A case of human leptospirosis linked to pet rats

1
A case of human leptospirosis linked to pet rats
Wendy Phillips1, Rosemary McNaught1, June
Chambers1, Paul Rhodes2, Catriona Gaudie3,
Charlotte Featherstone3, Jane Errington4, Jackie
Fenner5, Geoff Pritchard6
1 Health Protection Agency, Yorkshire and
Humber2 Sheffield City Council Environmental
Services3 Veterinary Laboratories Agency,
Thirsk 4 Veterinary Laboratories Agency,
Penrith5 Veterinary Laboratories Agency,
Weybridge 6 Veterinary Laboratories Agency,
Bury St Edmunds

• 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 (Weils
  disease).
• Wild animals, especially rodents, are common
  carriers and
• reservoirs of infection but are clinically
  unaffected.
• Although wild rats are known to be frequently
  infected1, 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 tested2.

• 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 leptospires3.
• 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

Figure 2 Rodent contact tracing and testing

• 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.

Figure 1 Timeline of key events

• References
• 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