Serotype variation among infectious bronchitis viral isolates taken from several areas of Java [Indonesia]

English. Infectious bronchitis (IB) is an acute highly contagious viral respiratory disease of poultry caused by virus belongs to the family of Coronaviridae. The virus consist of many serotypes with low level of cross-protectivity among serotypes. Field data showed that the outbreaks of IB were frequently reported in chicken flocks, although vaccinations against the disease have been practiced. Hence, the study on serotype relationship among isolates of the viruses is essentially required. The aim of this study was to isolate and characterize IB viruses from chicken flocks in some areas of Java. Isolation of the virus was carried out in nine-days old embrionated chicken eggs and identified by means of agar gel precipitation (AGP) tests against standard antisera to IB virus. The serotypes of the IB viral isolates were determined by cross-neutralization tests in nine days old embryonated chicken eggs using r value derived from homologous and heterologous serum titres as criteria. This study obtained 12 IB viral isolates which were identified on the basis of the ability to cause lesions in chicken embryos and positive to agar gel precipitation test against standard positive antiserum to the virus. Based on the cross-neutralization tests in embryonated chicken eggs, isolate 1.9 was formed to have relationship closed to Mass-41 serotype, while 1.2, 1.3. and 1.7 isolates were closely to the serotype of Con-46. Virus isolates (1.5, 1.14, 1.24, and 1.25) were decided to have no serotype relationships to either Mass-41 or Con-46 serotype. Since the 1.5, 1.14, 1.24 and 1.25 isolates were not neutralized by antisera against the previous identified local infectious bronchitis viral isolates, and that were considered to be distinct serotype to the previously identified local IB viral isolates

unknown. Infectious bronchitis (IB) merupakan penyakit pernapasan yang bersifat akut dan sangat menular pada ayam, disebabkan oleh virus yang termasuk ke dalam famili Coronaviridae dan mempunyai banyak serotipe dengan tingkat proteksi silang yang rendah. Kasus penyakit IB di lapangan hingga saat ini sering dilaporkan pada peternakan ayam, meskipun telah rutin dilakukan vaksinasi. Variasi serotipe virus IB di lapangan yang menyebabkan kasus belum diketahui dan penting untuk dilakukan penelitian. Penelitian ini bertujuan mengisolasi virus IB dari beberapa daerah di pulau Jawa dan mempelajari variasi serotipenya. Isolasi virus IB dilakukan pada telur ayam berembrio umur 9 hari dan diidentifikasi dengan serum standar anti-virus IB dalam uji presipitasi agar (agar gel precipitation test, AGP). Variasi serotipe dari isolat-isolat tersebut dipelajari secara uji serum netralisasi silang pada telur ayam berembrio umur 9 hari. Data hasil pemeriksaan titer reaksi netralisasi terhadap serum homolog dan heterolog dipakai sebagai dasar penentuan serotipe dianalisa menggunakan nilai r (r value). Dalam studi ini, diperoleh 12 isolat virus IB yang diidentifikasi berdasarkan kemampuannya menyebabkan lesi pada embrio ayam dan positif terhadap uji AGP. Hasil penentuan serotipe dari isolat-isolat tersebut dengan menggunakan uji netralisasi silang pada telur ayam berembrio diketahui isolat 1.9 termasuk dalam serotipe Mass-41 dan isolat 1.2, 1.3 dan 1.7 termasuk dalam serotipe Con-46. Isolat 1.5, 1.14, 1.24, dan 1,25 tidak termasuk dalam serotipe Mass-41 maupun Con-46. Karena Isolat-isolat 1.5, 1.14, 1,24, dan 1.25 tidak dinetralisasi dengan antiserum terhadap virus IB isolat lokal yang telah ada berarti serotipenya berbeda dengan virus IB isolat sebelumnya