Identification of Fasciola spp. based on ITS-2 reveals the Fasciola gigantica infection in buffaloes in Nanning city, South China

Abstract

Fasciolosis is harmful to ruminant husbandry worldwide. Given the superficial survey on Fasciolosis infection in Guangxi, the main buffalo breeding area in China, an in-depth investigation in the infection of buffaloes in Nanning, the capital of Guangxi Zhuang Autonomous Region, with Fasciola (Platyhelminthes: Trematoda: Digenea) species will provide a theoretical support for the control and prevention of Fasciolosis infection in buffaloes. Five water buffalo livers were collected from an abattoir in Nanning every 2 weeks from June 2018 to April 2019, and a total of 101 livers were obtained. All livers were then dissected to observe the liver lesions caused by the flukes. Afterwards, Fasciola spp. collected from Fasciolosis-infected livers were numbered and measured. Then, the livers infected with more than 3 flukes were marked, and 3 flukes were picked from each liver according to their morphological differences, such as body length (BL), body maximum width (BW) and length-width ratio (BL/BW). Moreover, these Fasciola spp. worms were selected for molecular biological analysis. The second internal transcribed spacer (ITS-2) of nuclear ribosomal DNA (rDNA) was amplified by polymerase chain reaction (PCR) and sequenced. Finally, sequential and phylogenetic analyses were also performed. The infection rate was 38.6 % according to anatomic examination, and the livers infected by Fasciola spp. were damaged seriously. The principal manifestations were the enlargement of the liver and protrusion of the bile ducts. In some cases, the bile duct wall became inflamed and rough, in which some sediment such as phosphate could be easily found. After dissection, 1243 Fasciola spp. flukes were collected from 39 out of 101 livers. The morphometric measurements obtained from the present study showed that the BL/BW ranged from 1.42–10.25. However, it might vary considerably among different geographical locations and could not be used as an accurate method for the identification of Fasciola spp.. Analysis of the ITS-2 sequences showed that 83 out of 87 flukes had 100 % homology with each other, and the other 4 flukes with 99.3 % homology possessed a nucleotide polymorphism. A unique position (271) was detected in flukes in Nanning isolates. Phylogenetic analysis indicated that all the flukes were Fasciola gigantica, and no Fasciola hepatica or the intermediate form was found in this study.