CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / No Brasil, a maioria das viroses transmitidas por artrópodes (arboviroses) pertence ao gênero Flavivirus, no entanto, aqueles transmitidos por carrapatos são menos estudados do que os transmitidos por insetos. Além dos vírus, outros microrganismos possuem grande relevância em saúde pública. Riquétsias são os principais agentes de zoonoses transmitidas por carrapatos no Brasil, especialmente as do Grupo da Febre Maculosa (GFM), que inclui diversas espécies patogênicas e que são transmitidas por carrapatos. Dentre os diversos biomas, dois foram particularmente degradados no Brasil, a Mata Atlântica e o Cerrado. Diante destes motivos, esta tese compõe-se de três capítulos, que tiveram como objetivo identificar carrapatos vetores em áreas do Cerrado e Mata Atlântica adjacentes a áreas com atividade humana, pesquisando por patógenos causadores de zoonoses, Rickettsia spp. e Flavivirus. No primeiro capítulo, a presença de riquétsias foi averiguada em carrapatos de cães e carnívoros da região de Cumari-GO. Pesquisou-se por esse microrganismo em oito espécies de carnívoros silvestres e em cães domésticos. Duas amostras amplificaram fragmentos do gene ompB, presente em riquétsias do GFM, e ao mesmo tempo amplificaram fragmentos específicos para Rickettsia bellii, que não pertence a esse grupo. Isso demonstra uma possível infecção cruzada, podendo o carrapato manter concomitantemente estas duas espécies divergentes. O segundo capítulo, dados de carrapatos de tamanduás (Myrmecophaga tridactyla e Tamandua tetradactyla) referentes a um período de 18 anos foram analisados, 169 amostras foram avaliadas quanto à presença de riquétsias. Quatro destas amostras exibiram sequência de ompA com 100% de identidade com outras sequências de carrapato Amblyomma nodosum, indicando que Rickettsia spp. do grupo da febre maculosa (SFG) em Amblyomma nodosum estava circulando no entorno da cidade de Uberlândia e estado de São Paulo, podendo outros carrapatos, tais como A. sculptum serem infectados, gerando risco para animais domésticos e seres humanos. No último capítulo, carrapatos de seis áreas, uma pertencente à Mata Atlântica e as outras do bioma Cerrado, foram avaliados quanto à presença de Flavivirus. Nestes locais foram pesquisados carrapatos de doze espécies diferentes, sendo onze da família Ixodidae e um da família Argasidae, estes pertenciam às espécies: Amblyomma sculptum, Rhipicephalus sanguineus, Rhipicephalus microplus, Dermacentor nitens, Amblyomma ovale, Amblyomma dubitatum, Amblyomma parvum, Amblyomma rotundatum, Amblyomma incisum, Amblyomma brasiliense, Amblyomma naponense e Ornithodoros sp. Detectou-se a presença de um flavivírus em carrapatos R. microplus coletados na região de Uberlândia. Estas amostras exibiram aproximadamente 98% de identidade com o Vírus do Carrapato Mogiana (MGTV). Todos os carrapatos que exibiram resultados positivos para flavivírus ou riquétsias, foram coletados em áreas antropizadas, confirmando a importância do estudo de vetores hematófagos na epidemiologia de agentes virais e bacterianos de animais domésticos e selvagens. / In Brazil, most arthropod-transmitted viruses (arboviruses) belong to Flavivirus genus, being tick-transmitted less studied than insect-transmitted ones. Other microorganisms have great public health relevance, such as Rickettsia, the main agent of tick-borne diseases in Brazil, specially the Macular Fever (MF) group, which includes several pathogenic species that are transmitted by ticks. Within different biomes, both the Atlantic Forest and the Cerrado were severely degraded in Brazil. This thesis consisted of three chapters, aiming to identify ticks in areas of Cerrado and Atlantic Forest with surrounding human activity, looking for both Rickettsia and Flavivirus infected ticks. In the first chapter, the presence of Rickettsia was investigated in ticks from dogs and other carnivores, being eight wild carnivores species and domestic dogs in Cumari, Goiás state, Brazil. Two samples were positive for ompB gene, common in the MF group, being also positive for specific genes found in Rickettsia bellii, which does not belong to the MF group. This result shows a possible cross-infection, being tick able to maintain these two different species simultaneously. The second chapter, an 18- year-study-data from anteater ticks (Myrmecophaga tridactyla and Tamandua tetradactyla) was analyzed, accounting 169 samples evaluated for the presence of Rickettsia. Four samples were positive for ompA gene, being 100% identical to other tick sequences present in Amblyomma nodosum, indicating that Rickettsia from the MF group in A. nodosum was circulating around the city of Uberlândia and state of São Paulo. Other ticks, such as A. sculptum, could become infected by the Rickettsia presence, generating risk for domestic animals and humans. In the last chapter, ticks from six areas, being one from the Atlantic Forest and the others from the Cerrado biome, were evaluated for the presence of Flavivirus. 12 different species were accounted, in which eleven were from the Ixodidae family and one was from the Argasidae family, having the following species identified: Amblyomma sculptum, Rhipicephalus sanguineus, Rhipicephalus microplus, Dermacentor nitens, Amblyomma ovale, Amblyomma dubitatum, Amblyomma parvum, Amblyomma rotundatum, Amblyomma incisum, Amblyomma brasiliense, Amblyomma naponense and Ornithodoros sp. The presence of a Flavivirus in R. microplus ticks collected in the Uberlândia region was detected. These samples exhibited approximately 98% identity with the Mogiana Tick Virus (MGTV). All ticks that were positive for Flavivirus or Rickettsia were collected in areas with human activities, stating the importance of studies on hematophagous vectors in the epidemiology of both viral and bacterial agents in domestic and wild animals. / Tese (Doutorado)

