Haja vista a existência de quatro famílias de M. avium molecularmente distintas circulando na população de suínos do Sul do Brasil, a diferença de virulência constatada entre essas quatro famílias, a influência da virulência nos mecanismos de transmissão, as dúvidas existentes a respeito da existência e da importância da transmissão horizontal de M. avium em suínos e do significado desse conhecimento para o estabelecimento de métodos de controle eficientes, o presente projeto tem por objetivos: 1) Padronizar método de isolamento de micobactérias a partir de fezes suínas; 2) Caracterizar a eliminação de M.avium pelas fezes em suínos experimentalmente infectados pela via oral; 3) Verificar se existe transmissão horizontal entre suínos durante a fase de eliminação ativa, através de experimentos envolvendo infecção oral e exposição de animais contactantes; 4) Estudar, através de modelagem matemática, a dinâmica da infecção por M.avium em uma população suína. Como resultados, para cada um dos itens obteve-se: 1) Houve diferença significativa entre os protocolos de recuperação de micobactérias a partir de fezes de suínos (p< 0,05) e o método ácido com ressuspensão em solução de anfotericina B e semeadura em meio de Lowenstein-Jensen com antibióticos apresentou o maior percentual de recuperação (87%); 2) Foram constados dois períodos de eliminação fecal de MAC em suínos: um inicial, relativo à eliminação residual do inóculo, do 1º ao 4º, e um segundo, com início no 18º e término no 62º dias pós-inoculação, este último é resultado de suposta lesão aberta para a luz do intestino; 3) Cinco, dos sete animais contactantes, infectaram-se com o M.avium, estirpe PIG B e 4) A simulação matemática da doença, considerando a transmissão horizontal como mecanismo principal da ocorrência de condenações em matadouro por linfadenite granulomatosa é inconsistente com o que se observa na população. Portanto, o componente ambiental tem papel preponderante na dinâmica das infecções micobacterianas dos suínos produzidos no Brasil. / Considering four genetic distinct M. avium families within the swine population of the Southern Brazil, the virulence difference detected among them, the virulence influence on the transmission mechanisms, the current doubts concerning M. avium horizontal transmission existence and importance in swine and about its knowledge meaning in order to stablish efficient control programs, the objectives of the present study were: 1) to set in a standard mycobacterial isolation method from swine feces; 2) to characterize M. avium excretion through feces in swine infected orally; 3) to verify the existence of horizontal transmission among swine during the active elimination phase, by experiments involving oral infection and exposure of contacting animals; 4) to study, through mathematical modelling, M. avium infection dynamics in a swine population. These are the attained results for each of the items: 1) there was a significant difference (p<0.05) between the mycobacterial recovery protocols from swine feces and the acid method with suspension in amphotericin solution and inoculation in Lowenstein-Jensen media with antibiotics presented the greatest recovery percentage (87%); 2) two fecal elimination periods of M. avium in swine feces were observed: an initial one, relative to the residual elimination of the inoculum, within days 1 and 4, and a second one, starting at day 18 and ending at day 62 post inoculation - the last one results from a supposed lesion opened to the intestinal lumen. 3) Five out of seven contacting animals were infected with M. avium; 4) The mathematical simulation of the disease, considering the horizontal transmission as the major mechanism of occurrence of condemnation at slaughterhouses due to granulomatous lymphadenitis is not consistent with what is observed in the population. Therefore, the environmental component plays a preponderant role in the mycobacterial infections dynamics of swine raised in Brazil.

