A review of the genus Rickettsia in Central America

Molecular detection of rickettsial agents in Amblyomma maculatum ticks (Ixodida: Ixodidae) from Ecuador

Rickettsiales are obligate intracellular bacteria that need vertebrates and arthropods to maintain their life cycles. Some species of the genera Anaplasma, Ehrlichia, and Rickettsia are transmitted by ticks to both animals and humans and can cause mild to severe and even fatal cases. In the Americas, there is substantial data on rickettsial agents, encompassing both clinical cases and the detection of these agents in ticks, but in Ecuador, the information about them remains poorly understood. Therefore, the objective of this study was to detect molecularly rickettsial agents in Amblyomma maculatum ticks in both parasitic and free-living phases collected from domestic animals and pasture in five localities across three coastal provinces of Ecuador. Rickettsia parkeri, Candidatus Rickettsia andeanae, and Ehrlichia sp. were recorded in A. maculatum for the first time in Ecuador. These records were made in a region where antibodies to the Spotted Fever Rickettsia Group were detected in humans. Additional studies are needed to characterize Ehrlichia sp. at a specific level. Furthermore, recognizing the specific Rickettsiales species circulating in the ticks and the hosts within a region is crucial for assessing potential contact risks.

Molecular screening of tick-borne microorganisms in ticks from rural areas of Panama, with the first record of Ehrlichia minasensis in Rhipicephalus microplus from Central America

During a molecular screening of rickettsial, borrelial and protozoal agents in ticks from rural areas of Panama, we detected DNA of Rickettsia amblyommatis in four Amblyomma mixtum collected from horses in a locality in Los Santos province. Ehrlichia minasensis and Anaplasma marginale were identified from three and two Rhipicephalus microplus, respectively, collected on cows from Chiriqui province. No DNA from other tick-borne agents was found. These results increase the information of R. amblyommatis and A. marginale in Panama, and also mark the first record of E. minasensis in Central America.

New hard tick (Acari: Ixodidae) reports and detection of Rickettsia in ticks from Sierra Nevada de Santa Marta, Colombia

The Sierra Nevada de Santa Marta (SNSM), located in northern Colombia, is considered a geographical island with high levels of biodiversity and endemism. However, little is known about tick species and their associated microorganisms at the SNSM. In this study we sampled host-seeking ticks in areas of the town of Minca within the SNSM. We collected 47 ticks identified as Amblyomma pacae, Amblyomma longirostre, Amblyomma ovale, Amblyomma mixtum, Haemaphysalis juxtakochi, Ixodes sp. cf. Ixodes affinis and Ixodes sp. Of these ticks, we tested for Rickettsia spp. by amplifying the gltA, SCA1, and 16S rRNA genes via PCR. Rickettsia amblyommatis was detected in one pool of 3 larvae and in a female of A. pacae. Additonally, we isolated Rickettsia sp. belonging to the group of spotted fevers in larvae of A. longirostre. This study reports new findings of six species of ticks and two species of Rickettsia within the SNSM.

Exotic ticks removed from German travelers

We report the finding of five nymphs and three adult ticks attached to German tourists while traveling the American continents. All eight specimens were morphologically identified and confirmed genetically using the 16S rRNA gene and screened for Rickettsia spp. infections. Five tick species were identified: one Amblyomma mixtum nymph from Ecuador, one Amblyomma varium nymph from Colombia, three Amblyomma coelebs nymphs from Costa Rica, one Amblyomma americanum male from the USA, one Dermacentor andersoni female and one D. andersoni male from Canada. Tick-borne microorganisms screening using the pan-Rickettsia-PCR resulted in two positive and six negative ticks. The A. mixtum nymph was positive for Rickettsia amblyommatis, while the D. andersoni female was positive for Rickettsia peacockii.

