Subterranean Fishes of the World

3283

2017

AIM 2017

We know surprisingly little about the pathogens in lab-raised Astyanax mexicanus considering their influence on fish behavior, fertility, and physiology. We performed a comprehensive disease screen on fish from two independent recirculating systems containing a mixture of Surface, Pachon, Tinaja, and Molino populations. Microscopic examination of detritus and water revealed midge fly larvae, monogenean flukes, polychaetes, nematodes, and ciliates. While these are not all parasitic, they could influence water quality and/or be secondary hosts for fish pathogens. We treated one recirculating system with Praziquantel (¼ tsp per 25 gallons) and cleaned each component with 0.5% bleach. One week later, sixty-five adult fish were randomly sampled from each system. Skin scrapes and gill clips revealed two species of flukes (Dactylogyrus sp. And Gyrodactylus sp.) at low numbers in most fish from the treated and untreated system. Virus isolation using pooled fish tissues revealed no cytopathic viruses and similarly no bacteria of interest were isolated by culture. However, we identified six Mycobacterium species by PCR screening. Mycobacteria are common in fish facilities and nearly impossible to eradicate as they can be vertically transmitted. Consistent with the molecular identification of Mycobacterium, histopathology revealed granuloma formation in the visceral organs of some fish, a common feature of infection. Mycobacteria cause disease in humans; contact with water or fish without gloves should be avoided particularly if you have any breaks in the skin. To manage Mycobacterium infection, regularly disinfect surfaces using 70% ethanol, euthanize older fish, and avoid transferring water or fish between tanks and systems. We found that routine detritus removal was the most effective way to decrease fluke, nematode, and midge fly larvae abundance. Knowing and managing what’s in your water will give you confidence in maintaining the health of your colony and producing reliable data.

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