Journal of the New Zealand Medical Association, 25-November-2005, Vol 118 No 1226
Prevalence of human pathogens in cat and dog fleas in New Zealand
Patrick Kelly, Jean-Marc Rolain, Didier Raoult
To date, murine typhus is the only rickettsial disease known to occur in New Zealand.1 The disease is caused by Rickettsia typhi which is transmitted by the oriental rat flea, Xenopsylla cheopis. Recently, the cat flea, Ctenocephalides felis, has been recognised as a vector of emerging human pathogens including R. felis, Bartonella henselae and B. clarridgeiae.1 In a preliminary study, DNA of R. felis, B. henselae and B. clarridgeiae were detected in cat fleas from the town of Palmerston North in New Zealand.2 To provide further information on the prevalence of these pathogens in New Zealand, we studied fleas from a further three sites in the North Island.
Fleas—Fleas were collected from cats and dogs presenting to private veterinary practices in Matamata, Lower Hutt, and New Plymouth townships. The fleas were preserved in 95% ethanol and identified using morphological criteria.3
Polymerase chain reaction (PCR)—Fleas were placed individually in sterile Eppendorf tubes and washed in sterile distilled water for 5 minutes before being macerated with a sterile pipette. DNA was extracted with the QIAamp Tissue Kit (QIAGEN, Hilden, Germany) according to the manufacturer’s instructions. This kit was also used to extract DNA from a human body louse reared in our laboratory (Unité des Rickettsies, France) under standard conditions and used as a negative control.
The flea DNA extracts were assayed as described previously4 with genus-specific primers for Bartonella derived from the its (intergenic spacer region) and the pap 31 (31-kDa major protein) gene, and for Rickettsia spp. with primers derived from the gltA (citrate synthase) and rOmpB (rickettsial outer membrane protein B) genes. Positive controls consisted of DNA extracted from laboratory cultures of B. elizabethae (for Bartonella) and R. montanensis (for Rickettsia).
Positive PCR products were sequenced using the dRhodamine Terminator cycle-sequencing ready reaction kit (PE Applied Biosystems, Les Ulis, France) according to the manufacturer’s instructions. Sequences obtained were compared with those in the GenBank DNA database using the BLAST program (version 2.0, National Center for Biotechnology Information, http://www.ncbi.nlm.nih.gov).
Between 1 and 13 fleas were collected from individual cats and dogs presenting to the veterinary practices in the study. DNA of R. felis, B. henselae and B. clarridgeiae was detected in 19%, 11%, and 7% of the 114 C. felis collected, respectively. No products were obtained from the negative control DNA from a human body louse and positive controls revealed appropriate amplicons.
Rickettsia felis was identified in fleas from all practices, while B. henselae was found in fleas from two practices (Lower Hutt and Matamata) and B. clarridgeiae in fleas from one practice (Matamata). The DNA of both B. henselae and B. clarridgeiae was found in three fleas (from two animals); B. clarridgeiae and R. felis in one flea; B. henselae and R. felis in five fleas (from three animals); and R. felis, B. henselae and B. clarridgeiae in two fleas (from one animal). No PCR products were obtained from the three C. canis.
Flea-borne spotted fever caused by R. felis is an emerging infectious disease that has been reviewed recently in this journal.1 Infections are transmitted by the cat flea, which is also the reservoir host of R. felis. In a preliminary study in 2004, 10% of C. felis collected from dogs and cats in Palmerston North contained DNA of R. felis.2 We have now found DNA of R. felis in cat fleas from each of three other sites sampled, and the overall prevalence is 15% (32/213). While flea-borne spotted fever has yet to be reported in New Zealand, our study shows the aetiological agent is widely distributed and common in cat fleas in the country.
Bartonella henselae and B. clarridgeiae are also emerging human pathogens transmitted by C. felis.4,5 Infections can result in a wide variety of clinical syndromes which have been reviewed recently.1 In New Zealand, cat scratch disease,1 neuroretinitis and encephalopathy6,7 occur; and a preliminary study in Palmerston North revealed DNA of B. henselae and B. clarridgeiae in 3% and 1% of the C. felis studied, respectively.2
We have now found DNA of B. henselae in 11% of the fleas from two of the three additional sites we surveyed. Similarly, we found B. clarridgeiae in cat fleas (7%) from one of the three new sites we sampled, thus indicating both organisms probably occur widely in New Zealand.
Most New Zealand households have cats and dogs as companion animals, and fleas are very common ectoparasites on these animals. Although cat fleas prefer to feed on pets, they have a wide host range and will readily feed on people.8 With the high prevalences of R. felis, B. henselae and B. clarridgeiae in cat fleas and their wide distribution in New Zealand, it would seem likely that people are not uncommonly infected.
Of note is our finding that DNA of more than one organism occurred in 10 out of 22 PCR-positive fleas, thus indicating that multiple infections may be acquired from a single flea. Diagnosing single and multiple infections is often not easy as symptoms are generally non-specific. Our study also shows that health workers should have a high index of suspicion of infections in patients with a history of ‘flea-bites.’
Author information: Patrick Kelly, Professor, Ross University School of Veterinary Medicine, Basseterre, St Kitts, West Indies; Jean-Marc Rolain, Professor, Unité des Rickettsies, CNRS UMR 6020, Faculté de Médecine, Marseille, France; Didier Raoult, Professor, Unité des Rickettsies, CNRS UMR 6020, Faculté de Médecine, Marseille, France
Correspondence: Patrick Kelly, Ross University School of Veterinary Medicine, PO Box 334, Basseterre, St Kitts, West Indies. Fax: (869) 465 1203; email: email@example.com
Acknowledgements: We thank Steve De Grey, Christine Mander, and Julian Shorten for providing flea specimens for our study.
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