Investigation of a type C/D botulism outbreak in free-range laying hens in France.

In 2014, a botulism outbreak in a flock of laying hens was investigated in France. In the flock of 5020 hens, clinical signs of botulism occurred at 46 weeks of age. A type C/D botulism outbreak was confirmed using the mouse lethality assay for detection of botulinum toxin in serum and a real-time PCR test to detect Clostridium botulinum in intestinal contents. The disease lasted one week with a mortality rate of 2.6% without recurrence. Botulism in laying hens has rarely been reported. Five monthly visits were made to the farm between December 2014 and May 2015 for a longitudinal study of the persistence of C. botulinum in the poultry house after the outbreak, and to assess egg contamination by C. botulinum. Several samples were collected on each visit: in the house (from the ventilation circuit, the egg circuit, water and feed, droppings) and the surrounding area. Thirty clean and 30 dirty eggs were also swabbed at each visit. In addition, 12 dirty and 12 clean eggs were collected to analyse eggshell and egg content. The samples were analysed using real-time PCR to detect type C/D C. botulinum. The bacterium was still detected in the house more than 5 months after the outbreak, mostly on the walls and in the egg circuit. Regarding egg contamination, the bacteria were detected only on the shell but not in the content of the eggs. Control measures should therefore be implemented throughout the egg production period to avoid dissemination of the bacteria, particularly during egg collection.

A bovine botulism outbreak associated with a suspected cross-contamination from a poultry farm.

In October 2014, an outbreak of botulism type D/C occurred on two cattle farms in close proximity. A poultry farm located nearby with no history of botulism had transferred poultry manure to both bovine farms before the beginning of the outbreak. Given this context, epidemiological investigation was conducted to determine if the poultry farm was a reservoir of C. botulinum type D/C and to identify the source of contamination on the cattle farms. Environmental samples were collected at three houses on the poultry farm (boot swabs from the surroundings, swabs from the ventilation system, boot swabs from the poultry litter and darkling beetles samples), and on the two cattle farms (silage samples, boot swabs from the cattle stalls, boot swabs from the cattle pasture and poultry manure samples). These samples were analyzed using real-time PCR after an enrichment step to detect C. botulinum type D/C. On the poultry farm, three boot swabs from the surroundings, two swabs from the ventilation system, one boot swab from the litter and one sample of darkling beetles were detected positive. On one cattle farm, C. botulinum type D/C was identified in a sample of silage made from grass grown on a field on which the poultry manure had previously been stored and in a boot swab from a pasture. On the other cattle farm, C. botulinum type D/C was detected in a sample of poultry manure stored on the cattle farm and in a boot swab from a pasture. This investigation shows that the healthy poultry farm might have been the reservoir of C. botulinum type D/C and that cross-contamination between poultry and cattle likely occurred, resulting in the botulism outbreak on the two cattle farms.