the presentation provides the various fungal pathogens of fish and shell fish along with their lifecycles, the pathology, histology, epizootiology, prevention and treatment measures

1. MYCOTIC DISEASES –
GENERAL
CHARACTERISTICS,
EPIZOOTIOLOGY,
DIAGNOSIS, PREVENTION
AND TREATMENT

2. Presented
by…..
AKHILA S,
MFSc Fish Nutrition and feed
Technology,
Kerala University Of Fisheries
And Ocean Studies
Kochi
2

3. INTRODUCTION
▸ Two main groups infectious mycopathogens are recognized from
fish and shellfish:
▹ (1) those that are obligate invaders ¹
▹ (2) those that are facultative.
▸ ²Majority of fungal invaders recovered from fish and shellfish are
considered to be facultative
▸ In nature, some of these types also exhibit wide substrate specificity
and can be collected using baiting methods from a variety of
biological surfaces, including decaying algal, higher plant, and animal
tissues, and sediments..
3

4. FUNGAL DISEASES
AFFECTING FIN
FISHES

5. 1. OOMYCETES

6. “▸The earliest record of fungal
infection of any known vertebrate
is that of William Anderson(1748)
who illustrated what is obviously
an oomycete infection of a roach
‘

7. Biflagellate
Heterokont
Zoospores¹
▸ Cause most of micotic infections
▸ Sexual reproduction ²oogamous(oomycetes derive its
name)
▸ Most have a eucarpic ³coenocytic thallus
7

8. The class Oomycetes is divided into four orders
▸ Lagenidiales – Lagenidium rabenhorsteii
▸ Peronosporales - Pythium
▸ Leptomitales - Leptomitus
▸ Saprolegniales – Achlya, Aphanomyces,
Calyptralegnia,Dictyuchus, Leptolegnia,
Pythiopsis, Saprolegnia, Thraustotheca

9. Comparision
Genus Saprolegnia
▸ Zoospores typically swim away from
zoosporangium prior to encystment
▸ Two types of zoospores –
▹ Primary zoospores: pip shaped with
flagella inserted at tip of the spore(feeble
swimmer and encysts shortly after
emergence from zoosporangium)
▹ Secondary zoospore: the above referred
cyst may produce another type of
zoospore, which is typically reniform or
bean-shaped, with its flagella inserted
laterally with the tinsel flagellum directed
anteriorly an the whiplash flagellum
directed posteriorly
Genus Achlya
▸ No free-swimming
primary zoospore.
▸ Spores encyst at the
mouth of the
sporangium where
they form a hollow
ball
▸ Secondary zoospores
emerge from the
cysts at the mouth of
the sporangium
Genus Aphanomyces
▸ In aphanomyces
also encystment
occur at the mouth of
zoosporangium.
▸ Aphanomyces is
distinguished from
Achlya by its more
delicate hyphae and
that zoospores occur
in single row in
zoosporangium
9
video

10. SAPROLEGNIOSIS

11. SALMON DISEASE
(now UND)
Oomycetes were reported for the first
time in the European literature in
association with an epizootic which came
to be called the salmon Disease.
11

12. LIFE CYCLE of saprolegnia
▸ exhibit the complete life cycle, i.e.
▹ the presence of vegetative reproduction by production of
gemmae
▹ asexual reproduction by formation of zoosporangia producing
biflagellate zoospores under favorable conditions
▹ sexual reproduction by formation of male (antheridia) and
female (oogonia) gametangia producing respective gametes
under unfavorable conditions.
12

13. 13

14. Asexual reproduction
▸ The organism produces specialized sporangia from which emerge
zoospores with an anterior tinsel flagellum and a recurrent whiplash
flagellum which may be produced in succession
▸ A primary zoospore with both flagella originates at the anterior end and a
secondary zoospore with the two flagella originate laterally.
▸ Zoospores then germinate to produce a body with cellulose and glucan
walls
▸ The filaments (hyphae) are coarse, and non-septate.
▸ Nuclear division is closed, with a persistent nucleolus and an intranuclear
spindle with poles near pairs of centrioles oriented at 180⁰ to each other.
▸ In the vegetative state, they are diploid organisms with gametic meiosis.
14

15. Sexual reproduction
▸ Begins with the apposition of two
hyphae that are cut off by septa at
their tips and migration of nuclei
through channels from one
(differentiated as an antheridium) to
the other (differentiated as an
oogonium).
▸ After fertilization, the zygote develops
into a thick-walled oospore (resting
stages)
▸ The oospores germinate by the
production of a diploid vegetative
filament
15

