Density and behavior of capybara (Hydrochoerus hydrochaeris) ticks (Acari: Ixodidae) Amblyomma sculptum and Amblyomma dubitatum with notes on Rickettsia bellii infection: Assessing human exposure risk

In several urban and peri‑urban areas of Brazil, populations of Amblyomma sculptum and Amblyomma dubitatum ticks are maintained by capybaras (Hydrochoerus hydrochaeris). In some of these areas, this host and these tick species are associated with Brazilian spotted fever (BSF), a lethal human disease caused by the bacterium Rickettsia rickettsii. In this work, we evaluated the risk of human exposure to these tick species using four collection techniques to discern host-seeking behavior. The study was carried out in 10 urban sites inhabited by capybaras in Uberlândia, a BSF-free municipality in southeastern Brazil. Ticks were collected in areas of 400 m2 at each site and at three seasons. Within the same municipality, the distance and speed of A. sculptum nymphs moving towards the CO2 traps were evaluated. In a sample of ticks Rickettsia DNA was investigated. During the study period, 52,953 ticks were collected. Among these, 83.4 % were A. sculptum (1,523 adults, 10,545 nymphs and 32,104 larvae) and 16.6 % were A. dubitatum (464 adults, 2,153 nymphs and 6,164 larvae). An average annual questing tick density of 4.4/m² was observed, with the highest density recorded at one site in autumn (31.8/m²) and the lowest in summer at another site (0.03/m²). The visual search yielded the highest proportion of A. sculptum larvae, constituting 47 % of the total and 63.6 % of all A. sculptum larvae. In contrast, CO2 traps collected a greater proportion of nymphs and adults of A. sculptum ticks. In the case of A. dubitatum, the CO2 trap was the most efficient technique with 57.7 % of captures of this species, especially of nymphs (94.5 % of captures) and adults (97.8 % of captures). Ticks' ambush height on vegetation (9 to 77 cm), observed by visual search 30 times, yielded a total of 20,771 ticks. Of these, 28 (93 %) were A. sculptum ticks, with only two (7 %) identified as A. dubitatum ticks. Among A. sculptum ticks, the nymph was the most attracted stage to humans and larva in the case of A. dubitatum. Amblyomma sculptum adults and nymphs were significantly more attracted to humans than those of A. dubitatum, but A. dubitatum larvae were significantly more attracted than the same stage of A. sculptum. The maximum distance and speed of horizontal displacement for A. sculptum nymphs were five meters and 2.0 m/h, respectively. The only species of Rickettsia detected in ticks, exclusively in A. dubitatum, was R. bellii. Importantly, it was observed that the higher the proportion of A. sculptum in the community of ticks, the lower the rate of infection of A. dubitatum by R. bellii. In conclusion, host-seeking behavior differed between the two tick species, as well as between stages of the same species. A greater restriction of A. dubitatum ticks to the soil was observed, while larvae and nymphs of A. sculptum dispersed higher in the vegetation. The behavior presented by A. sculptum provides greater opportunities for contact with the hosts, while A. dubitatum depends more on an active search for a host, the hunter behavior. Taken together, these observations show that a human being crossing an area infested with A. sculptum and A. dubitatum ticks will have almost exclusive contact with A. sculptum larvae and/or nymphs. Humans in a stationary position (sitting, lying or immobile) are exposed to both tick species, but they are more attractive to adults and mainly nymphs of A. sculptum compared to the corresponding stages of the tick A. dubitatum. The negative effect of A. sculptum on A. dubitatum infection by R. bellii deserves further studies.

