Made available in DSpace on 2014-06-11T19:27:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-22Bitstream added on 2014-06-13T20:27:43Z : No. of bitstreams: 1 demoner_lc_me_botfmvz.pdf: 668999 bytes, checksum: f0837d7e0a185cd0a8385b4105355512 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Hepatozoon canis é um hemoparasita transmitido por carrapatos que afeta cães em diversas regiões do mundo. Rhipicephalus sanguineus é considerado seu vetor biológico, entretanto, é possível que existam outros vetores. No Brasil, H. canis é descrito principalmente em áreas rurais, onde cães podem ser infestados por outras espécies, incluindo Amblyomma spp. O objetivo do presente trabalho foi infectar experimentalmente diferentes espécies de carrapatos com H. canis, a partir de cães naturalmente infectados. Para isso, foram utilizadas ninfas de A. cajennense e R. sanguineus e adultos de A. cajennense e A. ovale. Após o ingurgitamento dos espécimes em animal infectado, foi realizada pesquisa de formas evolutivas do protozoário na hemolinfa, intestino e hemocele dos ixodídeos, por técnicas citológicas e histológicas. Alguns carrapatos foram submetidos ao diagnóstico molecular pela técnica de PCR. Somente em duas fêmeas de A. cajennense foram observadas estruturas morfologicamente semelhantes a Hepatozoon spp. e uma fêmea de A. ovale apresentou oocistos na hemocele. Além disso, duas fêmeas de A. ovale e uma de A. cajennense foram positivas na PCR. Entretanto, não é possível caracterizar essas espécies como vetores de H. canis, pois foram usados muitos exemplares nas infecções experimentais e poucos foram capazes de se infectar com o parasita. É provável que R. sanguineus tenha pouca importância epidemiológica na transmissão de H. canis no Brasil, pois este estudo, assim como pesquisas anteriores, demonstraram que a espécie foi incapaz de se infectar experimentalmente com o protozoário / Hepatozoon canis is a hemoparasite that afflicts dogs in several regions of the world. Rhipicephalus sanguineus is considered to be the biologic vector of this agent, although other species may act as possible vectors. In Brazil, H. canis is described mainly in rural areas, where dogs are infested by other species, such as Amblyomma spp. The aim of this study was to transmit experimentally H. canis to different species of ticks, using naturally infected dogs. For this purpose A. cajennense and R. sanguineus nymphs and A. cajennense and A. ovale adults were used. After the repletion of specimens fed on a naturally infected animal, we searched for development forms of the protozoa in hemolymph, gut and hemocoel of the ticks by cytological and histopathologic examinations. Some ticks were also examined by molecular detection (PCR). Only two female ticks of the species A. cajennense contained structures morphologically similar to Hepatozoon spp. and oocysts were recovered from the hemocoel of an A. ovale female. In addition, two females of A. ovale and one female of A. ovale were positive through PCR. However, our results are not enough to characterize these species as vectors of H. canis mainly because many ticks were used in experimental infections and few were infected with the parasite. It is likely that R. sanguineus has little epidemiological importance in the transmission of H. canis in Brazil, since this research and previous researchers demonstrated that R. sanguineus was unable to experimentally get infected with the protozoan

Orientador: Lucia Helena O'Dwyer / Banca: Elizabeth Moreira dos Santos Schmidt / Banca: Gervásio Henrique Bechara / Resumo: Hepatozoon canis é um hemoparasita transmitido por carrapatos que afeta cães em diversas regiões do mundo. Rhipicephalus sanguineus é considerado seu vetor biológico, entretanto, é possível que existam outros vetores. No Brasil, H. canis é descrito principalmente em áreas rurais, onde cães podem ser infestados por outras espécies, incluindo Amblyomma spp. O objetivo do presente trabalho foi infectar experimentalmente diferentes espécies de carrapatos com H. canis, a partir de cães naturalmente infectados. Para isso, foram utilizadas ninfas de A. cajennense e R. sanguineus e adultos de A. cajennense e A. ovale. Após o ingurgitamento dos espécimes em animal infectado, foi realizada pesquisa de formas evolutivas do protozoário na hemolinfa, intestino e hemocele dos ixodídeos, por técnicas citológicas e histológicas. Alguns carrapatos foram submetidos ao diagnóstico molecular pela técnica de PCR. Somente em duas fêmeas de A. cajennense foram observadas estruturas morfologicamente semelhantes a Hepatozoon spp. e uma fêmea de A. ovale apresentou oocistos na hemocele. Além disso, duas fêmeas de A. ovale e uma de A. cajennense foram positivas na PCR. Entretanto, não é possível caracterizar essas espécies como vetores de H. canis, pois foram usados muitos exemplares nas infecções experimentais e poucos foram capazes de se infectar com o parasita. É provável que R. sanguineus tenha pouca importância epidemiológica na transmissão de H. canis no Brasil, pois este estudo, assim como pesquisas anteriores, demonstraram que a espécie foi incapaz de se infectar experimentalmente com o protozoário / Abstract: Hepatozoon canis is a hemoparasite that afflicts dogs in several regions of the world. Rhipicephalus sanguineus is considered to be the biologic vector of this agent, although other species may act as possible vectors. In Brazil, H. canis is described mainly in rural areas, where dogs are infested by other species, such as Amblyomma spp. The aim of this study was to transmit experimentally H. canis to different species of ticks, using naturally infected dogs. For this purpose A. cajennense and R. sanguineus nymphs and A. cajennense and A. ovale adults were