1. Bacterial Diseases

2. ESC and Columnaris These two bacterial diseases are the most common and most devastating bacterial problems in the commercial catfish industry. Estimated economic losses resulting from these diseases is millions of dollars

4. Enteric Septicemia of Catfish (ESC) Causative agent - Edwardsiella Ictaluri Gram Negative, rod shaped, weakly motile Thought to be obligate but can survive in mud for 90 days. Similar to Edwardsiella Tarda

5. Which fish can get ESC? Channel catfish most susceptible White catfish, brown bullhead, walking catfish are also susceptible Blue catfish can get it but are generally resistant

6. Which fish can get ESC? Esc has been isolated from some diseased tropical fish. Trout, salmon and tilapia have been experimentally infected but natural outbreaks have not been reported.

7. Clinical Signs Behavior Tail chasing or spiraling Star gazing (head up tail down) Stop eating

8. Clinical Signs External Signs Red and white ulcers –petecial hemorrhages (pin point size) –Raised pimples (buckshot appearance) Hole or lightened area on head Exopthalmia Swollen belly

9. External Signs

10. Petechial Hemorrhaging (Buckshot appearance)

11. Deteriorating Skull Cartilage

12. ESC “Hole in the Head”

13. Clinical Signs Internal Signs Clear - straw colored or bloody fluid in body cavity Mottled liver Petechial hemorrhages in muscle Intestine often filled with bloody fluid

14. Diagnosing ESC Look at behavioral and external signs Necropsy for internal signs Isolate bacteria from internal organs –run diagnostic tests –determine antibiotic sensitivity

15. Causes of ESC Combination –Pathogen - virulent Edwardsiella ictaluri –Stress –Environment - that favors rapid proliferation of the bacteria Generally in the “ESC Window” 68 - 82 degrees F

16. How Does ESC Spread Enters through –Gut –Nares –Gills Transmitted through water Transmitted by cannibalism Transmitted by carrier fish, equipment and birds

17. Treatment and Prevention Prevention by reducing stress –not always possible Nutritional supplements Winter Feeding Genetic improvement Vaccination Treatment with medicated feeds

18. Medicated Feed Treatment of ESC Romet 30 and Romet B –sulfadinethoxine and ormetoprim –Fed at recommended rate for 5 days –3 day withdrawal period Terramycin –Fed at recommended rate for 10-14 days –21 day withdrawal period

19. Economic Evaluation Need to make sure that treating the fish does not cost more than the fish are worth

20. Other Methods of Control Withhold Feed Wait for temperature change Vaccines

22. Causes of Columnaris Causative agent - Flexibacter columnaris –Gram negative, rod shaped and motile –Non Obligate - present in the natural environment Stress - particularly in warm weather –Especially long term exposure to low levels of toxic ammonia

23. Characteristics of the Disease Rarely occurs unless fish are stressed Most frequently occurs between March and October when water temperatures are above 59F especially in the 75 -85 degree range Can be external, internal or both

24. Characteristics of the Disease Chronic at lower temperatures and more acute at higher temperatures. Likely to reoccur if original stress is not removed All ages, sizes and species can be effected

25. Clinical Signs of Columnaris External –increase in thickness of mucous on skin –saddleback appearance –areas of gray or colorless skin leading to ulcers and open lesions –grey/brown areas on the gills esp. at the tips –yellow colonies inside the mouth –frayed fins

26. Columnaris Colonies Using Skin & Gill Wet Mounts

27. Columnaris on Gills

28. Columnaris (Frayed fins, tail rot)

29. Columnaris Skin Lesions Leading to Open Ulcers

30. Diagnosis External - Microscopic examination of skin and gill wet mounts Internal - Isolation of bacteria and identification proceedurs

31. Treatment Depends on whether the infection is internal or external External only - 2 to 4 ppm KMnO 4 Internal only - Terramycin Both - Terramycin