At a glance
- A diagnosis of A. cantonensis is strongly suggested when symptoms suggest bacterial meningitis, but testing reveals eosinophilia. Cases of A. costaricensis are often diagnosed postoperatively by examination of surgical specimens. Serologic tests for both species have been developed but are not readily avaialble.
Recommended tests
Angiostrongylus cantonensis
A diagnosis of A. cantonensis is strongly suggested when symptoms suggest bacterial meningitis, but testing reveals eosinophilia either in the blood (>5%) or in cerebrospinal fluid (>10%) and travel history reveals recent travel to endemic areas of the world. History of ingestion of raw or undercooked intermediate hosts or possibly transport hosts is a crucial clue as well. However, ill persons may not be aware of ingestion of foods that could lead to infection. Examination of the CSF can reveal eosinophilia (>10% eosinophils), elevated protein, and low or normal CSF glucose. It is important to note, however, that eosinophilia in the CSF and in the blood may not be present on initial presentation or in late stages of infection. The CSF pressure is generally elevated. Recovery of A. cantonensis from the CSF confirms the diagnosis; however, the organism is rarely detected on microscopy as it can adhere to the meninges.
Serologic tests have been developed but are not commercially available. A few specialty or research laboratories offer serologic tests, but the sensitivity and specificity of the tests may not be optimal, and the infection is often identified only on convalescent sera. In addition, some research laboratories have developed PCR tests for use with CSF and tissue. Because of the difficulty in making the diagnosis, it is important to rule-out other causes of eosinophilic meningitis. Neuroimaging studies can be useful as there usually is an absence of focal lesions on CT scan, which helps to distinguish A. cantonensis eosinophilic meningitis from focal lesions which may be seen in neurocysticercosis and gnathostomiasis. Because eggs are not passed in the feces, a stool examination is not useful for diagnosis.
Angiostrongylus costaricensis
Although several serologic tests have been developed by researchers, they are not readily available. Cases are often diagnosed postoperatively by examination of surgical specimens. Most patients have leukocystosis, often with a high percentage of eosinophils (>10%). Radiologic examination of the gastrointestinal tract may demonstrate edema and spasticity in the areas of inflammation. Because eggs are not passed in the feces, a stool examination is not useful for diagnosis. The parasitic differential diagnosis includes anisakiasis and toxocariasis.