Metrics details. Brazilian spotted fever BSF , caused by the bacterium Rickettsia rickettsii, is the deadliest spotted fever of the world. In most of the BSF-endemic areas, capybaras Hydrochoerus hydrochaeris are the principal host for the tick Amblyomma cajennense, which is the main vector of BSF. In , a BSF case was confirmed in a child that was bitten by ticks in a residential park area inhabited by A.
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Metrics details. Brazilian spotted fever BSF , caused by the bacterium Rickettsia rickettsii, is the deadliest spotted fever of the world. In most of the BSF-endemic areas, capybaras Hydrochoerus hydrochaeris are the principal host for the tick Amblyomma cajennense, which is the main vector of BSF. In , a BSF case was confirmed in a child that was bitten by ticks in a residential park area inhabited by A. Host questing A. A tick-inoculated guinea pig that presented high fever was euthanized and its internal organs were macerated and inoculated into additional guinea pigs guinea pig passage.
Tissue samples from guinea pig passages were also used to inoculate Vero cells through the shell vial technique. Infected 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.
Blood serum samples were collected from capybaras that inhabited the residential park. Sera were tested through the immunofluorescence assay using R. A tick-inoculated guinea pig presented high fever accompanied by scrotal reactions edema and marked redness. These signs were reproduced by consecutive guinea pig passages. Rickettsia was successfully isolated in Vero cells that were inoculated with brain homogenate derived from a 3 rd passage-febrile guinea pig.
A total of 83 A viable isolate of R. Nearly half of the capybara population of the residential park was seroreactive to R. Brazilian spotted fever BSF is the deadliest spotted fever of the world. It has been reported in southeastern Brazil, where laboratory-confirmed cases were reported from to , resulting in deaths The disease is caused by the bacterium Rickettsia rickettsii, which also causes severe cases of spotted fever in other American countries, including the United States, where the disease is called Rocky Mountain spotted fever RMSF.
The reasons for such a contrast are still speculative; however, two studies have showed genetic differences between R. In Brazil, R. In these areas, R. However, because R. Competent amplifier hosts are still unknown in the A. Similarly to that previously reported for A. However, R. For this reason, the participation of vertebrate amplifier hosts to create new lineages of infected ticks, in order to avoid the disappearance of R. In this case, capybaras Hydrochoerus hydrochaeris have played a crucial role in BSF-endemic areas of southeastern Brazil [ 8 , 12 , 13 ].
Besides being the most important host for all parasitic stages of A. During the first half of the 20 th century, A. Since then, no additional viable isolates of R. While a few recent studies detected R. These findings corroborate the above mentioned experimental studies, which showed that A. Even under such circumstances, A. In the present study, we investigated the circulation of R. During the study, we obtained a viable isolate of R.
In September , a severe case of BSF occurred in a child few days after being infested by ticks while playing near one of the lakes of the residential park, inhabited by free-ranging capybaras. After two weeks under hospitalization and therapy with chloramphenicol, the child had the infection resolved.
In October , we visited the residential park for collection of free-living ticks by using 20 CO 2 traps armed at capybara common places including the site where the child got tick-infested as previously described [ 26 ].
Thousands of Amblyomma unfed nymphs, and hundreds of Amblyomma unfed adult ticks were captured by the CO 2 traps. The A. The 42 A. Since we had 8 tick pools, we used 8 guinea pigs, one per tick pool. Guinea pigs had their rectal temperature measured daily until the 21st day post inoculation DPI , when they were bled through cardiac puncture, and their sera were individually tested for the presence of anti- R.
If the result was positive, the monolayer of the shell vial was harvested and inoculated into a cm 2 flask containing a monolayer of confluent uninfected Vero cells. M59 and targeting a portion of the rickettsial ompB gene [ 30 ]. Because the A. For this purpose, from December to May , a total of capybaras were collected by corrals according to Moreira et al. Capybara sera were individually tested through the IFA using R.
Briefly, capybara sera were diluted in 2-fold increments with phosphate-buffered saline PBS , starting from the dilution. For each sample, the endpoint IgG titer reacting with R. In each slide, a serum previously shown to be non-reactive negative control and a known reactive serum positive control , both from the study of Souza et al. The proportions of seroreactive capybaras were compared between three age categories infant, juvenile, or adult and gender male or female by the Chi-square test.
Among the 8 guinea pigs inoculated with adult tick homogenate, 2 animals one inoculated with A. Among the remaining 6 guinea pigs each of 5 inoculated with A.
