A granulomatous disease in pejerrey (Odontesthes bonariensis).

LOBATO V; SOMOZA G; LÓPEZ G ; MIRANDA L ; MIYAZAKI T ; BERASAIN G

Bariloche

Simposio; VI Simposio Argentino de Ictiología; 2019

Since 2016, therehas been broken out a sub-acute mortality in the pejerrey stock taken from thewild and reared in Junín hatchery. The mortality rate of this wild fish(collected from Gómez Lake, Junín county, Buenos Aires) was significantlyhigher than the one of the farmed fish group (from Estación Hidrobiológica deChascomús), though these groups were reared in the same hatchery. Also, themortality rate is higher between spring and summer compared with other seasons. Diseased fishsometimes showed light hemorrhages on the skin of body surface and occasionallypop eyes. After a naked eye observation on inside organs, some white and hardparticles were seen in the kidney, spleen and liver. The histopathologicalobservation showed that these particles were mainly consisted by macrophages,epithelial and fiber cells, so they can be named as granuloma. Occasionally, thesegranulomas were also found in the heart and testes but never in the gills,intestine, ovary nor in the brain.A bacterialexamination trying to isolate the causative agent was performed, usingdifferent media: nutrient agar, 5% NaCl added nutrient agar, BHI agar, bloodBHI agar, Sabouraud agar, cytophaga agar and Ogawa plate, but no colonies weregrown from diseased fish samples. Also, a PCR examination with primers coveringwide range of Mycobacteria was performed, using DNA extracted from the kidneyof diseased fish, but any specific amplicon was appeared. In sum, until now,the causative agent of this disease is unknown.