An investigation by researchers from the Department of Parasitology at Bangladesh Agricultural University (BAU) has uncovered an alarming public health crisis, identifying three intestinal parasites –Cryptosporidium, Blastocystis, and Giardia species – as drivers of diarrhoea outbreaks, particularly in the densely populated slums of Bangladesh.

Conducted in a slum adjacent to Railway Colony in Mymensingh city, the study not only detected these pathogens in humans but also in local animals, underscoring a significant cross-species transmission risk. This breakthrough, led by Professor Dr Shahiduzzaman, marks a critical advancement in understanding health threats in underserved areas and carries profound implications for disease control under the ‘One Health’ approach, which integrates human, animal, and environmental health.

The research team, comprising Professor Dr Shahiduzzaman, postgraduate student Beni Amin from the Faculty of Veterinary Medicine, and graduate student Md Ashikuzzaman, collected 102 samples –including faeces, water, and soil – from children, adults, and a range of animals such as poultry, cows, goats, and pigeons.

“This study is a cornerstone for public health research in Bangladesh,” Shahiduzzaman told UNB, emphasizing the need to view humans, animals, and their shared environment as an interconnected system rather than isolated entities.

The samples underwent rigorous analysis, with DNA extracted in the laboratory and parasites identified using advanced PCR and sequencing techniques, ensuring precise detection of these microscopic threats.

The findings are striking. Blastocystis emerged as the most prevalent, detected in 24 samples, with a shocking 100% infection rate among goats, a discovery that left researchers astounded. The study identified seven subtypes of Blastocystis, with ST2 and ST3 confined to humans, while ST23 and ST24 were found in animals and birds, including goats and chickens within the same households.

This overlap suggests a dynamic transmission cycle, where parasites move freely between species, amplifying the risk. Cryptosporidium was present in eight samples, including one human case of Cryptosporidium parvum—typically transmitted from animals—alongside three goats, three chickens, and a soil sample containing Cryptosporidium meleagridis, a bird-related strain. Giardia intestinalis appeared in a single soil sample, likely originating from animal or human faeces, further illustrating the environmental contamination at play.

The study traced the spread to the slum’s unsanitary conditions, where unplanned sewage disposal, roaming animals, and scattered garbage create fertile ground for parasitic proliferation. “Contaminated water, soil, and sewage are major conduits,” Shahiduzzaman explained, highlighting how residents risk infection while bathing, washing clothes, or cleaning utensils.

The research also revealed that animals like cattle and goats contract these parasites from abandoned waste, posing a secondary threat to humans through direct contact.

This cycle of contamination is particularly alarming in slums, where overcrowded living conditions exacerbate health risks.

To address this crisis, the team advocates for a multi-pronged strategy. Raising awareness about hygiene, establishing designated sites for animal waste, and implementing a well-planned sewage system are seen as immediate priorities to curb the spread.

Shahiduzzaman stressed the urgency of these measures, noting, “Creating a healthy environment is essential to break the infection cycle in densely populated, underserved areas.”

As a pilot project, the study provides a foundation for larger-scale investigations, with plans to extend research to other slums, rural regions, and urban centres across Bangladesh.

“This initial data will guide more comprehensive studies, revealing the true extent of parasitic infections,” he added, calling for government and private sector sponsorship to fuel this effort.