Insects transmit diseases to humans and animals . Insects and other arthropods also can transmit diseases to animals. Perhaps best known are mosquitoes, which spread malaria, yellow fever, dog heartworm and many other very important diseases. In the Rocky Mountain region the most important diseases that mosquitoes spread are types of equine encephalitis, which can be very serious to horses and occasionally infects humans as well. Insects sting, bite or otherwise create annoyance .
Many insects feed on the blood of animals.
Fleas, ticks, sucking lice and mange mites require an animal host to survive. Various biting flies, such as mosquitoes, blackflies, and deerflies, need a blood meal for them to produce young. Other insects can sting, such as yellowjackets, bees and harvester ants, usually in an effort to protect and defend their colony. However, the effect of these biting and stinging insects often harms humans and livestock.