Internal Parasites of Horses and Mules

THE DOMESTIC EQUINES provide shelter and subsistence to approximately 150 kinds of protozoa and worms which live, as internal parasites.^ There are few horse owners who have not had some first-hand experience with many of these, and nearly everyone is familiar, in one way or another, with at least some of them. Among the protozoa are the blood-inhabiting trypanosomes and piroplasmata, the ciliates of the large bowel, and several miscellaneous species. The parasitic worms include flukes, tapeworms, stomach worms, large roundworms, strongyles, pinworms, lungworms, filariae, and some others. Some of the worst diseases of equines are caused by these invaders; yet they do not, as a rule, cause specific and spectacular diseases. In every case of harmful parasitism, the damaging effects are essentially of two kinds—general and specific. The general eflect, although seldom as obvious, is unquestionably more important than the specific effect from an economic standpoint; it always causes a loss in the functional efficiency of the animal as a working unit. In some instances, as in such a disease as dourine, the specific effects, clinical or pathological or both, definitely indicate the disease. In most cases, however, as best typified.^ perhaps, by strongylosis, the