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Year : 2020  |  Volume : 10  |  Issue : 1  |  Page : 62-64  

Laboratory experience with the development of Fasciolopsis buski eggs

Department of Microbiology, ABVIMS and Dr. Ram Manohar Lohia Hospital, New Delhi, India

Date of Submission26-Sep-2019
Date of Acceptance22-Dec-2019
Date of Web Publication20-May-2020

Correspondence Address:
Arvind Achra
Department of Microbiology, ABVIMS and Dr. Ram Manohar Lohia Hospital, New Delhi - 110 001
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/tp.TP_61_19

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How to cite this article:
Achra A, Kansra S, Shulania A. Laboratory experience with the development of Fasciolopsis buski eggs. Trop Parasitol 2020;10:62-4

How to cite this URL:
Achra A, Kansra S, Shulania A. Laboratory experience with the development of Fasciolopsis buski eggs. Trop Parasitol [serial online] 2020 [cited 2022 Dec 5];10:62-4. Available from: https://www.tropicalparasitology.org/text.asp?2020/10/1/62/284614


Fasciolopsis buski is the largest trematode parasitizing the human small intestine. It was first described by a English surgeon George Busk in 1843 following autopsy of an Indian sailor in London and its developmental cycle was studied in detail by Nakagawa in 1922.[1],[2]

The monoecious adult worm inhabits the small intestine of humans and pigs. Infection in humans is acquired on ingestion of encysted infective metacercariae, which are found adhering to the surface of edible water plants such as water caltrop, water chestnuts, lotus, and watercress. Excystation of the ingested metacercariae is facilitated by gastric juices and release of a juvenile worm. This juvenile worm migrates and grows to maturity in the small intestine where it produces operculated eggs which are passed in feces. Eggs give rise to free-swimming miracidium which undergo further development in snails of the genus Segmentina and give rise to cercariae which encyst to form metacercariae and adhere to edible water plants.[3]

Clinical presentation of parasitism varies and depends on the number of infecting flukes in the small intestine. Patients with light infections are usually asymptomatic, whereas moderate and particularly heavy infections manifest as abdominal pain, diarrhea, nausea, vomiting, fever, and allergic reactions such as edema of the face, lower extremities, and ascites. Heavy infection can be fatal, as the flukes cause extensive intestinal inflammation, erosions, ulceration, hemorrhage, and abscess formation.[4]

F. buski is endemic to Bangladesh, China, India, Indonesia, the Lao People's Democratic Republic, Malaysia, Taiwan, Thailand, and Vietnam.[4]

In 2012, during a field survey, 45.8% of residents of a sector of a village in Bihar were found to be infected with F. buski with the highest worm burden in children 5–14 years of age.[5]

During this study, certain microscopic observations were made in the laboratory regarding the development of eggs which might be useful to young microbiologists.

   Observation 1 Top

It was observed that the freshly passed eggs were dark brown in color [Figure 1] and with inconspicuous operculum [Figure 1] arrow]. An inexperienced microbiologist might miss the diagnosis considering them as artifacts or some other parasites, as text books characteristically describe eggs being light brownish-yellow in color (bile stained).[3] On leaving the wet mount slide in moist chamber at room temperature, the eggs gradually turned to light brownish-yellow in color and a well-distinguished operculum was visible after 8–9 days [Figure 2]. Patients from whom these eggs were recovered were suffering from diarrhea due to high worm burden in their intestine. This finding suggests that eggs discharged by adult worm in the small intestine are stained by bile and are dark brown in color. Eggs gradually loose the bile stain during the intestinal transit and later in the external environment after discharge in the stool. Eggs in these patients could not loose bile stain due to decreased intestinal transit time and remained dark brown in color.
Figure 1: Freshly passed dark brown egg of Fasciolopsis buski

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Figure 2: Light brownish-yellow egg containing developing miracidium surrounded by yolk cells and a clearly distinguished operculum (black arrow). A viscous cushion of material at opercular end (white arrow)

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   Observation 2 Top

Fasciola hepatica eggs contain a viscous cushion of material in the shape of a concavo-convex lens at the opercular end of eggs, which helps in hatching of developing miracidium.[6] A structure similar to this viscous cushion was also observed in F. buski eggs on the 8th day [Figure 2], white arrow].

   Observation 3 Top

On further incubation at room temperature on the 11th day, partially open operculum and two transverse grooves were observed on the shell of developing eggs, signaling matured miracidium pushing the operculum to escape from the eggs [Figure 3]. Development and maturation of miracidium depends on the environmental conditions, particularly temperature and exposure to light stimulus.[6] Nakagawa observed that the development of miracidium in F. buski varies according to the season of the year and in summer it generally takes 2–3 weeks.[2] Under room temperature, in distilled water, miracidium developed in 12–15 days in F. hepatica eggs.[7]
Figure 3: Egg with partially open operculum and transverse grooves on shell surface

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   Observation 4 Top

On the 11th day, a disintegrating egg releasing yolk cells was observed, though it was not possible to visualize any miracidium [Figure 4]. Life span of the released F. hepatica miracidium was 10 h in the environment and might be similar for F. buski miracidium.[7]
Figure 4: Disintegrating egg releasing yolk cells

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   Observation 5 Top

At similar time frame, some eggs with detached operculum and 3–4 transverse grooves were observed which might be eggs from which miracidium had escaped [Figure 5]. Significance of these grooves is not known; these might have appeared on the eggshell due to pushing efforts of motile miracidium while escaping.
Figure 5: Egg having transverse grooves on shell surface and detached operculum

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From the above findings, it can be concluded that freshly passed eggs of F. buski may be dark brown in color and with inconspicuous operculum. These eggs can be kept in moist chamber to see further developmental stages, which helps in there identification.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Cook GC. George Busk, FRS (1807-1886): Surgeon, zoologist, parasitologist and palaeontologist. Trans R Soc Trop Med Hyg 1996;90:715-6.  Back to cited text no. 1
Nakagawa K. The development of Fasciolopsis buski Lankester. J Parasitol 1922;8:161-6.  Back to cited text no. 2
Chatterjee KD, editor. Phylum platyhelminthes. In: Parasitology: Protozoology and Helminthology. 13th ed., Vol. 1. Daryaganj: CBS Publishers; 2011. p. 188-90.  Back to cited text no. 3
Mas-Coma S, Bargues MD, Valero MA. Fascioliasis and other plant-borne trematode zoonoses. Int J Parasitol 2005;35:1255-78.  Back to cited text no. 4
Achra A, Prakash P, Shankar R. Fasciolopsiasis: Endemic focus of a neglected parasitic disease in Bihar. Indian J Med Microbiol 2015;33:364-8.  Back to cited text no. 5
[PUBMED]  [Full text]  
Rowan WB. The mode of hatching the egg of Fasciola hepatica. Exp Parasitol 1956;5:118-37.  Back to cited text no. 6
Hussein AN, Hassan IM, Khalifa RM. Development and hatching mechanism of Fasciola eggs, light and scanning electron microscopic studies. Saudi J Biol Sci 2010;17:247-51.  Back to cited text no. 7


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