Morphological and molecular identification of medically important questing Dermacentor species collected from some recreational areas of Peninsular Malaysia

Metagenomic profile of the bacterial communities associated with Ixodes granulatus (Acari: Ixodidae): a potential vector of tick-borne diseases

Ixodes granulatus Supino, 1897 (Acari: Ixodida) is one of Malaysia's most common hard ticks and is a potential vector for tick-borne diseases (TBDs). Despite its great public health importance, research on I. granulatus microbial communities remains largely unexplored. Therefore, this study aimed to investigate the bacterial communities of on-host I. granulatus collected from three different recreational areas on the East Coast of Peninsular Malaysia using high throughput Next Generation Sequencing (NGS). A total of 9 females on-host I. granulatus were subjected to metabarcoding analysis targeting V3-V4 regions of 16S ribosomal RNA (rRNA) using the Illumina MiSeq platform. This study identified 15 bacterial phyla corresponding to 19 classes, 54 orders, and 90 families from 435 amplicon sequence variants (ASVs), revealing a diverse bacterial community profile. Together with 130 genera assigned, local I. granulatus harbored 4 genera of pathogens, i.e., Rickettsia da Rocha Lima, 1916 (Rickettsiales: Rickettsiaceae) (58.6%), Borrelia Swellengrebel 1907 (Spirochaetales: Borreliaceae) (31.6%), Borreliella Adeolu and Gupta 2015 (Spirochaetales: Borreliaceae) (0.6%), and Ehrlichia Cowdria Moshkovski 1947 (Rickettsiales: Ehrlichiaceae) (39.9%). Some endosymbiont bacteria, such as Coxiella (Philip, 1943) (Legionellales: Coxiellaceae), Wolbachia Hertig 1936 (Rickettsiales: Ehrlichiaceae), and Rickettsiella Philip, 1956 (Legionellales: Coxiellaceae), were also detected at very low abundance. Interestingly, this study reported the co-infection of Borrelia and Ehrlichia for the first time, instilling potential health concerns in the context of co-transmission to humans, especially in areas with a high population of I. granulatus. This study successfully characterized the tick microbiome and provided the first baseline data of I. granulatus bacterial communities in Malaysia. These results support the need for way-forward research on tick-associated bacteria using NGS, focusing on medically important species toward TBD prevention.

Comparative analysis of the mitochondrial genome of Dermacentor steini from different regions in China

Ticks are a group of blood-sucking ectoparasites that play an important role in human health and livestock production development as vectors of zoonotic diseases. The phylogenetic tree of single genes cannot accurately reflect the true kinship between species. Based on the complete mitochondrial genome analysis one can help to elucidate the phylogenetic relationships among species. In this study, the complete mitochondrial genome of Dermacentor steini (isolate Longyan) was sequenced and compared with the mitochondrial genes of 3 other Chinese isolates (Nanchang, Jinhua and Yingtan). In Dermacentor steini 4 isolates had identical or similar mitochondrial genome lengths and an overall variation of 0.76% between sequences. All nucleotide compositions showed a distinct AT preference. The most common initiation and stop codons were ATG and TAA, respectively. Fewer base mismatches were found in the tRNA gene of D. steini (isolate Longyan), and the vicinity of the control region and tRNA gene was a hot rearrangement region of the genus Dermacentor. Maximum likelihood trees and Bayesian trees indicate that D. steini is most closely related to Dermacentor auratus. The results enrich the mitochondrial genomic data of species in the genus Dermacentor and provide novel insights for further studies on the phylogeographic classification and molecular evolution of ticks.

A checklist of the ticks of Malaysia (Acari: Argasidae, Ixodidae), with lists of known associated hosts, geographical distribution, type localities, human infestations and pathogens

Studies of ticks in Malaysia from past articles were reviewed, resulting in a list of 47 species belonging to seven genera (Argas, Ornithodoros, Amblyomma, Dermacentor, Haemaphysalis, Ixodes, and Rhipicephalus). The most prevalent genus in Malaysia is Haemaphysalis (20 species), followed by Amblyomma (eight species) and Dermacentor (seven species). Out of 47 species, only 28 have bitten humans, mostly belonging to Haemaphysalis. The most researched tick-borne pathogens in Malaysia are Rickettsia and Anaplasma, and most research was focused on the tropical-lineage brown dog ticks, R. sanguineus sensu lato, and the cattle ticks, Haemaphysalis bispinosa and Rhipicephalus microplus. 18 species were excluded from the list due to lack of definite records or dubious findings: Ornithodoros mimon, O. turicata, Amblyomma breviscutatum, A. clypeolatum, A. integrum, A. maculatum, Dermacentor marginatum, D. taiwanensis, Haemaphysalis birmaniae, H. flava, H. humerosa, H. longicornis, H. punctata, H. sulcata, Ixodes holocyclus, Rhipicephalus appendiculatus, R. annulatus and R. bursa. This paper presents the first complete and updated list for Dermacentor and Ixodes tick species in Malaysia since Kohls (1957).  

First Record of the Tortoise Tick, Amblyomma geoemydae (Cantor, 1847) (Acari: Ixodidae) Parasitizing a Tree Shrew, Tupaia glis (Scandentia: Tupaiidae) in West Malaysia

The tick genus Amblyomma Koch, 1844 (Acari: Ixodidae) has received little attention in Malaysia; therefore, its associated hosts and distribution records are poorly known. In this study, we collected six Amblyomma sp. individuals (two larvae and four adults) that infested a common treeshrew, Tupaia glis (Diard, 1820) (Scandentia: Tupaiidae) caught in a recreational area in Sungai Lembing, Pahang (West Malaysia). The adult female ticks were morphologically identified according to taxonomic keys prior to molecular identification using cytochrome oxidase subunit I (COI) and 16S rDNA genes. The ticks were genetically verified as Amblyomma geoemydae (Cantor, 1847) with 98%-99% similarity to the available GenBank sequences. Neighbor-joining (NJ) trees indicated that A. geoemydae was clearly distinguished from other Amblyomma ticks and this was supported with high bootstrap values. This paper is the first to report A. geoemydae ticks infesting T. glis and provides a new tick-host record from West Malaysia. This information is significant for further investigation, specifically on this tick species as potential vector of tick-borne disease (TBD) agents.