Désirée Seger Jansson

Background: Erysipelas, caused by infection with Erysipelothrix rhusiopathiae (ER), is an emerging disease in non-cage housed laying hens. According to Swedish field experience outbreaks seem more common in older flocks and may also occur in flocks vaccinated against erysipelas. This cross-sectional study aimed to assess single-dose vaccination outcome in laying hens with respect to antibody titres to ER and to monitor selected immune parameters to identify putative risk factors for erysipelas. Blood samples were collected from laying hen flocks at 30, 50 and 75 weeks of age. At each time point, 5 unvaccinated flocks and 5 flocks that had been vaccinated against erysipelas once at placement were sampled (20 hens/flock, total n=600). Results: The results showed that the majority of hens were positive for IgY to ER and that the antibody titres were higher in older hens irrespective of vaccination status. Vaccinated hens had significantly higher IgY titres to ER compared to those of unvaccinated hens. This difference was most prominent for the youngest age category. Among the different leukocyte populations studied, blood heterophil, monocyte and γ/δTCR+ T-cell counts were significantly higher in younger hens. Also, serum MBL-levels were significantly higher in younger hens and MBL-levels were positively correlated to heterophil and monocyte counts at the individual level. Conclusions: Taken together, results indicate that ER or antigenically similar bacteria are common in the hen environment and that this exposure results in antibodies recognising ER that are present at higher levels in older laying hens. In addition, a higher general pathogen load/level of subclinical infections was indicated by altered leukogram patterns and increased MBL-levels in the youngest age category. Nonetheless, among the parameters studied we found no evidence to suggest that antibody responses to single-dose vaccination should fail or why older flocks seem more susceptible to erysipelas outbreaks.

Erysipelas is an important differential diagnosis of severe viral diseases.Most of the outbreaks occurred in organic and free-range laying hen flocks.Pre-enrichment or selective culture is useful in case of suspected co-infection.Isolates from temporally clustered outbreaks on a farm are often clonal.

Background: A growing number of people in western countries keep small chicken flocks. In Sweden, respiratory disease is a common necropsy finding in chickens from such flocks. A respiratory real-time polymerase chain reaction (PCR) panel was applied to detect infectious laryngotracheitis virus (ILTV), Avibacterium paragallinarum (A. paragallinarum) and Mycoplasma gallisepticum (M. gallisepticum) in chickens from small flocks which underwent necropsy in 2017–2019 and had respiratory lesions. Owners (N = 100) of PCR-positive flocks were invited to reply to a web-based questionnaire about husbandry, outbreak characteristics and management. Results: Response rate was 61.0%. The flocks were from 18 out of Sweden’s 21 counties indicating that respiratory infections in small chicken flocks are geographically widespread in Sweden. Among participating flocks, 77.0% were coinfected by 2–3 pathogens; 91.8% tested positive for A. paragallinarum, 57.4% for M. gallisepticum and 50.8% for ILTV. Larger flock size and mixed-species flock structure were associated with PCR detection of M. gallisepticum (P = 0.00 and P = 0.02, respectively). Up to 50% mortality was reported by 63.9% of respondents. Euthanasia of some chickens was carried out in 86.9% of the flocks as a result of the outbreaks. Full clinical recovery was reported by 39.3% of owners suggesting chronic infection is a major challenge in infected flocks. Live birds had been introduced in many flocks prior to outbreaks, which suggested these as an important source of infection. Following the outbreaks, 36.1% replaced their flocks with new birds and 9.8% ceased keeping chickens. Conclusions: This study highlights the severity of respiratory outbreaks in small non-commercial chicken flocks and points to the need for more research and veterinary assistance to prevent and manage respiratory infections in small chicken flocks.