16. PATHOLOGY
16

17. Isolation And Culture Of The Parasite
▸ Isolated from soil or water by using
“baits” such as hemp seeds or various
designed agar media
▸ Isolations from fish and fish eggs can
be made by plating mycelium directly
into agar medium with a suitable
bacteriostat or antibiotic¹
▸ A particular procedure is followed
where portions of lesions are examined
for several days to observe the forms
that develop
17
Hemp seeds

18. Gross Pathology
▸ Saprolegnian infections, once initiated, generally tend to be
progressive and terminal
▸ Mycelium spreads outwards from the initial focus of infection and
adjacent infections become confluent
▸ As infection progresses, fish becomes increasingly lethargic(tires
and becomes less responsive to external stimuli)
▸ Presence of light fungal patch makes fish more conspicuous
▸ Mycelium offers physical resistance to passage of fish through
water(easy target of predators)
▸ Loss of equilibrium, eventually death
18

19. 19

20. 20

21. Histopathology
▸ Two most popular technique
1. Grocott’s methenamine-silver method
2. PAS – light green
21

22. In the tissues, the hyphae appear as coenocytic , irregularly branched
structures
Grocott’s
methenamine-
silver method
▸ Hyphae stain brown
to black
PAS –light green
▸ Stain pink to red
22

23. 23
▸ Tissues to be examined histologically
should be fixed as soon as possible after
death(avoid post mortem growth of
hyphae)
▸ Fixatives – Bouins and 10% neutral
buffered formalin

24. Symptoms
▸ white fluff and fur on the body and any part of the eternal anatomy
▸ Fish fungus appears as gray or white patches on the skin/gills
(brown/green (later stage) as they trap sediment)
▸ Patches of skin in serious infections may fall way exposing reddish wounds
and bare flesh.
▸ Fins will begin to recede in many cases, gills also , are extremely vulnerable
▸ slimy patches and cloudy eyes.
▸ promote colour changes in most fish, from patches through to complete
blanching of colour on the entire body.
24

25. Diagnosis
Tentative identification
▸ microscopic examination
of wet mounts of infected
tissues and observation of
branching, filamentous,
aseptate (not separated by
cross-walls, known as
septa) fungal hyphae
comprising the vegetative
mass known as a
mycelium.
Definitive diagnosis
▸ requires culture,
visualization, and
identification of sexual or
asexual reproductive
stages.
25

26. PREVENTION AND TREATMENT
26

27. 27 ▸Vast array of chemicals have been tested for
effectiveness against these fungi in-vitro
▸Include acriflavin, collargol, copper sulphate, diquat,
formalin, gentain violet(crystal violet), griseofluvin, a
gardinol type detergent ( Teepol), hydroquinone,
malachite green, merbromin( mercurochrome), neutral
red, nifurpirinol(Furanace), ozone, 2- phenoxyethanol,
potassium chromate, potassium dichromate, sodium
chloride and silver nitrate.
▸Ultraviolet irradiation and
▸Biological control using bacteria or crustaceans

28. 28
Zinc- free malachite green
▸ Most popular agent for
controlling
saprolegniosis(despite
being a potential mutagen,
carcinogen and teratogen)
▸ Use curtailed in USSR
▸ Inexpensive and effective
fungicide
▸ Dosage : 1 – 5 mg per liter
for bath or flush treatments
▸ 67 mg per liter for short
dips
▸ Topical applications at
100,000 mg/ L(for
salmons)
Common salt
▸ Chemotherapeutant
▸ Inexpensive, safe,
apparently efficacious
▸ 30,000 mg/L
Formalin
▸ Inexpensive and
popular
▸ Chemoprophylactic
and chemotherapeutic
▸ When using,
contamination with
Para-formaldehyde
must be
avoided(ensure
thorough mixing)

29. Isopod
29
▸Also use of the isopod
Asellus militaris, provide
means of controlling the
proliferation of fungi
▸Reduction in use of
fungicides( having adverse
effects on environment, fishes
and man

30. 2.
BRANCHIOMYCES

31. SYSTEMATICS, PATHOLOGY AND EPIZOOTIOLOGY
31

32. BRANCHIOMYCOSIS – Gill Rot, Kiemenfàule
▸ Divided into relatively two distinct
entities
1. Branchiomycosis of carp – Branchiomyces
sanguinis
2. Branchiomycosis of pike and tench -
Branchiomyces demigrans
32

