Echinococcosis (hydatidosis) is the infection caused by cestodes of the genus Echinococcus. Humans are potential intermediate hosts and can become infected by ingesting eggs passed in the feces of an infected animal. The resulting disease is called hydatidosis, or hydatid disease. Four species are known pathogens of the disease: E. granulosus, E. multilocularis, E. oligarthrus and E. vogeli. The infection caused by E. granulosus is referred to as cystic hydatid disease (CHD) and results in cysts in various organs, especially the liver and lungs. These cysts may become quite large and contain hundreds or thousands of scoleces called hydatid sand. The degree of antibody response to these cysts will vary depending on their location and degree of calcification. Liver cysts typically produce a higher antibody response than lung cysts. Infection due to E. multilocularis is referred to as alveolar hydatid disease (AHD), and also occurs as cysts that may spread throughout the infected tissue.

Since Echinococcus eggs are not shed by infected humans, serological determination has been important in the diagnosis of hydatid disease. A number of tests have been used, including latex agglutination (LA), indirect hemagglutination (IHA), complement fixation (CF), agar gel diffusion (AGD) and enzyme linked immunosorbent assay (ELISA). Cross reactivity between echinococcosis and cysticercosis (Taenia solium infection) will occur to some degree in this assay due to the use of crude antigen. It is recommended that any sample showing a positive result by this test be confirmed by additional testing.