An integrated overview of the bacterial flora composition of Hyalomma anatolicum, the main vector of CCHF

Another tick bites the dust: exploring the association of microbial composition with a broad transmission competence of tick vector species

IMPORTANCE

Some tick species are competent to transmit more than one pathogen while other species are, until now, known to be competent to transmit only one single or any pathogen. Such a difference in vector competence for one or more pathogens might be related to the microbiome, and understanding what differentiates these two groups of ticks could help us control several diseases aiming at the bacteria groups that contribute to such a broad vector competence. Using 16S rRNA from tick species that could be classified into these groups, genera such as Rickettsia and Staphylococcus seemed to be associated with such a broad vector competence. Our results highlight differences in tick species when they are divided based on the number of pathogens they are competent to transmit. These findings are the first step into understanding the relationship between one single tick species and the pathogens it transmits.

Metagenomics Characterization of Ixodes ricinus Intestinal Microbiota as Major Vector of Tick-Borne Diseases in Domestic Animals

Background

Understanding the microbiota of disease vectors can help for developing new strategies to prevent the transmission of vector pathogens. Ixodes ricinus is one of the most notorious tick vectors with increasing importance in Iran and other parts of the world while there is limited data on its microbiota. This study aimed to use metagenomics for identifying the I. ricinus tick's microbiota of Iran.

Methods

A total of 39 adult ticks were collected from Mazandaran (21 females), Gilan (17 females), and Golestan (1 male). Five tick pools prepared from 39 adults of I. ricinus were subjected to metagenomics analysis. The data were analyzed by targeting the V6 region of the 16S rRNA gene by Illumina 4000 Hiseq sequencing.

Results

Among hundreds of intestinal microbiota identified by metagenomics, various pathogenic microorganisms distributed in 30 genera and species including those responsible for tick-borne diseases resided in the genera Coxiella, Rickettsia, and Burkholderia were found.

Conclusion

Our results indicated that metagenomics identifies bacteria genera and species which cannot be easily recognized by routine methods. The presence of such pathogenic bacteria indicates the importance of possible zoonotic diseases in this region which could affect public health. These results further substantiate the importance of advanced metagenomics analyses to identify neglected tick-borne pathogens which enable researchers to provide efficient mapping roads for the management of emerging and re-emerging infectious diseases.

The Impact of RNA Interference in Tick Research

Over the past two decades, RNA interference (RNAi) in ticks, in combination with omics technologies, have greatly advanced the discovery of tick gene and molecular function. While mechanisms of RNAi were initially elucidated in plants, fungi, and nematodes, the classic 2002 study by Aljamali et al. was the first to demonstrate RNAi gene silencing in ticks. Subsequently, applications of RNAi have led to the discovery of genes that impact tick function and tick-host-pathogen interactions. RNAi will continue to lead to the discovery of an array of tick genes and molecules suitable for the development of vaccines and/or pharmacologic approaches for tick control and the prevention of pathogen transmission.

Comparative analysis of the gut microbiota of sand fly vectors of zoonotic visceral leishmaniasis (ZVL) in Iran; host-environment interplay shapes diversity

The development of Leishmania parasites within sand fly vectors occurs entirely in the insect gut lumen, in the presence of symbiotic and commensal bacteria. The impacts of host species and environment on the gut microbiome are currently poorly understood. We employed MiSeq sequencing of the V3-16S rRNA gene amplicons to characterize and compare the gut microbiota of field-collected populations of Phlebotomus kandelakii, P. perfiliewi, P. alexandri, and P. major, the primary or secondary vectors of zoonotic visceral leishmaniasis (ZVL) in three distinct regions of Iran where ZVL is endemic. In total, 160,550 quality-filtered reads of the V3 region yielded a total of 72 operational taxonomic units (OTUs), belonging to 23 phyla, 47 classes, 91 orders, 131 families, and 335 genera. More than 50% of the bacteria identified were Proteobacteria, followed by Firmicutes (22%), Deinococcus-Thermus (9%), Actinobacteria (6%), and Bacteroidetes (5%). The core microbiome was dominated by eight genera: Acinetobacter, Streptococcus, Enterococcus, Staphylococcus, Bacillus, Propionibacterium, Kocuria, and Corynebacterium. Wolbachia were found in P. alexandri and P. perfiliewi, while Asaia sp. was reported in P. perfiliewi. Substantial variations in the gut bacterial composition were found between geographically distinct populations of the same sand fly species, as well as between different species at the same location, suggesting that sand fly gut microbiota is shaped by both the host species and geographical location. Phlebotomus kandelakii and P. perfiliewi in the northwest, and P. alexandri in the south, the major ZVL vectors, harbor the highest bacterial diversity, suggesting a possible relationship between microbiome diversity and the capacity for parasite transmission. In addition, large numbers of gram-positive human or animal pathogens were found, suggesting that sand fly vectors of ZVL could pose a potential additional threat to livestock and humans in the region studied. The presence of Bacillus subtilis, Enterobacter cloacae, and Asaia sp suggests that these bacteria could be promising candidates for a paratransgenesis approach to the fight against Leishmaniasis.

