Alveolar echinococcal disease
Cystic echinococcal disease
Detection of antibodies to Echinococcus species, including Echinococcus multilocularis and Echinococcus granulosus
Centrifuge and aliquot serum into plastic vial.
Depending on cyst location, individuals may not develop high enough antibody titers to be detectable by serologic assays, leading to false-negative results. Cysts localized to the lungs, central nervous system, or spleen or cysts that are senescent, calcified, or dead are associated with lower serologic reactivity.
False-positive results may occur in patients with other helminth infections, including with Taenia species, Schistosoma species, and Strongyloides. Careful correlation with imaging findings and exposure history is required.
This assay may not detect antibodies to other species of Echinococcus, including Echinococcus vogeli and Echinococcus oligarthrus, both fairly uncommon causes of hydatid disease in humans.
Echinococcosis, also referred to as hydatidosis or hydatid disease, is 1 of the 17 neglected tropical diseases recognized by the World Health Organization and affects over 1 million people worldwide. Echinococcus species are tapeworms or cestodes, and 2 main species infect humans: Echinococcus granulosus and Echinococcus multilocularis.
With respect to geographic distribution, E granulosus can be found worldwide but, more frequently, is found in rural grazing areas where dogs may feed on infected sheep or cattle carcasses. E multilocularis is largely localized to the northern hemisphere. The definitive hosts for E granulosus are dogs or other canids, while the definitive host for E multilocularis are foxes and, to a much lesser extent, canids. Echinococcus tapeworms reside in the small intestine of definitive hosts and release eggs that are passed in the feces and ingested by an intermediate host, typically sheep or cattle in the case of E granulosus or small rodents for E multilocularis. The eggs hatch in the small bowel, releasing an oncosphere that penetrates the intestinal wall and migrates through the circulatory system to various organs where it develops into a cyst that gradually enlarges, producing protoscolices and daughter cysts, which fill the interior. The definitive host becomes infected following ingestion of these infectious cysts. Humans become accidentally infected following ingestion of Echinococcus eggs.
In humans, E granulosus (cystic echinococcal disease) cysts typically develop in the lungs and liver. The infection may remain silent or latent for years (5-20 years) prior to cyst enlargement and symptom manifestation. Symptomatic manifestations include chest pain, hemoptysis, and cough for pulmonary involvement and abdominal pain and biliary duct obstruction for liver infection. E multilocularis (alveolar echinococcal disease) infections manifest more rapidly than those of E granulosus and similarly to a rapidly growing, destructive tumor, resulting in abdominal pain and biliary obstruction. Rupture of cysts can produce fever, urticaria, and anaphylactic shock.
Diagnosis of echinococcal infections relies on characteristic findings by ultrasound or other imaging techniques and serologic findings. Fine-needle aspirates of cystic fluid may be performed; however, they carry the risk of cyst puncture and fluid leakage, potentially leading to severe allergic reactions. Importantly, infected individuals do not shed eggs in stool.
The absence of antibodies to Echinococcus species suggests that the individual has not been exposed to this cestode. A single negative result should not be used to rule out infection (see Cautions).
Consider repeat testing on a new serum sample in 1 to 2 weeks.
Results suggest infection with Echinococcus. False-positive results may occur in settings of infection with other helminths or in patients with chronic immune disorders. Results should be considered alongside other clinical findings (eg, characteristic findings on imaging) and exposure history.