Comparison of two methods for collecting free-living ticks in the Amazonian forest

In the present study, we compared 2 methods for collecting ixodid ticks on the verges of animal trails in a primary Amazon forest area in northern Brazil. (i) Dragging: This method was based on passing a 1-m(2) white flannel over the vegetation and checking the flannel for the presence of caught ticks every 5-10 m. (ii) Visual search: This method consisted of looking for guesting ticks on the tips of leaves of the vegetation bordering animal trails in the forest. A total of 103 adult ticks belonging to 4 Amblyomma species were collected by the visual search method on 5 collecting dates, while only 44 adult ticks belonging to 3 Amblyomma species were collected by dragging on 5 other collecting dates. These values were statistically different (Mann-Whitney Test, P = 0.0472). On the other hand, dragging was more efficient for subadult ticks, since no larva or nymph was collected by visual search, whereas 18 nymphs and 7 larvae were collected by dragging. The visual search method proved to be suitable for collecting adult ticks in the Amazon forest: however, field studies should include a second method, such as dragging in order to maximize the collection of subadult ticks. Indeed, these 2 methods can be performed by a single investigator at the same time, while he/she walks on an animal trail in the forest. (C) 2010 Elsevier GmbH. All rights reserved.

Cellular and molecular characterization of an embryonic cell line (BME26) from the tick Rhipicephalus (Boophilus) microplus

The cellular and molecular characteristics of a cell line (BME26) derived from embryos of the cattle tick Rhipicephalus (Boophilus) microplus were studied. The cells contained glycogen inclusions, numerous mitochondria, and vesicles with heterogeneous electron densities dispersed throughout the cytoplasm. Vesicles contained lipids and sequestered palladium meso-porphyrin (Pd-mP) and rhodamine-hemoglobin, suggesting their involvement in the autophagic and endocytic pathways. The cells phagocytosed yeast and expressed genes encoding the antimicrobial peptides (microplusin and defensin). A cDNA library was made and 898 unique mRNA sequences were obtained. Among them, 556 sequences were not significantly similar to any sequence found in public databases. Annotation using Gene Ontology revealed transcripts related to several different functional classes. We identified transcripts involved in immune response such as ferritin, serine proteases, protease inhibitors,. antimicrobial peptides, heat shock protein, glutathione S-transferase, peroxidase, and NADPH oxidase. BME26 cells transfected with a plasmid carrying a red fluorescent protein reporter gene (DsRed2) transiently expressed DsRed2 for up to 5 weeks. We conclude that BME26 can be used to experimentally analyze diverse biological processes that occur in R. (B.) microplus such as the innate immune response to tick-borne pathogens. (C) 2008 Elsevier Ltd. All rights reserved.

Diagnoses of fipronil resistance in Brazilian cattle ticks (Rhipicephalus (Boophilus) microplus) using in vitro larval bioassays

Fipronil is a phenylpyrazolic insecticide that is widely used in agriculture and has been recently used to control the cattle tick, Rhipicephalus (Boophilus) microplus. Because of the serious problems associated with resistance to the available acaricides, this product has been used as an important alternative to control acaricide-resistant ticks. The objective of this work was to analyse the fipronil sensitivity of ticks that were collected from farms with a history of fipronil use by larval bioassays. A total of 11 Brazilian tick populations were studied: one population from Rio Grande do Sul, one population from Mato Grosso do Sul and nine populations from Sao Paulo. To validate the assays, susceptible reference strains, POA (Porto Alegre, Brazil) and Mozo (Dilave, Uruguay), and ticks from six different farms that never used fipronil were tested. The resistance of various tick populations to technical grade fipronil (95.3%) was primarily evaluated using the larvae immersion test (LIT) and the larval packet test (LPT), when a sufficient number of larvae was collected. Using the LIT, the resistance ratios (RR(50)) of the tick populations from Rio Grande do Sul and Mato Grosso do Sul were 14.9 and 2.6, respectively, and the populations derived from Sao Paulo had RR(50)s ranging from 2.5 to 6.9. Four populations were evaluated with the LPT, and two populations displayed lower RR(50), while other populations displayed higher RR(50) than those determined by the LIT. This article reports the first cases of fipronil resistance in Brazil and highlights the LIT as a more sensitive technique for the evaluation of fipronil resistance in R. (B) microplus ticks. We suggest the use of the LIT as an evaluation tool for monitoring fipronil resistance in the control programmes of R. (B) microplus. (C) 2010 Elsevier B.V. All rights reserved.