33. Diagnostic features used for separation of B. sanguinis
from B. demigrans
33
B. sanguinis B.demigrans
Principal host Cyprinus carpio Esox lucius,Tinca tinca
Occurance
Usually locallised in blood
vessels of gill arch,gill
filaments and lamellae
Hyphae can penetrate gill filaments and
occur on surface of filament
Morphometric comparisons
Hyphal diameters 8-30 microns 13-14 microns,22-28 microns at the tip
Hyphal wall thickness 0.2 microns 0.5-0.7 microns
Spore diameter 5-9 microns 12-17 microns

34. Mode of transmission
▸ Fungal spores are transmitted by water to gills.
▸ These spores adhere to the gills, germinate and
produce hyphae.
▸ The hyphae penetrate gills epithelium or within the
blood vessels of gills depending on species of
fungi.
34

35. Epizootiology
▸ Both have been reported only within the gill tissue of freshwater fish.
▸ Both species produce spores that are shed from necrotic gill tissue and
probably infect new hosts through a water-borne route.
▸ Mortality may be very high when conditions favor development of the
disease.
▸ Branchiomycosis is most commonly associated with temperatures above
20°C.
35

36. Stress factors
▸ elevation of the water temperature
▸ low dissolved oxygen.
▸ reduced water flow.
▸ over crowded conditions.
▸ high levels of nutrients in the water and phytoplankton
blooms.
▸ high ammonia levels,
▸ high organic loads, and
▸ dense plankton blooms
36

37. Disease Signs
Behavioral Changes
Associated with the
Disease
▸ swim listlessly
▸ exhibit signs consistent
with oxygen deprivation or
osmoregulatory distress.
External Gross Signs
▸ Fish with severe infections
will have typical “gill rot”
lesions
▸ The lesions may be similar
to those associated with
columnaris disease or
other gill infections.
37

38. Histopathological Changes
▸ Oomycete hyphae and spores can be easily seen in the gill
vasculature and in extravascular gill tissues stained with
special stains for fungi (periodic acid Schiff’s (PAS) or silver
stains),
▸ There is little host response to hyphae within blood vessels,
but extravascular hyphae provoke an inflammatory
granulomatous response.
▸ Necrosis of filament tips occurs distal to regions where the
gill vasculature has been damaged or blocked.
38

39. 39
A histological section from the gill of a pumkinseed with branchiomycosis. In this PASstained paraffin section,
hyphae and spores stain red. On the right, a higher-magnification view of the same section shown in Figure 3.
Spores can clearly be seen within hyphae growing in the central sinus of the fish gill. Photo by Fred Meyer. E.

40. Culture
▸ The appearance of Branchiomyces in culture is similar to its
appearance in the gills of infected fish
▸ A week after inoculation, thin brown pellicle like colonies can
be seen- surface of Sabouraud’s maltose agar
▸ Hyphae lie on surface of agar(produce neither aerial nor
submerged hyphae
▸ Spores produced in older hyphae(dimensions- spores and
hyphae same as those found in fish)
40

41. PREVENTION AND TREATMENT
41

42. 42
▸ 0.3 mg/L malachite green treatment for 24 hrs
▸ One hour bath containing 1-4 ppm active ingredient of
benzalkonium chloride or 100 mg/L copper sulphate for 10-30
minutes
▸ Salt baths @ 3-5% for prophylaxis and control
(however dose is dependent on water quality and hardness and on
species, age, condition of affected fish)
▸ Generally, sudden onset and rapid course of Branchiomycosis
could lead to high mortality before treatment could be instituted*

43. 43
Discoloration of gill filaments in a largemouth bass with branchiomycosis. Pale filaments are those in which the gill
vasculature has been blocked or damaged by Branchiomyces sp. resulting in greatly reduced numbers of
erythrocytes in gill lamellae. Photo by Andrew Goodwin. Figure 2. A largemouth bass with branchiomycosis. In this
fish, there is multifocal necrosis of gill filaments producing a notched appearance of the gill margin. Photo by
Andrew Goodwin. 1 cm 1 cm

