Rickettsia africae infection rates and transovarial transmission in Amblyomma hebraeum ticks in Mnisi, Bushbuckridge, South Africa

Mazhetese, Estere; Lukanji, Zinathi; Byaruhanga, Charles; Neves, Luís; Morar-Leather, Darshana

doi:10.1007/s10493-022-00696-w

Cited by 9 publications

(6 citation statements)

References 33 publications

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“…S1 ). In concurrence with other studies, R. africae is found to be prevalent among cattle ticks (Pillay et al 2022 ) and occurs at a higher rate among larval tick population, inferring to possible transovarial maintenance of the species (Mazhetese et al 2022 ). Only a few other reports from China had a similar prevalence of R. africae among the Haemaphysalis tick population (Fig.…”

Section: Discussionsupporting

confidence: 89%

Rickettsia africae and other unclassified Rickettsia species of the spotted fever group in ticks of the Western Ghats, India

et al. 2023

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The spotted fever group (SFG) of Rickettsia are zoonotic disease-causing pathogens, commonly transmitted by hard ticks to a wide range of hosts, including humans. Rickettsia conorii is the common SFG recognised in India, whereas most of the infections due to other group species go undifferentiated at the species level. Hence, this study was conducted to screen host-seeking ticks in the Western Ghats region, India, for the DNA of SFG Rickettsia. The ticks were collected from Kerala, Goa, and Maharashtra states of India during a survey conducted between November 2017 and January 2018. In total, 288 tick pools were screened for Rickettsia spp. DNA using pan-Rickettsia real-time PCR, and conventional PCR targeting the gltA, OmpA and 17-kDa protein-coding genes. Nucleotide sequences were subjected to phylogenetic analysis using the NCBI BLAST tool to identify submitted sequences with higher homology. Neighbour-joining trees were constructed using the reference sequences of the GenBank database. Overall, Rickettsia spp. DNA was detected in 27.2% (62/228 pools) of host-seeking ticks across the Western Ghats region, with an estimated minimum infection rate of 0.057. Upon phylogenetic analysis, it was identified that the detected sequences were highly similar (> 99% sequence homology) to R. africae, Candidatus R. laoensis and an un-categorised Rickettsia species, and they were widely carried by Haemaphysalis ticks. The current study is the first report of R. africae and Candidatus R. laoensis in ticks in India. Although the pathogenicity of these species is not well documented, they may pose a potential threat to both animal and the human population in this geographical region.

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Section: Discussionsupporting

confidence: 89%

Rickettsia africae and other unclassified Rickettsia species of the spotted fever group in ticks of the Western Ghats, India

et al. 2023

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“…Within sub-Saharan Africa, Rickettsia species have been reported in Amblyomma, Hyalomma, and Rhipicephalus tick species, with Amblyomma and Hyalomma considered the principal vectors [13]. In our study, the overall MIR was 8.6%, which is within the prevalence range (3-77%) reported in other studies on ticks conducted in countries bordering Namibia [25][26][27][36][37][38][39][40], with the variability hypothesized to be due to factors such as ecological differences (biotic and abiotic) in different locations [41]. The detection of Rickettsia species in ticks from our study, coupled with the serological evidence of exposure to SFGR in humans [28] and molecular reports of the pathogen in hyenas [42], indicates the existence of transmission cycles of Rickettsia species in the country.…”

Section: Discussionsupporting

confidence: 82%

Molecular Detection and Characterization of Rickettsia Species in Ixodid Ticks from Selected Regions of Namibia

Mbiri,

Matomola,

Muleya

et al. 2024

Microorganisms

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Rickettsial pathogens are among the emerging and re-emerging vector-borne zoonoses of public health importance. Reports indicate human exposure to Rickettsial pathogens in Namibia through serological surveys, but there is a lack of data on infection rates in tick vectors, hindering the assessment of the relative risk to humans. Our study sought to screen Ixodid ticks collected from livestock for the presence of Rickettsia species in order to determine infection rates in ticks and to determine the Rickettsia species circulating in the country. We collected and pooled Hyalomma and Rhipicephalus ticks from two adjacent regions of Namibia (Khomas and Otjozondjupa) and observed an overall minimum Rickettsia infection rate of 8.6% (26/304), with an estimated overall pooled prevalence of 9.94% (95% CI: 6.5–14.3). There were no statistically significant differences in the estimated pooled prevalence between the two regions or tick genera. Based on the nucleotide sequence similarity and phylogenetic analysis of the outer membrane protein A (n = 9) and citrate synthase (n = 12) genes, BLAST analysis revealed similarity between Rickettsia africae (n = 2) and Rickettsia aeschlimannii (n = 11), with sequence identities ranging from 98.46 to 100%. Our initial study in Namibia indicates that both zoonotic R. africae and R. aeschlimannii are in circulation in the country, with R. aeschlimannii being the predominant species.

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“…Sample collection areas are shown in Figure 1 . For MP samples, DNA extracted from ticks collected in Utah and Welverdiend dip tanks was obtained by Mazhetese et al ( 2022 ). Ticks were collected from cattle in Moddergat and Geoderede-S dip tanks in MP.…”

Section: Methodsmentioning

confidence: 99%

Characterisation of South African field Ehrlichia ruminantium using multilocus sequence typing

Dlamkile,

Neves,

Morar-Leather

et al. 2023

Onderstepoort Journal of Veterinary Research

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Heartwater, one of the major tick-borne diseases of some domestic and wild ruminants in Africa, is caused by Ehrlichia ruminantium. The genetic diversity of E. ruminantium isolates renders the available vaccine ineffective against certain virulent isolates. To better understand the E. ruminantium genotypes in South Africa, a total of 1004 Amblyomma hebraeum tick deoxyribonucleic acid (DNA) samples from cattle in three South African provinces were tested by pCS20 Sol1 real-time polymerase chain reaction (qPCR) and characterised by multilocus sequence typing (MLST) using five housekeeping genes. Out of 1004 samples tested, 222 (22%) were positive for E. ruminantium. The occurrence of E. ruminantium in Mpumalanga, KwaZulu-Natal and Limpopo provinces was 19%, 22% and 27%, respectively. The E. ruminantium positive samples were screened for housekeeping genes and sequenced. Phylogenetic analysis revealed three main lineages: clade 1 made up of worldwide isolates (eastern, southern Africa, and Caribbean isolates), clade 2 comprised only West African isolates and clade 3 consisted of Omatjenne, Kümm2 and Riverside. Some study sample sequences were not identical to any of the reference isolates. However, they could all be grouped into the worldwide clade. Genetic variation in the sequenced regions was observed in the form of single nucleotide polymorphisms (SNPs). Using MLST to characterise E. ruminantium field isolates allowed the South African genotypes to be clearly distinguished from the distinct West African isolates.Contribution: Characterisation of E. ruminantium field isolates is important for the control of heartwater and contributes to preliminary knowledge required for the development of a more practical vaccine against heartwater.

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Rickettsia africae infection rates and transovarial transmission in Amblyomma hebraeum ticks in Mnisi, Bushbuckridge, South Africa

Cited by 9 publications

References 33 publications

Rickettsia africae and other unclassified Rickettsia species of the spotted fever group in ticks of the Western Ghats, India

Rickettsia africae and other unclassified Rickettsia species of the spotted fever group in ticks of the Western Ghats, India

Molecular Detection and Characterization of Rickettsia Species in Ixodid Ticks from Selected Regions of Namibia

Characterisation of South African field Ehrlichia ruminantium using multilocus sequence typing

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