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Publication
Prevalência e fatores de Risco da Teileriose Bovina na Raça Alentejana
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Advisor(s)
Abstract(s)
A Teileriose bovina é uma hemoparasitose amplamente distribuída, com elevado impacto económico
e produtivo. É causada por protozoários do género Theileria, sendo Theileria orientalis uma das
espécies, e que é transmitida por carraças do género Haemaphysalis. Em Portugal, a doença manifesta se principalmente na região do Alentejo durante os meses mais quentes, devido à maior atividade do vetor. O ciclo de vida de Theileria spp. envolve uma fase assexuada no hospedeiro vertebrado e uma
fase sexuada no hospedeiro invertebrado, existindo possibilidade de transmissão transestadial no
hospedeiro invertebrado. Os sinais clínicos incluem anemia, hipertermia, fraqueza, perda de apetite,
entre outros. O diagnóstico pode ser clínico ou laboratorial, com destaque para técnicas moleculares,
como a reação em cadeia da polimerase, pela sua elevada sensibilidade. No que respeita ao
tratamento, não existe ainda uma terapêutica específica amplamente eficaz, existindo substâncias
como a buparvaquona, pertencente à classe das naftoquinonas, que demonstram eficácia variável. Por
outro lado, o controlo desta parasitose requer a implementação de estratégias eficazes de combate
ao vetor, embora existam limitações associadas à resistência a fármacos, ausência de vacinas eficazes
e dificuldades logísticas em sistemas extensivos.
O presente estudo visa determinar a prevalência de infeção por Theileria orientalis em bovinos da raça
Alentejana, bem como a possível coinfeção com Theileria annulata, e identificar eventuais fatores de
risco associados. A identificação desses fatores poderá fornecer informações relevantes para a
implementação de medidas de controlo mais eficazes, contribuindo para o bem-estar animal, a
produtividade e a sustentabilidade das explorações.
Na realização deste trabalho foram utilizadas 420 amostras de sangue de bovino da raça Alentejana,
as quais foram sujeitas a extração de ADN. Foi realizada a amplificação de um fragmento do gene da
principal proteína de superfície do piroplasma da Theileria orientalis por PCR, seguido de eletroforese
em gel de agarose e os resultados foram visualizados com recurso a um transiluminador UV. Por fim,
foi realizada a análise estatística dos dados obtidos.
Com a realização deste estudo, foi possível apurar que, das 420 amostras analisadas, 45 testaram
positivo para Theileria orientalis, correspondendo a uma prevalência de 10,7 %. A análise dos fatores
de risco permitiu concluir que animais do sexo feminino e animais mais velhos apresentam uma maior
predisposição para a infeção. Relativamente à estação do ano, as amostras colhidas na primavera
apresentaram uma prevalência de 25,8 % (34/132), evidenciando que esta variável apresenta
significância estatística relevante no contexto da infeção por este hemoparasita.
Com este estudo verificamos que a Teileriose continua a representar um desafio relevante para a
saúde animal. Neste sentido, torna-se essencial a manutenção e o reforço das medidas de
biossegurança, bem como o desenvolvimento de estratégias terapêuticas mais eficazes, incluindo a
investigação de novos princípios ativos com maior eficácia contra esta piroplasmose e o eventual
desenvolvimento de uma vacina preventiva ou seleção de animais mais resistentes.
