Belgian bulk tank milk surveillance program reveals the impact of a continuous vaccination protocol for small ruminants against Coxiella burnetii

Abstract

Endemic Q fever in small ruminants remains an ongoing challenge for veterinary and human public health agencies. Though surveillance programs are implemented in Belgium, infection patterns and vaccination profiles, driving variables, as well as geographical clustering were not presented until now. Based on data from a decade of bulk tank milk analysis between 2009 and 2019, shedding in dairy goat herds declined from 16% (8/50) to 6% (10/162), whereas seroprevalence remained between 32% and 40%. Merely up to two shedding dairy sheep flocks were detected until 2019; seroprevalence peaked in 2017 (43%, 12/28) and declined thereafter. The number of animals in the holding influenced significantly (p = .048) the likelihood of shedding, whereas other established risk factors such as uncovered manure, high abortion rates and diversified farm structure could not be confirmed to significantly affect infection on Belgian herd level. Intermittent, incomplete and unsynchronized vaccinated herds shed Coxiella burnetii significantly more often and longer (p < .001) than continuously, complete and synchronized vaccinated herds. Spatial analyses revealed restricted but matching, homogenous clusters with ≤35 km diameter, concentrated in the coastal region close to the border to the Netherlands from 2009 to 2012, and broadened, heterogeneous clusters with ≥45 km diameter between 2014 and 2016 spreading south‐west. Though the majority of human cases was notified in this region, the animal clusters could not be allied with Q fever cases. The impact of environmental factors as well as the role of wildlife, rodents and ticks on the transmission between flocks and to humans remains to be elucidated to harness additional epidemiological drivers of Q fever in Belgium. In conclusion, attempts to reduce the burden of Q fever in Belgium should particularly focus on the timely, complete and synchronized vaccination of flocks, including the breeding sire, and particularity in high‐risk areas.

Surveillance of Coxiella burnetii Shedding in Three Naturally Infected Dairy Goat Herds after Vaccination, Focusing on Bulk Tank Milk and Dust Swabs

“…Bulk tank milk (BTM) samples have been successfully used to monitor the Q fever status of dairy goat herds [ 33 , 34 , 35 ]. Analyzing caprine BTM samples for C. burnetii by PCR revealed a wide range of detection rates in several countries, such as 16% in Belgium [ 35 ], 32.9% in the Netherlands [ 34 ], 54% in Poland [ 36 ], and 16.1% in Iran [ 37 ].…”

“…Bulk tank milk (BTM) samples have been successfully used to monitor the Q fever status of dairy goat herds [ 33 , 34 , 35 ]. Analyzing caprine BTM samples for C. burnetii by PCR revealed a wide range of detection rates in several countries, such as 16% in Belgium [ 35 ], 32.9% in the Netherlands [ 34 ], 54% in Poland [ 36 ], and 16.1% in Iran [ 37 ]. However, this method is limited to dairy animals, and there is a growing interest to examine dust samples from animal facilities to detect C. burnetii on ruminant farms [ 3 , 6 , 38 , 39 , 40 , 41 ].…”

The Tick-Borne Pathogens: An Overview of China’s Situation

“…Q fever in mammals is generally asymptomatic; however, pregnant livestock will manifest reproductive disorders, such as abortion, stillbirth, and mastitis. Large amounts of pathogens are not only shed during abortion or normal parturition, but also through milk, vaginal mucus, and feces for months [ 57 ]. The routes of human infection include direct contact with shedders, eating raw meat and milk of infected ruminants, or inhalation of contaminated aerosols [ 58 ].…”

Adjuvanting Coxevac® with QuilA® skews Coxiella burnetii-induced inflammatory responses towards a sustained Th1-CD8+-mediated activation and increases protection in an experimental goat model

“…Effective action of Coxevac® is usually achieved following compliant multiannual vaccination protocols, but filed data indicated that protective antibody levels are not maintained long enough to establish standardized yearly vaccination programs 19 . Given that Coxevac® does not contain an adjuvant and the need to increase its efficacy, we designed an improved formulation of Coxevac® by including the readyto-use QuilA® adjuvant in the emulsion.…”

“…Although several studies demonstrated its efficacy in reducing clinical signs (abortions) and bacterial shedding [13][14][15][16] , this vaccine does not prevent infection 13,15 nor clears the infection in infected animals 17,18 . In addition, field data indicated that antibody levels decrease after 9 months below protective levels, hampering targeted annual vaccination programs on herd level 19 . If the critical level of protective immunity is not maintained long enough at the individual or herd level, recrudescence will likely take place 19,20 .…”