In Mexico, the incidence of intestinal parasitosis due to Giardia lamblia varies from 5 to 33 per cent, but its pathogenicity has until recently been a subject of controversy. Giardia is sometimes considered to be pathogenic and consequently there is a search for a specific therapy. Maris and Bushong studied a group of 85 children with giardiasis and found that the most common symptoms in the order of frequency were abdominal pain, weight loss, anorexia, pruritus, and irritability. Some gastroenterologists think the parasite may cause cholecystitis or cholangitis when it reaches the biliary ducts. However, even in the absence of symptoms attributable to the infection it is considered advisable by many doctors to free the patient of Giardia.
No very successful drug was found until in 1933 a series of experiments were started using atabrine in the treatment of giardiasis. Since this antimalarial gave good results, it was thought that the newer antimalarials might be effective also, and Basnuevo and Sotolongo (1946) tried chloroquine, paludrine, and pentaquine.