Review: Zoonotic Enteric Parasites: A One Health Guide to Preventing Infection

One Health Newsletter: Volume 10 Issue 2

Author

Amber N. Barnes
Duke One Health Team, Duke Global Health Institute
Duke University School of Medicine & Department of Public Health, University of North Florida, Brooks College of Health

A Duke University One Health research team, working at the Institute of Veterinary Medicine in Mongolia, recently published a comprehensive guide to zoonotic enteric parasites (ZEPs) in humans, animals, and the environment. In this guide, Zoonotic Enteric Parasites: A One Health Guide to Preventing Infection , authors use an interdisciplinary approach to appeal to diverse One Health stakeholders and share critical information about risk factors for ZEP exposure and strategies to prevent transmission in humans and animals. A corresponding slide set in English and Mongolian languages can be downloaded from the Duke One Health website for presentations and other educational purposes.

While working in remote rural communities of Mongolia, the research team noticed the absence of coordinated One Health efforts in response to zoonotic disease challenges. The field staff also encountered limited accessible information for human and animal health care providers practicing in Mongolia and more generally in low- and middle-income countries. These experiences facilitated direct interactions with veterinarians, clinicians, researchers, academics, and the public, who provided insight as this resource was developed. In this guide, authors describe prevention and control strategies and document case and outbreak responses. The report provides details on questionnaire development, recommendations for ZEP surveillance, and the incorporation of water, sanitation, and hygiene (WASH) messages and interventions to prevent ZEP transmission. Health promotion activities facilitate the dissemination of health messages to specific target audiences such a food handlers. Multiple potential sources of exposure, such as indiscriminate animal waste in the living space, components of household and WASH, and direct contact with animals (e.g., livestock, companion, wild, and synanthropic), are examined. Authors also describe risk factors for human infection, particularly in regards to cultural, economic, and socio-behavioral determinants of health as well as transmission within the environment.

Figure 1. Fecal-Oral Zoonotic Disease Transmission. A modified fecal-oral parasite transmission model including zoonotic contributions is presented. Adapted from Wagner, E. G., Lanoix, J. N., & World Health Organization. (‎1958)‎. Excreta disposal for rural areas and small communities / E. G. Wagner & J. N. Lanoix. WHO Monograph. World Health Organization, Geneva. 187pp. Accessible at: https://apps.who.int/iris/handle/10665/41687

Authors emphasize that a One Health effort is required to curb the ZEP transmission cycle. Transmission of a ZEP occurs after an unsuspecting host ingests the parasite, most often through the fecal-oral route. The F-diagram is a conceptual framework that illustrates the multiple fecal exposure pathways of a diarrheal pathogen (e.g., ZEP) to a new susceptible host (Wagner, Lanoix, & World Health Organization 1958). Disease exposures include the five Fs – contaminated fingers, flies, fomites, fluids, and fields or floors. The parasite then continues its life cycle and is released into the environment, where it can infect a new host and reinitiate the process. The drawback with the traditional F-diagram, however, is that it overlooks the fecal-oral pathogen ingestion from a One Health perspective. Human waste is not the only source of exposure for diarrhea-causing pathogens. Animal waste in the household and community serves as an additional exposure risk. In this guide, the authors created an updated F-diagram with humans, animals, and the environment in mind for both exposure pathways as well as host potential (Figure 1).

Most of the time, ZEP exposure will lead to an asymptomatic interaction between the host and the parasite; however, some infections lead to illness, particularly diarrheal diseases or chronic disorders. Scientists are still trying to determine what may be contributing to negative health outcomes in one host but not another. Recent research points to potential interactions between parasites and the host’s microbiome or microbial composition (Berrilli et al. 2012; Dheilly et al. 2017). Global health practitioners know that incessant bouts of diarrheal disease can cause a condition known as environmental enteropathy (EE) or environmental enteric dysfunction (EED). Chronic exposure to enteric pathogens like ZEPs create challenges with overall nutrition, physical and intellectual development, and even the body’s ability to properly respond to oral vaccines (Watanabe & Petri Jr 2016). New trends in One Health parasitological research may lead the way to understanding more about parasite pathogenicity and its converse relationship with the body’s unique microbiome (Vlčková et al. 2018).

Over the coming years, global health practitioners anticipate an increased incidence of enteric diseases, particularly zoonotic parasites, due to several One Health-related drivers. These factors include dietary changes and food trends, population growth and habitat expansion, climate change, increasing global food markets and trade, intensive farming and agriculture practices, human and animal movement, and longer life spans with resulting chronic illness (Broglia & Kapel 2011; Jaykus et al. 2008). Continued efforts to prevent future infections and promote better outcomes within our communities will require a collaboration of diverse resources. Creating similar open-access materials is vital for the promotion of multidisciplinary undertakings from human, animal, and environmental health disciplines across the globe. This indispensable One Health guide presents key scientific information for training and community education and encourages all stakeholders to take future steps to protect the health and well-being of our shared environment.

Guide Citation

Barnes, A. N., Davaasuren, A., Baasandagva, U., & Fieldhouse, J. (2018). Zoonotic enteric parasites: a One-Health guide for preventing infection. Durham, North Carolina: Duke University. Accessible at: https://sites.globalhealth.duke.edu/dukeonehealth/projects/team-3-zoonotic-enteric-parasite-disease-ecology-and-epidemiology-in-mongolia/

Cited References

Berrilli, F., Di Cave, D., Cavallero, S., & D'Amelio, S. (2012). Interactions between parasites and microbial communities in the human gut. Frontiers in Cellular and Infection Microbiology, 2, 141.

Broglia, A., & Kapel, C. Changing dietary habits in a changing world: emerging drivers for the transmission of foodborne parasitic zoonoses. Veterinary Parasitology, 182(1), 2-13.

Dheilly, N. M., Bolnick, D., Bordenstein, S., Brindley, P. J., Figuères, C., Holmes, E. C., Martinez, J., Phillips, A.J., Poulin, R., & Rosario, K. (2017). Parasite microbiome project: systematic investigation of microbiome dynamics within and across parasite-host interactions. mSystems, 2(4), e00050-17.

Jaykus, L. A., Woolridge, M., Frank, J. M., Miraglia, M., McQuatters-Gollop, A., Tirado, C., Clarke, R., & Friel, M. (2008). Climate change: implications for food safety. Rome, Italy: Food and Agriculture Organization of the United Nations.

Vlčková, K., Pafčo, B., Petrželková, K.J., Modrý, D., Todd, A., Yeoman, C.J., Torralba, M., Wilson, B.A., Stumpf, R.M., White, B.A., & Nelson, K.E. (2018). Relationships between gastrointestinal parasite infections and the fecal microbiome in free-ranging western lowland gorillas. Frontiers in Microbiology, 9: 1202.

Wagner, E. G., Lanoix, J. N., & World Health Organization. (‎1958)‎. Excreta disposal for rural areas and small communities / E. G. Wagner & J. N. Lanoix. WHO Monograph. World Health Organization, Geneva. 187pp. Accessible at: https://apps.who.int/iris/handle/10665/41687

Watanabe, K., & Petri Jr, W. A. (2016). Environmental enteropathy: elusive but significant subclinical abnormalities in developing countries. EBioMedicine, 10, 25-32.

 

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