Originally Posted by
Jessika
Another worry about drinking pond water is giardia and leptospirosis, so if you're worried that he may have contracted something then you can have him tested and vaccinated against them. If you're already vaccinated against them you should be fine.
I think heartworms are a little less of a worry since the larvae can only survive in the intermediate host, the mosquito, and unless the larvae have reached the L3 form they can not infect a host, not even if they are stuck by the mosquito or ingested. Certainly not if they eat mosquito eggs.
Those aside, there are also a myriad of other types of internal parasites that loooove hanging around water and in areas where wildlife roam around and urinate/defecate. Its a breeding ground for roundworms, tapeworms, you name if. But if you're on a monthly preventative for these it shouldn't be a problem :)