Concentration of soil-transmitted helminth eggs in sludge from South Africa and Senegal: A probabilistic estimation of infection risks associated with agricultural application

Abstract

The use of sludge in agriculture has been encouraged as a means of increasing soil nutrient content and improving the water holding capacity. On the negative side, major public health concerns with sludge application prevail, mainly due to the high concentration of pathogenic microorganisms. Soil-transmitted helminths (STHs) are of major health concern in this regard, especially in endemic regions, mainly due to the high environmental resistant of the eggs combined with a low infectious dose. In this study the concentration of STH eggs in two months dried sludge from Durban, South Africa and Dakar, Senegal was determined and compared. Sampling was carried out from January to October 2016 and in September 2016 for Dakar. Ascaris spp, hookworm, Trichuris spp, Taenia spp and Toxocara spp were the commonly recorded STH eggs. STH egg concentrations were higher in Dakar than in Durban, with viable STH egg concentrations exceeding both local and international guidelines. Due to the high concentration of viable STH eggs, risks of Ascaris spp infection was very high for farmers applying this sludge on their farms in both Durban (7.9 × 10−1 (±1.7 × 10−2)) and Dakar (9.9 × 10−1 (±1.3 × 10−5)). Consumption of lettuce grown on sludge amended soil will result in probable infections but harvest after 30 days between sludge application and harvest in Durban gave median probability infection risks with a risk level similar to the WHO tolerable risk value (10−4). This time period need to be prolonged to harvest in Dakar to 40 days to reduce the risks of infection to the tolerable risks values. Further treatment of the sludge either through composting or drying for longer periods of time is thus recommended from a public health perspective.

Helminth eggs assessment of fecal sludge in urban area of Bandung, Indonesia

“…In general, hookworm and A. lumbricoides are the common STH that is found in country with bad habits of sanitation practice, such as open defecation and poor handwashing habits and lack of sanitation infrastructure. STH egg concentration in sludge from main wastewater treatment plants is mainly depends on their concentration in raw wastewater [16]. Helminth eggs is very resistant in the environment and their survival could reach six months to one year in soils [17].…”

Contamination of urbanized territories with eggs of helmiths of animals

“…In rural area, eggs of helminths first of all pose a threat for farmers, who are most often in contact with contaminated objects of live stock (Amoah et al, 2018). Eggs of helminths were experimentally found in 60-100% of field samples, in 20-100% yard samples, in 0-20% samples from gardens and in 10-100% samples of compost.…”

“…Regarding rural area, in pastures, the most frequently observed parasites have been invasive larvae of Strongilata, gastrointestinal tract parasites, larvae of strongyloidiases and eggs of trematodes of agricultural animals (de Silva et al, 2003;Amoah et al, 2018;Campos et al, 2018).…”

Field-Scale Co-fermentation of Solid Waste From Urine-Diverting Dry Toilets (UDDT-SW) and Banana Waste to Produce Undissociated Carboxylic Acids to Inactivate Ascaris Eggs

“…One plastic chamber from each media bottle was removed during sampling on Day 6 and 15. Ascaris eggs were recovered from the plastic chambers using a method adapted from several methods published previously (Nelson and Darby, 2002;Bowman et al, 2003;Trönnberg et al, 2010;Amoah et al, 2018). First, the mesh from one side was peeled off, and a metal spatula was used to divide most of the contents between two 50-mL centrifuge tubes.…”