O modelo Echinostoma paraensei (Trematoda:Digenea): avaliação do grau de compatibilidade entre hamster e rato Wistar, características do desencistamento in vitro e das alterações morfológicas provocadas pelo artesunato

Abstract

Echinostoma paraensei is recognized as an appropriate model, among other factors, due to ease of maintenance in the laboratory cycle. Little is known about the development kinetics of hosts with different degrees of compatibility, the factors involved on excystation and the susceptibility of these stages to treatment with herbal medicine. In this thesis these aspects were analyzed. Metacercariae of E. paraensei were removed from Biomphalaria glabrata and incubated in vitro in Alkaline trypsin bile salts for excystation study. The excystation depended on the presence of trypsin and bile salts, but not of concentrations studied, reaching high levels after 2 hours. By light microscopy were verified four stages of development: encysted, activated, breached and excysted, similar to that described for other species of the genus. By confocal laser scanning microscopy was played that newly excysted metacercariae showed a similar morphology to adults helminths, with the exception of the reproductive system structures in which are present as genital anlage. Albino rats and hamsters were infected by gavage and necropsied at 3, 7, 14 and 21 days after infection. By light microscopy were verified highest worm recovery rate in hamster, especially in the last two weeks. In this host was higher fertility rate, represented by greater number of ovigerous specimens. Rather, morphometric data of the gonads were significantly lower in rats. By confocal microscopy was observed atrophied ovaries, specimens with no vitelline glands, although there was spermiogenesis and spermatozoa in the seminal vesicle. The data add new information about the hamster as compatible host of E. paraensei. The study of phenotypic aspects of helminth incubated in vitro is a suitable method to monitor the development of therapeutic activities. Metacercariae were maintained in RPMI 1640 with 1, 10, 25, 50 and 100 µg/mL artesunate. At concentrations 25 µg/ mL of the drug there was increased of mortality rate and progressive reduction of movements. The concentrations of 100 µg/mL and 50 µg/mL showed deleterious effects after 24 and 48 h, respectively. For scanning electron microscopy was found that the helminths incubated with 50 and 100 µg /mL of artesunate showed swelling, blebs, holes, eruptions, folds on the integument and loss of collar spines. For the first time it was shown that excysted larvae are susceptible to treatment. The data set confirms that E. paraensei is an appropriate model for in vitro studies or in vivo trematodes biology. In vitro culture of the facilities, point to the possibility of providing alternative approaches to the study of development and testing of plant-derived drugs with potential anthelmintic activity. From an ethical point of view, the in vitro culture can help to reduce the use of animals in the early stages of testing of drugs.