Rickettsiae-infected Ticks in an Endemic Area of Spotted Fever in the State of Minas Gerais, Brazil

A study on tick-borne rickettsiosis was developed in the county of Santa Cruz do Escalvado, State of Minas Gerais, Brazil, where a clinical case of the disease, confirmed by necropsy, had been reported. Of the 1,254 ticks collected, 1,061 belonged to the Amblyomma genus, 57 to the Rhipicephalus sanguineus species, 81 to Boophilus microplus, and 46 to Anocentor nitens. The hemolymph test associated with Giménez staining showed that 18 of the 221 A. cajennense specimens, 1 of the 16 R. sanguineus, 1 of the 22 B. microplus, 3 of the A. nitens, and 1 of the A. ovale contained rickettsia-like microorganisms. Only 3 A. cajennense ticks were positive under direct immunofluorescence. A. cajennense was the only species found on humans

Experimental Infection of Amblyomma aureolatum Ticks with Rickettsia rickettsii

We experimentally infected Amblyomma aureolatum ticks with the bacterium Rickettsia rickettsii, the etiologic agent of Rocky Mountain spotted fever (RMSF). These ticks are a vector for RMSF in Brazil. R. rickettsii was efficiently conserved by both transstadial maintenance and vertical (transovarial) transmission to 100% of the ticks through 4 laboratory generations. However, lower reproductive performance and survival of infected females was attributed to R. rickettsii infection. Therefore, because of the high susceptibility of A. aureola turn ticks to R. rickettsii infection, the deleterious effect that the bacterium causes in these ticks may contribute to the low infection rates (< 1%) usually reported among field populations of A. aureolatum ticks in RMSF-endemic areas of Brazil. Because the number of infected ticks would gradually decrease after each generation, it seems unlikely that A. aureolatum ticks could sustain R. rickettsii infection over multiple successive generations solely by vertical transmission.

Experimental Infection of Opossums Didelphis aurita by Rickettsia rickettsii and Evaluation of the Transmission of the Infection to Ticks Amblyomma cajennense

The present study evaluated the infection of opossums (Didelphis aurita) by Rickettsia rickettsii and their role as amplifier hosts for horizontal transmission of R. rickettsii to Amblyomma cajennense ticks. Three groups of opossums were evaluated: on day 0, group 1 (G1) was inoculated intraperitoneally with R. rickettsii; group 2 (G2) was infested by R. rickettsii-infected ticks; and group 3 (G3) was the uninfected control group. Opossum rectal temperature was measured daily. Blood samples were collected every 2 to 4 days during 30 days, and used to (1) inoculate guinea pigs intraperitoneally; (2) extract DNA followed by real-time polymerase chain reaction (PCR) targeting the rickettsial gene gltA; (3) study hematology; (4) detect R. rickettsii-reactive antibodies by indirect direct immunofluorescence assay (IFA). Blood was also collected every 10 days from days 30 to 180, to be tested by serology. Opossums were infested by uninfected A. cajennense larvae and nymphs from days 3 to 15. Engorged ticks were collected and allowed to molt in an incubator. Thereafter, the subsequent flat ticks were allowed to feed on uninfected rabbits, which were tested for seroconversion by IFA. Samples of flat ticks were also tested by real-time PCR. All G1 and G2 opossums became infected by R. rickettsii, as demonstrated by real-time PCR or/and guinea pig inoculation, but they showed no clinical abnormality. Rickettsemia was first detected at days 2 to 8, lasting intermittently till days 1 to 30. Approximately 18% and 5% of the flat ticks previously fed on G1 and G2 opossums, respectively, became infected by R. rickettsii, but only the rabbits infested with G1-derived ticks seroconverted. The study demonstrated that R. rickettsii was capable of infecting opossums without causing illness and developing rickettsemia capable of causing infection in guinea pigs and ticks, although the infection rate in ticks was low.

