Can Interacting Pathogens Explain Disease Patterns?

A group of scientists in the UK and the US has been studying the behaviour of infectious parasites in rabbits. The findings could lead to us being able to predict more successfully when infectious cyclical diseases in humans are likely to occur.

The team from Cardiff University's School of Biosciences, University of Stirling, University of Liverpool and Penn State University, Pennsylvania, have discovered that when rabbits are infected with more than one disease at a time, the diseases can interact with each other, changing their courses and potentially resulting in a more severe infection.

Most animals including humans are infected with more than one disease at any one time.

The research findings point to the possibility that any disease which follows a natural cycle could have that cycle changed by an interaction with another disease.

Dr Joanne Lello, Cardiff School of Biosciences, said that the findings provide a new way of looking for interactions between organisms which cause disease and provides another piece in the puzzle in terms of understanding how pathogens behave.

She said: "There has been a long standing debate as to whether co-infecting organisms interact with one another or whether interactions matter in natural pathogen systems. The debate continues because these interactions are so hard to detect in nature.

"What this study has provided us with is a new method of detection. For example, when we test this method on real data, such as where we examine changes in parasitic worm numbers in rabbits, it reveals changes in seasonal patterns of one type of worm when another type is present.

"Many diseases show cycles and if interactions change these cycles then there could be wide-ranging consequences and understanding this can help us better understand pathogen patterns. For example it could help scientists to predict more clearly when parasite outbreaks may occur."

"The whole subject of co-infection biology is very exciting as it has implications for everything from theoretical biology to how we treat infectious diseases."

The study is detailed in the leading scientific journal American Naturalist.

The paper "Pathogen interactions, population cycles and phase shifts" is published in The American Naturalist in January.