Roaming Dogs, Intense Brown Dog Tick Infestation, and Emerging Rocky Mountain Spotted Fever in Tijuana, México.

A two decades-long epidemic of Rocky Mountain spotted fever in northern México reached the U.S. border city of Tijuana in 2021. Cases were near the city periphery in marginalized areas, some lacking infrastructure such as streets or utilities. We worked in the three census areas where human cases were reported and in 12 additional control Áreas Geoestadisticas Básicas. There were dogs, the primary tick host and Rickettsia rickettsii reservoir, in 76% of homes, with 2.2 owned dogs per home on average, approximately equal numbers of roaming dogs were seen, and 46.2% of owned dogs were allowed to roam in the street. Sixty-eight percent of people had heard of Rocky Mountain spotted fever (RMSF), and 35% self-reported tick infestation, including 19% of homes without dogs. Ticks appeared to move among houses of adjacent neighbors. Of 191 examined dogs, 61.8% were tick-infested, with 6-fold increased odds if they were allowed to roam. Although no dogs were Rickettsia polymerase chain reaction-positive, we found one R. rickettsii- and 11 Rickettsia massiliae-infected ticks. The rickettsial IgG seroprevalence by immunofluorescence antibody assay was 76.4%, associated with unhealthy body condition, adults, dogs with >10 ticks, more dogs being seen in the area, and dogs being permitted in the street. Insufficient medical and canine management resources have contributed to a case fatality rate of RMSF that has exceeded 50% in areas. High canine seroprevalence suggests risks to people and dogs; unfortunately, herd immunity is impeded by high turnover in the canine population owing to the birth of puppies and high death rates. Binational One Health workers should monitor disease spread, enact canine population management and tick eradication, and provide prevention, diagnostic, and treatment support.

Optimal control of a tick population with a view to control of Rocky Mountain Spotted Fever.

In some regions of the Americas, domestic dogs are the host for the tick vector Rhipicephalus sanguineus, and spread the tick-borne pathogen Rickettsia rickettsii, which causes Rocky Mountain Spotted Fever (RMSF) in humans. Interventions are carried out against the vector via dog collars and acaricidal wall treatments. This paper investigates the optimal control of acaricidal wall treatments, using a prior model for populations and disease transmission developed for this particular vector, host, and pathogen. It is modified with a death term during questing stages reflecting the cost of control and level of coverage. In the presence of the control, the percentage of dogs and ticks infected with Ri. rickettsii decreases in a short period and remains suppressed for a longer period, including after treatment is discontinued. Risk of RMSF infection declines by 90% during this time. In the absence of re-application, infected tick and dog populations rebound, indicating the eventual need for repeated treatment.

POTENTIAL SHARED DISEASE RISK AMONG DOGS AND COYOTES (CANIS LATRANS) EXEMPLIFIED BY THE ECOLOGY OF RICKETTSIOSIS IN A ROCKY MOUNTAIN SPOTTED FEVER-EPIDEMIC REGION IN NORTHERN MEXICO.

Rocky Mountain spotted fever (RMSF), caused by the bacterium Rickettsia rickettsii, is a re-emerging tick-borne zoonosis in North America, with hundreds of human fatalities in multiple outbreaks in northern Mexico and the southwestern US in the past few decades. Free-roaming dogs are key because they are reservoirs for the pathogen and the main hosts of the brown dog tick (Rhipicephalus sanguineus), which vectors RMSF in this region. Because coyotes (Canis latrans) can be infected with R. rickettsii and infested with Rh. sanguineus, we hypothesized that space sharing among dogs and coyotes could enhance disease risks. In summer 2021, we captured and sampled 11 coyotes at two sites in Baja California, Mexico, near population centers with human cases of RMSF, and fitted seven individuals with GPS logging collars. We also tested tissue samples, sera, and ectoparasites for DNA of R. rickettsii with PCR and used serology to detect antibodies to R. rickettsii. Finally, we deployed an array of cameras to document dog-coyote interactions. Mean home range size was 40.37 km2. Both GPS and camera data showed considerable home range overlap both between individual coyotes and between coyotes and dogs. Coyotes were active in areas where dogs occur including the domestic interface surrounding human settlements. Although none of our samples were positive for R. rickettsii on PCR, 72.7% (8/11) of the samples were seropositive with titers ≥64. Our data confirm shared space use and risk of shared parasites and disease between coyotes and dogs.

