Experimental infection of capybaras Hydrochoerus hydrochaeris by Rickettsia rickettsii and evaluation of the transmission of the infection to ticks Amblyomma cajennense

Sterilization of free-ranging female capybaras (Hydrochoerus hydrochaeris): a comparison between two surgical techniques

This study evaluated two surgical sterilization techniques in free-ranging female capybaras (n = 21). The first group underwent uterine horn ligature (HL; n = 11), while the second was subjected to partial salpingectomy (S; n = 10). We assessed total operative time, incision length, the ease of identifying reproductive structures, the adequacy of exposure for surgical performance through flank or midline approaches, and the extent of abdominal viscera manipulation for each method. The HL method emerged as faster, with an average operative time difference of 16 minutes. In the S group, a flank mini-laparotomy over the ovarian topography facilitated easy exposure of the ipsilateral ovary and uterine tube, enabling ligature and partial resection of the uterine tube but not the uterine horn exposure. However, accessing the contralateral uterine tube without a bilateral incision was impractical, thus prolonging the total operative time due to the need for patient repositioning and new antisepsis procedures. Conversely, a post-umbilical approach for the HL method necessitated only one mini-laparotomy incision, offering ample uterine exposure for hysterotomy in pregnant females. Both methods involved minimal abdominal viscera manipulation and resulted in no fatalities or postoperative complications. Although direct comparison is limited by the distinct sterilization techniques and surgical approaches, this study underscores the challenges and surgical access of each method. Our findings endorse the HL technique as an effective contraception method for female capybaras to prevent the birth of seronegative offspring that could amplify Rickettsia sp., the causative agent of Brazilian spotted fever.

Spotted Fever Group Rickettsia spp. Molecular and Serological Evidence among Colombian Vectors and Animal Hosts: A Historical Review

Spotted fever group Rickettsia spp. (SFGR) are a large group of tick-borne bacteria causing important emerging and re-emerging diseases that affect animals and humans. While SFGR are found worldwide, a lack of surveillance and misdiagnosis particularly affect South American countries. Colombia is a high burdened country in South America, yet rickettsioses are not deemed a nationally reportable condition limiting disease-specific public health resources. As mortality rates are high for one Rickettsia pathogen species, there is a great need to better understand the epidemiological and ecological factors that increase SFGR transmission risk regionally. This literature review provides an overview of Colombia-based SFGR studies connecting knowledge about both vectors and hosts.

First report of Amblyomma sculptum (Amblyomma cajennense complex) in a Brazilian state classified as a silent area for human rickettsiosis

Background and Aim

Studies on ticks of public health concern in equine husbandry are scarce in the Northeastern region of Brazil. This study aimed to investigate the presence of ticks on horses in the State of Alagoas, which is classified as a silent area for human rickettsiosis.

Materials and Methods

Ticks infesting horses were collected using anatomical tweezers or a commercial hook and kept in ethanol-labeled tubes for taxonomic identification.

Results

A total of 2,238 ticks were found. Ticks were identified as 2,215 (98.89%, 95% CI: 98.41-99.28) Dermacentor nitens, 19 (0.98%, 95% CI: 0.05-1.38) Amblyomma sculptum, and 4 (0.18%; 95% CI: 0.007-0.46) Rhipicephalus microplus.

Conclusion

This is the first study to report A. sculptum and D. nitens in the State of Alagoas. The presence of A. sculptum should draw the attention of public health managers once Alagoas State is considered a silent area for rickettsial diseases, which means the absence of local surveillance programs for these pathogens.

Detection of Rickettsia spp. in Animals and Ticks in Midwestern Brazil, Where Human Cases of Rickettsiosis Were Reported

Brazilian spotted fever (BSF) is the most important tick-borne diseases affecting humans in Brazil. Cases of BSF have recently been reported in the Goiás state, midwestern Brazil. All cases have been confirmed by reference laboratories by seroconversion to Rickettsia rickettsii antigens. Because serological cross-reactions among different rickettsial species that belong to the spotted fever group (SFG) are common, the agent responsible for BSF cases in Goiás remains unknown. From March 2020 to April 2022, ticks and plasma were collected from dogs, horses and capybaras (Hydrochoerus hydrochaeris), and from the vegetation in an area where BSF cases have been reported and two areas under epidemiological surveillance in Goiás. Horses were infested by Amblyomma sculptum, Dermacentor nitens and Rhipicephalus microplus; dogs by Rhipicephalus sanguineus sensu lato (s.l.), Amblyomma ovale and A. sculptum, and capybaras by A. sculptum and Amblyomma dubitatum. Adults of A. sculptum, A. dubitatum, Amblyomma rotundatum and immature stages of A. sculptum and A. dubitatum, and Amblyomma spp. were collected from the vegetation. DNA of Rickettsia that did not belong to the SFG was detected in A. dubitatum, which was identified by DNA sequencing as Rickettsia bellii. Seroreactivity to SFG and Rickettsia bellii antigens was detected in 25.4% (42/165) of dogs, 22.7% (10/44) of horses and 41.2% (7/17) of capybaras, with higher titers for R. bellii in dogs and capybaras. The seropositivity of animals to SFG Rickettsia spp. antigens demonstrates the circulation of SFG rickettsiae in the region. Further research is needed to fully determine the agent responsible for rickettsiosis cases in this area.

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.

A systems biology approach to better understand human tick-borne diseases

Tick-borne diseases (TBDs) are a growing global health concern. Despite extensive studies, ill-defined tick-associated pathologies remain with unknown aetiologies. Human immunological responses after tick bite, and inter-individual variations of immune-response phenotypes, are not well characterised. Current reductive experimental methodologies limit our understanding of more complex tick-associated illness, which results from the interactions between the host, tick, and microbes. An unbiased, systems-level integration of clinical metadata and biological host data - obtained via transcriptomics, proteomics, and metabolomics - offers to drive the data-informed generation of testable hypotheses in TBDs. Advanced computational tools have rendered meaningful analysis of such large data sets feasible. This review highlights the advantages of integrative system biology approaches as essential for understanding the complex pathobiology of TBDs.

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.

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.

Capybara Ticks and the Urban Context of Spotted Fever in Brazil: An Overview

Spotted fever is caused by Rickettsia rickettsii and is transmitted through tick’s saliva. Humans, ticks, and capybaras (Hydrochoerus hydrochaeris) are often coexisting in environments that favor the spread of Brazilian spotted fever (BSF). Although capybaras do not transmit R. rickettsii, they can amplify these bacteria among tick vector populations, playing a significant role in the one health approach and epidemiology of the disease. Urban populations of capybaras have increased, especially in Southeast Brazil, as well as the number of cases and lethality of BSF have increased in the country since the 1980s. This expansion is mainly determined by the availability of food and the absence of predators. Thus, urban areas, including parks and university campuses, provide an abundance of food and protection against predators, ensuring the multiplication of the species and increasing the risk of transmission to humans due to the proximity of man with animals in the urban environment. Therefore, this chapter aims to address aspects of spotted fever, considering the many dimensions of the species involved, contributing to public strategies and policies.

Diversity of tick species (Acari: Ixodidae) in military training areas in Southeastern Brazil

Tick-borne pathogens belong to one of the two main groups of occupational biohazards, and occupational exposure to such agents puts soldiers at risk of zoonotic infections, such as those caused by rickettsiae. There are few studies on acarological fauna and occupational risk in military areas in Brazil. Thus, the present study aimed to analyze the diversity of ticks present in the military training areas of municipalities in the Southeast Region of Brazil. The ticks were collected from the selected areas using the dragging and flagging techniques as well as by visual detection on the operators' clothing, and environmental information was also recorded. A total of ten species were collected from the 66 surveyed areas, belonging to five genera and nine species: Amblyomma sculptum, Amblyomma dubitatum, Amblyomma brasiliense, Amblyomma longirostre, Amblyomma aureolatum, Dermacentor nitens, Rhipicephalus spp., Ixodes spp. and Haemaphysalis spp. The frequent presence of tick species in military training areas along with traces and sightings of wild animals, most commonly capybaras (Hydrochoerus hydrochaeris), in most of the studied areas, indicates high levels of exposure of the military to tick vectors of spotted fever group rickettsiae and the possible occurrence of infections among the troops.

