I have not seen this posted on the forum even though we see the question "What is wrong with my fish?" once in a while. It is from aquanic : http://aquanic.org/publicat/state/ga/baitfish.htm
Note the common stress factors listed in the first para..
Parasites and Disease
At some time an outbreak of some type of disease or parasite will likely occur. However, the severity, frequency and duration of these outbreaks can be reduced by controlling fish stress. Conditions favorable for disease outbreaks require a host, such as the fish, a disease organism such as a parasite and a stress such as low dissolved oxygen. Common stress factors are rough handling, water temperature changes, low oxygen, water quality changes, poor nutrition and fish crowding.
Diseases can be classified as infectious and non-infectious. Infectious diseases include those caused by parasitic bacterial and viral pathogens. In the baitfish industry, it is believed that parasites are the most devastating disease agents because of the variety and number of parasites. Yet treatment of parasite infestations if often simpler than treatment of bacterial or viral infections.
Protozoans Protozoans are small parasites and usually require microscopic examination for diagnosis. Infections of the gills and skin are most common. However, some protozoans can infect fish ovaries causing partial or complete sterility.
1. Ich Ich is usually visible as white spots on the skin; however it also infects the gills of fish. Occurring from fall to spring, Ich often appears after fish have been seined and moved from one pond to another.
2. Trichodina Trichodina is a circular protozoan with many abrasive grooves on its surface. It irritates the skin and gills causing fish to die from impaired respiration problems, secondary infections or starvation. Outbreaks can occur from fall to spring.
3. Ictyoboda Ictyoboda (Costia) is an extremely small parasite. Large numbers cause severe irritation to gills. On the skin, erosion of mucus and skin makes the fish susceptible to secondary bacterial infections. Early diagnosis and treatment are important in limiting mortality.
4. Chilodonella Chilodonella is a parasite that usually attacks the gills but can be found on the skin. It causes red, puffy or frayed gills. Fish mortality is more rapid and extensive than with other external parasites. It occurs in cool weather from fall to spring.
5. Scyphidia and Epistylis Scyphidia and Epistylis attach to the gill or skin surface. They usually occur in the spring and these parasites are characteristic of over fertile water.
6. Sporozoan Parasites Sporozoan parasites are protozoans which produce a cyst in the fish that contains spores. Mitraspora cyprini infects goldfish and can be found in the kidney. The kidney enlarges and the fish appears bloated. Myxobolus notemigoni and M. aregenteus form cysts beneath the scales of golden shiners, making the fish unsightly. Pleistophora ovarie infects golden shiner ovaries, reducing egg production. Egg masses appear discolored, opaque, yellow or brown instead of light green. Treatments for these diseases have not been developed and prevention requires culling of infected fish and disinfection of ponds. Pleistophora infections may be reduced by removing golden shiner females from brood fish ponds after two years of age.
Trematodes (Grubs) Flukes or grubs infect gills, skin and internal organs of fish. These parasites weaken fish and make the fish more susceptible to bacterial or more lethal parasitic infections. The brain fluke of the fathead minnow, (Ornithodiplostomum ptychocheilus) can be controlled by killing its secondary host, the snail. Black grub and yellow grub can also be controlled by destroying snail populations.
Cestodes (Tapeworms) The Asian tapeworm has become and important golden shiner parasite. Small fish less than 1 inch in length are susceptible, with up to 80% mortality. Copepods carry infected stages and the parasite can be transferred by wildlife and equipment. Good pond management, including pond disinfection, disposal of diseased stock and treatment to kill copepods can reduce the chances of infection.
In fathead minnows, Ligula intestinalis, a large visceral worm can cause mortalities of about 3%. No effective treatment has been developed, but prevention by disposal of diseased fish and pond disinfection can reduce losses.
Nematodes (Roundworms) Roundworms are infrequently found in several organs of baitfish. However, in golden shiners, Capillaira catostomi, causes significant mortality by infecting the gut and the fish starves.
Crustaceans Two crustaceans cause significant damage to baitfish. Argulus is an irritant to goldfish causing weight loss and mortality in extreme cases. The anchor worm, Lernaea, infects all fishes and may cause mortality in small fish. The protruding "worm" and red sores cause the fish to be unsalable. Control of copepod forms of these crustaceans is effective in controlling adult forms. Fungi Fungi are often a secondary problem associated with another infection. They usually occur in the fall or winter, but fungus can grow on stressed fish even in the summer. Saprolegnia covers the body of fish with cotton-like growth and causes skin lesions and chronic but severe losses. Branchiomyces grows on the gills of golden shiners causing impaired respiration and mortalities. Good water quality and adequate fish nutrition help prevent fungus outbreaks.
Bacterial Diseases Bacterial infections of baitfishes are almost always related to environmental stress. The most important bacteria, Flexibacter columnaris, Aeromonas hydrophilla and A. salmonicida are found in most soil and water. Because these bacteria are almost always present, they become a problem when conditions favor their growth, especially when warm water becomes nutrient rich or fish are crowded or stressed.
Columnaris infections are often recognized by a pale saddle shaped patch on the back of fish. Other signs are eroded fins and gill filaments. Fish in warm or cold water are susceptible to columnaris when they are stressed. Recent studies indicate that the pH of water may be changed to control columnaris infections.
Goldfish ulcer disease, A. salmonicida, attacks large goldfish. Mortalities of over 40% can result. Lesions on the fish start as small white spots but grow to 1 inch or more in size and are hemorrhagic. Changing water temperatures in the spring and fall encourages this disease.
Another bacterial disease, A. hydrophilla, is common to all species of baitfish. Erosion of skin resulting in open sores or shallow ulcers, bloating, popeye and hemorrhaging under the chin and around fins are all signs of this bacterial infection. Warm water, over 80oF, favors outbreaks..
Viral Diseases The only important viral disease of baitfish infects golden shiners. The golden shiner virus causes gradual mortalities over several months. A few dead or dying fish may appear each day. Hemorrhaging of the underside, back, eye, and head of the fish are signs of this disease. The virus usually occurs in the fall when fish reach 2 1/2 inches in length. Because of the low mortality associated with the disease and the lack of an effective control, the disease is usually allowed to run its course. Pond management including the isolation of infected stock and pond disinfection may help control the spread of the virus.