First molecular evidence of Wolbachia occurrence in Amblyomma sculptum (Acari: Ixodidae).

As the main vector for the bacterium Rickettsia rickettsii in Brazil, the tick Amblyomma sculptum is a parasite of great public health importance in this country. Wolbachia is an endosymbiont bacterium highly widespread among invertebrates and because of its impact on its hosts' biology, form a powerful alternative for pests and disease control. The aim of this study was to investigate the occurrence of this bacterium in A. sculptum. For this, 187 adult ticks collected in two municipalities in the interior of the state of São Paulo, Brazil, were analyzed using molecular techniques and bioinformatics tools. A total of 15 ticks were positive for the presence of Wolbachia. Phylogenetic analysis on the 16S rRNA gene indicated that the Wolbachia DNA sequences obtained in this investigation belonged to different clades, probably in supergroups B and F. This was the first study to report the occurrence of Wolbachia in A. sculptum and it enriches knowledge about the susceptibility of ticks to this bacterium. Now that we know that Wolbachia can be found in A. sculptum, the objective for a next study must be to investigate Wolbachia's possible origin in this tick.

Evaluation of a mimotope of the Rickettsia outer membrane protein A (OmpA) as an antigen in enzyme-linked immunosorbent assay to detect rickettsiosis in capybaras (Hydrochoerus hydrochaeris), horses (Equus caballus), and opossums (Didelphis sp.).

Rickettsia rickettsii is the etiological agent of Rocky Mountain spotted fever, which is an important tick-borne zoonosis and, in Brazil, it causes Brazilian spotted fever, which has high lethality rate. This study aimed to evaluate a synthetic peptide corresponding to a segment of the outer membrane protein A (OmpA) as an antigen in a serological test for the diagnosis of rickettsial infections. The amino acid sequence of the peptide was selected by predicting B cell epitopes using B Cell Epitope Prediction (Immune Epitope Database and Analysis Resource) and Epitopia and OmpA sequences of Rickettsia rickettsii strain 'Brazil' and Rickettsia parkeri strains 'Maculatum 20' and 'Portsmouth'. A peptide with amino acid sequence common to both Rickettsia species was synthesized and arbitrarily named OmpA-pLMC. To evaluate this peptide in enzyme-linked immunosorbent assay (ELISA), serum samples of capybara (Hydrochoerus hydrochaeris), horse (Equus caballus), and opossum (Didelphis albiventris) that had been previously tested by indirect immunofluorescence assay (IFA) for rickettsial infection were separated into IFA-positive and IFA-negative groups and used in the assay. There were no significant differences in ELISA optical density (OD) values between IFA-positive and IFA-negative groups with horse samples. The mean OD values were significantly higher in the IFA-positive capybara serum samples (IFA-pos vs. IFA-neg = 2.389 ± 0.761 vs. 1.760 ± 0.840). However, receiver operating characteristic (ROC) curve analysis did not show significant diagnostic parameters. On the other hand, 12 out of 14 (85.7%) opossum samples of the IFA-positive group showed reactivity in ELISA, and this was significantly higher than of the IFA-negative group (0.7196 ± 0.440 vs. 0.2318 ± 0.098, respectively; 85.7% sensitivity, 100% specificity). Therefore, our results show that OmpA-pLMC has a potential to be used in immunodiagnostic assays to detect spotted fever group rickettsial infections.