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

Bacterial endosymbionts play important roles in the life histories of herbivorous insects by impacting their development, survival, reproduction, and stress tolerance. How endosymbionts may affect the interactions between plants and insect herbivores is still largely unclear. Here, we show that endosymbiotic Rickettsia belli can provide mutual benefits also outside of their hosts when the sap-sucking whitefly Bemisia tabaci transmits them to plants. This transmission facilitates the spread of Rickettsia but is shown to also enhance the performance of the whitefly and co-infesting caterpillars. In contrast, Rickettsia infection enhanced plant resistance to several pathogens. Inside the plants, Rickettsia triggers the expression of salicylic acid-related genes and the two pathogen-resistance genes TGA 2.1 and VRP, whereas they repressed genes of the jasmonic acid pathway. Performance experiments using wild type and mutant tomato plants confirmed that Rickettsia enhances the plants' suitability for insect herbivores but makes them more resistant to fungal and viral pathogens. Our results imply that endosymbiotic Rickettsia of phloem-feeding insects affects plant defenses in a manner that facilitates their spread and transmission. This novel insight into how insects can exploit endosymbionts to manipulate plant defenses also opens possibilities to interfere with their ability to do so as a crop protection strategy.

IMPORTANCE

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.

A systematic review of neglected tropical diseases (NTDs) in Myanmar

BACKGROUND

Neglected tropical diseases (NTDs) affect most impoverished communities in developing countries, like Myanmar in Southeast Asia. NTDs have been understudied and underreported in Myanmar.

METHODS

A systematic review of published and grey literature (1900-2023) on neglected tropical diseases (NTDs) in Myanmar was conducted. The literature search included five international databases: PubMed, EMBASE, Ovid Global Health, and Web of Science Core Collection and one national database: the Myanmar Central Biomedical Library (locally published papers and grey literature). The selection criteria included articles with all types of study designs of current or previous infections conducted in humans, that reported NTDs, recognised by WHO, US CDC, and listed in PLoS NTDs. We included melioidosis and rickettsioses which we consider also meet the definition of an NTD.

RESULTS

A total of 5941 records were retrieved and screened, of which, 672 (11%) met the selection criteria and were included in this review. Of the included articles, 449 (65%) were published after 2000 and 369 (55%) were from two regions (Yangon and Mandalay) of Myanmar. Of the included articles, 238 (35%) reported bacterial NTDs, 212 (32%) viral NTDs, 153 (23%) helminth NTDs, 25 (4%) protozoal NTDs and 39 (6%) reported more than one aetiology. Based on reported frequency in descending order, the bacterial NTDs were leprosy, Escherichia coli enteritis, salmonellosis, cholera, shigellosis, melioidosis, leptospirosis and rickettsioses; the viral NTDs were dengue, chikungunya and Japanese encephalitis virus (JEV) infection; the protozoal NTDs were amoebiasis, giardiasis and leishmaniasis, and the helminth NTDs were ascariasis, trichuriasis, hookworm disease, filariasis and strongyloidiasis.

CONCLUSION

This review summarises NTDs reported in Myanmar over the past 100 years. The findings suggest that most NTDs are likely to be under reported, especially from the majority of the country which is far from academic centres. Research capacity building together with strengthening of laboratory systems would lead to better understanding of the true burden of NTDs in Myanmar.

TRIAL REGISTRATION

PROSPERO registration ID: CRD42018092627.

Rickettsial Disease Outbreak, Mexico, 2022

Beginning in 2022, Nuevo Leon, Mexico, experienced an outbreak of rickettsioses that is still ongoing despite multidisciplinary control efforts. A total of 57 cases have been confirmed, particularly affecting children. We report a high mortality rate among hospitalized persons in Nuevo Leon. Continuing efforts are required to control the outbreak.

Serologic Evidence of Orientia Infection among Rural Population, Cauca Department, Colombia

We assessed serum samples collected in Cauca Department, Colombia, from 486 persons for Orientia seroreactivity. Overall, 13.8% showed reactive IgG by indirect immunofluorescence antibody assay and ELISA. Of those samples, 30% (20/67) were confirmed to be positive by Western blot, showing >1 reactive band to Orientia 56-kD or 47-kD antigens.

