SCIENCE WATCH; MILK KILLS A PARASITE
Published: September 20, 1983
AN intestinal parasite that frequently infects children is killed by a component of human milk, according to a study reported in the Sept. 23 issue of the journal Science. While the authors say human milk ''may play a protective role'' in infants exposed to the parasite, it is not known whether those raised on mother's milk have a lower incidence of such infections.
The parasite is a free-swimming protozoan, known as Giardia lamblia, that infects the digestive tract, causing diarrhea, abdominal pain and weight loss. Its cysts are discharged in the feces and contagion is usually by contaminated water. It is a common cause of ''traveler's diarrhea.''
The agent has not yet been identified, but it is so powerful half of a culture of parasites was killed within 30 minutes by a solution containing only 3 percent of human milk. The substance was not found in milk from cows or goats. Nor does it appear to be an antibody, or chemical defender, produced by the mother.
The agent was also found to kill two other human parasites: an amoeba (Entamoeba histolytica) that infects the colon, and a protozoan (Trichomonas vaginalis) that lives in the urogenital tract. Under suspicion as a component of the parasite-killing substance is an enzyme (bile salt-stimulated lipase) that occurs in human milk but has not been found in mammals other than the primates.
Authors of the report were Drs. Frances D. Gillin and David S. Reiner of the University of California Medical Center in San Diego and Chi- sun Wang of the Oklahoma Medical Research Foundation in Oklahoma City.