The oriental eyeworm (Thelazia callipaeda) is one of the parasitic nematodes which parasitize in the conjunctival sac of humans, dogs, and cats. Thelazia callipaeda is known for its unique vector, the lachryphagous flies of the genus Phortica. This nematode species was known to be distributed mainly in Asia, but human thelaziosis is caused by T. callipaeda has been confirmed in Europe and North America in the last decade. In Japan, this species has been reported from humans and domestic animals mainly in western Japan, and in recent years, reports T. callipaeda has been detected from raccoon and tanuki in the Kanto region (Tokyo, Gunma, Kanagawa) , and revealed the existence of three haplotypes (h9, h10, and h12) unique to Japan. In this study, we newly obtained T. callipaeda from 10 hosts, Japanese red fox (Tokyo), masked palm civet (Tokyo), Japanese badger (Tokyo), Japanese black bear (Nagano), raccoon (Ibaraki), tanuki (Ibaraki), Japanese marten (Ibaraki), dog (Tokyo, Iwate), cat (Tokyo) and human (Ehime, Hiroshima), and thus the cox1 gene of 41 individuals of T. callipaeda was sequenced and analyzed.
The cox1 gene sequences of the newly obtained T. callipaeda were distinguished into two haplotypes (h9 and h10), and mixed infections of the two haplotypes were observed in masked palm civets, Japanese black bear, Japanese red fox, Japanese marten and dogs. Of these, h9 was reported from humans (Okayama, Niigata), dogs (Tokyo), tanuki (Gunma) and raccoons (Tokyo, Kanagawa), h10 from humans (Kumamoto, Oita), dogs and cats (Tokyo) and raccoons (Gunma), and h12 from dogs and raccoons (Tokyo). No significant regional or host specificity was observed among the three strains of T. callipaeda strains in this study.