“…Several viruses have been suggested including: an adenovirus (Kouwenhoven et al, 1978), a reovirus (Jones, 2000), infectious bronchitis virus (Yu et al, 2001), infectious bursal disease virus (IBDV) (Huff et al, 2001), and a picornavirus (Kim et al, 2015). A few years ago, a new birnavirus, named chicken proventricular necrosis virus (CPNV), was detected in naturally and experimentally reproduced TVP-affected cases in the USA and proposed to be its cause (Guy et al, 2011a(Guy et al, , 2011b. CPNV has subsequently been detected in a few other studies in TVP-affected broiler chickens in France and the USA (Marguerie et al, 2011;Noiva et al, 2015).…”