Carbon monoxide (CO) has a much greater affinity for hemoglobin than does oxygen, effectively displacing oxygen from the blood. It combines with hemoglobin to form carboxyhemoglobin, reduces oxygen exchange, and causes mortality. Carbon monoxide is produced by incomplete combustion of any carbonaceous fuel, but most poisonings occur because of improperly functioning (yellow versus blue flame) space heaters or furnaces. Carbon monoxide is a colorless, odorless, and tasteless gas.
Recognition of malfunctioning heaters should alert one to the possibility of poisoning.
In late pregnancy sows, a high level of stillbirths and neonatal mortality is associated with CO poisoning. The sows themselves may show no other signs. Affected piglets usually show no lesions other than a pink to bright red color imparted to their blood and tissues by carboxyhemoglobin. Blood from affected piglets and fetuses with CO poisoning is usually characterized as “cherry red.” The concentration of carboxyhemoglobin in fetal thoracic fluid or blood of an affected pig can be used to confirm CO poisoning.