A Review of Pathogen Transmission at the Backyard Chicken–Wild Bird Interface

Abstract

Habitat conversion and the expansion of domesticated, invasive species into native habitats are increasingly recognized as drivers of pathogen emergence at the agricultural-wildlife interface. Poultry agriculture is one of the largest subsets of this interface, and pathogen spillover events between backyard chickens and wild birds are becoming more commonly reported. Native wild bird species are under numerous anthropogenic pressures, but the risks of pathogen spillover from domestic chickens have been historically underappreciated as a threat to wild birds. Now that the backyard chicken industry is one of the fastest growing industries in the world, it is imperative that the principles of biosecurity, specifically bioexclusion and biocontainment, are legislated and implemented. We reviewed the literature on spillover events of pathogens historically associated with poultry into wild birds. We also reviewed the reasons for biosecurity failures in backyard flocks that lead to those spillover events and provide recommendations for current and future backyard flock owners.

A systematic review and meta-analysis on global prevalence of infectious diseases in backyard chicken in the recent two decades

“…Although high prevalence was reported for Orinithobacterium rhinotracheale (ORT − 96%), Leucocytozoan (69%) and chicken infectious anemia (CIA − 53%), the number of studies was meagre. Mycoplasma gallisepticum (MG) and Mycoplasma Synoviae (MS) are commonly found in backyard chickens and the most notable bacterial pathogens that have spread from backyard chicken to wild birds (Ayala et al, 2020). Avian in uenza (AI) was the most reported disease worldwide followed by Newcastle disease (ND) in backyard poultry in the present meta-analysis.…”

“…Earlier studies also reported 34% and 40% seropositivity in unvaccinated backyard chickens in Vietnam and Iran, respectively (Vui et al, 2002;Saadat et al, 2014). Nevertheless, backyard chicken is considered as potential source of reservoir for pathogen spill over including ND and spread to wild birds (Ayala et al, 2020).…”

Low occurrence of Salmonella spp. in wild birds from a Swiss rehabilitation centre

“…Wild birds are often suspected to be the source of a disease incursion into farm animals, although domestic and wild birds share the same environment, and both may get infected from similar environmental sources, or pathogen transmission may consist of spill‐over and spill‐back events among wildlife, livestock and humans. 29 The present study investigated wild birds as possible carriers of Salmonella as a potential hazard to livestock and humans ‐ specifically the workers of the bird rehabilitation centre. Sampling was limited to a small geographic region, due to the fact, that wild birds were not sampled in the field, but were sampled in a resource‐effective manner after admittance to a rehabilitation centre.…”

Wildlife–livestock interactions in animal production systems: what are the biosecurity and health implications?

“…In most of those cases, the disease does not cause apparent symptoms in the wildlife host but can have devastating impacts on livestock populations. Examples include wild waterfowl acting as reservoirs of highly pathogenic avian influenza viruses ( Globig et al, 2009 ), wild birds as reservoirs of Newcastle Disease viruses for domestic chickens ( Ayala et al, 2020 ), warthogs being able to act as reservoirs of ASFV, and the African buffalo that is well known as the major wild reservoir of FMDV ( Jori and Etter, 2016 ; Jori et al, 2021a ). Direct or indirect contacts of such reservoirs with susceptible livestock populations can initiate sporadic outbreaks that can develop into epidemics as disease spreads between farms.…”