Autophagy facilitates intracellular survival of pathogenic rickettsiae in macrophages via evasion of autophagosomal maturation and reduction of microbicidal pro-inflammatory IL-1 cytokine responses

IMPORTANCE

Rickettsia spp. are intracellular bacterial parasites of a wide range of arthropod and vertebrate hosts. Some rickettsiae are responsible for several severe human diseases globally. One interesting feature of these pathogens is their ability to exploit host cytosolic defense responses to their benefits. However, the precise mechanism by which pathogenic Rickettsia spp. elude host defense responses remains unclear. Here, we observed that pathogenic Rickettsia typhi and Rickettsia rickettsii (Sheila Smith [SS]), but not non-pathogenic Rickettsia montanensis, become ubiquitinated and induce autophagy upon entry into macrophages. Moreover, unlike R. montanensis, R. typhi and R. rickettsii (SS) colocalized with LC3B but not with Lamp2 upon host cell entry. Finally, we observed that both R. typhi and R. rickettsii (SS), but not R. montanensis, reduce pro-inflammatory interleukin-1 (IL-1) responses, likely via an autophagy-mediated mechanism. In summary, we identified a previously unappreciated pathway by which both pathogenic R. typhi and R. rickettsii (SS) become ubiquitinated, induce autophagy, avoid autolysosomal destruction, and reduce microbicidal IL-1 cytokine responses to establish an intracytosolic niche in macrophages.

Severe Rickettsia typhi Infections, Costa Rica

Murine typhus is a febrile, fleaborne disease caused by infection with Rickettsia typhi bacteria. Cases can range from mild and nonspecific to fatal. We report 2 cases of murine typhus in Costa Rica, confirming the presence and circulation of R. typhi causing severe disease in the country.

First Report of Multiple Rickettsia sp., Anaplasma sp., and Ehrlichia sp. in the San Miguel Department of El Salvador from Zoonotic Tick Vectors

Neglected bacterial zoonoses are a group of Neglected Tropical Diseases (NTDs) that are commonly underdiagnosed and underreported due to their undifferentiated febrile illness symptomology. Spotted fever group rickettsioses (SFGR), a subset of tick-borne bacterial zoonoses, belong in this group. There is a dichotomy in the reporting and recognition of these pathogens in Central America: countries with reduced human development scores-like El Salvador-have little to no research or surveillance dedicated to these pathogens and the diseases they cause. This was the third-ever tick survey in El Salvador, highlighting the knowledge gap in this country. A total of 253 ticks were collected from 11 animals at two farm sites and one veterinary office. Standard and quantitative PCR were used to detect presence of SFGR, Ehrlichia, and Anaplasma sp. pathogens in ticks. Ehrlichia sp. were detected in 2.4% of all collected ticks and Anaplasma sp. were detected in 5.5% of all ticks. Rickettsia rickettsii was amplified in 18.2% of ticks, and amplicons similar to R. parkeri, and R. felis were found in 0.8% and 0.4%, of collected ticks, respectively. This is the first report of these pathogenic bacterial species in El Salvador. This study emphasizes the need for further surveillance and research including incorporating additional human seroprevalence and testing to understand the public health burden in this country.

Molecular detection of Babesia spp. and Rickettsia spp. in coatis (Nasua nasua) and associated ticks from midwestern Brazil

