Transmission Of Rickettsia Research Articles

Rickettsia symbionts spread via mixed mode transmission, increasing female fecundity and sex ratio shift by host hormone modulating

Heritable symbionts are common among animals in nature, but the molecular mechanisms underpinning symbiont invasions of host populations have been elusive. In this study, we demonstrate the spread of Rickettsia in an invasive agricultural pest, the whitefly Bemisia tabaci Mediterranean (MED), across northeastern China from 2018 to 2023. Here, we show that the beneficial symbiont Rickettsia spreads by manipulating host hormone signals. Our analyses suggest that Rickettsia have been horizontally acquired by B. tabaci MED from another invasive whitefly B. tabaci Middle East-Asia Minor 1 during periods of coexistence. Rickettsia is transmitted maternally and horizontally from female B. tabaci MED individuals. Rickettsia infection enhances fecundity and results in female bias among whiteflies. Our findings reveal that Rickettsia infection stimulates juvenile hormone (JH) synthesis, in turn enhancing fecundity, copulation events, and the female ratio of the offspring. Consequently, Rickettsia infection results in increased whitefly fecundity and female bias by modulating the JH pathway. More female progeny facilitates the transmission of Rickettsia. This study illustrates that the spread of Rickettsia among invasive whiteflies in northeastern China is propelled by host hormone regulation. Such symbiont invasions lead to rapid physiological and molecular evolution in the host, influencing the biology and ecology of an invasive species.

Serological detection of Rickettsia spp. and evaluation of blood parameters in pet dogs and cats from Bangkok and neighboring provinces.

Rickettsiosis is caused by Orientia spp. and Rickettsia spp., arthropod-borne zoonotic intracellular bacteria. The close relationships between pet dogs, cats and owners increase the risk of rickettsial transmission, with limited studies on the seroprevalence in pets. This study investigated the prevalence of rickettsia exposure among dogs and cats in Bangkok and neighboring provinces. The samples from 367 dogs and 187 cats used in this study were leftover serum samples from routine laboratory testing stored at the Veterinary Teaching Hospital. In-house Enzyme-linked immunosorbent assay (ELISA) tests included IgG against the scrub typhus group (STG), typhus group (TG), and spotted fever group (SFG). The seroprevalence in pet dogs was 30.25% (111/367), including 21.53% for STG, 4.36% for TG, and 1.09% for SFG. Co-seroprevalence consisted of 2.72% for STG and TG, 0.27% for STG and SFG, and 0.27% for pangroup infection. The prevalence in cats was 62.56% (117/187), including 28.34% for STG, 4.28% for TG, and 6.42% for STG. Co-seroprevalence in cats consisted of STG and TG (4.28%), STG and SFG (5.35%), TG and SFG (3.21%), and three-group infection (10.69%). No significant difference in seroprevalence for the three serogroups was observed in any of the 64 districts sampled. The mean hematocrit level significantly decreased in seropositive dogs (P<0.05). Seropositive dogs and cats were detected in significantly greater numbers of anemia cases than nonanemia cases (P<0.05) (odds ratio: 7.93, 0.44, p = 0.00, p = 0.01). A significantly higher number of seropositive cats had decreased hemoglobin levels (P<0.05) (odds ratio: 3.63, p = 0.00). The seropositive samples significantly differed among older cats (P<0.05). These high exposures in pet dogs and cats could constitute important relationship dynamics between companion animals and rickettsial vectors. Significantly decreased hematocrit and hemoglobin levels indicated anemia in the exposed dogs and cats. The study findings will raise awareness of this neglected disease among pet owners and veterinary hospital personnel and aid in future public health preventative planning.

Rickettsia transmission from whitefly to plants benefits herbivore insects but is detrimental to fungal and viral pathogens.

Most insects are associated with symbiotic bacteria in nature. These symbionts play important roles in the life histories of herbivorous insects by impacting their development, survival, reproduction as well as stress tolerance. Rickettsia is one important symbiont to the agricultural pest whitefly Bemisia tabaci. Here, for the first time, we revealed that the persistence of Rickettsia symbionts in tomato leaves significantly changed the defense pattern of tomato plants. These changes benefit both sap-feeding and leaf-chewing herbivore insects, such as increasing the fecundity of whitefly adults, enhancing the growth and development of the noctuid Spodoptera litura, but reducing the pathogenicity of Verticillium fungi and TYLCV virus to tomato plants distinctively. Our study unraveled a new horizon for the multiple interaction theories among plant-insect-bacterial symbionts.

