A:   Internal parasites which affect cattle include: roundworms, flukes, and tapeworms. Tapeworms are not considered to be of economic importance in cattle. Flukes are a problem in the Gulf Coast states and Pacific Northwest.

There are several different species of roundworms that can affect cattle in different parts of the United States. Of these species, the one thought to be of most importance is Ostertagia, also known as the brown stomach worm. There are several aspects of this worm's life cycle that are important in designing a complete deworming program. Cattle are most susceptible to this worm at less than 2 years of age. Most cows greater than 2-3 years of age have developed immunity to this worm and do not show an economical benefit to deworming: However, deworming of cows can decrease the exposure of younger animals pastured in the same field.

Another important aspect of this roundworm's life cycle is its ability to go into hibernation in the abomasum, or true stomach, of cattle. This is commonly known as the inhibited larval stage of Ostertagia. This process can occur during the winter with these larvae maturing and developing into adult worms in the spring. While not common, large numbers of inhibited larvae can cause individual calves to show severe signs of parasitism, severe diarrhea, and rapid weight loss. This condition is known as Type II Ostertagiasis. Most but not all dewormers kill inhibited stage larvae.

Internal parasites can be controlled using a number of different products that may be in to form of a paste, injectible, pour-on, drench, and delivered through the mineral program. Consult your veterinarian to help you determine the targeted parasite and the best pRoduct to accomplish the task.