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Rabbit parasite poses threat to humans
- Emma Keeble, Linda Dykes (16 December 2005)
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Indigenous Hepatitis E Virus Infections in England and Wales
- Hannah Catherine Lewis, Dilys Morgan, Samreen Ijaz and Elizabeth Boxall (9 June 2006)
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Emma Keeble, Veterinary Surgeon Exotic Animal Service, Royal (Dick) School of Veterinary Studies, University of Edinburgh, EH25 9RG, Linda Dykes
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Dear Editor, We were extremely interested to read the recent joint issue of the BMJ and the Veterinary Record (‘Animal and Human Health: strengthening the link’, Volume 157, Number 22) exploring the links between human and animal health issues. We wish to bring to the attention of both the medical and veterinary professions a potential emerging infection in humans, which as yet has not been reported in the UK and is not on the list of organisms routinely reported to the Centre for Disease Research. Encephalitozoon cuniculi is a mammalian microsporidian obligate intracellular protozoal parasite. It primarily infects rabbits, although it may be found in other mammal species and is zoonotic [1] This parasite is of particular importance in immunocompromised humans where it may cause severe life- threatening disease [2] A recent study conducted at the Royal (Dick) School of Veterinary Studies, University of Edinburgh, found serological evidence of exposure to this parasite in 52% of clinically healthy pet rabbits from across the UK. [3] Three strains of Encephalitozoon cuniculi have been identified. Strain III has been reported in dogs and in immunocompromised humans in the USA [4]. Strain II is associated with rodents and strain I is associated with rabbits. Strain I has been isolated from humans in Switzerland [1]. It is not known whether these strains are species specific or whether they can transfer freely between different hosts. No direct link between pet rabbits and human cases has been demonstrated: none owned a pet rabbit or recalled exposure to rabbits, but neither was any other source of infection identified. However, it has been shown that E.cuniculi strains of human origin can infect rabbits [5] and that the human strains isolated from AIDS patients are immunologically and molecularly identical to those isolated from rabbits. From this evidence it seems highly likely that E. cuniculi found in rabbits does pose a zoonotic risk to immunocompromised humans. There are an estimated 1.3-3 million pet rabbits in the UK: close contact between owners and susceptible pet species may lead to an increase in human exposure to E.cuniculi. At present there is no surveillance program for this disease in humans in the UK and the incidence is therefore unknown. Microsporidial infections in humans are an emerging field and are of interest to both the medical and veterinary profession as they pose a threat to both immunocompromised humans and infected animals. Yours faithfully, Emma Keeble BVSc Cert ZooMed MRCVS * Linda Dykes MBBS (Hons) MRCSEd A&E FFAEM ** * Exotic Animal Service, Small Animal Hospital, Department of Veterinary Clinical Studies, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Veterinary Centre, Roslin, Midlothian, EH25 9RG ekeeble@staffmail.ed.ac.uk ** A&E Department, Ysbyty Gwynedd, Bangor, Gwynedd, LL57 2PW References: 1. Deplazes P, Mathis A, Baumgartner R, Tanner I and Weber R (1996) Immunologic and molecular characteristics of Encephalitozoon-like microsporidia isolated from humnas and rabbits indicate that Encephalitozoon cuniculi is a zoonotic parasite. Clinical Infectious Diseases 22:557-9 2. Hollister, W.S, Canning E.U and Willcox A (1991) Evidence for widespread occurrence of antibodies to Encephalitozoon cuniculi (Microspora) in man provided by ELISA and other serological tests. Parasitology, 102, 33-43. 3. Keeble, E.J. and Shaw, D.J (in press) Seroprevalence of antibodies to Encephalitozoon cuniculi in domestic rabbits in the United Kingdom. The Veterinary Record. 4. Didier E, Didier P, Snowden K and Shadduck J (2000) Microsporidiosis in Mammals. Microbes and Infection. 2, 709-720. 5. Mathis A, Michel M, Kuster H, Muller C, Weber R and Deplazes P (1997) Two E.cuniculi strains of human origin are infectious to rabbits. Parasitology 114, 29-35 Competing interests: LD is a former trustee of the Rabbit Welfare Fund; she was involved in approving the RWF grant that supported the seroprevelance study by Keeble and Shaw (reference 3); EK conducted that study. |
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Hannah Catherine Lewis, Epidemiologist Health Protection Agency, Centre for Infections, London. NW9 5EQ, Dilys Morgan, Samreen Ijaz and Elizabeth Boxall
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Dear Editor, Palmer and colleagues undertook a qualitative risk assessment of the emerging zoonotic potential of porcine hepatitis E virus (HEV). They recommended enhanced surveillance of non-A, non-B, non-C hepatitis after noting that sporadic cases of HEV may be missed in humans as testing is not routine in the UK without a history of foreign travel (1). We investigated cases of HEV in England and Wales to describe the epidemiology and study possible risk factors for the acquisition of indigenous infection. Between 1st January 2005 and 30th June 2005, the Health Protection Agency HEV reference laboratories confirmed 181 cases of acute hepatitis E, including 5 deaths in patients with underlying serious medical conditions. Travel to an endemic area was recorded for 69 cases so further enquiries were made into the remaining 112 cases with an unknown travel history. Twenty-five (14%) cases had not travelled outside the UK in nine weeks prior to their illness and of these 20 (80%) were male and the median age was 59 years (IQR 43 – 71.5 years). Ten of these cases were PCR positive, all but one being HEV genotype 3 (N. American and European genotype). Twenty-four of the 25 cases had non-S. Asian names. Based on HEV genotype 3 and demographic information (age within IQR and non-S. Asian name), it is likely that an additional 23 cases for whom the travel history is unknown were likely to have acquired their infection in the UK. Twenty-two non-travel associated cases were interviewed using a detailed trawling questionnaire. Despite the striking demographic finding that the majority of cases were middle-aged to elderly Caucasian males, no common source, including contact with pigs or pig food products, has so far been identified by our study. The total number of cases reported in the first six months of 2005 was three times that expected based on routine voluntary surveillance and the proportion of non-travel associated cases was much larger than that previously reported (2). With the evolving epidemiology of HEV in England and Wales, HEV should be considered as an aetiological agent of acute and fulminant hepatitis in patients reporting no travel history. We therefore need to raise awareness of the requirement for further investigation of non-travel associated cases of non-A, non-B, non-C hepatitis among health professionals and standardise laboratory and hospital referral procedures. Hannah Lewis, Epidemiologist (hannah.lewis@hpa.org.uk); Dilys Morgan, Consultant Epidemiologist; Samreen Ijaz, Clinical Scientist Health Protection Agency, Centre for Infections, London. NW9 5EQ. Elizabeth Boxall, Clinical Scientist Health Protection Agency Heartlands Hospital, Birmingham B9 5SS. (1) Palmer S, Brown D, Morgan D. Early qualitative risk assessment of the emerging zoonotic potential of animal diseases. BMJ 2005; 331(7527):1256-1260. (2) Ijaz S, Arnold E, Banks M, Bendall RP, Cramp ME, Cunningham R et al. Non-travel-associated hepatitis E in England and Wales: demographic, clinical, and molecular epidemiological characteristics. J Infect Dis 2005;192:1166-72. Competing interests: None declared |
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