The post-teenage decline in the disease has often been taken as evidence for a gradually acquired immunity, but this probably plays a less significant role in the decline than do changing patterns of water contact. However, "concomitant immunity" is known to occur in experimental animals. The adult worms induce an immune response that has no effect on the adult worms but that protects the host from reinfection by destroying many of the invading cercariae. The adult worms, themselves, are able to circumvent this immune response 2 to 3 days after boring into the skin by acquiring host antigens that become bound to the surface of the parasite; the host is no longer able to recognize the worms as foreign organisms. Whether concomitant immunity plays any significant role in humans has yet to be determined.

Your Heart and Nutrition

Your Heart and Nutrition

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