Rickettsia amblyommatis-infected Amblyomma coelebs parasitizing a human traveler in Rio Grande do Sul, southern Brazil, after returning from the Amazon

First isolation of Rickettsia amblyommatis from Amblyomma mixtum in Colombia

BACKGROUND

Rickettsiae are obligate intracellular Gram-negative bacteria that are the causative agent of rickettsioses and are spread to vertebrate hosts by arthropods. There are no previous reports of isolation of Rickettsia amblyommatis for Colombia.

METHODS

A convenience sampling was executed in three departments in Colombia for direct collection of adult ticks on domestic animals or over vegetation. Ticks were screened for the presence of Rickettsia spp. by real-time polymerase chain reaction (qPCR) amplifying the citrate synthase gene (gltA), and the positive sample was processed for isolation and further molecular characterization by conventional PCR. The absolute and relative frequencies were calculated for several tick species variables. All products from conventional PCR were further purified and sequenced by the Sanger technique. Representative sequences of 18 Rickettsia species were downloaded from GenBank. Consensus phylogenetic trees were constructed for the gltA, ompB, ompA, and htrA genes with 1000 replicates, calculating bootstrap values through the maximum likelihood method and the generalized time reversible substitution model in the MEGA 7.0 software program.

RESULTS

One female Amblyomma mixtum collected on vegetation was amplified by qPCR (gltA), indicating a frequency of 1.6% (1/61) for Rickettsia spp.

INFECTION

Sequence analysis of a rickettsial isolate from this tick in BLASTn showed 100% identity with gltA (340 base pairs [bp]), 99.87% for ompB (782 bp), 98.99% for htrA (497 bp), and 100% for ompA (488 bp) to R. amblyommatis. Concatenated phylogenetic analysis confirmed these findings indicating that the isolate is grouped with other sequences of Amblyomma cajennense complex from Panama and Brazil within the R. amblyommatis clade.

CONCLUSIONS

This paper describes the isolation and early molecular identification of a R. amblyommatis strain from A. mixtum in Colombia.

Diversity and phylogeny of the tick-borne bacterial genus Candidatus Allocryptoplasma (Anaplasmataceae)

The family Anaplasmataceae includes tick-borne bacteria of major public and veterinary health interest, as best illustrated by members of the genera Anaplasma and Ehrlichia. Recent epidemiological surveys have also reported on the presence of a novel putative genus in the Anaplasmataceae, Candidatus Allocryptoplasma, previously described as Candidatus Cryptoplasma in the western black-legged tick, Ixodes pacificus. However, the genetic diversity of Ca. Allocryptoplasma and its phylogenetic relationship with other Anaplasmataceae remain unclear. In this study, we developed a multi-locus sequence typing approach, examining the DNA sequence variation at five genes of Ca. Allocryptoplasma found in ticks. Combining this multi-locus sequence typing and genetic data available on public databases, we found that substantial genetic diversity of Ca. Allocryptoplasma is present in Ixodes, Amblyomma and Haemaphysalis spp. ticks on most continents. Further analyses confirmed that the Ca. Allocryptoplasma of ticks, the Ca. Allocryptoplasma of lizards and some Anaplasma-like bacteria of wild mice cluster into a monophyletic genus, divergent from all other genera of the family Anaplasmataceae. Candidatus Allocryptoplasma appears as a sister genus of Anaplasma and, with the genera Ehrlichia and Neoehrlichia, they form a monophyletic subgroup of Anaplasmataceae associated with tick-borne diseases. The detection of genetically distinct Ca. Allocryptoplasma in ticks of significant medical or veterinary interest supports the hypothesis that it is an emergent genus of tick-borne pathogens of general concern.

Soft and hard ticks (Parasitiformes: Ixodida) on humans: A review of Brazilian biomes and the impact of environmental change

Records of accidental parasitism by ticks in humans from Brazil are scarce, with most being reported by researchers who are parasitized during their research and by professionals who work with animals. In order to compile these records, an extensive literature review was carried out. Our revision includes studies published between 1909 and 2022, including nine species of the Argasidae family and 32 species of the Ixodidae family that were reported biting humans in the six biomes of the Brazilian territory. The species with the highest number of records of human parasitism was Amblyomma sculptum, followed by Amblyomma coelebs, Amblyomma cajennense sensu stricto, and Amblyomma brasiliense. The Atlantic Forest was the most frequent biome where human parasitism occurred, probably due to the greater number of inhabitants, universities, and researchers in the region; however, this does not mean that this biome is more conducive to the development of ticks and their parasitism in humans. In addition to Amblyomma ovale, a vector of Rickettsia parkeri in the country, two of the main species that act as vectors of Rickettsia rickettsii, A. sculptum, and Amblyomma aureolatum, have been reported, which is quite worrying considering that the wide distribution of the species and life stages most frequently mentioned in parasitism (i.e., nymphs and adults) are the ones that favour pathogen transmission. This research provides a significant contribution to the knowledge of tick species associated with human parasitism in Brazil; however, due to environmental change potentiated by deforestation and fires, it is expected that there will be a geographic expansion of some tick species and the pathogens that use them as a vector and an increase in human parasitism.

Spotted Fever Group Rickettsia spp. Diversity in Ticks and the First Report of Rickettsia hoogstraalii in Romania

Simple Summary

Ticks are important parasites that feed on the blood of various host species, representing the most important arthropods transmitting diseases in Europe. Continuous changes in both tick distribution and abundance are related to multiple factors, including climate change. These changes have strong implications for both animal and human health; therefore, continuous surveillance of tickborne diseases is required for an appropriate evaluation of the potential risks faced by animals and humans in a given area. The spotted fever group Rickettsia comprises a large number of zoonotic agents with an increasing importance recognized in the last 30 years. The aim of this study was to evaluate these bacteria in ticks in Romania. Five Rickettsia species were identified in different tick species, with new pathogen–tick associations reported. Rickettsia hoogstraalii, one member of this group, was detected for the first time in Romania and in Rhipicephalus rossicus ticks. This species was first described in 2006 in Croatia, and its pathogenicity is not well known. In addition, the detection of R. raoultii and R. monacensis in unfed larvae of Haemaphysalis punctata reinforce the hypothesis of transmission of Rickettsia from female ticks to larvae; therefore the bite of larvae could pose a health risk.

Abstract

Tickborne bacterial pathogens have been described worldwide as risk factors for both animal and human health. Spotted fevers caused by Rickettsiae may cause non-specific symptoms, which make clinical diagnosis difficult. The aim of the current study was to evaluate and review the diversity of SFG Rickettsiae in ticks collected in 41 counties in Romania. A total of 2028 questing and engorged ticks collected in Romania belonging to five species were tested by PCR amplification of Rickettsia spp. gltA and 17-D gene fragments: Ixodes ricinus (n = 1128), Dermacentor marginatus (n = 507), D. reticulatus (n = 165), Rhipicephalus rossicus (n = 128) and Haemaphysalis punctata (n = 100). Five Rickettsia species were identified following DNA sequence analysis: R. helvetica, R. monacensis, R. slovaca, R. raoultii, and R. hoogstraalii. The most common species detected was R. monacensis. Moreover, R. hoogstraalii was detected for the first time in Romania and in R. rossicus ticks. The detection of R. raoultii and R. monacensis in questing larvae of Hae. punctata suggests the possible transovarial transmission of these Rickettsia species in ticks. The detection of R. hoogstraalii for the first time in Romania increases the reported SFG Rickettsia diversity in the country.