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

The present study evaluated the infection of capybaras (Hydrochoerus hydrochaeris) by Rickettsia rickettsii and their role as amplifier hosts for horizontal transmission of R. rickettsii to Amblyomma cajennense ticks. Two groups of two capybaras each were evaluated: on day 0, group 1 (G1) was infested by R. rickettsii-infected ticks, and group 2 (G2) was inoculated intraperitoneally with R. rickettsii. Two additional groups were control groups, not exposed to R. rickettsii, being CG1 group the control of G1, and CG2 group the control of G2. Capybara rectal temperature was measured daily. Blood samples were collected every 3 days during 30 days, and used to (i) inoculate guinea pigs intraperitoneally; (ii) DNA extraction followed by real-time PCR targeting the rickettsial gene gltA; (iii) hematology; (iv) detection of R. rickettsii-reactive antibodies by indirect immunofluorescence assay (IFA). Blood was also collected from G I capybaras every approximate to 10-30 days till the 146th day, to be tested by serology. Capybaras were infested by uninfected A. cajennense nymphs from the 3rd to the 18th day. Engorged nymphs were collected, allowed to molt to adults in an incubator. Thereafter, the subsequent flat ticks were tested by PCR. All G1 and G2 capybaras became infected by R. rickettsii, as demonstrated by guinea pig inoculation and seroconversion, but they showed no fever. Rickettsemia was continually detected from the 6th (G2 capybaras) or 9th (G1 capybaras) to the 18th day post inoculation or infestation with R. rickettsii-infected ticks. A total of 20-25% and 30-35% of the flat ticks previously fed on G1 and G2 capybaras, respectively, became infected by R. rickettsii. The study demonstrated that R. rickettsii was capable to infect capybaras without causing clinical illness, inducing rickettsemia capable to cause infection in guinea pigs and ticks. Our results indicate that capybaras act as amplifier host of R. rickettsii for A. cajennense ticks in Brazil. (c) 2008 Elsevier B.V. All rights reserved.

Ticks (Acari: Ixodidae) Infesting Birds in an Atlantic Rain Forest Region of Brazil

Brazil has the third richest bird diversity of the world; however, there are few data concerning ticks (Acari: Ixodidae) parazitizing birds. The aim of the study was to report tick infestations on wild birds from an Atlantic rain forest region of Brazil. During 2 yr, ticks were collected from birds and from the environment in 12 forest sites. A total of 1,725 birds were captured representing 80 species from 24 families. In total, 223 (13%) birds were found infested by immature stages of Amblyomma ticks: 1,800 larvae and 539 nymphs. The prevalence of ticks was higher among-birds from the families Thamnophilidae, Conopophagidae, and Momotidae. The most common tick parasitizing birds was Amblyomma nodosum Koch. Other tick species, Amblyomma coelebs Neumann, Amblyomma cajennense (F.), Amblyomma ovale Koch, Amblyomma longirostre (Koch), Amblyomma calcaratum Neumann, and Amblyomma naponense (Packard), were found sporadically. Among free-living ticks collected in the environment, A. cajennense was the most common, followed by A. coelebs, A. naponense, Amblyomma brasilense Aragao, and Hemaphysalis juxtakochi Cooley.

Experimental infection of dogs with a Brazilian strain of Rickettsia rickettsii: clinical and laboratory findings