These animals were euthanized at the 3 rd febrile day and their internal organs were used to inoculate 2 additional guinea pigs.
In all cases, fever was accompanied by scrotal reactions edema and marked redness ; a single guinea pig from the 3rd passage was not euthanized; in this case, the animal presented high fever from the 5 th to the 9 th DPI. When this animal was tested by serology at the 21th DPI, it presented a 8, endpoint titer to R. The remaining guinea pigs that were primarily inoculated with tick homogenate each of 4 inoculated with A.
Rickettsiae were successfully isolated in Vero cells that were inoculated with brain homogenate derived from a 3 rd guinea pig passage of the A. The rickettsial isolate was designated as strain ITU. The GenBank nucleotide sequence accession numbers of the partial sequences of R. A total of capybaras were sampled in the residential park. From these, 83 Seroreactive capybaras presented endpoint titers to R.
To achieve such results, we initially performed intraperitoneal inoculation of tick homogenate into guinea pigs, a method that was widely used during the first half of the 20 th century, when all previous isolates of R.
With such procedure, we were able to sample hundreds of ticks with relatively few efforts, if compared to more contemporary methods that usually test ticks individually or in pools of few specimens by inoculating cell culture, such as the shell vial technique [ 28 , 35 , 36 ]. Indeed, the increasing use of the shell vial technique has allowed isolation of various Rickettsia species that could not be isolated by inoculation of guinea pigs with field-collected samples, just because most of the Rickettsia species are not pathogenic for this animal species [ 37 ].
On the other hand, because guinea pig inoculation remains an efficient and simple method for isolation of R. In fact, at least two recent studies have used guinea pig inoculation of patient samples for confirmatory diagnostic of RMSF fatal cases in Colombia and Costa Rica [ 38 , 39 ]. Only one guinea pig, inoculated with A. This result indicates that at least one R. Because other 4 guinea pigs, each inoculated with A.
This low rate is quite expected since several recent studies have failed to detect R. Since human infestation by A. This procedure was adopted because previous studies reported that injection of triturated, unfed, R.
Nearly half of this capybara population was seroreactive to R. In a recent study [ 14 ], capybaras experimentally infected with R. On the other hand, capybaras with lower antibody titers could be in a phase of ascending recent infection or descending earlier infection antibody titers to R. Finally, the overall lower titers observed in infant capybaras of the present study could be related to passive immunity, whereas overall higher endpoint titers in juvenile and adult capybaras could be related to a past active immunity elicited by transmission of R.
The fact that nearly half of the capybara population of the residential park was seronegative to R. Therefore, the procedure of the residential park to cull its entire capybara population was reasonable, in order to prevent new human cases of BSF in the area, where no other host species i.
Rev Panam Salud Publica. Google Scholar. Ann N Y Acad Sci. J Clin Microbiol. Curr Infect Dis Rep. Rev Bras Parasitol Vet. Emerg Infect Dis. Med Vet Entomol. Labruna MB: Brazilian spotted fever: the role of capybaras. Vet Parasitol. Bras Med. Vallejo-Freire A: Spotted fever in Mexico. Mem Inst Butantan.
Mem Inst Oswaldo Cruz. Rev Soc Bras Med Trop. Exp Appl Acarol. Marrero M, Raoult D: Centrifugation-shell vial technique for rapid detection of Mediterranean spotted fever rickettsia in blood culture.
Hydrochoerus hydrochaeris - Capybara
All rights reserved. You thought the beaver was a rodent of unusual size? The capybara is twice that big —the biggest rodent on Earth. These impressive semi-aquatic mammals are found throughout much of northern and central South America, though a small invasive population has been seen in Florida. Like beavers, capybaras are strong swimmers.
Capybaras (Hydrochoerus spp.) Fact Sheet: Taxonomy & History
The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.
Hydrochoerus hydrochaeris is a strictly South American rodent species. Its range extends throughout most of Brazil, Uruguay, Venezuela, and Columbia, south into the Argentinian pampas, and west to the Andes. Capybaras are found only in areas where water is easily accessible: flooded grasslands are a favored habitat, as are marsh edges and lowland forests where grazing is good and there is water year-round. However, they occupy a range of habitats, including dry forest, scrub, and grasslands throughout South America. Capybaras are the largest of rodents, weighing from 35 to 66 kg and standing up to 0. Females of this species are slightly larger than males.