Wolbachia é uma alfaproteobactéria que apresenta simbiose com uma variedade de artrópodos e nematoides, estando entre os mais abundantes gêneros de bactérias intracelulares já descobertos. Na região Neotropical, os estudos sobre tais bactérias e seus hospedeiros, em especial isópodos terrestres, ainda são incipientes. O presente trabalho teve como objetivos: investigar as espécies de isópodos terrestres neotropicais infectados por Wolbachia; analisar a prevalência de infecção, variação genética e relações filogenéticas das linhagens presentes nessas espécies; investigar a simbiose de Wolbachia em nematoides parasitos de tatuzinhos-de-jardim e inferir sobre as possíveis rotas de transmissão horizontal da bactéria entre os isópodos terrestres e os invertebrados que possuam associações ecológicas com os mesmos. A detecção da bactéria foi realizada através de PCRs diagnósticas, utilizando-se o gene 16S rDNA. A infecção pelo simbionte foi registrada pela primeira vez em Atlantoscia floridana e Burmoniscus meeusei. As linhagens de Wolbachia que infectam as espécies nativas de isópodos terrestres, ao contrário das introduzidas, são muito diversas e não se agrupam dentro do Oniclado. Já as sequências presentes em B. meeusei não são relacionadas a nenhuma outra linhagem presente em crustáceos, e nem mesmo fazem parte de qualquer supergrupo conhecido de Wolbachia. Pela primeira vez foi evidenciada a presença da bactéria em um nematoide da família Mermithidae, Agamermis sp., endoparasito do tatu-bola Armadillidium vulgare. Uma vez que as sequências do parasito e do hospedeiro são idênticas, é possível que um evento de transmissão horizontal tenha ocorrido entre ambos. Por fim, a presença de Wolbachia foi examinada em espécies que possuiam relações ecológicas com os isópodos terrestres (predadores, parasitos, foréticos e animais que vivem sob as mesmas condições ecológicas). Entre as espécies associadas, a infecção foi registrada apenas no nematoide parasito e nos ácaros foréticos. Enquanto as linhagens do isópodo hospedeiro e do nematoide se mostraram muito similares, àquelas dos ácaros foréticos não apresentaram relação filogenética com as de seus forontes Balloniscus glaber. Interessantemente, as sequências presentes nos ácaros são proximamente relacionadas com aquelas de B. meeusei, embora mais estudos sejam necessários para esclarecer tal achado. / Wolbachia is a genus of alfaproteobacteria whose members live in symbiosis with a variety of arthropods and nematodes. It is among the richest genera of intracellular bacteria discovered to date. In the Neotropical region, studies on these bacteria and their hosts, especially terrestrial isopods, are still in the initial stages. The objectives of the present study were: to investigate the species of Neotropical terrestrial isopods infected by Wolbachia; to analyze the prevalence of infection, genetic variation, and phylogenetic relationships of the lineages present in these isopod species; to investigate the symbiosis of Wolbachia in parasitic nematodes of pillbugs; and to provide information to support inferences about the possible routes of horizontal transmission of the bacteria between the terrestrial isopods and the invertebrates that are ecologically associated with them. The bacteria were detected by means of diagnostic PCR’s, using the 16S rDNA gene. Infection by this symbiont was recorded for the first time in Atlantoscia floridana and Burmoniscus meeusei. The lineages of Wolbachia that infect the native species of terrestrial isopods, in contrast to the introduced species, are very diverse and do not group within the Oniclade. The sequences present in B. meeusei are not related to any other lineage present in crustaceans, nor to any other known supergroup of Wolbachia. This study is the first to demonstrate the presence of these bacteria in a nematode of the family Mermithidae, Agamermis sp., an endoparasite of Armadillidium vulgare. Since the sequences from the parasite and the host are identical, it is possible that a horizontal transmission event occurred between the two. Finally, the presence of Wolbachia was examined in species that are ecologically associated with terrestrial isopods (predators, parasites, phoretic species, and animals that live under the same ecological conditions). Among the associated species, the infection was recorded only in the parasitic nematode and in the phoretic mites. Whereas the lineages of the isopod host and of the nematode proved to be very similar, those of the phoretic mites showed no phylogenetic relationship with those of their phoront Balloniscus glaber. Interestingly, the sequences present in the mites are closely related to those of B. meeusei, although further studies are necessary to clarify this finding.