Novel Chronic Anaplasmosis in Splenectomized Patient, Amazon Rainforest

We report a case of unusual human anaplasmosis in the Amazon rainforest of French Guiana. Molecular typing demonstrated that the pathogen is a novel Anaplasma species, distinct to all known species, and more genetically related to recently described Anaplasma spp. causing infections in rainforest wild fauna of Brazil.

Exosomally Targeting microRNA23a Ameliorates Microvascular Endothelial Barrier Dysfunction Following Rickettsial Infection

Spotted fever group rickettsioses caused by Rickettsia (R) are devastating human infections, which mainly target microvascular endothelial cells (ECs) and can induce lethal EC barrier dysfunction in the brain and lungs. Our previous evidence reveals that exosomes (Exos) derived from rickettsial-infected ECs, namely R-ECExos, can induce disruption of the tight junctional (TJ) protein ZO-1 and barrier dysfunction of human normal recipient brain microvascular endothelial cells (BMECs). However, the underlying mechanism remains elusive. Given that we have observed that microRNA23a (miR23a), a negative regulator of endothelial ZO-1 mRNA, is selectively sorted into R-ECExos, the aim of the present study was to characterize the potential functional role of exosomal miR23a delivered by R-ECExos in normal recipient BMECs. We demonstrated that EC-derived Exos (ECExos) have the capacity to deliver oligonucleotide RNAs to normal recipient BMECs in an RNase-abundant environment. miR23a in ECExos impairs normal recipient BMEC barrier function, directly targeting TJ protein ZO-1 mRNAs. In separate studies using a traditional in vitro model and a novel single living-cell biomechanical assay, our group demonstrated that miR23a anti-sense oligonucleotide-enriched ECExos ameliorate R-ECExo-provoked recipient BMEC dysfunction in association with stabilization of ZO-1 in a dose-dependent manner. These results suggest that Exo-based therapy could potentially prove to be a promising strategy to improve vascular barrier function during bacterial infection and concomitant inflammation.

Ticks on reptiles and amphibians in Central Amazonia, with notes on rickettsial infections

Reptiles and amphibians are exceptional hosts for different ectoparasites, including mites and ticks. In this study, we investigated tick infestations on reptiles and amphibians trapped in Central Amazonia, and also assessed the presence of rickettsial infections in the collected ticks. From September 2016 to September 2019, 385 reptiles (350 lizards, 20 snakes, 12 tortoises, and three caimans) and 120 amphibians (119 anurans and one caecilian) were captured and examined for ectoparasites. Overall, 35 (10%) lizards, three (25%) tortoises and one (0.8%) toad were parasitized by ticks (124 larvae, 32 nymphs, and 22 adults). In lizards, tick infestation varied significantly according to landscape category and age group. Based on combined morphological and molecular analyses, these ticks were identified as Amblyomma humerale (14 larvae, 12 nymphs, 19 males, and one female), Amblyomma nodosum (three larvae, one nymph, and one female), and Amblyomma rotundatum (four larvae, three nymphs, and one female), and Amblyomma spp. (103 larvae and 16 nymphs). Our study presents the first records of A. nodosum in the Amazonas state and suggests that teiid lizards are important hosts for larvae and nymphs of A. humerale in Central Amazonia. Moreover, a nymph of A. humerale collected from a common tegu (Tupinambis teguixin) was found positive for Rickettsia amblyommatis, which agrees with previous reports, suggesting that the A. humerale-R. amblyommatis relationship may be more common than currently recognized.

Massive Tick Bites Causing Spotted Fever Rickettsial Infection: A Hazard in a Tea Plantation, Sri Lanka

Tea plantations in Sri Lanka cover the central hills of the island, where spotted fever group (SFG) rickettsial infection is common. In most cases, the history of tick bite is obscure and eschars are not present. A 45-y-old female experienced massive tick bites while working in her tea plantation. She developed fever 2 d after exposure, but the diagnosis of SFG infection was not considered until a skin rash appeared on the eighth day. She had a very high titer of antirickettsial antibodies detected by immunofluorescence assay and responded to doxycycline. Here, we highlight the high risk of exposure to ticks and tick bites within tea estates and its causal relationship to SFG infection, which is increasing in Sri Lanka. Active case detection, notification, surveillance, and community awareness are imperative. Possible preventative measures for tick bites have to be introduced. There is a need to explore the effectiveness of local remedies currently in use.