The bacterium Rickettsia rickettsii is the etiological agent of an acute, severe disease called Rocky Mountain spotted fever in the United States or Brazilian spotted fever (BSF) in Brazil. In addition to these two countries, the disease has also been reported to affect humans in Mexico, Costa Rica, Panama, Colombia and Argentina. Like humans, dogs are also susceptible to R. rickettsii infection. However, despite the wide distribution of R. rickettsii in the Western Hemisphere, reports of R. rickettsii-induced illness in dogs has been restricted to the United States. The present study evaluated the pathogenicity for dogs of a South American strain of R. rickettsii. Three groups of dogs were evaluated: group 1 (G1) was inoculated ip with R. rickettsii; group 2 (G2) was infested by R. rickettsii-infected ticks; and the control group (G3) was infested by uninfected ticks. During the study, no clinical abnormalities, Rickettsia DNA or R. rickettsii-reactive antibodies were detected in G3. In contrast, all G1 and G2 dogs developed signs of rickettsial infection, i.e., fever, lethargy, anorexia, ocular lesions, thrombocytopenia, anemia and detectable levels of Rickettsia DNA and R. rickettsii-reactive antibodies in their blood. Rickettsemia started 3-8 days after inoculation or tick infestation and lasted for 3-13 days. Our results indicate that a Brazilian strain of R. rickettsii is pathogenic for dogs, suggesting that canine clinical illness due to R. rickettsii has been unreported in Brazil and possibly in the other South American countries where BSF has been reported among humans.

New Epidemiological Data on Brazilian Spotted Fever in an Endemic Area of the State of Sao Paulo, Brazil

The present work evaluated rickettsial infection in dogs and their ticks in an area endemic for Brazilian spotted fever (BSF) in the metropolitan area of Sao Paulo, Brazil, where the tick Amblyomma aureolatum was presumed to be the vector of the disease. Ticks were collected on dogs from 185 houses, encompassing single infestations by Rhipicephalus sanguineus, Amblyomma aureolatum, Amblyomma longirostre, or Amblyomma sp. in dogs from 60 (32.4%), 77 (41.6%), 2 (1.1%), and 25 (13.5%) houses, respectively; 19 (10.3%) houses had dogs with mixed infestations by R. sanguineus and A. aureolatum; 1 (0.5%) house had dogs with infestations by A. aureolatum and A. longirostre; and 1 (0.5%) house had dogs with infestations by R. sanguineus and Amblyomma sp. Overall, A. aureolatum was present in dogs from 97 (52.4%) houses, and R. sanguineus in dogs from 80 (43.2%) houses. A total of 287 ticks (130 A. aureolatum and 157 R. sanguineus) infesting dogs from 98 houses were selected for testing by polymerase chain reaction (PCR) targeting rickettsial genes. Overall, 3.1% of the A. aureolatum ticks were infected by Rickettsia bellii, and 1.3% of the R. sanguineus were infected by Ricketttsii rickettsii. For serology, we selected 23 dogs living in and in the vicinity of the house where the R. rickettsii-infected ticks were collected. The indirect fluorescent antibody (IFA) test detected antibodies reactive with R. rickettsii in sera from 16 (69.6%) dogs, with titers ranging from 256 to 32,768. It is established that Amblyomma aureolatum is a vector of R. rickettsii in the Sao Paulo metropolitan area, but our results highlight for the first time in Brazil, a possible role of R. sanguineus in the epidemiology of R. rickettsii, corroborating previous findings in Mexico and the United States, where R. sanguineus has been implicated in the transmission of R. rickettsii to humans.

Ecology of Rickettsia in South America

Until the year 2000, only three Rickettsia species were known in South America: (i) Rickettsia rickettsii, transmitted by the ticks Amblyomma cajennense, and Amblyomma aureolatum, reported in Colombia, Argentina, and Brazil, where it is the etiological agent of Rocky Mountain spotted fever; (ii) Rickettsia prowazekii, transmitted by body lice and causing epidemic typhus in highland areas, mainly in Peru; (iii) Rickettsia typhi, transmitted by fleas and causing endemic typhus in many countries. During this new century, at least seven other rickettsiae were reported in South America: Rickettsia felis infecting fleas and the tick-associated agents Rickettsia parkeri, Rickettsia massiliae, Candidatus ""Rickettsia amblyommii,"" Rickettsia bellii, Rickettsia rhipicephali, and Candidatus ""Rickettsia andeanae. "" Among these other rickettsiae, only R. felis, R. parkeri and R. massiliae are currently recognized as human pathogens. R. rickettsii is a rare agent in nature, infecting : <= 1% individuals in a few tick populations. Contrastingly, R. parkeri, Candidatus ""R. amblyommii, "" R. rhipicephali, and R. bellii are usually found infecting 10 to 100% individuals in different tick populations. Despite rickettsiae being transmitted transovarially through tick generations, low infection rates for R. rickettsii are possibly related to pathogenic effect of R. rickettsii for ticks, as shown for A. aureolatum under laboratory conditions. This scenario implies that R. rickettsii needs amplifier vertebrate hosts for its perpetuation in nature, in order to create new lines of infected ticks (horizontal transmission). In Brazil, capybaras and opossums are the most probable amplifier hosts for R. rickettsii, among A. cajennense ticks, and small rodents for A. aureolatum.

