Investigation of vertical and horizontal transmission of Spiroplasma in ticks under laboratory conditions.

Many arthropods harbour bacterial symbionts, which are maintained by vertical and/or horizontal transmission. Spiroplasma is one of the most well-known symbionts of ticks and other arthropods. It is still unclear how Spiroplasma infections have spread in tick populations despite its high prevalence in some tick species. In this study, Ixodes ovatus, which has been reported to harbour Spiroplasma ixodetis at high frequencies, was examined for its vertical transmission potential under experimental conditions. Next, two isolates of tick-derived Spiroplasma, S. ixodetis and Spiroplasma mirum, were experimentally inoculated into Spiroplasma-free Haemaphysalis longicornis colonies and the presence of Spiroplasma in their eggs and larvae was tested. Our experimental data confirmed that S. ixodetis was transmitted to eggs and larvae in a vertical manner in the original host I. ovatus. In the second experiment, there was no significant difference in engorged weight, egg weight, and hatching rate between Spiroplasma-inoculated and control H. longicornis groups. This suggested that Spiroplasma infection does not affect tick reproduction. Spiroplasma DNA was only detected in the eggs and larvae derived from some individuals of S. ixodetis-inoculated groups. This has demonstrated the potential of horizontal transmission between different tick species. These findings may help understand the transmission dynamics of Spiroplasma in nature and its adaptation mechanism to host arthropod species.

Comparative mitogenomics elucidates the population genetic structure of Amblyomma testudinarium in Japan and a closely related Amblyomma species in Myanmar.

Ticks are the second most important vector capable of transmitting diseases affecting the health of both humans and animals. Amblyomma testudinarium Koch 1844 (Acari: Ixodidae), is a hard tick species having a wide geographic distribution in Asia. In this study, we analyzed the composition of A. testudinarium whole mitogenomes from various geographical regions in Japan and investigated the population structure, demographic patterns, and phylogeographic relationship with other ixodid species. In addition, we characterized a potentially novel tick species closely related to A. testudinarium from Myanmar. Phylogeographic inference and evolutionary dynamics based on the 15 mitochondrial coding genes supported that A. testudinarium population in Japan is resolved into a star-like haplogroup and suggested a distinct population structure of A. testudinarium from Amami island in Kyushu region. Correlation analysis using Mantel test statistics showed that no significant correlation was observed between the genetic and geographic distances calculated between the A. testudinarium population from different localities in Japan. Finally, demographic analyses, including mismatch analysis and Tajima's D test, suggested a possibility of recent population expansion occurred within Japanese haplogroup after a bottleneck event. Although A. testudinarium has been considered widespread and common in East and Southeast Asia, the current study suggested that potentially several cryptic Amblyomma spp. closely related to A. testudinarium are present in Asia.

Identification, genetic variation, and structural analysis of 18S rRNA of Theileria orientalis and Theileria velifera-like isolates from Myanmar.

Ribosomal RNA genes have been widely used for the identification and phylogenetic analysis of various organisms, including parasitic protozoa. Here, we report nine near full-length Theileria orientalis 18S rRNA gene sequences from cattle from different areas of Myanmar. Phylogenetic analysis of the 18S rRNA genes revealed a considerably close genetic relationship among T. orientalis isolates from Australia, China, Japan, Korea, Myanmar, and Pakistan. We also obtained four Theileria velifera-like (Theileria cf. velifera) 18S rRNA gene sequences from two cattle and two water buffaloes from the northernmost area of Myanmar. The phylogenetic analysis of T. cf. velifera isolates from Myanmar along with T. velifera and T. cf. velifera isolates from African countries suggested an evolutionary lineage of greater complexity in T. velifera-related parasites. DNA alignment analysis indicated the presence of 51 and 55 nucleotide variation positions within the 18S rRNA genes from 15 T. orientalis and 11 T. velifera-related isolates, respectively. Alignment entropy analysis of the 18S rRNA sequences indicated that both T. orientalis and T. velifera-related isolates had three hyper variable regions, corresponding to V2, V4, and V7 regions in eukaryotes. The degree of variation was prominent in the V2 in T. orientalis and V4 in T. velifera-related isolates. The secondary structure analysis of the 18S rRNA predicted using minimum free energy algorism revealed that the structure of V4 region differed most significantly between T. orientalis and T. velifera. These results provide novel insights into common structures, variations and functions of small subunit rRNA in Theileria species.

First molecular detection of Theileria luwenshuni from goats in Myanmar.

Tick-borne intracellular protozoan parasites of the Theileria genus infect a wide range of both domestic and wild animals. In the present study, we describe the first PCR detection of Theileria luwenshuni in the blood of goats in Myanmar. Nested PCR targeting the Theileria 18S rRNA gene resulted in seven positive goats in central and northern Myanmar. Nucleotide sequencing of the PCR products revealed that all seven sequences were identical and showed 100% identity with T. luwenshuni sequences in GenBank from goats and sheep in China. Since T. luwenshuni parasites have recently been discovered and shown to have nationwide distribution in China, they might have been introduced into Myanmar via transboundary movement of infected domestic small ruminants and/or wild animals from China.