Tick-borne pathogens detected in sheltered dogs during an epidemic of Rocky Mountain spotted fever, a One Health challenge.

OBJECTIVE: To assess exposure to and infection with 3 pathogens (Rickettsia rickettsii, Anaplasma platys, and Ehrlichia canis) vectored by brown dog ticks (Rhipicephalus sanguineus) in sheltered dogs at the western US-Mexico border. ANIMALS: 239 dogs in shelters in San Diego and Imperial counties, US, and Mexicali and Tijuana, Mexico. PROCEDURES: Each dog had blood drawn and basic demographic data collected. PCR was performed to determine active infection with Rickettsia spp, E canis, and A platys. Serology was performed to determine exposure to Rickettsia, Anaplasma, and Ehrlichia species. RESULTS: 2 of 78 (2.6%) dogs sampled in Tijuana were actively infected with R rickettsii. A single brown dog tick collected from a dog in Tijuana was PCR-positive for R rickettsii. Infection with E canis and A platys ranged across shelters from 0% to 27% and 0% to 33%, respectively. Dogs in all 4 locations demonstrated exposure to all 3 pathogens, though Rickettsia and Ehrlichia seropositivity was highest in Mexicali (81% and 49%, respectively) and Anaplasma seropositivity was highest in Tijuana (45%). CLINICAL RELEVANCE: While infection and exposure were highest in sheltered dogs in the southern locations, dogs in all locations demonstrated exposure to all pathogens, demonstrating the potential for emergence and spread of zoonotic pathogens with significant public health consequences in southern California and northern Baja California. In addition, veterinarians and shelter staff should be aware that Ehrlichia or Anaplasma infection may co-occur with Rocky Mountain spotted fever, which is a human health risk.

Emerging Spotted Fever Rickettsioses in the United States.

Spotted fever rickettsioses are important causes of emerging infectious disease in the United States and elsewhere. Rocky Mountain Spotted Fever, caused by R. rickettsii causes a febrile, acute illness in dogs. Because it circulates in peripheral blood in low copy number and because of the acute nature of the disease, dogs may test PCR and seronegative at the time of presentation. Therefore, therapy with doxycycline must be initiated and continued based on the clinician's index of suspicion. Combining PCR with serologic testing, repeat testing of the same pre-antimicrobial blood sample, and testing convalescent samples for seroconversion facilitates diagnosis. The prognosis can be excellent if appropriate antimicrobial therapy is begun in a timely fashion. It is well established that dogs are sentinels for infection in people in households and communities. Whether R. rickettsii causes illness in cats is not well established. The role of other spotted fever group rickettsia in causing illness in dogs and cats is being elucidated. Veterinarians should keep in mind that novel and well characterized species of SFG Rickettsia are important causes of emerging infectious disease. Veterinarians can play an important role in detecting, defining, and preventing illness in their canine patients and their human companions.

Serological exposure of spotted fever group Rickettsia in capybaras (Hydrochoerus hydrochaeris) from urban parks in Campo Grande, Brazilian Midwest.

BACKGROUND: Rickettsia of the spotted fever group (SFG) has been reported in ticks and domestic animals in Campo Grande (CG), Midwest Brazil. METHODS: We searched for Rickettsia in the SFG in capybaras and their ticks in an urban park in the CG. RESULTS: The seropositivity rate was 88.2% (15/17). Although 87.7% of the capybaras sampled showed infestations with Amblyomma sculptum, A. dubitatum, and Amblyomma spp., no molecular results were detected in ticks. CONCLUSIONS: Since Rickettsia from the SFG circulates among capybaras in the urban parks of Campo Grande, this large rodent species should be monitored within the One Health Agenda.

Long-term persistence of anti-Rickettsia rickettsii antibodies in capybaras, with passive transfer to offspring.