A salmonelose é uma das mais importantes causas de toxinfecção alimentar em humanos, provocando sérios problemas à saúde pública, além de ser uma das doenças de maior impacto na produção avícola. Em vista disso, este estudo objetivou avaliar o uso de ácido fórmico no controle de Salmonella Enteritidis (SE). Assim, foram utilizados 360 pintinhos de um dia de idade: 50% das aves foram inoculadas via inglúvio com 3x107 UFC/0,1mL de SE e 50% não (aves contactantes). As aves foram divididas em cinco (05) grupos com seis (06) repetições cada: T1) controle sem o aditivo; T2) ácido fórmico 0,3% na ração; T3) ácido fórmico 0,2% na ração; T4) ácido fórmico diluído em água de beber até que a mesma atingisse um pH 4; T5) ácido fórmico 0,2% protegido na ração. As aves receberam ácido do 1º ao 7º dia e do 35º ao 42º dia. A cada sete dias, amostras de fezes foram colhidas da cama em todos os grupos para se avaliar o isolamento de SE. Aos 42 dias foram colhidas à necropsia amostras de inglúvio, fígado/baço e ceco para o isolamento de SE e sangue para a avaliação sorológica. Nas aves do T1, do T2 e do T5 SE foi isolada do inglúvio, fígado/baço e ceco das aves inoculadas e das contactantes. Houve isolamento de SE no T3 apenas em inglúvio e ceco das aves inoculadas e, no T4, apenas do ceco das contactantes. Em todos os grupos SE foi reisolada do material da cama, embora não em todas as semanas. A avaliação sorológica realizada com teste comercial de ELISA revelou aves sororeagentes no T1 (inoculadas e contactantes), no T2 (inoculadas) e no T3 (contactantes). Nenhuma ave foi sororeagente no T4 e T5. A transmissão horizontal foi evidenciada em todos os grupos estudados. Os dados foram comprovados por ANOVA e teste LCD. Nos grupos T3 e T4 o ácido fórmico foi eficaz em reduzir a presença e a transmissão horizontal de SE. / Salmonellosis is one of the most common and widely distributed foodborne diseases, with tens of millions of human cases occurring worldwide every year. Furthermore, this disease is responsible to significant economic losses to the poultry industry. Endemic infection of broiler chickens with Salmonella. Enteritidis (SE) and consequential human illness has been well documented. For these reasons the aim of this study was to evaluate the use of formic acid to control SE in broilers experimentally infected. Thus 360 day-old chicks were used in the experiment: 50% (180) of birds were inoculated in crop with 3x107CFU/0.1 mL of SE and 50% (180) were used as controls and kept in contact with the infected chicks. For the formic acid treatment the birds were divided into five (05) groups with six (06) replicates as follows: T1) control without additive; T2) 0.3% formic acid in the diet ; T3) 0.2% formic acid in the diet ; T4) formic acid diluted in drinking until it reached pH 4 water; T5) 0.2% formic acid microencapsulated in the food. The birds received the formic acid from the 1st to 7th day and from the 35th to 42nd days. Every seven days faeces samples were collected from the chick\'s litter and SE isolation was attempted. In the 42 day blood samples were collected for serological evaluation by means of Elisa. Additionally samples from the crop, liver/spleen and cecum were collected at necropsy and submitted to culture for SE detection. SE was isolated from crop, liver/spleen and cecum of the inoculated and contacts birds belonging to the T1, T2 and T5. Regarding the T3, SE was isolated in the crop and cecum of the inoculated birds and in the T4 only in the contacts chicks cecum. In all groups SE was isolated from the litter, although not in every week. Serological evaluation revealed serum positive birds in T1 (inoculated and contacts), T2 (inoculated) and T3 (contacts). Antibodies anti-SE were not detected in the serum from the birds of T4 and T5. Horizontal transmission was observed in all groups. The data were confirmed by ANOVA and LCD test. In groups T3 and T4 formic acid was effective in reducing the presence and horizontal transmission of SE.