Procyonids are reservoirs of many zoonotic infectious diseases, including tick-borne pathogens. The role of coatis (Nasua nasua) in the epidemiology of piroplasmids and Rickettsia has not been fully addressed in Brazil. To molecularly study these agents in coatis and associated ticks, animals were sampled in two urban areas in Midwestern Brazil. Blood (n = 163) and tick (n = 248) DNA samples were screened by PCR assays targeting the 18S rRNA and gltA genes of piroplasmids and Rickettsia spp., respectively. Positive samples were further molecularly tested targeting cox-1, cox-3, β-tubulin, cytB, and hsp70 (piroplasmid) and ompA, ompB, and htrA 17-kDa (Rickettsia spp.) genes, sequenced and phylogenetically analyzed. All coatis' blood samples were negative for piroplasmids, whereas five pools of ticks (2%) were positive for two different sequences of Babesia spp.. The first from Amblyomma sculptum nymphs was close (i.e., ≥ 99% nucleotide identity) to a Babesia sp. previously found in capybaras (Hydrochoerus hydrochaeris); the second from Amblyomma dubitatum nymphs and Amblyomma spp. larvae was identical (100% nucleotide identity) to a Babesia sp. detected in opossums (Didelphis albiventris) and associated ticks. Four samples (0.8%) were positive by PCR to two different Rickettsia spp. sequences, being the first from Amblyomma sp. larva identical to Rickettsia belli and the second from A. dubitatum nymph identical to Rickettsia species from Spotted Fever Group (SFG). The detection of piroplasmids and SFG Rickettsia sp. highlights the importance of Amblyomma spp. in the maintenance of tick-borne agents in urban parks where humans and wild and domestic animals are living in sympatry.

Ticks (Acari: Ixodidae) and Associated Pathoge Collected From Domestic Animals and Vegetation in Stann Creek District, Southeastern Belize, Central America

Data on the prevalence and distribution of ticks and tick-borne diseases in Belize are lacking. Ticks (n = 564) collected from dogs, horses, and vegetation in two villages in Stann Creek District in southeastern Belize in 2018, were molecularly identified and screened for tick-borne nonviral human pathogens. The identity of 417 ticks was molecularly confirmed by DNA barcoding as Rhipicephalus sanguineus (Latreille) (66.43%), Amblyomma ovale Koch (15.59%), Dermacentor nitens Neumann (11.51%), Amblyomma sp. ADB0528 (3.6%), and the remainder being small records (2.87%) of Amblyomma coelebs Neumann, Amblyomma imitator Kohls, Amblyomma tapirellum Dunn, Amblyomma auricularium Conil, and Amblyomma maculatum Koch. Individual tick extracts were screened for the presence of Rickettsia spp., Babesia spp., Babesia microti, Borrelia spp., Ehrlichia spp., and Anaplasma spp. using available conventional polymerase chain reaction (PCR) assays. Rickettsia parkeri strain Atlantic Rainforest was identified in five specimens of A. ovale, and one other unidentified tick, all collected from dogs. Another unidentified tick-also collected from a dog-tested positive for an undefined but previously detected Ehrlichia sp. With the exception of D. nitens, all eight other tick species identified in this study were collected on dogs, suggesting that dogs could be usefully employed as sentinel animals for tick surveillance in Belize.

Spotted Fever Group Rickettsioses in Central America: The Research and Public Health Disparity among Socioeconomic Lines

Simple Summary

Tick-borne diseases are an important public health issue globally. Spotted fever group rickettsioses (SFGR), a group of related tick-borne pathogens, can cause significant disease, but is widely underreported and likely misdiagnosed. In Central America, there is little known about SFGR, and there seems to be a socioeconomic-related difference between the most-developed and least-developed countries in the region. The least-developed countries (El Salvador, Guatemala, Honduras, and Nicaragua) disproportionately underreport research or studies regarding SFGR disease compared to the most-developed countries (Belize, Panama, and Costa Rica). We compared human development and poverty indicators among Central American countries for this review of SFGR Rickettsia-related articles. The least-developed countries are at a higher risk or are more vulnerable to SFGR disease than the most-developed countries in this region.