Antibody and blood leukocyte response in Rhipicephalus sanguineus (Latreille, 1806) tick-infested dogs and guinea pigs

The dog is considered to be the natural host of Rhipicephalus sanguineus and is unable to develop appreciable resistance even after repeated feedings. The guinea pig develops strong resistance after one infestation with adult ticks. Antibody (IgG) titres against tick salivary gland antigens (SGAs) and blood leukocyte numbers in dogs and guinea pigs undergoing experimental R. sanguineus tick infestations were measured to detect a possible correlation with susceptibility or resistance of hosts. Since infested dogs develop an immediate hypersensitivity reaction to R. sanguineus antigens, total and anti-R. sanguineus SGA IgE levels were also measured in this host species. IgG and IgE antibody levels were determined by an enzyme-linked immunosorbent assay (ELISA) along three consecutive infestations of both hosts. Most dogs and guinea pigs displayed low IgG levels against R. sanguineus SGAs, though marked differences in individual response were observed. Although dog's total serum IgE levels increased significantly after infestations, no change in the amount of anti-salivary gland IgE was detected. Total and differential blood cell counts were determined in dogs and guinea pigs during primary and secondary infestation. In dogs, a tertiary infestation and a subsequent higher infestation level were also evaluated. Infested dogs did not display any alteration in blood leukocyte counts throughout the experiment. Guinea pigs, on the other hand, developed a significant basophilia during primary infestation which increased further during secondary infestation. These data reveal similarities and differences in the reactions of resistant and non-resistant hosts to ticks. They contribute for the understanding of such host-parasite relationships and will hopefully aid in the development of immune control of ticks. (C) 2003 Elsevier B.V. All rights reserved.

The first reported case of human tick paralysis in Brazil: a new induction pattern by immature stages

Tick paralysis (TP) is a rare disease with rapid progression and potential fatal evolution. Immediately after the diagnosis, removal of all ticks from the body of the patient is mandatory. The present study reports for the first time a human case of the disease in Brazil. The patient had loss of muscle strength, decreased reflexes and marked palpebral ptosis. Six hours after removal of the last tick, the ptosis improved and on the following day, the patient had near total regression of the symptoms. This report emphasizes the possible presence of similar cases that should be promptly diagnosed and quickly treated. A new induction pattern for TP in humans associated with immature stages of ticks is also presented.

Caracterização da população de ectoparasitos em cães de núcleos de expansão urbana de Juiz de Fora, Minas Gerais, Brasil

No presente trabalho caracterizou-se a população de ectoparasitos em cães de núcleo de expansão urbana de Juiz de Fora, MG. As coletas foram realizadas de julho a setembro de 2003, examinando-se 101 cães SRD (sem raça definida). Os ectoparasitos foram coletados através de inspeção visual e tátil dos animais e acondicionados em frascos com etanol 70°GL e identificados sob estereoscopia. Espécimes foram clarificados e montados para análise em microscopia fotônica. Dentre os sifonápteros, Ctenocephalides felis foi mais prevalente (64,35%) com intensidade média de 6,12 ± 5,37 sifonápteros/cão, seguido por Rhopalopsyllus lutzi (3,96%), híbrida C. felis X C. canis (1,98%), Tunga penetrans (1,98%). Aúnica espécie de fitiráptero encontrada foi Trichodectes canis (7,92%) com 1,3 ± 0,51 fitiráptero/cão. Dentre os ixodídeos, Rhipicephalus sanguineus foi a espécie mais prevalente (49,50%) com intensidade média de 6,44 ± 10,2 ixodídeos/ cão, seguido por Amblyomma cajennense (3,96%), Boophilus microplus (2,97%), A. ovale (1%) e A. aureolatum (1%). As ninfas de ixodídeos foram separadas em ninfas de Amblyomminae (58,41%) com 10,11 ± 10,09 ninfas/cão e ninfas Rhipicephalinae (24,75%) com 2,64 ± 3,25 ninfas/cão. em 3,96 % dos cães foram encontradas larvas de ixodídeo.