The bacterium Rickettsia rickettsii is the etiological agent of Brazilian spotted fever (BSF), and its most important vector to humans in Brazil is the tick Amblyomma sculptum. Capybaras are the main hosts of A. sculptum in many BSF-endemic areas and are considered valuable sentinels for BSF surveillance. This study aimed to assess the persistence of anti-R. rickettsii antibodies for long periods in capybaras and their passive transfer to offspring. For this purpose, three adult capybaras previously exposed to multiple infections with R. rickettsii were followed up until 3.1 years after their last exposure. During the study, one female delivered five cubs, of which three survived. Blood samples were collected monthly from adults and infants, and serum samples were titrated by indirect immunofluorescence assay (IFA) to determine endpoint titers of anti-R. rickettsii antibodies. All three adults remained seroreactive to R. rickettsii with high endpoint titers until the end of the study. All infants were seroreactive to R. rickettsii after birth and remained seroreactive for one to four months. This study showed that exposure of capybaras to R. rickettsii-infected A. sculptum ticks elicits a persistent antibody response. In addition, there was evidence of passive transfer of R. rickettsii-reactive antibodies to offspring.

Increasing Incidence of Spotted Fever Group Rickettsioses in the United States, 2010-2018.

Spotted fever group Rickettsia species are intracellular bacteria transmitted by tick or mite vectors and that cause human diseases referred to as spotted fever group rickettsioses, or spotted fevers. In the United States, the most recognized and commonly reported spotted fevers are Rocky Mountain spotted fever (RMSF) (Rickettsia rickettsii), Rickettsia parkeri rickettsiosis, Pacific Coast tick fever (Rickettsia species 364D), and rickettsialpox (Rickettsia akari). In this study, we summarize and evaluate surveillance data on spotted fever cases reported to the Centers for Disease Control and Prevention (CDC) through the National Notifiable Diseases Surveillance System from 2010 to 2018. During this period, there were 36,632 reported cases of spotted fevers with 95.83% (N = 35,104) reported as meeting the case definition as probable and 4.17% (N = 1528) reported as meeting the case definition as confirmed. The average national incidence of total cases, both probable and confirmed, was 12.77 cases per million persons per year. The highest statewide incidence was in Arkansas, with 256.84 per million per year, whereas the lowest incidence occurred in California, with 0.32 per million per year (note that spotted fevers were not notifiable in Hawaii and Alaska). Cases of spotted fevers were reported more frequently among males by gender, White by race, and non-Hispanic by ethnicity. The incidence of spotted fevers increased significantly from 2010 to 2018, but it is uncertain how many of the reported cases were RMSF and how many developed from more moderate spotted fevers. Improvement of the ability to differentiate between spotted fever group Rickettsia species is needed.

Small mammals, ticks and rickettsiae in natural and human-modified landscapes: Diversity and occurrence of Brazilian spotted fever in Brazil.

We studied communities of small mammals and their ticks in endemic (E) and non-endemic (NE) areas for Brazilian spotted fever (BSF), aiming to infer if diversity parameters of parasites and hosts could be related to occurrence and prevalence of rickettsial infection, especially Rickettsia rickettsii. We compared E and NE areas in human-modified landscapes (HMLs) and natural areas (BIO) with no report of BSF cases. Composition and equitability were important components of diversity explaining differences among areas. The marsupial Didelphis albiventris was dominant in HMLs, but not in natural areas, and this opossum was the main host for the tick Amblyomma sculptum, principal vector of R. rickettsii, especially in E areas. Communities of ticks were dominated by A. sculptum, followed by Amblyomma dubitatum in E areas. In NE areas, this dominance was inverted, with more A. dubitatum than A. sculptum infesting small mammals, but the numbers of ticks were much lower than in E areas. Composition and abundance of ticks in natural areas were very dissimilar from HMLs, with the lowest tick burdens. Didelphis albiventris in E areas presented higher seroprevalence and endpoint titres against R. rickettsii than in other areas. At least three Rickettsia species, non-pathogenic to humans, were detected in natural areas (Rickettsia bellii, Rickettsia amblyommatis and 'Candidatus Rickettsia andeanae'), and only one non-pathogenic species in HMLs (R. bellii). Our results suggest that higher diversity of ticks, hosts and rickettsiae could be relevant factors in buffering the effect in BSF occurrence. Particularly for D. albiventris, its importance has to be quantified in further studies considering the epidemiological scenario of BSF.

