Biotic Factors Influence Microbiota of Nymph Ticks from Vegetation in Sydney, Australia.

Shona Chandra,Jan Šlapeta

doi:10.3390/pathogens9070566

Abstract

Ticks are haematophagous ectoparasites of medical and veterinary significance due to their excellent vector capacity. Modern sequencing techniques enabled the rapid sequencing of bacterial pathogens and symbionts. This study’s aims were two-fold; to determine the nymph diversity in Sydney, and to determine whether external biotic factors affect the microbiota. Tick DNA was isolated, and the molecular identity was determined for nymphs at the cox1 level. The tick DNA was subjected to high throughput DNA sequencing to determine the bacterial profile and the impact of biotic factors on the microbiota. Four nymph tick species were recovered from Sydney, NSW: Haemaphysalis bancrofti, Ixodes holocyclus, Ixodes trichosuri and Ixodes tasmani. Biotic factors, notably tick species and geography, were found to have a significance influence on the microbiota. The microbial analyses revealed that Sydney ticks display a core microbiota. The dominating endosymbionts among all tick species were Candidatus Midichloria sp. Ixholo1 and Candidatus Midichloria sp. Ixholo2. A novel Candidatus Midichloria sp. OTU_2090 was only found in I. holocyclus ticks (nymph: 96.3%, adult: 75.6%). Candidatus Neoehrlichia australis and Candidatus Neoehrlichia arcana was recovered from I. holocyclus and one I. trichosuri nymph ticks. Borrelia spp. was absent from all ticks. This study has shown that nymph and adult ticks carry different bacteria, and a tick bite in Sydney, Australia will result in different bacterial transfer depending on tick life stage, tick species and geography.

Highlights

Ticks (Acari: Ixodida) are important vectors for diseases and the application of high throughputDNA sequencing enables the study of the bacterial symbionts, commensals and pathogenic microorganisms that ticks may carry
This study has shown that nymph and adult ticks carry different bacteria, and a tick bite in Sydney, Australia will result in different bacterial transfer depending on tick life stage, tick species and geography
We discovered there was no significant difference between the operational taxonomic unit (OTU) generated at either the DNA isolation method variable, or the hypervariable region selected (Supplementary Figure S1)

Summary

Introduction

Ticks (Acari: Ixodida) are important vectors for diseases and the application of high throughputDNA sequencing enables the study of the bacterial symbionts, commensals and pathogenic microorganisms that ticks may carry. There have been studies implementing NGS that look at ticks, but few that involved a comparison between questing ticks across at least two life stages [4,5,6,7]. Such studies have found that bacterial composition diversity differs with host species, geographic distribution and tick life stage [5,8]. In Australia, the most important tick in the medical and small animal veterinary context is the Australian paralysis tick Ixodes holocyclus Neumann, 1899. Found along the eastern coastline, I. holocyclus possesses a potent neurotoxin that causes fatal paralysis eventuating in death for many domestic animals, and can have a flaccid paralysis effect in humans, infants [9,10,11,12]

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