Estimation of the frequency of Q fever in sheep, goat and cattle herds in France: results of a 3-year study of the seroprevalence of Q fever and excretion level of Coxiella burnetii in abortive episodes

Abstract

A study was carried out, from 2012 to 2015, in 10 French départements to estimate the serological prevalence of Q fever and the frequency of abortive episodes potentially related to Coxiella burnetii in a large sample of cattle, sheep and goat herds. The serological survey covered 731 cattle, 522 sheep and 349 goat herds, randomly sampled. The frequency of abortive episodes potentially related to C. burnetii was estimated by investigating series of abortions in 2695 cattle, 658 sheep and 105 goat herds using quantitative polymerase chain reaction analyses and complementary serological results when needed. The average between-herd seroprevalence was significantly lower for cattle (36·0%) than for sheep (55·7%) and goats (61·0%) and significantly higher for dairy herds (64·9% for cattle and 75·6% for sheep) than for meat herds (18·9% for cattle and 39·8% for sheep). Within-herd seroprevalence was also significantly higher for goats (41·5%) than for cattle (22·2%) and sheep (25·7%). During the study period, we estimated that 2·7% (n = 90), 6·2% (n = 48) and 16·7% (n = 19) of the abortive episodes investigated could be 'potentially related to C. burnetii'in cattle, sheep and goat herds, respectively. Overall, strong variability was observed between départements and species, suggesting that risk factors such as herd density and farming practices play a role in disease transmission and maintenance.

Keywords: Coxiella; Abortions; ELISA; Q fever; qPCR; seroprevalence; surveillance; zoonoses.

Fig. 1.

(a) Geographical location of départements included in the study, (b) departmental distribution of the proportion (mean = 0·37) of farmers having notified abortions in 2014 in dairy and (c) departmental distribution of the proportion (mean = 0·16) of farmers having notified abortions in 2014 in beef cattle farms (Data: Perrin et al., 2015).

Fig. 2.

Interpretation scheme of qPCR and ELISA results for the abortion surveillance scheme. (A) Herd classified as ‘suspected for Q fever with high excretion level’ and abortive episode potentially related to C. burnetii; (B) herd classified as ‘suspected for Q fever with low excretion level or inconclusive results’ and abortive episode inconclusive; (C) herd classified as ‘not-suspected for Q fever’ and abortive episode not attributed to C. burnetii.

Fig. 3.

Average proportions of cows over 5-years-old sampled in dairy and beef herds per department.

Fig. 4.

Average between-herd seroprevalence (%) and 95% confidence interval (vertical black line) per species and département; (a) for all production types, (b) per production type for cattle herds (b1), and sheep flocks (b2). Mix type corresponds to herds in which dairy and beef animals are mixed.

Fig. 5.

Distribution (boxplot) of the within-herd seroprevalence per species and département.

Fig. 6.

Quantitative results for (a) individual and (b) pooled qPCR analyses per species (from endocervical or vaginal swabs). LD: limit of detection (2 × 10² or 3 × 10² bacteria per swab, depending on the method used); LQ: limit of quantification (2 × 10² or 5 × 10² bacteria per swab, depending on the method used); LQ_max: maximum limit of quantification (2 × 10⁶ or 4 × 10⁶ bacteria per swab, depending on the method used).

Fig. 7.

Proportion and number (in bolded numbers) of herds ‘suspected for Q fever with high excretion level’ per département and species.