Association between Growth Rate and Pathogenicity of Spotted Fever Group Rickettsia

Rickettsia parkeri and Rickettsia amblyommatis are spotted fever group Rickettsia (SFGR) associated with Amblyomma ticks. R. parkeri is a recognized human pathogen that causes an eschar-associated febrile illness, while R. amblyommatis has not been confirmed as a causative agent of human disease. We hypothesized that the rate of replication is one of the factors contributing to rickettsial pathogenicity. In this study, growth and infectivity of R. parkeri and R. amblyommatis in mammalian (Vero E6) and tick-derived (ISE6) cell lines were assessed and compared over a 96-hour time course of infection using quantitative real-time polymerase chain reaction and microscopy. The pathogenic R. parkeri displayed a significantly higher level of infection in both Vero E6 and ISE6 cells than R. amblyommatis at 72 hours post-inoculation (hpi). Distinct growth profiles between rickettsial species with known and uncertain pathogenicity were identified. R. parkeri burdens were significantly greater than those of R. amblyommatis from 24 to 96 hpi. The relative fold changes of load were significantly higher in the pathogenic agent than in R. amblyommatis from 48 hpi onward and reached the maximum fold increase of ~2002- and ~296-fold in Vero E6 cells and ~1363- and ~161-fold in ISE6 cells, respectively, at 96 hpi. The results from the present study demonstrate that growth rate is associated with the pathogenicity of rickettsiae. Understanding SFGR growth characteristics in mammalian and tick cells will provide insight into rickettsial biology and pathogenesis.

Surgical sterilization of free-ranging capybaras (Hydrochoerus hydrochaeris): “Passos Nunes” uterine horn ligature

Capybaras are the primary hosts of Amblyomma sculptum tick, vectors of Rickettsia rickettsia bacteria, and the zoonotic agent of Brazilian Spotted Fever (BSF). In this context, contraceptive methods have been suggested for population control in order to reduce the number of free-ranging capybaras cohabiting with humans in urban and rural areas and acting as disease amplifiers. To maintain the group's expected behavior and social hierarchy, sterilization techniques that preserve the gonads are recommended. On 126 female capybaras in the Brazilian state of São Paulo, a new surgical technique named “Passos Nunes” uterine horn ligature was performed after adequate general anesthesia. It achieved effective surgical sterilization, with an incision length of about 3 cm in the periumbilical linea alba, cranial to the pubis. After entering the abdominal cavity, the urinary bladder is pulled laterally to access the uterine horns and the cervix. The uterine horn is folded up, forming a strap; the distal portion of the strap is ligated and its distal end sectioned. The exact process is performed on the opposite horn. After the surgical procedure, the musculature is sutured in a sultan pattern and the subcutaneous tissue with a horizontal mattress pattern. The skin is sutured in a separate simple format, using nylon 2.0 for all steps. The wide exposure of the uterine horns facilitates the confirmation of pregnancy, allowing the surgeon to choose between salpingo hysterectomy or ligature of the uterine horns. The present study presents a new technique of surgical sterilization that can be used in female free-ranging mammals in which maintenance of the gonads is recommended, and births of offspring should not occur.

Rickettsial infection in free-ranging capybaras (Hydrochoerus hydrochaeris) and their ticks (Acari, Ixodidae) in the Caatinga and Atlantic forest biomes, Northeastern Brazil

Caatinga and Atlantic Forest are Brazilian biomes threatened by anthropogenic disturbances, which are a serious threat to biodiversity and favor the emergence of zoonotic pathogens. Capybara populations are increasingly present in urban and rural areas due to the loss of their natural habitats. There are no studies on the rickettsial infection in these rodents in Northeastern Brazil, although there are case records of Brazilian Spotted Fever (BSF) in this region. In this context, we evaluated rickettsial infection in capybaras and their ticks in four areas of the Atlantic Forest and Caatinga biomes in Northeastern Brazil. Blood sera from 21 capybaras were tested by indirect immunofluorescence assay (IFA) using Rickettsia rickettsii, R. parkeri, and R. amblyommatis antigens. Blood samples and ticks (Amblyomma sp., Amblyomma dubitatum and Amblyomma sculptum) were tested by PCR, targeting a fragment of the rickettsial gltA gene and R. bellii primers. Overall, 15 out of 21 capybaras (71.4%) reacted positively (titer ≥64) to at least one of the three Rickettsia antigens tested, with final titers ranging from 64 to 1024. No rickettsial DNA was found in capybara blood samples. Rickettsial DNA was detected in 22 of 31 adult tick pools using gltA gene, being all nine pools of A. sculptum and 16 of the 19 of A. dubitatum, but all samples were negative to R. bellii specific primers. All attempts to sequence the amplicon were unsuccessful, indicating a possible low rickettsial load in the tick samples. The present study reports for the first time the serological evidence of Rickettsia spp. infection in free-ranging capybaras and suggest the rickettsial infection in A. sculptum and A. dubitatum in the Caatinga and Atlantic Forest biomes in Northeastern Brazil.

Tick-borne zoonotic agents infecting horses from an urban area in Midwestern Brazil: epidemiological and hematological features

The emergence of tick-borne diseases has been reported as a serious problem in public health worldwide and many aspects of its epidemiology and effects on the health of its hosts are unclear. We aimed to perform an epidemiological study of tick-borne zoonotic Rickettsia, Borrelia, and Anaplasmataceae in horses from Midwestern Brazil. We also evaluated whether Borrelia spp. and Anaplasmataceae may be associated with hematological disorders in the sampled animals. Blood and serum samples as well as ticks were collected from 262 horses. Serum samples were used to perform serological tests, and hematological analyses were made using whole blood. Furthermore, DNA extracted from whole blood and ticks was used for molecular tests. Campo Grande is enzootic for tick-borne studied bacteria, since we found an overall exposure of 59.9% of the sampled horses, 28.7% of them presented co-exposure. Seropositivity rates of 20.6% for Borrelia spp., 25.6% for Rickettsia spp., and 31.6% for Anaplasmataceae were found in the sampled horses. Considering both molecular and serological tests for Borrelia spp., the infection rate was 48.0% (126/262). None of the tested horses showed molecular positivity for Anaplasma phagocytophilum. The horses sampled displayed 7.2% of parasitism by ixodid ticks in single and coinfestations. We did not find DNA of any studied bacteria in the sampled ticks. Positive horses for Borrelia spp. and Anaplasmataceae agents displayed leukopenia, monocytopenia, and lymphopenia. Together, our results suggest that horses may play a role as sentinel host for zoonotic bacteria and Borrelia spp. and Anaplasmataceae agents can impair the health of horses.

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.

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.

Endoparasites of capybaras (Hydrochoerus hydrochaeris) from anthropized and natural areas of Brazil

This study aimed to evaluate the occurrence of endoparasites in fecal samples of capybaras from anthropized areas in seven cities in the state of São Paulo, southeastern Brazil, and natural areas in two locations in the Pantanal biome. For the parasitological evaluation of samples, feces were subjected to centrifugal sedimentation in water-ether and centrifugal flotation in sucrose solution. Out of the 113 samples examined, 97.3% (110/113) were positive for the presence of helminth eggs and/or protozoan oocysts, with 96.7% (89/92) and 100% (21/21) in capybaras from anthropized and natural areas, respectively. Helminth eggs belonging to the Class Cestoda (Monoecocestus spp.), Class Digenea, and Class Nematoda (Trichostrongyloidea, Strongyloides chapini, Protozoophaga obesa, and Capillaria hydrochoeri) were detected. Coccidia oocysts of Eimeria spp. and Cryptosporidium spp. were detected. The difference found was in the occurrence of S. chapini between anthropized and natural areas, as S. chapini was not detected in natural areas. Capybaras from anthropized areas showed a greater species richness of endoparasites, including species such as Fasciola hepatica and Cryptosporidium spp., that might have zoonotic potential.

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.

