Scanning electron microscopic observations of Thelazia callipaeda from human

Abstract

Four females and a male nematode isolated from 2 patients who visited eye clinics in Seoul were identified as Thelazia callipaeda and their ultrastructures were observed by scanning electron microscopy (SEM). General features of the worms were slender and attenuated at both ends. Vaginal opening was located at 0.27 mm from the anterior end, and in front of the esophago-intestinal junction. In the body cuticle transverse striations varied characteristically through the body. The number of cuticular transverse striations was 400-650/mm at head portion, 250/mm at middle portion and 300-350/mm at tail portion. The SEM observation of the mouth part of the females showed 6 cord-like cuticular thickenings in hexagonal arrangement and an amphid was observed. A lateral line, a vaginal opening, a pair of phasmids, and an anus were identified in the body portion. A pair of papillae and 6 cord-like cuticular thickenings were on the mouth part of the male. It was difficult to observe structures at the tail of the male except wrinkle-like structures. Most of the larvae isolated from the uterus of a female worm were sheathed and thus cuticular striations were not seen. Others were un-sheathed and revealed cuticular striations. The oval membrane which encysted sheathed larvae was also observed. These are the 18th and 19th record of human thelaziasis in Korea as the literature are concerned.

First Thelazia callipaeda Infestation Report in a Dog in Taiwan

“…From the location of vulva and the number of cuticular transverse striations, these parasites were identified as six female and three male Thelazia callipaeda [4]. Female worms were ranging from 10 to 13 mm in length and 416 to 464 µm in width.…”

“…Since eye worm, Thelazia, was first described in 1676, various species of this genus have been reported from mammals, including humans [2][3][4]11] and domestic animals [8,10,[12][13][14]16]. Except the sporadic reports in United States [13] and Europe [6,11,12], Thelazia spp.…”

“…have mostly been reported in Asia [1,2,4,9,[14][15][16]. Of these species, only T. callipaeda and T. californiensis have been known to parasitize both humans [4] and dogs [13]. In addition, T. callipaeda also parasitizes cats [12].…”

“…Except the sporadic reports in United States [13] and Europe [6,11,12], Thelazia spp. have mostly been reported in Asia [1,2,4,9,[14][15][16]. Of these species, only T. callipaeda and T. californiensis have been known to parasitize both humans [4] and dogs [13].…”

“…3). T. callipaeda has been reported to parasitize humans in China [15], Indonesia [9], Japan [1], Korea [4,7], Thailand [17], Taiwan [2] and European countries [12]. It causes tearing, itching and occasionally blurred vision [2].…”