Coxiella burnetii Shedding Routes and Antibody Response after Outbreaks of Q Fever-Induced Abortion in Dairy Goat Herds

Abstract

Q fever is a zoonosis caused by Coxiella burnetii, a bacterium largely carried by ruminants and shed into milk, vaginal mucus, and feces. The main potential hazard to humans and animals is due to shedding of bacteria that can then persist in the environment and be aerosolized. The purpose of this study was to evaluate shedding after an outbreak of Q fever abortion in goat herds and to assess the relationship with the occurrence of abortions and antibody responses. Aborting and nonaborting goats were monitored by PCR for C. burnetii shedding 15 and 30 days after the abortion episodes. PCR analysis of all samples showed that 70% (n ‫؍‬ 50) of the aborting and 53% (n ‫؍‬ 70) of the nonaborting goats were positive. C. burnetii was shed into vaginal mucus, feces, and milk of 44%, 21%, and 38%, respectively, of goats that aborted and 27%, 20%, and 31%, respectively, of goats that delivered normally. Statistical comparison of these shedding results did not reveal any difference between these two groups. PCR results obtained for the vaginal and fecal routes were concordant in 81% of cases, whereas those for milk correlated with only 49% of cases with either vaginal or fecal shedding status. Serological analysis, using enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence assay (IFA), and complement fixation tests, showed that at least 24% of the seronegative goats shed bacteria. Positive vaginal and fecal shedding, unlike positive milk shedding, was observed more often in animals that were weakly positive or negative by ELISA or IFA. Two opposite shedding trends were thus apparent for the milk and vaginal-fecal routes. Moreover, this study showed that a nonnegligible proportion of seronegative animals that delivered normally could excrete C. burnetii.

Circulation of Coxiella burnetii in a Naturally Infected Flock of Dairy Sheep: Shedding Dynamics, Environmental Contamination, and Genotype Diversity

“…Bacterial burdens in vaginal mucus and, to a lesser extent, in feces were also higher. These results are consistent with those previously obtained for sheep (17,20,21,35), goats (19,27,36), and cows (18). Low levels of C. burnetii DNA were also detected in milk (C T Ͼ30.5), which fits with the prevailing opinion among experts that sheep shed lower burdens of C. burnetii in milk than do cows and goats (3).…”

“…Low levels of C. burnetii DNA were also detected in milk (C T Ͼ30.5), which fits with the prevailing opinion among experts that sheep shed lower burdens of C. burnetii in milk than do cows and goats (3). We also confirmed that vaginal and fecal shedding durations varied among ewes (17,20) and that shedding may be discontinuous, as in goats (19,23,25,26,37) and cows (18,24). The latter finding suggests that the number of C. burnetii shedders may be underestimated if only one shedding route is investigated and/or if the animals are not repeatedly tested over time.…”

“…On livestock farms, C. burnetii DNA has been found in various environmental matrices, such as dust (11-13) and aerosols (14-16). However, studies that examine the relationship between environmental contamination levels and the clinical status and shedding dynamics of ruminant herds are lacking.Although it is known that C. burnetii may be shed by infected domestic ruminants via birth products, vaginal secretions, feces, and milk (1,(17)(18)(19)(20)(21)(22), studies looking at the duration of individual shedding and the relative importance of the different shedding routes have yielded inconsistent results (3, 17-19, 21, 23). However, longitudinal follow-up studies performed on cattle (18, 24) and goat (21, 25-27) farms have been particularly valuable in providing descriptive data on individual shedding patterns and revealing the factors that may affect shedding dynamics.…”

“…Although it is known that C. burnetii may be shed by infected domestic ruminants via birth products, vaginal secretions, feces, and milk (1,(17)(18)(19)(20)(21)(22), studies looking at the duration of individual shedding and the relative importance of the different shedding routes have yielded inconsistent results (3, 17-19, 21, 23). However, longitudinal follow-up studies performed on cattle (18,24) and goat (21,(25)(26)(27) farms have been particularly valuable in providing descriptive data on individual shedding patterns and revealing the factors that may affect shedding dynamics.…”

Prevalence Study of <i>Coxiella burnetii</i> in Aborted Ovine and Caprine Fetuses by Evaluation of Nested and Real-Time PCR Assays

“…The diagnosis of C. burnetii by serological responses, which can be unspecific and unsensitive due to cross-reaction (Rousset et al, 2009) or subsensitive reactionsin samples from areas with a low or subclinical prevalence of Coxiellosis. In addition serological diagnostic methods are retrospective due to the timeframe for sero-conversion (3-4 weeks post infection), rendering them useless for timely treatment.…”