A salmonelose é uma das mais importantes causas de toxinfecção alimentar em humanos, provocando sérios problemas à saúde pública, além de ser uma das doenças de maior impacto na produção avícola. Em vista disso, este estudo objetivou avaliar o uso de ácido fórmico no controle de Salmonella Enteritidis (SE). Assim, foram utilizados 360 pintinhos de um dia de idade: 50% das aves foram inoculadas via inglúvio com 3x107 UFC/0,1mL de SE e 50% não (aves contactantes). As aves foram divididas em cinco (05) grupos com seis (06) repetições cada: T1) controle sem o aditivo; T2) ácido fórmico 0,3% na ração; T3) ácido fórmico 0,2% na ração; T4) ácido fórmico diluído em água de beber até que a mesma atingisse um pH 4; T5) ácido fórmico 0,2% protegido na ração. As aves receberam ácido do 1º ao 7º dia e do 35º ao 42º dia. A cada sete dias, amostras de fezes foram colhidas da cama em todos os grupos para se avaliar o isolamento de SE. Aos 42 dias foram colhidas à necropsia amostras de inglúvio, fígado/baço e ceco para o isolamento de SE e sangue para a avaliação sorológica. Nas aves do T1, do T2 e do T5 SE foi isolada do inglúvio, fígado/baço e ceco das aves inoculadas e das contactantes. Houve isolamento de SE no T3 apenas em inglúvio e ceco das aves inoculadas e, no T4, apenas do ceco das contactantes. Em todos os grupos SE foi reisolada do material da cama, embora não em todas as semanas. A avaliação sorológica realizada com teste comercial de ELISA revelou aves sororeagentes no T1 (inoculadas e contactantes), no T2 (inoculadas) e no T3 (contactantes). Nenhuma ave foi sororeagente no T4 e T5. A transmissão horizontal foi evidenciada em todos os grupos estudados. Os dados foram comprovados por ANOVA e teste LCD. Nos grupos T3 e T4 o ácido fórmico foi eficaz em reduzir a presença e a transmissão horizontal de SE. / Salmonellosis is one of the most common and widely distributed foodborne diseases, with tens of millions of human cases occurring worldwide every year. Furthermore, this disease is responsible to significant economic losses to the poultry industry. Endemic infection of broiler chickens with Salmonella. Enteritidis (SE) and consequential human illness has been well documented. For these reasons the aim of this study was to evaluate the use of formic acid to control SE in broilers experimentally infected. Thus 360 day-old chicks were used in the experiment: 50% (180) of birds were inoculated in crop with 3x107CFU/0.1 mL of SE and 50% (180) were used as controls and kept in contact with the infected chicks. For the formic acid treatment the birds were divided into five (05) groups with six (06) replicates as follows: T1) control without additive; T2) 0.3% formic acid in the diet ; T3) 0.2% formic acid in the diet ; T4) formic acid diluted in drinking until it reached pH 4 water; T5) 0.2% formic acid microencapsulated in the food. The birds received the formic acid from the 1st to 7th day and from the 35th to 42nd days. Every seven days faeces samples were collected from the chick\'s litter and SE isolation was attempted. In the 42 day blood samples were collected for serological evaluation by means of Elisa. Additionally samples from the crop, liver/spleen and cecum were collected at necropsy and submitted to culture for SE detection. SE was isolated from crop, liver/spleen and cecum of the inoculated and contacts birds belonging to the T1, T2 and T5. Regarding the T3, SE was isolated in the crop and cecum of the inoculated birds and in the T4 only in the contacts chicks cecum. In all groups SE was isolated from the litter, although not in every week. Serological evaluation revealed serum positive birds in T1 (inoculated and contacts), T2 (inoculated) and T3 (contacts). Antibodies anti-SE were not detected in the serum from the birds of T4 and T5. Horizontal transmission was observed in all groups. The data were confirmed by ANOVA and LCD test. In groups T3 and T4 formic acid was effective in reducing the presence and horizontal transmission of SE.

