Presentation on theme: "A case of human leptospirosis linked to pet rats BACKGROUND Leptospirosis is a relatively uncommon zoonotic infection in England and Wales with an average."— Presentation transcript:
A case of human leptospirosis linked to pet rats BACKGROUND Leptospirosis is a relatively uncommon zoonotic infection in England and Wales with an average of less than 40 laboratory confirmed human cases annually (Source: HPA). Leptospira interrogans is subdivided into numerous serovars and further classification is possible with molecular typing. In the UK, clinical disease in animals is mainly seen in dogs (kidney and liver disease), cattle (milk drop, reproductive failure) and pigs (reproductive failure). L. icterohaemorrhagiae infection can cause liver disease in a wide range of species, including man (Weil’s disease). Wild animals, especially rodents, are common carriers and reservoirs of infection but are clinically unaffected. Although wild rats are known to be frequently infected 1, pet (fancy) rats are considered to be free of infection. Infection is acquired from direct or indirect contact with infected animal urine; incubation period in man varies from 3 to 30 days. Serosurveys in the USA have demonstrated evidence of past infection in up to one third of people tested 2. It is usually a mild, self-limiting flu-like illness in man although Weil’s disease results in hepato-renal failure and haemorrhages. There are 1 or 2 deaths per year from leptospirosis in the UK. CASE REPORT AND INVESTIGATION In July 2006, the Veterinary Laboratories Agency (VLA) diagnosed leptospira infection in 2 pet rats and reported it to HPA. The owner of the rats (index case) had been in hospital with hepato-renal failure; Weil’s disease was suspected. The 2 rats were from a group of 4 (from litter of 18) brought in by a “Saturday girl” and distributed through a pet shop earlier in year. The pet shop did not usually sell rats (just hamsters, gerbils, mice, rabbits) but shop owner kept 2 pet rats. The animals offered for sale were healthy; pet shop met Health and Safety requirements (enforced by Local Authority). Figure 1: Timeline of key events CONTROL MEASURES ADOPTED Pet shop visited by a local animal warden, EHO and CCDC. Shop owner advised to remove all (14) small rodents from sale and from public access; subsequently agreed to test these, plus his own 2 rats. This required culling to undertake PCR on kidney tissue. Litter mates of infected rats were traced and owners given advice on leptospirosis control, hygiene measures and testing. The 2 other sibling rats (from the original litter of 18) distributed from the pet shop were also culled for laboratory testing. Of the remaining 14 sibling rats: one had died, 6 were untraceable and 7 were traced but the owners declined testing. The mother of the index rats was traced but testing was also declined. The owners of potentially infected rats were advised that they should not be handled by other people, not used for breeding and not mixed with other rats. LABORATORY TESTING L icterohaemorrhagiae infection was confirmed in the index case following serological testing at the hospital where being treated. Initial screening of the rats used LightCycler Real Time PCR which detects a 370bp amplicon of the 16S rRNA gene of pathogenic leptospires 3. Re-amplified purified DNA template was sequenced to confirm the presence of pathogenic leptospires. Speciation was undertaken using Denaturing High Pressure Liquid Chromatography (DHPLC) 4. Indistinguishable molecular profiles consistent with one of five serovars including L icterohaemorrhagiae found in PCR positive rats. Two rats were also tested by serology using a microscopic agglutination test (MAT) 5. Very high titres (1/1600 and 1/400) for L. icterohaemorrhagiae were detected. Table 1: Summary of results of laboratory testing of animals CONCLUSIONS AND RECOMMENDATIONS The source of infection was identified as contact with pet rats. This conclusion was based on the most comprehensive range of animal tests currently available (VLA are also developing multi locus variant analysis (MVLA) to further improve serovar identification). We were unable to determine whether the primary source of infection was the 4 litter mates brought into the shop, the resident rats or whether the two groups were independently infected. It seems possible that Infection of fancy rats may be more common than previously thought and further research is indicated in this field. Serological surveys are needed to compare the level of past exposure in rat fanciers compared with the general human population. Pet rats should be considered a potential risk for leptospiral infection and the importance of hygiene emphasised to owners. References 1.Carter ME, Cordes DO. Leptospirosis and other infections of Rattus rattus and Rattus norvegicus. New Zealand Vet Jnl 1980; 28: 45-60. 2. Vinetz JM, Glass GE et al. Sporadic urban leptospirosis. Ann Int Med 1996; 125: 794-98. 3. Gallego-Beltrain, J.F (2001), Leptospirosis in Columbian Cattle; Microbiological, serological, molecular and epidemiological aspects of the disease. PhD thesis, RVC, London 4. Fenner and others (submitted for publication). Analysis of 16S rDNA sequence from pathogenic Leptospira serovars and use of single nucleotide polymorphisms for rapid speciation by DHPLC 5. Pritchard, D.G (1986), Proceedings of CEC veterinary research programme, Belfast 1984 Acknowledgements The veterinary investigations described were funded by Defra under the FZ2100 project within the Food and Environmental Safety programme of the VLA Wendy Phillips 1, Rosemary McNaught 1, June Chambers 1, Paul Rhodes 2, Catriona Gaudie 3, Charlotte Featherstone 3, Jane Errington 4, Jackie Fenner 5, Geoff Pritchard 6 1 Health Protection Agency, Yorkshire and Humber 2 Sheffield City Council Environmental Services 3 Veterinary Laboratories Agency, Thirsk 4 Veterinary Laboratories Agency, Penrith 5 Veterinary Laboratories Agency, Weybridge 6 Veterinary Laboratories Agency, Bury St Edmunds Specimen PCR/DHPLC (Kidney) MAT (Sera) Index rat 1POSITIVENot done Index rat 2POSITIVENot done Sibling rat 1POSITIVE Sibling rat 2NegativePOSITIVE Resident rat 1POSITIVENot done Resident rat 2NegativeNot done Assorted small rodents (14) NegativeNot done Figure 2: Rodent contact tracing and testing
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