Observations on Echinostoma revolutum and Echinostoma trivolvis in single and concurrent infections in domestic chicks

Inmnarionai Journalfor Pararitdogy. Vol. 27. No ‘Cl 1997 Austrahan Society for Parasitology. Published

Pergamon

I I. pp. 1319-1322. 1997 by Elsevier Science Lid Printed in Great Brmm 002&7519/97 $17.00+0.00

PII: SOO20-7519(97)00100-8

RESEARCH

NOTE

Observations on Echinostoma revolutum and Echinostoma trivolvis in Single and Concurrent Infections in Domestic Chicks BERNARD

FRIED,*

THOMAS

J. MUELLER

and BETSY A. FRAZER

Department of Biology, Lafayette College, Easton, PA 18042, U.S.A. (Received 5 May 1997; accepted 21 July 1997)

Abstract-Fried B., Mueller T. J. & Frazer B. A. 1997. Observations on EcLinosrome reuolurum and Echinostoma triuoluis in single and concurrent infections in domestic chicks. International Journalfor Parasitology 27: 1319-1322. Studies were done to determine specific differences between adults of Echinostoma reuolutum and Echinostoma triuolvis grown singly and concurrently in domestic chicks. Worm recovery at l& 21 days post-infection (p.i.) of E. reuolufum and E. frivofuis in singly infected chicks was 21 and 17%, respectively; in concurrent infections, worm recovery for E. reuolutum and E. triuoluis was 21 and 16%, respectively. The body area of E. triuofuis was 1.5-2.0 times greater than that of E. reuolufum at 10-21 days p.i. Most body organ measurements of the suckers and gonads at 10, 14 and 21 days p.i. were significantly greater in E. triuoluis compared with those of E. reuolutum. The mean dry weight/worm at 14 days p.i. was 2.5 mg for E. triuoluis and 1.0 mg for E. reuolutum. In single infections, E. reuolutum was found only in the rectum and E. triuoluis mainly in the lower ileum, and in concurrent infections worms of both species were found in the rectum. Contrary to a previous report that stated that the body size of adult worms is not a reliable taxonomic indicator between E. reuolutum and E. frivoluis, the findings reported here show that body area and organ size can be used to distinguish these closely related species. (0 1997 Australian Society for Parasitology. Published by Elsevier Science Ltd.

Key words: Echinostoma reoolutum: Echinostoma trioolvis; Trematoda; infections;

concurrent

infections;

domestic

The Echinostoma revolutum complex consists of a number of 37-collar-spined species of Echinostoma that are now considered separate based on morphological, physiological and biochemical differences (Christensen et al.. 1990). The following species are included in this complex: a European-Asian species referred to as E. revofutum that uses various species of lymnaeid snails as first intermediate hosts and only avian species as definitive hosts (see Kanev, 1994 for details); a North American species referred to as E. trivolvis that uses the planorbid snail Helisoma trivolvis as first and second intermediate hosts and both avian and mammalian species as definitive hosts (see Kanev et a/., 1995). An additional species has recently *To whom 250-5463; lafayette.edu

systematics;

infectivity;

single

chicks.

correspondence should be addressed. Tel: 610Fax: 610-250-6557; e-mail: friedb@lafvax.

1319

that uses Lymhosts and birds as definitive hosts (Sorensen et al., 1997). This new species is considered as a North American form of E. revolutum and Sorensen et al. (1997), using morphological characteristics, were not able to distinguish the North American species of E. rerohtum from that of the European-Asian form. Because of interest in echinostome species in the E. revolutum complex, Humphries et al. (1997) compared growth and development of E. revolutum from L. elodes with E. trivolvis from H. trivolvis, and reported differences in growth and infectivity of these species in laboratory-infected domestic chicks. The purpose of this study was to extend the observations of Humphries et al. (1997) to include certain comparative morphological observations of adults of these species grown singly and concurrently in domestic chicks. been described