Severe Case of Rickettsiosis Identified by Metagenomic Sequencing, China

A case of Rickettsia sibirica subspecies sibirica BJ-90 infection in China was identified by metagenomic analysis of an eschar biopsy specimen and confirmed by nested PCR. Seroprevalence of spotted fever group Rickettsia was ≈17.4% among the local population. This report highlights the threat of rickettsioses to public health in the Qinghai–Tibet Plateau.

Co-infection with Severe Fever with Thrombocytopenia Syndrome Virus and Rickettsia japonica after Tick Bite, Japan

Severe fever with thrombocytopenia syndrome was diagnosed in a febrile woman in Japan after a tick bite. However, Rickettsia japonica DNA was retrospectively detected in the eschar specimen, suggesting co-infection from the bite. Establishment of the severe fever with thrombocytopenia syndrome virus infection might have overpowered the R. japonica infection.

Seasonal dynamics of Amblyomma sculptum in two areas of the Cerrado biome midwestern Brazil, where human cases of rickettsiosis have been reported

Amblyomma sculptum is a common human-biting tick in Brazil, where it plays an important role as a vector of Rickettsia rickettsii, the agent of the Brazilian spotted fever. Herein, we studied the seasonal dynamics of A. sculptum in an urban area of the Cerrado biome in midwestern Brazil, where human rickettsiosis is endemic. Ticks were collected in two sites located within the campus of Federal University of Goiás. The collections were done by dragging, flagging and visual search. In total, 117,685 ticks were collected, including 100,627 Amblyomma spp. larvae, 10,055 nymphs and 6977 adults of A. sculptum, and one nymph and 25 adults of Amblyomma dubitatum. The highest peak of larvae occurred in June 2018 and in July 2019, whereas nymphs peaked in July 2018 and September 2019. Adults reached their highest numbers in March 2018 and November 2019. These data suggest that A. sculptum develops one generation per year in this urban area of the Cerrado biome in midwestern Brazil. Interestingly, the peak of nymphs occurred during the same period of all confirmed cases of rickettsiosis in Goiás, suggesting a possible relationship between the seasonal dynamics of this tick stage and rickettsiosis transmission in this state.

[Rickettsioses]

Rickettsioses. Rickettsioses are caused by intracellular bacteria from order of rickettsiales. They are transmitted by arthropods, mainly ticks, lice, fleas or other species close to chiggers, mainly in tropical areas. Some rickettsioses are endemic in France and others can be seen in patients returning from travel, including those presenting with "fever of unknown origin". Rickettsiae can't be isolated by conventional blood cultures in the laboratory. The diagnosis of rickettsial diseases is often made by serology, but specific PCR based on the swab of an inoculation eschar when it is present is a simple and rapid tool. The standard treatment for rickettsioses is doxycycline, that should be started as soon as clinical suspicion occurs, before diagnostic confirmation since some rickettsial diseases can be fatal.

Rickettsia spp. in Dermacentor marginatus ticks: analysis of the host-vector-pathogen interactions in a northern Mediterranean area

In this work, we have analyzed the key features of Rickettsia spp. maintenance in Dermacentor marginatus ticks in four regions of the northern Mediterranean area, where extensive investigations are currently lacking. For this purpose, 380 adult D. marginatus ticks were collected from vegetation and wild ungulates during a 3-year study. A host-vector-pathogen interaction approach was applied to investigate the key components of the disease systems and evaluate their respective weight in the intensity of infection in natural foci. A high variability in the R. slovaca infection rate among sampling sites was observed, whereas R. raoultii was sporadically present and at low infection rates. Dermacentor marginatus presence was confirmed in all the investigated regions. The local wild boar population showed a strong association with adult D. marginatus ticks. The results of this investigation suggest that wild boars not only maintain D. marginatus populations by feeding adult ticks, but may also have a potential role in the eco-epidemiology of rickettsioses, as carriers of rickettsiae-infected ticks. The public health implications of these results are discussed.