Capybara (Hydrochoerus hydrochaeris) exposure to Rickettsia in the Federal District of Brazil, a non-endemic area for Brazilian spotted fever.

In this study, whole blood samples and ticks were collected from 57 capybaras in recreational areas in the Federal District, Brazil, aiming to investigate the presence of Rickettsia spp. using polymerase chain reaction (PCR) and indirect immunofluorescence (IFAT) assays. None of the capybara blood samples yielded rickettsial DNA by PCR. Among 55 capybara serum samples tested by IFAT, 53 (96.3%) reacted to Rickettsia spp. Among these, 21 (39.6%) identified the R. bellii antigen as the probable antigen involved in a homologous reaction (PAIHR), whereas 2 (3.8%) identified the R. parkeri antigen. Ticks collected from capybaras were identified as 173 Amblyomma sculptum and 410 A. dubitatum, in addition to nine Amblyomma spp. larvae. A sample of 231 ticks was subjected to DNA extraction and PCR for Rickettsia species. None of 122 A. sculptum yielded rickettsial DNA. Molecular evidence of R. bellii was found in 25/108 (23.1%) and of Rickettsia sp. strain Cooperi (R. parkeri-like agent) in 2/108 (1.9%) of the A. dubitatum samples. These results suggest a greater exposure to R. bellii in these capybara populations, in addition to a more significant number of A. dubitatum, which might characterize the Federal District region as not endemic for Brazilian spotted fever.

Prevalence of Rickettsia rickettsii in Ticks: Systematic Review and Meta-Analysis.

Background and Objectives:Rickettsia rickettsii is a pathogen that is known to cause spotted fever, a zoonosis that is endemic in several regions of the Americas. However, no systematic review and meta-analysis has been conducted to estimate the prevalence of this rickettsial disease in the Americas. Therefore, the objective of this study was to estimate the prevalence of R. rickettsii in ticks in the Americas. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed and data were retrieved from four electronic databases: MEDLINE/PubMed, SciELO, ScienceDirect, and Directory of Open Access Journals. The pooled prevalence and heterogeneity were determined using a random-effects model and using Cochran's Q test and I2 index, respectively. Publication bias was assessed using a funnel plot and Egger's method. Results: The pooled prevalence of R. rickettsii in ticks was highest in Colombia (17.00%; confidence interval [95% CI]: 7.01-30.24), followed by Mexico (9.89%; 95% CI: 2.03-22.74), Panama (2.76%; 95% CI: 0.45-6.93), Brazil (2.03%; 95% CI: 0.66-4.14), and the United States (0.50%; 95% CI: 0.15-1.05). The tick species most frequently infected by R. rickettsii were Rhipicephalus sanguineus sensu lato (6.23%; 95% CI: 2.79-10.92) and Amblyomma mixtum (4.36%; 95% CI: 0.25-13.14). Interpretation and Conclusion: It can be suggested that studies aiming to identify the potential vectors of R. rickettsii should be conducted more intensively to better understand the epidemiology of spotted fever in the Americas.

Serological evidence of Rickettsia in horses from a semi-arid Brazilian region.

