It can reduce the animal's ability to reduce the pathogenicity of a parasite and may also allow parasites to be more fecund and produce more eggs. Conversely, it's been found that protein supplements given to sheep and goats might help an animal to reduce the fecundity of its parasites. The climate of the area has a direct effect on the species of parasites any animal may come into contact with. There are some parasite species that require tropical climates, others that can survive subzero temperatures and many that have an ideal growing temperature somewhere in between. Heated buildings provide temperatures that may be warm enough for some of the tropical parasites to survive colder climates.
Some parasites have life cycles that reflect the climate in which they survive.
In temperate regions, there are parasites that can go dormant in different life stages during the time of year that has unfavorable weather. This is called overwintering or oversummering. The particular season during which a parasite goes dormant varies with the individual parasite and with the temperature extremes. For example, one parasite may go dormant and oversummer in hotter regions while the same parasite goes dormant in the winter in colder regions. Dormancy does not only occur outside the animal, but many life cycles utilize a dormant period within the host's body which allows a parasitic infection to become patent during more ideal climatic conditions for parasite reproduction.