Abstract
The digenetic trematode Fasciola gigantica is a parasite of great agricultural and economic importance. Along with Fasciola hepatica, F. gigantica incurs huge economic losses to the agricultural sector. Because of unavailability of an effective and commercial vaccine, the earliest diagnosis of the disease is the only way to control the disease. The conventional coprological techniques are able to detect the disease only after the parasites get matured and starts releasing their eggs with the faeces of host, therefore prepatent infection remain undiagnosed. The alternative method is by serological tests that uses circulatory antigens. Despite high sensitivity, their reliability is quite low because of the common antigens shared between different helminth parasites. To overcome this, investigation was shifted to identify the copro-antigens which could be more sensitive and reliable. In the present study, we tried to identify some of the immunodominant proteins from the Excretory Secretory (ES) product of F. gigantica which can be further characterized and used for early detection of infection and also as drug and vaccine candidates. The ES products of F. gigantica were collected and used for raising the polyclonal antibody in rabbit. The polypeptide profile was generated as well as immunogenic polypeptides were identified. The Source of ES antigen was immunolocalized using confocal microscopy and dot blot assay was performed to diagnose field infection. The polypeptide profile of ES products revealed a total of 24 polypeptides out of which 12 immunogenic polypeptides were identified by western blotting. Confocal micrographs showed the immunolocalization of antigens in the intestinal caecae, vitalline glands, gonads as well as in the tegument of the worm. The dot blot assay confirmed the utility of ES products for the detection of field infection. Subsequently, cross reactivity was found negative with Gigantocotyle explanatum; an amphitome parasite of same habitat. However, the cross reactivity with other helminths needs to be worked out.
Highlights
The digenetic trematode Fasciola gigantica is a parasite of great agricultural and economic importance in India and in other tropic and sub tropic regions of the world [1,2]
Excretory secretory products were collected by incubating parasites in the phosphate buffered saline (PBS) pH 7.4 and the protein content of the collected ES products was estimated according to the method of Spector [45] using bovine serum albumin as standard
Hyperimmune sera against F. gigantica ES products were raised in male New Zealand white rabbit about 6 weeks old according to the method of Leenaars and Hendriksen [46] with some modifications
Summary
The digenetic trematode Fasciola gigantica is a parasite of great agricultural and economic importance in India and in other tropic and sub tropic regions of the world [1,2]. The most classical and widely used method to diagnose trematodiasis is the detection of parasite eggs in the host faeces. Considering the biology of the liver fluke, it is difficult to diagnose the disease during the early phase of infection since the newly excysted juveniles following metacercarial excystation penetrate through the intestinal wall and appear in the peritoneum. These worms migrate towards liver, penetrate the liver tissue and reach their microhabitat, the bile ducts, where they attain maturity in about 10–20 weeks post infection [6,7,8] and start producing eggs. The hurdles in the early diagnosis of infection have lead to the development of other more advanced or modified methods for the detection of parasitic infections [9]
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