Abstract
In 2007, Q fever started to become a major public health problem in the Netherlands, with small ruminants as most probable source. In order to reduce environmental contamination, control measures for manure were implemented because of the assumption that manure was highly contaminated with Coxiella burnetii. The aims of this study were 1) to clarify the role of C. burnetii contaminated manure from dairy goat farms in the transmission of C. burnetii to humans, 2) to assess the impact of manure storage on temperature profiles in dunghills, and 3) to calculate the decimal reduction time of the Nine Mile RSA 493 reference strain of C. burnetii under experimental conditions in different matrices. For these purposes, records on distribution of manure from case and control herds were mapped and a potential relation to incidences of human Q fever was investigated. Additionally, temperatures in two dunghills were measured and related to heat resistance of C. burnetii. Results of negative binomial regression showed no significant association between the incidence of human Q fever cases and the source of manure. Temperature measurements in the core and shell of dunghills on two farms were above 40°C for at least ten consecutive days which would result in a strong reduction of C. burnetii over time. Our findings indicate that there is no relationship between incidence of human Q fever and land applied manure from dairy goat farms with an abortion wave caused by C. burnetii. Temperature measurements in dunghills on two farms with C. burnetii shedding dairy goat herds further support the very limited role of goat manure as a transmission route during the Dutch human Q fever outbreak. It is very likely that the composting process within a dunghill will result in a clear reduction in the number of viable C. burnetii.
Highlights
Qfever is a zoonotic disease caused by the obligate intracellular bacterium Coxiella burnetii
These control farms were defined as dairy goat farms without notified abortions caused by C. burnetii, which never had a positive PCR result in the mandatory bulk tank milk (BTM) surveillance program between its start in 2009 up to and including 2014, and which were BTM ELISA negative in 2008, before goats on these farms were vaccinated against C. burnetii [17]
C. burnetii induced abortion waves were confirmed on twelve dairy goat farms
Summary
Qfever is a zoonotic disease caused by the obligate intracellular bacterium Coxiella burnetii. The bacterium is shed in urine, milk, faeces, and is found in high numbers in birth products of infected animals, causing environmental contamination. Q fever started to become a major public health problem with 168, 1,000, and 2,357 notified human cases in 2007, 2008 and 2009, respectively [7]. These unprecedented annual outbreaks are largely explained by exposure of the general population to airborne C. burnetii contaminated dust particles originating from infected dairy goat herds with abortion storms [5, 8,9,10,11,12]. Environmental contamination, control measures were implemented, such as compulsory vaccination of all dairy sheep and dairy goats, and measures to reduce potential transmission, for instance by prohibiting removal of manure from stables within thirty days after lambing, and compulsory covering of manure after removal from the stable to reduce potential transmission [13,14]
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