BackgroundClose relationships between ticks and microbial communities are important for tick fitness and pathogen colonization and transmission. Haemaphysalis longicornis, distributed widely in China, can carry and transmit various pathogens and pose serious damages to public health and economics. However, little is known about the broader array of microbial communities and symbionts in H. longicornis under natural conditions. In the present study, we investigated the composition of bacterial communities associated with H. longicornis and evaluated the putative symbionts.MethodsThe eubacterial 16S rRNA gene clone libraries of H. longicornis were constructed and analyzed by restriction fragment length polymorphism (RFLP) and DNA sequencing. In addition, diagnostic PCR was performed to assess the prevalence, vertical transmission and infection sites of the symbionts in H. longicornis.ResultsVertically-transmitted symbionts, potential pathogens and allochthonous nonpathogenic bacteria were identified from the field-collected H. longicornis. Three types of symbionts (Coxiella-like, Arsenophonus-like and Rickettsia-like symbionts) were identified in a single host simultaneously. A series of analyses revealed the vertical transmission, prevalence, and infection sites of these symbionts. However, only Coxiella-like bacteria were transmitted stably in the laboratory-reared ticks. In addition, we identified a novel Coxiella-like agent with 95.31% sequence similarity to the taxon described previously.ConclusionsThe present study demonstrated that natural H. longicornis harboured a diverse array of microbial communities. Three types of symbionts were identified in a single host simultaneously. Moreover, high prevalence, vertical transmission and the infection sites supported an obligate symbiotic association between Coxiella symbiont and its host. The role of Coxiella symbiont in the host fitness and the interaction among microbial communities remained to be elucidated. Our investigation of microbial communities in the ticks revealed the complexity of ecological interactions between host and microbe and provided insight for the biological control of ticks.

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We report that multiple symbionts coexist in Dermacentor silvarum. Based on 16S rRNA gene sequence analyses, we prove that Coxiella-like and Arsenophonus-like symbionts, with 95.6% and 96.7% sequence similarity to symbionts in the closest taxon, respectively, are novel. Moreover, we also provide evidence that the Coxiella-like symbiont appears to be the primary symbiont.

The paper investigated the life cycle of the hard tick Haemaphysalis doenitzi under laboratory conditions and its phylogeny based on mitochondrial 16S rDNA. The results revealed that the complete life cycle of H. doenitzi requires a mean duration of 109.6 days ranging from 91 to 137 days and the average prefeeding, feeding and premoulting periods of larvae, nymphs and females and the eggs hatching period are 18.7, 26.9, 38.9, and 25.1 days, respectively. In addition, the weight of engorged females is highly correlated with the number of egg masses laid (r = 0.936, P < 0.001). The female reproductive efficiency index and reproductive fitness index are 13.4 and 12.8, respectively. The mean weight of the engorged nymphs (2.77 mg) moulting to females is much higher than those (1.68 mg) moulting to males, which could be used as an index to predict sexes in this species. The ratio of male to female is 1:1.01. Moreover, multisequence alignments and phylogenetic tree constructed based on the mitochondrial 16S rDNA sequences suggest that H. doenitzi is genetically close to H. longicornis.

Rhipicephalus sanguineus (Latreille) is the most widely distributed tick species globally and plays a major role in tick-borne pathogen transmission among canine populations. The microbial community of this tick has not been characterized previously in Nigeria. Thus, in this study, the bacterial diversity in R. sanguineus collected from two states in Nigeria was explored using 16S rRNA high-throughput sequencing (IonS5TM XL sequencing platform). Three hundred genera (although 18 groups belong to unidentified genera) of bacteria belonging to 22 phyla were detected after pooling and sequencing, indicating a diverse bacterial community profile. At the phylum level, Actinobacteria (47.39%) was the most abundant phylum in the Benue state samples, followed by Proteobacteria (43.87%) and Firmicutes (8.21%), whereas Fusobacteria (38.14%) was the most abundant phylum in Plateau state samples, followed by Bacteroidetes (17.57%) and Firmicutes (17.54%). Proteobacteria accounts for 17% of samples from Plateau state. In general, Cetobacterium (35.86%) was the most abundant genus, followed by an unidentified genus under Corynebacteriaceae (29.94%) and Stenotrophomonas (19.52%). Coxiella spp., one common endosymbiont found in various tick species, was present in R. sanguineus. This study provides a baseline of knowledge of the bacterial microbiome of R. sanguineus in Nigeria. Nonpathogenic bacteria species were prevalent, and not much is known about their role. Thus, their composition, functional, and ecologic implications merit further investigation because this will aid in the subsequent management of ticks and tick-borne diseases.