Prevalensi dan perubahan histopatologik infectious myonecrosis (IMN) pada udang putih (Litopenaeus Vannamei) di jawa Timur

NURAINI, Yani Lestari, Dr. drh. Asmarani Kusumawati, MP

2008 | Tesis | S2 Sain Veteriner

Infectious myonecrosis (IMN) di Indonesia diketahui sudah menyerang udang putih di kabupaten Situbondo pada bulan Mei tahun 2006 dengan prevalensi 11,11 %. Penelitian ini bertujuan untuk mengetahui perkembangan prevalensi IMN pada udang putih di Jawa Timur dan perubahan histopatologi IMN secara invivo. Pengambilan sampel prevalensi IMN dilakukan di kabupaten Situbondo, Banyuwangi, Jember, Probolinggo, Gresik, Lamongan dan Tuban dengan menggunakan metode Sampling Tahapan Ganda. Jumlah sampel di kabupaten dibagi dalam tiap kecamatan dengan perhitungan secara proporsional. Masing-masing petak sampel udang diambil secara bias sampling kemudian dianalisa RT-PCR dengan menggunakan IQ 2000 IMNV. Sampel yang diambil diamati abnormalitas dan gejala klinisnya. Uji patogenesitas IMNV pada udang putih secara invivo, empat puluh empat ekor udang sehat yang tidak terdeteksi TSV, WSSV, IHHNV dan IMNV dibagi dalam 2 kelompok. Infeksi buatan dilakukan dengan cara penyuntikan 0,01 ml/gram berat udang dengan hasil ekstraksi virus dari udang yang positif terinfeksi IMNV ke udang yang sehat pada ruas ke-3 abdomen. Satu kelompok udang diinjeksi dengan 2 % larutan NaCl. Udang dipelihara selama 15 hari dan setiap hari dilakukan penggantian air sebanyak 50 % dan udang diberi pakan sebanyak 3 % berat badan/hari. Pengamatan berupa gejala klinis dan mortalitas udang dilakukan setiap hari. Udang yang sakit diambil insang dan atau pleopode untuk dilakukan uji PCR. Ruas ke-5, ke-6 abdomen dan cephalohorax dipotong secara longitudinal dan direndam dengan larutan fiksasi Davidson untuk diproses histopatologi. Analisa data dihitung prosentase prevalensi IMN di lapangan dan persentase daya kelangsungan hidup udang. Patogenesitas IMNV pada udang putih didasarkan hasil pemeriksaan RT-PCR, gejala klinis, perubahan histopatologi dan dianalisa secara diskriptif. Hasil penelitian menunjukkan prevalensi IMN di Banyuwangi 23,07 %, Situbondo 20,51 %, Jember 0 %, Probolinggo 23,53 % dan di kabupaten Tuban, Gresik, Lamongan sebesar 3,7 %. Kematian 100 % terjadi pada hari ke-9 setelah infeksi. Gejala klinis muncul pada hari ke-3 yaitu abdomen ruas ke-6 berwarna putih, abdomen dan ekor berwarna oranye pada hari ke-7. Lesi patologi berupa nekrosis koagulasi dan radang pada otot. Radang juga dijumpai pada jaringan interstitial. Badan inklusi yang berwarna basofilik pucat sampai biru tua dijumpai pada otot, usus, hati dan hepatopankreas. Semakin berat infeksi virus akan menyebabkan perubahan patologi lebih berat.

Infectious myonecrosis (IMN) has infected white shrimp in Situbondo, Indonesia at May 2006 with prevalence of 11.11%. This study aimed to know the prevalence development of infectious myonecrosis in white shrimp in East Java and histopathological changes of disease by in vivo. Sampling for prevalence study using Multiple Level Sampling method was done in Situbondo, Banyuwangi, Jember, Probolinggo, Gresik, Lamongan and Tuban. Number of sample in every district was divided into sub district or municipality with proportional calculation. In every pond, sample of shrimp was taken out using sampling bias and subjected to IMNV detection using RT-PCR with IQ 2000 IMNV. Those samples were also observed any abnormality and clinical signs. Pathogenicity test of IMNV in white shrimp was carried out in vivo. Forty four healthy shrimp (free from TSV, WSSV, IHHNV and IMNV) were separated into two groups. Artificial infection was done through injection of IMNV extraction prepared from infected shrimp to last third segment of abdomen of healthy shrimp with dosage of 0.01 cc per gram body weight. Control group were injected with 2 % NaCl solution. Treated and control shrimps were reared for 15 days with 50% water exchange every day and fed at the rate of 5% body weight per day. Observation on clinical sign and mortality were carried out every day. Gills or pleopods of infected shrimp were examined for IMNV confirmatory test with RT-PCR. Fifth and sixth segment of abdomen and cephalothorax were cut longitudinally and fixed in Davidson solution for histophatological analysis. Data obtained of this study were percentage of IMN prevalence and survival rate. Level of IMNV pathogenicity in white shrimp was based on RT-PCR examination, clinical sign, histopathological changes and analyzed with description method. Result of study showed that prevalence of IMN were 23.07% in Banyuwangi, 20.51% in Situbondo, 0% in Jember, 25,53% in Probolinggo and 3,7% in Tuban, Gresik and Lamongan. Total mortality (100%) occurred at day 9 after infection. Clinical signs were started at day third with sixth segment of abdomen became white and subsequently, abdomen and tail became red at day seventh. Pathological lesions were coagulation necrosis and inflammation at muscle. Inflammation was also found at interstitial tissue. Inclusion bodies with dark blue or basophilic colour were also found in muscle, intestine, liver and hepatopancreas. More severe of virus infection caused the high severity of pathological changes.

Kata Kunci : IMN,Infectious myonecrosis,Udang putih, Prevalence, Infectious Myonecrosis (IMN), White Shrimp (Litopenaeus vannamei)