Identifying low risk insecticides that can enhance food production without increasing mortality of biocontrol agents for human schistosomiasis

Abstract

Synthetic chemicals, such as pesticides, have increased faster than other agents of global change have, yet their ecological impacts remain understudied. Additionally, agricultural expansion to address human population growth and food shortages is predicted to increase the use of pesticides, some of which have been linked to increases in infectious diseases of humans, such as schistosomiasis, which infects >250 million people worldwide. Previous work revealed that ecologically relevant concentrations of organophosphate and pyrethroid insecticides are highly toxic to crayfish. Whether these same insecticides are also highly toxic to Macrobrachium rosenbergii and M. vollenhovenii prawns, which are closely related to crayfish and are important predators on snails that transmit schistosomiasis in Asia and Africa, respectively, is unknown. We performed laboratory dose-response studies for M. rosenbergii using three pyrethroid (esfenvalerate, λ-cyhalothrin, and permethrin) and three organophosphate (chlorpyrifos, malathion, and terbufos) insecticides. Pyrethroid LC50 values were consistently several orders of magnitude lower than for organophosphate insecticides. Pyrethroids also had a greater likelihood of field runoff at levels lethal to prawns. To corroborate these findings in natural settings, we experimentally tracked survival of individually caged M. vollenhovenii at 31 waterways in West Africa that varied widely in their insecticide use. Consistent with laboratory results, pyrethroid insecticide use in these villages was positively associated with Macrobrachium mortality when controlling for village-level and prawn-level attributes, including levels of organophosphate applications. Villages with the most pyrethroid use had lower prawn survival, despite using on average 20% less total insecticides than villages with high prawn survival. Our findings suggest that pyrethroid insecticides widely used in sub-Saharan Africa have strong non-target effects on Macrobrachium spp. prawns, with possible implications for human schistosomiasis. Thus, regulations or incentives to avoid high-risk insecticides, especially near waterways, could have important human health implications in countries undergoing agricultural expansion in schistosomiasis-endemic regions.

Why the World Health Organization should reconsider long lasting insecticide nets (LLIN) and indoor residual spraying (IRS) in primary mosquito/malaria control in favour of house screening

“…Fresh water pollution from agricultural insecticide use poses intolerable threat to marine biodiversity Yura et al, (2021). Haggerty et al, (2022) noted that pyrethroids can be several times more toxic than organophosphate insecticides and its runoffs can induce lethal toxic levels unto non-target beneficial organisms. In fresh water, insecticides runoffs from fields become toxic to prawns (Macrobrachium sp.)…”

Agricultural Innovations to Reduce the Health Impacts of Dams

“…The breakdown of vegetation, produces both a nutrient-rich amendment for crops while simultaneously offering natural gas that can be used for cooking or for powering generators. By reducing reliance on fertilizers, these approaches might, indirectly, further reduce schistosome transmission [30,31,54,55]. These innovations have great potential for using aquatic vegetation to improve agricultural production and profitability.…”

“…This practice is already common in South Asia [70,71], and could be applied to the rapidly growing area under rice cultivation on the African continent [69]. Identifying and using insecticides that minimize harm to aquaculture species would be necessary for this strategy to succeed [55].…”