Correlation of antigen specific IgG and IgG(T) responses with Anoplocephala perfoliata infection intensity in the horse.

There is increasing interest in the application of serological methods to macro-parasite infections to indicate infection intensity, which in turn is related to pathogenicity. Colic is the single most important cause of mortality in horses and there is evidence that a proportion of colic cases are associated with infection with the intestinal cestode Anoplocephala perfoliata. In order to develop better tools to investigate this association, the correlation between antigen-specific equine IgG and IgG(T) and infection intensity of A. perfoliata was investigated. Affinity purification of a 12/13 kDa protein doublet from crude excretory/secretory (E/S) products, and its use in enzyme linked immunosorbent assays (ELISA) is described. Its use in the immunodiagnosis of equine cestodosis and the correlation of anti-12/13 kDa IgG and IgG(T) with parasite burden is investigated using sera from 94 horses of known tapeworm infection intensity. The anti-12/ 13 kDa IgG and IgG(T) ELISAs gave correlation coefficients with infection intensity of 0.56 and 0.63 respectively. Linear regression analysis also indicated that anti-12/ 13 kDa IgG(T) was the best predictor of infection intensity. The decay of anti-12/13 kDa IgG(T) in horses following the elimination of A. perfoliata is demonstrated for four horses. Specificity of the anti-12/13 kDa IgG(T) ELISA is investigated with sera from 33 A. perfoliata negative horses with other helminth infections. Immunoblotting studies demonstrate no cross-reactivity between A. perfoliata 12/13 kDa antigen and the protein antigens of other helminths. It is concluded that assay of anti-12/13 kDa IgG(T) provides a useful tool for the assessment of A perfoliata infection intensity for clinical diagnosis and for epidemiological studies.