Abortion in Animals

the interruption of pregnancy with either the subsequent complete or partial resorption of the fetus or the expulsion of the dead fetus (miscarriage) or the immature fetus (premature birth) from the uterus.

Abortions are differentiated as noninfectious and infectious. The latter can result from penetration of pathogenic microorganisms such as bacteria, bacilli, and viruses into the maternal organism (infectious abortion) or from the invasion of parasitic worms (helminths) and single-celled protozoa—for example, trichomonads—into the body and organs of the female (infestation abortion). The factors causing abortions can directly affect the fetus (idiopathic abortion) or the female organism (symptomatic abortion).

Idiopathic noninfectious abortions occur when the female or male sexual cells become inviable as a result of illness or of metabolic disturbances which have a negative effect on the formation of sexual cells and on the development of the already fertilized female sexual cell (the zygote). Inflammatory processes in the fetal membranes or in the tissues of the fetal sac may also cause abortions. Idiopathic infectious abortions are the indication of a definite infectious or infestation disease (vibriosis, brucellosis, paratyphoid fever, trichomoniasis, etc.), the pathogens of which directly affect the fetus, the fetal membranes, or the fetal sac.

Symptomatic abortions, regardless of the factors causing them, occur as a result of changes in the maternal organism which influence the normal course of pregnancy. Noninfectious symptomatic abortions are caused by a qualitative or quantitative diet imbalance—an insufficiency of vitamins, proteins, minerals, and so on, in the feed; various traumas—for example, an animal’s abrupt and rapid movements in the last stage of pregnancy; and feed poisonings. Certain infectious and infestation animal diseases (anthrax, glanders, su-auru, and so on) can cause infectious symptomatic abortions.

In animals having multiple births, abortions are termed complete when all the fetuses die and incomplete when some of the fetuses are born alive. Ordinarily the dead fetus is expelled from the maternal organism. However, a concealed abortion can also occur without any apparent clinical indications. In this instance, the fetus is resorbed in the maternal organism at the onset of pregnancy. A concealed abortion can be detected by a veterinarian or veterinary technician by retesting for pregnancy. In large animals (mares and cows), the resumption of the sexual cycle (the resumption of estrus) one to three months after insemination is an indication of a concealed abortion. Abortions are a serious danger for the maternal organism, particularly abortions complicated by a putrefactive infection; these abortions can often lead to the death of the female. Animals which have aborted occasionally remain sterile for an extended period, and their productivity declines. With infectious and certain infestation abortions, a quarantine is imposed on the farm. In all instances of abortions in agricultural animals, the veterinarian or veterinary technician must be informed immediately. They in turn establish the cause of the abortion, provide immediate aid for the stricken animal, and organize special measures on the farm, consisting of improving the conditions under which the animals are kept, correcting their feeding and use, and isolating them from contagious diseases.