Experimental inoculation of male rats with Coxiella burnetii: successful infection but no transmission to cage mates.
Beginning in 2007, the largest human Q fever outbreak ever described occurred in the Netherlands. Dairy goats from intensive farms were identified as the source, amplifying Coxiella burnetii during gestation and shedding large quantities during abortions. It has been postulated that wild rodents are reservoir hosts from which C. burnetii can be transmitted to domestic animals and humans. However, little is known about the infection dynamics of C. burnetii in wild rodents. The aim of this study was to investigate whether brown rats (Rattus norvegicus) can be experimentally infected with C. burnetii and whether transmission to a cage mates occurs. Fourteen male brown rats (wild type) were intratracheally or intranasally inoculated with a Dutch C. burnetii isolate obtained from a goat. At 3 days postinoculation, a contact rat was placed with each inoculated rat. The pairs were monitored using blood samples and rectal and throat swabs for 8 weeks, and after euthanasia the spleens were collected. Rats became infected by both inoculation routes, and detection of C. burnetii DNA in swabs suggests that excretion occurred. However, based on the negative spleens in PCR and the lack of seroconversion, none of the contact animals was considered infected; thus, no transmission was observed. The reproduction ratio R(0) was estimated to be 0 (95% confidence interval = 0 to 0.6), indicating that it is unlikely that rats act as reservoir host of C. burnetii through sustained transmission between male rats. Future research should focus on other transmission routes, such as vertical transmission or bacterial shedding during parturition.
National Institute for Public Health and the Environment, Centre for Infectious Disease Control, Bilthoven, Netherlands.
Marieke
M
Opsteegh
Lenny
L
Hogerwerf
Stephane
S
Nooijen
Cecile
C
Dam-Deisz
Lianne
L
de Heer
Chantal
C
Reusken
Annemarie
A
Bouma
Hendrik-Jan
HJ
Roest
Mirjam
M
Nielen
Joke
J
van der Giessen
D000818:Animals; D001769:Blood / Q000382:microbiology; D016997:Coxiella burnetii / Q000302:isolation & purification / Q000472:pathogenicity*; D004269:DNA, Bacterial / Q000302:isolation & purification; D018562:Disease Transmission, Infectious / Q000662:veterinary*; D008297:Male; D010614:Pharynx / Q000382:microbiology; D011778:Q Fever / Q000635:transmission / Q000662:veterinary*; D051381:Rats; D012007:Rectum / Q000382:microbiology; D012376:Rodent Diseases / Q000382:microbiology / Q000473:pathology* / Q000635:transmission*; D013154:Spleen / Q000382:microbiology
D004269:DNA, Bacterial