fungal diseases of shrimp

1. Fungal Diseases of
Shrimps
Aditya Kumar Baruah
(AAH-MA7-01)
COURSE:
Bacterial and
fungal diseases
of finfish and
shellfish
(AAH502)

2. Introduction
• Fungal infections are common in the fish culture, but it possible for shrimp to get
fungal infections as well.
• It's unavoidable, since fungal spores are everywhere, in the air and water.
• Fungi are plant like organisms but unlike plants are not capable of photosynthesis.
• All fungal diseases are called Mycosis (plural: mycoses).
• Fungi are usually fought off by a healthy immune system, so we only see this in
weakened or injured shrimp or just after a moult.
• Spores attach themselves to weakened sites on the shrimp and break out as a
cottony white growth.
• If not treated quickly, the spores will invade any dead tissue cells and in the process
infect more tissue causing a greater infection.
• At times, if the infection is only on the surface of the shrimp's shell, a moult can get
rid of the fungus. It is only by timeliness/chance that such a situation could rectify
itself. At other times, treatment is required.

3. MAJOR FUNGAL DISEASES IN
SHRIMPS
• Larval mycosis- Lagenidium sp.
Sirolpidium sp.
• Black gill disease- Fusarium sp.
• Red disease- Alfatoxicosis

4. Larval Mycosis
CAUSATIVE AGENTS:
• Lagenidium spp., Sirolpidium spp., Haliphthoros spp.
SPECIES AFFECTED:
• All Penaeus species, crabs (e.g. Scylla serrata)

5. GROSS SIGNS:
• Sudden onset of mortalities in larval stages of shrimps and crabs.
• Crab eggs are also susceptible for mycotic infection.
• The commonly affected larval stages among shrimp species are
the protozoeal and mysis stages.
• Infected larvae become immobile and will settle to the bottom of
the tank if aeration/circulation is interrupted.
• Presence of excessive mycelial network visible through the
exoskeleton of moribund and dead larvae.

6. EFFECTS OF HOSTS:
• Progressive systemic mycosis that is accompanied by
little or no host inflammatory response can be
observed.
• Infection is apparently lethal, accumulating mortality of
20-100% within 48-72 h after onset of infection.

7. Causative agents:
Lagenidium sp.
Phylum: Heterokonta
Class: Oomycota
Order: Lagenidiales
Family: Lagenidiaceae
Genus: Lagenidium
(Schenk, 1859)

8. Lagenidium sp.
• In wild crustacean population, it is known as an
egg parasite, while in aquaculture it affects both
eggs and larvae of crustaceans.
• Lagenidium callinectes (Couch, 1942) is a marine
phycomycetous parasitic fungus in eggs and
larvae of marine crustaceans.
• First report in larvae of penaeid white shrimp
Penaeus setiferus (Lightner & Fontaine,1973)

9. • The hyphae of Lagenidium callinectes are irregularly branched, septate, and
contain a cell wall and membrane, vacuoles, mitochondria, ribosomes, small
and large vesicles.
• The spores occur singly or in pairs.
• The fungal mycelium may either invade and embed itself in the tissues, or
alternatively, replace all the muscle tissues of the infected larval P. monodon.
• Fungus infected, untreated populations of nauplii, zoea and mysis exhibited
heavy mortalities

10. • Lagenidium sp. exhibited growth in potato
dextrose agar medium and in Sabouraud's agar
at 28 °C.
• The pathology of Lagenidium in all host species
is apparently similar.
• Lagenidium is particularly troublesome in
aquaculture of marine decapod crustaceans and
it is reported to be responsible for major
epizootics of the larvae of most species of
penaeid shrimp throughout the world (Lightner
1977, 1981).

11. Species affecting crustaceans

12. Lagenidium infection in crustacean larvae.
Larva of Penaeus monodon heavily infested with the fungus (note
the mycelia [arrows] completely replacing the body tissues of the
larva; and the vesicles [arrowheads] ready to release the
zoospores).

