Detection of Ehrlichia spp., Anaplasma spp., Rickettsia spp., and other eubacteria in ticks from the Thai-Myanmar border and Vietnam

Abstract

A total of 650 ticks, including 13 species from five genera, were collected from animals, from people, or by flagging of the vegetation at sites on the Thai-Myanmar border and in Vietnam. They were tested by PCR to detect DNA of bacteria of the order RICKETTSIALES: Three Anaplasma spp. were detected in ticks collected in Thailand, including (i) Anaplasma sp. strain AnDa465, which was considered a genotype of Anaplasma platys (formerly Ehrlichia platys) and which was obtained from Dermacentor auratus ticks collected from dogs; (ii) Anaplasma sp. strain AnAj360, which was obtained from Amblyomma javanense ticks collected on a pangolin; and (iii) Anaplasma sp. strain AnHl446, which was closely related to Anaplasma bovis and which was detected in Haemaphysalis lagrangei ticks collected from a bear. Three Ehrlichia spp. were identified, including (i) Ehrlichia sp. strain EBm52, which was obtained from Boophilus microplus ticks collected from cattle from Thailand; (ii) Ehrlichia sp. strain EHh324, which was closely related to Ehrlichia chaffeensis and which was detected in Haemaphysalis hystricis ticks collected from wild pigs in Vietnam; and (iii) Ehrlichia sp. strain EHh317, which was closely related to Ehrlichia sp. strain EBm52 and which was also detected in H. hystricis ticks collected from wild pigs in Vietnam. Two Rickettsia spp. were detected in Thailand, including (i) Rickettsia sp. strain RDla420, which was detected in Dermacentor auratus ticks collected from a bear, and (ii) Rickettsia sp. strain RDla440, which was identified from two pools of Dermacentor larvae collected from a wild pig nest. Finally, two bacteria named Eubacterium sp. strain Hw124 and Eubacterium sp. strain Hw191 were identified in Haemaphysalis wellingtoni ticks collected from chicken in Thailand; these strains could belong to a new group of bacteria.

FIG. 1.

Map showing the locations where ticks were collected in Thailand and Vietnam and the results of the molecular detection of rickettsial DNA (in the following order: bacteria/tick species/number of ticks tested/number of positive ticks/host).

FIG. 2.

Phylogenetic tree based on studies of 960 sites of the 16S RNA genes of bacteria of the genera Anaplasma, Ehrlichia, Neorickettsia, and Wolbachia and drawn by using MEGA software (version 2.1) (12). The distance matrix was calculated by using Kimura-2 parameters. Trees were obtained by the neighbor-joining method. The numbers at the nodes are the proportions of 500 bootstrap resamplings that support the topology shown. The bacteria detected in this work are highlighted.

FIG. 3.

Phylogenetic tree based on studies of 1,035 sites of the citrate synthase genes of bacteria of the genus Rickettsia, drawn as described in the legend to Fig. 2. The bacteria detected in this work are highlighted.