Prirodna mješovita zaraza uzrokovana virusom influence ptica podtipa H9 i virusom zaraznog bronhitisa na farmama tovnih pilića

Although H9N2 AIV (Avian Influenza Virus) is pathotyped as a low pathogenic avian influenza virus, our extensive field experiences over the last decade show serious disease and high mortality in broiler chicken associated with this subtype in many regions of Iran. One of the possible explanations for such high mortality and great economic losses could be mixed infection with other respiratory pathogens such as infectious bronchitis virus (IBV). This investigation was conducted to study the natural co-infections of H9N2 AIV and infectious bronchitis viruses in broiler chicken flocks in Fars province, Iran. Tracheal samples were taken from chickens in 30 closely monitored broiler flocks suffering from respiratory disease with mortality higher than normal range. RT-PCR was performed using primers in order to detect the M protein and the H9 gene of avian influenza A. The multiplex nested RT-PCR was also performed to detect Massachusetts, 793B (4/91) and D274 serotypes of IBV in the samples. In this study, AIV and IBV were detected in 16 (53/3%) and 12 (40%) out of 30 flocks, respectively. The tracheal samples of 11 out of 12 flocks were positive for 4/91 strain of IBV and one for Massachusetts serotype. A mixed infection of AIV (H9 subtype) and IBV (4/91 serotype) was observed in four flocks with severe lesions and 20-30% mortality. The results of this study indicate the high occurrence of natural co-infection of AIV and IBV in Iranian broiler chicken farms showing respiratory signs and they show that the mortality rate in co-infected flocks was significantly higher than others (P<0.05).Premda podtip H9N2 virusa influence ptica (VIP) po patotipu pripada slabo patogenom virusu influence ptica, terenska iskustva posljednjih desetak godina pokazala su da je pojava teške bolesti i velikog pomora tovnih pilića u mnogim dijelovima Irana vezana uz taj podtip. Jedno od mogućih objašnjenja za tako visok pomor i velike gospodarske gubitke mogla bi biti mješovita zaraza s ostalim uzročnicima dišnih bolesti kao što je virus zaraznog bronhitisa (VZB). Ovo istraživanje poduzeto je s ciljem proučavanja prirodne mješovite zaraze virusom influence ptica H9N2 i virusom zaraznog bronhitisa u tovnih pilića u pokrajini Fars u Iranu. Uzorci obriska dušnika bili su uzeti od pilića na 30 promatranih jata tovnih pilića u kojih je bila ustanovljena dišna bolest s pomorom većim od uobičajenog. Rabljen je RT-PCR s početnicama specifičnima za dokazivanje proteina M i gena za hemaglutinin H9 virusa influence ptica A. Višestruka ugniježđena RT-PCR rabljena je za dokaz serotipova Massachusetts, 793B (4/91) i D274 u pretraživanim uzorcima. VIP je bio dokazan u 16 (53/3%), a VZB u 12 (40%) od 30 pretraženih jata. Uzorci dušnika uzeti iz 11 od 12 jata bili su pozitivni za soj 4/91 VZB i jedan za serotip Massachusetts. Mješovita infekcija virusom influence ptica podtipom H9 i virusom zaraznog bronhitisa (serotip 4/91) bila je promatrana na četirima jatima ptica s teškim poremećajima i 20-30%-tnim pomorom. Rezultati ovog istraživanja govore o pojavi prirodne koinfekcije virusom influence ptica i virusom zaraznog bronhitisa u iranskih tovnih pilića koji su pokazivali dišne znakove te da je pomor u jatima s mješovitom zarazom bio značajno veći (P