Brazilian spotted fever (BSF) is a common tick-borne disease caused by Rickettsia rickettsii. Horses are the primary hosts of the main vector, Amblyomma sculptum, and are considered efficient sentinels for circulation of Rickettsia. Therefore, the aim of this study was to detect antibodies reactive to R. rickettsii antigens in horses from a non-endemic area in the north-central region of Bahia state, Brazil. Blood samples and ticks were collected from 70 horses from the municipalities of Senhor do Bonfim, Antônio Gonçalves, Pindobaçu, and Campo Formoso. The sera obtained were tested by an indirect immunofluorescence assay to detect anti-Rickettsia antibodies. Overall, 5.7% (4/70) of the horses reacted to R. rickettsii antigens. Ticks were collected from 18.6% (13/70) of the horses and were identified as A. sculptum and Dermacentor nitens. Despite being a non-endemic area, seropositive animals were identified in our study, suggesting circulation of rickettsial agents in the region. This is the first serological survey of this agent in horses from the north-central region of Bahia, and further studies are needed to understand the epidemiology of BSF in these locations.

Report of Amblyomma sculptum in a House in a Rickettsia rickettsii Circulation Area.

Amblyomma sculptum is a tick that has medical and veterinary importance as, in Brazil, it is the main vector of Rickettsia rickettsii, a disease affecting humans. The presence of ticks was observed outside a residence in a peri-urban area of the Atlantic Forest region in Brazil, as well as on two dogs that lived there. Eighteen A. sculptum adults were seen walking on a cemented pillar at the porch of the house and sheltering inside the pillar's crevices; meanwhile on the dogs, only Rhipicephalus sanguineus sensu lato ticks were found. It is hypothesized that as the dogs circulated in the forest regions, they might have carried A. sculptum to the residence. This situation highlights the role of dogs as possible carriers of Brazilian spotted fever (BSF) tick vectors into human habitation. Strategies for the prevention and control of BSF should consider the hypothesis that ticks infected with R. rickettsii can be harbored in human dwellings in peri-urban areas.

Capybara (Hydrochoerus hydrochaeris) exposure to Rickettsia in the Federal District of Brazil, a non-endemic area for Brazilian spotted fever / Exposição de capivaras (Hydrochoerus hydrochaeris) à Rickettsia no Distrito Federal, área não endêmica para febre maculosa brasileira

Abstract In this study, whole blood samples and ticks were collected from 57 capybaras in recreational areas in the Federal District, Brazil, aiming to investigate the presence of Rickettsia spp. using polymerase chain reaction (PCR) and indirect immunofluorescence (IFAT) assays. None of the capybara blood samples yielded rickettsial DNA by PCR. Among 55 capybara serum samples tested by IFAT, 53 (96.3%) reacted to Rickettsia spp. Among these, 21 (39.6%) identified the R. bellii antigen as the probable antigen involved in a homologous reaction (PAIHR), whereas 2 (3.8%) identified the R. parkeri antigen. Ticks collected from capybaras were identified as 173 Amblyomma sculptum and 410 A. dubitatum, in addition to nine Amblyomma spp. larvae. A sample of 231 ticks was subjected to DNA extraction and PCR for Rickettsia species. None of 122 A. sculptum yielded rickettsial DNA. Molecular evidence of R. bellii was found in 25/108 (23.1%) and of Rickettsia sp. strain Cooperi (R. parkeri-like agent) in 2/108 (1.9%) of the A. dubitatum samples. These results suggest a greater exposure to R. bellii in these capybara populations, in addition to a more significant number of A. dubitatum, which might characterize the Federal District region as not endemic for Brazilian spotted fever.

