Transcript Diseases of a Non-infectious Nature

Diseases of a Noninfectious Nature
Disease Types Associated
with Non-living Agents
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4)
nutritional diseases
neoplastic diseases
toxic substances
miscellaneous origin
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
 are dietary supplements required?
 nutrient requirements
 proper feeding practices
Nutritional Requirements
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protein and amino acids
fatty acids
protein:energy ratio
vitamins
minerals
possibly fiber
Nutritional Diseases of Fish
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most are chronic in nature
usually develop slowly over an extended
period of time
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 examination
 also may be useful to have your feed
analyzed to rule out deficiencies
 evaluate feed ration, frequency and quality of
feed management
Pathological Syndromes
protein/amino acids
 reduced or abnormal amino acid intake in fish/shrimp
results in reduced biosynthesis of many vital
substances:
enzymes, hormones, certain pigments,
and cofactors
 certain amino acids are necessary for oxidation and
utilization of fats/carbo's
 amino acids also required for formation of purines,
pyrimidines
 diagnosis of malnutrition associated with protein or
amino acid deficiencies is difficult due to being
nonspecific
Protein/Amino Acid
Deficiency
 one sign is poor FCR, FCE
 for fish, this may be shown as anemia or low
blood erythrocyte count
 problem is that protein and amino acid deficiency
symptoms are similar to disease caused by other
etiological agents
 most common sign: reduction of growth
 for fish, deficiency of the EAA tryptophan will lead
to scoliosis and lordosis
Amino Acid Deficiency
 other signs of tryptophan deficiency
include cloudiness (cataracts) of the
eye lens
 this condition also occurs from
deficiency of sulfur containing AA's
 excesses of leucine or isoleucine
increases valine requirement
(antagonism)
Dietary Fats and Lipids
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pathological conditions associated with:
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high fat intake or dietary fat
deficiency in essential fatty acids
or rancidification (peroxidation)
high fat intake = fat deposition in liver and obesity
(yes, it's a disease)
check liver for fat droplets in water
coldwater species and high saturated fat don't mix
(reduced digestibility, flexibility)
deficiency of linolenic acid = de-pigmentation, fin
erosion, fainting
Fatty Acids
 unsaturated fats are subject to rancidification
 this is a process where peroxides and other toxic
compounds are produced
 peroxidation causes a syndrome similar to muscular
dystrophy (usually associated with alpha tocopherol
Vit E)
 incomplete metabolism of fat causes production of a
pigment that is stored in the liver, affecting its proper
function
 no specific treatment for peroxidation
Carbohydrates
 excess soluble COH results in hyperglycemia, buildup of liver glycogen and enlargening of the liver
 the practical effect of this is not known
 lethargy, darkening of color, poor appetite
 increased glycogen storage in liver results in
increased susceptibility to disease from bacteria,
fungi, parasites
 liver malfunctions
Mineral Deficiencies
 hard to evaluate due to difficulty of removing minerals
from diet and water
 most famous study showed that fish can develop
goiter (thyroid condition associated with iodine
deficiency)
 zinc implicated in eye cataracts
 low iron = anemia
 phosphorus deficiency = lordosis, skeletal
deformities, skull size
Treatments for Nutritional Diseases
 protein/amino acid deficiency: confirm feed nutrient
levels, rations, storage
 lipids/fatty acids: analyze feed FA levels, insure
quality at time of manufacture; reduce dietary lipid
 carbohydrates: check liver glycogen content, blood
glucose; reduce dietary level of digestible carbo's
 vitamin deficiency: gross signs, blood chemistry,
histopath; check storage, form of vitamin (e.g.,
ascorbic acid)
 mineral deficiency: histopath on thyroid (iodine),
lenses (zinc), blood (iron), etc.; confirm feed nutrient
levels, form of mineral (digestibility)
Neoplastic (Tumor-like) Diseases
in Fish
 cell regeneration, growth, replacement occurs at a
specific rate for specific tissues
 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
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as with other animals cause is obscure
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
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, however, is quite low with typically little
effect on entire population
 major malignant tumor in fish is known as
"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 during the early stages of tumor growth
 enlargement of the liver may then take place and the
fish becomes emaciated
 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 therapy
 must eliminate aflatoxin from the ration in subsequent
generations
 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