from North

America

naeaelodesas first and second intermediate

B. Fried et al.

1320

In single infections, l-day-old White Leghorn chicks were each exposed to 50 metacercarial cysts of E. trivolvis or E. revolutum as described in Fried & Butler (1978). Chicks were fed ad libitum on a standard poultry chow. Sixteen other chicks were each exposed concurrently to 50 cysts of E. trivolvis and 50 cysts of E. revolutum. In addition, six chicks were each exposed concurrently to 25 cysts of E. trivolvis and 25 cysts of E. revolutum to match the total number of metacercarial cysts fed singly to each chick. All chicks were necropsied at 10, 14, or 21 days post-infection (p.i.). Acquisition of metacercarial cysts, methods of infection, necropsy and worm recovery were described in Humphries et al. (1997). At necropsy, the location of each worm in the intestinal tract was recorded. In a single trial the dry weights of five worms from each species at 14days p.i. were determined after drying the worms for 24 h at 60°C. Weights were calculated on a per worm basis. Most worms were fixed in hot (85590°C) alcoholformalin-acetic acid (AFA), stained in Gower’s carmine, dehydrated in an alcohol series, cleared in xylene and mounted in Permount. Body length, maximal width measurements and organ measurements were made on 10 worms of each species on days 10, 14, and 21 p.i. as described in Ursone & Fried (1995). Student’s t-test was used to compare differences in worm body area and organ measurements, with P
current infections are summarised in Table 1. A photomicrograph of live lCday-old E. trivolvis and E. revolutum is shown in Fig. 1. Body and organ measurements of 10 worms each recovered at 10, 14 and 21 days p.i. are summarised in Table 2, which shows that the body and organ measurements of E. trivolvis were significantly greater than those of E. revolutum except for the diameters of the oral sucker and acetabulum. The ratio of body length to width of E. trivolvis was significantly greater than that of E. revolutum. However, the ratio of the diameter of the acetabulum to oral sucker was the same for both species. The body area of E. trivolvis was 1.7 times greater than that of E. revolutum. Similar trends were noted for 14-day-old and lo-day-old worms. The body area of E. trivolvis at 14days was 1.5 times greater than that of E. revolutum and the ratio of the diameter of acetabulum to oral sucker of E. revolutum was greater than that of E. trivolvis. All measurements of E. trivolvis at 21 days p.i. were significantly greater than those of E. revolutum, and the body area of E. trivolvis was 1.9 times greater than that of E. revolutum. Moreover, the ratio of body length to width of E. revolutum was greater than that of E. trivolvis and the ratio of the diameter of acetabulum to oral sucker was greater in E. revolutum than E. trivolvis. Dry weights on a per worm basis were calculated only at 14 days pi. and showed that the mean weight for E. trivolvis was 2.5mg compared with that of 1.O mg for E. revolutum. In the single infections at l&21 days p.i. all E. revolutum adults were in the rectum, while 14% of the E. trivolvis adults were in the rectum and 86% in the

of worm recovery of single and concurrent infections of Echinostoma trivohis (E.t.) in the domestic chick

No. of chicks used Exposed Infected

No. of cysts per chick E. r.

E.t.

Single E.r. infection 6 14 2

4 14

8

6

1

50 50 50

Single E.I. infection 12 2

10 1

3 12

3"

50 50 50

revolutum

No. of days post-infection 10 14 21

(Er.)

and Echinostoma

Average no. (and percentage) of worms recovered E.?.

E.1.

3.5 (7) 13.3 (27) 2.0(4)

10

6.8 (14)

14 21

10.1 (20) 4.0 (8)

Concurrent infections 1 5 1

11” 1” 5"

1”

“Number of chicks infected concurrently.

50 50 50 25 25

50 50 50 25 25

10 14 21 14 21

3.7(7) 10.5 (21) 25.0(50) 6.8 (27) 7.0(28)

14.0 (28) 6.3 (13) 15.0(30) 2.2 (9) 7.0(28)

Research

Fig.

1.

Table

A phon omit -ograph

2-Mean

Measurements” Body length Body width Body areab Oral sucker diameter Acetabulum diameter Ovary length Ovary width Anterior testis length Anterior testis width Posterior testis length Posterior testis width

(dark

field)

k SE. (in mm) of body

showing

live lCday-old (ER).

and organ

10 days p.i. E. revolutum E. trivolvis 3.56kO.14 0.55 +0.03 1.98kO.15 0.14*0.01 0.43 kO.01 0.09~0.01 0.08+0.01 0.23 +0.02 0.16kO.01 0.24*0.01 0.16rtO.02

“All measurements were significantly greater diameter of the oral sucker and acetabulum; 21 days p.i. hBody area reported in mm’.

note

4.8310.15 0.69kO.04 3.34k0.26 0.12+0.003 0.35 ,O.Ol 0.20+0.02 0.16&0.01 0.26 kO.02 0.20 & 0.02 0.33 +0.02 0.20+0.02

1321

Echinostoma

measurements

trivolvis

of 10 adult worms

14 days pi. E. revolutum E. trivolvis 5.21 kO.11 0.70+0.02 3.73kO.18 0.15 *0.002 0.51+0.01 0.17+0.01 0.15*0.01 0.34+0.02 0.21+0.01 0.38+0.02 0.20*0.01

7.01+0.22 0.77+0.03 5.48 + 0.35 0.16+0.01 0.49 + 0.02 0.25 f 0.01 0.20*0.01 0.40 f 0.02 0.25+0.01 0.45 * 0.02 0.26*0.01