Distribution of Spotted Fever Group Rickettsiae in Hard Ticks (Ixodida: Ixodidae) from Panamanian Urban and Rural Environments (2007-2013)

Tick-borne rickettsiosis is an important emerging disease in Panama; to date, there have been 12 confirmed cases, including eight fatalities. To evaluate the distribution of rickettsiae in Panamanian ticks, we collected questing and on-host ticks in urban and rural towns in elevations varying between 0 and 2300 m. A total of 63 sites (13 urban and 50 rural towns) were used to develop models of spatial distributions. We found the following tick species: Rhipicephalus sanguineus s.l. (present in 54 of 63 towns and cities), Amblyomma mixtum (45/63), Dermacentor nitens (40/63), A. ovale (37/63), Rhipicephalus microplus (33/63), A. oblongoguttatum (33/63), Ixodes affinis (3/63), and Ixodes boliviensis (2/63). Rhipicephalus sanguineus s.l. was present in urban and rural towns, and other species were present only in rural towns. DNA was extracted from 408 R. sanguineus s.l., 387 A. mixtum, 103 A. ovale, and 11 A. oblongoguttatum and later tested for rickettsiae genes using PCR. Rickettsia DNA was detected in ticks from 21 of 63 localities. Rickettsia rickettsii was detected in five A. mixtum (1.29%), and Candidatus "Rickettsia amblyommii" was found in 138 A. mixtum (35%), 14 R. sanguineus (3.4%), and one A. ovale (0.9%). These results suggest that much of rural Panama is suitable for the expansion of tick populations and could favor the appearance of new tick-borne rickettsiosis outbreaks.

Rickettsioses and Q fever in travelers (2004-2013)

Rickettsioses (also called typhus) are associated with arthropods, including ticks, mites, fleas, and lice, although Q fever is more frequently acquired through the inhalation of contaminated aerosols or the consumption of milk. These zoonoses first emerged in the field of travel medicine 20 years ago. Here, we review rickettsioses and Q fever in travelers, highlighting cases reported in the past decade. African tick bite fever and Mediterranean spotted fever are the two most frequent spotted fevers. While the presentation of these fevers is typically benign, cardiac and neurological complications due to African tick bite fever have been reported, and Mediterranean spotted fever has been complicated by multi-organ failure and death in a few cases. Murine typhus and Q fever remain difficult to recognize and diagnose because these illnesses often present with only fever. New molecular tools, particularly when deployed with samples obtained from eschar swabs, might be easily implemented in laboratories with PCR facilities. Doxycycline must be introduced upon clinical suspicion of rickettsioses or Q fever and should be considered in cases of fever of unknown origin in travelers who are returning from at-risk geographic areas.

First report of mild Brazilian spotted fever associated to arthritis

We describe the first Brazilian case of mild Rickettsiosis, complicated by knee monoarthritis, in young adult bitten by a tick on his left leg in Camburi zone, located in São Sebastião municipality, southern coastal region of the State of São Paulo, in the Atlantic rainforest region, Brazil. The patient developed inoculation eschar at the tick bite site associated with enlarged lymph nodes in the left groin, fever, polyarthralgia, headache and macular rash. Twenty days after tick bite episode, he displayed monoarthritis in his right knee. The diagnosis of mild Rickettsiosis was established by sequential immunological analysis in serum and synovial fluid, using the indirect immunofluorescence (IF) assay for antibodies reactive with Rickettsia parkeri and Rickettsia rickettsii. The mild Rickettsiosis is an emerging zoonosis, that must be investigated by physicians, including rheumatologists, in patients that present macular rash, fever and eventually arthritis, after visiting the southern coastal Atlantic rainforest region in Brazil.

