Strongyloides venezuelensis Brumpt, 1934: EVALUATION OF SOME ASPECTS OF THE INDIRECT CYCLE
Name: DEBORA GOLDNER ROSSI
Publication date: 17/05/2018
Advisor:
Name |
Role |
|---|---|
| FAUSTO EDMUNDO LIMA PEREIRA | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| BLIMA FUX | Internal Examiner * |
| FAUSTO EDMUNDO LIMA PEREIRA | Advisor * |
Summary: Introduction. Strongyloides venezuelensis (Brumpt, 1934) has been used as an experimental model of strongyloidiasis and its life cycle is complex and poorly known, with alternating generations of parasite and free-living stages.
Many aspects of the parasite biology are not clear, especially regarding the existence of free-living males. Objectives. The goal of this study is to verify which factors, related to the host or to the culture environment, can influence the development of adults of free-living stages in the indirect cycle of the parasite. Methods. Environmental factors were evaluated, such as: (a) vermiculite cultures and agar plates (Koga agar) and; (b) culture temperature. Regarding host factors, we evaluated: (c) experimental infection of the parasite in Swiss mice, Wistar rats, gerbils and hybrid rats from the crossing of Wistar rats with wild rats; (d) host age; (e) amount of inoculated larvae and; (f) immunological sensibilization with larvae inoculation. The ability to maintain the indirect cycle of the parasite was also evaluated by monitoring the positive cultures for free-living females for longer periods, as well as the cloning of freeliving females in order to verify whether parthenogenetic females may or may not maintain the free-living cycle. Results and Conclusions. (1) Firstgeneration free-living males were absent in different fecal culture conditions, maintained for three days, from the hosts. (2) The frequency of free-living females in the faeces cultures from different hosts was low at different culture conditions, except when faeces from wild hybrid rats were first submitted to temperature reduction (6°C) before incubation at 28°C, when the frequency of
those females increased significantly. (3) First-generation free-living females were able to maintain the heterogeneous cycle of the nematode, including males in later generations. (4) The free-living cycle of S. venezuelensis was
maintained in the laboratory, in successive cultures, apparently by parthenogenetic free-living females.
