The National Centre for Zoonosis Research ~ Exploration of the prevalence of toxigenic Cornyebacterium ulcerans, an emerging human pathogen, in companion animals in NW England

Exploration of the prevalence of toxigenic Cornyebacterium ulcerans, an emerging human pathogen, in companion animals in NW England

Diphtheria caused by toxigenic Corynebacterium ulcerans is recognised as an emerging infectious disease in humans in many countries, including the UK.

There is increasing evidence that, as yet, uncharacterised animal reservoirs of C. ulcerans are significant for human disease and there have been several recent incidents where human cases of C. ulcerans have been associated with carriage or infection in pets.

C. ulcerans is not recognised as a major pathogen of animals and is certainly not of economic importance, therefore, there is a danger that C. ulcerans will fall between the responsibilities of animal and human health agencies, not being recognised as a significant health threat by either.

Background

Human diphtheria is a severe, acute disease of the upper respiratory tract, classically caused by toxigenic strains of Corynebacterium diphtheriæ. Infection with the bacteria can cause neurological and cardiac disease and frequently results in death.

Vaccination programmes developed in the first half of the twentieth century have dramatically reduced clinical disease around the world, but the potential still exists for large-scale epidemics, as demonstrated in countries of the former Soviet Union during the 1990s.

C. ulcerans is a closely related organism that can also produce the diphtheria toxin. Human infection with toxigenic strains of C. ulcerans can present as classical diphtheria, but other clinical presentations also occur.

If pets are able to act as symptomless carriers, it is essential to estimate the prevalence in animal populations and to identify risk factors for carriage. This work has not been done anywhere in the world and would provide invaluable information about potential animal reservoirs for this emerging infectious disease.

Preliminary Study

The use of 16s gene sequencing to characterise the range of Corynebacterium spp. isolated from the mouths of healthy dogs and cats in northwest England

Swabs from the oropharynx have been taken from around 500 cats and dogs at local rescue centres. These were cultured and presumptive Corynebacterium colonies were selected and transferred to fresh blood agar plates. Molecular identification of the isolates was carried out.

Preliminary Results

Healthy cats and dogs carry a range of Corynebacterium spp.
Sequencing of 16s gene identifies Corynebacterium spp. reliably ...

BUT

may not differentiate between some closely-related species, e.g. C. ulcerans and C. pseudotuberculosis.
Additional sequencing of other genes (e.g. rpoB) may be required on a small proportion of isolates to differentiate closely related Corynebacterium spp.