Wild rodent fleas carrying Bartonella and Rickettsia in an area endemic for vector-borne diseases from Argentina.

Vector-borne diseases account for nearly 20% of all globally recognised infectious diseases. Within the spectrum of flea-borne pathogens, Bartonella and Rickettsia bacteria are prominent, contributing to the emergence and resurgence of diseases on a global scale. This study investigates the presence of species of Bartonella and Rickettsia harboured by fleas collected from wild rodents in northwestern Argentina (NWA). A total of 28 fleas from three genera and seven species were assessed. DNA of Bartonella and Rickettsia spp. was found in 12 fleas (42.8%). Phylogenetic analysis of concatenated sequences of gltA and rpoB genes showed the presence of Bartonella quintana in eight fleas of two species, Craneopsylla minerva minerva and Polygenis acodontis. Phylogenetic analysis of concatenated sequences of gltA, ompA and ompB genes identified Rickettsia felis in ten fleas of five species, C. m. minerva, P. acodontis, Polygenis bohlsi bohlsi, Polygenis byturus and Tiamastus palpalis. These bacterial species mark the first report in all flea species studied. This study represents the first survey of flea-borne bacteria for NWA. The results provide information to address strategies for the control and prevention of bartonellosis and rickettsiosis that could have an impact on public health in one of the geographical areas of Argentina with the highest incidence of infections transmitted to humans by ectoparasites.

Effect of environmental variables on the abundance of Amblyomma ticks, potential vectors of Rickettsia parkeri in central Brazil.

Amblyomma ticks are vectors of both Rickettsia rickettsii and R. parkeri in the Americas, where capybaras (Hydrochoerus hydrochaeris) are the main hosts in urban areas, thus contributing to the transmission of spotted fever. Herein, we studied: (i) the seasonal dynamics and abundance of ticks in areas where capybaras live, (ii) the effect of environmental variables on tick abundance, and (iii) the presence of Rickettsia-infected ticks. Between September 2021 and September 2022, we sampled ticks using cloth-dragging at 194 sites on the shore of Lake Paranoá in Brasília, Brazil. We measured environmental data (season, vegetation type, canopy density, temperature, humidity, and presence or vestige of capybara) at each site. Nymphs and adults were morphologically identified to the species level, and a selected tick sample including larvae was subjected to genotypic identification. We investigated Rickettsia-infected ticks by PCR (gltA, htrA, ompB, and ompA genes) and associations between tick abundance and environmental variables using Generalized Linear Models. A total of 30,334 ticks (96% larvae) were captured. Ticks were identified as Amblyomma, with A. sculptum comprising 97% of the adult/nymphs. Genotype identification of a larval sample confirmed that 95% belonged to A. dubitatum. Seasonal variables showed significant effects on tick abundance. Most larvae and nymphs were captured during the early dry season, while the adults were more abundant during the wet season. Vegetation variables and the presence of capybaras showed no association with tick abundance. Rickettsia parkeri group and R. bellii were identified in A. dubitatum, while A. sculptum presented R. bellii. We conclude that: (i) Amblyomma ticks are widely distributed in Lake Paranoá throughout the year, especially larvae at the dry season, (ii) the abundance of Amblyomma ticks is explained more by climatic factors than by vegetation or presence of capybaras, and (iii) A. dubitatum ticks are potential vectors of R. parkeri in Brasília.

Ticks (Acari: Ixodidae) and rickettsiae associated with wild boars in a rural area of Minas Gerais, Brazil.

