Do worms transmit disease causing bacteria to humans?

Issue date: 11 October 2007

Bioluminescents shows glowing bacteria in a nematode worm Do worms transmit bacteria that cause diseases (pathogens) to humans? A team of researchers led by the University of the West of England has just secured funding from the Natural Environment Research Council (NERC) to investigate if nematode worms – including those that are common in the soil and eat bacteria – can spread those same bacteria to humans and animals. Nematodes are ubiquitous and live in all climates, from Tropical to Arctic, therefore they can be found in any soil, in every country.

The research is a collaboration between scientists at UWE, the Centre for Infectious Disease Dynamics (CIDD) at Penn State University in the US and the University of Bristol Veterinary School at Langford.

Research Fellow, Dr Lizeth Lacharme-Lora from UWE is working on the project, she said, “In recent years, life-style trends have motivated people to a higher consumption of fresh produce such as fruit and vegetables, particularly, organic products. However, although apparently healthier, these products (especially those where animal manures are used to enrich the soil), could come accompanied by pathogen-containing nematodes that are present in the soil where the products are cultivated.

“Organic foods focus on the absence of pesticides, but microbiological safety studies on these products are still required. Our study will shed some light onto this aspect.”

Lead researcher, Dr Vyv Salisbury from UWE, said, “We are thrilled to get the support of NERC – it is a first for UWE to receive funding from this Research Council so something of a coup for the university.

“We are also delighted to be working with world class institutions such as CIDD and the Bristol Vet School. The research project has three strands to discover if nematode worms pose a threat to human health when they enter the body via accidental ingestion or as a parasite. First, we will find out how bacterial pathogens survive when ingested by soil-dwelling worms, then we will determine if bacteria can be transferred into the body via parasitic worms and finally test to see if the bacteria becomes more virulent when harboured inside a worm's body.

“We already know that worms do harbour bacteria that cause human disease (pathogens). For example it is possible that pathogens entering the body protected by a worm might not be killed by stomach acids because the worm might act as a shield protecting the bacteria. We want to find out if normal defence mechanisms in the body are less effective when invaded by pathogen carrying nematodes.

“Pathogens that we already know can be carried by worms include E. coli O157 and salmonella. These bacteria can cause severe gastrointestinal infections in humans and are commonly found in soil. The first part of our research will be carried out in the labs at UWE. We will use 'glowing bacteria' or bioluminescence to track what happens to bacteria when they are eaten by the model worm Ceanorhabditis elegans. We will use genetically modified salmonella and E.coli O157 that express lux genes so that they become self bioluminescent, that is to say they will glow if they are alive and stop glowing if they die.

“The fantastic thing about glowing bacteria is that it will be easy for us to see if the bacteria do in fact remain alive inside the worm when ingested. Bioluminescence is an incredible reporter system – the modified bacteria emit light when they are alive and can therefore be seen within the organism they are infecting.

The research will then move on to the US where we will investigate whether parasitic worms can transmit pathogens into and between animals, again using bioluminescence to detect if the bacteria carried by the worms stay alive when the worm enters the body. This will mean it is possible to see if the bacteria leave the worm and can establish an infection in the animal. .

Sarah Perkins; collaborator in the US, says “Our theory is that bacteria hitch-hike a ride into the body using parasitic worms and in doing so they evade being fought off by the immune system. Once in the body, the bacteria may then be released during the course of the worm's feeding and cause an infection. The novel use of bioluminescent bacteria will actually allow us to see whether parasitic worms are indeed acting as a 'Trojan Horse'. This is a very exciting and novel application of bioluminescence, which has never before been used in disease ecology, and allows us to investigate a question that has huge implications for human and animal health”

The work at the Vet School will focus on DNA micro tests to find out if the bacterium becomes more infectious when carried by the nematode worms.”

“The research findings will have important implications for the dynamics and control of pathogens as we will ascertain precisely what, if any, dangers are implicated in the carriage of bacteria dangerous to human and animal health via free-living or parasitic worms.”


Editor's notes

Visual available, caption: Bioluminescents shows glowing bacteria in a nematode worm.

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