Immunisation of dogs, hamsters and guinea pigs against Rhipicephalus sanguineus using crude unfed adult tick extracts

Naive experimental groups of dogs, hamsters and guinea pigs were inoculated three times subcutaneously with unfed adult extract of the tick Rhipicephalus sanguineus and challenged with adult R. sanguineus to evaluate resistance. The acquisition of resistance was based on alterations of some reproductive and feeding performance parameters of female ticks such as female and egg mass weights, engorgement, pre-oviposition and incubation periods, larval hatchability rate and efficiency rates of female ticks in converting their food reservoir to eggs and larvae. Dogs did not develop resistance under these experimental conditions; guinea pigs and hamsters, to a lesser extent, acquired an effective immunity to ticks as demonstrated by the impairment of the reproductive and feeding performance. However, the resistance induced by inoculation of the extract in the rodents seemed not to be as efficient as that induced by successive infestations.

Western blot analysis of tick antigens from a Rhipicephalus sanguineus unfed larval extract and identification of antigenic sites in tick sections using immunohistochemistry. A comparative study between resistant and susceptible host species

Most parasite-host relationships are characterized by the development of resistance by the host, thus limiting the number of parasites. However, some cases are very unusual. In the relationship of the domestic dog with the brown dog-tick Rhipicephalus sanguineus this does not occur, whereas guinea pigs develop efficient resistance. Sera from domestic dogs, crab-eating foxes and guinea pigs collected before and after infestation with R. sanguineus ticks, and after immunization with a whole tick adult or larval homogenate, were used in Western blot analysis to compare and identify potential important antigens from a tick larval homogenate. The same sera were tested in an indirect immunohistochemistry assay in an attempt to compare relevant antigenic sites on histological tick sections. The immunoblotting displayed antigens recognized only by the guinea pigs, as well as several shared antigens between host species, depending on the kind of immunization. Immunohistochemistry revealed probable antigenic sites on the cells and tissues of ticks, which varied depending on the kind of immunization (infestation or vaccination) and the animal species involved.

An enzyme-linked immunosorbent assay (elisa) for the detection of antibodies against babesia boris in cattle

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structure of tick anticoagulant peptide at 1.6 Å resolution complexed with bovine pancreatic trypsin inhibitor

The structure of tick anticoagulant peptide (TAP) has been determined by X-ray crystallography at t.6 Å resolution complexed with bovine pancreatic trypsin inhibitor (BPTI). The TAP-BPTI crystals are tetragonal, a = b = 46.87, c = 50.35 Å, space group P41, four complexes per unit cell. The TAP molecules are highly dipolar and form an intermolecular helical array along the c-axis with a diameter of about 45 Å. Individual TAP units interact in a head-to-tail fashion, the positive end of one molecule associating with the distal negative end of another, and vice versa. The BPTI molecules have a uniformly distributed positively charged surface that interacts extensively through 14 hydrogen bonds and two hydrogen bonded salt bridges with the helical groove around the helical TAP chains. Comparing the structure of TAP in TAP-BPTI with TAP bound to factor Xa(Xa) suggests a massive reorganization in the N-terminal tetrapeptide and the first disulfide loop of TAP (CyS5(T)- Cys 15(T)) upon binding to Xa. The Tyr1(T)OH atom of TAP moves 14.2 Å to interact with Asp189 of the S1 specificity site, Arg3(T)CZ moves 5.0 Å with the guanidinium group forming a cation-π-electron complex in the S4 subsite of Xa, while Lys7(T)NZ differs in position by 10.6 Å in TAP-BPTI and TAP-Xa, all of which indicates a different pre-Xa-bound conformation for the N- terminal of TAP in its native state. In contrast to TAP, the BPTI structure of TAP-BPTI is practically the same as all those of previously determined structures of BPTI, only arginine and lysine side-chain conformations showing significant differences.

Ticks associated with wild animals in the Nhecolândia Pantanal, Brazil

A study of ticks associated with wild animals was carried out from September 1996 to April 1998 at the Fazenda Alegria (21,000 ha), in the Nhecolândia Pantanal, State of Mato Grosso do Sul, Brazil, a sunken plain bordering the upper Paraguay river, located 19 × 08′S; 56 × 46′W. A total of 81 wild animals (13 species, 6 orders) were captured with the aid of nets, and ticks were found on 63 (78%). Tick species identified included Boophilus microplus (Canestrini), Amblyomma cajennense (F.), A. parvum (Aragão), A. pseudo-concolor (Aragão), A. scalpturatum (Neumann), A. nodosum (Neumann), A. ovale (Koch), and A. tigrinum (Koch). Dragging from grasslands (campos) yielded negative results compared to the high concentration of ticks, mainly nymphs, that were collected from leaves in the forests (capão). Predominance of immature instars (Amblyomma genera) was observed in the end of winter (August-September). Ticks were associated mainly with coatis, deer (Mazama gouazoubira) and anteater, and these animals may play a role in the epidemiology of tick-transmitted pathogens in the Pantanal if one considers their coexistence with local domestic animals.