(ET) and

at various

times post-infection

21 days pi. E. revolutum E. trivolvis 6.3lkO.17 0.76*0.03 4.86 * 0.32 0.17+0.01 0.58 + 0.02 0.17+0.01 0.19*0.01 0.36kO.02 0.17+0.01 0.39kO.02 0.18&0.01

8.41 kO.29 1.11*0.04 9.39+0.63 0.43 + 0.02 0.73 f 0.05 0.26+0.01 0.36*0.01 0.46+0.04 0.29 * 0.02 0.52 k 0.04 0.32+0.04

-

(P~0.05) in E. trivolvis than E. revolutum at 10 and 14days pi., except for the all measurements were significantly greater in E. trivolvis than E. reoolutum at

1322

B. Fried et al.

lower ileum. However, in similarly aged worms from concurrent infections, 19% of the E. trivolvis adults were in the rectum and 81% in the lower ileum. All the E. revolutum were in the rectum in the concurrent infections. Infectivity and worm recovery data were lower in this study than those reported for E. revolutum and E. trivolvis by Humphries et al. (1997). Studies on infectivity in chicks using echinostome metacercariae (reviewed in Huffman & Fried, 1990) showed variable results probably related to numerous factors, including species or strain of echinostome, age of metacercarial cysts, age and strain of chicks, and feeding protocols of the chicks. Hence, the significance of infectivity and worm recovery data in studies on echinostomes in chicks must be viewed with caution. In the present comparative study on these two related 37collar-spined echinostome species, worm recoveries of both species in either single or concurrent infections ranged from 1.5 to 20%. Further studies are needed to determine the factors that maximize worm establishment of avian species of Echinostoma in domestic chicks. The infected sites within the host differ between the two species. E. revolutum was always found in the rectum, whereas the main site of E. trivolvis was the lower ileum. In concurrent infections both E. trivolvis and E. revolutum were found in the rectum. The fact that these species can occupy the same habitat in concurrent infections suggests that studies on interspecies mating should be attempted, as done by Nollen (1997) for E. trivolvis and E. caproni in hamsters. Body area differs significantly between these two species, with E. trivolvis being 1.5-2.0 times larger than E. revolutum at l&21 days p.i. This research confirms a previous observation by Humphries et al. (1997) on significant differences in body area of these species at 10 and 14days p.i. and also reports significant differences in length and width of major body organs and of body and sucker length-width ratios often used by trematode systematists in comparative

studies. Sorensen et al. (1997) noted that body size of adult worms is not a reliable taxonomic indicator between E. revolutum and E. trivolvis. The findings reported here and those of Humphries et al. (1997) show that body area and organ size can be used to distinguish these two related species, at least in experimentally infected domestic chicks. Dry weights were different, with E. trivolvis being 2.5 times heavier than E. revolutum at 14 days p.i. Dry weights have been used infrequently in comparative studies on digeneans, but can provide valuable information on differences in closely related echinostome species. REFERENCES

Christensen N. M., Fried B. & Kanev I. 1990. Taxonomy of 37-collar spined Echinostoma (Trematoda: Echinostomatidae) in studies on the population regulation in experimental rodent hosts. Angewandte Parasitologie 31: 127-130.

Fried B. & Butler M. S. 1978. Infectivity, excystation, and development on the chick chorioallantois of the metacercaria of Echinostoma revolutum (Trematoda). Journal of Parasitology

64 175-177.

Huffman J. E. & Fried B. 1990. Echinostoma and echinostomiasis. Advances in Parasitology 29: 215-269. Humphries J. E., Reddy A. & Fried B. 1997. Infectivity and growth of Echinostoma reoolutum (Froelich, 1802) in the domestic chick. International Journalfor Parasitology 27: 129-130.

Kanev I. 1994. Life-cycle, delimitation and redescription of Echinostoma reoolutam (Froelich, 1802) (Trematoda: Echinostomatidae). Systematic Parasitology 28: 125-144. Kanev I., Fried B., Dimitrov V. & Radev V. 1995. Redescription of Echinostoma trivoluis (Cort, 1914) with a discussion on its identity. Systematic Parasitology 32: 61-70. Nollen P. M. 1997. Mating behavior of Echinostoma caproni and E. trivolvis in concurrent infections in hamsters. International

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Parasitology

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Sorensen R. E., Kanev I.. Fried B. & Minchella D. J. 1997. The occurrence and identification of Echinostoma revolufum from North nal of Parasitology

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Ursone R. L. & Fried B. 1995. Light and scanning electron microscopy of Echinosroma caproni (Trematoda) during maturation in ICR mice. Parasitology Research 81: 45-51.