Uma população experimental F2 foi desenvolvida a partir do cruzamento de quatro machos da raça Holandesa com vinte e oito fêmeas Gir, produzindo uma geração F1 com cento e cinqüenta animais, da qual quatro machos foram escolhidos baseados na sua fertilidade para acasalar com sessenta e oito fêmeas e produzir a geração F2 com aproximadamente quatrocentos indivíduos. Foram coletados dados fenotípicos para características de contagem de carrapatos, peso ao nascimento e peso a desmama para os animais da geração F2. Cerca de duzentos e noventa animais tiveram seu fenótipo medido para as características com exceção da contagem de carrapatos, onde somente cento e sessenta e sete animais foram medidos. As gerações parentais e F1 foram genotipadas para cinco marcadores microssatélites posicionados no cromossomo 23. Após a determinação do grau de informação dos marcadores, todos os animais da geração F2 disponíveis foram genotipados para os cinco marcadores. Com o resultado da genotipagem foi construído o mapa de ligação específico dos marcadores no cromossomo 23 para a população desenvolvida. Após o ajuste da característica de contagem de carrapatos pelo logaritmo da contagem e pela transformação rank, ambos ajustes foram utilizados para mapeamento de QTL pelo método de regressão por mínimos quadrados ordinários, utilizando o programa QTL Express. Não foi encontrado nenhum QTL associado a nenhuma das características estudadas. O pequeno número de animais avaliados para a característica de contagem de carrapatos pode ter influenciado o resultado, bem como um melhor ajuste ou mais variáveis que complementem essa característica. Outras análises devem ser realizadas com essa população, tanto para complementar este estudo como para realização de outros estudos sobre características relativas a resistência a ecto e endoparasitas. / A F2 design population had been developed from the breeding between four male holstein with twenty eight female Gir, generating a F1 with one hundred and fifty animals, from these sample four male have been chosen based on their fertility for matching. They have been breed with sixty eight females, producing the F2 generation with about four hundred individuals. Phenotypic data has been collected for tick accounting, birth weight and weight after sixty days for individuals on F2. Over than two hundred and ninety animals had their phenotypic measured for those characteristics with the exception of the tick accounting. On this case, only one hundred sixty seven were measured. The parental and F1 generations were genotyped for five microsatellite markers positioned on chromosome 23. After the determination of the markers information degree, all the F2 animals available were genotyped for the five markers. Under the genotyping results was constructed the linkage map for this markers on chromosome 23. After the log transformation for tick accounting and the rank transformation both adjusts was used for QTL mapping by the regression method based on minimum ordinary least squares, using the QTL Express software, were not found any QTL associated for any studied characteristics. The small sample of animals used for tick accounting could have biased the results. Other analyses must be taken over this population; not only to complete the present study, but also to create new sort of studies on characteristics related on ecto and endo parasites.

Made available in DSpace on 2014-07-29T15:13:54Z (GMT). No. of bitstreams: 1 Tese_Marcio_Pereira_Martins.pdf: 660888 bytes, checksum: 070c9552e0ed53121a6615f34c32ec29 (MD5) Previous issue date: 2009-12-21 / Rocky Mountain spotted fever (FM), a zoonosis transmitted to humans through the bite of ticks infected with Rickettsia spp. Especially R. rickettsii, emerged in the United States in the late 19th century, been taking place in Brazil in the mid 20th century. Since then, in Brazil the disease, initially diagnosed in São Paulo, became identified focally in some cities, getting to the end of the 20th century restricted states in the Southeast. Already at the beginning of the 21st century FM was first identified in Southern states, focusing in Santa Catarina and also, occasionally, been observed in rare cases that occurred in states in other regions of the country: State Federal, Bahia, Rondônia and Amapá. Given the above, and aiming to collaborate with the service of Epidemiology in Goias, this unprecedented study throughout the Midwest Region, proposes and creates conditions for the first milestone for the monitoring of FM in this State, by means of serological screening with indirect immunofluorescence assay (IFA) in sera of animals and humans, in addition to the research of tick vectors. This study took place in the city of Quirinópolis-GO, and despite not having been detected in the chain reaction polymerase (PCR), ticks infected with Rickettsia spp., the principal vector of FM in Brazil, the tick Amblyomma cajennense, was observed. In previous pilot study conducted in February 2007 in Quirinópolis-GO, serology by IFAT reagents detected in 25% (7 / 28) of humans in a group of individuals cohabiting with a suspected case of FM, which was notified to the Ministry of Health (MOH) of Brazil in 2006, and in 0% (0 / 5) of dogs and 28.6% (12/42) of horses from 3 rural property where the suspect