Isolasi, identifikasi serologis dan virulensi virus infectious laryngotracheitis (ILT) isolat mangestoni farm

WIBOWO, Michael Haryadi, Drs. B. Sardjono, MSc

2002 | Tesis | S2 Sain Veteriner

Penyakit Infectious Laryngotracheitis (ILT) merupakan salah satu penyakit ekonomi yang penting pada ayam, banyak dijumpai di lapangan tetapi belum banyak dilaporkan. Penelitian ini bertujuan untuk melakukan isolasi, identifikasi, dan karakterisasi virulensi virus ILT dari ayam yang menunjukkan gejala klinis tersifat ILT, yang terjadi di Mangestoni farm, Bantul, Jogjakarta. Isolasi, propagasi, titrasi dan uji netralisasi pada penelitian ini menggunakan telur ayam berembrio 9—11 hari dengan inokulasi pada membran korioalantois. Identifikasi serologis menggunakan uji agar gel presipitasi (AGP) dan uji netralisasi. Uji netralisasi dikerjakan secara berpasangan (homolog) dan secara silang (heterolog) kemudian ditentukan titer netralisasi menggunakan rumus Reed dan Muench. Titer netralisasi silang berguna untuk mengkaji hubungan susunan antigenik virus isolat Mangestoni farm dengan virus vaksin, menurut rumus Archetti dan Horsfall. Tahap akhir penelitian merupakan uji in vivo pada ayam petelur yang peka, serta penentuan indeks patogenisitas intratrakeal yang bermanfaat untuk mengobservasi tingkat virulensi virus isolat Mangestoni farm tersebut. Hasil penelitian ini adalah sebagai berikut: virus ILT dapat diisolasi dan dipropagasi pada membran korioalantois telur ayam berembrio 9-11 hari. Pertumbuhan virus berbentuk lest virus isolat Mangestoni farm diperoleh titer 159 • dosis infeksi-50 per ml, sedangkan titer virus vaksin aktif ILT adalah 10 dosis infeksi-50 per ml. Tahap identifikasi serologis dengan uji AGP positip terjadi garis presipitasi di antara stuntman antigen dan antibodi. Hasil perhitungan titer netralisasi dengan metode Reed dan Mtiench adalah: titer serum anti vaksin-homolog adalah 7,5; titer serum anti isolat- homolog adalah 7,1; titer serum anti vaksin-heterolog adalah 2,5 dan titer serum anti isolat-heterolog adalah 4,6. Nilai (R) menurut rumus Archetti dan Horsfall adalah 46,3. Artinya bahwa virus isolat Mangestoni farm tersebut berbeda susunan antigeniknya dengan virus vaksin. Uji netralisasi menggunakan telur ayam berembrio menghasilkan nilai R kurang dan 70. Uji tersebut dianggap kurang sensitif, karena sejauh ini belum ada laporan adanya serotipe pada virus ILT. Hasil perhitungan nilai indeks patogenisitas antra trakeal adalah 0,51. Nilai tersebut menunjukkan tingkat virulensi virus isolat Mangestoni farm termasuk dalam katagori tinggi. Berdasarkan data-data pada penelitian ini dapat disimpulkan bahwa virus isolat Mangestoni farm terbukti sebagai virus ILT dengan virulensi tinggi.

Infectious Laryngotracheitis (ILT) has been an important disease in chicken, as mostly found in the field but rarely reported. The objective of this study was to isolate, identify and characterize ILT virus (ILTV), from field cases in Mangestoni farm, Bantul, Jogjakarta. Isolation, propagation, titration and neutralization test was done by inoculation on the chorioallantoic membrane (CAM) of 9 to 11-days-old chicken embrionating egg. Mangestoni farm isolate was confirmed as ILTV by agar gel precipitation test (AGPT) and serum-neutralization test using anti-ILTV vaccine virus. Neutralization test was conducted in homologous and heterologous sera, which resulted neutralization titer. It was useful to study the relationship ( R ) between composition of virus antigenic of Mangestoni farm isolate and vaccine strain. The final stage of this research was to examine in vivo inoculation in layer birds, and to determine intratracheal pathOgenicity index (ITP1) that was useful to observe the virulence level of Mangestoni farm virus. The result on the inoculation of Mangestoni farm virus on CAM of 9 to 11-days-old embrionating chicken egg was showed plaques and intranuclear inclusion bodies specific to ILTV. Mangestoni farm virus isolate titer was 10 3'68 egg infectious dose-50 per ml. and vaccine .virus titer was 10 3'57 egg infectious dose-50 per ml. Serological identification using AGPT showed a line of precipitation between the antigen and antibody, Neutralization titer in homologous: vaccine virus-anti vaccine; Mangestoni farm isolate-anti Mangestoni farm isolate were 7,5 and 7,1 respectively. Neutralization titer in heterologous: vaccine virus-anti Mangestoni farm isollite; Mangestoni farm isolate-anti vaccine were 4,6 and 2,5 respectively. Cross neutralization test of Mangestoni farm virus and ILT vaccine virus resulted ( R ) value was 46,3. It means that the antigenic composition of isolate virus differed to that of vaccine virus. The ( R') point less than 70 was speculated due to the less of sensitivity serum-neutralization test using CAMs of chicken embryo, since there was no report of serotype in ILTV. Intratracheal pathogenicity index (ITPI) on 8-weeks-old chicken resulted ITPI of 0,51. This point considered high to the level of Mangestoni farm virus virulence. Base upon the data of this research, it was concluded that Mangestoni farm isolate was proved as a highly pathogenic ILT virus.

Kata Kunci : virus ILT isolat Mangestoni farm, sifat antigenik, virulensi, ILTV Mangestoni f mis olate, antigenic properties, virulence