Hemolytic Disease of The Newborn - in Animals

In Animals

Hemolytic disease is a well-known condition in newborn foals, especially in Thoroughbreds and mules. Mares or jennies which have been sensitized by a previous pregnancy develop antibodies by fetal blood cells crossing the placental barrier. The iso-antibodies do not transcend the fetal barrier, but are present in colostrum. The Neonatal Fc receptor which in case of humans transfer the maternal antibody from mother through placenta to fetus, in this case is involved in transporting the IgG1 antibodies from mother animal's mammary gland into milk and then again from the ingested milk across the newborn intestine into the newborn animal's circulation. The placenta of mammals can be of many varieties and unless it is hemochorial like humans and some rodents, the IgG of mother cannot directly cross the placenta and passively immunize the fetus. Horse (and also ruminants) have epitheliochorial placenta. Thus IgG1 will enter the bloodstream of the foal only after birth when colostrum immunoglobulins are exposed to FcRn in the newborn intestine, in the first days of life. Hence, hemolytic disease will develop only after birth : first to 4th day in foal and 3 to 7 days in newborn mules. Affected animals show lethargy, recumbency, tachycardia, and progressive icterus of eye and mouth mucosae, which rapidly leads to death. The condition is also described in newborn pigs and other animals