Skin test and tick immune status in susceptible and resistant cattle in Brazil

A cutaneous hypersensitivity test (CHT) was used to correlate host resistance to ticks and type of reaction elicited to unfed larval extract-ULE of the cattle tick Boophilus microplus in European and Indian cattle. Twenty calves were separated into four groups of five animals each: naïve or preinfested Indian or European cattle. CHT was induced by intradermal inoculation of 0.1 ml of ULE cattle tick B. microplus (50 μg protein) in the calf ear. Ear thickness was measured using calipers before and 10 min, 1, 2, 6, 18, 24, 48, 72, 96, and 144 h postinoculation (PI). Preinfested European calves showed only an immediate type reaction with maximum response (75% increase in ear thickness) at 10 min PI. On the other hand, preinfested Indian calves presented an immediate response with maximum reaction (70% increase in ear thickness) between 10 min and one hour PI, and a delayed type reaction at 72 h PI (60% increase in ear thickness). These results point out the crucial role of the cellular immune response of cattle in the expression of resistance to cattle tick B. microplus. Skin test might be useful in the ranking of cattle according to the susceptibility/resistance to ticks.

Avaliação clínica e hematológica em bezerros Nelore infectados experimentalmente com isolados de Babesia bigemina das regiões Sudeste, Nordeste e Norte do Brasil

A comparative study was made regarding the clinical and hematological alterations caused by isolates of Babesia bigemina from southeastern, northeastern and northern Brazil in experimentally infected Nelore calves. Eighteen calves between 7 and 9 months of age, without antibodies against Babesia sp and raised free from ticks, were used. Three animals were previously inoculated with 2.0×109 parasitic erythrocytes (PE) for each stabilate. The other 15 calves were subdivided into three groups, with five animals each, that were subinoculated with 1.0×1010 PE of the respective isolates. The clinical and hematological alterations were evaluated by the determination of parasitaemia, haemogram, plasmatic fibrinogen, reticulocyte count, descriptive analysis of the bone marrow and erythrocytic osmotic fragility, for 30 days, totalizing seven moments of observation. The follow-up of the immunological response by the indirect fluorescent antibody test was carried out daily until the 10th day after inoculation (DAI) and after that, on the 15th, 20th, 25th and 30th DAI. A mild clinical manifestation of the disease was observed. The laboratory findings revealed low levels of parasitaemia; decrease of the erythrogram values; absence of reticulocytes, initial decrease in the total count of leukocytes, neutrophils and lymphocytes with a posterior elevation of the number of these cells; hypercellularity of the erythrocytic series and decrease of the myeloid: erythroid relation which was more accentuated between the 8th and 12th DAI, and an increase of the erythrocytic osmotic fragility in the groups inoculated with the Southeast and Northeast isolates. None of the three isolates of B. bigemina gave rise to the clinical characteristic form of the disease, although they induced an humoral immune response.

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.

Ehrlichiosis in anemic, thrombocytopenic, or tick-infested dogs from a hospital population in South Brazil

Ehrlichia canis has a worldwide distribution, but clinical manifestations may vary geographically. We selected 129 dogs to determine prevalence of ehrlichiosis in dogs with anemia, thrombocytopenia, or ticks presented to a Veterinary Teaching Hospital in South Brazil. Of the 129 dogs, 68 carried the brown dog tick (Rhipicephalus sanguineus), 61 had thrombocytopenia (platelet count <150,000/μl), and 19 had anemia (PCV < 22%). Twenty dogs fulfilled more than one inclusion criteria. Ehrlichiosis was diagnosed by positive amplification of ehrlichial DNA by PCR using primers ECC and ECB that amplify a sequence of the 16S rRNA gene. Presence of E. canis was confirmed by cleavage of the amplified DNA using endonucleases HaeIII and AvaI. Fourteen of 68 (21%) dogs with ticks had ehrlichiosis, whereas 12 of 61 (20%) dogs presented with thrombocytopenia and 4 of 19 (21%) anemic dogs had ehrlichiosis. Similar results were obtained in dogs with thrombocytopenia and anemia (one of eight positive) and in dogs with thrombocytopenia and ticks (two of seven positive). All four dogs with anemia and ticks, and the dog that fulfilled all inclusion criteria yield no amplification of ehrlichial DNA by PCR. Based on our results, one in each five dogs infested by the brown dog tick, with anemia or thrombocytopenia had ehrlichosis. Contrary to widespread believe, ehrlichiosis was not the main cause for thrombocytopenia in our region. © 2003 Elsevier B.V. All rights reserved.

Demodicose bovina no estado da Paraíba

Cases of bovine demodicosis caused by Demodex bovis were reported in a Sindhi herd from December 1989 to January 1992. Both localized and generalized forms were diagnosed. This is the first report of the generalized form in Brazil. In the first two years, demodicosis was diagnosed only in cattle < 2 years old, whereas animals of all ages were positive in the last two years. Prevalence varied from 20.4% (11/54) to 53.1% (26/49) and 13.2% (12/91) to 14.8% (9/61) for cattle < 2 years old and > 2 years old, respectively. Clinical signs varied from a few small nodules to a thickened skin with soft large nodules in the localized and generalized forms, respectively. Main microscopic features of the nodules in the generalized form consisted of acanthosis with hyperqueratosis, chronic sebaceous adenitis, subcutaneous muscular necrosis, focal cellular degeneration of the epidermis basal layer and presence of large number of mites inside the lumen of dilated hair follicles. In addition, a chronic perifoliculitis was observed, characterized by lymphoplasmocytic infiltrate which also contained macrophages and neutrophils. It is suggested that poor nutrition and stress due to prolonged drought probably contributed to the increase of susceptibility of the herd to mite infestation.