Wild boars or feral pigs are classified by the Brazilian Institute for the Environment and Renewable Resources (IBAMA) in "Category I of invasive exotic species". They cause economic losses, harm the environment, serve as hosts and reservoirs for several zoonotic disease agents, and provide a blood meal for tick species that act as vectors for zoonotic diseases. The objective of this study was to identify tick species on wild boars, assess host-seeking ticks in the related environment, and identify other potential tick hosts coexisting with wild boars on a farm located in the state of Minas Gerais, southeastern Brazil. Additionally, the study aimed to determine the presence of rickettsiae in these arthropods and assess the exposure of wild boars to rickettsiae species from the Spotted Fever Group and Rickettsia bellii through serology. A total of 3585 host-seeking ticks from three species (Amblyomma sculptum - 41.58%; Amblyomma dubitatum - 0.39% and Rhipicephalus microplus - 0.05%) were collected in the environment and A. sculptum was the most abundant species. Thirty-one wild boars were evaluated, resulting in the collection of 415 ticks, all of which were A. sculptum. Rickettsia DNA was not detected in samples of A. sculptum and R. microplus from the environment or in A. sculptum ticks from wild boars. However, all A. dubitatum ticks (n = 14) had Rickettsia bellii DNA confirmed by the species-specific PCR protocol. Out of the 31 serum samples from wild boars, 24 reacted with at least one Rickettsia antigen. Among these, seven individuals exhibited a reaction to a probable homologous antigen (PHA) of three rickettsiae species: R. rickettsii (n = 3), R. amblyommatis (n = 3) and R. rhipicephali (n = 1). Despite the high prevalence of seroreactivity, titers were low, indicating limited exposure to Rickettsia spp. Camera traps generated 874 animal records, capturing a total of 1688 individuals. At least 11 species of birds and 14 species of mammals (12 wild and two domestic) shared the environment with wild boars and potentially shared ticks with them. These findings provide baseline information for understanding the sharing of ticks and tick-borne pathogens between wild boars and other animals within the Cerrado biome. Further studies are necessary to monitor the potential and actual risk of wild boars to harbor infected ticks and their role in the transmission and maintenance cycle of Rickettsia spp.

Domestic dogs as amplifying hosts of Rickettsia rickettsii for Amblyomma aureolatum ticks.

Brazilian spotted fever (BSF) is an acute infectious disease caused by the bacterium Rickettsia rickettsii, which is transmitted by different tick species. Due to deleterious effects caused on ticks, the horizontal transmission of R. rickettsii through amplifying hosts is crucial for its maintenance in tick populations among BSF-endemic areas. The tick Amblyomma aureolatum is the main vector of R. rickettsii in the São Paulo metropolitan area; nevertheless, it is not known which vertebrate could act as an amplifying host for this tick species. Herein, we evaluated the potential of domestic dogs - primary hosts for A. aureolatum adults in BSF-endemic areas - to act as amplifying hosts. For this purpose, A. aureolatum non-infected adults were allowed to feed on two groups of dogs: the control group (G1), composed of one dog not exposed to R. rickettsii; and, the infected group (G2), composed of three dogs infected with R. rickettsii via tick parasitism. All G2-dogs became ill, seroconverted to R. rickettsii, and rickettsial DNA was detected in 87% of the engorged females that fed on them. Transovarial transmission rate was estimated to be 25% and infected larvae successfully transmitted R. rickettsii to guinea-pigs, confirming transovarial transmission and vector competence. No rickettsial DNA was detected in individual samples of eggs or larvae, which precluded the estimation of filial infection rate, but implies that it was low. Our results suggest that domestic dogs act as amplifying hosts of R. rickettsii for A. aureolatum ticks in BSF-endemic areas in Brazil.

Experimental infection and vector competence of Amblyomma patinoi, a member of the Amblyomma cajennense species complex, for the human pathogen Rickettsia rickettsii.

Amblyomma patinoi ticks infected with Rickettsia rickettsii are present in Colombia, but its vector competence is unknown. Hence, we evaluated the vector competence of A. patinoi with R. rickettsii under laboratory conditions. Experimental guinea pigs and rabbits (males and females) were separated in the infected group (IG) and the control group (CG). In the IG, the filial 1 (F1) larvae (R. rickettsii-free) from Colombian A. patinoi engorged female specimens were exposed to R. rickettsii (ITU strain) by feeding on infected guinea pigs. Next, F1 nymphs and adults, and F2 larvae were allowed to feed on uninfected guinea pigs or rabbits and tested by qPCR targeting the gltA rickettsial gene. All animals used to feed the IG F1 ticks became febrile and had R. rickettsii infection (89% fatality rate) detected through serological or molecular techniques. After the F1 larvae ticks became R. rickettsii infected, subsequent IG tick stages were able to maintain the rickettsial infection by transstadial maintenance to all infested animals, indicating A. patinoi vector competence. Subsequently, almost 31% of the F1 female egg masses and only 42% of their F2 larvae were infected. Less than 50% of the infected females transmitted R. rickettsii transovarially, and only a part of the offspring were infected. This study demonstrated that A. patinoi might not be able to sustain R. rickettsii infection by transovarial transmission for successive tick generations without horizontal transmission via rickettsemic hosts. This condition might result in low R. rickettsii-infection rates of A. patinoi under natural conditions.

