Excerpted from the thesis of Truong Hoang Phuong

                                                                DISSERTATION ABSTRACT

  1. Summary introduction


– Major: Veterinary Parasitology and Microbiology         Code: 964. 01. 04

– Supervisors:

      Ass. Prof. Nguyen Huu Hung                                Dr. Nguyen Duc Tan

– Educational Institution: National Institute of Veterinary Research

  1. Dissertation abstract contents

2.1 The purposes and objectives of the study:

The aims of this study were to identify species, distribution, biological characteristics, and influential factors on the prevalence of liver fluke (Opisthorchis sp.) infection in ducks in Binh Dinh, Phu Yen and Khanh Hoa provinces.  Also, the study recommended the appropriate treatment and control methods.

The objectives of this research are ducks infected with small liver flukes Opisthorchis sp. in Binh Dinh, Phu Yen and Khanh Hoa provinces; small liver flukes Opisthorchis parageminus; intermediate hosts fresh water snails and fresh water fish.

2.2. Research methods

In this study, the morphotyping as well as genotyping methods were used for identifying species of Opisthorchis sp. Post mortem and tissue digestion methods were applied to determine the prevalence of duck infection. Experimental infection method was used to determine the live cycle of Opisthorchis parageminus and pathological signs of infected ducks. This study also tested some different kinds of medicine and chemical substances for treatment and control small liver flukes in ducks. This leads to the recommendation for treatment and control methods.

2.3 Main results and conclusion

– The study was conducted in three Central regional provinces of Binh Dinh, Phu Yen and Khanh Hoa. The result showed that, only ducks in Binh Dinh infected with liver fluke Opisthorchis sp. with the prevalence of 19.31%. Moreover, the prevalence of susceptible fresh water fish infected with metacercariae was 24%.

– Base on morphological characteristics analysis and partial sequence analysis of ITS2 and COX1 genes, the study revealed that, small liver fluke Opisthorchis sp. infected in ducks in Binh Dinh is Opisthorchis parageminus. The Opisthorchis parageminus is the most close in genetic relationship to Opisthorchis viverrini.

– Also, fresh water snail Bithynia siamensis and fresh water fish Systomus binotatus were identified as first and second intermediate hosts of small liver flukes, respectively.

– The life cycle of small liver flukes, including different stages: eggs forming miracidium in the  environment within 12 – 20 days; cercaria forming and leaving out of snails within 60 days; cercaria then penetrate into Systomus binotatus fish and develop into metacercariae within 8 – 20 days. Metacercariae then developed into mature flukes in duck within 60 – 65 days.

– Ducks infected with small liver flukes showing some typical pathological signs including reduce appetite, lose weight, reduce egg production, intestinal obstruction, yellow or green faces, accumulation of fluid in the abdominal cavity, enlarged gallbladder, hepatitis, hemorrhage or abdominal adhesive peritonitis,…

– To control small liver flukes, its eggs should be killed using iodine 2% or chloramine B 1.25%, spraying 1 liter/10-12m2 floor of duck pent. These chemical substances were able to kill 66.66% to 88.14% Opisthochis eggs.

– Fenbendazole (16mg/kg body weight) and praziquantel (10mg/kg body weight) should be frequently used, results to 85.81% to 90.47% clearance. For egg-laying ducks, deworming should be taken twice a year.

Scientific significances of the study

This is a logical research which studied on small liver flukes (Opisthochis parageminus) in ducks. The duck infection status was determined and factors that influence the distribution of the parasite were identified. Identifying species of small liver flukes was carried out, using morphology and sequencing the ITS2 and COI gens.

This is the first research in Vietnam as well as in the world that studied on the life cycle of small liver flukes in ducks. The study described the life cycle, identified intermediate hosts, determined clinical signs of infected ducks, recommended treatment and control methods.

Practical significances of the study

The result of this study is the scientific basic that could be applied to control small liver flukes in ducks, in order to minimize negative effect and develop sustainable duck production.


This is the first research that successfully studied on the life cycle of the small live flukes Opisthorchis parageminus. Identifying the first intermediate host is fresh water snail Bithynia siamensis and the second intermediate host is fresh water fish Systomus binotatus.

Described clinical signs, gross lesions and microscopic lesions of the disease caused by small liver flukes in ducks, providing a scientific basis for the rapid diagnosis to timely treat the disease.


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