Abstract

Tick-borne diseases including rickettsial diseases are increasing in incidence worldwide. Many rickettsial pathogens can cause disease which is commonly underdiagnosed and underreported; Rickettsia pathogens in the spotted fever group (SFGR) are thus classified as neglected bacterial pathogens. The Central American region shoulders a large proportion of the global neglected disease burden; however, little is known regarding SFGR disease here. Although development varies, four of the seven countries in this region have both the highest poverty rates and SFGR disease burdens (El Salvador, Honduras, Guatemala, and Nicaragua), compared to Belize, Panama, and Costa Rica. Utilizing the Human Development Index (HDI), we compared published articles related to SFGR Rickettsia prevalence in the lowest-HDI-scoring countries to the highest-HDI-scoring countries. Our analysis identified a distinct dichotomy in publication, and by proxy, potentially awareness and knowledge of SFGR tick-borne disease in Central America, where the least-developed countries are at the highest risk for, yet the most vulnerable to, SFGR disease.

The Impact of Deforestation, Urbanization, and Changing Land Use Patterns on the Ecology of Mosquito and Tick-Borne Diseases in Central America

Central America is a unique geographical region that connects North and South America, enclosed by the Caribbean Sea to the East, and the Pacific Ocean to the West. This region, encompassing Belize, Costa Rica, Guatemala, El Salvador, Honduras, Panama, and Nicaragua, is highly vulnerable to the emergence or resurgence of mosquito-borne and tick-borne diseases due to a combination of key ecological and socioeconomic determinants acting together, often in a synergistic fashion. Of particular interest are the effects of land use changes, such as deforestation-driven urbanization and forest degradation, on the incidence and prevalence of these diseases, which are not well understood. In recent years, parts of Central America have experienced social and economic improvements; however, the region still faces major challenges in developing effective strategies and significant investments in public health infrastructure to prevent and control these diseases. In this article, we review the current knowledge and potential impacts of deforestation, urbanization, and other land use changes on mosquito-borne and tick-borne disease transmission in Central America and how these anthropogenic drivers could affect the risk for disease emergence and resurgence in the region. These issues are addressed in the context of other interconnected environmental and social challenges.

First detection and genetic identification of Rickettsia infection in Rhipicephalus sanguineus (Acari: Ixodidae) ticks collected from Southern Taiwan

The prevalence and genetic identity of Rickettsia infection in Rhipicephalus sanguineus sensu lato (s.l.) ticks were determined in Taiwan. In total 1153 ticks were examined for Rickettsia infection by PCR assay targeting the citrate synthase gene (gltA) of Rickettsia. The prevalence of Rickettsia infection in R. sanguineus s.l. ticks with a general infection rate of 2.2%, and was detected in nymph, male and female stages of R. sanguineus s.l. ticks with an infection rate of 3.1, 2.0 and 1.1%, respectively. Phylogenetic relationships were analyzed by comparing the gltA sequences obtained from four Taiwan strains and 16 other strains representing 13 genospecies of Rickettsia. Phylogenetic analyses reveal that one Taiwan strain was genetically affiliated with the Japan isolate (GRA-1 strain) which belongs to the spotted fever group (R. parkeri/R. honei) and three Taiwan strains were genetically affiliated with the transitional group of Rickettsia (R. felis). Intra- and inter-species analysis also indicated the genetic distance (GD) of the Taiwan strains with a lower level of GD < 0.011, 0.023 and 0.003 as compared with the type strains of R. parkeri, R. honei and R. felis, respectively. Our findings reveal the first detection of Rickettsia infections (R. parkeri/R. honei and R. felis) in R. sanguineus s.l. ticks of Taiwan. These results also highlight the epidemiological significance of diverse Rickettsia species existed in R. sanguineus s.l. ticks and the potential threat for the geographical transmission of Rickettsia infection in Taiwan.