Urban ecology of hosts and vectors of Rickettsia in a rickettsiosis-endemic city of the Yucatan peninsula, Mexico.

Rickettsioses are vector-borne zoonotic diseases that occur in urban environments. Currently, they are associated with the presence of domestic and synanthropic animals, the ectoparasites that they harbor, and their local habitat. The implementation of prevention actions relies on the understanding of the local ecology of interactions between hosts, vector species, and the etiologic agents. In this context, this study aimed to explore and describe the occurrence of infected mammals and their ectoparasites in human urban dwellings, and those characteristics of urban dwellings associated to the presence of Rickettsia infected animals in groups of households where at least one human case of rickettsiosis has occurred in the previous year of the study. Briefly, blood-samples and ectoparasites from synanthropic and domestic animals, were obtained from groups of households from different areas of an urban settlement. Serologic and molecular diagnostics helped to identify Spotted Fever Group (SFG) and TG (Typhus Group) Rickettsia in animal and ectoparasite samples. A total of 99 mammals were sampled, 29 opossums (Didelphis virginiana), 13 house mice (Mus musculus), seven black rats (Rattus rattus) and 50 dogs. Infection occurrence in opossums was 8.3% of SFG, 50% for TG, and 4.2% of undetermined group. For house mice 46.2% for SFG and 30.8% were undetermined. Black rats 28.6% of SFG and 57.1% undetermined. Finally, dogs were 19.1% of SFG, 57.4% to TG, and 23.4% belonged to undetermined group. A total of 424 ectoparasites were collected from the mammals. In opossums occurred the ticks Ambyomma sp., Ornithodoros (Alecterobius) nr. talaje, and the flea Ctenocephalides felis. In dogs we found the ticks Rhipicephalus sanguineus s. l., Amblyomma sp., O. (A.) nr. talaje, and the flea Ct. felis. No ectoparasites were collected from rodents. The occurrence of infected animals was associated primarily with the material of the backyard floor, the type of sanitary system in the household, the presence of garbage in the backyard, presence of firewood storage, stored polyethylene terephthalate (PET) containers for sale to recyclers, and the store of construction supplies in the backyard. Nonetheless a generalized linear model showed that the household with a backyard with a dirt floor or other non-concrete material has more chances of harboring infected animals (RR= 1.74, 95% CI= 1.07-2.84 and RR= 1.03, 95% CI= 0.39-2.32 respectively). In contrast, when the house has a sanitary system of urban sewer system or a latrine outside de house, the chances of having infected animals decreased significantly (RR= 0.39, 95% CI= 0.12-0.94 and RR= 0.46, 95% CI= 0.03-2.22). We conclude that both SFG and TG rickettsioses occur in animals and their ectoparasites in peridomiciles of urban households were at least one human rickettsiosis case had occurred.

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.

Clinical and epidemiological comparison of Rickettsia parkeri rickettsiosis, related to Amblyomma triste and Amblyomma tigrinum, in Argentina.

