Co-infection of Infectious Myonecrosis Virus (IMNV) and Vibrio harveyi in Pacific White Shrimp (Litopenaeus vannamei)

Abstract

L. vannamei production in Indonesia was growing intensively. In 2006, IMN (infectious myonecrosis) disease was confirmed spread to Indonesia shrimp farm and declined shrimp production. The study was conducted to investigate effect of dose of V. harveyi on co-infection with IMNV in L. vannamei as well as development of viral infection. Shrimps juvenile were oral infected with IMNV infected shrimps 10 % feeding rate during 3 days and co-infected with 106, 107 and 108 cfu/ml V. harveyi. Mortality rate was 0 % in control and single infection of V. harveyi except 108 cfu/ml treatment. Mortality pattern demonstrated on co-infection was faster and higher than single IMNV infection in 14 days observation. The density of green colony Vibrio in hepatopancreas of co-infected shrimps collected in 2, 4, 6, 8 and 10 days post infection were higher than V. harveyi single infected (significantly in 10 days post infection). There were no difference of IMN disease development between co-infection and IMNV single infection. It was confirmed by visual gross sign appeared, tissue and lymphoid organ histophatology, organ abnormality, and PCR test. In conclusion, IMN disease caused higher and faster mortality on co-infection with V. harveyi, but not affect to IMN disease development.

Penyakit IMN (infectious myonecrosis) adalah penyakit terkini yang menyerang udang Litopenaeus vannamei. Saat ini mortalitas udang akibat penyakit IMN bisa mencapai 70% dan udang yang mengalami kematian tidak menampakkan gejala klinis tingkat lanjut, yaitu sebagian abdomen sampai ekor menjadi merah. Konsep ko-infeksi belum banyak dipelajari di bidang akuakultur, padahal banyak kasus patogen tidak hanya menyerang sebagai infeksi tunggal. Penelitian ini dilakukan untuk menginvestigasi dampak ko-infeksi infectious myonecrosis virus (IMNV) dan Vibrio harveyi pada udang L. vannamei, serta mengamati perkembangan gejala klinis penyakit IMN yang terjadi. Penelitian ini dilakukan pada Januari-Mei 2011 di Laboratorium Kesehatan Ikan, Departemen Budidaya Perairan, Fakultas Perikanan dan Ilmu Kelautan, Institut Pertanian Bogor. Udang uji diperoleh dengan memelihara benih udang vaname SPF (specific pathogen free) sejak PL (post larvae) 10 hingga berukuran minimal 2 gram. Stok virus adalah udang hidup yang diinfeksi virus IMNV, dan digunakan sebagai sumber infeksi setelah menampakkan symptom penyakit IMN dan diverifikasi dengan PCR (polymerase chain reaction). Sedangkan isolat V. harveyi merupakan koleksi Laboratorium Kesehatan Ikan, Departemen Budidaya Perairan, Institut Pertanian Bogor.