Acquisition and transmission of Hepatozoon canis (Apicomplexa: Hepatozoidae) by the tick Amblyomma ovale (Acari: Ixodidae)

The present study aimed to evaluate under controlled conditions the acquisition of Hepatozoon canis by Amblyomma ovale after feeding on infected dogs, and the subsequent induction of infection in uninfected dogs that ingested the experimentally infected ticks. Two H. canis naturally infected dogs were infested with A. ovate adult ticks derived from an uninfected laboratory tick colony. After feeding, two A. ovale females presented H. canis oocysts in the hemolymph at the first and fourth days after removal of ticks from dogs. The oocysts had an average size of 244.34 mu m x 255.46 mu m. Three uninfected dogs were fed with ticks previously fed on the infected dogs. Only one dog became infected 32 days after oral inoculation, presenting circulating gametocytes, parasitemia less than 1%, and positive PCR confirmed to be H. canis by DNA sequencing. The results obtained indicated A ovale ticks as potential vector of H. canis in rural areas of Brazil. (C) 2009 Elsevier B.V. All rights reserved.

Poderá o carrapato transmitir a lepra?: mais quatro amostras de culturas de bacilos acido-alcool resistentes obtidas de carrapatos (2 de "Amblyomma cajennense"e 2 de "Boophilus microplus") infectados em leprosos do Paraná: 3ª nota

The AA. carried out experiments in the leprosarium São Roque, State of Paraná, South Brazil, to verify if the cattle tick Boophilus microplus could be experimentally infected in lepers, which was true. The AA. Tried also to be ascertained if Boophilus microplus and Amblyomma cajennense could change of hosts during their feedings which was true, both ticks continue feeding, the last species for many days, after being transferred from one to another leper. The junior A. describes in full their experiments and also a dermatites caused by tick bites. The senior A. brought to Rio de Janeiro most of the infected ticks for examination, which revealed a very high positivity. He smeared the sediments of lots of both species of ticks in Loewenstein medium and after a variable periode of incubation at 37° C. he obtained four new samples of cultures of acid-fast organisms, two from Amblyomma cajennense and two from Boophilus microplus. These cultures are being studied and will be inoculated into laboratory animals. The senior A. inoculated new batches of white rats with sediments of many ticks infected in lepers. Various hypotheses of both previous notes upon the subject now are verified facts. The A. is accumulating facts to draw the conclusions in the future. He also suggested the leprosy workers in the interior of the country to cooperate with him in such important studies, specially in the habitat of lepers in the rural zones of various States.

Infecção experimental de carrapatos (Amblyomma cajennense) em ratos com lepra Stefansky

The A. succeeded, after various experiments, to infect ticks (Amblyoma cajennense) with STEFANSKY bacillus, upon feeding them in rats suffering from murine leprosy, in advanced stages. The A. thinks that will be ease to transfer the sickness from rat to rat by means of inoculation of triturate of infected ticks, as did MARCHOUX with Laelaps echdninus.

