This study evaluated the myxozoan infection and
histopathology of the kidney of freshwater fish Piaractus
mesopotamicus from intensive fish farming in Brazil. A total
of 55 fish were examined for myxozoan infection. Infected
organs were processed by usual histology and stained with
hematoxylin-eosin (H&E) and Ziehl-Neelsen (ZN). From the
total of 55 fish analyzed, 47 (85.45%) presented myxospores,
being 9.09% (5/55) only with Myxobolus sp., 5.45% (3/55)
only with Henneguya sp., and 70.91% (39/55) presenting both
parasites. The presence of myxospores was associated with
histological alterations in both stromal and renal parenchyma.
Myxospores were found mostly in the peritubular interstitial
tissue and in low intensity in the glomerulus which caused
nuclear hypertrophy and loss of Bowman space. An increase
in the glomerular tuft and a reduction in the lumen of the
collector tubules were also observed, besides the high number
of melanomacrophage cells in the glomerulus. This study reports
for the first time detection of myxozoan mixed infection
in one organ of pacu and discuss the possible transportation of
myxospores in the circulating blood