44. 44

45. Preventive measures
▸ Elimination of environmental factors thought to encourage
initiation of infection*
▹ Take steps to prevent water from being too warm
▹ Prevent excessive accumulation of decomposing organic
matter in ponds during critical warm months of the year
▸ Addition of copper sulphate as an algaecide - @ 8kg/ha(0.5
m depth); 12kg/ha(1.0m depth)
45

46. Control
▸ Introduction of 150-200kg/ha quick lime(added at two week
interval during summer and daily during an outbreak). The pH
is kept below 9.0
▸ If outbreak occurs, feeding of fish should be stopped, dead
fish removed and buried in lime pit
▸ To prevent further outbreaks, ponds are drained, dried and
disinfected with quick lime
46

47. 3.ICHTHYOPHONUS

48. SYSTEMATICS

49. 49 ▸ Consists of two species
▹ I.hoferi
▹ I. gasterophilum(found in the ducts of gastric glands and pyloric cecae
of two marine fishes)
▸ Two other species were also reported, namely
▹ I. intestinalis (salmo trutta and other salmonids)
▹ I. lota(Lota lota)
▸ Both the species were found only in the digestive tract and
not found associated with any pathological condition
▸ Ichthyophonus is a genus of unicellular parasites of fish
▸ Ichthyophonus has been placed taxonomically in the newly
proposed class Mesomycetozoea (believed to link fungi and
animals evolutionarily )

50. ICHTHYOPHONUS HOFERI – morphology and
development
▸ Most frequently occurs in tissue of infected fish as a
spherical, thick walled, multinucleate cell*plate 20.21.23
▸ No: of cyst comprise a nodule contains a prominent centrally
located karyosome with fine rays connecting it to granules
associated with the nuclear membrane
▸ Wall of resing spore has variable thickness(2-11µm), three
layered
▸ Resting spore can germinate to produce a multinucleate
stout hypha
▸ Cytoplasm then evacuates the spore into the hypha
▸ Endogenous cleavage to produce daughter spores of varying
50

51. ▸ Alternatively, the resting spore may produce daughter spores
endogenously without prior formation of a hypha
▸ Daughter spores subsequent to cleavage are released by
rupture of hypha(if no hypha produced, then by rupture of
resting spore wall
▸ Fragmentation – wall of resting spore ruptures and releases
the nuclei(each of which is surrounded by minute bits of
cytoplasm)
▸ They subsequently become enclosed by a wall and develop
into multinucleate resting spores
51

52. 52

53. ICHTHYOPHONIASIS (ICHTHYOSPORIDIOSIS)
53

54. Species affected
▸ Groupers, trouts, flounders, herrings and cods
▸ encompasses more than 80 fish hosts (Spanggaard et al
1994)
▸ includes 35 marine and 48 freshwater fishes
(ReichenbachKlinke & Elkan 1965).
▸ low parasite-host specificity in fish (McVicar 1999).
54

55. Transmission
▸ a natural route of infection has not been demonstrated
▸ in piscivorous and scavenger hosts likely occurs through consumption of infected
prey
▸ Horizontal transmission through cohabitation occurs in some species, including
cultured rainbow trout
▸ The route of transmission for planktivorous hosts, including Clupeids, remains
unclear;
▸ Infection can result in one of three outcomes:
▹ acute disease and mortality,
▹ chronic disease associated with decreased condition and performance, or
▹ subclinical infection *
▸ The prevalence of infection often increases with host size and age
55

56. Disease signs
▸ decreased swimming performance, more pronounced at
warmer temperatures
▸ in hatchery conditions, diseased individuals may appear
lethargic and consume less food than uninfected cohorts.
▸ infected wild herring may aggregate around the periphery of
highly dense schools
56

57. 57 Gross signs externally
▸ ‘sandpaper skin’ on clinically
diseased Atlantic and Pacific
herring(most pronounced on
the caudal third of the body
surface )
▸ caused by large numbers of
raised papules under the skin
surface.
▸ The parasite is eventually
released from these papules,
leaving pigmented ulcers that
resemble flakes of pepper on
the skin surface
▸ Heavily infected rainbow
trout may demonstrate
petechial hemorrhages on the
skin and pigmented ulcers on
the ventral surface.
Gross signs
internally
▸ white or
cream-colored
nodular lesions
throughout the
blood-rich
organs,
including heart,
liver, kidney,
and spleen
▸ Pigmented
lesions occur
in the skeletal
muscle of
heavily
infected fishes,
Microscopic signs
▸ Developmental stages of
Ichthyophonus occurs within
well-defined host cellular
granulomas ,consists of a
large (10-250μm), thick-
walled, multi-nucleate,
spherical body*
▸ Germination tubes (hyphae
and pseudohyphae) are
typically observed after the
infected host has been dead
for a period of time.
▸ A small, motile mono-
nucleate stage (referred to
as endospore, microspore,
amoeboblast, and
plasmodium).

