Avian Ganglioneuritis in Clinical Practice

Avian Bornaviral Ganglioneuritis: Current Debates and Unanswered Questions

“…Gastrointestinal (GI) signs may involve excessive regurgitation, poor appetite, crop impaction, weight loss, and passage of undigested food in the feces. ese symptoms may be related to pathology of the vagus nerve that controls the upper part of the digestive tract, including the crop, proventriculus, and ventriculus, resulting in reduced gastrointestinal motility [1]. Some researchers have also suggested that the interstitial cells of Cajal that control muscular movements in the digestive system are likely to be involved as the target of avian bornaviruses [2].…”

“…Bornaviruses can spread through other parts of a bird's nervous system and cause shaking of the head, abnormal and uncoordinated movements, difficulty balancing, tremors, paralysis, self-mutilation, aggression, and seizures. ere may also be heart arrhythmias, blindness, and cognitive deficits, depending on the various locations of neurological damage [1,4]. A survey of 32 bornavirus-positive birds from Brazilian clinics and breeding facilities, including several confiscated from illegal trade, revealed that 66% of afflicted birds showed CNS symptoms, while 22% had GI signs, and 9% of the birds died [5].…”

“…e impact of bornavirus infection appears to depend on the body's immunological responses because the presence of CD3+ host T cells in the brain has been shown to be strongly associated with the onset of neurological symptoms [11]. Furthermore, research has shown that the amount of virus detected in tissues after death is not associated with severity of clinical symptoms, supporting the conclusion that the body's immune response is a causal factor in the disease, although the specific pathogenic mechanisms are currently under debate by researchers [1,2].…”

“…Another important debate about avian ganglioneuritis involves the pathogenic mechanisms for this disease. It is generally believed that avian bornaviruses affect the body's immunological response because CD8+ host T cells in the brain are strongly associated with the onset of neurological symptoms and the amount of virus detected in tissues after death is not associated with severity of clinical symptoms [1]. Specifically, CD8+ T cells cause direct damage to the ganglia and neurons, combined with CD4 T-cell recruitment of macrophages, ultimately resulting in antibody-mediated phagocytosis of axons [1].…”

“…It is generally believed that avian bornaviruses affect the body's immunological response because CD8+ host T cells in the brain are strongly associated with the onset of neurological symptoms and the amount of virus detected in tissues after death is not associated with severity of clinical symptoms [1]. Specifically, CD8+ T cells cause direct damage to the ganglia and neurons, combined with CD4 T-cell recruitment of macrophages, ultimately resulting in antibody-mediated phagocytosis of axons [1]. Less direct mechanisms including loss of protective myelin, dysfunction of mitochondria, and release of nitric oxide or glutamate may contribute to axonal damage [1].…”