Parasites and health status of free-ranging capybaras (Hydrochoerus hydrochaeris) in the Atlantic Forest and Caatinga biomes of Brazil

Due to the degradation and loss of its natural habitat, the presence of capybaras in urban environments and crop areas has been frequently reported in various regions of Brazil. The objective of this study was to identify the parasitic fauna of free-living capybaras in two impacted biomes of the northeastern region (Atlantic Forest and Caatinga), as well as to evaluate the impact of parasitism on the health of these rodents. For this, ticks, fecal and blood samples (for hematology and serum biochemistry evaluation) were collected from 23 free-ranging capybaras from four areas of Atlantic Forest (areas 1, 2 and 3) and Caatinga (area 4) biomes. Of the 23 animals with parasites, 73.9% (17/23) were parasitized simultaneously by gastrointestinal parasites (GIP) (Strongylida, Strongyloides chapini, Capillaria sp., Trematoda and Eimeria sp.) and Amblyomma ticks (larvae of Amblyomma sp. - areas 1, 2, and 3; Amblyomma dubitatum - areas 1 and 2; A. sculptum - areas 3 and 4), while 26.1% (6/23) were parasitized exclusively by ticks. The trematode Hippocrepis hippocrepis was collected during the necropsy of one animal that died during the study. Most hematological and serum biochemical parameters were within the reference values for the species, except AST, albumin, urea, and Na, which presented higher values. Some parameters presented statistically significant differences associated with parasitism, with higher values for animals with co-infection (GIP and ticks) than animals parasitized by ticks only: leukocyte counts (p = 0.0332), neutrophils (p = 0.0498), monocytes (p = 0.0443), as well as creatinine (p = 0.0422) and lactate (p = 0.0307). This may mean that the GIP identified in this study can have a greater impact on the hematological and serum biochemical parameters. However, although parasitized and living in threatened biomes, the animals were healthy, demonstrating that they could be adapted to parasitism. Amblyomma sculptum was recorded for the first time in capybaras in the Caatinga biome in Pernambuco state. The presence of A. sculptum evidences the need for studies about the infection by Rickettsia on capybaras and their ticks, to provide data on the potential risk of occurrence of Brazilian Spotted Fever in Pernambuco state, within a One Health perspective.

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.

Detecção de anticorpos anti-Rickettsia rickettsii em cães residentes em área negligenciada no município de São Paulo, SP, Brasil

RESUMO A febre maculosa brasileira (FMB), descrita inicialmente nos Estados Unidos como febre maculosa das Montanhas Rochosas, é uma antropozoonose relatada apenas no continente americano e causada pela bactéria Rickettsia rickettsii. No Brasil a transmissão ocorre sobretudo pela picada de carrapatos do gênero Amblyomma spp. A doença foi inicialmente descrita como de transmissão em áreas rurais e silvestres, no entanto áreas periurbanas e urbanas vêm apresentando casos, principalmente relacionados com a presença de humanos residindo em pequenos fragmentos de mata ciliar. O presente estudo teve por objetivo elucidar a dispersão da FMB nas proximidades dos reservatórios Guarapiranga e Billings, na cidade de São Paulo, SP. Para tanto, a presença de anticorpos anti-R. rickettsii, Rickettsia parkeri e Rickettsia bellii foi avaliada em cães atendidos nas campanhas de esterilização cirúrgica e residentes ao redor dos reservatórios. Foram coletadas amostras de 393 cães, e as amostras de soro foram analisadas pela reação de imunofluorescência indireta (RIFI), com ponto de corte de 1:64. Os títulos para R. rickettsii variaram de 256 a 4096, com positividade de 3,3% (13/393); para R. bellii, de 128 a 1024 e 4,1% (16/393) de positivos, e um único animal (0,25%) foi soropositivo para R. parkeri, com título de 128. Os achados permitem concluir que a região de estudo apresenta condições de se tornar uma possível área com casos de FMB, pois comporta fragmentação de Mata Atlântica, condições essas ideais para a manutenção do vetor do gênero Amblyomma já descrito na região, bem como para a presença da Rickettsia rickettsii circulante entre os cães, confirmada pela existência de anticorpos. Condutas referentes à conscientização da população por meio de trabalhos educacionais devem ser implantadas para a prevenção da doença na população da área.

Molecular detection of vector-borne agents in ectoparasites and reptiles from Brazil

Trombidiformes and Mesostigmata mites, as well as Ixodida ticks, infest ectothermic tetrapods worldwide, potentially acting as vectors of bacteria, viruses and protozoa. The relationship among ectoparasites, transmitted pathogenic agents (e.g., Borrelia spp., Coxiella spp., Hepatozoon spp., and Rickettsia spp.) and ectothermic hosts has been scarcely investigated. This research focuses on a large collection of Brazilian herpetofauna screened for the presence of arthropod ectoparasites and vector-borne microbial agents. Reptiles (n = 121) and amphibians (n = 49) from various locations were infested by ectoparasites. Following genomic extraction, microbial agents were detected in 81 % of the Acari (i.e. n = 113 mites and n = 26 ticks). None of the mites, ticks and tissues from amphibians yielded positive results for any of the screened agents. Blood was collected from reptiles and processed through blood cytology and molecular analyses (n = 48). Of those, six snakes (12.5 %) showed intraerythrocytic alterations compatible with Hepatozoon spp. gamonts and Iridovirus inclusions. Hepatozoon spp. similar to Hepatozoon ayorgbor and Hepatozoon musa were molecularly identified from seven hosts, two mite and two tick species. Rickettsia spp. (e.g., Rickettsia amblyommatis, Rickettsia bellii-like, Rickettsia sp.) were detected molecularly from four mite species and Amblyomma rotundatum ticks. Phylogenetic analyses confirmed the molecular identification of the above-mentioned microbial agents of mites and ticks related to snakes and lizards. Overall, our findings highlighted that the Brazilian herpetofauna and its ectoparasites harbour potentially pathogenic agents, particularly from the northern and south-eastern regions. The detection of several species of spotted fever group Rickettsia pointed out the potential role of ectothermic hosts and related arthropod ectoparasites in the epidemiological cycle of these bacteria in Brazil.

Habitat selection in natural and human-modified landscapes by capybaras (Hydrochoerus hydrochaeris), an important host for Amblyomma sculptum ticks

Human activities are changing landscape structure and function globally, affecting wildlife space use, and ultimately increasing human-wildlife conflicts and zoonotic disease spread. Capybaras (Hydrochoerus hydrochaeris) are linked to conflicts in human-modified landscapes (e.g. crop damage, vehicle collision), as well as the spread and amplification of Brazilian spotted fever (BSF), the most human-lethal tick-borne disease in the world. Even though it is essential to understand the link between capybaras, ticks and BSF, many knowledge gaps still exist regarding the effects of human disturbance in capybara space use. Here, we analyzed diurnal and nocturnal habitat selection strategies of capybaras across natural and human-modified landscapes using resource selection functions (RSF). Selection for forested habitats was higher across human-modified landscapes, mainly during day- periods, when compared to natural landscapes. Across natural landscapes, capybaras avoided forests during both day- and night periods. Water was consistently selected across both landscapes, during day- and nighttime. Distance to water was also the most important variable in predicting capybara habitat selection across natural landscapes. Capybaras showed slightly higher preferences for areas near grasses/shrubs across natural landscapes, and distance to grasses/shrubs was the most important variable in predicting capybara habitat selection across human-modified landscapes. Our results demonstrate human-driven variation in habitat selection strategies by capybaras. This behavioral adjustment across human-modified landscapes may be related to increases in A. sculptum density, ultimately affecting BSF.