58. 58
Trout with ichthyophonus infection in the brain

59. Want big impact? USE BIG IMAGE
59

60. 60

63. DIAGNOSIS
Internal and
external signs
Tissue squash
preparation
Spherical schizonts(10-250µm)
Culture of
ichthyophonus
from infected
tissues
*MEM,L-15
63
Schizont
germination
Histopathology Molecular
biological tests
~PCR
Genomic DNA isolate
rDNA amplification

64. Histopathology
▸ parasite occurs as single or multiple schizonts inside well-defined host
cellular granulomas(un-encapsulated schizonts are also common
throughout infected tissues during various stages of infection. )
▸ The host granulomatous reaction is easily observed in hematoxalyn and
eosin (H&E) stained tissue sections.
▸ Polysaccharides on the surface of the parasite stain strongly positive with
periodic acid-Schiff (PAS)(other spherical organisms in the 50-250 μm size
range also stain PAS-positive and superficially resemble Ichthyophonus
schizonts in histological sections)*
64

65. Histological view – H&E(A), PAS
65

66. PREVENTION AND TREATMENT
66

67. 67
▸ No established chemo prophylactic or chemotherapeutic
agent available
▸ Proper hygiene measures, including pasteurization of
potentially infected food prevent appearance of disease in
fresh water hatcheries
▸ Dead and dying fish should be removed and disposed of in
accordance with routine hatchery practice

68. 4.DERMOCYSTIDIUM

69. DERMOCYSTIDIOSIS
▸ Dermocystidium is the cause of a disease that affects the skin of fish and can be
found on the gills, fins or body.
▸ causes raised swellings varying in size from 1-2 cms to large lesions up to 10 cm.
▸ lesions are pinkish to red and vary in shape from circular to long elongated
ovals(minimal inflammation around the lesion)
▸ Because of the presence of both spores and hyphae it is currently believed to be a
fungal infection, although some authorities class it with the protozoa.
▸ As the lesion swells, the epidermis covering the swelling gets progressively thinner,
at which stage it is sometime possible to see the white hyphae inside(whitish, cloudy
look).
▸ When the lesion matures, it ruptures spreading thousands of spores into the water.

70. VACUOPLAST
▸ A single, large, partially eccentric vacuole which
frequently contains a large polymorphic
"vacuoplast”; The presence of such a vacuole,
occupying the greater part of the body of the
organism is the distinguishing feature of the
genus Dermocystidium.
70

71. 71

72. LIFE CYCLE
▸ maintained from year to year by overwintering cysts.
▸ Cysts develop from thin-walled, round plasmodium mother cells, about 10
mm in diameter, by elongating and increasing in size.
▸ The nucleus of the plasmodium mother cell degenerates, and a reticular
chromatin-containing structure with dense centra spreads out between
conspicuous lipid droplets in the plasmodium.
▸ Nuclei reappear during fragmentation of the plasmodium.
▸ The sporonts thus formed divide to form sporoblasts, which in addition to
small lipid droplets acquire a non-lipid 'central' inclusion.
▸ The inclusion grows in size to the typical inclusion of the ultimate
Dermocystidium spore.
▸ Sporogenesis takes place mostly in summer, and can continue until autumn.
72

73. 73
▸ The nucleus of the plasmodium mother cell degenerates, and a
reticular chromatin-containing structure with dense centra
spreads out between conspicuous lipid droplets in the
plasmodium.
▸ Nuclei reappear during fragmentation of the plasmodium.
▸ The sporonts thus formed divide to form sporoblasts, which in
addition to small lipid droplets acquire a non-lipid 'central'
inclusion.
▸ The inclusion grows in size to the typical inclusion of the
ultimate Dermocystidium spore.
▸ Sporogenesis takes place mostly in summer, and can
continue until autumn.