Leishmania infantum, a parasitic protozoan causing fatal visceral leishmaniasis, is transmitted to humans by several sand fly vectors. In this study, the microbiota within the midguts of Phlebotomus kandelakii, P. perfiliewi, P. major and P. alexandri was analyzed by 16S ribosomal DNA (rDNA) Miseq sequencing, revealing highly diverse community composition and abundance, from three diverse ecological and geographical regions of Iran. It appears that the gut microbiota is highly dynamic and controlled by multiple factors, including sand fly host and environment. Proteobacteria were the principal bacterial phylum isolated. High numbers of gram-positive human or animal pathogens were also found, suggesting that sand fly vectors of ZVL could pose a potential threat to livestock and human in the region. Furthermore, there was a positive correlation between vector capacity and bacterial diversities, where the weakest ZVL vector had the lowest diversity, whereas other, more efficient, vectors had higher diversity. This study showed that Bacillus subtilis, Asaia sp. and Enterobacter cloacae are possible candidates for a paratransgenic approach to reduce Leishmania transmission.

Characterization and manipulation of the bacterial community in the midgut of Ixodes ricinus

Background

Ticks are obligate hematophagous arthropods transmitting a wide range of pathogens to humans and animals. They also harbor a non-pathogenic microbiota, primarily in the ovaries and the midgut. In the previous study on Ixodes ricinus, we used a culture-independent approach and showed a diverse but quantitatively poor midgut bacterial microbiome. Our analysis also revealed the absence of a core microbiome, suggesting an environmental origin of the tick midgut microbiota.

Methods

A bacterial analysis of the midgut of adult females collected by flagging from two localities in the Czech Republic was performed. Using the culture-independent approach, we tested the hypothesis that the midgut microbiome is of the environmental origin. We also cultured indigenous bacteria from the tick midgut and used these to feed ticks artificially in an attempt to manipulate the midgut microbiome.

Results

The midgut showed a very low prevalence and abundance of culturable bacteria, with only 37% of ticks positive for bacteria. The culture-independent approach revealed the presence of Borrelia sp., Spiroplasma sp., Rickettsia sp., Midichloria sp. and various mainly environmental Gram-positive bacterial taxa. The comparison of ticks from two regions revealed that the habitat influenced the midgut bacterial diversity. In addition, the midgut of ticks capillary fed with the indigenous Micrococcus luteus (Gram-positive) and Pantoea sp. (Gram-negative) could not be colonized due to rapid and effective clearance of both bacterial taxa.

Conclusions

The midgut microbiome of I. ricinus is diverse but low in abundance, with the exception of tick-borne pathogens and symbionts. The environment impacts the diversity of the tick midgut microbiome. Ingested extracellular environmental bacteria are rapidly eliminated and are not able to colonize the gut. We hypothesize that bacterial elimination triggered in the midgut of unfed adult females is critical to maintain low microbial levels during blood-feeding.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05362-z.

Microbial composition in Hyalomma anatolicum collected from livestock in the United Arab Emirates using next-generation sequencing

BACKGROUND

Hyalomma anatolicum is a widely distributed tick species that acts as a vector transmitting tick-borne pathogens (TBPs) in livestock. Such pathogens affect the health of livestock and consequently reduce their productivity. Knowledge about the microbial communities (pathogens and endosymbionts) of ticks in the United Arab Emirates (UAE) is scarce. Therefore, the aim of the present study was to quantify microbial diversity in H. anatolicum using next-generation sequencing (NGS) technology.

METHODS

Hyalomma anatolicum ticks were collected from livestock in the emirates of Abu Dhabi, Dubai and Sharjah in the UAE during 2019. DNA was extracted from 175 male ticks sampled from livestock (n = 78) and subjected to NGS. The 16S rRNA gene was analyzed using the Illumina MiSeq platform to determine the bacterial communities. Principal coordinates analysis (PCA) was performed to identify patterns of diversity in the bacterial communities.

