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Stronglyoides ransomi: factors influencing the in vitro development of the free-living generation
Abstract:
Among the progeny of parasitic females of Strongyloides ransomi, ransomi, males did not appear in significant numbers until the 7th week of infection in cases of simple infection, and until the 3rd week of infection in cases of multiple infection. The appearance of males was attributed to the effect of host immunity, the physiological ageing of the parasitic females, or both. Type of culture substrate and other cultural conditions did not influence the percent of larvae developing into males. Sex of larvae was determined prior to hatching, probably during oogenesis or embryogenesis. Culture conditions influenced the direction of development of female larvae. An initial pH below 5.9 or above 7.2 favored differentiation of larvae into infective larvae, whereas, intermediate initial pH levels favored development of free-living females. Baby pig substrate, autoclaved substrate, and substrate washed free of soluble chemicals (adverse cultural conditions) promoted differentiation toward infective larvae. Adult pig substrate, nonautoclaved substrate and unwashed substrate promoted differentiation toward free-living females. In general, adverse conditions inside the host and favor an indirect life cycle.
Insights
Male Strongyloides ransomi development is influenced by host immunity and infection intensity, not culture conditions. Environmental factors like pH and substrate impact female larvae
Area of Science:
- Veterinary Parasitology
- Helminthology
- Animal Health
Background:
- Strongyloides ransomi is a significant swine parasite.
- Understanding its life cycle is crucial for disease control.
- Factors influencing male and female larvae development require elucidation.
Purpose of the Study:
- To investigate the factors affecting the appearance of male Strongyloides ransomi.
- To determine the influence of host immunity and infection intensity on male progeny.
- To analyze the impact of environmental conditions on the differentiation of female larvae.
Main Methods:
- Controlled infection experiments in pigs (simple and multiple infections).
- Larval culture under varied substrate and pH conditions.
- Microscopic examination to determine sex and larval stage.
Main Results:
- Male Strongyloides ransomi appeared later in simple infections (7 weeks) than multiple infections (3 weeks).
- Culture substrate and conditions did not affect the proportion of male larvae; sex is determined pre-hatching.
- Initial pH and substrate type significantly influenced female larvae differentiation into free-living or infective stages.
- Adverse conditions (low/high pH, processed substrates) favored infective larvae, mimicking host environment.
Conclusions:
- Host immunity and infection intensity are key drivers for male Strongyloides ransomi production.
- Environmental factors, particularly pH and substrate, critically regulate the development pathway of female larvae.
- Adverse conditions promote the indirect parasitic life cycle, essential for host transmission.