Spotted Fever and Typhus Group Rickettsiae in Dogs and Humans, Mexico, 2022.

We found serologic evidence of spotted fever group Rickettsia in humans and dogs and typhus group Rickettsia in dogs in Reynosa, Mexico. Our investigation revealed serologic samples reactive to spotted fever group Rickettsia in 5 community members, which highlights a potential rickettsial transmission scenario in this region.

Parasitoid-mediated horizontal transmission of Rickettsia between whiteflies.

Intracellular bacterial endosymbionts of arthropods are mainly transmitted vertically from mother to offspring, but phylogenetically distant insect hosts often harbor identical endosymbionts, indicating that horizontal transmission from one species to another occurs in nature. Here, we investigated the parasitoid Encarsia formosa-mediated horizontal transmission of the endosymbiont Rickettsia between different populations of whitefly Bemisia tabaci MEAM1. Rickettsia was successfully transmitted from the positive MEAM1 nymphs (R +) into E. formosa and retained at least for 48h in E. formosa adults. Fluorescence in situ hybridization (FISH) visualization results revealed that the ovipositors, mouthparts, and digestive tract of parasitoid adults get contaminated with Rickettsia. Random non-lethal probing of Rickettisia-negative (R- ) MEAM1 nymphs by these Rickettsia-carrying E. formosa resulted in newly infected MEAM1 nymphs, and the vertical transmission of Rickettsia within the recipient females can remain at least up to F3 generation. Further phylogenetic analyses revealed that Rickettsia had high fidelity during the horizontal transmission in whiteflies and parasitoids. Our findings may help to explain why Rickettsia bacteria are so abundant in arthropods and suggest that, in some insect species that shared the same parasitoids, Rickettsia may be maintained in populations by horizontal transmission.

Evaluating the Clinical and Immune Responses to Spotted Fever Rickettsioses in the Guinea Pig-Tick-Rickettsia System.

The guinea pig was the original animal model developed for investigating spotted fever rickettsiosis (SFR). This model system has persisted on account of the guinea pig's conduciveness to tick transmission of SFR agents and ability to recapitulate SFR in humans through clinical signs that include fever, unthriftiness, and in some cases the development of an eschar. The guinea pig is the smallest animal model for SFR that allows the collection of multiple blood and skin samples antemortem for longitudinal studies. This unit provides the basic protocols necessary to establish, maintain, and utilize a guinea pig-tick-Rickettsia model for monitoring the course of infection and immune response to an infection by spotted fever group Rickettsia (SFGR) that can be studied at biosafety level 2 (BSL-2) and arthropod containment level 2 (ACL-2); adaptations must be made for BSL-3 agents. The protocols cover methods for tick feeding and colony development, laboratory infection of ticks, tick transmission of Rickettsia to guinea pigs, and monitoring of the course of infection through clinical signs, rickettsial burden, and immune response. It should be feasible to adapt these methods to study other tick-borne pathogens. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Tick transmission of SFGR to guinea pigs Support Protocol 1: Laboratory infection of ticks by injection Alternate Protocol 1: Needle inoculation of SFGR to guinea pigs Basic Protocol 2: Monitoring the course of guinea pig rickettsial infection: clinical signs Basic Protocol 3: Monitoring the course of guinea pig rickettsial infection: collection of biological specimens Support Protocol 2: Guinea pig anesthesia Basic Protocol 4: Monitoring rickettsial burden in guinea pigs by multiplex qPCR Basic Protocol 5: Monitoring guinea pig immune response to infection: blood leukocytes by flow cytometry Basic Protocol 6: Monitoring immune response to guinea pig rickettsial infection: leukocyte infiltration of skin at the tick bite site by flow cytometry Basic Protocol 7: Monitoring the immune response to guinea pig rickettsial infection: antibody titer by ELISA Support Protocol 4: Coating ELISA Plates Alternate Protocol 2: Monitoring immune response to guinea pig rickettsial infection: antibody titer by immunofluorescence assay.

