A pinboard by
Rawadee Kumlert

PhD. Student, Mahidol University/ Faculty of tropical medicine


A novel methodology combining morphological with molecular identification of Walchia chigger mites

Scrub typhus disease is zoonotic disease transmitting by Trombiculid mite called “chigger”. We need to identify chigger

mite under compound microscope by slide preparation method to destroy internal tissue that it mean unable to study molecular in the same time. However, chigger mites are member of Chelicerate arthropods which auto-fluorescence property of exoskeleton, it will be see under UV light. Walchia, a diverse chigger mite species on rodent hosts, are good demonstration for the study of morphological and molecular correlation. Total of 59 Walchia chigger mites were selected from natural rodents collecting in scrub typhus areas. Individual chigger mites can be identified by both fluorescence and conventional light microscopy for morphotyping to species level with 16 characters. At the same time can be used for DNA extraction. The DNA quality of the specimens has been verified by PCR of COI gene amplification and sequencing. For the result, Approximately 640 pb of COI partial fragments was analyzed. 21 COI sequences of 5 species of Walchia chigger mites were presented. Phylogenetic analysis of COI sequences among Walchia specimens showed that the morphological and molecular identification are correlated reciprocally. It can be concluded that morphological studies by using UV light combine with visible light can actually preserve the quality of DNA materials enough for COI fragment analysis. This is the novel microscopic method for morphological identification of the chigger species that would preserve DNA for molecular studies.


Host body microcosm and ectoparasite infracommunities: arthropod ectoparasites are not spatially segregated.

Abstract: We studied the distribution of ectoparasite species (an ixodid tick, a chigger mite, 7 mesostigmate mites, 5 fleas and 3 lice) on bodies of 5 species of rodent hosts from the marshlands in Argentina to establish whether arthropod ectoparasites are segregated across body parts of the same host individual. We asked (a) whether an individual ectoparasite species prefers certain parts of the body of its host and, if yes, whether these preferences overlap among ectoparasite species; (b) whether ectoparasite species composition differs among different parts of a host's body; and (c) whether co-occurrences of ectoparasite species within pre-defined body parts of a host are non-random and, if yes, whether ectoparasites co-occur in the same body part of a host either less or more often than expected by chance. It was found that, in general, ectoparasite species were not segregated across body parts of a host. Although some ectoparasites preferred certain body parts, these preferences were similar among ectoparasites belonging to different species and/or higher taxa resulting in similarity among host body parts in ectoparasite species composition. In addition, ectoparasite species demonstrated a tendency to co-occur on the same body parts of a host and not to be segregated among them. It was concluded that the distribution of ectoparasites on the body of a small mammalian host is driven mainly by their interaction with the host rather than by distinct preferences or interactions among ectoparasite species.

Pub.: 06 Sep '12, Pinned: 25 Aug '17

A Revised Checklist of Chigger Mites (Acari: Trombiculidae) From Thailand, with the Description of Three New Species.

Abstract: Chigger mites of Thailand were studied on the basis of larvae collected from 19 small mammal species (17 species of Rodentia, 1 species of Erinaceomorpha, and 1 species of Scandentia) and revision of published data. Samples of 38 trombiculid species were collected from 11 provinces. Three new species were described: Trombiculindus kosapani sp. nov., Helenicula naresuani sp. nov., and Walchia chavali sp. nov. Ten species were recorded in Thailand for the first time: Leptotrombidium sialkotense Vercammen-Grandjean and Langston, 1976; Leptotrombidium subangulare Wen and Xiang, 1984; Leptotrombidium tenompaki Stekolnikov, 2013; Leptotrombidium turdicola Vercammen-Grandjean and Langston, 1976; Leptotrombidium yunlingense Yu, Yang, Zhang and Hu, 1981; Lorillatum hekouensis Yu, Chen and Lin, 1996; Helenicula pilosa (Abonnenc and Taufflieb, 1957); Gahrliepia xiaowoi Wen and Xiang, 1984; Walchia minuscuta Chen, 1978; and Walchia ventralis (Womersley, 1952). In all, 99 chigger mite species were considered; the presence of 93 species was established in Thailand by original data or properly documented records in the scientific literature. Evidence for 64 species records of 147 from a previous checklist of Thai chiggers (Tanskul 1993) remains unknown. Distribution of chigger species by geographical regions of Thailand is discussed.

Pub.: 09 Jan '16, Pinned: 25 Aug '17