Experimental infection of dogs with a Brazilian strain of Rickettsia rickettsii: clinical and laboratory findings

The bacterium Rickettsia rickettsii is the etiological agent of an acute, severe disease called Rocky Mountain spotted fever in the United States or Brazilian spotted fever (BSF) in Brazil. In addition to these two countries, the disease has also been reported to affect humans in Mexico, Costa Rica, Panama, Colombia and Argentina. Like humans, dogs are also susceptible to R. rickettsii infection. However, despite the wide distribution of R. rickettsii in the Western Hemisphere, reports of R. rickettsii-induced illness in dogs has been restricted to the United States. The present study evaluated the pathogenicity for dogs of a South American strain of R. rickettsii. Three groups of dogs were evaluated: group 1 (G1) was inoculated ip with R. rickettsii; group 2 (G2) was infested by R. rickettsii-infected ticks; and the control group (G3) was infested by uninfected ticks. During the study, no clinical abnormalities, Rickettsia DNA or R. rickettsii-reactive antibodies were detected in G3. In contrast, all G1 and G2 dogs developed signs of rickettsial infection, i.e., fever, lethargy, anorexia, ocular lesions, thrombocytopenia, anemia and detectable levels of Rickettsia DNA and R. rickettsii-reactive antibodies in their blood. Rickettsemia started 3-8 days after inoculation or tick infestation and lasted for 3-13 days. Our results indicate that a Brazilian strain of R. rickettsii is pathogenic for dogs, suggesting that canine clinical illness due to R. rickettsii has been unreported in Brazil and possibly in the other South American countries where BSF has been reported among humans.

Replication enhancer elements within the open reading frame of tick-borne encephalitis virus and their evolution within the Flavivirus genus

We provide experimental evidence of a replication enhancer element (REE) within the capsid gene of tick-borne encephalitis virus (TBEV, genus Flavivirus). Thermodynamic and phylogenetic analyses predicted that the REE folds as a long stable stem–loop (designated SL6), conserved among all tick-borne flaviviruses (TBFV). Homologous sequences and potential base pairing were found in the corresponding regions of mosquito-borne flaviviruses, but not in more genetically distant flaviviruses. To investigate the role of SL6, nucleotide substitutions were introduced which changed a conserved hexanucleotide motif, the conformation of the terminal loop and the base-paired dsRNA stacking. Substitutions were made within a TBEV reverse genetic system and recovered mutants were compared for plaque morphology, single-step replication kinetics and cytopathic effect. The greatest phenotypic changes were observed in mutants with a destabilized stem. Point mutations in the conserved hexanucleotide motif of the terminal loop caused moderate virus attenuation. However, all mutants eventually reached the titre of wild-type virus late post-infection. Thus, although not essential for growth in tissue culture, the SL6 REE acts to up-regulate virus replication. We hypothesize that this modulatory role may be important for TBEV survival in nature, where the virus circulates by non-viraemic transmission between infected and non-infected ticks, during co-feeding on local rodents.

Borreliose de Lyme

As borrelioses constituem um grupo de doenças infecciosas causadas por espiroquetas do gênero Borrelia. A borreliose de Lyme, também denominada doença de Lyme, é uma doença infecciosa, não contagiosa, causada por espiroquetas pertencentes ao complexo Borrelia burgdorferi Sensu Lato e transmitida, mais frequentemente, por picada de carrapatos do gênero Ixodes. A doença apresenta quadro clínico variado, podendo desencadear manifestações cutâneas, articulares, neurológicas e cardíacas.

Brazilian spotted fever: A reemergent zoonosis

Brazilian spotted fever is caused by the bacterium Rickettsia rickettsii, which is the most pathogenic species of the spotted-fever rickettsiae group and is transmitted by the bite of infected ticks. Amblyomma cajennense is the most important tick species involved in the cycle of this zoonosis in Brazil as it presents low host specificity, great number of natural reservoirs and wide geographic distribution. It was first described in the state of São Paulo in 1929 and later in Rio de Janeiro, Minas Gerais and Bahia. The number of cases decreased in the 1940's with the development of new plague control techniques and antibiotics. In the last decades, the number of new cases has increased. The current review aimed at reporting some of the epidemiological and public health aspects of this reemergent disease with new foci, mainly in the southeastern region of Brazil.