Infectivity, Growth, Development, Excystation and Transplantation of Zygocotyle lunata (Trematoda) in the Chick

Abstract

Twenty-three chicks, each fed 10 cysts of Zygocotyle lunata in 3% NaHCO:~, were infected with a total of 85 worms (1 to 9/host), recovered only in the ceca 1 to 120 days postexposure. Body length increased slowly until the 5th day, and then rapidly until the 20th, followed by a slow increase to an average of 5 mm by the 120th day. Gonadal differentiation was evident by the 4th day and eggs appeared in the uterus by the 12th. Excystation occurred in the chick intestine, probably the lower ileum, but not in a surgically isolated chick cecum. Excysted metacercariae transplanted to the chick rectum migrated to the ceca. Zygocotyle lunata (Diesing, 1836) parasitizes the ceca of a variety of birds and mammals and has been maintained in sheep, rats, and ducks in the laboratory (Hall, 1927; Price, 1928; Willey, 1941). Adults can be surgically implanted into the cecum of a rat, and metacercariae placed there excyst (Bacha, 1960, 1962). Willey (1941) reported sexual maturation of Z. lunata within 41 to 44 days in ducks and 46 to 61 days in rats but Bacha (1960) found eggs in the uterus of a 17-day-old worm from the rat. This paper reports use of the domestic chick for the first time in studies on infectivity, growth, development, excystation, and transplantation of this trematode. MATERIALS AND METHODS Cercariae shed by naturally infected Helisomna trivolvis (Say) from Lake Warren, Bucks County, Pa., encysted on finger bowls containing pond water. Cysts 1 to 10 days old, well within the Received for publication 8 August 1969. * Supported by NIH Grant AI-06835. viability period (Willey, 1941), were scraped from bowls, and 10 pretreated in 3% NaHCO. for 30 to 60 min (Bacha, 1964) were fed in 1 to 3 ml of the bicarbonate to each of 23 1to 3-day-old domestic chicks which were necropsied 1 to 120 days later. Worms were pipetted into hot AFA (Fried, 1962), stained in Gower's (1939) carmine, cleared in terpineol, and mounted in Permount. Criteria of growth were length measurements of uncurled specimens (Fried, 1962). In excystation studies, the right cecum and a 2-inch strip of lower ileum were removed from Host A and 10 cysts placed into each organ. After the open ends were ligated with silk thread, the preparation was placed in a finger bowl containing 150 ml Tyrode's at 37 C and examined 4 hr later. Host B was prepared for surgery (Fried and Vonroth, 19618) and the right cecum was ligatured close to the ileocecal valve. After the cecal apex was severed, 10 cysts were implanted and the opening sutured; thie chick was necropsied 5 hr after surgery. Ten cysts were implanted into the rectum of Host C which was necropsied 5 hr later. Hosts D to J (Table II) were fed 10 to 50 cysts each and necropsied 0.5 to 15 hr postexposure. Four excysted metacercariae from Host I and 3 from Host F (Table II) were implanted into the recta of chicks K and L which were necropsied 3 days later. This content downloaded from 207.46.13.51 on Sun, 19 Jun 2016 07:40:07 UTC All use subject to http://about.jstor.org/terms FRIED-BIOLOGY OF ZYGOCOTYLE LUNATA (TREMATODA) IN THE CHICK 45