PRELIMINARY EVALUATION OF A SIMPLE IN-VITRO TEST FOR THE DIAGNOSIS OFTYPE-C BOTULISM IN WILD BIRDS

An enzyme-linked immunosorbent assay (ELISA) was developed for the det ection of type C botulinum toxin (Clostridium botulinum) in wild birds . This simple, antigen-capture ELISA utilizes polystyrene immunosticks as the solid substrate, chicken antitoxin (IgY) as the coating antibo dy, rabbit antitoxin as the primary antibody, and peroxidase-labeled g oat-anti-rabbit as the secondary antibody. To evaluate the immunostick ELISA as a diagnostic test for avian botulism, known concentrations o f to;toxin were added to heparinized blood collected from healthy bird s and tested by both the ELISA and mouse bioassay. Also, blood samples from 236 bird carcasses submitted to the National Wildlife Health Cen ter (NWHC) for cause of death determinations were tested by both proce dures. Using less than or equal to 0.5 ml as the test volume for both procedures, the ELISA was less sensitive, detecting 0.25 ng/ml of toxi n compared to 0.12 ng/ml for the mouse bioassay. Using the same volume of test sample for diagnostic submissions (less than or equal to 0.5 ml), the ELISA was positive for 60% of the 149 clinically-diagnosed ca ses of botulism, whereas the mouse bioassay was positive for 79%. Howe ver, we demonstrated that with larger sample volumes (greater than or equal to 1.0 ml), the sensitivity of the ELISA may be equivalent or be tter than the mouse test due to the concentrating effect of the ELISA procedure. These preliminary results suggest that when adequate sample volumes are available, the immunostick ELISA can replace the mouse te st for the diagnosis of botulism in wild birds.