The aim of this work was to compare the epidemiological and clinical characteristics of Rickettsia parkeri rickettsiosis related to Amblyomma triste and Amblyomma tigrinum ecological regions in Argentina. We reviewed cases of R. parkeri rickettsiosis from 2007 to 2017 evaluated at Muñiz Hospital, directly or through referral. Univariate analysis was used to examine the association between different variables and the disease related by each vector species. The eighteen cases of R. parkeri rickettsiosis included had fever, inoculation eschar and all except one had rash. Regional differences in epidemiological variables were identified, depending on the vector. There was a significantly increased risk of exposure to A. tigrinum in peri-domestic areas (odd ratio 12, p = 0.02), whereas an increased risk of exposure to A. triste was evident in wildlife areas (odd ratio 12, p = 0.02). Seasonality of R. parkeri rickettsiosis differed based on its vector. Cases associated with A. triste occurred predominantly during spring and summer, whereas those associated with A. tigrinum occurred during fall, winter, and springtime. Exanthema was maculopapular (13/18), maculo-vesicular (3/18) or petechial (1/18). No clinical differences were identified depending on the vector.

[Lymphadenopathy transmitted by tick. A pediatric case of rickettsiosis in primary care]. / Linfadenopatía transmitida por garrapata. Un caso pediátrico de rickettsiosis en atención primaria.

The entity called tick-borne lymphadenopathy, also known as dermacentor-borne necrosis eritema lymphadenopathy, is included in the differential diagnosis of diseases transmitted by ticks, which have increased considerably in recent years due to greater clinical-epidemiological observation and diagnostic improvement. It is a zoonosis caused by Rickettsia slovaca and transmitted by the bite of the Dermacentor marginatus tick. Affected patients have a necrotic eschar surrounded by an erythematous halo in the scalp, as well as painful regional lymphadenopathy. We present a seven-year-old male who shows, after the extraction of a tick, a necrotic eschar on the scalp, accompanied by lymphadenopathy and low-grade fever. The study of polymerase chain reaction and culture of the lesion confirm the presence of Rickettsia slovaca. The patient received oral azithromycin with a good response. In Primary Care, it is important to monitor the tick bites, to detect possible diseases transmitted by them.

La entidad llamada tick-borne lymphadenopathy, también conocida como dermacentor-borne necrosis eritema lymphadenopathy, se incluye dentro del diagnóstico diferencial de enfermedades transmitidas por garrapatas, que han aumentado considerablemente en los últimos años debido a una mayor observación clínica-epidemiológica y mejoría diagnóstica. Es una zoonosis causada por Rickettsia slovaca y transmitida por la picadura de la garrapata Dermacentor marginatus. Los pacientes afectados tienen una escara necrótica rodeada de un halo eritematoso en el cuero cabelludo y adenopatías regionales dolorosas. Se presenta a un varón de siete años que mostró, tras la extracción de una garrapata, una escara necrótica en el cuero cabelludo, con adenopatías y febrícula. La reacción en cadena de la polimerasa y el cultivo de la lesión confirmaron la presencia de Rickettsia slovaca. El paciente recibió azitromicina oral con buena respuesta. En Atención Primaria, es importante el seguimiento de las picaduras de garrapatas para detectar posibles enfermedades transmitidas por estas.

Phylogenetic divergence between Rickettsia amblyommatis strains from Argentina.

The aim of this study was to investigate if there is a phylogenetic divergence of Rickettsia amblyommatis strains from different phytogeographic provinces of Argentina and South America. Therefore, ompA and ompB gene sequences of R. amblyommatis DNA detected in Amblyomma hadanii and Amblyomma neumanni ticks from the Yungas and Chaco phytogeographic provinces, respectively, were obtained. These sequences were compared with GenBank sequences from R. amblyommatis from different countries of the American continent. The analyses shown that ompA haplotypes of R. amblyommatis form two clusters which differ phylogenetically. Regarding to ompB sequences, three groups of R. amblyommatis strains were detected. It could be shown that strains of R. amblyommatis detected in A. hadanii from the phytogeographic province Yungas are phylogenetic different to them detected in A. neumanni from the phytogeographic province Chaco. Furthermore, it could be observed that strains detected in different tick species associated with different phytogeographic provinces of the American continent differ phylogenetically.

Serologic evidence of rickettsial diseases associated with tick bites in workers of urban veterinary clinics.