Mapping Brazilian spotted fever: Linking etiological agent, vectors, and hosts

Brazilian spotted fever (BSF) is a highly lethal disease in southeastern Brazil. BSF is caused by the bacterium Rickettsia rickettsii and is transmitted by the bites of the tick of the genus Amblyomma. The spatial distribution of BSF risk areas is not well known in the country given the complexity of the transmission cycle. This study used the ecological niche modeling (ENM) approach to anticipate the potential distribution of the etiological agent (Rickettsia rickettsii), vectors (Amblyomma sculptum and A. dubitatum), and hosts (Hydrochoerus hydrochaeris, Didelphis aurita, and D. marsupialis) of BSF in Brazil. We compiled occurrence records for all vectors, hosts, and BSF from our own field surveillance, online repositories, and literature. ENM identified BSF risk areas in southeastern and southern Brazil, and anticipated other dispersed suitable areas in the western, central, and northeastern coast regions of Brazil. Tick vectors and mammalian hosts were confined to these same areas; however, host species showed broader suitability in northern Brazil. All species ENMs performed significantly better than random expectations. We also tested the BSF prediction based on 253 additional independent cases identified in our surveillance; the model anticipated 251 out of 253 of these independent cases. Background similarity tests comparing the ENMs of R. rickettsii, tick vectors, and mammalian hosts were unable to reject null hypotheses of niche similarity. Finally, we observed close coincidence between independent BSF cases, and areas suitable for combinations of vectors and hosts, reflecting the ability of these model pairs to anticipate the distribution of BSF cases across Brazil.

Capybaras (Hydrochoerus hydrochaeris) as amplifying hosts of Rickettsia rickettsii to Amblyomma sculptum ticks: Evaluation during primary and subsequent exposures to R. rickettsii infection

Rickettsia rickettsii is the agent of Brazilian spotted fever (BSF), the most lethal tick-borne disease in the western hemisphere. Amblyomma sculptum is the main vector of R. rickettsii in southeastern Brazil. Capybaras act as primary hosts for this tick species, and as amplifying hosts for R. rickettsii, creating new infected lineages of A. sculptum in BSF-endemic areas. In a recent study, we demonstrated that capybaras successively exposed to R. rickettsii-infected A. sculptum ticks developed a mean rickettsemic period of 9.2 days during primary infection, but no rickettsemia during subsequent expositions, when capybaras were immune to R. rickettsii. During the primary and subsequent infections, capybaras were also infested with uninfected A. sculptum ticks. These infestations compose the present study, which aimed to evaluate: (i) if either rickettsemic or non-rickettsemic capybaras could serve as infection sources of R. rickettsii for A. sculptum larvae and nymphs; (ii) the vector competence of the subsequent nymphs and adults (molted from the engorged ticks collected from capybaras); and (iii) if there were R. rickettsii-acquisition by uninfected ticks co-feeding with infected ticks on immune capybaras (without rickettsemia). Through experimental infection of capybaras with R. rickettsii via tick feeding, simulating a natural condition, we demonstrated that primarily infected capybaras developed rickettsemia that resulted in successful acquisition feeding of larvae and nymphs of A. sculptum, since part of these ticks maintained R. rickettsii transstadially, and the resultant molted ticks (either nymphs or adults) successfully transmitted the bacterium by feeding on susceptible rabbits. Contrastingly, all rabbit infestations with ticks derived from acquisition feeding on R. rickettsii-immune capybaras (including when acquisition ticks fed in direct contact with donor ticks) evidenced absence of R. rickettsii transmission due to lack of clinical signs and antibody response in those rabbits. Our results indicate that capybaras could serve as R. rickettsii-amplifying hosts for A. sculptum ticks only during the capybara's primary infection, but not during subsequent infections on immune capybaras. Finally, the probable co-feeding nonsystemic transmission of R. rickettsii seems to be irrelevant in the context of BSF epidemiology, in areas where capybaras are incriminated as main amplifying hosts of R. rickettsii for A. sculptum ticks.

Prevalence of plasmodium, leptospira and rickettsia species in Northern Tanzania: a community based survey

BACKGROUND

The overlap of symptoms, geographic and seasonal co-occurrence of Plasmodium, Leptospira and Rickettsia infections makes malaria diagnosis difficult, increasing the chances of misdiagnosis. The paucity of data on the prevalence Plasmodium, Leptospira and Rickettsia infections contributes to an overly diagnosis of malaria. We aimed to determine the prevalence and distribution of Plasmodium, Leptospira and Rickettsia infections in northern Tanzania.

METHODS

A community based, cross sectional survey was conducted in two sites in Northern Tanzania. PCR was used to detect Plasmodium, Leptospira and Rickettsia infections.

RESULTS

The prevalence of P. falciparum and Leptospira spp were 31/128 (24.2%) and 3/128 (2.3%), respectively. No Rickettsia infection was detected in any of the two sites. Taking study sites separately, Plasmodium infection was detected in 31/63(49.2%) of participants in Bondo while Leptospira infection was detected in 3/65(4.6%) of participants in Magugu. Plasmodium was not detected in Magugu while no Leptospira infections were detected in Bondo. Fever was significantly associated with Plasmodium infection (χ2= 12.44, p<0.001) and age (χ2=17.44, p=0.000).

CONCLUSION

Results from this study indicate Plasmodium infection as the main cause of fever in the studied sites. While Plasmodium and Leptospira contribute to fevers, Rickettsia infection is an insignificant cause of fever in Northern Tanzania.

Serosurvey of Rickettsia spp. in cats from a Brazilian spotted fever-endemic area

Rickettsia spp. bacteria are responsible for tick-borne diseases worldwide, mostly maintained by rickettsial amplifiers capybaras in Brazilian endemic areas. The campus of the University of São Paulo, in southeastern Brazil, is an area endemic for Brazilian spotted fever (BSF), with high density of capybaras and Amblyomma spp., along with confirmed human cases. Besides capybaras, the university has also an in-campus high population of sheltered and free-roaming cats. Accordingly, the aim of this study was to determine the prevalence and characteristics associated with Rickettsia rickettsii, Rickettsia parkeri and Rickettsia felis exposure among cats in a BSF-endemic area. Out of 51 cats sampled, 23/35 shelter (65.7%) and 5/16 free-roaming (31.2%) were positive (titers ≥ 64) for at least one Rickettsia species. Ticks species were present in 3/16 free-roaming cats (18.8%), consisting of Amblyomma spp., nymphs of Amblyomma sculptum and adult Rhipicephalus sanguineus sensu lato. Despite sharing the capybaras environment, the seropositivity among the free-roaming and shelter cats was lower than owned cats in other endemic areas. Whether equally or less exposed to rickettsial infection, compared with owned cats in endemic areas, free-roaming and shelter cats may be used as environmental sentinels for human exposure to rickettsiae in such areas.

Clinical and serological evaluation of capybaras (Hydrochoerus hydrochaeris) successively exposed to an Amblyomma sculptum-derived strain of Rickettsia rickettsii

Brazilian spotted fever (BSF), caused by Rickettsia rickettsii, is the most lethal tick-borne disease in the western hemisphere. In Brazil, Amblyomma sculptum ticks are the main vector. Capybaras (Hydrochoerus hydrochaeris), the largest living rodents of the world (adults weighing up to 100 Kg), have been recognized as amplifying hosts of R. rickettsii for A. sculptum in BSF-endemic areas; i.e., once primarily infected, capybaras develop bacteremia for a few days, when feeding ticks acquire rickettsial infection. We conducted experimental infections of five capybaras with an A. sculptum-derived strain of R. rickettsii and performed clinical and bacteremia evaluation during primary and subsequent infections. Bacteremia was detected in all capybaras during primary infection, but not in subsequent infections. All animals seroconverted to R. rickettsii (titres range: 64-32,768), and remained seropositive throughout the study. Primary infection resulted in clinical spotted fever illness in four capybaras, of which two had a fatal outcome. Subsequent infections in seropositive capybaras resulted in no clinical signs. Capybaras developed a sustained immune response that prevented a second bacteremia. This condition may imply a high reproduction rate of capybaras in BSF-endemic areas, in order to continuously generate capybaras susceptible to bacteremia during primary infection.