74. 74
Transmission electron micrograph of mature spore from a naturally infected
adult Chinook salmon. N: nucleus; M: mitochondrion; 0: osmiophilic inclusion;
arrow: spore wall. Bar = 1.0 pm

75. 75

76. 76

77. 77

78. CLINICAL SIGNS
▸ During outbreaks, Dermocystidium spp cysts initially become
visible breaking through the skin( around 1mm)
▸ Grow in size, ultimately they rupture releasing infectious
spores into the water to then seek a new host fish.
▸ Size of each cyst can vary but they seldom rupture at less than
6mm in size
▸ Few remain intact to reach 10mm and cysts over that size are
extremely rare and usually due to two individual lesions that
appear as one.
78

79. 79
Dermocystidium sp. infecting Silurus
meridionalis. Infected juvenile southern
catfish cultured in a net cage in Jialing
River, Chongqing, China. Fig. 1. Individual
juvenile catfish infected by Dermocystidium
sp. Note ca. 42 pink or red parasitic sites;
cysts of Dermocystidium sp. marked with
arrows. Scale bar = 1 cm. Fig. 2. Ventral
view of the infected catfish. Note the
parasitic sites displaying hyperaemia and
oedema; ruptured epidermis marked with
arrows, cysts of the parasite marked with
arrowheads. Scale bar = 1 cm. Fig. 3.
Lateral view of the infected partial body;
whitish cysts marked with arrows, cysts in
the anal fin marked with arrowheads. Scale
bar = 1 cm

80. 80

81. PREVENTION AND TREATMENT
81

82. 82 ▸ no known treatment(since mode of transmission of disease is
poorly understood)
▸ Fish infected can be housed in malachite green or acriflavine (used
in conjunction with salt) in reduce the secondary risks of fungus
and bacteria into the lesions and this can also lower the level of
cross-infection
▸ Topical treatment can be applied after the cyst has ruptured but
this can be discontinued once the crater or hole the cyst creates
develops a slight gloss which indicates that healing has begun.
▸ Secondary bacterial infection may require antibiotics.
▸ The recovery period is temperature related, therefore not possible to
be accurate about how long this will take but weeks rather than
days should be anticipated.
▸ Diquat baths at 1: 500,000 dilution for one hour twice weekely
appeared to prove effective prophylactic control

83. IINFECTIVITY AND RE-INFECTION
83

84. 84 ▸ It is infective and likely to affect very large numbers of fish
▸ When the lesion ruptures the lesion left, which can be substantial,
seems to heal fairly well and quickly, leaving little sign of the
infection.
▸ It seems to be a spring-time disease, lasting some 6-8 weeks.
▸ It has been reported that re-occurrences can sometimes happen in
previously infected ponds.
▸ Although Dermocystidium does not seem to be fatal in most cases, it
does bring with it a very real threat of secondary infections.
▸ Antibiotic treatments and regular cleaning of the wounds will help
prevent secondary infections and aid recovery.
▸ Also important, as with all diseases, to maintain optimum conditions to
prevent stress causing additional complications.

85. 6.
FUNGI
IMPERFECTI/DEUT
EROMYCETES

86. 1.BLASTOMYCETES
2.HYPHOMYCETES
3.COELOMYCETES
86

87. FUNGAL DISEASE
OF SHELL FISHES
87

88. OOMYCETES

90. Place your screenshot here
90
LAGENIDIUM
Larval Mycosis

91. Diagnostic techniques
Gross Observations:
▸ Appendages or body filled
with white mycelia,
vegetative fruiting
structures visible under
dissecting microscope.
▸ Infected eggs soon give
definite indication of being
abnormal; they are opaque
and dwarfed, the diameter
becoming reduced
Culture:
▸ On saline mycological
media.
▸ Microscopy may be
necessary for specific
identification.

92. 92
Cross section of a blue crab egg parasitized by Lagenidium callinectes, showing extensive enternal
mycelium (400X). Two blue crab eggs from a single pleopod filament (200 X). The parasitized egg (left)
demonstrates 8 external hyphae and 3 empty exit tubes. Internal mycelium is seen through the transparent
egg membranes. Parasitized egg shows reduction in size. ROGERS-TALBERT (1948)

93. LIFE CYCLE
▸ when germination of the zoospore begins, a delicate germ tube is sent
through the egg membranes.
▸ This tube grows rapidly into a network of branched mycelium that soon
fills the entire egg.
▸ From the mycelium, stumpy, thumb-like projections, or hyphae, pass
through the egg membranes to the outside.
▸ These hyphae quickly mature into sporangia which rupture and
discharge new spores to continue the cycle of infection.
▸ When the nutrient material of the egg has been exhausted by the fungus,
the mycelium appears to break up into heavy walled, resting cells that
seem to be resistant to adverse conditions.
93

94. 94

95. 95

96. 96
1. An egg of black tiger shrimp P. monodon infected with a fungus.
Bar = 100 m. 2. A zoea of black tiger shrimp infected with a fungus.
Bar = 100 m.

