Background: Among the 21 species in the genera Angiostrongylus, only one has been confirmed to cause disease in humans. A. cantonensis is a parasitic nematode of rodents whose life-cycle involves a maturation phase in the central nervous system. Infected humans often develop eosinophilic meningitis, and when the infection is confirmed, the condition is called neuroangiostrongyliasis. The two most commonly found species of Angiostrongylus in Thailand are A. cantonensis and A. malaysiensis. Both species exhibit a very similar life-cycle, but only A. cantonensis is considered a human pathogen. Recent molecular studies revealed that A. cantonensis and A. malaysiensis have an overlapping distribution in many parts of Thailand which might indicate that A. malaysiensis is also causing human disease. The two species have similar morphologies, which results in misidentification.

Objective: Compare the morphological identification of the two species with their corresponding molecular analysis.

Materials and Methods: Polymerase chain reaction (PCR) was used to amplify the mitochondrial cytochrome c oxidase subunit 1 (COX1) gene. Fourteen adult worms were obtained from Phayao province, located in Northern Thailand. All fourteen adult worms were morphologically identified and compared with the corresponding PCR results.

Results: Analysis of the data showed a 28.6% mismatch between the two assays.

Conclusion: Further refinement and research are needed to achieve a 0% mismatch to unequivocally differentiate the two species. Understanding the epidemiology and clinical implications of these species is essential for infection control and patient management.