An annotated checklist of the eukaryotic parasites of humans, exclusive of fungi and algae

The classification of "parasites" in the medical field is a challenging notion, a group which historically has included all eukaryotes exclusive of fungi that invade and derive resources from the human host. Since antiquity, humans have been identifying and documenting parasitic infections, and this collective catalog of parasitic agents has expanded considerably with technology. As our understanding of species boundaries and the use of molecular tools has evolved, so has our concept of the taxonomy of human parasites. Consequently, new species have been recognized while others have been relegated to synonyms. On the other hand, the decline of expertise in classical parasitology and limited curricula have led to a loss of awareness of many rarely encountered species. Here, we provide a comprehensive checklist of all reported eukaryotic organisms (excluding fungi and allied taxa) parasitizing humans resulting in 274 genus-group taxa and 848 species-group taxa. For each species, or genus where indicated, a concise summary of geographic distribution, natural hosts, route of transmission and site within human host, and vectored pathogens are presented. Ubiquitous, human-adapted species as well as very rare, incidental zoonotic organisms are discussed in this annotated checklist. We also provide a list of 79 excluded genera and species that have been previously reported as human parasites but are not believed to be true human parasites or represent misidentifications or taxonomic changes.

Ticks and Tick-Borne Diseases in Central America and the Caribbean: A One Health Perspective

Ticks have complex life cycles which involve blood-feeding stages found on wild and domestic animals, with humans as accidental hosts. At each blood-feeding stage, ticks can transmit and/or acquire pathogens from their hosts. Therefore, the circulation of tick-borne pathogens (TBPs), especially the zoonotic ones, should be studied in a multi-layered manner, including all components of the chain of infections, following the 'One Health' tenets. The implementation of such an approach requires coordination among major stakeholders (such as veterinarians, physicians, acarologists, and researchers) for the identification of exposure and infection risks and application of effective prevention measures. In this review, we summarize our current knowledge on the epidemiology of tick-borne diseases in Central America and the Caribbean and the challenges associated with the implementation of 'One Health' surveillance and control programs in the region.

Detection and distribution of zoonotic pathogens in wild Norway rats (Rattus norvegicus) from Tehran, Iran

This is the first study on the prevalence of vector-borne zoonotic pathogens found in Rattus norvegicus (R. norvegicus) in urban areas of Tehran, Iran. Serological tests were used to detect IgG antibodies against Coxiella burnetii (C. burnetii) and Rickettsia spp. using a commercial qualitative rat ELISA kit. The frequency of Streptobacillus moniliformis (S. moniliformis) and Bartonella spp. was determined using a conventional PCR method. Molecular detection and characterization of Leptospira spp. were conducted using TaqMan real-time PCR based on lipL32 gene and SecY typing methods. A total of 100 R. norvegicus rats were collected from five regions in Tehran, Iran, and investigated to determine their zoonotic pathogens. S. moniliformis and Bartonella spp. were detected in 23 of 100 (23%) and 17 of 100 (17%) R. norvegicus populations, respectively. The highest prevalence of S. moniliformis and Bartonella spp. with similar frequency rates (n = 6/20; 30%) was seen among the R. norvegicus rats captured from the northern and southern parts of Tehran, respectively. Seroreactivity against C. burnetii and Rickettsia spp. was detected in 4% and 1% of R. norvegicus, respectively. C. burnetii. was identified only in one rat captured from the eastern part of Tehran. Results showed that Leptospira spp. was detected only in two rats, collected from the southern part (n = 2/20; 10%) of Tehran. The secY typing method identified two different Leptospira species including L. interrogans and L. kirschneri. The results showed that urban rats might play an important role in transmission of zoonotic pathogens to humans.

Molecular Detection and Genetic Identification of Rickettsia Infection in Ixodes granulatus Ticks, an Incriminated Vector for Geographical Transmission in Taiwan