Made available in DSpace on 2014-08-20T14:37:54Z (GMT). No. of bitstreams: 1 tese_nilton_azevedo_da_cunha_filho.pdf: 1341797 bytes, checksum: 3a24f48f5e86bbb452bd241d5e458c34 (MD5) Previous issue date: 2013-07-08 / Neospora caninum is causing great economic losses in cattle, due to abortion. It has been shown that the transmission of N. caninum is the primary route of infection in cattle, followed by horizontal transmission. Few studies demonstrate the outcome of this type of transmission in herd raised in pasture cattle. The first experiment aimed to evaluate the occurrence of vertical transmission of N. caninum in beef cattle and verify the relationship between seropositivity and abortion. Blood was collected from mothers in the pre-pregnancy and after, three more times in the gestation period, plus a sampling of calves at birth. The seroprevalence in the arrays found in the screening was 32.2% (29/90). The vertical transmission rate was 75.8% and all dams evaluated completed pregnancy, demonstrating that N. caninum is present on the property studied, with high transmission rates, but no apparent influence on the reproductive performance of dams. The second experiment aimed to demonstrate the importance of horizontal transmission in maintaining N. caninum in the same herd. Were accompanied by serological tests, 61 seronegative mothers during pregnancy thirds and their calves at birth (n = 61) and during the first year of life (n = 24). No seroconversion occurred in any of the dams. In calves, however, that seroconversion occurred, indicative of horizontal infection by N. caninum, 12.5% at the end of 12 months. This indicates that horizontal transmission interference occurred in this herd. The third experiment aimed to detect the presence of DNA of N. caninum in umbilical cord of calves positive of positive dams. Was collected the umbilical cord of 20 calves at birth for laboratory testing by PCR. The DNA of the parasite was confirmed by 1/20 (5.0%) umbilical cords. This is the first report of the detection of DNA from N. caninum in umbilical cord of calves by PCR. / Neospora caninum é causador de grandes perdas econômicas na bovinocultura, devidas ao aborto. Já foi demonstrado que a transmissão vertical de N. caninum é a principal rota de infecção entre bovinos, seguida pela transmissão horizontal. Poucos estudos demonstram qual o resultado desse tipo de transmissão em rebanho criado a campo. O experimento 1 teve o objetivo de avaliar a ocorrência de transmissão vertical de N. caninum em matrizes de criação extensiva de gado de corte e verificar a relação entre soropositividade e aborto. Foi coletado sangue das matrizes no período pré-gestacional e, após, em mais três momentos do período gestacional, além de uma coleta de seus bezerros ao nascer. A soroprevalência nas matrizes, constatada na triagem foi de 32,2% (29/90). O índice de transmissão vertical foi de 75,8% e todas as matrizes avaliadas levaram a gestação a termo, demonstrando que N. caninum está presente na propriedade estudada, com índices elevados de transmissão vertical, porém sem influência aparente no desempenho reprodutivo das matrizes. O experimento 2 objetivou demonstrar a importância da transmissão horizontal na manutenção de N. caninum nesse mesmo rebanho. Foram acompanhadas, através de exames sorológicos, 61 matrizes soronegativas durante os terços gestacionais e seus bezerros ao nascer (n=61) e durante o primeiro ano de vida (n=24). Não ocorreu soroconversão em nenhuma das matrizes. Nos bezerros, no entanto, ocorreu essa soroconversão, indicativa de infecção horizontal por N. caninum, em 12,5%, ao final dos 12 meses. Isso indica a interferência da transmissão horizontal nesse rebanho. O experimento 3 teve o objetivo de detectar a presença do DNA de N. caninum em cordão umbilical de bezerros soropositivos filhos de matrizes soropositivas. Coletou-se o cordão umbilical de 20 bezerros no momento do nascimento para os testes laboratoriais pela técnica de PCR. O DNA do parasito foi confirmado em 1/20 (5,0%) dos cordões umbilicais. Este é o primeiro relato da detecção de DNA de N. caninum em cordão umbilical de bezerros pela técnica de PCR.

