We recorded the first confirmed case of Cercopithifilaria bainae , a tick-borne filarioid of canids, in a stray dog from Bangkok Province, Central Thailand. Microscopic examination of thin blood films revealed unsheathed microfilariae, measuring on average 171.59 μm in length and 3.54 μm in width, characterized by a straight, slender, or slightly curved body. The body is relatively uniform in width, tapering gradually at the posterior end. The microfilariae presented with a rounded head, an elongated cephalic space containing one nucleus, and an internal column of nuclei extending across the majority of the body length. Molecular analysis of the cox 1 sequence (843 bp) confirmed species identity (99.84%) as C. bainae . Bayesian phylogenetic and molecular clock analyses estimated the origin of Cercopithifilaria lineage to the Middle Miocene (∼11.73 Mya, 95% HPD: 8.65–15.11 Mya), coinciding with the origins of key host families, Canidae (∼14.06 Mya) and Cervidae (∼12.80 Mya). Cercopithifilaria bainae shared a most recent common ancestor with the progenitors of Cercopithifilaria japonica , Cercopithifilaria grassii , and Cercopithifilaria roussilhoni at ∼10.55 Mya (95% HPD: 6.78–14.51 Mya) in the Middle Miocene. Meanwhile, the radiation of extant C. bainae haplotypes occurred much more recently during the Early Pleistocene (∼0.71 Mya, 95% HPD: 0.28–1.23 Mya), suggesting a history of ghost lineages, perhaps persisting in prehistoric caniforms, before adaptation in domestic dogs. These findings significantly expand the geographical range of C. bainae into Asia and highlight the importance of combining morphological identification with molecular phylogenetics for diagnosing and investigating neglected filarioid. • First evidence of Cercopithifilaria bainae in a stray dog from Thailand. • Microfilariae were inadvertently detected in the blood beyond the dermal region. • Origin of Cercopithifilaria coincided with the origin of canid and cervid hosts. • C. bainae likely persisted in ancient caniforms before adapting to domestic dogs. • The findings significantly expand the geographical range of C. bainae into Asia.
Narapakdeesakul et al. (Wed,) studied this question.