Immunodiagnosis of Taenia saginata in cattle using hydrophobic antigens from T. hydatigena metacestode cyst fluid

Hydrophobic fractions isolated from cyst fluid of Taenia hydatigena metacestodes, obtained from naturally infected goats from Tanzania, were used it an indirect ELISA and in immunoblot (Western or dot blot) procedures. The use of the most hydrophobic fractions of the cyst fluid proved to result in a better diagnostic discrimination in ELISA than the more hydrophilic fractions. Best diagnostic ratio between responses from T. saginata infected and non-infected cattle was achieved when using horse-radish peroxidase-labelled sheep antibovine IgG 1 as the conjugate. When the hydrophobic fractions of T. hydatigena cyst fluid were employed as antigen in ELISA, no cross-reaction took place with sera from cattle infected with Fasciola hepatica, Ostertagia ostertagi, Cooperia oncophora, Dictyocaulus viviparus, Sarcocystis cruzi or a mixture of D. viviparus, Trichostrongylus axei and Eimeria. Using the Western blot technique, specific low molecular weight components (M r 10-18 kDa) of the hydrophobic fractions of the cyst fluid were reactive with sera from 14 of the 21 calves infected with T. saginata for 60 days. Also, hydrophobic fractions of T. hydatigena cyst fluid were dotted onto strips of filter membranes and reacted specifically with sera from the 21 calves infected with T. saginata. This technique resulted in the highest sensitivity, detecting 17 of the 21 calves infected with T. saginata. Calves harbouring as few as 16, 26, 43, 53 and 74 cysts could be detected. Thirteen calves harbouring between 74 and 2,545 cysts were all detected. However, 4 calves harbouring 2, 22, 52 and 66 cysts, respectively, were not detected. The potential of using a dot blot technique in large scale investigations in the tropics is present. However, before accepting any of the three tests in the tropical environment, a broader spectrum of helminth infections should be evaluated for their eventual cross-reactivity.