Tick-borne Rickettsia pathogens have become an emerging source of zoonotic infections and have a major impact on human health worldwide. In this study, the prevalence and genetic identity of Rickettsia infections in Ixodes granulatus ticks was firstly determined in Kinmen Island of Taiwan. A total of 247 I. granulatus ticks were examined for Rickettsia infection by nested-PCR assay targeting the citrate synthase (gltA) gene of Rickettsia. The Rickettsia infection was detected with a general infection rate of 4.86%, and was detected in nymph, male and female stages with an infection rate of 3.81%, 0% and 6.84%, respectively. Phylogenetic relationships were analyzed by comparing the gltA sequences obtained from four Taiwan strains and 19 other strains representing 13 genospecies of Rickettsia. Phylogenetic analyses reveal that all Taiwan strains were genetically affiliated to the genospecies of spotted fever (R. parkeri) and transitional (R. felis) groups of Rickettsia. Our findings reveal the first detection of R. parkeri-like and R. felis in I. granulatus ticks from Kinmen Island. As a tourist island between Taiwan and mainland China, these results demonstrate the epidemiological significance of diverse Rickettsia species existed in I. granulatus ticks and highlight the potential threat of geographical transmission among humans in the Taiwan area.

Rickettsia-host interaction: strategies of intracytosolic host colonization

Bacterial infection is a highly complex biological process involving a dynamic interaction between the invading microorganism and the host. Specifically, intracellular pathogens seize control over the host cellular processes including membrane dynamics, actin cytoskeleton, phosphoinositide metabolism, intracellular trafficking and immune defense mechanisms to promote their host colonization. To accomplish such challenging tasks, virulent bacteria deploy unique species-specific secreted effectors to evade and/or subvert cellular defense surveillance mechanisms to establish a replication niche. However, despite superficially similar infection strategies, diverse Rickettsia species utilize different effector repertoires to promote host colonization. This review will discuss our current understandings on how different Rickettsia species deploy their effector arsenal to manipulate host cellular processes to promote their intracytosolic life within the mammalian host.

Ticks and tick-borne Rickettsia in El Salvador

From May to November 2013, ticks were collected from wild and domestic hosts that were sampled by convenience in different localities of El Salvador. Among 48 localities, in total 1181 ticks were collected from 200 vertebrate animals, comprising 13 species of wild hosts (amphibian, reptiles, mammals) and five species of domestic mammals, plus four samples from humans and four samples from the environment. Through morphological analysis (corroborated by molecular analyses in a few cases), the following ten tick species were identified: Amblyomma dissimile, Amblyomma mixtum, Amblyomma ovale, Amblyomma cf. parvum, Amblyomma sabanerae, Amblyomma scutatum, Dermacentor dissimilis, Dermacentor nitens, Rhipicephalus microplus, and Rhipicephalus sanguineus sensu lato. Among a sample of 211 tick specimens tested for rickettsial infection by molecular methods, we identified: 'Candidatus Rickettsia colombianensi' in 10% of the A. dissimile ticks and 11% of the A. scutatum ticks; Rickettsia amblyommatis in 77% of the A. mixtum ticks, 50% of the A. cf. parvum ticks, 8% of the D. nitens ticks, and 11% of the Amblyomma spp. nymphs; and Rickettsia bellii in 3% of the A. dissimile ticks and 17% of the A. ovale ticks. The tick fauna of El Salvador is currently represented by 12 reported species.

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.

Novel Rickettsia genotypes in ticks in French Guiana, South America

Rickettsia are obligate intracellular bacteria often associated with ticks and best known for causing human diseases (rickettsiosis), including typhus fever and sporadic cases of serious infection. In this study, we conducted a large survey of ticks in French Guiana to understand the overall diversity of Rickettsia in this remote area largely covered by dense rainforests. Out of 819 individuals (22 tick species in six genera), 252 (30.8%) samples were positive for Rickettsia infection. Multilocus typing and phylogenetic analysis identified 19 Rickettsia genotypes, but none was 100% identical to already known Rickettsia species or strains. Among these 19 genotypes, we identified two validated Rickettsia species, Rickettsia amblyommatis (spotted fever group) and Rickettsia bellii (bellii group), and characterized a novel and divergent Rickettsia phylogenetic group, the guiana group. While some tick hosts of these Rickettsia genotypes are among the most common ticks to bite humans in French Guiana, their potential pathogenicity remains entirely unknown. However, we found a strong association between Rickettsia genotypes and their host tick species, suggesting that most of these Rickettsia genotypes may be nonpathogenic forms maintained through transovarial transmission.