Proteome analysis ofRickettsia felis highlights the expression profile of intracellular bacteria

The proteome of Rickettsia felis, an obligate intracellular bacterium responsible for spotted fever, was analyzed using two complementary proteomic approaches: 2-DE coupled with MALDI-TOF, and SDS-PAGE with nanoLC-MS/MS. This strategy allowed identification of 165 proteins and helped to answer some questions raised by the genome sequence of this bacterium. We successfully identified potential virulence factors including two putative adhesins, four proteins of the type IV secretion system, four Sca autotransporters, four components of ABC transporters, some R. felis-specific proteins, and one antitoxin of the toxin-antitoxin system. Notably, the antitoxin was the first to be identified in intracellular bacteria. Only one protein containing rickettsia palindromic repeats was found, whereas none of the split genes, transposases, or tetratricopeptide/ankyrin repeats were detectably expressed. Comparison of the protein expression profiles of R. felis and 23 other bacterial species according to functional categories showed that intracellular bacteria express more proteins related to translation, especially ribosomal proteins. However, the remaining bacteria express more proteins related to energy production and carbohydrate/amino acid metabolism. In conclusion, this study reveals R. felis virulence factor expression and highlights the unique protein expression profile of intracellular bacteria.

Localization of antigen in tissue cells; antigens of rickettsiae and mumps virus

Rickettsiae of epidemic typhus fever and Rocky Mountain spotted fever have been microscopically localized and identified in smears of exudates and tissue sections from infected cotton rats by means of homologous antibody labelled with fluorescein. Epidemic typhus has also been identified in smears from single infected human body lice. Mumps virus antigen has been microscopically localized in the parotid of the experimentally infected monkey by the same method. The antigenic material, probably active virus, was found in the cytoplasm of the acinar cells. Such infected acini were scattered irregularly throughout the gland. Some antigen could be seen in the lumens of the parotid ducts and small amounts were present in the cytoplasm of the epithelial cells lining the ducts.

Serious waterborne and wilderness infections

Serious waterborne and wilderness infections are common and usually treatable if diagnosed early. The differential diagnosis for these infections requires a careful and thorough history and physical examination. Common clinical presentations include acute febrile illnesses, altered mental status, diarrhea, or pneumonia. Pathogens causing serious infections include bacteria, fungi, viruses, and protozoa. Epidemiologic help can be obtained from local or state health departments as well as the Centers for Disease Control.

Molecular evidence for single Wolbachia infections among geographic strains of the flour beetle Tribolium confusum

Infections with the rickettsial microorganism Wolbachia are cytoplasmically inherited and occur in a wide range of insect species and several other arthropods. Wolbachia infection often results in unidirectional cytoplasmic incompatibility (CI): crosses between infected males and uninfected females are incompatible and show a reduction of progeny or complete inviability. Unidirectional CI can also occur when males harbouring two incompatible Wolbachia strains are crossed with females infected with only one of the two strains. In the flour beetle Tribolium confusum, Wolbachia infections are of particular interest because of the severity of incompatibility. Typically, no progeny results from the incompatible cross, whereas only partial incompatibility is observed in most other hosts. Werren et al. (1995a) reported that Wolbachia infections in T. confusum consist of two bacterial strains belonging to distinct phylogenic groups, based on PCR amplification and sequence analysis of the bacterial cell division gene ftsZ. However, Fialho & Stevens (1996) showed that eight strains of T. confusum were infected with a single and common incompatibility type. Here we report analysis of the ftsZ gene by specific PCR amplification. Diagnostic restriction enzyme assays revealed no evidence of double infections in 11 geographic strains of T. confusum, including the strain examined by Werren et al. (1995a). Further, sequence analysis of the Wolbachia ftsZ gene and an internal transcribed spacer (ITS) region in two of these strains displayed no nucleotide variation or evidence of polymorphisms. Results suggest that T. confusum is infected with B-group Wolbachia only.