used. After the repletion of specimens fed on a naturally infected animal, we searched for development forms of the protozoa in hemolymph, gut and hemocoel of the ticks by cytological and histopathologic examinations. Some ticks were also examined by molecular detection (PCR). Only two female ticks of the species A. cajennense contained structures morphologically similar to Hepatozoon spp. and oocysts were recovered from the hemocoel of an A. ovale female. In addition, two females of A. ovale and one female of A. ovale were positive through PCR. However, our results are not enough to characterize these species as vectors of H. canis mainly because many ticks were used in experimental infections and few were infected with the parasite. It is likely that R. sanguineus has little epidemiological importance in the transmission of H. canis in Brazil, since this research and previous researchers demonstrated that R. sanguineus was unable to experimentally get infected with the protozoan / Mestre

The aim of this study was to investigate three key epidemiological aspects of Theileria parva infections in cattle and African buffalo (Syncerus caffer) in South Africa. The first of these was the possible behavioural change (i.e. transformation) of buffalo-derived T. parva (causing classical Corridor disease in cattle) to what might be considered cattle-derived T. parva (causing classical East Coast fever in cattle) after repeated tick-passage in cattle. For the first time a South African isolate of buffalo-derived T. parva was successfully transmitted using Rhipicephalus zambeziensis for eight passages in non-splenectomised cattle. This was achieved despite most animals developing fatal infections with extremely low piroplasm parasitaemias, and without chemotherapeutic intervention. This finding indicates that, contrary to earlier belief, Corridor disease is not a self-limiting disease in cattle, and given the opportunity, could well become established in a cattle population in the absence of buffalo. Despite repeated tick transmission in cattle of the South African buffalo isolate of T. parva used in this study, it did not exhibit the behavioural changes associated with “transformation” to typical cattle-derived T. parva. Secondly, the potential role of the common waterbuck (Kobus ellipsiprymnus) in the selection of cattle-adapted subpopulations of parasites from buffalo-derived T. parva was investigated. Waterbuck captured in Kruger National Park (KNP) were screened by conventional and molecular diagnostic techniques for Theileria spp. infections. Laboratory-reared R. zambeziensis were fed on captive buffalo confirmed to be naturally infected with T. parva. The ensuing adult ticks were fed on captive waterbuck and cattle. All the waterbuck were found to carry microscopically detectable Theileria sp. piroplasm infections, found by polymerase chain reaction (PCR) diagnosis to belong to a hitherto uncharacterised Theileria species. R. zambeziensis adults which fed as nymphs on the buffalo transmitted fatal T. parva infections to cattle. However, no transmission of T. parva to the waterbuck could be demonstrated clinically or by PCR diagnosis. Also, R. zambeziensis nymphs that were subsequently fed on the waterbuck failed to transmit T. parva to cattle in the ensuing adult stage, confirming the absence of T. parva-group infections in the waterbuck. The results suggest that buffalo in KNP probably do not carry T. parva-group parasites which are readily transmissible to common waterbuck and waterbuck are therefore unlikely to play an important role in the epidemiology of T. parva-group infections in cattle in South Africa. Thirdly, to investigate the carrier state of buffalo-derived T. parva infections in cattle, blood from infected non-splenectomised and splenectomised carrier cattle was subinoculated to splenectomised cattle. T. parva infections were successfully transmitted by subinoculation of 1000 ml of blood at various intervals after infection to splenectomised recipient cattle. Donor animals comprised of recovered intact cattle, reacting intact cattle or splenectomised recovered cattle. Microscopically detectable piroplasm parasitaemias were detected in all recipients after inoculation. One splenectomised recipient developed a moderate clinical reaction, accompanied by a moderate schizont parasitosis, but recovered spontaneously, confirming persistence of schizonts in some T. parva carrier animals. By contrast, a T. parva piroplasm infection, persisting in a treated recovered splenectomised bovine, in the apparent absence of circulating schizonts, was serially (consecutively) passaged in splenectomised cattle. Seroconversion occurred in all recipient cattle. With the exception of the recipient which developed a clinical reaction and circulating schizonts, none of the recipients showed any clinical signs of T. parva infection. Upon homologous sporozoite challenge with T. parva, two out of three recipient animals with only microscopically detectable piroplasm parasitaemias developed fatal T. parva infections and one recovered after exhibiting severe clinical signs. These findings confirm the stage-specific immunity in T. parva and, contrary to popular belief, the possibility of long-term maintenance of piroplasm parasitaemias in the absence of schizonts in carrier cattle. The technique of subinoculating and establishing virulent T. parva carrier infections in splenectomised cattle also provides a method whereby buffalo-derived parasite stocks may be isolated and maintained for characterisation and the preparation of sporozoite stabilates for inclusion in T. parva vaccines. Copyright / Dissertation (MSc)--University of Pretoria, 2011. / Veterinary Tropical Diseases / unrestricted