Abstract
Dispersion or dilution of stool by water from heavy rainfall may affect Strongyloides stercoralis free-living development producing infective filariform larvae (FL). This study examined effect of water dilution of stool on survival of S. stercoralis free-living development. One g of stool was prepared in water so that its soluble component was diluted sequentially from 1:2 to 1:480. Three dishes were used to compare FL production in three culture conditions: stool suspension, stool sediment deposited in soil, and isolated rhabditiform larvae (RhL) deposited in soil. The fourth dish was for developmental observation of RhL into free-living stages. Numerous FL were generated from undiluted or 1:2 diluted stool and stool sediment placed on soil. However, starting from dilution 1:5, FL production continuously decreased in both stool suspensions and stool sediments placed on soil. RhL isolated from stool dilutions placed on soil gave rise to few FL. Worm mating were seen at 24-30 hours in dilutions 1:20-1:120 only. Highest numbers of FL from indirect free-living cycle were 1/3 of those from control. FL production decreased as stool dilution increased, and reached zero production at 1:160 dilution. Rainfall may disperse or dilute stool so that nutritional supplement for S. stercoralis free-living development is insufficient.
Highlights
A preliminary observation revealed that some RhL died when placed in diluted stool suspension, while some survived but gave rise to stunted free-living adult worms
Rainfall disperses soil-transmitted helminth eggs and helps in spreading the infection[9]. This may not be the case for S. stercoralis, as RhL need to grow into adult males and females, mate, and produce progeny which develop into infective filariform larvae (FL)
Our unpublished study conducted in Moklan subdistrict of Thasala district, Nakhon Si Thammarat province, southern Thailand, revealed that the prevalence of hookworm (Necator americanus) infection was 52% while that of strongyloidiasis was only 13%
Summary
A preliminary observation revealed that some RhL died when placed in diluted stool suspension, while some survived but gave rise to stunted free-living adult worms. We aimed to study the growth and development of S. stercoralis RhL in diluted stool or in soil. Results Effect of water dilution of soluble stool component on worm development.
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