case was before the manifestation of signs of illness. There were two horses positive sera in these three farms. Unable to trace the likely source of infection, but the findings here obtained allowed to suspect that the suspected case of FM has been in one of these two farms the likely source of antigenic contact with bacteria or micro-FM group antigenically similar. Already in scale epidemiological study horses, held in March 2007 on 20 farms, found the prevalence of positive sera of 11.6% (39/335) among horses and the frequency of seropositive 36.6% (15/41 ) between the human and 16.7% (2 / 12) among the dogs from these properties to create horses. Humans here tested HIV positive were asymptomatic for FM at the time of sample collection. It was concluded that the FM, or antigenically similar disease, may be occurring in the State of Goiás, in the City of Quirinópolis / A febre maculosa (FM), zoonose transmitida ao homem por meio da picada de carrapatos infectados com Rickettsia spp., especialmente R. rickettsii, surgiu nos Estados Unidos no final do século 19, vindo a ocorrer no Brasil em meados do século 20. Desde então, no Brasil a enfermidade, inicialmente diagnosticada no Estado de São Paulo, passou a ser identificada focalmente em vários municípios, ficando até o final do século 20 restrita aos Estados da Região Sudeste. Já no inicio do século 21 a FM começou a ser identificada em Estados da Região Sul, concentrando-se em Santa Catarina e também, pontualmente, sendo observada em raros casos ocorridos em Estados das demais regiões do país: Distrito Federal, Bahia, Amapá e Rondônia. Diante do exposto, e visando colaborar com o serviço de Epidemiologia em Goiás, o presente Estudo inédito em toda a Região do Centro-Oeste, se propõe e cria condições de marco inicial para a vigilância da FM neste Estado, por meio de inquérito sorológico com a reação de imunofluorescência indireta (RIFI) em soros de animais e humanos, além da pesquisa de carrapatos vetores. O presente estudo se deu no Município de Quirinópolis-GO, e apesar de não terem sido detectados, na reação em cadeia pela polimerase (PCR), carrapatos infectados com Rickettsia spp., o principal vetor de FM no Brasil, o carrapato Amblyomma cajennense, foi observado. Em prévio estudo piloto realizado em fevereiro de 2007, em Quirinópolis-GO, a sorologia pela RIFI detectou reagentes em 25% (7/28) dos humanos de um grupo de indivíduos conviventes com um caso suspeito de FM, que foi notificado ao Ministério da Saúde (MS) do Brasil em 2006, e em 0% (0/5) dos cães e 28,6% (12/42) dos eqüinos oriundos de 3 propriedade rurais onde esse caso suspeito esteve antes da manifestação dos sinais de enfermidade. Houve eqüinos sororeagentes em duas dessas três propriedades rurais. Não foi possível rastrear a provável fonte de infecção, mas os achados aqui obtidos permitem suspeitar que o caso suspeito de FM tenha tido em uma dessas duas propriedades rurais a fonte antigênica do provável contato com bactérias do grupo da FM ou microrganismos antigenicamente semelhantes. Já no estudo dimensionado epidemiologicamente para eqüinos, realizado em março de 2007 em 20 propriedades rurais, foi encontrada a prevalência de sororeagentes de 11,6% (39/335) entre os eqüinos e a freqüência de soropositivos de 36,6% (15/41) entre os humanos e de 16,7% (2/12) entre os cães oriundos dessas propriedades de criação de eqüinos. Os humanos soropositivos aqui testados eram assintomáticos para FM no momento da coleta de amostras. Concluiu-se que a FM, ou doença antigenicamente semelhante, possa estar ocorrendo no Estado de Goiás, no Município de Quirinópolis

Para o sucesso das estratégias de manejo de Rhipicephalus (Boophilus) microplus (carrapato bovino) são necessários testes práticos, econômicos e confiáveis que possam detectar a presença de fenótipos resistentes a drogas em suas populações. O fipronil é um acaricida de uso relativamente recente não havendo testes padronizados para o diagnóstico de resistência do carrapato à molécula. No presente trabalho, foram padronizados bioensaios in vitro para esta finalidade: Teste de Imersão de Adultas, Teste de Imersão de Larvas e Teste de Pacote com Larvas. Os testes foram aplicados e, de forma inédita, populações resistentes foram diagnosticadas tanto no Brasil quanto no Uruguai. Ensaios com inibidores enzimáticos não evidenciaram participação importante de enzimas detoxificadoras no mecanismo de resistência. Foi demonstrada reação cruzada entre fipronil e lindano, não verificada para ivermectina. Em algumas situações, foi observado interferência do controle químico de pragas agrícolas no desenvolvimento de resistência dos carrapatos. / For the success of the strategies for the management of Rhipicephalus (Boophilus) microplus (cattle tick), practical, economical and reliable tests are needed to detect the presence of drug-resistant phenotypes in their populations. Fipronil is a relatively new acaricide with no standardized tests for the diagnosis of tick resistance to this molecule. In this study, were standardized in vitro bioassays for this purpose: Adult Immersion Test, Larval Immersion Test and Larval Packet Test. The tests were applied and for the first time, resistant populations were diagnosed in Brazil and Uruguay. Tests with enzymatic inhibitors showed no significant involvement of detoxification enzymes in the mechanism of resistance. Cross-resistance was demonstrated between lindane and fipronil but not with ivermectin. In some situations, it was observed interference of the chemical control of agricultural pests in the development of resistance in ticks.