Unraveling the epidemiological relationship between ticks and rickettsial infection in Africa

Tick-borne rickettsioses are emerging and re-emerging diseases of public health concern caused by over 30 species ofRickettsia. Ticks are obligate hematophagous arthropods with over 700 species of Ixodid ticks known worldwide. The escalating geographical dispersal of tick vectors and concomitant increase in the incidences of tick-borne diseases have fueled interest in the ecology of tick-borne pathogens. This review focuses on aspects of theRickettsiapathogen, including biology, taxonomy, phylogeny, genetic diversity, epidemiology of the disease, and the role of vertebrate host in the perpetuation of rickettsioses in Africa. Our review also highlights some of the species ofRickettsiathat are responsible for disease, the role of tick vectors (both hard and soft ticks) and the species ofRickettsiaassociated with diverse tick species across the continent. Additionally, this article emphasizes the evolutionary perspective of rickettsiae perpetuation and the possible role of amplifying vertebrate host and other small mammals, domestic animals and wildlife in the epidemiology ofRickettsiaspecies. We also specifically, discussed the role of avian population in the epidemiology of SFG rickettsiae. Furthermore, we highlighted tick-borne rickettsioses among travelers due to African tick-bite fever (ATBF) and the challenges to surveillance of rickettsial infection, and research on rickettsiology in Africa. Our review canvasses the need for more rickettsiologists of African origin based within the continent to further research towards understanding the biology, characterization, and species distribution, including the competent tick vectors involved in their transmission of rickettsiae across the continent in collaboration with established researchers in western countries. We further highlighted the need for proper funding to encourage research despite competing demands for resources across the various sectors. We finalize by discussing the similarities between rickettsial diseases around the world and which steps need to be taken to help foster our understanding on the eco-epidemiology of rickettsioses by bridging the gap between the growing epidemiological data and the molecular characterization ofRickettsiaspecies.

Rickettsia massiliae circulation in sheep and attached Rhipicephalus sanguineus in Central Portugal.

Rickettsiosis is considered an emerging/re-emerging vector-borne disease that causes significant public health threats. Ticks are reservoirs and vectors of Rickettsia having a significant role in the transmission of rickettsiae. In Portugal, little is known about tick-borne Rickettsia species in sheep. Therefore, this study aimed to investigate rickettsiae infection in ticks and their sheep host from 27 farms in four districts of central Portugal, to clarify the role of the sheep host in the circulation of this zoonotic agent. Between March and May 2021, EDTA blood samples (n = 100) of healthy grazing sheep and their ticks (n = 100, one tick per animal) were collected during a herd health program in central Portugal. Obtained ticks were identified as Rhipicephalus sanguineus sensu lato by PCR targeting a partial sequence of 16S rRNA gene followed by sequence analysis. Rhipicephalus sanguineus s.l. and host sheep blood were tested for the presence of Rickettsia spp. by PCR targeting a partial sequence of ompB and ompA genes. From a total of 100 paired R. sanguineus s.l. and host sheep, Rickettsia massiliae was detected in 62 ticks and 35 grazing sheep blood samples, collected in central Portugal, 2021. All 35 positive sheep had attached positive R. sanguineus s.l., with matching nucleotidic sequences. These findings suggest that sheep may develop rickettsiemia and are likely capable of transmitting and amplifying the infection to uninfected ticks maintaining rickettsiae in circulation in the domestic cycle.

Carios kelleyi (Acari: Ixodida: Argasidae) Infected With Rickettsial Agents Documented Infesting Housing in Kansas, United States.

During September-December 2018, 25 live ticks were collected on-post at Fort Leavenworth, Kansas, in a home with a history of bat occupancy. Nine ticks were sent to the Army Public Health Center Tick-Borne Disease Laboratory and were identified as Carios kelleyi (Cooley and Kohls, 1941), a species that seldom bites humans but that may search for other sources of blood meals, including humans, when bats are removed from human dwellings. The ticks were tested for numerous agents of human disease. Rickettsia lusitaniae was identified by multilocus sequence typing to be present in two ticks, marking the first detection of this Rickettsia agent in the United States and in this species of tick. Two other Rickettsia spp. were also detected, including an endosymbiont previously associated with C. kelleyi and a possible novel Rickettsia species. The potential roles of C. kelleyi and bats in peridomestic Rickettsia transmission cycles warrant further investigation.

