Progression of Q fever and <i>Coxiella burnetii</i> shedding in milk after an outbreak of enzootic abortion in a goat herd

Abstract

two to four weeks after the second parturition, thereby possibly lowering the chance of detecting the bacteria.Thus, C burnetii could not be identified as the agent causing the reproductive failure in the second season.Human infection is commonly acquired via the inhalation of infectious aerosols produced by domestic livestock in birth or abortion products.Although the alimentary route is less common as a mode of transmission of Q fever to human beings, previous studies have reported that the ingestion of contaminated goat dairy products by people leads not only to seroconversion but also causes Q fever (Fishbein and Raoult 1992).Therefore, it is important to evaluate C burnetii shedding in milk, in order to prevent possible transmission to human beings and other animals.Milk samples taken from goats in the herd that delivered before June 10, 2002, were grouped into five pools, each containing six to nine individual milk samples.PCR analysis showed evidence of C burnetii shedding in pools 1 and 2 but not in pools 3, 4 and 5 (Table 2).Two weeks later, PCR testing of individual milk samples from goats in pools 1 and 2 showed five positive goats.During this study, it appeared that only goats that had aborted shed the bacteria in their milk.The shedding of C burnetii in the milk appeared to persist for a long period during lactation (Table 2), after which it was cleared from the milk.The goats may not excrete the pathogen in their milk at the second kidding season even if they are still serologically positive.During the early lactation period, 21 female kids were fed regularly with the bulk tank milk composed mainly of the milk from goats in pools 1 and 2, but only three of them became serologically positive (data not shown).It is therefore questionable whether Q fever can be transmitted by the ingestion of raw milk.During this investigation, it appeared that, as with sheep (Berri and others 2001, 2002), the Q fever in the goats was characterised by a long-term persistence of antibodies in the sera of infected animals.A serosurvey conducted in the goat herd in May 2003, one year after the outbreak, showed that 33 (60 per cent) of the animals were positive by ELISA.Four