Os carrapatos são artrópodes hematófagos, vetores de doenças. Vacinas são uma alternativa para o seu controle, já que esses parasitas durante a infestação, estimulam as respostas imunes do hospedeiro, as quais são implicadas em sua rejeição. As glândulas salivares do parasita são importantes para permitir a alimentação e para mediar os mecanismos de escape às defesas do hospedeiro. Diversas evidências indicam que ocorre reatividade cruzada entre espécies de carrapatos e que reações de hipersensibilidade cutânea tardia (DTH) são correlacionadas com resistência ao carrapato. A possibilidade de vacinar cachorros que são parasitados pelo R. sanguineus com antígenos do carrapato do boi, o R microplus, foi investigada por meio da análise in silico de 45 GIs de R microplus clonados em vetor plasmidial (TOPO VR2001), dentre os quais 14 Gls de R microplus se revelaram mais similares a sequências do R sanguineus, e foram empregados para avaliar: 1) A capacidade em elicitar reações cutâneas tardias em cobaias imunes a carrapatos por meio de infestações prévias com R sanguineus. 2) A capacidade de vacinas contendo GIs individuais em afetar infestações de camundongos com adultos de R sanguineus. 3) a capacidade do GI induzir anticorpos específicos após vacinação em camundongos. Dos 14 GIs testados, apenas dois não induziram reações cutâneas, quatro não afetaram nenhum parâmetro parasitológico da infestação, e três não induziram a produção de anticorpos nesses animais. Dentre os GIs, sete foram escolhidos para compor uma vacina multigênica contra o carrapato do cão R sanguineus. A vacina foi capaz de induzir resistência á infestação por R sanguineus em camundongos e em cachorros vacinados evidenciadoa pela diminuição do número de fêmeas que conseguiram colocar ovos, do peso médio da massa de ovos produzidos por essas fêmeas, do índice reprodutivo dessas fêmeas, e da taxa de eclosão das larvas, demonstrando que GIs de R microplus podem ser alvos para formulação de uma vacina contra o carrapato R sanguineus. / Ticks are arthropod vectors of disease. Vaccines are an alternative to chemicals for controlling ticks because during infestations these parasites stimulate host immune responses such as delayed hypersensitivity skin reactions (DTH), which are involved in their rejection and are correlated with resistance to ticks. Tick salivary glands are important for the parasite to acquire blood meals because their products mediate escape mechanisms from host defenses. The possibility of vaccinating dogs against infestations with the brown dog tick, Rhipicephalus sanguineus, with antigens derived from salivary glands of the cattle tick, R. microplus, was investigated by in silica analysis of 45 genes from R. microplus. These genes were targeted because of their putative biological function and had been cloned into the plasmid vector TOPO VR2001. Of them, 14 were chosen to be evaluated in a vaccine because their sequences were the most similar to several genes expressed in salivary glands of R. sanguineus. The plasmids containing the genes of interest (GIs) were used to assess: 1) The ability of the product of the genes to elicit delayed skin reactions in guinea pigs immune to ticks by previous infestations with R sanguineus. 2) The ability of individual GIs delivered as DNA vaccines to affect infestations of mice with adult R sanguineus. 3) The ability of the genes to induce specific antibodies after vaccination in mice. Only two of the 14 genes delivered to guinea pigs via intradermal injection of DNA did not elicit delayed skin reaction, four used in a vaccine did not affect any parameter of tick infestations, and three did not induce production of antibodies in these animals after DNA vaccination. Of the 14 genes, seven were chosen to formulate a multigene vaccine against the dog tick R. sanguineus. The vaccine was able to significantly affect several parameters of infestations by R sanguineus in vaccinated dogs and mice. This was reflected in the reduction of the number of females that were able to lay eggs, of the average weight of the egg mass produced by these females, of the reproductive rate of these females, and of hatching rate of larvae, demonstrating that GIs from R microplus may be targets for development of a vaccine against the tick R sanguineus.

Made available in DSpace on 2014-08-20T14:38:46Z (GMT). No. of bitstreams: 1 dissertacao_patricia_biegelmeyer.pdf: 576535 bytes, checksum: 210ef4efc6311207454f251dd80d5018 (MD5) Previous issue date: 2012-02-29 / The overall aim of this study was to analyze different perspectives of Rhipicephalus (Boophilus) microplus genetic resistance. Therefore, the present study was divided into three manuscripts. Firstly, a literature review was conducted to present some aspects of tick resistance, like results of previous studies of bovine resistance, environmental effects on this triat, and some findings in molecular biology that will help to identify resistant animals. The second trial was conducted to estimate genetic parameters for tick resistance measured by two assessment methods in Hereford and Braford cattle, and genetic correlations between tick resistance and growth of animals. The animals belonging to the Delta G Connection genetic improvement consortium, were raised on nature and artificial pastures in Southern Brazil, and the age at the evaluation period was about 18 months. Data were analyzed from 6,462 bovines naturally exposed to ticks. The number of ticks was counted at inner hind legs region (IHL) of 3,413 animals between 2001 and 2008, and was recorded up to three consecutive counts at one side of body (LAT) in 3,049 bovines between 2009 and 2010, a total of 7,813 records. In addition, the database contained data of 109,566 birth weights (BW), 112,815 records of weight gain from birth to weaning (ADG) and 54,843 data of weight gain from weaning to yearling (PWG). For the analyses, tick count