Infectious myonecrosis, caused by infectious myonecrosis virus (IMNV), is an important disease of shrimp that has adversely affected the production of cultured Litopenaeus vannamei. The studies reported here were centered on development and/or validation of alternative diagnostic methods for detection of IMNV. Hence, two manuscripts were published in the Journal of Aquaculture and one manuscript was published in the Journal of Fish Diseases. Chapter 2 describes the development of a real-time reverse transcription polymerase chain reaction (real-time RT-PCR) method using TaqMan probe. The results showed that this real-time RT-PCR assay can detect as little as 10 IMNV copies/μl RNA, while the nested RT-PCR can detect 1000 copies/μl RNA. These findings suggest that the TaqMan real-time RT-PCR is “the gold standard” for screening shrimp to protect aquaculture production systems from losses caused by IMNV, because it provides quantification, higher sensitivity and specificity, and because it is less time consuming and less prone to contamination compared to conventional gel-based RT-PCR. In Chapter 3 I evaluated if prolonged storage of infectious myonecrosis virus (IMNV) infected shrimp in Davidson’s AFA fixative can degrade its double-stranded RNA genome resulting in false negative ISH reactions. Shrimp were collected at Day 12 post-injection and fixed in Davidson’s AFA for five different preservation times (1, 2, 4, 7 and 10 days). Hence, in the present report it was found that the length of time (up to 10 days) in Davidson’s AFA did not have a deleterious effect on the ISH reaction for IMNV. The Chapter 4 describes the development of a reverse transcription loop-mediated isothermal amplification and nucleic acid lateral flow (RT-LAMP-NALF) for detection of IMNV. The RT-LAMP-NALF method combines simplified nucleic acid extraction, a reverse-transcription loop-mediated isothermal amplification platform, and one-step visual colorimetric confirmation of the IMNV amplified sequences using a generic NALF qualitative detection test strip. The RT-LAMP-NALF was found to be 100 and 10 times more sensitive than one-step RT-PCR and RT-LAMP (two primer pairs), respectively. These results clearly demonstrate that the RT-LAMP-NALF method is specific, sensitive, can shorten the time for analysis, and has potential application for IMNV diagnosis in resource-poor diagnostic settings.

Submitted by (edna.saturno@ufrpe.br) on 2017-02-22T13:02:10Z No. of bitstreams: 1 Suzianny Maria Bezerra Cabral Silva.pdf: 1259614 bytes, checksum: e36cf9293552877b5a90863a34eee04d (MD5) / Made available in DSpace on 2017-02-22T13:02:10Z (GMT). No. of bitstreams: 1 Suzianny Maria Bezerra Cabral Silva.pdf: 1259614 bytes, checksum: e36cf9293552877b5a90863a34eee04d (MD5) Previous issue date: 2010-02-01 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The Pacific white shrimp Litopenaeus vannamei is the most important shrimp species in volume in world aquaculture. However, in recent decades, outbreaks of several diseases, especially viral diseases, were responsible for significant economic losses, threatening the sustainability of shrimp farming worldwide. In 2004, Brazilian shrimp farming was seriously affected by a new disease, caused by the Infectious myonecrosis virus (IMNV). Thus, disease control based on rapid and sensitive pathogen detection methods has become a priority worldwide. In this study, specific quantification method for IMNV was developed using real-time PCR with SYBR Green dye and viral load of the principal target tissues was quantified. A recombinant plasmid that contains the target IMNV sequence was constructed and a linear relationship between plasmid DNA and Ct values (R² = 0.992) was obtained for a range from 108 to 10² copies of IMNV. Viral load of IMNV was different for various tissues, being higher in haemolymph and muscle, followed by pleopods and gill. / O camarão marinho (Litopenaeus vannamei) é a mais importante espécie de camarão em volume na aqüicultura mundial. Entretanto, nas últimas décadas, surtos de diversas doenças especialmente as de etiologia viral foram responsáveis por perdas econômicas significativas,ameaçando a sustentabilidade da carcinicultura mundial. Em 2004, a carcinicultura brasileira foi seriamente afetada por uma nova doença, causada pelo vírus da Mionecrose infecciosa (IMNV). Assim, o controle de doenças baseado em métodos de detecção rápida e sensível de patógenos tornouse uma prioridade em nível mundial. No presente estudo, um método específico de quantificação para IMNV foi desenvolvido usando PCR em tempo real com o corante SYBR Green e a carga viral dos principais tecidos-alvo usados para o diagnóstico de IMNV foi determinada. Um plasmídeo recombinante contendo uma seqüência do vírus foi construído e uma relação linear de 0,992 foi obtida entre a quantidade de DNA plasmidial e os valores de Ct para uma faixa de 108 a 10² cópias de IMNV. A carga viral detectada nos tecidos mostrou que há diferença entre eles e os maiores valores estiveram presentes na hemolinfa e músculo, seguida de pleópodo e brânquia.