La lutte microbiologique connaît un regain d'intérêt suite aux problématiques soulevée spar les pesticides chimiques en agriculture. L'objectif de ces travaux de thèse est d'étudier le potentiel d'une ressource virale alternative, les Densovirus pathogènes de Lépidoptères,appartenant à la sous famille des Densovirinae, strictement inféodée aux Arthropodes. Nos travaux ont été axés sur trois points (i) décrire le spectre d'hôtes de deux Densovirus candidats et identifier des déterminants de spécificité pour comprendre l'évolution du spectre d'hôtes ; (ii) caractériser des mécanismes de transmission horizontale pour analyser la dynamique de l'infection et (iii) valider des outils de détection des Densovirinae afin d'étudier la diversité génétique virale dans la nature. Le premier axe nous a permis d'identifier (i) un Densovirus candidat qui ne semble être virulent que pour des Lépidoptères ravageurs de culture, et (ii) des déterminants de spécificité à la surface de la capside impliqués le franchissement de la barrière intestinale. Concernant la transmission, nos résultats montrent qu'un Densovirus se propage rapidement dans une population hôte en induisant un comportement cannibale probablement développé par les individus non infectés. Nous avons également caractérisé deux mécanismes de transmission horizontale,par morsures et par un vecteur endoparasitoïde. Enfin, pour étudier la prévalence virale,nous avons mis au point un protocole basé sur le principe d'une PCR nichée que nous avons testé sur des insectes collectés dans la nature. Ceci nous a permis de dresser un inventaire de la diversité d'insectes, sans toutefois révéler à ce jour la présence de Densovirinae. Ces résultats constituent les premières connaissances pour l'élaboration d'un modèle épidémiologique qui nous permettra d'évaluer l'impact sur l'environnement d'utiliser un Densovirus en tant qu'agent de lutte microbiologique. / Microbial control has a renewed interest due to issues raised by chemical pesticides inagriculture. The aim of this work is to propose a new viral resource, Densoviruses pathogenicfor Lepidoptera belonging to Densovirinae sub‐family restricted to arthropods. We focus onthree axes, (i) we described the host range of two Densovirus candidates, and identified hostspecificity determinants to understand host range evolution; (ii) we characterized themechanisms driving the horizontal transmission of Densovirus to model the dynamic of theinfection; and (iii) we validated tools to detect Densovirinae to study the viral geneticdiversity in natura. The first point lead us to identify (i) a Densovirus potentially pathogeniconly for lepidopteran pests, and (ii) few determinants of specificity localized at the surface ofthe capsid that are essential for the midgut recognition, although this barrier of specificity isnot the only one. Concerning horizontal transmission, our results show that a Densovirus canspread rapidly within a host population, inducing a cannibalistic behavior probablydeveloped by non infected individuals. We also characterize two mechanisms involved intransmission, by biting and by an endoparasitoïd vector. To study the densoviral prevalence,we develop a nested PCR and test it on insect sampling. This allowed us to describe theinsect diversity. No Densovirinae have been detected so far. These results are the first steptoward building an epidemiology model that may allow to evaluate the impact of using aDensovirus as a biological control tool.

This thesis studies the inter-group variation of the consonant endings among five principal subgroups of the Chaoshan dialect, a branch of the South Min dialect in Eastern Guangdong Province, from the perspective of language contact and horizontal transmission. I conduct a quantitative study to present the synchronic variance of the consonant endings among five Chaoshan subgroups and the diachronic variance from Middle Chinese to modern Chaoshan dialect on a numerical scale. The current literature tends to take the change of the consonant endings as a process of weakening governed by regular rules. My research findings challenge this conventional view. First, the change of the consonant endings from Middle Chinese to five subgroups of modern Chaoshan dialect is irregular, which is an exception to the linguistic laws proposed in the existing literature. Secondly, I find that some characters without consonant endings or with a weakened ending in Chaozhou in the 19th century reverse to have a consonant ending in modern Chaoshan dialect. This reversal contradicts to the weakening hypothesis that regards the change of the consonant endings as a process of simplifying. Finally, my quantitative research shows that Chaozhou dialect in the 19th century in much closer to modern Xiamen dialect than to five subgroups of modern Chaoshan dialect in terms of the relativeness in consonant endings, which is the opposite to the prediction that languages become more and more different and have no consequent contact with other daughter languages after separating from the proto-language. We propose that the actual situation of the consonant endings in different subgroups of the Chaoshan dialect can be better explained from the perspective of language contact and horizontal transmission. The interaction between Han Chinese and non-Han Chinese is the primary reason for the change of the consonant endings of the Chaoshan dialect. Also, the language contact between Chaoshan aborigines and migrants from the Fujian Province leads to the divergence of the consonant endings in different Chaoshan subgroups.Population structure and other social factors determine what phonetic features survive after several times of horizontal transmission.

