Molecular insights versus morphological traits: rethinking identification of the closely related Angiostrongylus cantonensis and Angiostrongylus malaysiensis

Chanisara Kaenkaew; Abigail Hui En Chan; Naowarat Saralamba; Jiraporn Ruangsittichai; Kittipong Chaisiri; Vachirapong Charoennitiwat; Urusa Thaenkham

doi:10.1186/s13071-024-06140-9

Molecular insights versus morphological traits: rethinking identification of the closely related Angiostrongylus cantonensis and Angiostrongylus malaysiensis

Parasit Vectors. 2024 Feb 8;17(1):56. doi: 10.1186/s13071-024-06140-9.

Authors

Chanisara Kaenkaew¹, Abigail Hui En Chan¹, Naowarat Saralamba², Jiraporn Ruangsittichai³, Kittipong Chaisiri¹, Vachirapong Charoennitiwat¹, Urusa Thaenkham⁴

Affiliations

¹ Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
² Department of Molecular Tropical Medicine and Molecular Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
³ Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
⁴ Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. urusa.tha@mahidol.edu.

Abstract

Background: The closely related Angiostrongylus cantonensis and Angiostrongylus malaysiensis have been reported to coexist in Thailand and share similar hosts and life cycles. Recently, in an angiostrongyliasis outbreak in Thailand, both A. cantonensis and A. malaysiensis were found in the cerebrospinal fluid of affected patients. Morphological similarities, overlapping distribution, shared hosts and habitats, and the close genetics of the two Angiostrongylus species can complicate accurate species identification. Addressing these challenges, this study aims to evaluate whether a correlation between the morphological and genetic identities of A. cantonensis and A. malaysiensis can improve species identification accuracy.

Methods: Angiostrongylus spp. specimens from five zoogeographical regions in Thailand were subjected to morphological and molecular identification using the mitochondrial cytochrome b gene and the nuclear internal transcribed spacer 2 region (ITS2). The morphological characters for males and females were then validated using the species identity obtained from the nuclear ITS2 region.

Results: The results revealed that morphological misidentifications between these two closely related species are common due to overlapping morphological characters. Although certain male traits such as body length and width aided species differentiation, female traits were found to be less reliable. Furthermore, hybrid forms (8.2%) were revealed through the ITS2 results, which can further complicate morphological identification. Mito-nuclear discordance was also present in 1.9% of the Angiostrongylus specimens from Thailand, suggesting a complex historical interbreeding between the species.

Conclusions: Based on our findings, we suggest that nuclear ITS2 is a reliable marker for species identification of A. cantonensis and A. malaysiensis, especially in regions where both species coexist. Additionally, the scope and consequences of hybridization between the two closely related Angiostrongylus species should be further investigated in Thailand.

Keywords: Angiostrongylus cantonensis; Angiostrongylus malaysiensis; Hybrids; Misidentification; Morphological and molecular characters.

MeSH terms

Angiostrongylus cantonensis* / genetics
Angiostrongylus* / genetics
Animals
Female
Humans
Male
Phenotype
Phylogeny
Strongylida Infections* / epidemiology