the cause of similar but probably milder disease. Both these viruses appear to be able to be able to produce classical dengue fever in some individuals and disease with haemorrhagic manifestations in others. Because of the growing public health importance and the progressive spread of this disease a unified review of its clinical and epidemiological features has been needed. This paper presents the history and salient clinical features of mosquito-borne haemorrhagic fever and summarizes recent epidemiological studies and current diagnostic and control methods.