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Infeção por Toxocara em animais de companhia: abordagem ao tratamento e ao controlo
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Abstract(s)
Toxocarose é uma doença provocada por nemátodes da família Ascarididae, da espécie Toxocara canis, no caso de cães, e Toxocara cati, no caso de gatos. Os cães e gatos desempenham um importante papel na transmissão destes parasitas ao ser humano, através da excreção de ovos nas fezes. A toxocarose é considerada uma zoonose de grande importância em Saúde Pública. Embora a espécie Toxocara cati seja considerada menos importante na transmissão desta zoonose, alguns autores defendem que Toxocara cati é um agente subestimado. Toxocara canis é um parasita que suscita interesse devido a algumas particularidades entre as quais: elevada sobrevivência nos tecidos (podendo chegar a anos); capacidade de atravessar a placenta e infectar o feto; tropismo para o tecido neurológico nos hospedeiros paraténicos; secreção de um conjunto de glicoproteínas biologicamente activas, in vivo e in vitro; e ainda o facto de possuir um glicocálice à superfície, que permite evasão à resposta imunológica do hospedeiro.
É importante conhecer a biologia e os factores de risco para a sua transmissão, a fim de serem tomadas medidas eficazes de tratamento e controlo da infecção por estes helmintas, por exemplo pelo uso adequado de antiparasitários. O tratamento a instituir nos animais infectados dependerá da sua idade e do seu estado fisiológico. De uma forma geral, utilizam-se benzimidazóis na prevenção e tratamento de Toxocara. No entanto, quando ocorre migração larvar, este tratamento é pouco efectivo, uma vez que apresenta baixa solubilidade, levando a tratamentos prolongados com doses elevadas. Para além da falta de eficácia contra determinados estadios do parasita, é importante considerar as resistências aos fármacos. Desta forma, as combinações de anti-helmínticos são cada vez mais frequentes, demonstrando uma maior eficácia no tratamento e controlo destes parasitas.
Nesta dissertação pretende-se efectuar uma revisão bibliográfica das medidas de tratamento e controlo disponíveis para infecções pelo género Toxocara, em cães e gatos, através de uma análise crítica de vários factores determinantes, nomeadamente: a biologia do parasita e os seus mecanismos de evasão às respostas imunológicas do hospedeiro; a fase de infecção, tendo em conta o estado fisiológico do animal; e ainda, a acção de diversos anti-helmínticos considerando as diversas fases de vida do parasita e do estado imunológico do hospedeiro.
Toxocariasis is a disease caused by nematodes of Ascarididae family, more specifically Toxocara canis and Toxocara cati in cats and dogs, respectively. This disease is a very important zoonosis, given that both dogs and cats have an important role in the transmission of parasites to humans through the excretion of eggs in the faeces. Toxocariasis is considered a zoonosis of great public health importance Although the species Toxocara cati is considered less important in the transmission of this zoonosis, some authors claim that Toxocara cati is an underrated agent. Toxocara canis is a parasite that raises a lot of interest due to some special features such as: high survival in tissues (sometimes for years); ability to cross the placenta and infect the foetus; neurological tissue tropism for the parathenic hosts; secretion of a number of biologically active glycoproteins in vivo and in vitro; and also the presence of a glycocalyx on the surface, allowing evasion to the host immune response. It is important to understand the biology and the risk factors of the transmission, in order to treat and control helminth infections, for example by the appropriate use of antiparasitic drugs. The treatment of the infected animals depend on their age and their physiological state. In general the prevention and treatment of Toxocara infections is attained by the use of benzimidazoles. However, when larval migration occurs, this treatment is not very effective since it has a low solubility, leading to prolonged treatments at high doses. Apart from the lack of effectiveness against certain stages of the parasite, it is also important to consider the drug resistance. Thus, anthelmintic combinations are increasingly common, demonstrating a greater efficacy in the treatment and control of these parasites. This dissertation aims to present a literature review of prophylactic measures and available treatments for infections genus Toxocara in dogs and cats, through a critical analysis of several key factors, including: the biology of the parasite and its evasion strategies to the host immune responses; the stage of infection, taking into account the physiological state of the animal; and, the action of various antihelmintics considering the various life stages of the parasite and the immune status of the host.
Toxocariasis is a disease caused by nematodes of Ascarididae family, more specifically Toxocara canis and Toxocara cati in cats and dogs, respectively. This disease is a very important zoonosis, given that both dogs and cats have an important role in the transmission of parasites to humans through the excretion of eggs in the faeces. Toxocariasis is considered a zoonosis of great public health importance Although the species Toxocara cati is considered less important in the transmission of this zoonosis, some authors claim that Toxocara cati is an underrated agent. Toxocara canis is a parasite that raises a lot of interest due to some special features such as: high survival in tissues (sometimes for years); ability to cross the placenta and infect the foetus; neurological tissue tropism for the parathenic hosts; secretion of a number of biologically active glycoproteins in vivo and in vitro; and also the presence of a glycocalyx on the surface, allowing evasion to the host immune response. It is important to understand the biology and the risk factors of the transmission, in order to treat and control helminth infections, for example by the appropriate use of antiparasitic drugs. The treatment of the infected animals depend on their age and their physiological state. In general the prevention and treatment of Toxocara infections is attained by the use of benzimidazoles. However, when larval migration occurs, this treatment is not very effective since it has a low solubility, leading to prolonged treatments at high doses. Apart from the lack of effectiveness against certain stages of the parasite, it is also important to consider the drug resistance. Thus, anthelmintic combinations are increasingly common, demonstrating a greater efficacy in the treatment and control of these parasites. This dissertation aims to present a literature review of prophylactic measures and available treatments for infections genus Toxocara in dogs and cats, through a critical analysis of several key factors, including: the biology of the parasite and its evasion strategies to the host immune responses; the stage of infection, taking into account the physiological state of the animal; and, the action of various antihelmintics considering the various life stages of the parasite and the immune status of the host.
Description
Keywords
Controlo Mecanismo de evasão Protocolo de desparasitação Sistema imunitário Toxocara Canis Toxocara Cati Tratamento Control Evasion mechanism Deworming protocol Immune system Treatment