Lime juice does kill some bacteria, it is not effective against all types of bacteria. In fact, lime juice may even promote the growth of some bacteria. Therefore, it is not safe to assume that the lime juice will kill all of the bacteria in the shrimp.  Additionally, lime juice is not effective against parasites, so it will not kill any parasites in the shrimp. However, the lime juice may make the parasites taste better, which could possibly make them easier to remove from the shrimp.