Evaluation of human hydatid disease before and after surgery and chemotherapy by demonstration of hydatid antigens and antibodies in serum.

This study was performed to differentiate serologically between patients with hydatid disease which is active, and which has been successfully cured. A total of 18 cases was included. Pre-treatment serum samples were collected before surgery or chemotherapy. Post-treatment serum samples were collected at various intervals (3 days, 7 days, 1 month, 6 months, 1 year and 2 years) after surgery or chemotherapy. These sera were tested for the presence of circulating hydatid antigen (CAg) by bacterial co-agglutination (Co-A) and counter-current immunoelectrophoresis (CIEP) tests, and for circulating hydatid antibodies (CAb) by indirect haemagglutination assay (IHA). Ten and eight sera, respectively, were positive out of 11 pre-operative and pre-chemotherapeutic sera tested for CAg by the Co-A and CIEP tests. Post-operative sera collected from these cases did not show any CAg by the CIEP test. However, CAg was detected by Co-A in three and four serum samples collected on the third and seventh day, respectively, after surgical removal of the cyst. However, the CAg levels in these post-operative sera showed a gradual decline by the seventh day and were completely absent in the serum specimens collected 1 month after surgery and 6 months after chemotherapy. All the post-operative serum samples except two, collected 2 years after surgical removal of the cyst, in seven cases of old hydatid disease, were negative for CAg by both the CIEP and Co-A tests. Unlike the CAg profile, no marked differences were noted between the CAb profile of the pre- and post-treatment sera, as shown by the IHA test. Even 1 year after surgery or chemotherapy, two sera showed a marginal decrease in their CAb titre. CAb at varying titres was still detectable in all seven serum samples from old cases of hydatid disease, even 2 years after surgical removal of the cyst. This study shows the value of serial pre- and post-operative or chemotherapy estimation of CAg by Co-A and CIEP as an index of cure or of continuing hydatid infection.