Exposure of dogs to Rickettsia spp. in Costa Rica: Risk factors for PCR-positive ectoparasites and seropositivity

Infection of dogs with Rickettsia spp. can result in inapparent, mild, or severe disease. Moreover, common dog ticks and fleas are able to transmit rickettsiae to nearby humans. In this study, the seroprevalence of spotted fever group (SFG) rickettsiae was determined in dogs of Costa Rica, as well as possible risk factors associated with exposure. An interview of owners and clinical examinations were performed in a country-wide sample of 441 dogs. IgG antibodies were determined in 399 dogs by indirect immunofluorescence assay (IFA) using antigens of Rickettsia rickettsii, R. amblyommatis, and R. felis. The presence of Rickettsia spp. gltA gene was evaluated by PCR in ticks and fleas. Poisson regression was performed to assess possible risk factors associated with seropositivity, as well as with having PCR-positive ticks and fleas. The overall seroprevalence to SFG rickettsiae was 10.0% (end titers 64 to 256). Rhipicephalus sanguineus s.l. (116/441; 26.3%) and Ctenocephalides felis (153/441; 34.7%) were the most common ectoparasites. Rickettsia DNA was detected in 30% (39/130) and 32.3% (56/173) of tick and flea pools, respectively. Seropositivity was significantly associated with mean age of 2 to 7 years, scrotal edema, walking problems, large size, and tick and flea infestation. Being a purebred dog was a possible protective factor. The presence of Rickettsia PCR-positive ticks was associated with being a purebred dog, while flea treatment was protective. Having PCR-positive fleas was associated with being purebred and the number of people in the dog's environment; protective factors were free roaming and being an outdoor dog. Results confirm that dogs in Costa Rica are exposed to different species of SFG rickettsiae. This may represent a risk to human health and underscores the need for accurate diagnosis in dogs and humans. Surveillance of rickettsial infection in canines may provide useful indicators to understand the epidemiology of these zoonoses.

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10% of dogs were exposed to different species of SFG rickettsiae in Costa Rica.

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Risk factors included age, large size, and tick and flea infestation.

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Rickettsiae were detected in approximately 30% of flea and tick pools.

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Flea treatment and free roaming were protective against infected ticks and fleas.

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Surveillance and accurate diagnosis are required in dogs and humans.

Detection of Rickettsia spp. in Rhipicephalus sanguineus (sensu lato) collected from free-roaming dogs in Coahuila state, northern Mexico

Background

The aim of this study was to detect and molecularly identify Rickettsia spp. in Rhipicephalus sanguineus (sensu lato) collected from free-roaming dogs in 30 communities from five municipalities in the south of Coahuila State, northern Mexico, where Rocky Mountain spotted fever is endemic.

Methods

In total, 60 dogs from each municipality were examined for engorged ticks. DNA was isolated from tick pools and conventional PCR assays targeting the 23S-5S ribosomal RNA intergenic spacer and outer membrane protein (ompA) gene of Rickettsia spp. were performed.

Results

All ticks (n = 1238) were morphologically identified as R. sanguineus (s.l.). Six pools (each with six engorged females) from four municipalities were positive to Rickettsia spp. DNA sequencing and phylogenetic analyses confirmed the presence of R. rickettsii and R. rhipicephali in R. sanguineus (s.l.) in these ticks.

Conclusions

This study confirms the presence of R. rickettsii and R. rhipicephali in R. sanguineus (s.l.) from stray dogs in the south of Coahuila. This suggests that stray dogs may play a role in the inter-municipal dissemination of infected ticks in this region. Further research is required to assess whether ticks from stray dogs could serve as good indicators for the molecular xenomonitoring of R. rickettsii in this region. Considering that R. sanguineus (s.l.) is a proven vector of R. rickettsii in Mexico, increased awareness regarding permanent tick control in dogs is warranted.