data was transformed using a logarithmic function. Heritability estimates obtained by bivariate analysis were IHL = 0.152 ± 0.043 and LAT = 0.235 ± 0.063 and genetic correlation between both methods was 0.575 ± 0.220. Single-trait analysis of LAT indicated a repeatability of 0.312 ± 0.014. Genetics association analysis between IHL and LAT and the development characteristics evaluated indicated significant associations between IHL and BW (0.220 ± 0.102), and favorable negative correlations between LAT and ADG (-0.211 ± 0.099) and LAT and PWG (-0.650 ± 0.125) (P<0.05). The objective of third trial was to analyze the bovine genetic resistance effect on tick biological traits. The engorged female ticks analyzed were collected from 40 Braford heifers classified as genetically resistant (R) or susceptible (S), according to the breeding values for tick count, calculated based on a database with 9,036 records of Hereford and Braford bovines. After classification, the selected heifers were moved to an experimental area in Embrapa Pecuária Sul, located in the city of Bagé, in the Brazilian state of Rio Grande do Sul, and subjected to four artificial infestations, 14 days apart each one. Weights of engorged female ticks and of female ticks after oviposition did not differ between resistant and susceptible heifers. Female ticks engorged in genetically susceptible heifers showed higher capacity of posture (R = 0.097 ± 0.021g and S = 0.109 ± 0.030g) and higher values of reproductive efficiency index (R = 47.23 ± 5.85% and S = 53.27 ± 3.74%) The overall aim of this study was to analyze different perspectives of Rhipicephalus (Boophilus) microplus genetic resistance. Therefore, the present study was divided into three manuscripts. Firstly, a literature review was conducted to present some aspects of tick resistance, like results of previous studies of bovine resistance, environmental effects on this triat, and some findings in molecular biology that will help to identify resistant animals. The second trial was conducted to estimate genetic parameters for tick resistance measured by two assessment methods in Hereford and Braford cattle, and genetic correlations between tick resistance and growth of animals. The animals belonging to the Delta G Connection genetic improvement consortium, were raised on nature and artificial pastures in Southern Brazil, and the age at the evaluation period was about 18 months. Data were analyzed from 6,462 bovines naturally exposed to ticks. The number of ticks was counted at inner hind legs region (IHL) of 3,413 animals between 2001 and 2008, and was recorded up to three consecutive counts at one side of body (LAT) in 3,049 bovines between 2009 and 2010, a total of 7,813 records. In addition, the database contained data of 109,566 birth weights (BW), 112,815 records of weight gain from birth to weaning (ADG) and 54,843 data of weight gain from weaning to yearling (PWG). For the analyses, tick count data was transformed using a logarithmic function. Heritability estimates obtained by bivariate analysis were IHL = 0.152 ± 0.043 and LAT = 0.235 ± 0.063 and genetic correlation between both methods was 0.575 ± 0.220. Single-trait analysis of LAT indicated a repeatability of 0.312 ± 0.014. Genetics association analysis between IHL and LAT and the development characteristics evaluated indicated significant associations between IHL and BW (0.220 ± 0.102), and favorable negative correlations between LAT and ADG (-0.211 ± 0.099) and LAT and PWG (-0.650 ± 0.125) (P<0.05). The objective of third trial was to analyze the bovine genetic resistance effect on tick biological traits. The engorged female ticks analyzed were collected from 40 Braford heifers classified as genetically resistant (R) or susceptible (S), according to the breeding values for tick count, calculated based on a database with 9,036 records of Hereford and Braford bovines. After classification, the selected heifers were moved to an experimental area in Embrapa Pecuária Sul, located in the city of Bagé, in the Brazilian state of Rio Grande do Sul, and subjected to four artificial infestations, 14 days apart each one. Weights of engorged female ticks and of female ticks after oviposition did not differ between resistant and susceptible heifers. Female ticks engorged in genetically susceptible heifers showed higher capacity of posture (R = 0.097 ± 0.021g and S = 0.109 ± 0.030g) and higher values of reproductive efficiency index (R = 47.23 ± 5.85% and S = 53.27 ± 3.74%) / O objetivo geral do presente estudo foi abordar diferentes perspectivas sobre a resistência genética de bovinos ao carrapato Rhipicephalus (Boophilus) microplus. Para tanto, foi dividido em três trabalhos. Primeiramente, foi realizado um estudo de revisão que abrangeu alguns aspectos relacionados à resistência, como resultados de trabalhos que avaliaram a resistência de bovinos, fatores ambientais capazes de afetar os fenótipos de resistência e algumas descobertas na área da biologia molecular que poderão ser úteis no processo de identificação de animais geneticamente resistentes. O segundo trabalho objetivou estimar parâmetros genéticos para a resistência mensurada por dois métodos de avaliação em bovinos Hereford e Braford, e as correlações genéticas entre a resistência e características de crescimento dos animais. Os bovinos que participaram das avaliações foram provenientes de rebanhos controlados pelo programa de melhoramento da Conexão Delta G, localizados no estado do Rio Grande do Sul e criados a campo sobre pastagens naturais e artificiais. Foram avaliados dados de 6.462 bovinos com idade média de 18 meses, naturalmente infestados, sendo as contagens realizadas na região do entrepernas (ENT) em 3.413 animais entre 2001 e 2008, e 7.813 registros de contagens na lateral do corpo (LAT) de 3.049 bovinos realizadas entre 2009 e 2011. Foram utilizados também 109.566 dados de peso ao nascimento (PN), 112.815 registros de ganho de peso do nascimento à desmama (GPD) e 55.843 dados de ganho da desmama ao sobreano (GDS). Para as análises, os dados de contagens sofreram transformação logarítmica. As estimativas de herdabilidade dos métodos de avaliação obtidas por análise bicaracterística foram ENT = 0,152 ± 0,043 e LAT = 0,235 ± 0,063, e a correlação genética entre ambos foi de 0,575 ± 0,220. A análise unicaráter da LAT apontou uma repetibilidade de 0,312 ± 0,014. As associações genéticas entre a ENT e a LAT e as características de desenvolvimento avaliadas apontaram associações significativas entre ENT e PN (0,220 ± 0,102), e favoráveis correlações negativas e entre LAT e GPD (-0,211 ± 0,099) e LAT e GDS (-0,650 ± 0,125) (P<0,05). O terceiro trabalho objetivou analisar o efeito da resistência dos bovinos sobre características biológicas dos carrapatos. As teleóginas analisadas foram coletadas em 40 novilhas Braford classificadas como geneticamente resistentes (R) ou suscetíveis (S), de acordo com os valores genéticos obtidos para a característica de contagem de carrapatos, calculados com base em um banco de dados com registros de 9.036 animais das raças Hereford e Braford. Após a classificação, as novilhas selecionadas foram encaminhadas à Embrapa Pecuária Sul (Bagé, RS), onde foram submetidas a quatro infestações artificiais, com intervalos de 14 dias. Os pesos médios iniciais das teleóginas e os pesos das quenóginas não diferiram entre os grupos de novilhas resistentes e suscetíveis. Fêmeas ingurgitadas em novilhas geneticamente suscetíveis apresentaram maior capacidade de postura (R = 0,097 ± 0,021g e S = 0,109 ± 0,030g) e maiores índices de eficiência reprodutiva (R = 47,23 ± 5,85% e S = 53,27 ± 3,74%) e nutricional (R = 54,33 ± 4,36% e S = 65,62 ± 8,84%) que teleóginas ingurgitadas em novilhas resistentes.

La connaissance des facteurs qui influent sur les populations de tiques et en particulier sur leurs distributions est un préalable indispensable à l’étude des maladies qu’elles transmettent. Parmi eux, l’importance des facteurs biotiques et en particulier celle de la compétition interspécifique est peu connue et souvent négligée. L’objectif de ce travail était d’évaluer le rôle de la compétition interspécifique sur la distribution de deux espèces de tiques d’importance vétérinaire, Amblyomma variegatum et A. hebraeum. Alors que seule A. variegatum favorise la transmission de la dermatophilose, une maladie de peau débilitante pour les ruminants, les deux espèces sont vectrices de la cowdriose, maladie due à une bactérie Ehrlichia ruminantium qui représente une contrainte économique majeure pour l’élevage. L’impact de l’espèce vectrice dans l’épidémiologie de la cowdriose (différences de souches circulantes, sévérité des cas,…) est inconnu bien qu’ayant potentiellement des conséquences en termes de surveillance (risque épidémiologique à l’introduction d’animaux) et de contrôle (développement de vaccin régional adapté aux souches circulantes) de la maladie. Ces deux espèces ont une distribution contiguë en Afrique australe avec peu de chevauchement (distribution parapatrique) suggérant une préférence environnementale différentielle ou une compétition exclusive entre elles. Une revue des données de la littérature a permis de mettre en évidence un chevauchement de leur niche trophique, climatique, et temporelle, et une interférence comportementale via la production de leurs phéromones. Les deux espèces pourraient donc rentrer en compétition directement par interférence communicative ou reproductive (hybridation stérile), ou indirectement via le partage de ressources, prédateurs ou pathogènes communs. Le rôle des facteurs biotiques et abiotiques sur le maintien de la parapatrie de ces deux espèces a été analysée (i) d’une part par la comparaison de leur niche environnementale réalisée en Afrique australe, et aux deux zones de contact au Zimbabwe et Mozambique, par des méthodes d’ordination et de modèles de niche (Maxent) ; (ii) et d’autre part par l’étude de leurs distributions et de leurs interactions (distribution sur les hôtes, croisements hétérospécifiques) dans la zone de contact au Mozambique. Globalement les résultats montrent qu’en Afrique Sud-Est et au Zimbabwe les deux espèces occupent des niches environnementales distinctes, celle d’A. hebraeum incluant des zones plus chaudes et plus sèches que celle d’A. variegatum. Au contraire au Mozambique les deux niches se chevauchent considérablement. L’enquête de terrain dans cette zone montre que les deux espèces y sont moins souvent trouvées en sympatrie que les données prédites, suggérant une distribution en partie déterminée par des interactions biotiques. Dans les rares sites avec présence des deux espèces, A. variegatum et A. hebraeum partagent les mêmes sites de fixation sur les animaux et forment un pourcentage relativement élevé de couples hétérospécifiques. Ce pourcentage, bien que similaire entre les femelles A. variegatum et A. hebraeum, semble impliquer des processus de discrimination spécifique propres aux deux espèces intervenant au niveau de l’agrégation, de la fixation et du contact des individus. Nos résultats suggèrent l’existence d’une compétition exclusive entre les deux espèces, due à une compétition sexuelle probablement associée à une compétition indirecte. La frontière parapatrique semble occuper une position stable le long d’un gradient environnemental au Zimbabwe mais pas au Mozambique. Les conditions entrainant la coexistence ou l’exclusion des deux espèces avec formation d’une frontière parapatrique sont discutés à l’aide de modèles théoriques de compétition. / Studying the factors that influence tick populations and their distributions is an essential pre-requisite to understanding the dynamics of the diseases they transmit. The relative importance of biotic factors such as interspecific competition is not well known and often neglected. The