Diseases of a Non-infectious Nature

1. Diseases of a Non-infectious Nature

2. Disease Types Associated with Non-living Agents • nutritional • neoplastic (cancer) • toxins • miscellaneous origin...the rest.

3. Nutritional Diseases • proper nutrition is essential to the health of all animals • nutritional diseases in fish are common and associated with either deficiencies or excesses • estimating the role of malnutrition in disease outbreaks involving opportunistic pathogens is essential • not really a problem among wild fish populations because they select a balanced diet

4. What you Can Do to Avoid Malnutrition • estimate proper ration requirement • insure that moisture content is taken into consideration when feeding...why? • are dietary supplements required? • nutrient requirements • proper feeding practices

5. Nutritional Requirements • protein and amino acids • fatty acids • protein:energy ratio • vitamins • minerals • possibly fiber

6. Nutritional Diseases of Fish • Most are chronic in nature (develop slowly) • Six week interval is common. • Early disease symptoms may be subtle and difficult to interpret Why? • often only moderate nutrient deficiencies or excesses are involved • signs of the disease can often be masked by secondary pathogens

7. Nutritional Disease Diagnosis • Requires observation of external and internal signs • Quantitative clinical chemistry on blood, tissues, fluids of infected fish • Histopathalogical (cellular) examination • Feed analyzed for deficiencies • Evaluate feed management

8. Pathological Syndromesprotein/amino acids (AA) • Reduced or abnormal amino acid intake in fish/shrimp results in reduced biosynthesis of many vital substances: enzymes, hormones, certain pigments • Certain amino acids are necessary for fat/carbohydrate metabolism • Amino acids also required for formation of purines, pyrimidines, i.e. DNA, RNA • Diagnosis of protein/AA malnutrition is difficult!!

9. Protein/Amino Acid Deficiency • Observation: poor FCR • Anemia? • Challenge: protein/AA deficiency signs similar to disease caused by other etiological agents • Most common sign: reduction of growth

10. Amino Acid Deficiency • Tryptophan deficit = scoliosis and lordosis • Tryptophan or sulfur amino acid deficiency cataracts* • Excesses of leucine or isoleucine increases valine requirement (antagonism)

11. Dietary Fats and Lipids • Pathological conditions associated with: • high fat intake or dietary fat • deficiency in essential fatty acids • or rancidification (peroxidation) • High fat intake = fatty liver/obesity (check liver for fat droplets in water) • Coldwater species and high saturated fat don't mix (reduced digestibility, flexibility) • Deficiency of linolenic acid = malpigmentation, fin erosion

15. Fatty Acids • Unsaturated fats go rancid (spoil). • This produces peroxides and other toxic compounds. • Peroxidation causes a syndrome similar to muscular dystrophy (usually associated with alpha tocopherol Vit E)

16. Carbohydrates • Excess soluble carbohydrates cause hyperglycemia, build-up of liver glycogen and enlargening of the liver • Lethargy, darkening of color, poor appetite • Might cause increased susceptibility to disease from bacteria, fungi, parasites • Liver malfunctions possible

17. Mineral Deficiencies • Hard to evaluate due to difficulty of removing minerals from diet and water • Goiter in fish? Yep! • Zinc implicated in eye cataracts • Low iron = anemia • Phosphorus deficiency = lordosis, skeletal deformities, skull size

18. Treatments for Nutritional Diseases • Store feed properly (cool and dry) • Use feed by expiration date (90 days for vitamins) • Feed correct amount to fish (don’t underfeed) • If necessary, have feed analyzed ($$$$) • Only use feed from reputable sources. • If you suspect bad feed, throw it out (even if it’s 5 tons!)

19. Neoplastic (Tumor-like) Diseases • cell regeneration, growth, replacement occurs at a specific rate for specific tissues (REM: protein turnover?) • if cell growth and proliferation occurs at an uncontrolled rate, you have a tumor • neoplasia = appearance of tumor mass • hyperplasia = uncontrolled proliferation • two types of tumors: benign and malignant • benign tumors cause fewer negative effects than malignant ones

20. Malignant Tumors • cause formation of altered cells, altered characteristics are passed on to other generations • spread into blood, lymph or other organs is known as metastasis • tumors are also classified by tissue of origin, thus "basal cell carcinoma" or "lymphoma" • oncology or tumor study of fish is relatively recent

21. Causes of Neoplasia • Obscure causes, no single etiology can be found • Cellular changes result of multiple causes • Interacting factors: age, heredity, immunological factors, presence of carcinogens, oncogenic viruses • Fish age and susceptibility may not be true since fish continue to grow • Heredity: thyroid carcinoma in trout (kill these?)

22. Causes of Neoplasia • Heredity: susceptibility to aflatoxin, some species more so than others • Presence of carcinogens: industrialized areas = gonadal, liver tumors • Chlorination = neuroblastomas • Age effect has been shown in terms of aquatic pollutants (even for embryos)

23. Malignant Tumors of Fish • Neoplasms have been found in nearly all organs and cell types of fishes • Incidence is quite low with typically little effect on entire population • Major malignant tumor in fish is "hepatoma" or liver cell carcinoma, first reported in rainbow trout in 1933. • Result of feeding cottonseed meal that had spoiled in the field, producing the fungus Aspergillus flavus • The toxins from fungal spores were identified as the primary etiological agent

24. Liver Cell Carcinoma: aflatoxicosis • There are no outward signs of aflatoxicosis or hepatoma early on. • Enlargement of the liver, followed by emaciation • As disease progresses, liver nodules grow and contact other organs • Confirmatory diagnosis is via histopathology/oncology of the tumor

25. Hepatoma Therapy and Control • There is no cure! • Must eliminate aflatoxin from the feed. • Usually eliminated from feeds by addition of proprionic acid or ammonia treatment of the feedstuff • Prognosis: morbidity may reach 70% in culture facilities • Linear relationship between cottonseed meal intake and incidence of hepatoma

26. Idiopathic Epidermal Hyperplasia

27. Idiopathic Epidermal Hyperplasia (striped bass epithelium)

28. Stomatopapilloma in European Eel

29. X-cell Lesions in Gill Cavity of a blue whiting

30. Fibrosarcoma on a Goldfish

31. Mass in the throat of a porkfish caused by a thyroid tumor

32. Osteomas on the rib and vertebral column of an Atlantic croaker

33. Benign Tumors of Fishes • have been identified for many fish species throughout the world • most cases are concerned with individual fish and not the entire population • benign tumors are usually by oncogenic viruses or bacteria and may be more numerous than other types • good example in fish is the bacterium Mycobacterium fortuitum which stimulates production of tumor-like masses in the kidney, liver or spleen • other agents include copepod parasite which produce fibromas where they attach