A systematic review of the aetiology and presentation of stunting diseases in broiler chickens

The wide range of interchangeable terms used to describe stunting diseases reflects persistent confusion in the field. Many stunting syndromes share overlapping features, including malabsorption-associated conditions such as runting–stunting syndrome (RSS) and maldigestion-associated conditions such as transmissible viral proventriculitis (TVP). In this systematic review, we analysed published field and in vivo studies of stunting diseases and categorised them into four groups based on key diagnostic criteria. Although reduced growth is a common hallmark across syndromes, important differences exist. RSS typically occurs during the first to third week of age, whereas TVP and mixed stunting cases peak later, between the third and fifth weeks. Classical RSS is primarily linked to malabsorption resulting from intestinal damage, such as cystic enteritis. In contrast, TVP is characterised by maldigestion associated with distinct proventricular lesions and the absence of intestinal pathology, suggesting fundamentally different disease origins. Notably, concurrent lesions in both the proventriculus and small intestine are frequently observed in mixed stunted cases, particularly in co-infected birds. We therefore hypothesise that viral concurrent or co-infections play a central role in stunting diseases by driving overlapping clinical signs and lesions across gastrointestinal compartments. This systematic review clarifies key sources of confusion surrounding stunting diseases by distinguishing their age of onset, clinical presentation, histopathological features, and aetiology.