Proper identification of anisakine worms

Abstract

Luminal, gastric, intestinal and mesenteric forms of anisakiasis are known and can be encountered where raw or undercooked marine fish or squid are eaten. Although the anisakine nematodes which cause infection in humans are usually identified after surgical removal, laboratory personnel should be aware of their similarities to other nematodes. Cases have been reported of detection of larval nematodes in the throats or mouths of patients who have vomited or coughed. When such specimens are submitted to the clinical laboratory, problems in identification can be minimized by proper fixation and clearing. Systems for study involving clearing in phenol-ethanol and dissection to observe presence or absence of a ventricular appendix or intestinal cecum to distinguish Anisakis-, Phocanema- and Contracaecum-type larvae are described. Distinguishing characteristics are illustrated. The recovery of a Phocanema-type larva from a California woman is reported; the presence of the larvae in fish sold for human consumption in San Diego is exemplified.