objective of this study was to assess the influence of interspecific competition on the distribution of two tick species of veterinary importance, Amblyomma variegatum and A. hebraeum. Whereas only A. variegatum is known to favor dermatophilosis, a debilitating skin disease of ruminants, both species are good vectors of Ehrlichia ruminantium, the bacteria causing heartwater, a fatal disease of ruminants that presents a major constraint for livestock development in Africa. The impact of vector species in heartwater epidemiology (differences of circulating strains, severity of clinical cases…) is poorly known but may have important implications for surveillance (epidemiological risk of imported animals) and control (adapting regional vaccine programs to circulating strains) of the disease. These two ticks have abutting and marginally overlapping (i.e. parapatric) distributions in southern Africa, suggesting either differential environmental preferences or exclusive competition between the two species. A review of published data highlighted an important overlap of their trophic, climatic and seasonal niche, and existence of chemical behavior interference through pheromone production. Therefore, the two species might compete either directly by communicative or reproductive interference (sterile hybridization), or indirectly by sharing the same resources, predators or pathogens. The role of biotic and abiotic factors in determining parapatry of these species was assessed by (i) comparing their realized environmental niche in southern Africa, and at contact zones in Zimbabwe and Mozambique, using ordination techniques and environmental niche modeling (Maxent); (ii) studying their distributions and their interactions (distribution on co-infested host, heterospecific mating) at the contact zone in Mozambique. Globally, the results indicated the two species occupied distinctly different environmental niches in southern Africa and at the contact zone in Zimbabwe, with the niche of A. hebraeum including both hotter and drier areas than that of A. variegatum. However, in Mozambique their niches overlapped considerably. Field studies within this zone showed that sympatry was observed less frequently than predicted by niche models, suggesting an importance of biotic interactions. At the rare sites where both species were present, A. variegatum and A. hebraeum were observed to share the same preference sites on hosts and formed a high percentage of heterospecific pairs. Though this cross-mating rate was not significantly different between A. variegatum and A. hebraeum females, our observations suggest different mechanism of species discrimination involved for the two species acting at the aggregation, fixation and partner contact level. Our results strongly suggest exclusive competition between these species may arise from sexual competition probably interacting with other indirect forms of competition. The parapatric boundary apparently occupies a stable location along an environmental gradient at the contact zone in Zimbabwe but not in Mozambique. Conditions inducing coexistence or exclusion of both species with the formation of parapatric distributions are discussed in relation to theoretical models of competition. When sexual competition is introduced in these models, the relative frequency of two species is determined by their endogenous fitness (a function of environmental conditions), density dependent effects of competitive interactions, historical distributions and dispersal rates: survival of the first prevails when the immigration rate of a fitter invading species remains lower than an invasion threshold.

An intensive study was conducted on the free-living larvae and parasitic life stages of R.glabroscutatum on Angora and Boer goats in the Uitenhage district. Free-living larvae exhibited periods of maximum relative abundance during months of generally lower rainfall, from the end of autumn to the beginning of spring. Relative larval abundance in open and gully sites was low while larvae were rarely found in bush sites. Relative abundance was higher at 20h00 than at 08h00 and 14h00. Repeated sampling in the same areas did not reduce larval numbers. Over 99% of parasitic ticks removed from Angora and Boer goats were located on the feet. The annual occurrence of a low and variable number of parasitic immatures was synchronous with the occurrence of free-living larvae. High, less variable numbers of adult ticks were removed from goat feet from September to December, the highest numbers being recorded during October and November. The occurrence of a single period of parasitic adult abundance annually indicated a life cycle with 1 generation per anum. There were higher numbers of adult ticks on the feet of the Angora goats than on the Boer goats. Adult numbers were higher on the hind feet of both breeds of goats than on the front feet. R.glabroscutatum adults seem to be implicated in the aetiology of foot abscesses since more infections were observed in Angora goats than in Boer goats and on the hind feet rather than the front feet within both goat groups. In addition R.glabroscutatum adults attached at interdigital sites where abscesses also originated and reached highest numbers in October and November when abscesses were most frequently observed. A review of distribution and host records indicated that R.glabroscutatum was limited in its distribution to the eastern Cape Province, being primarily located in South Africa's major mohair producing areas. R.glabroscutatum was classed an obligative xerophile on the basis of its recorded occurrence in non coastal areas with a low annual rainfall and Karoo and Karroid Bush vegetation. Host records for R.glabroscutatum included 10 species of wild ungulate, sheep, goats and cattle. The common site of occurrence on small stock and on small to medium sized wild animals appeared to be the legs and feet.

