Contacts Dr Phil Jones Dr Eleni Michalopoulou Nicola Henley Dr. Will Sopwith Dr. Androulla Efstratiou 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 that the role of unpasteurised milk consumption is decreasingly important. There have been several recent incidents where human cases of C. ulcerans have been associated with carriage or infection in pets. There is evidence that immunity to diphtheria afforded through the childhood vaccination programme is waning in adult populations and although a booster dose to address this has been introduced, population coverage with the booster is relatively low. There is, therefore, an increasingly vulnerable population in the UK and a potentially large reservoir of infection with little knowledge about the risks of zoonotic transmission. 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. Clinical presentation is associated with the formation of an oropharyngeal diphtheritic membrane (which can physically obstruct respiration) and the absorption of toxins leading to neurological and cardiac disease and frequently resulting 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 Russia and the newly independent states of the former Soviet Union during the 1990s. Small numbers of cases of diphtheria caused by C. diphtheriæ are still diagnosed in the UK but are often associated with travel to countries where the disease is endemic. 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. C. ulcerans does not cause large epidemics and, although human-to-human transmission is thought to be unlikely, the organism has been isolated from a pair of siblings and from a father and son. Over recent years, C. ulcerans has been isolated from clinical samples in many countries including the USA, Canada, Japan, Germany, Italy, the Netherlands, Switzerland and France. In the UK, 50 clinical isolates of toxigenic C. ulcerans were submitted to the Streptococcus and Diphtheria Reference Unit between 1986 and 2003. Since that time, there have been two additional cases of diphtheria caused by C. ulcerans, one of which was fatal. Infection with C. ulcerans is increasingly recognised as an emerging infectious disease in many countries, including the UK, and there is evidence that the number of cases and the severity of clinical signs may be increasing. However, the source of the majority of human cases remains unknown. C. ulcerans has been associated with clinical mastitis in cattle and people drinking unpasteurised milk from affected herds have become infected. Nevertheless, an increasing number of cases of C. ulcerans infection in humans do not appear to be associated with the consumption of unpasteurised dairy products, raising the possibility that other animal reservoirs may exist. Evidence to support this hypothesis is starting to accumulate. Seven isolates of C. ulcerans were identified in cats with bilateral nasal discharge in the UK in 2002 - 2003. All isolates were found to be toxigenic and were of the same ribotypes as 50 human isolates from the UK, suggesting that cats may act as a reservoir for human infection. In addition, C. ulcerans has been isolated from pet dogs that were in contact with three human cases of the disease in the UK and France. The organism has been isolated from a range of other species, but isolation from pet cats and dogs is potentially very important from a public health perspective. C. ulcerans is not recognised as a major pathogen of animals and is certainly not of economic importance. As a result, animal health organisations (including DEFRA) do not consider it a funding priority. In addition, studies investigating animal populations for the presence of potential human pathogens do not attract human health funding. However, the implications for human patients and their families can be devastating and the health protection resource required to investigate, including the assessment and communication of risk, is significant. 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 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. Colonies sub-cultured from individual animals 80 cat 70 dog Number of animals 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 Number of colonies References De Zoysa A, Hawkey PM, Engler K, George R, Mann G, Reilly W, Taylor D and Efstratiou A. (2005). Characterization of toxigenic Corynebacterium ulcerans strains isolated from humans and domestic cats in the United Kingdom. J Clin Microbiol 43(9) 4377-81. (1997). Respiratory diphtheria caused by Corynebacterium ulcerans--Terre Haute, Indiana, 1996. MMWR Morb Mortal Wkly Rep 46(15) 330-2. Dewinter LM, Bernard KA and Romney MG. (2005). Human clinical isolates of Corynebacterium diphtheriae and Corynebacterium ulcerans collected in Canada from 1999 to 2003 but not fitting reporting criteria for cases of diphtheria. J Clin Microbiol 43(7) 3447-9. 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