Investigation of an unusual cluster of illness among staff at a wildlife rescue centre

When two previously fit and well staff from a wildlife rescue centre were hospitalised in early September 2018 with severe pneumonia and meningitis symptoms, the Health Protection Team began an investigation. Possible diagnoses included influenza and legionella, although it was not flu season, and initial testing proved negative. There were reports of other staff illness over the preceding weeks. The centre had accepted a wide range species over the Summer, including high numbers of gulls and pigeons, and an outbreak of psittacosis was suspected; the patients responded rapidly to doxycycline. An incident management team was rapidly convened to investigate and determine control measures. A testing algorithm was developed: including for Influenza A&B, Urine legionella & pneumococcal antigen; reference laboratory serology testing and real-time PCR for Chlamydia.psittaci; and pan-corona viruses. Case finding was conducted by telephone interviews and a select-survey of all 55 staff gained 46 responses. A series of site visits examined working practices at the site. Avian and environmental sampling was undertaken. A total of 22 staff met the agreed case definition for psittacosis, five of whom were later confirmed. Clinical features ranged from mild to severe. The onset dates of illness ranged from July to September. There was no evidence of person-to-person transmission. Analysis did not show a clear correlation between PPE use and illness. Clinical, microbiological, environmental, veterinary, and epidemiological evidence indicated zoonotic transmission of psittacosis. Variable compliance with PPE, hygiene when handling birds, and disinfection had likely contributed via aerosolization of dust. This was likely exacerbated by very high bird stocks and unusually warm weather conditions. Comprehensive recommendations were made to reduce the chances of future outbreaks, which are generalisable to other countries. KEY MESSAGES: • This was one of the largest clusters of human psittacosis described in a workplace in England. • Biosecurity in animal rescue centres is crucial to limit the chance of psittacosis and other zoonoses.