13. Filaments of Lagenidium in the tail of Penaeus
monodon larva (arrows). Zoospores in a vesicle
(arrowhead)
Zoosporangial development of
Haliphthoros sp. by hyphal
fragmentation

14. Sirolpidium sp.
Phylum: Oomycota
Class: Peronosporea
Order: Myzocytiopsidales
Family: Sirolpidiaceae
Genus: Sirolpidium
Species: Sirolpidium zoophthorum
A larval shrimp showing
hyphae of Sirolpidium inside
abdominal appendages.

15. Pathogenesis
• Affects larvae ranging in stage from early veliger
to post-metamorphic juveniles up to 400 µm in
diameter.
• Fungus spreads throughout the soft-tissues
causing them to disintegrate.
• The sporangia produce tubes which protrude
outside the shell and release motile zoospores.
• In heavily infected larval cultures over 90% of
larvae can be killed within two days.

16. DIAGNOSIS FOR LARVAL MYCOSIS
• Microscopic examination of affected larvae will reveal extensive, non-septate,
highly branched fungal mycelia throughout the body and appendages
• Specialized hyphae or discharge tubes, with or without terminal vesicles, may
be present, and could be the basis for identification of the causative agent.
• Motile zoospores may be observed being released from the discharge tubes in
the case of some species.
• Classification of the type of organism causing particular epizootic of larval
mycosis is dependent upon the microscopic examination as follows:
– Lagenidium – zoospores are released from terminal vesicle
– Haliphthoros – absence of terminal vesicles; zoospores are released through
discharge tubes formed by the zoosporangia
– Sirolpidium- Larvae contain looped, sparsely branched mycelia, with
constrictions at intervals between segments which may be swollen and
frequently lobed.

17. Molecular diagnosis
• PCR-based detection of Lagenidium DNA in frozen and
ethanol-fixed tissues
 First-round PCR, which utilized universal fungal primers ITS1
and ITS2P,
 Second-round PCR using the Lagenidium-specific primers
LAG1 and LAG2 (Nadine et.al., 2002)
• Research has been going on for developing DNA-based
diagnostics, PCR primers and DNA probes, specific for
Sirolpidium zoophthorum that allowsdetection of early
infections, so that control measures can be implemented
within the hatchery.

18. PREVENTION AND CONTROL
• Disinfection of contaminated larval rearing tanks and chlorination and/or
filtration of the incoming water can prevent outbreaks. Different
antimycotic compounds have been tested in vitro.
• Use of calcium hypochloride @500ppm for 24 hours in hatcheries is found
to be mycocidal.
• Malachite green oxalate @ 6-10ppb in prawn/shrimp hatcheries.
• 1-10 ppm formalin
• egg disinfection with 20 ppm detergent followed by thorough rinsing before
hatching.
• 0.5 ppm treatment with Trifluralin significantly reduced the mortality of
infected larval populations (i.e. 1-1% nauplii, 3-28% zoea and 5-21% mysis
mortality).
• For Sirolpidium: No known treatment.
Batches containing infected individuals should be destroyed in an
approved manner; disinfect all containers and equipment in contact with
the infected stock.

19. Black Gill Disease
CAUSATIVE AGENT: Fusarium solani
SPECIES AFFECTED: All Penaeus species

20. Fusarium sp.
Kingdom: Fungi
Phylum: Ascomycota
Class: Sordariomycetes
Subclass: Hypocreomycetidae
Order: Hypocreales
Family: Nectriaceae
Genus: Fusarium
Species: F. solani

21. Some spp.- Fusarium graminearum, Fusarium asiaticum, Fusarium
culmorum, and Fusarium avenaceumFusarium oxysporum
• Fusarium solani produces colonies that are white and cottony.
• However, instead of developing a pink or violet centre like
most Fusarium species, F. solani becomes blue-green or bluish
brown.
• On the underside, they may be pale, tea-with-milk-brown, or
red-brown.
• However, some clinical isolates have been blue-green or ink-blue
on the underside.
• F. solani colonies are low-floccose, loose, slimy, and sporadical.
• When grown on Potato Dextrose Agar (PDA), this fungus grows
rapidly, colonies reach a diameter of 64–70 mm in 7 days.