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.

PCR-based detection of Babesia bovis and Babesia bigemina in their natural host Boophilus microplus and cattle

PCR and nested-PCR methods were used to assess the frequency of Babesia bovis and Babesia bigemina infection in Boophilus microplus engorged females and eggs and in cattle reared in an area with endemic babesiosis. Blood and the engorged female ticks were from 27 naturally infested calves and 25 crossbred cows. The frequency of both Babesia species was similar in calves and cows (P > 0.05). Babesia bovis was detected in 23 (85.2%) calves and in 25 (100%) cows and B. bigemina was detected in 25 (92.6%) calves and in 21 (84%) cows. Mixed infections with the both Babesia species were identified in 42 animals, 21 in each age category. Of female ticks engorged on calves, 34.9% were negative and single species infection with B. bigemina (56.2%) was significantly more frequent (P < 0.01) than with B. bovis (4.7%). Most of the females (60.8%) engorged on cows did not show Babesia spp. infection and the frequency of single B. bovis infection (17.6%) was similar (P > 0.05) to the frequency of single B. bigemina infection (15.9%). Mixed Babesia infection was lower (P < 0.01) than single species infection in female ticks engorged either in cows (5.7%) or in calves (4.3%). An egg sample from each female was analysed for the presence of Babesia species. Of the egg samples from female ticks infected with B. bovis, 26 (47.3%) were infected while from those from female ticks infected with B. bigemina 141 (76.6%) were infected (P < 0.01). The results showed that although the frequency of both species of Babesia was similar in calves and cows, the infectivity of B. bigemina was higher to ticks fed on calves while to those ticks fed on cows the infectivity of both Babesia species was similar. © 2004 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

A new species of Pterodectes Robin, 1877 (Proctophyllodidae: Pterodectinae) from the pale-breasted thrush, Turdus leucomelas (Passeriformes: Turdidae)

A new species of feather mite, Pterodectes fissuratus sp. n., is described from the pale-breasted thrush, Turdus leucomelas Veillot (Passeriformes: Turdidae), in Brazil. This species is easily distinguished by having numerous well-pronounced lacunae and a longitudinal median furrow on prodorsal and hysteronotal shields in both sexes. Copyright © 2005 Magnolia Press.

Éster de sacarose no controle do Varroa estructor em abelhas africanizadas

This study aimed to determine the effect of sucrose ester on the control of Varroa destructor mite infestation in Africanized honeybees. For the in vitro experiments, the product was tested in bees and mites at five concentrations obtained through dilution in water (T0: 100% distilled water; T1: 0.5%; T2: 1%; T3: 2%; T4: 5%; and T5: 10% sucrose ester).For the field studies, the experimental design was completely randomized, with four treatments and seven replicates, totaling 28 colonies, from which seven were the controls, seven were treated with 0.1% sucrose ester, seven with 0.2% sucrose ester, and seven hives with 0.5% sucrose ester diluted in water. In the in vitro study, the sucrose ester at 0.5% concentration caused mite and bee mortality. In the field tests, the product at 0.2% concentration reduced Varroa destructor infestation in Africanized honeybees and, therefore, may be used as a tool to control this pest. At 0.1, 0.2, and 0.5% concentrations, sucrose ester did not impair the establishment of open and capped brood areas, as well as stored food areas in the hive, suggesting it is not toxic to Africanized honeybees.

Flower mites decrease nectar availability in the rain-forest bromeliad Neoregelia johannis

Nectarivorous flower mites can reduce the volume of nectar available to pollinators. The effects of the flower mite Proctolaelaps sp. on nectar availability in flowers of a melittophilous bromeliad Neoregelia johannis (Bromeliaceae) was evaluated in a coastal rain forest in south-eastern Brazil. In a randomized block experiment utilizing 18 flower pairs, one per bromeliad ramet, pollinators (Bombus morio) and mites were excluded, and then nectar volume, sugar concentration and sugar mass were quantified over the anthesis period. Mites significantly reduced nectar volume early in the morning (6h00-8h00), but not later (10h00-12h00). Mites decreased total volume of nectar available up to 22%. Sugar concentration in nectar was higher earlier in the morning, and decreased between 10h00-12h00. The pronounced consumption of nectar by mites during the period of higher sugar concentration reduced the total amount of sugar available to pollinators by 31%. This is the first study showing that flower mites decrease nectar rewards in a melittophilous plant. Because nectar volume by itself incompletely describes nectar production rates and the effects of nectar removal by flower mites on the availability of sugar, our study highlights the inclusion of sugar content in future studies assessing the effects of thieves on nectar production rates. Copyright © 2010 Cambridge University Press.