Resumo O presente trabalho realizou a coleta de amostras de sangue total e carrapatos de 57 capivaras da região, com o intuito de pesquisar bactérias do gênero Rickettsia spp., a partir de métodos de diagnóstico molecular (PCR) e sorológicos (RIFI). Nenhuma amostra de sangue das capivaras foi positiva na PCR. Dentre as 55 amostras de soro testadas por RIFI, 53 (96,3%) apresentaram soro-reação para Rickettsia spp. Dessas 53 amostras, 21 (39,6%) demonstraram o antígeno de R. bellii como provável antígeno envolvido em reação homóloga (PAERH); e duas (3,8%) demonstraram o antígeno de R. parkeri. Foram amostrados 173 carrapatos identificados como Amblyomma sculptum e 410 como Amblyomma dubitatum, além de nove larvas (Amblyomma spp.). Entre os carrapatos, 231 foram submetidos à extração de DNA e PCR para pesquisa de Rickettsia. Foram encontradas evidências moleculares de R. bellii em 25/108 (23,1%) e Rickettsia sp. "strain" Cooperi em 2/108 (1,9%) das amostras de A. dubitatum testadas. Os resultados sugerem uma maior exposição à R. bellii nas populações de capivaras da região, além de uma maior quantidade de carrapatos identificados como A. dubitatum. Isso pode estar relacionado ao que configura a região do Distrito Federal como não endêmica para a febre maculosa brasileira.

Serological evidence of Rickettsia in horses from a semi-arid Brazilian region / Evidência sorológica de Rickettsia em cavalos da região semiárida do Brasil

Abstract Brazilian spotted fever (BSF) is a common tick-borne disease caused by Rickettsia rickettsii. Horses are the primary hosts of the main vector, Amblyomma sculptum, and are considered efficient sentinels for circulation of Rickettsia. Therefore, the aim of this study was to detect antibodies reactive to R. rickettsii antigens in horses from a non-endemic area in the north-central region of Bahia state, Brazil. Blood samples and ticks were collected from 70 horses from the municipalities of Senhor do Bonfim, Antônio Gonçalves, Pindobaçu, and Campo Formoso. The sera obtained were tested by an indirect immunofluorescence assay to detect anti-Rickettsia antibodies. Overall, 5.7% (4/70) of the horses reacted to R. rickettsii antigens. Ticks were collected from 18.6% (13/70) of the horses and were identified as A. sculptum and Dermacentor nitens. Despite being a non-endemic area, seropositive animals were identified in our study, suggesting circulation of rickettsial agents in the region. This is the first serological survey of this agent in horses from the north-central region of Bahia, and further studies are needed to understand the epidemiology of BSF in these locations.

Resumo A Febre Maculosa Brasileira (FMB) é uma importante zoonose causada por Rickettsia rickettsii, sendo seu vetor o Amblyomma sculptum. Cavalos são os principais hospedeiros desse carrapato e considerados sentinelas eficientes para detectar a circulação de Rickettsia. O objetivo deste estudo foi detectar anticorpos reativos a antígenos de R. rickettsii em cavalos de uma área não-endêmica na região Centro-Norte da Bahia, Brasil. Foram coletadas amostras de sangue e carrapatos de 70 cavalos nos municípios de Senhor do Bonfim, Antônio Gonçalves, Pindobaçu e Campo Formoso. Os soros obtidos foram testados pela reação de imunofluorescência indireta para detectar anticorpos anti-Rickettsia. No geral, 5,7% (4/70) dos cavalos reagiram sorologicamente para antígenos de R. rickettsii. Os carrapatos foram coletados em 18,6% (13/70) dos cavalos e foram identificados como A. sculptum e Dermacentor nitens. Embora seja uma área não endêmica, foram observados animais soropositivos, sugerindo a circulação de riquétsias na região estudada. Este é o primeiro estudo de levantamento sorológico desse agente em cavalos do Centro-Norte da Bahia. São necessários mais estudos para compreender a epidemiologia da FMB nesses locais.

Rickettsial infection in equids, opossums and ticks in the municipality of Monte Mor, state of São Paulo, Brazil.

