Paragonimiasis: a Japanese perspective Fukumi Nakamura-Uchiyama, MD a , Hiroshi Mukae, MD b , Yukifumi Nawa, MD, PhD a, * a Department of Parasitology, Miyazaki Medical College, 5200 Kiyotake, Miyazaki 889-1692, Japan b Second Department of Internal Medicine, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan Paragonimiasis is a subacute to chronic inflamma- tory disease of the lung caused by infection with Paragonimus species lung flukes. Among over 40 species of genus Paragonimus described until now, Paragonimus westermani, Paragonimus miyazakii, Paragonimus mexicanus, Paragonimus skrjabini, and few other species are known to cause human infection [1]. Other majorities were found in car- nivorous/omnivorous animals. Infection in humans occurs when the second intermediate hosts, fresh- water crabs or crayfishes that are contaminated with metacercariae (infective larvae) of Paragonimus spp, are ingested. It has been estimated that 20 million people are infected worldwide, over 90% in Asia infected with P westermani [2]. The disease in humans is common in limited areas of Asia [3], some parts of Latin America [4 – 7], and Africa [8 – 10], where eating uncooked or undercooked freshwater crabs/crayfishes is common practice. As an unusual route of human infection, consumption of uncooked meat of wild boars, which serve as the paratenic host (see Life Cycle section below), has been reported from Japan [11]; this way of infection appears to be increasing [12]. Paragonimiasis is a typical food-borne parasitic zoonosis closely related to unique eating habits in particular areas of the world. Recently, however, paragonimiasis patients have been seen in many parts of the world because of an increase in the number of overseas travelers, popularization of ethnic dishes, and the expansion of worldwide trading of foods. Pa- tients found in United States were mostly emigrants/ refugees from Asia or Latin America [13 – 15]. One patient recently reported from France appeared to be infected while visiting Japan [16]. Thus, clinicians engaged in chest medicine should always be aware of the possibility of paragonimiasis. This review focuses mainly on clinical symptoms of paragonimiasis in association with the life cycle of the parasite. In addition, current trends of diagnosis and treatment for paragonimiasis are reviewed briefly. Life cycle of Paragonimus A schematic diagram of the life cycle of Parago- nimus spp is shown in Fig. 1. Adult worms residing in the lungs of the definitive hosts lay eggs, which are voided from the host either in sputum or in feces. After development in fresh water, eggs release mira- cidiae that invade the first intermediate host, fresh- water snails. In the snail hosts, miracidiae then develop through sporocysts and rediae stages into cercariae, which emerge from the snail and invade crustaceans (crabs or crayfish), the second intermedi- ate hosts, where they become metacercariae (infective larvae). Infection to the definitive hosts, including humans, occurs by ingesting raw or undercooked freshwater crabs or crayfishes contaminated with the metacercariae [17]. When freshwater crabs/cray- fishes contaminated with the metacercariae are ingested by unsuitable mammalian hosts such as wild pigs and boars, juvenile worms excysted from meta- cercariae migrate into the muscles of those hosts, where they remain immature for long years. These 0272-5231/02/$ – see front matter D 2002, Elsevier Science (USA). All rights reserved. PII:S0272-5231(01)00006-5 * Corresponding author. E-mail address: paras@post1.miyazaki-med.ac.jp (Y. Nawa). Clin Chest Med 23 (2002) 409 – 420