Rickettsial infections: A blind spot in our view of neglected tropical diseases

Salje, Jeanne; Weitzel, Thomas; Newton, Paul N.; Varghese, George M.; Npj., Day

doi:10.1371/journal.pntd.0009353

Cited by 43 publications

(43 citation statements)

References 24 publications

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“…In addition to transovarial transmission of R. conorii in ticks, domestic dogs are competent reservoirs of R. conorii which can further raise pathogen prevalence in ticks [ 118 ]. Rickettsia conorii and other members of the SFG Rickettsia are overlooked human pathogens that can persist in human dominated landscapes and cause morbidity, mortality, and economic losses in marginalized populations [ 119 ]. Comprehensive surveillance of SFG Rickettsia in vectors, humans, and animals from endemic areas is needed to inform public health priorities.…”

Section: Discussionmentioning

confidence: 99%

Survey of Ticks and Tick-Borne Rickettsial and Protozoan Pathogens in Eswatini

Ledger

Béati

2021

Pathogens

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Ticks are widespread parasites of vertebrates and major vectors of pathogens to humans, domestic animals, and wildlife. In southern Africa, numerous tick species transmit diseases of economic and health importance. This study aimed to describe the occurrence of ticks and tick-borne pathogens in multiple land-use types and the possible role of ticks in the transmission of pathogen species. Using molecular techniques, we screened 1716 ticks for infection by rickettsial bacteria and protozoans. To characterize pathogen identity, we sequenced multiple loci from positive samples and analyzed sequences within a phylogenetic framework. Across the seven tick species collected as nymphs or adults, we detected Rickettsia, Anaplasma, Ehrlichia, Babesia, Hepatozoon, and Theileira species. We found that some tick species and tick-borne pathogens differed according to land use. For example, we found a higher density of Haemaphysalis elliptica and higher prevalence of Rickettsia in H. elliptica collected from savanna grasses used for livestock grazing near human settlements than savanna grasses in conservation areas. These findings highlight the importance of comprehensive surveillance to achieve a full understanding of the diversity and ecology of the tick-borne pathogens that can infect humans, domestic animals, and wildlife.

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Section: Discussionmentioning

confidence: 99%

Survey of Ticks and Tick-Borne Rickettsial and Protozoan Pathogens in Eswatini

Ledger

Béati

2021

Pathogens

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“…The combined limitations of current serological and molecular diagnostics mean that diagnosis in the acute phase remains elusive, and empirical treatment is often given without any subsequent confirmation of diagnosis. The challenges in diagnosis perpetuate the neglected nature of rickettsial infections-without confirmation of cases, the true burden of disease is underestimated, leading to lack of development in diagnostics and ongoing under appreciation of clinical significance [ 14 ].…”

Section: Current Challenges In Diagnosismentioning

confidence: 99%

“…Rickettsial infections are an important cause of undifferentiated febrile illness in endemic settings but are frequently unrecognised [ 10 , 11 , 12 ]. Fever and seroprevalence studies have demonstrated a significant burden of rickettsial disease globally [ 13 ]; however, they remain a neglected disease [ 14 ].…”

Section: Introductionmentioning

confidence: 99%

An Update on the Laboratory Diagnosis of Rickettsia spp. Infection

Stewart

2021

Pathogens

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Rickettsia species causing human illness are present globally and can cause significant disease. Diagnosis and identification of this intracellular bacteria are challenging with many available diagnostic modalities suffering from several shortcomings. Detection of antibodies directed against Rickettsia spp. via serological methods remains widely used with a broad range of sensitivity and specificity values reported depending on the assay. Molecular methods, including polymerase chain reaction (PCR) testing, enables species-specific identification with a fast turnaround time; however, due to resource requirements, use in some endemic settings is limited. Reports on the use of next-generation sequencing (NGS) and metagenomics to diagnose Rickettsia spp. infection have been increasing. Despite offering several potential advantages in the diagnosis and surveillance of disease, genomic approaches are currently only limited to reference and research laboratories. Continued development of Rickettsia spp. diagnostics is required to improve disease detection and epidemiological surveillance, and to better understand transmission dynamics.

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“…Rickettsial diseases are prevalent in tropical and subtropical regions of the world and disproportionately affect those living in poverty with limited access to modern health care [ 2 ]. For decades, rickettsial diseases have been an overlooked cause of morbidity, mortality, and economic losses in marginalized populations [ 3 ]. Despite the increasing awareness of the importance of rickettsial diseases, there remains a lack of information on the prevalence of rickettsiae in vector species across all infective life stages.…”

Section: Introductionmentioning

confidence: 99%

Entomological risk of African tick-bite fever (Rickettsia africae infection) in Eswatini

et al. 2022

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Background Rickettsia africae is a tick-borne bacterium that causes African tick-bite fever (ATBF) in humans. In southern Africa, the tick Amblyomma hebraeum serves as the primary vector and reservoir for R. africae and transmits the bacterium during any life stage. Previous research has shown that even when malaria has been dramatically reduced, unexplained acute febrile illnesses persist and may be explained by the serological evidence of rickettsiae in humans. Methodology/Principal findings We collected 12,711 questing Amblyomma larvae across multiple land use types in a savanna landscape in Eswatini. Our results show that host-seeking Amblyomma larvae are abundant across both space and time, with no significant difference in density by land use or season. We investigated the entomological risk (density of infected larvae) of ATBF from A. hebraeum larvae by testing over 1,600 individual larvae for the presence of R. africae using a novel multiplex qPCR assay. We found an infection prevalence of 64.9% (95% CI: 62.1–67.6%) with no land use type significantly impacting prevalence during the dry season of 2018. The mean density of infected larvae was 57.3 individuals per 100m2 (95% CI: 49–65 individuals per 100m2). Conclusions Collectively, our results demonstrate R. africae infected A. hebraeum larvae, the most common tick species and life stage to bite humans in southern Africa, are ubiquitous in the savanna landscape of this region. Increased awareness of rickettsial diseases is warranted for policymakers, scientists, clinicians, and patients. Early detection of disease via increased clinician awareness and rapid diagnostics will improve patient outcomes for travelers and residents of this region.

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Rickettsial infections: A blind spot in our view of neglected tropical diseases

Cited by 43 publications

References 24 publications

Survey of Ticks and Tick-Borne Rickettsial and Protozoan Pathogens in Eswatini

Survey of Ticks and Tick-Borne Rickettsial and Protozoan Pathogens in Eswatini

An Update on the Laboratory Diagnosis of Rickettsia spp. Infection

Entomological risk of African tick-bite fever (Rickettsia africae infection) in Eswatini

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