The aim of this study was to investigate rickettsial infection in equids, opossums and ticks in the municipality of Monte Mor, a place where a Brazilian spotted fever case occurred in 2005. In addition, characteristics possibly associated with seropositivity in horses were analyzed. Serum samples from horses, mules and opossums (Didelphis albiventris) were subjected to indirect immunofluorescence assay (IFA) against Rickettsia rickettsii. The ticks collected from the animals were identified and Amblyomma sculptum ticks from the equids were tested using PCR for Rickettsia spp. Anti-R. rickettsii antibodies were detected in 22.6% (14/62) of the horses, none of the mules and 21.7% (5/23) of the opossums. Among the variables analyzed, only age > 12 years showed a statistically significant association with seropositivity among horses. All of the 166 A. sculptum ticks tested using PCR were negative. The results showed that rickettsiae of the spotted fever group was circulating in the municipality of Monte Mor when the samples were collected and indicate a need for surveillance of Brazilian spotted fever in this region.

Serosurvey of arthropod-borne diseases among shelter dogs in the Cumberland Gap Region of the United States.

BACKGROUND: The Cumberland Gap Region (CGR) of the United States is a natural corridor between the southeastern, northeastern, and midwestern regions of the country. CGR has also many species of ticks and mosquitos that serve as competent vectors for important animal and human pathogens. In this study, we tested dogs from six different animal shelters in the CGR for Rocky Mountain spotted fever (RMSF), anaplasmosis, Lyme disease, canine ehrlichiosis and canine heartworm disease. RESULTS: Sera from 157 shelter dogs were tested for antibodies to RMSF agent, Rickettsia rickettsii, using an indirect immunofluorescence assay. Sixty-six dogs (42.0%) were positive for either IgM or IgG, or both IgM and IgG antibodies to R. rickettsii. Moreover, the same set of sera (n = 157) plus an and additional sera (n = 75) from resident dogs at the same shelters were tested using the SNAP 4Dx Plus. Of 232 dogs tested, two (0.9%) were positive for antibodies to Anaplasma phagocytophilum/A. platys, nine (3.9%) were positive for antibodies to Borrelia burgdorferi, 23 (9.9%) for positive for antibodies to Ehrlichia canis/E. ewingii, and 13 (5.6%) were positive for Dirofilaria immitis antigen. Co-infection with two or more etiologic agents was detected in five animals. Three dogs had antibodies to both B. burgdorferi and E. canis/E. ewingii, and two dogs were positive for D. immitis antigen and antibodies to B. burgdorferi and E. canis/E. ewingii. CONCLUSIONS: Shelter dogs in the CGR are exposed to a number of important vector-borne pathogens. Further studies are required to ascertain the roles these animals play in maintenance and transmission of these pathogens.

An exploratory analysis of demography and movement patterns of dogs: New insights in the ecology of endemic Rocky Mountain-Spotted Fever in Mexicali, Mexico.

An outbreak of Rocky Mountain spotted fever (RMSF) transmitted by the brown dog tick (Rhipicephalus sanguineus sensu lato) has emerged as a major human and animal health concern in Mexicali, Mexico. Due to high rates of brown dog tick infestation, susceptibility, and association with humans, dogs serve as sentinels and have a key role in the ecology of RMSF. A cross-sectional household questionnaire study was conducted in six rural and urban locations to characterize dog ecology and demography in RMSF high-and low-risk areas of Mexicali. In addition, we tracked movement patterns of 16 dogs using a GPS data logger. Of 253 households, 73% owned dogs, and dog ownership tended to be higher in high-risk areas, with a mean dog:human ratio of 0.43, compared with 0.3 in low-risk areas. Dogs in high-risk areas had higher fecundity and roamed more, but the dog density and numbers of free-roaming dogs were comparable. There was a higher proportion of younger dogs and lower proportion of older dogs in high-risk areas. The high proportion of immunologically naïve puppies in high risk areas could result in a lack of herd immunity leading to a more vulnerable dog and human population. The marked increase of space use of free-roaming dogs in high-risk areas suggests that unrestrained dogs could play an important role in spreading ticks and pathogens. As means to limit RMSF risk, practical changes could include increased efforts for spay-neuter and policies encouraging dog restraint to limit canine roaming and spread of ticks across communities; due to dog density is less impactful such policies may be more useful than restrictions on the number of owned dogs.