Adenoviral associated gizzard erosions: an overview and case example
Abstract
Adenoviruses are of increasing concern in both human and veterinary medicine. The effects of adenoviruses in poultry species have been well documented for many decades. Adenoviral gizzard erosion (AGE) is one such syndrome that affects chickens and is caused by members of group A of the fowl adenoviruses. Development of clinical AGE is poorly understood, but cases of this syndrome can lead to economic losses and welfare concerns in both broiler and layer populations. Clinical signs, gross post-mortem lesions and histological lesions can all be used to help identify cases of AGE in practice. This article will explore AGE in the context of clinical poultry practice, including an overview of the aetiology, transmission, clinical signs, diagnosis and control of AGE.
Adenoviruses are recognised by the poultry industry as the aetiological agent for several widespread and economically significant conditions, such as egg drop syndrome (EDS) and turkey haemorrhagic enteritis (THE). More recently, fowl adenovirus A serotype 1 (FAdV-1) has been identified as the virus most commonly associated with gizzard erosion and ulceration syndrome (GEU) and adenoviral gizzard erosion (AGE). Other FAdV strains (FAdV-8a, FAdV-8B and FAdV-11) have also been detected, albeit less frequently (Steer-Cope et al, 2017; Mase and Nakamura, 2014; Mirzazadeh et al, 2019). This article will focus on FAdV-1 as the primary aetiological agent of AGE.
Adenoviruses are medium-sized (70–100 nm), double stranded DNA viruses that do not have a capsule (Hess, 2000; The International Committee on Taxonomy of Viruses (ICTV), 2012). They are classified into five genera, two of which affect mammals (mastadenovirus) or fish (ichtadenovirus). The three genera that affect avian species include atadenovirus (which contains duck adenovirus type-1, responsible for EDS), siadenovirus (which contains turkey adenovirus A, responsible for THE) and aviadenovirus. The aviadenovirus genus currently contains nine recognised species, five of which are fowl adenoviruses (categorised A–E) and includes the strains associated with AGE (ICVT, 2012).
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