RESUMO
Syncytial hepatitis (SHT) is an emerging viral disease of tilapia characterized by significant morbidity and mortality. This study aimed to establish the production-level risk factors associated with presence and severity of SHT. Production factors were analysed during multiple outbreaks of SHT that occurred between 2011 and 2013 on a single tilapia farm in Ecuador and compared with the year 2010 before the SHT outbreaks. Relative risks, t tests, modified Poisson and forward stepwise linear regression analyses were performed using EPIINFO™. Compared to other strains, Chitralada had an elevated risk of SHT [RR = 2.1 (95%CI 1.8-2.4)]. Excessive mortality associated with the presence (and severity) of SHT increased by 611 (365), 6,814 (5,768) and 388 (340) deaths per 100,000 fry when stocking density, dissolved oxygen and pond production cycles were raised by 1 fish/m2 , 1 mg/L and 1 cycle, respectively. Excessive mortality associated with the presence (and severity) of SHT decreased by 337 (258) and 1,354 (1,025) deaths per 100,000 when stocking weight and water temperature increased by 1 g and 1°C, respectively. Time (season and stocking year) was not significantly associated with SHT. This study shows that some production factors increase the risk incidence and severity of SHTon a farm.
Assuntos
Aquicultura/métodos , Ciclídeos/virologia , Doenças dos Peixes/virologia , Hepatite Viral Animal/epidemiologia , Infecções por Orthomyxoviridae/veterinária , Animais , Ciclídeos/genética , Surtos de Doenças/veterinária , Equador , Doenças dos Peixes/epidemiologia , Doenças dos Peixes/mortalidade , Células Gigantes/virologia , Orthomyxoviridae , Fatores de Risco , TemperaturaAssuntos
Doenças dos Peixes/epidemiologia , Doenças dos Peixes/microbiologia , Infecções por Bactérias Gram-Negativas/veterinária , Perciformes , Photobacterium/isolamento & purificação , Animais , Contagem de Colônia Microbiana/veterinária , Infecções por Bactérias Gram-Negativas/epidemiologia , Infecções por Bactérias Gram-Negativas/microbiologia , Granada/epidemiologiaAssuntos
Ciclídeos , Doenças dos Peixes/patologia , Pesqueiros , Trato Gastrointestinal/patologia , Células Gigantes/patologia , Fígado/patologia , Animais , Doenças dos Peixes/etiologia , Trato Gastrointestinal/ultraestrutura , Células Gigantes/ultraestrutura , Fígado/ultraestrutura , Microscopia Eletrônica de Transmissão/veterináriaRESUMO
The distribution of antigen and pathological changes induced by an experimental infection with Aeromonas hydrophila strain KJ99, and its extracellular products, were studied in two species of fish. The microorganism was disseminated systemically and the haemodynamic and tissue changes were similar to those observed in septicaemia of mammals. Intussusception, degeneration and necrosis of the nervous plexus and muscular layers of the gastrointestinal tract were common findings.