Bovine theileriosis is a widely distributed hemoparasitic disease with significant economic and productive impact. It is caused by protozoa of the genus Theileria, with Theileria orientalis being one of the species, and is transmitted by ticks of the genus Haemaphysalis. In Portugal, the disease is mainly observed in the Alentejo region during the warmer months, due to increased vector activity. The life cycle of Theileria spp. involves an asexual phase in the vertebrate host and a sexual phase in the invertebrate host, with the possibility of transstadial transmission occurring in the invertebrate host. Clinical signs include anemia, hyperthermia, weakness, loss of appetite, among others. Diagnosis can be clinical or laboratory-based, with molecular techniques, such as polymerase chain reaction (PCR), standing out due to their high sensitivity. With regard to treatment, there is still no widely effective specific therapy, although substances such as buparvaquone, belonging to the naphthoquinone class, have shown variable efficacy. On the other hand, the control of this parasitosis requires the implementation of effective vector control strategies, although there are limitations related to drug resistance, lack of effective vaccines, and logistical difficulties in extensive farming systems. The present study aims to determine the prevalence of infection by Theileria orientalis in Alentejana breed cattle, as well as the potential co-infection with Theileria annulata, and to identify possible associated risk factors. The identification of these factors may provide relevant information for the implementation of more effective control measures, contributing to animal welfare, productivity, and the sustainability of farming operations. For this study, 420 blood samples from Alentejana breed cattle were used, and DNA extraction was performed. Amplification of a fragment of the major piroplasm surface protein gene of Theileria orientalis was carried out by PCR, followed by agarose gel electrophoresis, and results were visualized using a UV transilluminator. Finally, statistical analysis of the obtained data was conducted. Through this study, it was found that out of the 420 samples analyzed, 45 tested positive for Theileria orientalis, corresponding to a prevalence of 10,7%. The analysis of risk factors indicated that female animals and older animals have a higher predisposition to infection. Regarding the season of the year, samples collected in the spring showed a prevalence of 25,8% (34/132), indicating that this variable presents statistically significant relevance in the context of infection by this hemoparasite. This study confirms that theileriosis continues to pose a relevant challenge to animal health. In this regard, it is essential to maintain and strengthen biosecurity measures, as well as to develop more effective therapeutic strategies, including the investigation of new active compounds with greater efficacy against this piroplasmosis, and the potential development of a preventive vaccine or the selection of more resistant animals.
Bovine theileriosis is a widely distributed hemoparasitic disease with significant economic and productive impact. It is caused by protozoa of the genus Theileria, with Theileria orientalis being one of the species, and is transmitted by ticks of the genus Haemaphysalis. In Portugal, the disease is mainly observed in the Alentejo region during the warmer months, due to increased vector activity. The life cycle of Theileria spp. involves an asexual phase in the vertebrate host and a sexual phase in the invertebrate host, with the possibility of transstadial transmission occurring in the invertebrate host. Clinical signs include anemia, hyperthermia, weakness, loss of appetite, among others. Diagnosis can be clinical or laboratory-based, with molecular techniques, such as polymerase chain reaction (PCR), standing out due to their high sensitivity. With regard to treatment, there is still no widely effective specific therapy, although substances such as buparvaquone, belonging to the naphthoquinone class, have shown variable efficacy. On the other hand, the control of this parasitosis requires the implementation of effective vector control strategies, although there are limitations related to drug resistance, lack of effective vaccines, and logistical difficulties in extensive farming systems. The present study aims to determine the prevalence of infection by Theileria orientalis in Alentejana breed cattle, as well as the potential co-infection with Theileria annulata, and to identify possible associated risk factors. The identification of these factors may provide relevant information for the implementation of more effective control measures, contributing to animal welfare, productivity, and the sustainability of farming operations. For this study, 420 blood samples from Alentejana breed cattle were used, and DNA extraction was performed. Amplification of a fragment of the major piroplasm surface protein gene of Theileria orientalis was carried out by PCR, followed by agarose gel electrophoresis, and results were visualized using a UV transilluminator. Finally, statistical analysis of the obtained data was conducted. Through this study, it was found that out of the 420 samples analyzed, 45 tested positive for Theileria orientalis, corresponding to a prevalence of 10,7%. The analysis of risk factors indicated that female animals and older animals have a higher predisposition to infection. Regarding the season of the year, samples collected in the spring showed a prevalence of 25,8% (34/132), indicating that this variable presents statistically significant relevance in the context of infection by this hemoparasite. This study confirms that theileriosis continues to pose a relevant challenge to animal health. In this regard, it is essential to maintain and strengthen biosecurity measures, as well as to develop more effective therapeutic strategies, including the investigation of new active compounds with greater efficacy against this piroplasmosis, and the potential development of a preventive vaccine or the selection of more resistant animals.
Description
Keywords
Coinfeção Doença transmitida por carraças Infeção PCR Piroplasmose Prevalência Raça Alentejana Theileria annulata Theileria orientalis Coinfection Tick-borne disease Infection Piroplasmosis Prevalence Alentejana breed