Dynamic gene expression in salivary glands of the cat flea during Rickettsia felis infection.

ABSTRACTThe cat flea, Ctenocephalides felis, is an arthropod vector capable of transmitting several human pathogens including Rickettsia species. Earlier studies identified Rickettsia felis in the salivary glands of the cat flea and transmission of rickettsiae during arthropod feeding. The saliva of hematophagous insects contains multiple biomolecules with anticlotting, vasodilatory and immunomodulatory activities. Notably, the exact role of salivary factors in the molecular interaction between flea-borne rickettsiae and their insect host is still largely unknown. To determine if R. felis modulates gene expression in the cat flea salivary glands, cat fleas were infected with R. felis and transcription patterns of selected salivary gland-derived factors, including antimicrobial peptides and flea-specific antigens, were assessed. Salivary glands were microdissected from infected and control cat fleas at different time points after exposure and total RNA was extracted and subjected to reverse-transcriptase quantitative PCR for gene expression analysis. During the experimental 10-day feeding period, a dynamic change in gene expression of immunity-related transcripts and salivary antigens between the two experimental groups was detected. The data indicated that defensin-2 (Cf-726), glycine-rich antimicrobial peptide (Cf-83), salivary antigens (Cf-169 and Cf-65) and deorphanized peptide (Cf-75) are flea-derived factors responsive to rickettsial infection.

Spotted fever group rickettsiae transmitted by Dermacentor ticks and determinants of their spread in Europe.

Rickettsiae from the spotted fever group, i.e. the etiological agents of tick-borne lymphadenopathy/Dermacentor-borne necrotic erythema and lymphadenopathy (TIBOLA /DEBONEL) syndrome, are associated with ticks, including Dermacentor marginatus and Dermacentor reticulatus. The expansion of these ticks into new areas increases the risk of infection of their hosts with tick-borne pathogens. The study summarises the importance of 2 species from the genus Dermacentor, i.e. D.marginatus and D.reticulatus, in the spread of spotted fever group rickettsiae in various regions of Europe. The study also focuses on the determinants of the presence of vectors and transmission of rickettsiae, as well as the effects of human infections with these pathogens. The climate changes observed nowadays affect vectors and increase the incidence and spread of tick-borne diseases worldwide. Due to the existing risk of exposure to an increasing number of people, knowledge about the course of these serious diseases and their etiological factors should be disseminated among healthcare professionals as well as in society. There is a great challenge for epidemiological services to provide access to medical and veterinary facilities in order to diagnose and treat rickettsioses. Therefore, the development of a strategy for tick control and the popularisation of knowledge concerning prophylaxis of tick-borne diseases is indispensable.

Molecular-based Survey of Rickettsia spp. and Coxiella burnetii in Mosquitoes (Diptera: Culicidae) from Fars Province, Southern Iran, during 2017-18

Objectives: Since there have not been any studies on the roles of the Iranian mosquitoes in the transmission of Rickettsia spp. and Coxiella burneti, the present study investigates the roles of mosquitoes in the transmission of the pathogens using the PCR techniques for the first time in Iran. Methods: The present study was conducted in Fars province during the activity seasons of mosquitoes in 2017-18. The primer design was done to investigate the probability of mosquito’s contamination with Rickettsia spp. and Coxiella burnetii. The conventional PCR was used after the extraction of DNA from mosquitoes to study the contamination. Results: A total of 1103 adult mosquitoes were collected and identified. Among them, 3 genera and 11 species were identified, including Anopheles (25.74%), Culex (51.84%) and Culiseta (22.39%) genera. All tested mosquitoes were negative in terms of contamination to Rickettsia spp. and Coxiella burnetii. Conclusion: Based on the results, mosquitoes are not considered as vectors of Rickettsia spp. and Coxiella burnetii in this part of the country currently. Further studies on a larger scale are needed to examine the exact role of mosquitoes (as a possible vector with high abundance and mobility) in the transmission of these pathogens in tropical areas of Iran.

Tissue Tropisms and Transstadial Transmission of a Rickettsia Endosymbiont in the Highland Midge, Culicoides impunctatus (Diptera: Ceratopogonidae).