BACKGROUND & OBJECTIVES: Rickettsial and other zoonotic diseases are a latent risk for workers of veterinary clinics. The objective of this study was to evaluate the prevalence and the associated risk factors of parasitosis caused by Rhipicephalus sanguineus, and to estimate the seroprevalence of rickettsial diseases in workers of urban veterinary clinics of Juárez city, México. METHODS: The participants of the study were recruited from 63 private veterinary clinics and hospitals. The serological analysis of the blood samples collected was carried out using immunofluorescence assay (IFA). The statistical analysis for prevalences, risk factors, and correlation was performed with the SAS program. RESULTS: In total, 167 veterinary workers were included in the study. The prevalence of tick bites was 40% (67/167), and the risk factors associated with the occurrence of bites included the activities performed in the clinic and the number of labour hours spent per week. About 21% (35/167) of participants were seropositive to R. rickettsii, 28% (47/167) to Ehrlichia chaffeensis, and 24% (40/167) to Anaplasma phagocytophilum. A correlation was observed between: the number of workers in the clinics and the proportion of tick bites (r2 = 0.865); the prevalence of bites and the seropositivity of the participants to at least one pathogen (r2 = 0.924); and the number of bites per individual and infection to pathogens (r2 = 0.838). INTERPRETATION & CONCLUSION: Workers in urban veterinary clinics are highly exposed to tick bites and, therefore, to the diseases they transmit. Hence, it is important to implement prevention measures and perform constant monitoring of these diseases.

Human Parasitism by Amblyomma parkeri Ticks Infected with Candidatus Rickettsia paranaensis, Brazil.

Spotted fever is the main rickettsial disease in Brazil. We report 12 cases of human parasitism by Amblyomma parkeri in the Atlantic rainforest, an area of Brazil to which spotted fever is endemic. Nine of the ticks were infected with Candidatus Rickettsia paranaensis.

First molecular detection of Rickettsia sp. strain Atlantic rainforest in Amblyomma ovale ticks from Espírito Santo state, Brazil / Primeira detecção molecular da Rickettsia sp. cepa Mata Atlântica em carrapatos Amblyomma ovale do estado do Espírito Santo, Brasil

Abstract Espírito Santo state (southeastern Brazil) is considered an endemic area for spotted fever group rickettsioses. In February 2017, we received in our laboratory seven unfed Amblyomma ovale adult ticks collected by a farmer from his clothes and body (not attached) during a working day in the rural area of Ibiraçu municipality, Espírito Santo state. By polymerase chain reaction (PCR) analyses, targeting gltA and ompA rickettsial genes, the DNA of Rickettsia was detected in 6/7 (85.7%) A. ovale. In all cases, DNA sequencing of PCR products revealed that consensus sequences of both genes were 100% identical to gltA and ompA corresponding sequences of Rickettsia sp. strain Atlantic rainforest retrieved from GenBank. This study reports the first molecular detection of Rickettsia sp. strain Atlantic rainforest in A. ovale ticks from Espírito Santo state. Our findings indicate a new Brazilian state in the southeast region at risk of human infection with this tick-borne emerging rickettsial agent.

Resumo O estado do Espírito Santo (Sudeste do Brasil) é considerado área endêmica para riquetsioses do Grupo Febre Maculosa. Em fevereiro de 2017, recebemos em nosso laboratório sete carrapatos adultos Amblyomma ovale não ingurgitados, coletados por um fazendeiro nas suas roupas e corpo (não fixadas) durante um dia de trabalho, em área rural do municipio de Ibiraçu, estado do Espírito Santo. Por meio de reação em cadeia da polimerase (PCR), amplificando os genes riquetsiais gltA e ompA , foi detectado ADN de Rickettsia em 6/7 (85,7%) dos A. ovale . O sequenciamento dos produtos de PCR indicou que as sequências consenso de ambos genes foram 100% idênticos às sequências correspondentes dos genes gltA e ompA da Rickettsia sp. cepa Mata Atlântica recuperadas do GenBank. Este estudo relata a primeira detecção molecular da Rickettsia sp. cepa Mata Atlântica em carrapatos A. ovale do estado do Espírito Santo. Nossos resultados apontam um novo estado brasileiro da região Sudeste com risco de infecção humana por este agente rickettsial emergente transmitido por carrapatos.