97. 97 P. monodon
larvae infected
by Lagenidium
sp. ,
Swimming
zoospores with
biflagella
Aftab-Uddin
et al. (2013)

98. PREVENTION AND TREATMENT
98
Disease probably related to poor
husbandry and can be prevented by
enhanced cleanliness.

99. Place your screenshot here
99
HALIPHTHOROS
▸ Larval Mycosis
▸ serious pathogens of
economically
important marine
crustaceans
▸ H. milfordensis
Fragment (arrow)
formation of genus
Haliphthoros

100. Gross signs
▸ 1–3 brown/black focal necrotic lesions in the gills near
insertion of the walking legs.
▸ Hyphae were observed in wet preparations of gill filaments
excised from lesions.
▸ loss of appetite, lethargy
100

101. SYMPTOMS
▸ The typical external symptom of diseased abalones was flat
or tubercle-like swelling formed on mantle, epipode and
dorsal surface on foot (Fig. 2.5).
▸ The mycelium was always observed in the lesions.
101

102. 102
The typical
external symptom
of diseased
abalones was flat
or tubercle-like
swelling
(arrow) formed on
mantle

103. Histology
▸ gill lesions showed hyphae inside the gill cuticle,
▸ invasion and lysis of the skeletal muscle
103

104. PREVENTION AND TREATMENT
▸ Chemicals that interrupted the life cycle by killing zoospores
or preventing sporulation included
▸ malachite green, trifuralin, formalin and copper sulphate.
▸ The appearance of the disease was associated with poor
hygiene and its elimination may be achievable by improving
husbandry practices.
104

105. 105
Figs. 2-3. Scylla serrata eggs. 2. Infected with Haliphthoros milfordensis; note the presence
of discharge tubes (arrowheads) releasing the zoospores (arrow). 3. Un infected eggs
(control treatment). Bars = 100 /μm. Leafio (2002)

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106
Abalone
Tubercle
Mycosis
Disease
HALIOTICIDA
Halioticida noduliformes

107. 107
Light micrographs of Halioticida
noduliformans isolate AF08527
showing various stages of
zoosporogenesis. (A) Aseptate,
branched hyphae. (B) Hyphae
showing cytoplasmic
fragmentation. (C) Developing
zoosporangium. (D) Developed
zoosporangium with discharge
tube. (E) Sporulation of
zoospores. (F) Discharge tube
releasing zoospore. Scale=50
μm. Muraosa et al., 2009

108. ▸ Infected abalone are characterised by multifocal areas of
necrosis of the epithelium, underlying muscle fibres and
connective tissues of the foot, epipodium and mantle.
▸ The lesions were typically 2–3 mm in diameter and contained
numerous hyphae.
▸ H. noduliformans fungus is the cause of abalone tubercle
mycosis disease that has been occurring in South Africa
since 2006.
108

109. 109
Haliotis midae exhibiting typical clinical lesions of
tubercle mycosis caused by Halioticida noduliformans.
(A) Epithelial defect. (B–C) Epithelial defect covered in
loosely adherent off-white material and surrounded by a
thin black reaction zone. (D) Enlarged lesion affecting a
large area of tissue. Macey et al. (2011)

110. 110
1. A mantis shrimp with
fungal infection. The color
of gills changes to brown
(arrow).2. Gill filaments of
mantis shrimp naturally
infected with fungus. Bar
= 80 m m.3. A colony of
the fungus isolated from
mantis shrimp grown on
PYGS agar 4. Fragment
with discharge tubes
(arrow) of the isolate NJM
0643. Bar = 50 m Atami et
al. (2009)

111. Diagnosis
▸ Currently, histopathology and gross observation are used to diagnose this
disease, but these 2 methods are neither rapid nor sensitive enough to
provide accurate and reliable diagnosis.
▸ Real-time quantitative PCR (qPCR) is a rapid and reliable method for the
detection and quantification of a variety of pathogens,
111

