2024-07-11 15:16:16
Poultry experts from Royal GD recently published a scientific article, in collaboration with practitioners, about an outbreak of Salmonella Pullorum in a flock of 65-week-old laying hens. The case concerns a couple who had complaints about an increase in the number of people leaving. Egg production fell by 5.7% in two weeks. It was remarkable that some animals showed signs of nervousness, such as twisted necks and tremors. It is not clear what exactly is the source of this outbreak.
Pathological examination revealed abnormal organs, such as an enlarged liver and premature egg follicles. Large amounts of the bacterium Salmonella Pullorum have been cultured from various organs. In addition, GD performed blood tests with a serological test used in monitoring. At 70 weeks of age, 61% of the blood samples were positive for antibodies and at 84 weeks, 100% of the herd were positive.
The couple had been vaccinated three times during the breeding period with a live vaccine against Salmonella Enteritidis and Salmonella Typhimurium. Histological examination of organ tissue from chickens with focal neurological symptoms showed inflammation in their brains where salmonella bacteria were detected. The bacteria found showed resistance to different types of antibiotics in the antibiotic sensitivity test. This is why the initial focus was on fighting blood mites and selecting sick animals.
When this did not have sufficient effect, a live salmonella vaccine, directed at Salmonella Gallinarum, was given as an emergency vaccination. Mortality decreased five weeks later. After the outbreak appeared to be over, 40 healthy chickens from the flock were randomly examined. Ovarian abnormalities occurred in several of these, which may explain why egg production did not return properly and remained at around 65%.
It is not clear what exactly is the source of this outbreak. It is suspected that there is a relationship with leakage of rainwater into the conservatory after damage to gutters, about 2 weeks before the onset of symptoms in the herd. In addition, the company experienced a malfunction in the ventilation system a week before the outbreak. Genetic analysis confirmed the genetic relatedness of Salmonella Pullorum isolates within this outbreak and distinguished them from previous outbreaks and from strains found in recreational poultry.
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