Histopathology of tick-bite lesions in naturally infested capybaras (Hydrochoerus hydrochaeris) in Brazil

In the present work features of tick-bite lesions were evaluated in capybaras naturally infested with Amblyomma cajennense and Amblyomma dubitatum ticks. Gross appearance of tick bite site was characterized by a mild swelling and erythema. Microscopic examination revealed the cement cone, a tube-like homogenous eosinophilic mass penetrating deep into the dermis. This structure was surrounded in the dermis by a cellular infiltrate and free eosinophilic granules and was associated to edema of variable intensity. Necrosis was a common feature deep in the dermis particularly at the far end of the eosinophilic tube. Hyperplasia, cellular edema and occasionally necrosis of keratinocytes could be seen at both sides of the ruptured epidermis. Cellular infiltrate was constituted overwhelmingly by polymorphonuclear leukocytes with eosinophilic granules. In capybaras cells with such features can be either eosinophils or heterophils (pseudoeosinophils), the latter being the equivalent of neutrophils of other mammals. Ultrastructural analysis of the cellular infiltrate revealed the predominance of heterophils over eosinophils. Mononuclear cells and mast cells and, in lesser numbers, basophils were also seen at skin attachment sites. The presence of heterophils in the reaction of capybaras against Amblyomma ticks is an outstanding feature but its role in the reaction to the tick is not known. It is however speculated that capybara heterophils might be associated with a more permissive environment for tick feeding and pathogen transmission as already shown for the equivalent cell type, the neutrophil, in the reaction of the dog against the Rhipicephalus sanguineus tick.

Acquired resistance of horses to Amblyomma cajennense (Fabricius, 1787) ticks

Acquired immunity of horses to larvae, nymphs and adults of the Amblyomma cajennense tick was evaluated through three consecutive experimental infestations of tick-bite naive hosts. Data from these infestations were compared to those from field-sensitized horses and donkeys. It was observed that tick-bite naive horses developed a low level of resistance after two infestations as shown by a significant decrease in larval yield and a tendency for lower engorged weight of nymphs during third infestation. Ticks fed on field-sensitized horses had a similar biological performance to that observed on the third infestation of tick-bite naive horses but the mean engorged nymph weight was significantly lower than that of the first infestation from tick-bite naive horses. Donkeys presented the strongest resistance with significantly lower engorged weights of all instars and of the egg mass compared to the first infestation of tick-bite naive horses. Donkeys also displayed a significantly higher resistance than field-sensitized horses as demonstrated by significantly lower egg mass weights. Overall these results indicate that donkeys but not horses maintain a strong resistance to A. cajennense ticks. The importance of these findings in relation to vectoring of tick-borne diseases is discussed. (C) 2003 Elsevier B.V. All rights reserved.

Antigens from Rhipicephalus sanguineus ticks elicit potent cell-mediated immune responses in resistant but not in susceptible animals

In the present study we compared the immunological reactions between Rhipicephalus sanguineus tick-infested susceptible (dogs and mice) and tick-resistant hosts (guinea pigs), elucidating some of the components of efficient protective responses against ticks. We found that T-cells from guinea pigs infested with adult ticks proliferate vigorously in the presence of concanavalin A (ConA), whereas ConA-induced cell proliferation of tick-infested mice and dogs was significantly decreased at 43.1 and 94.0%, respectively, compared to non-infested controls. Moreover, cells from mice and dogs submitted to one or three successive infestations did not exhibit a T-cell proliferative response to tick antigens, whilst cells from thrice tick-infested guinea pigs, when cultured with either a tick extract or tick saliva, displayed a significant increase in cell proliferation. Also, we evaluated the response of tick-infested mice to a cutaneous hypersensitivity test induced by a tick extract. Tick-infested mice developed a significant immediate reaction, whereby a 29.9% increase in the footpad thickness was observed. No delayed-type hypersensitivity (DTH) reaction was detected. Finally, the differential cell count at the tick attachment site in repeatedly infested mice exhibited a 6.6- and 4.1-fold increase in the percentage of eosinophils and neutrophils, respectively, compared to non-infested animals, while a decrease of 77.0-40.9 in the percentage of mononuclear cells was observed. The results of the cutaneous hypersensitivity test and the cellular counts at the tick feeding site for mice support the view that tick-infested mice develop an immune response to R. sanguineus ticks very similar to dogs, the natural host of this species of tick, but very different from guinea pigs (resistant host), which develop a DTH reaction in addition to a basophil and mononuclear cell infiltration at the tick-attachment site. In conclusion, saliva introduced during tick infestations reduces the ability of a susceptible animal host to respond to tick antigens that could stimulate a protective immune response. As a consequence, the animals present a lack of DTH response and disturbed cellular migration to tick feeding site, which can represent a deficient response against ticks. © 2003 Elsevier B.V. All rights reserved.

