288 Patogenesitas Virus Gumboro Isolat Lokal pada Ayam Pedaging (PATHOGENICITY OF LOCAL ISOLATES OF GUMBORO VIRUS IN BROILERS) Sutiastuti Wahyuwardani 1 , Dewi Ratih Agungpriyono 2 , Lies Parede 3 , Wasmen Manalu 4 1 Balai Besar Penelitian Veteriner, Laboratorium Patologi Jl. RE Martadinata 30, Bogor 16114. Telp 0251-86331048, Fax 0251-8336425, email : sutiastutiw@yahoo.co.id. 2 Bagian Patologi, Departemen Klinik, Reproduksi dan Patologi, Fakultas Kedokteran Hewan, Institut Pertanian Bogor 3 PT Caprifarmindo Laboratories, Cimareme, Bandung. 4 Bagian Fisiologi, Departemen Anatomi, Fisiologi dan Farmakologi, Fakultas Kedokteran Hewan, Institut Pertanian Bogor ABSTRAK Patogenesitas infeksi virus gumboro atau very virulent Infectious Bursal Disease virus (vvIBDv) isolat lokal dipelajari pada ayam pedaging, baik yang divaksinasi maupun yang tidak divaksinasi dengan vaksin komersial dan vaksin isolat lokal. Patogenesitas dipelajari berdasarkan sekuen waktu infeksi, distribusi, dan derajat lesi patologi anatomik (PA) dan lesi histopatologik (HP) pada organ pertahanan bursa fabricius, limpa, dan timus dikaitkan dengan keberadaan antigen virus gumboro pada organ tersebut. Pada tahap akut (1-3 hari pascainfeksi) ditemukan lesi PA bursa fabricius berupa hiperemi dan eksudasi pada kelompok ayam yang diinfeksi dengan vvIBDv maupun kelompok ayam yang divaksinasi kemudian ditantang dengan vvIBDv. Sementara itu, pada tahap selanjutnya (7-14 hari pascainfeksi) bursa fabricius mengalami atrofi. Lesi PA berupa hiperemi limpa dan timus, teramati pada tahap akut. Lesi HP pada jaringan intersisial menunjukkan adanya edema, hemorhagi dan infiltrasi sel heterofil dan hiperplasi jaringan fibroblast. Deplesi folikel limfoid pada bursa fabricius disebabkan oleh nekrosis sel limfoid dan apoptosis. Lapisan epitel penutup plika berlekuk-lekuk dan sel goblet mengalami metaplasi membentuk kista yang membesar dengan bertambahnya umur ayam pascainfeksi. Pada organ limpa dan timus ditemukan proliferasi sel reticuloendothelial system yang ditemukan pada tahap akut dan cenderung menurun pada tahap kronis. Sel berantigen ditemukan di bagian korteks dan medula folikel limfoid bursa fabricius pada tahap akut dan kronis pada kelompok ayam yang divaksin kemudian ditantang dengan vvIBDv. Sementara itu, pada kelompok ayam yang diinfeksi vvIBDv, antigen virus hanya terdeteksi hingga umur 7 hari pascainfeksi. Antigen virus tidak terdeteksi pada limpa dan timus. Hasil penelitian ini menunjukkan bahwa vaksinasi IBD menggunakan vaksin isolat lokal maupun vaksin komersial tidak dapat mencegah kerusakan organ bursa fabricius, limpa dan timus yang diakibatkan oleh infeksi vvIBDv isolat lokal. Kata kunci : patogenesis, imunohistokimia, Infectious Bursal Disease, organ pertahanan ABSTRACT Study of the pathogenicity of gumboro virus (very virulent Infectious Bursal Disease virus, vvIBDV) of local isolates was performed in broilers. The chickens were grouped into four: i) infected with vvIBDV; ii) vaccinated with commercial vaccine + challenge with vvIBDV; iii) vaccinated using locally produced vaccine + challenged with vvIBDV; and iv) control group (unvaccinated animals). Pathogenecity was analyzed based on the sequence of infection; the distribution and degree of gross pathology and histopathology lesions on bursa Fabricius, spleen and thymus in relation to the presence of the antigen (IBDV Ag) which was detected using immunohistochemistry technique. During the acute phase (1-3 days following the experimental infection) hyperemia and exudation on the bursa Fabricius were observed in the infected group and the two vaccinated-challenged groups. Similarly, hyperemia was also observed on the spleen and thymus. Whilst during the chronic stages (at 7 and 14 days following the experimental infection) the bursa showed atrophy. Upon histological examination, the bursa showed interstitial edema, hemorrhage, infiltration of heterophyl cells and fibroblast hyperplasia. The bursa lymphoid follicles were depleted due to cells necrosis and apoptosis. Plica epithelial layer was wrinkled and the Goblet cells metaplasia formed hyper plastic cysts. In the spleen and thymus severe reticulo endothelial cells proliferation was observed during the acute stage and tended to decline during the chronic stage. During the acute and chronic stages cells containing IBDV Ag were detected in the bursa Fabricius, distributed within the mantle zone and germinal center of lymphoid follicles in the two vaccinated-challenge groups. Whereas in the infected group, the IBDV antigen were detected up to 7 days post the infection. Nevertheless, neither IBDV antigen was detected in the spleen nor in the thymus in all the experimental groups. The results of this study clearly explained the ferocity of vvIBDV of local isolates. Keywords: pathogenicity, IBD virus, immunohistochemistry, bursa Fabricius, spleen, thymus Jurnal Veteriner Desember 2011 Vol. 12 No. 4: 288-299 ISSN : 1411 - 8327