Download Diseases of a Non-infectious Nature

Diseases of a Noninfectious Nature
Disease Types Associated
with Non-living Agents
1)
2)
3)
4)
nutritional
neoplastic (cancer)
toxins
miscellaneous origin...the rest.
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
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
Nutritional Requirements
 protein and amino acids
 fatty acids
 protein:energy ratio
 vitamins
 minerals
 possibly fiber
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?
1) often only moderate nutrient deficiencies or
excesses are involved
2) signs of the disease can often be masked by
secondary pathogens
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
Pathological Syndromes
protein/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!!
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
Amino Acid Deficiency
 Tryptophan deficit = scoliosis and lordosis
 Tryptophan or sulfur amino acid deficiency
cataracts*
 Excesses of leucine or isoleucine increases
valine requirement (antagonism)
Dietary Fats and Lipids

Pathological conditions associated with:
1)
2)
3)
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
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)
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
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
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!)
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
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
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?)
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)
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
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
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
Idiopathic Epidermal Hyperplasia
Idiopathic Epidermal Hyperplasia
(striped bass epithelium)
Stomatopapilloma in European Eel
X-cell Lesions in Gill Cavity of a
blue whiting
Fibrosarcoma on a Goldfish
Mass in the throat of a porkfish
caused by a thyroid tumor
Osteomas on the rib and vertebral
column of an Atlantic croaker
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