Reevaluating the presence of Rhipicephalus australis (Acari: Ixodidae) in Southeast Asia: A phylogenetic approach based on Cambodian tick samples

Morphological variability between Rhipicephalus australis and R. microplus has led to taxonomic ambiguity, leading to species misidentification. Rhipicephalus australis is reported to have a distribution range in Pacific Ocean region extending to several Southeast Asian countries, including Cambodia, although its presence in continental Southeast Asia has not been supported by molecular data. With growing evidence of conflicting morphological characters, this study aimed to evaluate the presence of R. australis in Cambodia using both morphological and molecular identification. Tick specimens were collected from cattle across 21 provinces of Cambodia, and a subset of 95 R. microplus complex (37 morphologically identified as R. australis, 39 R. microplus, and 19 nymphs) was selected for molecular analysis. DNA barcoding of the cox1 gene was performed, and a maximum likelihood phylogenetic tree revealed that all specimens clustered within R. microplus clade A. These findings, along with previous observations from other regions, suggest that, in the absence of molecular data, there is no definitive evidence to support the presence of R. australis in continental Southeast Asia, particularly in Cambodia.