WHERE PARASITES DON'T LIVE—IT'S TOO COLD, RIGHT?

摘要

It is often thought that transmission of parasitic diseases does not occur during the winter months. This is a true statement relative to many parasites. Parasites exist in many different climates: some are associated with tropical climates, some withtemperate climates, some do just fine in arctic climates, and some do exceedingly well in just about any environment. What is often forgotten is that parasites are very commonly associated with vertebrate paratenic hosts, and that this means that transmission can easily occur any time of the year through predation. It is often also forgotten how much climates at the same latitude can vary dramatically; Port Cartier, Winnipeg, and Vancouver have vastly different seasons that can even differ dramaticallyfrom each other within the same season. Parasites that are not transmitted in one season in one area may be easily transmitted at the same time in another. Also, parasites are themselves not warm-blooded creatures, and although some are killed by freezing, some do just fine when frozen, and when they get cold they just enter a state where they await sufficient warmth to become active and infectious. This latter event can even occur with heartworms in mosquitoes.