Rickettsia is a genus of intracellular bacteria which can manipulate host reproduction and alter sensitivity to natural enemy attack in a diverse range of arthropods. The maintenance of Rickettsia endosymbionts in insect populations can be achieved through both vertical and horizontal transmission routes. For example, the presence of the symbiont in the follicle cells and salivary glands of Bemisia whiteflies allows Belli group Rickettsia transmission via the germ line and plants, respectively. However, the transmission routes of other Rickettsia bacteria, such as those in the Torix group of the genus, remain underexplored. Through fluorescence in situ hybridization (FISH) and transmission electron microscopy (TEM) screening, this study describes the pattern of Torix Rickettsia tissue tropisms in the highland midge, Culicoides impunctatus (Diptera: Ceratopogonidae). Of note is the high intensity of infection of the ovarian suspensory ligament, suggestive of a novel germ line targeting strategy. Additionally, localization of the symbiont in tissues of several developmental stages suggests transstadial transmission is a major route for ensuring maintenance of Rickettsia within C. impunctatus populations. Aside from providing insights into transmission strategies, the presence of Rickettsia bacteria in the fat body of larvae indicates potential host fitness and vector capacity impacts to be investigated in the future.IMPORTANCE Microbial symbionts of disease vectors have garnered recent attention due to their ability to alter vectorial capacity. Their consideration as a means of arbovirus control depends on symbiont vertical transmission, which leads to spread of the bacteria through a population. Previous work has identified a Rickettsia symbiont present in several species of biting midges (Culicoides spp.), which transmit bluetongue and Schmallenberg arboviruses. However, symbiont transmission strategies and host effects remain underexplored. In this study, we describe the presence of Rickettsia in the ovarian suspensory ligament of Culicoides impunctatus Infection of this organ suggests the connective tissue surrounding developing eggs is important for ensuring vertical transmission of the symbiont in midges and possibly other insects. Additionally, our results indicate Rickettsia localization in the fat body of Culicoides impunctatus As the arboviruses spread by midges often replicate in the fat body, this location implies possible symbiont-virus interactions to be further investigated.

Rickettsia parkeri strain Atlantic rainforest in ticks (Acari: Ixodidae) of wild birds in Arauca, Orinoquia region of Colombia.

Birds are important hosts for the development of the immature stages of several tick species that are vectors for disease-causing microorganisms in animals and humans. Colombia has the highest number of bird species worldwide; however, there is scarce data on the role of birds in the circulation of ticks and their associated pathogens, such as rickettsiae. The department of Arauca has a high diversity of resident and migratory (boreal and austral) birds and ticks associated with the transmission of Rickettsia. The objective of this research was to identify tick species parasitizing birds and to detect Rickettsia species in these ectoparasites. We conducted samplings in the municipalities of Arauca, Cravo Norte, and Tame between November of 2018 and August of 2019. Birds were captured using mist nets and examined for the presence of tick species. The collected ticks were morphologically and molecularly identified. Furthermore, we detected rickettsiae in ticks by amplifying fragments of the citrate synthase (gltA) and outer membrane protein (ompB) genes. We captured 606 birds belonging to 25 families and 115 species. Tick infestation rate was 3.3% (20/606) in the birds captured and eight new associations between wild birds and ticks are reported for the American continent. We identified four tick species: Amblyomma nodosum, Amblyomma longirostre, Amblyomma mixtum, and Amblyomma sp.. Moreover, we confirmed the presence of Rickettsia parkeri strain Atlantic rainforest in A. nodosum, a medically-relevant rickettsia due to cases of rickettsiosis in the American continent. This finding manifests the importance of wild birds as hosts and dispersal agents of ticks infected with pathogenic rickettsiae, as well as the need to monitor migratory birds in the Orinoquia and other regions of Colombia and America.

Housing Conditions Linked to Tick (Ixodida: Ixodidae) Infestation in Rural Areas of Colombia: A Potential Risk for Rickettsial Transmission.