Les maladies infectieuses sont une des causes les plus importantes de morbidité chez l'homme et l'animal avec des conséquences à la fois économiques, sanitaires et écologiques. L'étude de la diversité des pathogènes responsables et de leurs dynamiques de circulation au sein des communautés d'hôtes et de vecteurs, peut fournir des informations importantes pour la prévention et le contrôle de ces maladies. Dans ce contexte, nous nous sommes intéressés à l'agent pathogène responsable de la maladie de Lyme. Cette maladie est causée par les bactéries du complexe d'espèces Borrelia burgdorferi sensu lato (s.l.) transmises par les tiques lors de repas sanguins et sont capables d'infecter plusieurs espèces d'hôtes vertébrés. L'analyse de la diversité génétique de 63 souches de B. burgdorferi s.l., dont les génomes ont été séquencés, ont révélé un degré d'isolement génétique très important entre les différentes espèces du complexe. Les résultats obtenus suggèrent que les différents spectres d'hôtes des lignées de B. burgdorferi s.s. (principalement associées aux petits mammifères) et de B. garinii (normalement associées aux oiseaux) conduisent à des dynamiques de populations distinctes. De plus, grâce au séquençage haut-débit de deux marqueurs, nous avons pu démontrer qu'il existe, à une échelle intra-spécifique, des associations préférentielles des génotypes de B. burgdorferi avec différentes espèces de rongeurs. Enfin, en utilisant la diversité observée chez ces rongeurs et celle chez les tiques, nous avons estimé, via une approche de modélisation, que la contribution au risque de la maladie pour l'homme d'une espèce hôte introduite (tamia de Sibérie), pouvait être importante. / Infectious diseases are one of the major causes of human and animal morbidity, and they have impacts on the economy, public health, and the environment. By studying the diversity of the pathogens responsible for these diseases and their circulation within host communities and among vectors, we may glean valuable information that will aid prevention and control efforts. For these reasons, during my thesis, I became particularly interested in the pathogen(s) responsible for Lyme disease. This disease is caused by bacteria belonging to the Borrelia burgdorferi sensu lato (s.l.) species complex that are transmitted by ticks (during their blood meals) and that can infect several vertebrate host species. When I analyzed the genetic diversity present in 63 B. burgdorferi s.l. strains, whose genomes had been sequenced, I found that there was a significant degree of genetic separation among the different genospecies making up the complex. My results suggest that the fact that these different bacterial groups infect different ranges of hosts B. burgdorferi s.s. is mainly a pathogen of small mammals and B. garinii is primarily associated with birds lead to distinct population dynamics. Moreover, thanks to the high-throughput sequencing of two genetic markers, I have been able to show that, at an intraspecific level, certain B. burgdorferi genotypes are associated with specific rodent species. Finally, using the pathogen diversity observed in rodents and ticks, I employed a modeling approach to estimate the human disease risks presented by an introduced host species (the Siberian chipmunk) and found that these risks could be significant.

A. phagocytophilum, une bactérie transmise par les tiques, est responsable de l’anaplasmose granulocytaire, une maladie émergente qui infecte une large gamme de mammifères dont l’homme. Actuellement, la description des cycles épidémiologiques de cette bactérie est incomplète. L’objectif de cette thèse est de caractériser la diversité génétique d’A. phagocytophilum chez différentes espèces d’hôtes, afin de déterminer quelles espèces participent au même cycle épidémiologique. D’abord, nous avons caractérisé la diversité génétique d’A. phagocytophilum chez les animaux domestiques malades à l’aide d’une MLSA. Nous avons identifié trois groupes de génotypes infectant les bovins, dont un groupe est partagé avec les chevaux et les chiens, et un avec les chevreuils. Ensuite, nous avons recherché quelles espèces de tiques pouvaient transmettre la bactérie, et quels pouvaient être les réservoirs parmi les mammifères sauvages. En Camargue, un génotype au fort potentiel zoonotique a été identifié chez cinq espèces de tiques du genre Rhipicephalus, Dermacentor et Hyalomma. La prévalence chez des rongeurs suggère qu’ils peuvent être réservoirs, mais la présence de génotypes infectant les bovins chez les mulots est à vérifier. Enfin, la comparaison des génotypes obtenus chez les tiques et les chevreuils par séquençage 454, a montré que la contribution des chevreuils à l’infection des tiques était faible sur le site des Vallons de Gascogne. L’absence de rongeurs infectés sur ce site suggère que d’autres mammifères réservoirs sont présents. Cette étude montre la complexité des cycles d’A. phagocytophilum et l’intérêt des outils moléculaires. / A. phagocytophilum, a tick-borne bacterium, is responsible of the granulocytic anaplasmosis, an emerging disease that infects a large range of mammals including humans. Currently, the description of the epidemiological cycles of this bacterium is incomplete. The objective of this thesis was to characterize the genetic diversity of A. phagocytophilum in different host species to determine those involved in the same epidemiological cycle. First, we characterized the genetic diversity of A. phagocytophilum in sick domestic animals with a MLSA. We identified three groups of genotypes infecting cattle, including one group shared with horses and dogs, and another shared with roe deer. Then, we investigated what species of ticks can transmit the bacteria, and what wild mammals could be reservoirs. In Camargue, a genotype with high zoonotic potential was identified in five species of ticks of the genus Rhipicephalus, Dermacentor and Hyalomma. The prevalence in French rodents suggests that they may be reservoir hosts, but the presence of genotypes infecting cattle in rodents must be checked. Finally, comparing the bacterial genotypes in ticks and roe deer by 454 sequencing, showed that the contribution of the roe deer to tick infection was low in the site of “Vallons de Gascogne”. The absence of infected rodents in this location suggests that other reservoir mammals are present. This study demonstrates the complexity of the A. phagocytophilum cycle and the contribution of molecular tools.