Tesis para optar al Grado de Magíster en Ciencias de la Acuicultura / La acuicultura en el Perú está creciendo marcadamente en los últimos años, siendo Puno uno de los Departamentos con mayor producción en el cultivo de truchas arcoíris (Oncorhynchus mykiss). A consecuencia de este crecimiento y la falta de producción de ovas nacionales, se ha incrementado su importación desde diferentes países. Al respecto, ello constituye un alto riesgo de introducción de agentes infecciosos que se transmiten por vía vertical como es la Piscirickettsia salmonis, que actualmente es el mayor problema sanitario asociado a altas tasas de mortalidad en la salmonicultura chilena. P. salmonis es una bacteria patógena que fue aislada por primera vez en el año 1989 y es el agente etiológico de la enfermedad denominada piscirickettsiosis. Actualmente dentro del cultivo de truchas arcoíris en Perú, la principal enfermedad en truchas es la yersiniosis, que es causada por el agente infeccioso Yersinia ruckeri, que genera altas pérdidas económicas.

Organisms are continuously exposed to heterogeneous micro- and macro-parasitic species, hence simultaneous infections often occur in wild and farm environments. This joint project aimed to develop a co-infection model between chronic and acute infections, evaluating their impact on the fish immune system. Proliferative Kidney Disease was studied on farmed rainbow and brown trout during natural seasonal outbreaks, using a parasite gene (Tetracapsuloides bryosalmonae RPL18) as a proxy for assessment of parasite burden. In hosts with elevated susceptibility PKD pathogenesis was shaped by an anti-inflammatory phenotype, a profound B cell/antibody response and dysregulated TH cell-like activity. Pathogen-free brown trout were exposed to Viral Haemorrhagic Septicaemia Virus (comparatively using European VHSV-Ia and North American VHSV-IVb strains) or to the bacterium Yersinia ruckeri. This European native species was highly resistant to the VHSV-IVb strain, which was undetectable in internal organs despite raising a strong antiviral and mucosal immune response. Following VHS and Yersiniosis infection, haemo-lymphopoietic organs were screened by RT-qPCR to assess the specific pathogen burdens and characterise the immune responses elicited. Transcription patterns were analysed for Interferons, CXC chemokines, SOCS (potential disease resistance biomarkers) and genes of the PACAP system. Lastly, PKD-infected brown trout were co-infected with VHSV-Ia, resulting in typical lesions while showing reduced and delayed mortality. PKD+/VHS+ fish were identified by RT-qPCR and histopathology screening. Pro-inflammatory and antimicrobial peptide genes were modulated following virus co-infection when compared to fish with single infection, with an earlier activation of cellular and humoral responses, and a stronger up-regulation of TH1 and antiviral genes. Oligonucleotide microarrays were used to assess the broader immune gene transcription modulation between single- and co-infected fish. Overall, the results suggest that the immune response of brown trout might be enhanced during the PKD/VHS co-infection.