This cross-sectional study explores the different conditions related to the infestation of ticks in households and the potential risks for rickettsial transmission in Urabá, Colombia. The main outcome of interest was villagers' perception of tick infestation. The data were analyzed using a clog-log mixed regression model. Ticks were collected from infested humans to diagnose infection by spotted fever group rickettsiae (SFGR). In addition, a thematic analysis of qualitative data from key informants concerning knowledge about ticks was conducted. The prevalence of infestation of ticks in households was estimated at 60.99% (95% CI: 51.58-93.51). The multivariate model suggested that households with palm leaf roofs (PR = 1.95; 95% CI: 1.19-2.95), canines (PR = 1.76; 95% CI: 1.21-2.46), rats (PR = 2.19; 95% CI: 1.45-3.08), and with the presence of opossums in areas surrounding the households (PR = 1.51; 95% CI: 1.05-2.10) had a higher prevalence of tick infestation. Two samples of the tick species Amblyomma patinoi were found infected with Rickettsia amblyommatis and Candidatus Rickettsia colombianensi. A thematic analysis provided the names that local community members give to ticks, areas where ticks are common, and the individuals at risk of infestation. The presence of domestic, synanthropic, and wild animals suggests a high risk of the dissemination of ticks inside dwellings and close to them in these rural areas.

Recent research milestones in the pathogenesis of human rickettsioses and opportunities ahead.

Infections caused by pathogenic Rickettsia species continue to scourge human health across the globe. From the point of entry at the site of transmission by arthropod vectors, hematogenous dissemination of rickettsiae occurs to diverse host tissues leading to 'rickettsial vasculitis' as the salient feature of pathogenesis. This perspective article accentuates recent breakthrough developments in the context of host-pathogen-vector interactions during rickettsial infections. The subtopics include potential exploitation of circulating macrophages for spread, identification of new entry mechanisms and regulators of actin-based motility, appreciation of metabolites acquired from and effectors delivered into the host, importance of the toxin-antitoxin module in host-cell interactions, effects of the vector microbiome on rickettsial transmission, and niche-specific riboregulation and adaptation. Further research on these aspects will advance our understanding of the biology of rickettsiae as intracellular pathogens and should enable design and development of new approaches to counter rickettsioses in humans and other hosts.

Disease Ecology of Rickettsial Species: A Data Science Approach.

We present an approach to assess the disease ecology of rickettsial species by investigating open databases and by using data science methodologies. First, we explored the epidemiological trend and changes of human rickettsial disease epidemics over the years and compared this trend with knowledge on emerging rickettsial diseases given by published reviews. Second, we investigated the global diversity of rickettsial species recorded in humans, domestic animals and wild mammals, using the Enhanced Infectious Disease Database (EID2) and employing a network analysis approach to represent and quantify transmission ecology of rickettsial species among their carriers, arthropod vectors or mammal reservoirs and humans. Our results confirmed previous studies that emphasized the increasing incidence in rickettsial diseases at the onset of 1970. Using the Global Infectious Diseases and Epidemiology Online Network (GIDEON) database, it was even possible to date the start of this increase of global outbreaks in rickettsial diseases in 1971. Network analysis showed the importance of domestic animals and peridomestic mammals in sharing rickettsial diseases with humans and other wild animals, acting as important hubs or connectors for rickettsial transmission.

Transovarial transmission of Borrelia spp., Rickettsia spp. and Anaplasma phagocytophilum in Ixodes ricinus under field conditions extrapolated from DNA detection in questing larvae

