Abstract
The importance of hands in the transmission of soil transmitted helminths, especially Ascaris and Trichuris infections, is under-researched. This is partly because of the absence of a reliable method to quantify the number of eggs on hands. Therefore, the aim of this study was to develop a method to assess the number of Ascaris eggs on hands and determine the egg recovery rate of the method. Under laboratory conditions, hands were seeded with a known number of Ascaris eggs, air dried and washed in a plastic bag retaining the washing water, in order to determine recovery rates of eggs for four different detergents (cationic [benzethonium chloride 0.1% and cetylpyridinium chloride CPC 0.1%], anionic [7X 1% - quadrafos, glycol ether, and dioctyl sulfoccinate sodium salt] and non-ionic [Tween80 0.1% -polyethylene glycol sorbitan monooleate]) and two egg detection methods (McMaster technique and FLOTAC). A modified concentration McMaster technique showed the highest egg recovery rate from bags. Two of the four diluted detergents (benzethonium chloride 0.1% and 7X 1%) also showed a higher egg recovery rate and were then compared with de-ionized water for recovery of helminth eggs from hands. The highest recovery rate (95.6%) was achieved with a hand rinse performed with 7X 1%. Washing hands with de-ionized water resulted in an egg recovery rate of 82.7%. This washing method performed with a low concentration of detergent offers potential for quantitative investigation of contamination of hands with Ascaris eggs and of their role in human infection. Follow-up studies are needed that validate the hand washing method under field conditions, e.g. including people of different age, lower levels of contamination and various levels of hand cleanliness.
Highlights
Ascariasis is an infection with the intestinal nematode Ascaris lumbricoides and it is estimated to infect over 800 million people worldwide [1]
This egg recovery rate was higher than that which was obtained with organosilane-coated Falcon tubes, irrespective of the type of pipette used, while the FLOTAC basic technique had a mean recovery rate of 43.3% (Table 1)
This paper presents a method for the recovery of Ascaris eggs from hands, based on a hand rinse and modified McMaster eggs enumeration
Summary
Ascariasis is an infection with the intestinal nematode Ascaris lumbricoides and it is estimated to infect over 800 million people worldwide [1]. Ascariasis is transmitted through the faecal-oral route; eggs are ingested following contact with contaminated hands, food, soil, or the deliberate act of eating contaminated soil. Infective A. lumbricoides eggs can survive, and remain infective for several months, or even for years in soil [2]. Eggs have been found on vegetables, especially in areas where excreta is used in agriculture [3,4], on utensils, and even on banknotes [5]. In endemic areas infection with A. lumbricoides reaches maximum intensity and prevalence in children aged between 5 and 15 years [6] and is associated with impairments in growth and cognitive performance. Studies have shown that reducing the worm burden can lead to marked improvements in weight gain, school performance and nutritional status [7]
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