The number of parasites infecting animals ("parasite load") varies with the seasons. This burden is generally heavier in warm months, declining in autumn and winter. This is largely due to the requirement of parasites for warmth and moisture in their development outside the host. Eggs hatch more readily and immature parasite forms develop faster with high humidity and warm temperatures. In summer months, the worm's life cycle is shorter and a higher proportion of larvae survive. Therefore, worm burdens in dogs increase tremendously during the warmer seasons.

Immunity to Parasite Infection

Damage to Host