Rickettsia rickettsii (Rickettsiales: Rickettsiaceae) Infecting Amblyomma sculptum (Acari: Ixodidae) Ticks and Capybaras in a Brazilian Spotted Fever-Endemic Area of Brazil

The bacterium Rickettsia rickettsii is the agent of Brazilian spotted fever (BSF), a highly fatal disease that is transmitted in Brazil mainly by the tick Amblyomma sculptum Berlese, which uses capybaras (Hydrochoerus hydrochaeris Linnaeus) as major hosts. In 2015, we captured nine capybaras in a BSF-endemic area of southeastern Brazil. From each capybara, we collected blood sera that were tested through the immunofluorescence assay using Rickettsia spp. antigens, and A. sculptum ticks, processed for isolation of R. rickettsii through guinea pig inoculation. All capybaras (100%) were seroreactive to Rickettsia spp., with highest titers to R. rickettsii. A total of 166 A. sculptum ticks were macerated and inoculated into nine guinea pigs, from which only one presented high fever and seroconverted to R. rickettsii. Blood from this febrile animal was inoculated into additional guinea pigs (guinea pig passages), which also became febrile and seroconverted, or when euthanized during the fever period, their internal organs (spleen, lung) were shown to contain R. rickettsii DNA. The present rickettsial isolate has been maintained cryopreserved as infected guinea pig organs. There was at least one R. rickettsii-infected tick among the 166 macerated ticks, giving a minimal infection rate of 0.6% (1/166). This infection rate is within the range of previous studies, which reported that only 0.05% to at most 1.28% A. sculptum ticks were infected by R. rickettsii in other BSF-endemic areas. These low infection rates support the low incidence of BSF, despite of A. sculptum being the most frequent human-biting tick in southeastern Brazil.

Experimental infection of Monodelphis domestica with Rickettsia parkeri

This study aimed to evaluate the infection of the marsupial Monodelphis domestica (the gray short-tailed opossum) by Rickettsia parkeri and its role as an amplifier of the bacterium for Amblyomma ticks. Ten M. domestica males were inoculated with phosphate-buffered saline (PBS) and 10⁶ Vero cells infected with R. parkeri. In seven animals, inoculation was intramuscular, and in three intraperitoneal. One male (control) received 1 ml of the same vehicle used for inoculation intraperitoneally. The three animals inoculated intraperitoneally were infested with uninfected A. sculptum larvae and nymphs between the 2^nd and 9^th day post-infection (DPI). Parasitemia was monitored from the 3^rd to 9^th DPI by polymerase chain reaction, using primers for 17 kDa and ompA. The animals were also clinically evaluated. Of the animals infected intramuscularly, only one was blood-positive by the 5th DPI. The three animals infected intraperitoneally were blood-positive on the 2nd, 5th, 7th, and 9th DPI. Of the ten pools of recovered engorged ticks, six had positive bands. The kidney, liver, heart, and spleen of an intramuscularly infected animal were also positive. The rectal temperature of the animals tested increased only in the first three DPI. The animals inoculated intraperitoneally showed prostration, bristled hair, and weight loss. The study found that R. parkeri was capable of infecting M. domestica, which developed rickettsemia and caused infection in xenodiagnostic ticks.

Epidemiology of capybara-associated Brazilian spotted fever

Background

Brazilian spotted fever (BSF), caused by the bacterium Rickettsia rickettsii, has been associated with the transmission by the tick Amblyomma sculptum, and one of its main hosts, the capybara (Hydrochoerus hydrochaeris).

Methods

During 2015–2019, we captured capybaras and ticks in seven highly anthropic areas of São Paulo state (three endemic and four nonendemic for BSF) and in two natural areas of the Pantanal biome, all with established populations of capybaras.

Results

The BSF-endemic areas were characterized by much higher tick burdens on both capybaras and in the environment, when compared to the BSF-nonendemic areas. Only two tick species (A. sculptum and Amblyomma dubitatum) were found in the anthropic areas; however, with a great predominance of A. sculptum (≈90% of all ticks) in the endemic areas, in contrast to a slight predominance of A. dubitatum (≈60%) in the nonendemic areas. Tick species richness was higher in the natural areas, where six species were found, albeit with a predominance of A. sculptum (≈95% of all ticks) and environmental tick burdens much lower than in the anthropic areas. The BSF-endemic areas were characterized by overgrowth populations of A. sculptum that were sustained chiefly by capybaras, and decreased populations of A. dubitatum. In contrast, the BSF-nonendemic areas with landscape similar to the endemic areas differed by having lower tick burdens and a slight predominance of A. dubitatum over A.sculptum, both sustained chiefly by capybaras. While multiple medium- to large-sized mammals have been incriminated as important hosts for A. sculptum in the natural areas, the capybara was the only important host for this tick in the anthropic areas.

Conclusions

The uneven distribution of R. rickettsii infection among A. sculptum populations in highly anthropic areas of São Paulo state could be related to the tick population size and its proportion to sympatric A. dubitatum populations.

Brazilian spotted fever (BSF), caused by the bacterium Rickettsia rickettsii, is the deadliest tick-borne disease of the New World. In southeastern Brazil, where 489 patients succumbed to the disease from 2001 to 2018, R. rickettsii is transmitted to humans mainly by the tick Amblyomma sculptum, which uses the capybara (Hydrochoerus hydrochaeris) as its main host. During 2015–2019, we captured capybaras and ticks in seven highly anthropic areas of São Paulo state (three endemic and four nonendemic for BSF) and in two natural areas of the Pantanal biome. The BSF-endemic areas were characterized by much higher tick burdens on both capybaras and in the environment, with a predominance of Amblyomma sculptum. In the BSF-nonendemic areas, another tick species, Amblyomma dubitatum, outnumbered A. sculptum. In the natural areas, six tick species were found; however, with much lower numbers than in the anthropic areas. The BSF-endemic areas were characterized by overgrowth populations of A. sculptum that were sustained chiefly by capybaras, and decreased populations of A. dubitatum. Results of this study support the idea that any intervention resulting in a drastic reduction of the A. sculptum population shall eliminate the R. rickettsii infection from the tick population, and consequently, prevent new BSF cases.

Comparative Susceptibility of Different Populations of Amblyomma sculptum to Rickettsia rickettsii

The bacterium Rickettsia rickettsii is the etiological agent of Brazilian spotted fever (BSF), which is transmitted in Brazil mainly by the tick Amblyomma sculptum. Herein, larvae and nymphs of six populations of A. sculptum were exposed to R. rickettsii by feeding on needle-inoculated guinea pigs, and thereafter reared on uninfected guinea pigs or rabbits. Two tick populations were exposed to autochthone R. rickettsii strains, whereas four tick populations were exposed to non-autochthone strains. The six geographically different populations of A. sculptum showed different susceptibilities to R. rickettsii, higher among the two tick populations that were exposed to their autochthone R. rickettsii strain. In addition, higher rates of transovarial transmission of R. rickettsii and vector competence success also included the two tick populations that were exposed to autochthone R. rickettsii strains. These results indicate that the susceptibility of A. sculptum to R. rickettsii varies among different tick populations, with a clear bias for higher susceptibility to an autochthone R. rickettsii strain that has already coevolved with a tick population for some time. Our results demonstrated that the R. rickettsii infection induces higher mortality of engorged larvae and nymphs, and tend to reduce the reproductive fitness of engorged females. All together, these results might explain the low R. rickettsii-infection rates of A. sculptum under natural conditions (usually <1%), and indicate that an A. sculptum population should not be able to sustain a R. rickettsii infection for successive tick generations without the creation of new cohorts of infected ticks via horizontal transmission on vertebrate rickettsemic hosts (amplifying hosts). Finally, despite of the ubiquitous distribution of A. sculptum in southeastern and central-western Brazil, most of the populations of this tick species are devoid of R. rickettsii infection. This scenario might be related to two major factors: (i) insufficient numbers of susceptible amplifying hosts; and (ii) lower susceptibilities of many tick populations. While the first factor has been demonstrated by mathematical models in previous studies, the second is highlighted by the results observed in the present study.

