A cow in Kenya. An on-going study in Nairobi, Kenya is investigating how zoonotic pathogens are introduced to urban populations through livestock commodity value-chains (photo credit: ILRI/Paul Karaimu).

A study by 12 Kenyan and UK institutions, including the University of Liverpool, the International Livestock Research Institute (ILRI) and the University of Nairobi, is investigating the role of urbanization in the origin and spread of zoonotic pathogens (those that spread between humans and animals) in Nairobi, Kenya.

According to an article published online and in print in the New Scientist in August 2014, the Nairobi study is investigating the effects of ‘close interactions between people and animals’ in urban settings on the spread of pathogens such as Escherichia coli, Campylobacter and Salmonella, which can infect both humans and animals.

The ‘Epidemiology, ecology and social-economics of disease emergence in Nairobi’ project is expected to reveal how pathogens are introduced into urban populations through ‘livestock commodity value chains’. Livestock are a key part of the study because zoonotic pathogens are likely to come from livestock and the close interaction between livestock, their products and people. The often cramped and unsanitary conditions found in informal settlements in African cities like Nairobi raise the risk of these pathogens crossing the species barrier.

According to the article, there have been cases of these pathogens getting into food chains in Africa. ‘In Swaziland in 1992, infected cattle passed a strain of E. coli to humans that caused bloody diarrhoea – the first such outbreak in the developing world – and the number of people visiting their doctor for diarrhoea jumped sevenfold in a month. Across Africa, diarrhoea is the single biggest killer of children.’

Researchers in the project are visiting livestock owners in Nairobi’s informal settlements such as Dandora and Korogocho and collecting blood and faecal samples from their animals for microbial DNA analysis. ‘By identifying where pathogens originate and concentrate along the food chains, the team hopes to make such outbreaks less likely.’

‘“The way you design your city and the way you structure your food system can play into a policy to prevent disease emergence,” says epidemiologist Eric Fèvre of the University of Liverpool, UK, who is based at ILRI in Nairobi.”

Fevre says the project is “‘redrawing the map of Nairobi, not based on geography but on the connectedness of animal and human populations, in terms of the bacteria that they share.”‘

Partners in this project, which is funded by the UK Research Council Environmental and Social Ecology of Human Infectious Diseases (ESEI) initiative, include the University of Liverpool, the Development Planning Unit at University College London, the International Institute for Environment and Development (IIED) in London, the University of Edinburgh, the University of Nairobi, the Kenya Medical Research Institute, the African Population and Health Research Center, the Royal Veterinary College, London and ILRI.

The article says that ‘so far, the effort has revealed that Nairobi’s food system is massively diverse, with meat and dairy products produced, sold and consumed across socio-economic boundaries. Pathogens that are widespread in poverty-stricken neighborhoods are also present in high-income areas.’ Researcher have also ‘found high concentrations of E. coli and alarming levels of antibiotic resistance linked to unregulated sales of veterinary drugs.’

Read the whole story: Mapping the web of disease in Nairobi’s invisible city

Find out more about the Epidemiology, ecology and socio-economics of disease emergence in Nairobi project