BackgroundIxodes ricinus constitutes the main European vector tick for the Lyme borreliosis pathogen Borrelia burgdorferi (sensu lato), the relapsing fever borrelia Borrelia miyamotoi, as well as Anaplasma phagocytophilum and several Rickettsia species. Under laboratory conditions, a transovarial transmission to the next tick generation is described for Rickettsia spp. and Borrelia spp., especially regarding B. miyamotoi, whereas the efficiency of transovarial transfer under field conditions is largely unstudied.MethodsIn order to better estimate the potential infection risk by tick larvae for humans and animals, 1500 I. ricinus larvae from 50 collected “nests” (larvae adhering to the flag in a clumped manner) were individually examined for Borrelia, Rickettsia and A. phagocytophilum DNA using quantitative real-time PCR (qPCR).ResultsThirty-nine of 50 nests each (78.0%, 95% CI: 64.0–88.5%) were positive for Borrelia spp. and Rickettsia spp. DNA, and in three nests (6.0%, 95% CI: 1.3–16.5%) A. phagocytophilum DNA was detected. Overall, DNA from at least one pathogen could be detected in 90.0% (45/50, 95% CI: 78.2–96.7%) of the nests. Of the 1500 larvae, 137 were positive for Borrelia spp. DNA (9.1%, 95% CI: 7.7–10.7%), 341 for Rickettsia spp. DNA (22.7%, 95% CI: 20.6–24.9%) and three for A. phagocytophilum DNA (0.2%, 95% CI: 0–0.6%). Quantity of Borrelia spp. and Anaplasma spp. DNA in positive larvae was low, with 2.7 × 100Borrelia 5S-23S gene copies and 2.4 × 101A. phagocytophilum msp2/p44 gene copies detected on average, while Rickettsia-positive samples contained on average 5.4 × 102gltA gene copies. Coinfections were found in 66.0% (33/50, 95% CI: 51.2–78.8%) of the nests and 8.6% (38/443, 95% CI: 6.1–11.6%) of positive larvae. In fact, larvae had a significantly higher probability of being infected with Borrelia spp. or Rickettsia spp. when both pathogens were present in the nest.ConclusionsThis study provides evidence for transovarial transmission of Rickettsia spp. and Borrelia spp. in I. ricinus under field conditions, possibly facilitating pathogen persistence in the ecosystem and reducing the dependence on the presence of suitable reservoir hosts. Further studies are needed to prove transovarial transmission and to explain the surprisingly high proportion of nests containing Rickettsia and/or Borrelia DNA-positive larvae compared to infection rates in adult ticks commonly reported in other studies.

Ixodid tick species and two tick-borne pathogens in three areas in the Sudan.

Ticks are important parasites from economic and public health points of view because of their ability to reduce farm animals' productivity and transmit zoonotic diseases. We conducted this cross-sectional study between January and March 2016 and between March and April 2017 to identify tick species in West Darfur, Al-Jazeera, and the River Nile states in the Sudan and to investigate whether these ticks carry Rickettsia spp. and Crimean-Congo hemorrhagic fever (CCHF) virus. In total, 1593 ticks were collected from 207 animals and identified based on morphology or 16S rRNA gene and tested for Rickettsia spp. and CCHF virus either individually or as pools containing 2 to 10 pooled ticks using molecular methods. Overall, 14 tick species belonging to three genera, namely Amblyomma, Hyalomma, and Rhipicephalus, were identified. Hyalomma anatolicum and Rhipicephalus evertsi evertsi were the most frequent ticks. A total of 561 tests comprised of individual or pooled ticks were conducted and 13.7% (77/561) were positive for Rickettsia spp. which were mostly Rickettsia aeschlimannii and R. africae. The highest positivity was noticed among H. rufipes collected from cattle and camels in West Darfur. However, none of the screened Hyalomma ticks harbored CCHF viral RNA. These findings suggest that there might be a risk of zoonotic transmission of Rickettsia spp. by ticks but zoonotic transmission of CCHF virus is apparently doubtful. An in-depth and a country-wide epidemiological study is needed to better understand the dynamic of Rickettsia spp. and CCHF virus in the Sudan.

Comparative analysis of the midgut microbiota of two natural tick vectors of Rickettsia rickettsii

Although the ticks Amblyomma sculptum and Amblyomma aureolatum are important vectors of Rickettsia rickettsii, causative agent of the life-threatening Rocky Mountain spotted fever, A. aureolatum is considerably more susceptible to infection than A. sculptum. As the microbiota can interfere with the colonization of arthropod midgut (MG) by pathogens, in the current study we analyzed the MG microbiota of both tick species. Our results revealed that the MG of A. aureolatum harbors a prominent microbiota, while A. sculptum does not. Remarkably, a significant reduction of the bacterial load was recorded in R. rickettsii-infected A. aureolatum. In addition, the taxonomy analysis of the MG bacterial community of A. aureolatum revealed a dominance of the genus Francisella, suggesting an endosymbiosis. This study is the first step in getting insights into the mechanisms underlying the interactions among Amblyomma species, their microbiota and R. rickettsii. Additional studies to better understand these mechanisms are required and may help the development of novel alternatives to block rickettsial transmission.