RESULTS

Twenty-six bacterial families with high relative abundance were identified, of which the most common were Staphylococcaceae, Francisellaceae, Corynebacteriaceae, Enterobacteriaceae, Moraxellaceae, Bacillaceae, Halomonadaceae, Xanthomonadaceae, Pseudomonadaceae, Enterococcaceae, Actinomycetaceae and Streptococcaceae. The diversity of the microbial communities in terms of richness and evenness was different at the three study locations, with the PCA showing clear clusters separating the microbial communities in ticks collected at Abu Dhabi, Dubai, and Sharjah. The presence of bacterial families harboring pathogenic genera showed that H. anatolicum could pose a potential threat to livestock and food security in the UAE.

CONCLUSIONS

The study is the first to document important data on the microbial communities associated with H. anatolicum in the UAE. This knowledge will facilitate a better understanding of the distribution pattern of microbes in livestock ticks in the UAE and, ultimately, will aid in deciphering the relationships between microbes and in the exploration of potential factors towards developing effective management strategies.

Prevalence, Distribution, and Molecular Record of Four Hard Ticks from Livestock in the United Arab Emirates

Simple Summary

Ticks, as blood feeders and vectors of many diseases, can negatively impact livestock and human health, with potential economic impacts on the livestock industry. In this study, we documented the occurrence of four tick species (Hyalomma dromedarii, Hyalomma anatolicum, Rhipicephalus sanguineus, and Amblyomma lepidum) on camels, cows, sheep, and goats from three areas in the United Arab Emirates (UAE). Our findings indicated that H. dromedarii was the most prevalent tick species on camels. The other tick species were present at varying levels on hosts. Some of the tick species collected in this study are potential carriers of tick-borne diseases that are serious and sometimes fatal to humans and animals. Thus, there is a need for more research on ticks and tick-borne diseases in the UAE.

Abstract

Ticks are important arthropod vectors that serve as reservoirs of pathogens. Rapid urbanization and changes in animal breeding practices could be causing a rise in tick burden on animals. Studies on tick distribution on livestock and tick molecular diversity from the United Arab Emirates (UAE) are limited. The aim of this study was to (i) provide molecular and morphological identification of tick species, (ii) compare tick infestation between different hosts, (iii) compare tick infestation in relation to the sex of the host, and (iv) assess the prevalence of tick species on hosts. A total of 5950 ticks were collected from camels (4803 ticks), cows (651 ticks), goats (219 ticks), and sheep (277 ticks). Ticks were identified based on morphological characters at the species level using taxonomic keys. In addition, Polymerase Chain Reaction (PCR) amplification of the cytochrome oxidase subunit 1 (cox1) and 16S rRNA mitochondrial genes was used to identify ticks. Four species were confirmed based on molecular and morphological characterization, namely, Hyalomma dromedarii, Hyalomma anatolicum, Rhipicephalus sanguineus, and Amblyomma lepidum. Hyalomma dromedarii (94.3%) was the most abundant species, followed by H. anatolicum (32.8%). Camels were heavily infested (94%) with ticks as compared to cows (38%), sheep (37%), and goats (14%). Widespread occurrence of these four tick species in the UAE poses a risk of spreading tick-borne pathogens wherever the conditions of infection prevail.

Hyalomma spp. ticks and associated Anaplasma spp. and Ehrlichia spp. on the Iran-Pakistan border

Background

Anaplasmosis and ehrlichiosis are tick-borne diseases affecting humans and livestock, particularly in tropical and subtropical regions. Animal husbandry is the main activity of people on the borders of Iran and Pakistan, with thousands of cattle crossing the border each week.

Methods

PCR and sequencing of the 16S rRNA gene was used to determine the percentage and geographical distribution of the pathogens carried by Hyalomma spp. (n = 306) collected from 126 goats, cattle and camels in the region between November 2017 and late March 2018.

Results

In total, 1124 hard ticks including 1020 Hyalomma spp. ticks belonging to six species (Hyalomma anatolicum, Hyalomma asiaticum, Hyalomma marginatum, Hyalomma dromedarii, Hyalomma schulzei, and Hyalomma detritum) were found on the borders of Iran and Pakistan, with H. anatolicum being the most prevalent tick species. Anaplasma spp. and/or Ehrlichia spp. DNA was found in 68.3% of the engorged tick specimens (n = 256). Sequencing of a subset (12.6%) of PCR-positive samples revealed Anaplasma ovis, Anaplasma marginale, and Ehrlichia ewingii DNA in 81.8%, 9.1%, and 9.1% of the ticks, respectively. To our knowledge, this is the first report of E. ewingii, an important human pathogen, in Iran.

Conclusions

Based on molecular analysis, three pathogenic Anaplasmataceae were detected in six Hyalomma spp. parasitizing cattle, goats and camels, confirming the presence of these pathogens along the Iran-Pakistan border.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04956-3.