The Dynamics of Ticks and Capybaras in a Residential Park Area in Southeastern Brazil: Implications for the Risk of Rickettsia rickettsii Infection

The bacterium Rickettsia rickettsii causes Brazilian spotted fever (BSF), a highly lethal disease that is transmitted by Amblyomma sculptum ticks in areas where capybaras (Hydrochoerus hydrochaeris) are the tick's major hosts. In this study, we evaluated the expansion of a capybara population in a residential park in São Paulo state, and the implications of such expansion to the occurrence of ticks and BSF. The capybara population was quantified during 2004-2013. In 2012, there was a BSF human case in the area, culminating in the complete fencing of the residential park and the official culling of all capybaras. Quantification of ticks in the environment was performed by dry ice traps from 2005 to 2018. Domestic dogs in 2006-2011 and capybaras in 2012 were serologically tested for the presence of anti-R. rickettsii antibodies. Our results show that capybara numbers increased ≈5 times from 2004 (41 capybaras) to 2012 (230 capybaras). Dry ice traps collected A. sculptum and Amblyomma dubitatum. The number of A. dubitatum adult ticks was generally higher than A. sculptum adults during 2005-2006; however, during 2012-2013, A. sculptum outnumbered A. dubitatum by a large difference. During 2016-2018 (after capybara culling), the number of both species fell close to zero. The low numbers of A. sculptum adult ticks during 2005-2006 coincided with relatively low capybara numbers (<80). Thereafter, in 2012, we counted the highest numbers of both A. sculptum ticks and capybaras (230 animals). All 40 canine blood samples were seronegative to R. rickettsii, in contrast to the 48.3% seropositivity (83/172) among capybaras. Our results support that the emergence of BSF in the residential park was a consequence of the increase of the local capybara population, which in turn, provided the increment of the A. sculptum population. Culling the entire capybara population eliminated the risks of new BSF cases.

dos Santos A, Labruna MB, Biondo AW. Ticks and serosurvey of anti-Rickettsia spp. antibodies in wild boars (Sus scrofa), hunting dogs and hunters of Brazil

BACKGROUND

Rickettsia bacteria are responsible for diseases in humans and animals around the world, however few details are available regarding its ecology and circulation among wild animals and human populations at high transmission risk in Brazil. The aim of this study was to investigate the occurrence of ticks and Rickettsia spp. in wild boars, corresponding hunting dogs and hunters.

METHODS

Serum samples and ticks were collected from 80 free-range wild boars, 170 hunting dogs and 34 hunters from southern and central-western Brazil, from the Atlantic Forest and Cerrado biomes, respectively, between 2016 and 2018. Serum samples were tested by indirect immunofluorescent-antibody assay (IFA) to detect IgG antibodies against Rickettsia rickettsii, Rickettsia parkeri, Rickettsia bellii, Rickettsia rhipicephali and Rickettsia amblyommatis. Tick species were identified by morphological taxonomic keys, as previously described. A total of 164 ticks including A. sculptum, A. brasiliense and A. aureolatum were tested in PCR assays for Spotted Fever Group (SFG) Rickettsia spp.

RESULTS

A total of 58/80 (72.5%) wild boars, 24/170 (14.1%) hunting dogs and 5/34 (14.7%) hunters were positive (titers ≥ 64) to at least one Rickettsia species. A total of 669/1,584 (42.2%) ticks from wild boars were identified as Amblyomma sculptum, 910/1,584 (57.4%) as Amblyomma brasiliense, 4/1,584(0.24%) larvae of Amblyomma spp. and 1/1,584 (0.06%) nymph as Amblyolmma dubitatum. All 9 ticks found on hunting dogs were identified as Amblyomma aureolatum and all 22 ticks on hunters as A. sculptum. No tested tick was positive by standard PCR to SFG Rickettsia spp.

CONCLUSIONS

The present study was the concomitant report of wild boar, hunting dog and hunter exposure to SFG rickettsiae agents, performed in two different Brazilian biomes. Wild boar hunting may increase the risk of human exposure and consequently tick-borne disease Wild boars may be carrying and spreading capybara ticks from their original habitats to other ecosystems. Further studies can be required to explore the ability of wild boars to infecting ticks and be part of transmission cycle of Rickettsia spp.

Evaluation of rickettsial infection in free-range capybaras (Hydrochoerus hydrochaeris Linnaeus, 1766) (Rodentia: Caviidae) and ticks (Acari: Ixodidae) in the Western Amazon, Brazil

Capybaras (Hydrochoerus hydrochaeris Linnaeus, 1766) (Rodentia: Caviidae) are important hosts of Amblyomma ticks (Acari: Ixodidae), which in turn can transmit rickettsiae to humans and animals. However, there is a scarcity of studies about the tick fauna and rickettsial infection in the Amazon region. The present study evaluated rickettsial infection in capybaras and ticks in different areas of the municipality of Rio Branco, state of Acre, in the Western Brazilian Amazon, where rickettsiosis has never been reported. Blood sera from 43 capybaras from four localities in Rio Branco were tested by indirect immunofluorescence assay using Rickettsia rickettsii antigens. Ticks were collected from capybaras and from vegetation as well. Ticks were taxonomically identified to the species level and some of them were tested by PCR, targeting a fragment of the rickettsial gltA gene. Additionally, ticks were tested for bacteria from the genus Borrelia and family Anaplasmatacae. All capybaras submitted to the serological examination were considered non-reactive to R. rickettsii. A total of 410 ticks were collected directly from the capybaras. Amblyomma dubitatum Neumann, 1899 was the most abundant species (82.4%), followed by Amblyomma naponense (Packard, 1869) (14.3%), Amblyomma humerale Koch, 1844 (0.7%), Amblyomma pacae Aragão, 1911 (0.4%), Amblyomma rotundatum Koch 1844 (0.2%) and Amblyomma sp. (1.7%). From the environment 262 ticks were collected: Rhipicephalus microplus (Canestrini, 1888) (88.9%), Dermacentor nitens Neumann, 1897 (9.9%), Amblyomma varium Koch, 1844 (0.7%) and A. rotundatum (0.3%). With the exception of A. humerale, A. rotundatum and R. microplus, all other species are reported here for the first time in the state. Some of the ticks sampled (N = 317) were tested by molecular methods for infection by Rickettsia spp. Rickettsia bellii was identified infecting A. dubitatum and A. rotundatum, while Rickettsia amblyommatis only was found infecting A. humerale and Rickettsia sp. strain Tapirapé was found in A. naponense. This is the first detection of R. bellii and Rickettsia sp. strain Tapirapé in Acre. No Borrelia or Anaplasmataceae were found in the tested ticks. These results add relevant knowledge about the Rickettsia spp. and the acarological fauna in the region of the Western Amazon, and are essential for the maintenance of vigilance about possible pathogens that occur in the state and determination of the risks that they pose to humans and animals that inhabit the region.

Hosts mobility and spatial spread of Rickettsia rickettsii

There are a huge number of pathogens with multi-component transmission cycles, involving amplifier hosts, vectors or complex pathogen life cycles. These complex systems present challenges in terms of modeling and policy development. A lethal tick-borne infectious disease, the Brazilian Spotted Fever (BSF), is a relevant example of that. The current increase of human cases of BSF has been associated with the presence and expansion of the capybara Hydrochoerus hydrochaeris, amplifier host for the agent Rickettsia rickettsii and primary host for the tick vector Amblyomma sculptum. We introduce a stochastic dynamical model that captures the spatial distribution of capybaras and ticks to gain a better understanding of the spatial spread of the R. rickettsii and potentially predict future epidemic outcomes. We implemented a reaction-diffusion process in which individuals were divided into classes denoting their state with respect to the disease. The model considered bidirectional movements between base and destination locations limited by the carrying capacity of the environment. We performed systematic stochastic simulations and numerical analysis of the model and investigate the impact of potential interventions to mitigate the spatial spread of the disease. The mobility of capybaras and their attached ticks was significantly influenced by the birth rate of capybaras and therefore, disease propagation velocity was higher in places with higher carrying capacity. Some geographical barriers, generated for example by riparian reforesting, can impede the spatial spread of BSF. The results of this work will allow the formulation of public actions focused on the prevention of BSF human cases.

