E. ilocanum at www.cdfound.to.it
The metacercarial cysts of echinostomes most likely excyst in the jejunum or ileum of the human host. Factors that influence excystation could include intestinal pH, temperature, or bile salt concentration. After excystation, the young flukes use their spiny tegument and large suckers to attach to the wall of the lower small intestine. It is also thought that the collar spines, especially the backwardly-pointed ones, help the flukes to secure themselves into the intestinal mucosa (Haseeb and Eveland). It is these spines along with the large oral and ventral suckers that are thought to cause damage to the intestinal mucosa in the form of inflammation and ulceration, and thereafter cause the other symptoms associated with echinostomiasis (Haseeb and Eveland, Fried and Graczyk). The life span of echinostomes in the human host (meaning the duration of infection) is thought to depend largely on the combination of infecting species (Haseeb and Eveland).
The number of parasites present in the body correlates with the amount of clinical symptoms that present themselves. In other words, the greater the worm burden, the worse the disease. In fact, in many cases of light-to-moderate infection, the disease can be asymptomatic. Most symptoms will not be present in an infected person, and few cases have been documented with significant morbidity. However, there are several ways in which echinostomiasis clinically presents itself.
Bearing in mind that symptoms often may be absent even with infection, and that they will be worse as infection becomes heavier, here is a list of symptoms that have been associated with echinostomiasis:
(Fried and Graczyk, Echinostomiasis: A Common but Forgotten Food-borne Disease; Fried, Graczyk, and Tamang. Food-borne Intestinal Trematodiases in Humans; John and Petri. Markell and Voge's Medical Parasitology, 9th ed.)