Amblyomma cajennense ticks induce immediate hypersensitivity in horses and donkeys

Since host immune reaction to ticks interferes with tick-borne pathogen transmission, it is important to recognize naturally occurring tick-host immune relationships to better understand the epidemiology of such infectious diseases. Amblyomma cajennense is an important tick-borne disease vector in the Neotropical region and horses maintain it in domestic environments. In the present work intradermal testing of A. cajennense tick exposed horses and donkeys using crude tick antigens was used to evaluate the type of hypersensitivity induced by infestations. Animals sensitized by A. cajennense infestation displayed an immediate hypersensitivity reaction at the antigen inoculation site. Foals sensitized with experimental infestations and field sensitized horses presented the most intense reactions (40% of ear thickness increase). Field sensitized donkeys presented less intense reaction reaching no more than 22% of mean thickness increase. Control horses (non-sensitized) had the least intense reaction, with a peak of no more 12% of increase. The presence of a prominent immediate hypersensitivity in equids sensitized experimentally or by field infestations indicates that A. cajennense ticks induce in this host an immune response that is associated with IgE production and which is known to be inappropriate against intracellular pathogens. Differences observed between horses and donkeys are discussed.

Morphological description of the nymphal stage of Amblyomma geayi and new nymphal records of Amblyomma parkeri

The external morphology of the nymph of Amblyomma geayi Neumann is described by optical and scanning electron microscopy. Unfed nymphs were obtained from an engorged A. geayi female, which had been collected on a sloth (Bradypus variegatus) from Belém municipality, State of Pará, northern Brazil, and was kept under laboratory conditions. With the present description, we propose a modification of a taxonomic key published in 2010 for the Amblyomma nymphs that occur in Brazil, through the inclusion of A. geayi. The nymph of A. geayi is morphologically very similar to the nymph of Amblyomma parkeri Fonseca and Aragão, with only slight morphological differences related to scutal surface and punctuations (more shagreened and less punctuated in A. geayi). These 2 nymphs differ from all other known Amblyomma nymphs from Brazil by the combination of auriculae present as small posterolateral rounded projections, eyes located at the level of the scutal midlength, and a rounded hypostome. These nymphal similarities as well the morphology of the adult stage corroborate previous studies that showed that A. geayi and A. parkeri are genetically closely related. Unpublished host records of the nymphs of both A. geayi and A. parkeri are provided. Established populations of A. geayi and A. parkeri seem to be geographically separated, since all confirmed records of A. geayi are from the northern half of South America (mainly the Amazonian region) and Central America, whereas all known records of A. parkeri are from the Atlantic rainforest biome in northeastern, southeastern, and southern Brazil. © 2013 Elsevier GmbH.

Descrição morfo-histológica dos testículos de Amblyomma cajennense em jejum e alimentados

Os carrapatos são ectoparasitas hematófagos de grande importância epidemiológica, pois são vetores de muitos patógenos. Esses animais pertencem ao Filo Arthropoda, Classe Arachnida, Subclasse Acari, são classificados em três famílias: Ixodidae, Argasidae e Nutalliellidae, apresentam ampla distribuição geográfica e podem parasitar grande variedade de vertebrados, inclusive o homem. O carrapato da espécie Amblyomma cajennense, popularmente conhecido como carrapato-estrela, carrapato do cavalo ou rodoleiro, tem grande importância médica por ser vetor da bactéria Rickettsia rickettsii, causadora da febre maculosa brasileira (FMB), que pode levar o hospedeiro a óbito. Apesar das crescentes pesquisas com esses animais, ainda existem lacunas na literatura acerca de alguns de seus processos reprodutivos. Dessa forma, esse trabalho teve por objetivo estudar o desenvolvimento dos testículos dessa espécie por meio da descrição da morfologia e histologia dos testículos de indivíduos em jejum e alimentados, identificando a dinâmica do processo de espermatogênese e se a alimentação influencia nesse processo. Os resultados obtidos mostraram que os testículos são estruturas pares e tubulares arranjadas dorsolateralmente no opistossoma, sendo que a região proximal está conectada às vesículas seminais pelos ductos deferentes, semelhante ao observado em outras espécies de ixodídeos. Associado ao aparelho genital masculino encontra-se um complexo de glândulas acessórias multilobuladas. Foi constatado que a alimentação tem papel fundamental no desenvolvimento do sistema reprodutor, visto que nos indivíduos em jejum as vesículas seminais e o complexo de glândulas acessórias foram menores e menos desenvolvidos do que nos animais alimentados. Além disso, as espermátides alongadas, precursoras dos espermatozoides no trato reprodutor... (Resumo completo, clicar acesso eletrônico abaixo)