Complex systems as the Brazilian Spotted Fever (BSF), present challenges in terms of modeling and policy development. BSF human cases have been associated with the presence and expansion of the capybara Hydrochoerus hydrochaeris, amplifier host for the agent Rickettsia rickettsii and primary host for the tick vector Amblyomma sculptum. We developed a reaction-diffusion system for the spread of BSF by considering the spatial structure and migration of amplifier hosts to gain a better understanding of the spatial spread of the R. rickettsii and potentially predict future epidemic outcomes. We performed stochastic simulations and numerical analysis to investigate the impact of potential interventions to mitigate the spatial spread of the disease. Our results indicate that as we vary the amount of capybaras’ food sources, the velocity at which the disease advances is roughly proportional to the carrying capacity, hence proportional to the local risk of zoonotic infection. Some geographical barriers, generated for example by riparian reforesting, can generate positive ecological impacts and can impede the spread of BSF to humans.

Diferenciação morfométrica entre larvas de Amblyomma sculptum Berlese, 1888 e Amblyomma dubitatum Neumann, 1899

RESUMO Os carrapatos estão envolvidos em processos biológicos de uma grande variedade de organismos patogênicos. O gênero Amblyomma é o de maior importância médica, com a espécie Amblyomma sculptum Berlese, 1888 envolvida no ciclo de transmissão da febre maculosa brasileira (FMB). Neste estudo, objetivou-se a validação molecular para uma diferenciação na característica morfométrica e no tamanho de idiossoma de larvas de duas espécies de carrapatos, Amblyomma dubitatum Neumann, 1899 e A. sculptum. Larvas não alimentadas foram coletadas em duas áreas de transmissão para FMB, por meio da técnica de armadilha atrativa de CO2. Foram identificadas em nível de espécie por morfometria comparativa, análise molecular por PCR e sequenciamento genômico, com validação pela análise de concordância pelo teste Kappa. As larvas de A. dubitatum apresentaram um comprimento significativamente maior que as larvas de A. sculptum. Embora nenhuma outra espécie do gênero Amblyomma tenha sido testada neste estudo, essa técnica poderá ser utilizada nos locais onde levantamentos acarológicos prévios, baseados nos estádios de ninfa e adultos, indicaram a presença de apenas A. sculptum e A. dubitatum, geralmente mantidos por capivaras. Digno de nota, essa condição é muito comum ao longo das áreas endêmicas para FMB na região Sudeste do Brasil.

Basic reproduction number for the Brazilian Spotted Fever

Brazilian Spotted Fever (BSF) is an emerging and lethal disease in South America which basic reproduction number (R₀) is unknown. Calculating R₀ for this disease is crucial to design control interventions and prevent human deaths. BSF endemic areas are related to the presence of capybaras Hydrochoerus hydrochaeris, amplifier hosts of Rickettsia rickettsii and primary hosts of the tick Amblyomma sculptum, main vector of the agent in this area. Because of the complexity of its dynamics, we calculated R₀ for the BSF system by constructing a next-generation matrix considering different categories of vectors and hosts. Each matrix element was considered as the expected number of infected individuals of one category produced by a single infected individual of a second category. We used field and experimental data to parameterize the next-generation matrix and obtain the final calculation (R₀ ≈ 1.7). We demonstrated the low impact of the matrix elements corresponding to the transovarial transmission and the transmission from infected larvae in the maintenance of R. rickettsii. Sensitivity and elasticity analyzes were performed to quantify the perturbations of each matrix element in R₀. We noted that the elements equivalent to the number of infected attached nymphs produced by an infected capybara, and the number of infected capybaras produced by an infected attached nymph or adult are the major contributors to changes in R₀. Our results provide insights into the strategic design of preventive interventions in BSF endemic areas.

Midichloria mitochondrii, endosymbiont of Ixodes ricinus: evidence for the transmission to the vertebrate host during the tick blood meal

Ticks are important vectors of a variety of pathogens affecting humans and other animals, but they also harbor numerous microorganisms whose role is still limitedly investigated. Ixodes ricinus harbors the endosymbiont Midichloria mitochondrii, which is localized in ovaries and in salivary glands. The bacterium is vertically transmitted and is present in 100% of wild adult females, while prevalence values drop after some generations under laboratory conditions. Molecular and serological evidences showed that M. mitochondrii molecules are transmitted to the vertebrate hosts by I. ricinus during the blood meal. Our work was focused on monitoring M. mitochondrii antigens and DNA in a vertebrate model after infestation with I. ricinus for a time-span of four months. Two groups of rabbits were infested with I. ricinus females, respectively from the wild (naturally infected with the symbiont) and laboratory strain (lab; considered devoid of M. mitochondrii after quantitative PCR investigations) and screened using molecular and serological assays at nine time points. M. mitochondrii presence was detected in rabbits infested with wild I. ricinus ticks, but surprisingly also in those infested with lab ticks, albeit at later time points. This result prompted a more sensitive molecular screening of lab ticks, which were found to harbor very low symbiont loads. Our results indicate that transmission of the bacterium occurs even at low bacterial loads, and that antibody response against M. mitochondrii antigens begins within one week post-infestation with wild I. ricinus. Circulating DNA was detected in the blood of rabbits belonging to both groups up to the end of the experiment, suggesting a replication of the symbiont inside the vertebrate host.

Capybara meat: An extraordinary resource for food security in South America

The available information on capybara (Hydrochoerus hydrochaeris) meat, an important resource for the subsistence of many traditional communities in several South American countries, is reviewed. Some features of the species, such as an herbivorous diet, high prolificacy, rapid growth rate, tameness, and social behaviour, which allow its commercial use through harvesting in Venezuela and farming in Brazil, where commercial hunting is not allowed, is discussed. Key characteristics of capybara meat, is low saturated fat and cholesterol content. Discussions about management and handling practices regarding animal welfare and capybara meat quality are also highlighted. After commenting on ethical, political, and economic implications of wildlife use it is concluded that capybara meat has an extraordinary potential to satisfy the growing demand for healthy and high-quality protein of animal origin for the subsistence of many people in the Neotropics.

Neglected aspects of tick-borne rickettsioses

Rickettsioses are among the oldest known infectious diseases. In spite of this, and of the extensive research carried out, many aspects of the biology and epidemiology of tick-borne rickettsiae are far from being completely understood. Their association with arthropod vectors, the importance of vertebrates as reservoirs, the rarity of clinical signs in animals, or the interactions of pathogenic species with rickettsial endosymbionts and with the host intracellular environment, are only some examples. Moreover, new rickettsiae are continuously being discovered. In this review, we focus on the ‘neglected’ aspects of tick-borne rickettsioses and on the gaps in knowledge, which could help to explain why these infections are still emerging and re-emerging threats worldwide.

CAPIVARAS (Hydrochoerus hydrochaeris) E A PRESENÇA DO CARRAPATO (Amblyomma sculptum) NO CAMPUS DA UFSCAR-ARARAS, SÃO PAULO

Resumo Capivaras são territoriais e vivem em grupos sociais, ocorrendo comumente em áreas antropizadas. Em algumas regiões do Brasil, estes animais apresentam infestação por carrapatos do gênero Amblyomma, que por sua vez são considerados como principal vetor biológico e reservatório natural da bactéria Rickettsia rickettsii, agente causador da Febre Maculosa Brasileira. Na UFSCar campus Araras, a interação entre capivaras, carrapatos e comunidade acadêmica é frequente, ocorrendo principalmente durante a estação seca. Este estudo teve como objetivo realizar um censo populacional das capivaras que ocupam o campus, identificando sua área de uso e se estes roedores se encontravam infestados por carrapatos. Realizou-se observação direta das capivaras, captura-marcação e recaptura com uso de um brete, e também coleta dos carrapatos nas capivaras e no ambiente. Registrou-se um total de 56 capivaras, com densidade de 1,50 ind./ha. Foram capturados 24 animais, sendo 25% machos e 75% fêmeas, dos quais 25% eram adultos, 45,8% jovens e 29,2% filhotes. A espécie de carrapato amplamente encontrada infestando tanto os animais como o ambiente foi A. sculptum. Conclui-se que o grupo de capivaras apresentou um número elevado de indivíduos por causa da abundância de recursos e ausência de predadores, e também com grande infestação por carrapatos.

