Q fever abortion diagnosed at TVMDL
By Andrés de la Concha-Bermejillo, DVM, PhD
With over 800,000 tests run annually, TVMDL encounters many challenging cases. Our case study series will highlight these interesting cases to increase awareness among veterinary and diagnostic communities.
The Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) recently diagnosed Q (Query) fever in a 3-week, pre-term aborted goat fetus. The clinical history indicated that four nannies on the same premises aborted during the course of 48 hours. All aborted nannies showed no other clinical signs of disease. During an external examination of one of the fetuses, no significant lesions were observed. The placenta was severely soiled with dirt, hay, and fecal material. Internally, there was diffuse, complete atelectasis indicating that the fetus was dead at the time of parturition. The pleura on the dorsal aspect of the right caudal lung lobe contained numerous petechiae. There was no evidence of fetal malformation.
The placenta was submitted to the molecular section to test for Coxiella burnetii by qPCR. Other fresh and formalin fixed tissues collected at necropsy were maintained in containment pending the Q fever qPCR results, which in this case turned out to be positive.
Q fever is a highly infectious zoonotic disease. In the United States, C. burnetii is classified as a category B potential aerosolized biological weapon. It is included on the federal list of Select Agents as a potential bioterroism agent and is therefore subject to strict controls. Current policy requires all small ruminant abortions submitted to TVMDL be tested for Q fever by qPCR before any other test can be performed. If C. burnetiiq PCR results are positive, Select Agent regulations require that all fresh and fixed tissues must be destroyed properly and no other testing can be performed.
Coxiella burnetii primarily affects goats, sheep, cattle, and humans. Dogs and cats can be infected by ingesting placentas and tissues of infected aborted fetuses. Other species less commonly affected include rabbits, a variety of wild and domestic mammals, and birds.
C. burnetii is extremely stable in the environment and can be transmitted to other animals via aerosol or contaminated dust and direct contact with placental tissues and parturient fluids, feces, or urine of infected animals. Fomites such as wool,bedding,clothing, ingestion of parturient material, contaminated water,or raw milk may also play a role in transmission.
Most C.burnetii infections in ruminants are asymptomatic, but outbreaks of late term abortions, stillbirths,retained placentas, infertility, or the birth of weak newborns are common in small ruminants. Affected adult ruminants are usually asymptomatic. Abortions typically occur over a 2-4 week period. Between 5 and 50% and in some cases up to 90% of the pregnant ewes or goats may abort. Some infected animals can become carriers and the infection may be reactivated in subsequent pregnancies resulting in shedding of the organism even though pregnancy may result in normal viable offspring. In cattle, infertility, sporadic abortion, and low birth weights are seen.
In humans, Q fever is considered an occupational hazard with the majority of infections occurring in livestock workers,veterinarians, and personnel of animal research facilities.
Gross lesions often consist of placentitis. The intercotyledonary areas of the placenta (chorioallantoic membrane) are thickened with a leathery appearance and are covered with white-yellow or brownish-red exudate. Cotyledons are swollen and exhibit a yellow or brownish-red discoloration. In the majority of cases, Q fever-aborted fetuses do not show gross lesions and can be autolyzed or fresh.
Currently, the preferred method to establish the diagnosis of Q fever in aborted fetuses is done by demonstration of C. burnetii DNA within the affected placenta or other tissues using the polymerase chain reaction (PCR). It is highly recommended that aborted fetuses and placentas are sent to the diagnostic laboratory double-bagged and chilled, rather than performing necropsies at the clinic or farm to reduce environmental contamination and potential human and animal exposure.
Serological tests in a flock/herd are good indicators of previous exposure, but provide no information on the infectious status of individual animals.
To learn more about this case, contact Dr. de la Concha, Veterinary Pathologist, at 979.845.3414. For more information about TVMDL’s test offerings, visit tvmdl.tamu.edu
de la Concha-Bermejillo, A. Q Fever (Coxiellosis). In: Blackwell’s Five-minute Veterinary Consult: Ruminant 2ndedition. C.C.L. Chase, K.A. Lutz, E.C.McKenzie,and A. Tibary eds. Wiley-Blackwell Ames, Iowa. Pp. 685-687, 2017.