The gammaproteobacterium Arsenophonus nasoniae infects Nasonia vitripennis (Hymenoptera: Pteromalidae), a parasitic wasp that attacks filth flies. This bacterium kills virtually all male offspring of infected females. Female wasps transmit A. nasoniae both vertically (from mother to offspring) and horizontally (to unrelated Nasonia developing in the same fly). This latter mode may enable the bacterium to colonize novel species and spread throughout a filth fly-parasitoid guild. This spread may be important for maintenance of the bacterium. The ecology of novel hosts may be significantly impacted by infection. The actual and potential host range of A. nasoniae was assessed. I used Arsenophonus-specific primers to screen a large sample of filth flies and their parasitoids. The bacterium infects a wide range of wasp species in the environment. The potential host range was determined by inoculating three wasp and one fly species with an isolate of A. nasoniae from Lethbridge, AB. The bacterium successfully infected all insects and was transmitted by two wasp species. It reduced host longevity, but did not kill males, in Trichomalopsis sarcophagae. It also caused pupal mortality in Musca domestica.

Em cana-de-açúcar, a colonização do caule por fungos oportunistas, como Fusarium verticillioides e Colletotrichum falcatum, está diretamente ligada ao ataque da lagarta Diatraea saccharalis (Lepidoptera: Crambidae). Duas proteínas, SUGARWIN1 e SUGARWIN2 são produzidas em cana-de-açúcar, em resposta ao dano mecânico e ao ataque de D. saccharalis, porém estas proteínas não afetam o inseto, e sim ocasionam alterações fisiológicas e morfológicas em F. verticillioides e C. falcatum, ocasionando a morte destes fungos por apoptose. Dietas artificiais suplementadas com estes fungos oportunistas ocasionaram o ganho de peso da D. saccharalis. Esses dados indicam uma interação mais íntima entre o inseto e estes patógenos de cana, sendo que, neste estudo procuramos identificar relações simbióticas entre os indivíduos, analisando se a forma de transmissão desses fungos é mediado pela D. saccharalis. Os resultados mostraram a presença do F. verticillioides em todas as fases de desenvolvimento da D. saccharalis após contato com o fungo, ou seja, depois de se alimentarem em dieta suplementada por F. verticillioides no 4º instar, permaneceram infectadas pelo fungo ao longo de toda a fase pupal e adulta, em ambos os sexos. Além disso, o F. verticillioides foi transmitido para os descendentes de D. saccharalis, sendo que o fungo foi detectado nos ovos, ou seja, um caso original de transmissão vertical. Por meio de microscopia, também foi possível verificar a alta intensidade de F. verticillioides no interior do intestino de lagartas. Estes dados inferem em uma relação simbiótica entre F. verticillioides e D. saccharalis, onde o simbionte é transferido verticalmente para as gerações subsequentes. As respostas obtidas com o fungo C. falcatum diferiram daquelas obtidas com F. verticillioides, uma vez que não se detectou a presença do fungo a partir da fase pupal. Neste caso, a relação de simbiose entre o fungo e o inseto pode resultar em uma transmissão horizontal. Com este estudo foi possível identificar diferentes formas de transmissão por D. saccharalis para dois fungos envolvidos em podridão de colmo em cana-de-açúcar. Estes dados mudam a forma como é vista a transmissão de F. verticillioides por D. saccharalis em cana-de-açúcar, podendo influenciar a forma de manejo da podridão de Fusarium e da broca nos canaviais. / In sugarcane, stem colonization by opportunistic fungi, such as Fusarium verticillioides and Colletotrichum falcatum, is directly linked to the attack of Diatraea saccharalis (Lepidoptera: Crambidae) caterpillar. Two proteins, SUGARWIN1 and SUGARWIN2 are produced in sugarcane, in response to mechanical damage and attack of D. saccharalis, however these proteins do not affect the insect, but cause physiological and morphological changes in F. verticillioides and C. falcatum, causing the death of these fungi by apoptosis. Artificial diets supplemented with these opportunistic fungi caused the weight gain of D. saccharalis. These data indicate a more intimate interaction between the insect and the sugarcane pathogens. In this study, we sought to identify symbiotic relationship among individuals, analyzing whether the transmission of these fungi is mediated by D. saccharalis. The results showed the presence of F. verticillioides in all stages of D. saccharalis development after contact with the fungus, in the 4th instar. The caterpillars remained infect by the fungus throughout the pupal and adult phase, in both sexes. In addition, F. verticillioides was transmitted to D. saccharalis offspring, being detected in eggs, an original case of vertical transmission. Through the microscopy results, it was also possible to verify the high intensity of F. verticillioides inside the intestines of caterpillar. These data infer in a symbiotic relationship between F. verticillioides and D. saccharalis, where the symbiont is transferred vertically to the offspring. The responses obtained with C. falcatum differed from those obtained with F. verticillioides, since the presence of the fungus was not detected from the pupal phase. In this case, the symbiont relationship between fungus and insect can result in a horizontal transmission. With this study was possible to identify different forms of fungi transmission by D. saccharalis. These data change the way the transmission of F. verticillioides by D. saccharalis in sugarcane is viewed, and may influence the management of Fusarium rot and sugarcane borer attack in sugarcane.