22. • Fusarium solani has aerial hyphae that give rise to conidiophores laterally.
• The conidiophores branch into thin, elongated monophialides that
produce conidia.
• Phialides that produce macroconidia are shorter than those that produce
microconidia.
• The macroconidia produced by F. solani are slightly curved, hyaline, and
broad, often aggregating in fascicles.
• Typically the macroconidia of this species have 3 septa but may have as many
as 4–5.
• Microconidia have thickened basal cells and tapered, rounded apical cells.
• Fusarium solani also forms chlamydospores most commonly under suboptimal
growth conditions

23. GROSS SIGNS:
Appearance of “black spots” that
preceded mortalities in juvenile shrimps grown in ponds.
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.
• Once infection is established, it is usually progressive with 30%
remission rate.
•Lesions may also serve as a route of entry for other opportunistic
pathogens.

24. DIAGNOSIS
• Microscopic examination of wet mounts of infected tissues
will reveal the presence of canoe-shaped macroconidia.
Infection may begin at different loci and spread slowly.
• Nested PCR: EF1/EF2 primer pair.
• A nested PCR with Fa/Ra in both steps was tested but
produced only a smear or no product at all.
• Therefore, new primers Fa+7 and Ra+6 were designed by
extending primers Fa and Ra at their 5′ ends.
• The TEF1 sequences of several Fusarium species are of
concern.

25. Aflatoxicosis (Red Disease)
CAUSATIVE AGENT:
• Aflatoxin produced by Aspergillus flavus and other Aspergillus
spp. which are common contaminants of not-properly stored or
expired feeds.
SPECIES AFFECTED: Penaeus monodon, other Penaeus spp.
.

26. 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
DIAGNOSIS:
• Affected shrimps will not survive for more than 30 seconds
when collected from the feeding trays. There will also be loss
of appetite.
• Confirmation is by chemical analysis for the presence of
aflatoxin in the suspected feed/ingredient.

27. 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.

28. Pathological changes in the hepatopancreas and heamatopoetic organs of shrimp
having red disease

29. Conclusion
• Fungal diseases arise due to bad pond hygiene.
• Keeping the organic load less in the system avoids majority of
fungal diseases.
• The diseases caused by fungi are mostly secondary.
• Very few works has been done on these shell fish fungus and
not much works has been done on the histopathological
effects of these fungus and diagnostic techniques are also not
well studied.
• Proper management strategies are to be taken in shrimp
culture to avoid loses due to these opportunistic pathogens.

30. References
• Davis, H.C. and V.L. Loosanoff. 1955. A fungus disease in bivalve larvae.
Proceedings of the National Shellfisheries Association 45: 151-156.
• Davis, H.C., V.L. Loosanoff, W.H. Weston and C. Martin. 1954. A fungus
disease in clam and oyster larvae. Science 120: 36-38.
• NADINE R. ZNAJDA, AMY M. GROOTERS‡ and ROSANNA MARSELLA,2002.
PCR-based detection of Pythium and Lagenidium DNA in frozenand
ethanol-fixed animal tissues. Veterinary Dermatology, 13: 187–194
ackwellScience,Ltd.
• Woo, P.T.K, 2006, Fish Diseases and Disorders, volume3, pp.205-229
• Muraosa,Y., Lawhavinit, O., Hatai, K., Lagenidium thermophilum isolated
from eggs and larvae of black tiger shrimp Penaeus monodon in Thailand,
Fish Pathology.41(1), 35-40, 2006.3