Proventriculite viral transmissível em frangos de corte naturalmente infectados

Abstract

The chicken proventricular necrotic vírus (CPNV) has been studied and researches have indicating it as the etiologic agent of transmissible viral proventriculitis (TVP). The aim of this study was to investigate the occurrence of TVP (first report in Brazil), using broilers proventriculus to histopathology analysis and identification of the VP1 gene from CPNV by RT-PCR and sequencing. In the pathology department, 73 broilers from flocks of the Brazilian southeast region with history of decreased body weight and stunted growth were examined. The birds were Cobb with 25 to 36 days of age. The proventriculus were examined macroscopically and microscopically, and scores for the histological lesions were stablished. The difference in the proventicular wall thickness and body weight were also evaluated considering the pattern for Cobb 500 for body weight. Broilers from all ages had histopathologic lesions and were RT-PCR positive, however, there were higher histologic severity and incidence at 33 days of age and RT-PCR positivity in 28 days of age. There was no association between body weight by the Cobb 500 pattern, histopathology and RT-PCR when the body weight was corrected removing the flock influence. Totally, 73 proventriculus were examined macroscopically and microscopically and 67 also tested by RT-PCR. In 47,9% of the proventriculus, were observed microscopic lesions of TVP, mainly glandular epithelial necrosis, epithelial duct hyperplasia with replacement of glandular epithelium by ductal epithelium, expansion of the interstitial glandular space by inflammatory infiltrate as well as glandular ectasia. In 35,8% of the broilers the RT-PCR were positive for VP1. Only 6,8% of the broilers showed enlargement of the proventricular wall. Proventriculus with TVP histologic lesions had higher wall thickness. Nonetheless, the low percentage of proventriculus with microscopic lesions without proventriculus enlargement strengthen the hypothesis of subdiagnosed disease. The sequencing of a VP1 gene fragment from CPNV reveled genetic similarity between 87,01% and 92,68% in comparison with other sequences of this same gene reported in USA, United Kingdom and Spain. This is the first TVP report in Brazil and supports CPNV as the etiologic agent of TVP. Even so, more studies on the effects of the disease in productivity and coinfections are required to improve the comprehension of TVP.