Eye fluke-induced cataract formation in fish: quantitative analysis using an ophthalmological microscope

Area of Science:

• Veterinary Ophthalmology
• Aquatic Parasitology
• Fish Biology

Background:

• Parasitic infections, specifically Diplostomum spathaceum, are known to affect fish health.
• Cataract formation in fish can lead to visual impairment and impact aquaculture.
• Understanding the relationship between parasite load and cataract severity is crucial for disease management.

Purpose of the Study:

• To investigate parasite-induced cataract formation in rainbow trout (Oncorhynchus mykiss).
• To determine the correlation between cataract intensity and the number of Diplostomum spathaceum parasites in the lens.
• To evaluate the utility of slit-lamp microscopy for assessing cataract development in fish.

Main Methods:

• Slit-lamp microscopy was employed to examine cataract formation in rainbow trout lenses.
• The intensity and location of cataracts were scored based on the 3-dimensional view provided by the microscope.
• Parasite burden within the lens was quantified and correlated with cataract severity.

Main Results:

• Cataract intensity showed a significant positive correlation with the number of Diplostomum spathaceum parasites.
• The pattern of exposure to parasite cercariae also influenced the development of cataracts.
• Slit-lamp microscopy proved effective for detailed assessment of cataract location and intensity.

Conclusions:

• Diplostomum spathaceum infection leads to significant cataract formation in rainbow trout, directly related to parasite burden.
• Slit-lamp microscopy is a valuable tool for quantifying cataract severity and understanding underlying mechanisms in fish.
• This methodology has potential applications in fish farming for disease monitoring and in broader parasitological research.