Parasites and Insects Affecting Livestock

PARASITES that attack livestock and poultry may live on the skin or in its layers (external parasites) or in the digestive tract, the liver, tlie lungs, the kidneys, and elsewhere in the body (internal parasites). With few exceptions, the external parasites are insects or forms related to insects. Most of the internal parasites.are either microscopic organisms known as protozoa or belong to a group of larger parasites known collectively as worms. Although the direct injuries produced by external parasites are confined for the most part to the skin, some of them have a profound effect on the general health. In addition to causing serious annoyance, some of the bloodsucking insects and related forms such as ticks introduce the germs of diseases. Internal parasites seriously injure the parts of the body in which they become localized, their presence in large numbers frequently resulting in stunting, unthriftiness, wasting, and death. In this article the more important external and internal parasites that are common to different kinds of domestic animals and poultry are discussed.