Rickettsia rickettsii Whole-Cell Antigens Offer Protection against Rocky Mountain Spotted Fever in the Canine Host

Rocky Mountain spotted fever (RMSF) is a potentially fatal tick-borne disease in people and dogs. RMSF is reported in the United States and several countries in North, Central, and South America.

Rocky Mountain spotted fever (RMSF) is a potentially fatal tick-borne disease in people and dogs. RMSF is reported in the United States and several countries in North, Central, and South America. The causative agent of this disease, Rickettsia rickettsii, is transmitted by several species of ticks, including Dermacentor andersoni, Rhipicephalus sanguineus, and Amblyomma americanum. RMSF clinical signs generally include fever, headache, nausea, vomiting, muscle pain, lack of appetite, and rash. If untreated, it can quickly progress into a life-threatening illness in people and dogs, with high fatality rates ranging from 30 to 80%. While RMSF has been known for over a century, recent epidemiological data suggest that the numbers of documented cases and the fatality rates remain high in people, particularly during the last two decades in parts of North America. Currently, there are no vaccines available to prevent RMSF in either dogs or people. In this study, we investigated the efficacies of two experimental vaccines, a subunit vaccine containing two recombinant outer membrane proteins as recombinant antigens (RCA) and a whole-cell inactivated antigen vaccine (WCA), in conferring protection against virulent R. rickettsii infection challenge in a newly established canine model for RMSF. Dogs vaccinated with WCA were protected from RMSF, whereas those receiving RCA developed disease similar to that of nonvaccinated R. rickettsii-infected dogs. WCA also reduced the pathogen loads to nearly undetected levels in the blood, lungs, liver, spleen, and brain and induced bacterial antigen-specific immune responses. This study provides the first evidence of the protective ability of WCA against RMSF in dogs.

Detection of Rickettsia monacensis and Rickettsia amblyommatis in ticks collected from dogs in Costa Rica and Nicaragua

The neotropical climate of Central America provides ideal conditions for ticks, which may transmit several human pathogens, including spotted-fever group Rickettsia. Dogs may act as sentinels or reservoirs for human tick-borne diseases due to shared tick species. Here, ticks were collected from 680 client-owned dogs in Nicaragua and Costa Rica, and a total of 316 tick pools were investigated for Rickettsia infection by quantitative real-time PCR (qPCR) targeting the gltA gene. Subsequently, up to six further genomic targets (16S rDNA, gltA, sca4, ompA, ompB and the 23S-5S intergenic spacer) were investigated for Rickettsia species determination. The predominant tick species was Rhipicephalus sanguineus sensu lato (s.l.) (19.9% of dogs infested in Costa Rica, 48.0% in Nicaragua), followed by Ixodes boliviensis (3.1% in Costa Rica / none in Nicaragua) and Amblyomma ovale (4.8% in Costa Rica, 0.9% in Nicaragua). In total, 22 of 316 tick pools containing 60 of 1023 individual ticks were Rickettsia-positive as determined by qPCR, resulting in a minimum infection rate (MIR) of 2.2%. In detail, MIR in Rh. sanguineus s.l. was 0.7% (7/281 pools), in I. boliviensis 33.3% (12/13 pools) and in A. ovale 9.7% (3/22 pools). For 11 of 12 positive I. boliviensis pools and one of six positive Rh. sanguineus s.l. pools, the species could be determined as R. monacensis. R. amblyommatis was identified in one Rh. sanguineus s.l. pool from Costa Rica and one A. ovale pool from Nicaragua. Nine of 12 R. monacensis-positive tick pools were collected in San Rafael de Heredia, Costa Rica, indicating a high local occurrence in this area. This study supports recent evidence that R. monacensis is present on the American continent. Its high local occurrence among dog-associated I. boliviensis, which may also parasitize humans, in Costa Rica gives cause for concern, as R. monacensis is also pathogenic to humans.