A two-year prospective study of small poultry flocks in Ontario, Canada, part 2: causes of morbidity and mortality:

Non-commercial poultry flocks (referred to as “small flocks”) have become increasingly popular in Canada. Despite this popularity, little is known about the main causes of morbidity and mortality (health status) in these flocks. We assessed the baseline prevalence of infectious and non-infectious diseases among Ontario’s small poultry flocks by conducting a prospective surveillance study over a 2-y period. With the owner’s consent, for each bird (n = 245) submitted to the Animal Health Laboratory, we performed a postmortem examination, including ancillary tests to reach a diagnosis. Infectious diseases were the most common primary cause of clinical signs or death (62%), with multifactorial respiratory diseases (21%) and Marek’s disease (11%) being most frequent. Multifactorial respiratory diseases were commonly caused by coinfection with bacteria (e.g., Mycoplasma gallisepticum and M. synoviae, Escherichia coli, Avibacterium spp.) and viruses, such as infectious bronchitis and infectious laryngotracheitis...