Pathogens transmitted in animal feces in low- and middle-income countries.

Miranda J Delahoy,Breanna Wodnik,Jenna Swarthout,Matthew C Freeman,Lydia Mcaliley,Karen Levy,Gauthami Penakalapati

doi:10.1016/j.ijheh.2018.03.005

Miranda J Delahoy, Breanna Wodnik + Show 5 more

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https://doi.org/10.1016/j.ijheh.2018.03.005

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Abstract

Animals found in close proximity to humans in low-and middle-income countries (LMICs) harbor many pathogens capable of infecting humans, transmissible via their feces. Contact with animal feces poses a currently unquantified-though likely substantial-risk to human health. In LMIC settings, human exposure to animal feces may explain some of the limited success of recent water, sanitation, and hygiene interventions that have focused on limiting exposure to human excreta, with less attention to containing animal feces. We conducted a review to identify pathogens that may substantially contribute to the global burden of disease in humans through their spread in animal feces in the domestic environment in LMICs. Of the 65 potentially pathogenic organisms considered, 15 were deemed relevant, based on burden of disease and potential for zoonotic transmission. Of these, five were considered of highest concern based on a substantial burden of disease for which transmission in animal feces is potentially important: Campylobacter, non-typhoidal Salmonella (NTS), Lassa virus, Cryptosporidium, and Toxoplasma gondii. Most of these have a wide range of animal hosts, except Lassa virus, which is spread through the feces of rats indigenous to sub-Saharan Africa. Combined, these five pathogens cause close to one million deaths annually. More than half of these deaths are attributed to invasive NTS. We do not estimate an overall burden of disease from improperly managed animal feces in LMICs, because it is unknown what proportion of illnesses caused by these pathogens can be attributed to contact with animal feces. Typical water quantity, water quality, and handwashing interventions promoted in public health and development address transmission routes for both human and animal feces; however, sanitation interventions typically focus on containing human waste, often neglecting the residual burden of disease from pathogens transmitted via animal feces. This review compiles evidence on which pathogens may contribute to the burden of disease through transmission in animal feces; these data will help prioritize intervention types and regions that could most benefit from interventions aimed at reducing human contact with animal feces.

Highlights

Many pathogens capable of infecting humans can be found in animal feces, yet the feces from these animals pose a currently unquantified—though likely substantial—risk to human health (Dufour et al, 2012)
As the majority of reviewed literature on human health impacts from exposure to animal feces has focused on health outcomes related to exposure to enteric pathogens or helminths (Penakalapati et al, 2017), we first considered all enteric pathogens and soil-transmitted helminth (STH) that were included in two recent large studies describing an array of enteric pathogens/STHs: the Global Enteric Multicenter Study (GEMS) and MAL-ED (The Etiology, Risk Factors, and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health Study) (Houpt et al, 2014; Panchalingam et al, 2012)
We considered pathogens detected in studies that met the inclusion criteria of that review, as well as pathogens from additional papers marked as relevant during the title and abstract assessment, if the abstract mentioned pathogens not previously considered or new pathogen-animal host pairs from research in an low- and middle-income countries (LMICs)

Summary

Introduction

Many pathogens capable of infecting humans can be found in animal feces, yet the feces from these animals pose a currently unquantified—though likely substantial—risk to human health (Dufour et al, 2012). Insufficient separation of animal feces from human domestic environments can lead to fecal-oral transmission of zoonotic pathogens through direct contact with animal feces or soil, or fecal contamination of fomites, food, or water sources (Penakalapati et al, 2017). Systematic reviews have demonstrated a 30–40% decrease in childhood diarrhea after the introduction of improved sanitation in low- and middle-income countries (LMICs) (Freeman et al, 2017; Wolf et al, 2014), but several recent water, sanitation, and/or hygiene interventions have failed to find consistent evidence of decreasing rates of childhood diarrhea, decreasing fecal contamination of household stored water, decreasing soil-transmitted helminth (STH) infections, and/or improving anthropometric indicators of malnutrition (Clasen et al, 2014; Null et al, 2018; Patil et al, 2014). One possible conclusion is that these interventions failed to interrupt a critical pathway in pathogen transmission: exposure to animal feces

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