112. qPCR assay for species-specific detection and
quantification of H. noduliformans
▸ Effective extraction of H. noduliformans genomic DNA from laboratory
grown cultures, as well as from spiked abalone tissues, (grinding samples
using a pellet pestle followed by heat lysis in the presence of Chelax-100
beads.)
▸ A set of oligonucleotide primers was designed to specifically amplify H.
noduliformans DNA in the large subunit (LSU) rRNA gene, and tested for
cross-reactivity to DNA extracted from related and non-related fungi
isolated from seaweeds, crustaceans and healthy abalone(no cross-
amplification was detected.)
112

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113
ATKINSIELLA
▸ Atkinsiella dubia
▸ marine algae and the
eggs of various
crabs
▸ morphology of its
mycelia and the
process of zoospore
production (vary with
sp)
Mycelia (arrow) in larvae of the swimming crab
artificially infected with Atkinsiella dubia. Scale: 100 ffm.

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114
HALOCRUSTICIDAHyphae in bodies of a rotifer
(arrow)

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115
FUSARIUM
(MITOSPORIC
FUNGI)
isolated from kuruma
prawn
Cause black gill disease/
fusarium disease
Fusarium solani

116. GROSS SIGNS
▸ Appearance of “black spots” that
preceded mortalities in juvenile shrimps
grown in ponds.
116

117. EFFECTS ON HOSTS
▸ Infection usually starts on damaged tissues such as wounds,
gills damaged from chemical treatments or pollutants, and
lesions resulting from other disease processes.
▸ Fusarium solani is an opportunistic pathogen of penaeids and
are capable of establishing infection in shrimps compromised
by other stresses or overcrowding.
▸ Lesions may also serve as a route of entry for other
opportunistic pathogens.
117

118. DIAGNOSIS
▸ Microscopic examination of wet mounts of infected tissues
will reveal the presence of canoe-shaped macroconidia
118

119. PREVENTION AND CONTROL
▸ Preventive measures include the elimination of sources of
Fusarium conidiophores and destruction of infected
individuals.
▸ Several fungicides show promise in vitro but none proved to
be effective in actual field trials.
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120
AFLATOXICOSIS
(RED DISEASE)
▸Aflatoxin produced by
Aspergillus flavus and
other Aspergillus spp.
▸ common
contaminants of not-
properly stored or
expired feeds
▸ Affects Penaeus
monodon, other
Penaeus spp.
Mass of sporangia of Aspergillus
sp. on contaminated feed particles
(fresh mount, 200x)

121. GROSS SIGNS
▸ Yellowish, and eventually reddish discoloration of the shrimp
body and appendages can be observed among pond-cultured
shrimp juveniles.
▸ Affected animals become lethargic with weak swimming
activity near pond dikes.
▸ Soft shelling can also be observed.
.
121

122. EFFECTS ON HOSTS
▸ Histopathologically, necrosis in the tubule epithelium that
proceeds from proximal portion of the tubules to peripheral
tubule tips in the hepatopancreas can be observed.
▸ Growth will be retarded
122

123. DIAGNOSIS:
▸ Affected shrimps will not survive for more than 30 seconds
when collected from the feeding trays.
▸ loss of appetite.
▸ Confirmation is by chemical analysis for the presence of
aflatoxin in the suspected feed/ingredient.
123

124. PREVENTION AND CONTROL
▸ Do not use moldy feeds.
▸ Feeds should be properly stored (for not
more than 6 months) in dry and well-
ventilated areas to prevent, or at least
minimize growth of fungal
contaminants.
124

125. 125
THANKS!
Any questions?

126. REFERENCE
▸ Refai et al. (2016). Monograph on Fungal Diseases of Fish. A guide for postgraduate
students
▸ Diseases of Fish: Book 6 – Fungal diseases of Fishes: Gordon A Neish and Gilbert C
Hughes
▸ Fungal diseases-Eduardo M. Leaño,SEAFDEC/AQD Institutional Repository (SAIR)
▸ Diseases of Fish and Shellfish Caused by Marine Fungi - Kishio Hatai
▸ Fungal Diseases of Fish and Shellfish T.G. RANDl
▸ A review on fungal diseases of algae, marine fishes, shrimps and corals, Indian
journal of Marine Sciences, Vol 35(4),December 2006 pp380-387

127. Credits
Special thanks to all the people who made and
released these awesome resources for free:
▸ Presentation template by SlidesCarnival
▸ Photographs by Startupstockphotos
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