Experimental infection of the tick Amblyomma cajennense, Cayenne tick, with Rickettsia rickettsii, the agent of Rocky Mountain spotted fever

In the laboratory, Amblyomma cajennense (Acari: Ixodidae) (Fabricius) larvae, nymphs and adults were exposed to Rickettsia rickettsii by feeding on needle-inoculated animals, and thereafter reared on uninfected guinea pigs or rabbits. Regardless of the tick stage that acquired the infection, subsequent tick stages were shown to be infected (confirming transstadial and transovarial transmissions) and were able to transmit R. rickettsii to uninfected animals, as demonstrated by serological and molecular analyses. However, the larval, nymphal and adult stages of A. cajennense were shown to be partially refractory to R. rickettsii infection, as in all cases, only part of the ticks became infected by this agent, after being exposed to rickettsemic animals. In addition, less than 50% of the infected engorged females transmitted rickettsiae transovarially, and when they did so, only part of the offspring became infected, indicating that vertical transmission alone is not enough to maintain R. rickettsii in A. cajennense for multiple generations. Finally, the R. rickettsii-infected tick groups had lower reproductive performance than the uninfected control group. Our results indicate that A. cajennense have a low efficiency to maintain R. rickettsii for successive generations, as R. rickettsii-infection rates should decline drastically throughout the successive tick generations.

Coxiella symbiont in the tick Ornithodoros rostratus (Acari: Argasidae)

In the present study, the presence of tick-associated bacteria and protozoa in Ornithodoros rostratus ticks (adults, nymphs, and eggs) from the Pantanal region of Brazil were determined by molecular detection. In these ticks, DNA from protozoa in the genera Babesia and Hepatozoon, and bacteria from the genera Rickettsia, Borrelia, Anaplasma, and Ehrlichia were not detected. Conversely, all tested ticks (100%) yielded PCR products for 3 Coxiella genes (16S rRNA, pyrG, cap). PCR and phylogenetic analysis of 3 amplified genes (16S rRNA, pyrG, cap) demonstrated that the agent infecting O. rostratus ticks was a member of the genus Coxiella. This organism grouped with Coxiella symbionts of other soft tick species (Argasidae), having different isolates of C. burnetii as a sister group, and these 2 groups formed a clade that grouped with another clade containing Coxiella symbionts of hard tick species (Ixodidae). Analysis of tick mitochondrial 16S rRNA gene database composed mostly of tick species previously shown to harbor Coxiella symbionts suggests a phylogenetic congruence of ticks and their Coxiella symbionts. Furthermore, these results suggest a very long period of coevolution between ticks and Coxiella symbionts and indicates that the original infection may have occurred in an ancestor common to the 2 main tick families, Argasidae (soft ticks) and Ixodidae (hard ticks). However, this evolutionary relationship must be confirmed by more extensive testing of additional tick species and expanded populations. (c) 2012 Elsevier GmbH. All rights reserved.

Rickettsia bellii in ticks Amblyomma varium Koch, 1844, from birds in Peru

Amazonian birds were caught and examined for the presence of ectoparasites in the Allpahuayo Mishana National Reserve near Iquitos, Peru, from 13 to 16 August 2011. A total of 40 birds representing 16 species were examined. Two birds (5%) were infested with 2 larvae of Amblyomma varium Koch, 1844, and one nymph of A. calcaratum Neumann, 1899. The 2 larvae of A. varium were infected with Rickettsia bellii. This is the first report of R. bellii in A. varium and also the first record of this rickettsia in Peru. In addition, an immature A. calcaratum is reported from Peru for the first time. (c) 2012 Elsevier GmbH. All rights reserved.