One Health and WaSH

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One Health is a holistic approach that considers the interconnected health of the environment, humans, and animals. The WaSH (Water, Sanitation, and Hygiene) sector has begun to employ One Health principles with regards to climate and weather on environmental fecal contamination as well as animal feces management. However, there is room for greater application of a One Health approach on WaSH-relevant public health problems.

The WaSH sector’s interest in animal excreta is due to its capacity to serve as a source for human-contracted zoonotic infections. Accordingly, WaSH scholarship on animal excreta focuses the transmission pathways between animal feces and human. However, the transmission of enteric zoonotic infections from humans to animals and between animal populations goes largely unacknowledged by WaSH literature. Similarly, the effects that environmental conditions may have on animal-human transmission routes has not been exhaustively studied.

The health of animal populations is important for public health. Animal populations with higher exposures to zoonotic pathogens—be they from humans or other animals—can serve as reservoirs for these zoonotic pathogens. In addition, the health of domesticated animals has a direct effect on the economic well-being of humans, which is important for public health outcomes. Globally, livestock contributes about 40% to agricultural Gross Domestic Product, ranging from 10% in Cote D’Ivoire to more than 80% in Somalia. [1] There is only limited research on the global burden of animal disease and the resulting economic impacts in general, much less the burden of specific zoonotic diseases. The Global Burden of Animal Diseases programme has recently been launched to quantify the global burden of animal disease.2 Initial case studies are being developed in Australia, Ethiopia, Indonesia, Mexico, the Netherlands, Norway, Ireland, and the United Kingdom. [2] There are a few studies looking at economic losses associated with animal enteritis, such as one which found a average cost of £33 associated with each calf suffering from enteritis, including veterinary costs, opportunity costs, loss in calf value, and mortality costs. [4] Cryptosporidium spp is a zoonotic pathogen which is major cause of enteritis in calves and prevalence ranges from 3.4 to 96.6% in calf population. [3] Regardless given the large part livestock plays in economies, animal disease and zoonosis-related mortalities are likely to result in significant economic losses.

There are many interventions targeting pathogen prevalence in domestic animals, reducing overall circulation of the pathogens, but may not target fecal-oral transmission routes. For example, probiotics and antibiotics are used to reduce Campylobacter spp. circulation in poultry populations, as this pathogen can be transmitted by humans through exposure to undercooked meat from infected poultry (Campylobacter spp can also be transmitted to humans through fecal-oral transmission). [5] However, the widespread use of antibiotics in livestock populations, from industrialized meat production in the US to Nigerian pastoralists, has been attributed to increasing antimicrobial resistance. [6] Theoretically, some of the animal excreta management interventions may indirectly reduce transmission between animals by reducing the gross amount of pathogens in the environment. However, such interventions have mixed results in reducing exposures or negative health outcomes in humans so the likelihood of these interventions impacting animal transmission as well is probably low. [7]

Environmental conditions have been shown to affect the prevalence of diarrheal diseases, including zoonoses such as Toxoplasma gondi and Cryptospordium spp. [8–11] Further research has explored how climate change may affect the geographic distribution of enteric diseases [8], and there is growing scholarship in the WaSH sector on how climate change affects access to WaSH services. However, I could find no literature which considered the effect that natural disasters or climate change have on the interactions between humans and animals that may lead to changes in the amount or route of zoonotic enteric disease transmission.

To more fully understand the interactions between sanitation, animals, and the environment and their impact on health outcomes, interdisciplinary WaSH and veterinary research is needed to better understand 1) enteric disease transmission in livestock and associated economic cost, 2) how environmental conditions and climate change affect livestock-human interactions, and 3) how these changing interactions affect zoonotic transmission of enteric pathogens. Better understanding of these interactions and their outcomes will allow the WaSH and veterinary sectors to propose and evaluate interventions.


(1) Salmon, G. R.; MacLeod, M.; Claxton, J. R.; Pica Ciamarra, U.; Robinson, T.; Duncan, A.; Peters, A. R. Exploring the landscape of livestock “Facts”. Glob. Food Sec. 2020, 25, 100329.

(2) Rushton, J.; Huntington, B.; Gilbert, W.; Herrero, M.; Torgerson, P. R.; Shaw, A. P. M.; Bruce, M.; Marsh, T. L.; Pendell, D. L.; Bernardo, T. M.; et al. Roll-out of the Global Burden of Animal Diseases programme. Lancet 2021, 397 (10279), 1045–1046.

(3) Thomson, S.; Hamilton, C. A.; Hope, J. C.; Katzer, F.; Mabbott, N. A.; Morrison, L. J.; Innes, E. A. Bovine cryptosporidiosis: impact, host-parasite interaction and control strategies. Vet Res 2017, 48 (1), 42.

(4) Gunn, G. H.; Stott, A. W. A comparison of economic losses due to calf enteritis and calf pneumonia in Northern Scotland. International Symposia on Veterinary Epidemiology and Economics proceedings 1997, ISVEE 8: Proceedings of the 8th Symposium of the International Society for Veterinary Epidemiology and Economics (31-32), 10–10.

(5) Kaakoush, N. O.; Castaño-Rodríguez, N.; Mitchell, H. M.; Man, S. M. Global Epidemiology of Campylobacter Infection. Clin. Microbiol. Rev. 2015, 28 (3), 687–720.

(6) Alhaji, N. B.; Isola, T. O. Antimicrobial usage by pastoralists in food animals in North-central Nigeria: The associated socio-cultural drivers for antimicrobials misuse and public health implications. One Health 2018, 6, 41–47.

(7) Penakalapati, G.; Swarthout, J.; Delahoy, M. J.; McAliley, L.; Wodnik, B.; Levy, K.; Freeman, M. C. Exposure to animal feces and human health: A systematic review and proposed research priorities. Environ. Sci. Technol. 2017, 51 (20), 11537–11552.

(8) Delahoy, M. J.; Cárcamo, C.; Huerta, A.; Lavado, W.; Escajadillo, Y.; Ordoñez, L.; Vasquez, V.; Lopman, B.; Clasen, T.; Gonzales, G. F.; et al. Meteorological factors and childhood diarrhea in Peru, 2005-2015: a time series analysis of historic associations, with implications for climate change. Environ Health 2021, 20 (1), 22.

(9) Yan, C.; Liang, L.-J.; Zheng, K.-Y.; Zhu, X.-Q. Impact of environmental factors on the emergence, transmission and distribution of Toxoplasma gondii. Parasit. Vectors 2016, 9, 137.

(10) Britton, E.; Hales, S.; Venugopal, K.; Baker, M. G. The impact of climate variability and change on cryptosporidiosis and giardiasis rates in New Zealand. J Water Health 2010, 8 (3), 561–571.

(11) King, B. J.; Monis, P. T. Critical processes affecting Cryptosporidium oocyst survival in the environment. Parasitology 2007, 134 (Pt 3), 309–323.

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