Cambodia and the continuum between animals, people and the environment

Welcome to the first of a new series of blog posts, as I document my mission to explore the diversity of zoonotic parasites in regions of the Asia Pacific alongside investigation into how to better control the diseases they cause.

I’m a postdoctoral research fellow at the Melbourne Veterinary School, University of Melbourne, Australia, where I develop and test intervention strategies to mitigate the impact of zoonotic parasites on people and animals residing in resource-limited settings. However, I haven’t always been Melbourne-based. Prior to my big move ‘Down Under’ I lived in the southern Italian city of Bari where I first graduated in Veterinary Medicine and then obtained a PhD in Animal Health and Zoonoses.

During my research period in Bari, I was fortunate enough to have the chance to explore the epidemiology of zoonotic parasites in several European countries, including Portugal, Bosnia and Herzegovina and Italy, as well as some further afield in Asia. This culminated with an investigation into the zoonotic parasites affecting companion animals in eight different countries in East and Southeast Asia, giving me the opportunity to journey widely whilst also igniting my curiosity for regions and cultures of the Asia Pacific.

As someone that grew up in one of the Mediterranean basin’s main harbours, I am used to witnessing a variety of people and their cultures flocking to the coast. Most of these people faced challenging travels from some of the poorest areas of Europe, Africa and the Middle East, often suffering from little-known diseases, such as those caused by parasites.

I was always fascinated by how, regardless of the suffering they went through, they were always able to quickly adapt to the new environments they found themselves in whilst also retaining the foundations of their respective cultures. I can vividly recollect spending time with the changing travelling communities that would live for periods in the meadowed areas around Bari, seeing excited and barefooted children playing, adults cooking up their national dishes, with dogs and all sorts of other backyard animals living alongside them. It is moments like these, seeing animals and humans existing in such close proximity that must have been the starting point for my passion of what I later learnt is the concept of One Health.  Having a holistic view of the continuum between people, animals, and the environment around them, can provide clues and shine a spotlight on the variety of drivers influencing the appearance of a pathogen and its associated disease.

All these characteristics found place in the project I’m currently leading in Cambodia. This pilot study aims at providing evidence that a One Health approach is more effective in controlling zoonotic hookworms than human-focused strategies.

Hookworms are blood-feeding soil transmitted helminths (STHs) causing infections of the small intestine. These parasites cause infections in nearly a billion people worldwide (~50% in the Asia-Pacific), causing impaired physical and cognitive development in children and poor neonatal outcomes. The World Health Organization has for long time provided guidelines for the control of STHs which proved successful in reducing the morbidity of these parasitic agents on a large scale. These recommendations are based on the assumption that Necator americanus and Ancylostoma duodenale, which are human-specific, are the main hookworms causing disease globally. However, epidemiological data obtained through molecular tools in the last 10 years have demonstrated that Ancylostoma ceylanicum is the second most common hookworm of humans in the Asia-Pacific, affecting roughly 100 million people. Importantly, A. ceylanicum is transmitted to humans from animals, with dogs acting as a reservoir of these pathogens. This zoonotic hookworm can reach prevalence as high as 90% in dogs in rural communities in Asia, where people, especially children, share a common environment, and greatly benefit from the human-animal bond.

Thanks to the Soulsby fellowship I’ll be able to deliver mass drug administration to school age children and community dogs in resource-poor communities in Cambodia. We will measure the impact of this intervention by looking at whether there is a reduced proportion of animals and people suffering from the negative impacts of zoonotic parasites after implementation, exploring the genetic and epidemiological traits driving disease transmission, and perform a cost-effectiveness analysis of this intervention to advocate for relevant policy change. Overall, generating comprehensive data on the effectiveness of One Health interventions in the Asia-Pacific could save people and dogs from the negative impacts of zoonotic diseases.

It is such an honour to be a Soulsby ambassador and I look forward to delivering more blogs about this journey in Cambodia and other regions of the Asia Pacific.

Vito Colella