Abstract
BackgroundThe gastrointestinal helminth, Teladorsagia circumcincta, is one of the major health risks and production-limiting diseases in small ruminant populations, particularly in temperate regions. With the increasing importance of disease management and recruited anthelmintic resistant types, accurate approaches are needed for the diagnosis of the infection in the host. Due to uncertain results using faecal examinations, the ELISA method was indicated for the detection of nematode antigenic materials. Despite some promising results, problems were described in terms of test specificity and cross-reactions. Therefore, this study aimed to evaluate the IgG response to worm somatic and excretory/secretory (ES) products using western blot analysis and an indirect ELISA for the detection of T. circumcincta infection in sheep.ResultsBased on the immuno-reactivity analysis, immunogenic fractions with molecular weights (MWs) of approximately 60, 75 and 100 kDa were detected in somatic content and two antigens of about 63 and 75 kDa in ES material. Accordingly, a specific product at 75 kDa had the strongest reaction and appeared as the most common antigenic protein. In ELISA, all the sera from the infected sheep revealed the OD rates above the calculated cut-off value with about two-fold greater average. Negative control samples were also specifically recognized with the mean OD rate of about 1/3 of the estimated cut-off value. The cross-reaction test, using rabbit anti-T. circumcincta IgG, did not show reactivity with the ES antigens of other prevalent nematodes including Haemonchus contortus, Protostrongylus rufescens and Marshallagia marshalli. In contrast, a strong positive reaction was observed with the somatic antigens of M. marshalli.ConclusionsThe results of this study indicated that the indirect ELISA method using the ES content enables distinguishing the T. circumcincta infected sheep with high specificity. Those antigenic ES peptides with 63 and particularly 75 kDa MWs should be further investigated due to the potential for serological diagnostic methods and immunoprotective targets in the host.
Highlights
The gastrointestinal helminth, Teladorsagia circumcincta, is one of the major health risks and production-limiting diseases in small ruminant populations, in temperate regions
In sheep infected with T. circumcincta, protective immunity was associated with the parasite-specific antibodies against adult worms [5] and the established larvae [6, 7]
The SDSPAGE analysis for somatic antigens revealed 15 protein fractions ranging in size from 20 to 245 kDa, with molecular weights (MWs) of 20, 25, 30, 38, 42, 45, 47, 60, 63, 65, 75, 80, 100, 180 and 245 kDa (Fig. 1)
Summary
The gastrointestinal helminth, Teladorsagia circumcincta, is one of the major health risks and production-limiting diseases in small ruminant populations, in temperate regions. Due to uncertain results using faecal examinations, the ELISA method was indicated for the detection of nematode antigenic materials. This study aimed to evaluate the IgG response to worm somatic and excretory/secretory (ES) products using western blot analysis and an indirect ELISA for the detection of T. circumcincta infection in sheep. Teladorsagia circumcincta is one of the most prevalent gastrointestinal nematodes (GIN) that infects sheep and goats worldwide. The detection of GIN has been traditionally depended on tracing the eggs in faecal samples by microscopy. In sheep infected with T. circumcincta, protective immunity was associated with the parasite-specific antibodies against adult worms [5] and the established larvae [6, 7]. The isotypes of antibodies play an important role in GIN resistance in sheep, including IgA, IgG1 and IgE [8]
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