Molecular detection of the human pathogen Rickettsia parkeri strain Atlantic rainforest in Amblyomma ovale ticks in Argentina.

Human rickettsioses caused by Rickettsia parkeri strain Atlantic rainforest in Brazil motivated the analysis of Amblyomma ovale ticks in Misiones province, a similar ecological region in northeastern Argentina. During 2010-2017, 393 A. ovale ticks were collected from domestic and wild animals and from vegetation, and 177 were pooled for rickettsial detection by PCR targeting the gltA, ompA and ompB genes. A sample consisting of a pool of two A. ovale adults collected on Nasua nasua was positive for Rickettsia parkeri strain Atlantic rainforest. Since the Atlantic rainforest areas in Brazil share environmental characteristics with Misiones province, the transmission cycle of R. parkeri strain Atlantic rainforest observed in Brazil should be extrapolated to Argentina, where awareness on the possibility of occurrence of rickettsiosis cases caused by this strain should be raised.

First molecular detection of Rickettsia sp. strain Atlantic rainforest in Amblyomma ovale ticks from Espírito Santo state, Brazil.

Espírito Santo state (southeastern Brazil) is considered an endemic area for spotted fever group rickettsioses. In February 2017, we received in our laboratory seven unfed Amblyomma ovale adult ticks collected by a farmer from his clothes and body (not attached) during a working day in the rural area of Ibiraçu municipality, Espírito Santo state. By polymerase chain reaction (PCR) analyses, targeting gltA and ompA rickettsial genes, the DNA of Rickettsia was detected in 6/7 (85.7%) A. ovale. In all cases, DNA sequencing of PCR products revealed that consensus sequences of both genes were 100% identical to gltA and ompA corresponding sequences of Rickettsia sp. strain Atlantic rainforest retrieved from GenBank. This study reports the first molecular detection of Rickettsia sp. strain Atlantic rainforest in A. ovale ticks from Espírito Santo state. Our findings indicate a new Brazilian state in the southeast region at risk of human infection with this tick-borne emerging rickettsial agent.

Rickettsia parkeri in Dermacentor parumapertus Ticks, Mexico.

During a study to identify zoonotic pathogens in northwestern Mexico, we detected the presence of a rickettsial agent in Dermacentor parumapertus ticks from black-tailed jackrabbits (Lepus californicus). Comparison of 4 gene sequences (gltA, htrA, ompA, and ompB) of this agent showed 99%-100% identity with sequences of Rickettsia parkeri.

New records of tick-associated spotted fever group Rickettsia in an Amazon-Savannah ecotone, Brazil.

Human rickettsiosis has been recorded in the Amazon Biome. However, the epidemiological cycle of causative rickettsiae has not been fully accounted for in the Amazon region. This study investigates the presence of spotted fever group (SFG) Rickettsia spp. in free-living unfed ticks of the Amblyomma genus. The study was conducted in seven municipalities in Rondonia State, Brazil, where the main biomes are Amazon forest, Brazilian Savannah and their ecotones (areas of ecological tension between open ombrophilous forest and savannah). The following tick species were collected: Amblyomma cajennense (sensu lato) s.l., A. cajennense (sensu stricto) s.s., A. coelebs, A. naponense, A. oblongoguttatum, A. romitii, A. scalpturatum and A. sculptum. A total of 167 adults, 248 nymphs and 1004 larvae were subjected to DNA extraction and polymerase chain reaction (PCR) to determine the presence of SFG Rickettsia spp. PCR-positive samples included: one A. cajennense s.s. female and one A. cajennense s.l. male from a rural area in Vilhena Municipality; 10 nymphs and a sample of larvae of A. cajennense s.l. from a peri-urban area in Cacoal Municipality; and an A. oblongoguttatum adult male from a rural area of Pimenta Bueno Municipality. All sequences obtained exhibited 100% identity with Rickettsia amblyommatis sequences. This is the first confirmation of SFG Rickettsia in an A. oblongoguttatum tick. Furthermore, this is the first record of SFG Rickettsia in the municipalities targeted by this study. These results warn that SFG Rickettsia circulation poses a threat in Rondonia State (among Amazon-Savannah ecotones), and that this threat is increased by the fact that SFG Rickettsia infect a human-biting tick species hitherto unconfirmed as a vector.

