Haemaphysalis (H.) obesa Larrousse (Ixodoidea: Ixodidae) from Northeast India and Southeast Asia: Description of Immature Stages and Biological Observations

Abstract

The larva and nymph of Haemaphysalis (H.) obesa Larrousse, described here, are quite similar to those of the Javan H. (H.) hirsuta Hoogstraal, Trapido, and Kohls. The two species comprise a structurally specialized and biologically similar H. (H.) obesa group. H. (H.) obesa inhabits dense, humid lowland forests from West Bengal and Assam (India) in the west, through Thailand southwestward into Perlis (the northernmost state of Malaysia) and northeastward into the Republic of Vietnam. Known hosts of adults are medium and large-size forest-dwelling mammals, the monkey, bear, boar, deer, and domestic cattle, and probably the elephant. The single nymph recovered from a host was biting on the neck of a child. Adults, nymphs, and larvae were swept or picked from forest vegetation; they rest on the underside near the tips of leaves within 1.5 m from the ground. In laboratories in India and Thailand, the life cycle was completed in about 100-130 days. The obesa group presents several unique and numerous interesting areas for structural, functional, ecological, biological, and epidemiological research. Haemaphysalis (H.) obesa Larrousse has been known only from 12 adult specimens (Hoogstraal et al., 1966; Hoogstraal and Rack, 1967). From the present description of laboratory-reared immature stages, the close structural and phylogenetic relationship of this species and the Javan H. (H.) hirsuta Hoogstraal, Trapido, and Kohls is confirmed. Both species, which form the H. (H.) obesa group, inhabit dense, humid, lowland forests, where adults feed on large and medium-size mammals. Owing to unique adult setal arrangements circumspiracularly and on femur IV, and to unusual female external genital features (Hoogstraal et al., 1966), functional anatomy, behavior, and sexual processes of the H. (H.) obesa Received for publication 7 July 1970. * From Research Project MF12.524.009-3010, Bureau of Medicine and Surgery, Department of the Navy, Washington, D. C. The opinions and assertions contained herein are the private ones of the authors and are not to be construed as official or as reflecting the views of the Department of the Navy or of the naval service at large. The illustrations in this report were prepared under the auspices of Agreement 03-005-01 between the NIAID (NIH) and NAMRU3. t Medical Zoology Department, U. S. Naval Medical Research Unit Number Three, Cairo, Egypt, UAR. $ Medical Zoology Department, Niigata University School of Medicine, Niigata City, Japan. ? Virus Research Centre, Poona, India. The Virus Research Centre is maintained by the Indian Council of Medical Research. group should be exceptionally interesting to compare experimentally with other haemaphysalid groups. Larval and nymphal hosts in nature remain unknown. Ecological characteristics, known host preferences of adults, rapid life cycle, and ease of collecting and rearing these large ticks also serve to recommend this group as an outstanding candidate for rewarding biological and epidemiological studies in the field and laboratory. Materials and data for this report derive from a program funded by the Indian Council of Medical Research to Dr. T. Ramachandra Rao, Director (now retired) of the Virus Research Laboratory, Poona, for investigating the Himalayan area tick fauna of India (Dhanda and Bhat data); the German India Expedition, 1955-58 (Hoogstraal and Rack, 1967); a tick survey of Nakhon Ratchasima, Thailand, and laboratory studies in the Faculty of Tropical Medicine, University of Medical Sciences, Bangkok (Saito data); the Malayan Tick Survey, a collaborative study between the Institute for Medical Research (Kuala Lumpur), Zoology Department of the University of Maryland, and NAMRU-3 (Cairo) (Hoogstraal et al., 1969; Hoogstraal et al., in press); and continuing studies on the genus Haemaphysalis by the first author. Haemaphysalis (H.) obesa Larrousse Indo-Vietnam hirsute haemaphysalid (Figs. 1-15) Haemaphysalis obesa Larrousse, 1925, p. 302304, fig. 2, briefly described and illustrated $.