Le système d'incompatibilité végétative a été décrit chez tous des champignons (Eumycètes) comme intervenant dans la limitation des fusions somatiques entre conspécifiques. Chez les champignons la fusion somatique est uniquement possible entre individus de même GCV (Groupe de Compatibilité Végétative). Comme tous les systèmes de reconnaissance du soi, le fonctionnement du système d'incompatibilité végétative des champignons est basé sur une grande diversité allélique. Cette thèse propose d'étudier la relation qui semble exister entre cette diversité des gènes impliqués dans l’incompatibilité végétative des champignons et la pression parasitaire exercée par des éléments cytoplasmiques délétères (ou DCE) transmis lors des fusions somatiques. Trois problématiques ont été abordées, avec trois approches différentes : (1) une approche conceptuelle générale portant sur l’évolution des systèmes de reconnaissance du soi, (2) une approche de modélisation sur le maintien de la diversité en GCV de la population de champignon par un DCE et (3) une approche expérimentale, pour étudier d’une part la perméabilité de la barrière d‘incompatibilité végétative et d’autre part l’interaction C. parasitica/CHV et les liens existant entre transmission et virulence du CHV. Ces études ont permis de montrer l'importance de la perméabilité de la barrière d'incompatibilité végétative à la fois au niveau du maintien de la diversité génétique de la population d'hôte et au niveau de la prévalence des DCE. Il semblerait donc que les DCE évoluent vers des niveaux de virulence faible du fait de la limitation de leur transmission par le système d'incompatibilité végétative de leur hôte. Nos résultats expérimentaux suggèrent que lorsque la diversité en GCV de la population d'hôte est faible, la virulence des DCE pourrait évoluer suivant le modèle du trade-off impliquant une évolution vers un niveau de virulence intermédiaire optimal. Ces travaux permettent donc de mieux comprendre les mécanismes agissant sur l'écologie et l'évolution des interactions champignon/DCE qui, au vu de cette étude, apparaissent comme de bon modèles pour l’étude des systèmes hôtes/parasites. / Vegetative incompatibility systems have been described in Fungi as controlling somatic fusion between conspecifics. For fungi, only fungi of the same vc type can fuse together. As other self recognition systems, this system involved high allelic diversity at specific genes. The issue of this work is to study the cause and effect relationship between the evolution of vegetative incompatibility systems and the selective pressure drove by cytoplasmic deleterious elements, transmitted during somatic fusion. Three problematics with three different approach were done : (1) a conceptual general framework on the evolution of self recognition systems (2) a theoretical work on the maintenance of vc type diversity by DCE and (3) an experimental work on the study of relationship between transmission and virulence in the C. parasitica/CHV host-parasite system. Ours results showed the key role of the permeability of the vegetative incompatibility barrier both for vc type diversity maintenance and on DCE prevalence. DCE would evolve toward avirulence in response to the transmission limitation by host incompatibility systems. Experimental work suggested a positive link between virulence and transmission in some population of CHV when host present a low vc type diversity, which could allow the evolution of the DCE toward an intermediate optimal virulence. This study would shed some light on mechanisms acting on the ecology and the evolution of fungi/DCE interaction which, according to our results, would be good study models for works on host-parasite systems.