Analysis of the Salivary Gland Transcriptome of Unfed and Partially Fed Amblyomma sculptum Ticks and Descriptive Proteome of the Saliva

Ticks are obligate blood feeding ectoparasites that transmit a wide variety of pathogenic microorganisms to their vertebrate hosts. Amblyomma sculptum is vector of Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever (RMSF), the most lethal rickettsiosis that affects humans. It is known that the transmission of pathogens by ticks is mainly associated with the physiology of the feeding process. Pathogens that are acquired with the blood meal must first colonize the tick gut and later the salivary glands (SG) in order to be transmitted during a subsequent blood feeding via saliva. Tick saliva contains a complex mixture of bioactive molecules with anticlotting, antiplatelet aggregation, vasodilatory, anti-inflammatory, and immunomodulatory properties to counteract both the hemostasis and defense mechanisms of the host. Besides facilitating tick feeding, the properties of saliva may also benefits survival and establishment of pathogens in the host. In the current study, we compared the sialotranscriptome of unfed A. sculptum ticks and those fed for 72 h on rabbits using next generation RNA sequencing (RNA-seq). The total of reads obtained were assembled in 9,560 coding sequences (CDSs) distributed in different functional classes. CDSs encoding secreted proteins, including lipocalins, mucins, protease inhibitors, glycine-rich proteins, metalloproteases, 8.9 kDa superfamily members, and immunity-related proteins were mostly upregulated by blood feeding. Selected CDSs were analyzed by real-time quantitative polymerase chain reaction preceded by reverse transcription (RT-qPCR), corroborating the transcriptional profile obtained by RNA-seq. Finally, high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis revealed 124 proteins in saliva of ticks fed for 96–120 h. The corresponding CDSs of 59 of these proteins were upregulated in SG of fed ticks. To the best of our knowledge, this is the first report on the proteome of A. sculptum saliva. The functional characterization of the identified proteins might reveal potential targets to develop vaccines for tick control and/or blocking of R. rickettsii transmission as well as pharmacological bioproducts with antihemostatic, anti-inflammatory and antibacterial activities.

Transmission dynamics and control of Rickettsia rickettsii in populations of Hydrochoerus hydrochaeris and Amblyomma sculptum

BACKGROUND

Brazilian Spotted Fever (BSF), caused by the bacterium Rickettsia rickettsii, is the tick-borne disease that generates the largest number of human deaths in the world. In Brazil, the current increase of BSF human cases has been associated with the presence and expansion of capybaras Hydrochoerus hydrochaeris, which act as primary hosts for the tick Amblyomma sculptum, vector of the R. rickettsii in this area.

METHODS

We proposed a semi-discrete-time stochastic model to evaluate the role of capybaras in the transmission dynamics of R. rickettsii. Through a sensitivity analysis, we identified the parameters with significant influence on the R. rickettsii establishment. Afterward, we implemented the Gillespie's algorithm to simulate the impact of potential public health interventions to prevent BSF human cases.

RESULTS

The introduction of a single infected capybara with at least one infected attached tick is enough to trigger the disease in a non-endemic area. We found that to avoid the formation of new BSF-endemic areas, it is crucial to impede the emigration of capybaras from endemic areas by reducing their birth rate by more than 58%. Model results were corroborated by ex-situ data generated from field studies, and this supports our proposal to prevent BSF human cases by implementing control strategies focused on capybaras.

CONCLUSION

The proposed stochastic model illustrates how strategies for the control and prevention of vector-borne infectious diseases can be focused on amplifier hosts management practices. This work provides a basis for future prevention strategies for other neglected vector-borne diseases.

Isolation of Rickettsia rickettsii from the tick Amblyomma sculptum from a Brazilian spotted fever-endemic area in the Pampulha Lake region, southeastern Brazil

Brazilian spotted fever (BSF) is a tick-borne disease caused by the bacterium Rickettsia rickettsii, the deadliest spotted fever of the world, transmitted in southeastern Brazil mainly by the tick Amblyomma sculptum, a member of the Amblyomma cajennense species complex. In the present study, over 5000 adults of A. sculptum ticks were collected by dry ice traps in the Municipal Ecological Park, alongside the Pampulha Lake region, a BSF-endemic area of Belo Horizonte city, state of Minas Gerais, southeastern Brazil. Ticks were taken alive to the laboratory, where a sample of 2100 specimens was processed for isolation of R. rickettsii. For this purpose, ticks were macerated and intraperitoneally inoculated into guinea pigs. Only one out of 21 inoculated guinea pigs presented high fever within 21days post inoculation with tick homogenates. This febrile animal was euthanized and its internal organs were macerated and inoculated into additional guinea pigs (guinea pig passage). A spleen sample from a febrile guinea pig was used to inoculate Vero cells, resulting in a successful isolation and in vitro establishment of rickettsiae. Rickettsia-infected Vero cells were used for molecular characterization of the rickettsial isolate through PCR and DNA sequencing of fragments of three rickettsial genes (gltA, ompA, and ompB), which were all 100% identical to corresponding sequences of R. rickettsii from GenBank. The present R. rickettsii isolate was designated as strain Pampulha. A minimal infection rate of 0.05% R. rickettsii-infected ticks was estimated for A. sculptum population of the Pampulha Lake region. Our results, coupled with epidemiological evidences, suggest that R. rickettsii strain Pampulha, isolated from A. sculptum ticks in the present study, is the strain responsible for human clinical cases of BSF in the Pampulha Lake region of Belo Horizonte city.

Antibodies for Rickettsia spp. in patients with negative serology for dengue virus, leptospirosis, and meningococcal disease in municipalities of São Paulo State, Brazil

INTRODUCTION

Brazilian spotted fever is an infectious disease with a high mortality rate if not treated early. Differential diagnosis is difficult, as the first clinical signs are non-specific and can be confused with other diseases. The aim of the study was to investigate evidence of infection with Rickettsia rickettsii and Rickettsia parkeri in negative sera samples, collected in 2014, from patients with suspected leptospirosis, dengue fever, and meningococcal disease in Atibaia and Bragança Paulista municipalities of the State of São Paulo.

METHODS

The samples stored at the Institute Adolfo Lutz in Campinas were tested using an indirect immunofluorescence assay (IFA) with IgG and IgM against R. rickettsii and R. parkeri. Real-time polymerase chain reaction (PCR) testing was performed for the sera samples of patients who died (n = 3), those with initial suspicion of meningococcal disease (n = 6), and those with positive IFA results.

RESULTS

Of 258 samples from Bragança Paulista, 4 (1.6%) were positive, with IgG titers of 1:64 and 1:128 against R. rickettsii and R. parkeri, respectively. Of 155 samples from Atibaia, 2 (1.3%) were positive, with IgG titers of 1:64 and 1:128 against R. rickettsii and R. parkeri, respectively. No sample showed positive PCR results.

CONCLUSIONS

This serological investigation suggests there is evidence of exposure to Rickettsia spp. in residents of areas that have environmental conditions favorable to the spread of bacteria, in which Brazilian spotted fever incidence was not previously confirmed.

Vectorial competence of Amblyomma tonelliae to transmit Rickettsia rickettsii

The aim of this work was to test the vectorial competence of Amblyomma tonelliae (Ixodida: Ixodidae) to transmit Rickettsia rickettsii (Rickettsiales: Rickettsiaceae), the agent of Rocky Mountain spotted fever (RMSF). All parasitic stages of A. tonelliae were exposed to R. rickettsii by allowing each stage to feed on hosts inoculated with this pathogen. Thereafter, ticks were fed on uninfected hosts. All stages of A. tonelliae were able to acquire the R. rickettsii infection and maintain it by transstadial and transovarial transmission. When infected ticks fed on uninfected hosts, the hosts developed rickettsiosis disease. This study demonstrates the vectorial competence of A. tonelliae to transmit R. rickettsii. These results have epidemiological relevance because A. tonelliae is one of the tick species most likely to infest humans in Argentina, including in areas in which RMSF has been reported.