Freshwater Amoebiasis - Histopathology

Fish affected with branchial amoebiasis, have marked epithelial fusion and hyperplasia, leading often to loss of normal gill architecture, with obliteration of interlamellar spaces. Several species are involved, some of which invade the lamellar epithelium.

O. mykiss, gill, H&E; severe lamellar hyperplasia — **Figure 1. Rainbow trout, gill, H&E; severe lamellar hyperplasia**

Trophozoites can therefore be seen in small groups within the branchial epithelium as well as on the surface.

**Figure 2. Rainbow trout, gill, H&E; severe lamellar hyperplasia.**

Several diagnostic methods can be used for the detection of amoebae, including whole mounts of fresh gills, histopathology, isolation and culture, in situ hybridization (ISH), electron microscopy and indirect immunofluorescence.

Differential diagnoses include bacterial gill disease (BGD), flavobacteriosis and mycosis.

Freshwater Amoebiasis — **Figure 4. Rainbow trout, gill, trophozoites are observed on lamellar surface, H&E.**

REFERENCES

Nash, G., Nash, M., & Schlotfeldt, H. J. (1988). Systemic amoebiasis in cultured European catfish, Silurus glanis L. Journal of Fish Diseases, 11(1), 57-71.
Sawyer, T. K., Hnath, J. G., & Conrad, J. F. (1974). Thecamoeba hoffmani sp. n.(Amoebida: Thecamoebidae) from gills of fingerling salmonid fish. The Journal of parasitology, 677-682.
Daoust, P. Y., & Ferguson, H. W. (1985). Nodular gill disease: a unique form of proliferative gill disease in rainbow trout, Salmo gairdneri Richardson. Journal of Fish Diseases, 8(6), 511-522.

Freshwater Amoebiasis – Histopathology