The rice rat Euryoryzomys russatus, a competent amplifying host of Rickettsia parkeri strain Atlantic rainforest for the tick Amblyomma ovale.

Rickettsia parkeri strain Atlantic rainforest (SAR) is the etiological agent of a spotted fever group rickettsiosis in Brazil, where it is transmitted to humans by the tick Amblyomma ovale. A previous study demonstrated that R. parkeri SAR was successfully maintained in A. ovale ticks by transstadial and transovarial passages; however, because this agent induced lower reproduction rates in A. ovale, the participation of a vertebrate amplifier host, yet to be determined, was speculated. Since the rice rat Euryoryzomys russatus was demonstrated to be the most important host for immature stages of A. ovale in a focus of R. parkeri SAR transmission, the present study evaluated the competence of rice rats to act as amplifying host of R. parkeri SAR for A. ovale ticks. Rice rats were infested with R. parkeri SAR-infected A. ovale nymphs, and four days later with uninfected A. ovale larvae. Rickettsial transmission to rats was confirmed by seroconversion to R. parkeri antigens. Detached engorged larvae were allowed to molt to nymphs, in which rickettsial DNA was detected in up to 60% (mean: 20%) of the specimens. When part of these nymphs was allowed to feed on susceptible rice rats, rickettsial transmission was confirmed by seroconversion, indicating that there was successful horizontal transmission of R. parkeri SAR from infected nymphs to uninfected larvae in the previous acquisition infestations. Because we used naïve, susceptible rats, we infer that this horizontal transmission occurred via a systemic infection (rickettsemia) in the rat. Our results, coupled with previous epidemiological studies, suggest that under natural conditions rice rats could be acting as amplifying hosts of R. parkeri SAR to A. ovale ticks.

Detection of Rickettsia spp. in ticks (Acari: Ixodidae) of domestic animals in Colombia.

Rickettsiosis are emerging or re-emerging diseases, with a worldwide distribution associated to transmission by arthropod vectors. Rickettsia species belong to the spotted fever group (SFG) and are transmitted by hard ticks (Acari: Ixodidae) that may act as vectors and reservoirs. This study carried out a molecular detection of Rickettsia from 7 species of the family Ixodidae collected from domestic hosts by PCR amplification of fragments of the citrate synthase "gltA" gene and outer membrane protein "ompA" gene. Of the 204 samples analyzed, 11.3% (23) were positive for rickettsial infection. Three Rickettsia species belonging to the SFG were found, constituting the first reports of Rickettsia rickettsii in 2 departments of Colombia. Furthermore, we confirmed the first occurrence of Candidatus Rickettsia andeanae in Colombia, a species with an unknown pathogenic role in humans. These results raise awareness regarding the need to increase epidemiological control measures, as well as to consider new endemic regions in Colombia for Rocky Mountain spotted fever (RMSF).

Rickettsial infection in ticks (Acari: Ixodidae) from reptiles in the Colombian Caribbean.

Although more reptiles are illegally traded in Colombia than any other group of animals, for both local and international markets, little is known about ticks associated with reptiles or pathogens associated with these ticks. In this study, ticks were collected from reptiles in Magdalena, Cesar and La Guajira regions in northern Colombia, and identified morphologically using taxonomic keys and molecularly by sequencing of the COI gene. In addition, Rickettsia spp. were detected by PCR amplifying the gltA, 16S rRNA, and sca1 genes. Ticks were identified as Amblyomma dissimile, representing the first record for this species in 17 of the 26 species of reptiles sampled. Additionally, our data expand the distribution range for this tick in Colombia. Rickettsia spp. DNA was detected in 18 ticks (3.6%) from 16 reptiles. Sequence analyses indicated that most of the Rickettsia were members of the R. monacensis clade, most closely related to Rickettsia sp. strain Colombianensi. We detected one tick infected with a Rickettsia with 99% identity to R. bellii.