Ticks and mites are second only to mosquitos in importance as vectors of human infectious diseases. This paper reviews recorded information on zoonotic infections based primarily on studies conducted in Malaysia since 1948, but with some attempt at a global perspective. The tropical rain forest ecosystem is reviewed. The paper summarizes some 35 years of studies on the involvement of ticks and mites in human health and welfare in Malaysia. This is also an attempt to introduce the field to those who may be interested, in view of our limited knowledge relative to the importance of these vectors, and their potential of transmitting newly emerging diseases that may be introduced to the country. Tropical rain forest is a stable environment. Though Acari-borne zoonotic diseases evolved in the forest, infections are manifested through the alterations mostly by man-made activities. The parasitic Acari have preferred environmental conditions and biotopes that determine their distribution in nature, particularly within the tropical rain forest and consequently the environmentally altered areas that are the source of greatest risk for diseases. Acarines also vary in their vector potential. This article reviews the biology and ecology of all those species known to have zoonotic importance. Zoonosis in this paper refers not only to diseases that are transmitted from animals to man, but also those parasites of animals that cause dermatitis and other skin conditions in humans. This paper documents all Acari-borne zoonoses and distinguishes between those caused by viruses and those caused by rickettsiae. Emphasis is placed on Langat Virus, a tick-borne virus discovered and documented in Malaysia, with notes on the life-history and ecology of the vector
Ixodes granulatus from which Langat virus was first isolated. Another tick-borne virus, the Lanjan virus was also isolated from Dermacentor “auratus” at the IMR. The paper mentions three other viral infections that have been isolated in Malaysia from ticks, vertebrate reservoirs or both. The tick-borne rickettsial infection, boutonneuse fever is reviewed. The distribution is given for Q-fever, a disease caused by a pathogenic agent that is rickettsia-like. Information to clarify the status of Dermacentor ticks, human tick bites, and the presence of questing ticks on vegetation are also given. Tick-caused human otoacariasis in Malaysia and elsewhere is discussed, with notes on terminology. Based on a report by Induharan et al., tick paralysis is believed to occur in Malaysia. The potential importance and introduction of Lyme disease to Malaysia is discussed. The epidemiology and ecology of scrub typhus and its vectors is reviewed, including the colourful history of its study at the Institute for Medical Research (IMR). Scabies is now recognized as a zoonosis and the condition is described. Sarcoptid mites are suspected to represent more than one species. Scrub-itch and dermatitis caused by chigger mites, macronyssid mites and astigmatid mites are discussed. The importance of birds and bats in the dispersal of parasites is discussed. As examples of classical Acari-borne zoonoses, a viral disease from India and a rickettsial disease from America are briefly described. The elucidations of the natural history of these tick-borne diseases are described as epics of biomedical history. Though the essence of this paper is on environmental effects of zoonoses caused by ticks and mites, the environment in relation to human welfare and diseases is also discussed.