Fungal Diseases on Fishes

Most common fungal diseases present in Fishes.

1. FUNGAL DISEASES Reported by: JULY B. ARIÑEZ

2. Fungi Heterotrophic straminipilous organisms E ukaryotic Can be unicellular or multicellular Cell walls made of chitin Contain no chlorophyll Filamentous Either be saprobes or parasites

3. Structure and Reproduction Have filaments called hyphae that can either be septate or non- septate Networks of hyphae are called mycelium Body – soma or thallus (capable of growth) * Zoosporic fungi or straminipilous fungi cause most fungal disease of aquatic animals.

4. MAJOR FUNGAL DISEASES

5. CONTRIBUTING FACTORS Stress factors such as: Mechanical injury after handling Exposure to extreme pH levels Prolonged exposure to low water temperatures L ack of food Excessive use of chemotherapeutants Presence of other microbial infections (e.g. bacterial, viral) increase

6. Saprolegniosis ( Saprolegniasis ) a.) Causative Agents: Saprolegnia spp., Achlya spp., and Aphanomyces spp . b.) Species affected: Freshwater fish (carps and goldfish) c .) Signs: 1. Formations of white cottony growth on fish eggs or tissues. 2. F ish becomes lethargic, tires easily and respond slowly to stimuli 3. Histopathologically , rapid destruction of epidermis with slight inflammation are observed. Figure 1. Mycelial filaments of Saprolegnia sp . on the gills of red drum with saprolegniasis (fresh mount, 100x)

7. Saprolegniosis ( Saprolegniasis ) d .) Diagnosis: Microscopic examination reveals the characteristic hyaline and coenocytic mycelia Numerous sporangia – tentative generic identification. e .) Prevention and Control: Bath treatments of chemotherapeutants such as: Zinc-free malachite green (67 mg/L for 1 min; 0.2 mg/L for 1 h) Sodium chloride (22 g/L for 30 min; 30 g/L for 10 min) Formalin (0.4-0.5 ml/L 30% formaldehyde for 1 h ) Hydrogen peroxide and increasing the salinity

8. Saprolegniosis ( Saprolegniasis ) Fig. 1. (A) African cichlid with Saprolegniasis . Note dark areas (hemorrhages/ulcers ) at edges of fungal growth. (B) Life cycle of water molds (From Noga EJ. Fungal and algal diseases of temperate freshwater and estuarine fishes. In: Stoskopf M

9. Ulcerative Epizootic Syndrome (UES) a.) Causative agent: Aphanomyces invadans , rhabdovirus and Aeromonas hydrophila Straminipilous organisms such as Aphanomyces strains, Saprolegnia spp ., and Pythium spp . b.) Species affected: <30 freshwater fish species (snakeheads, catfish, gourami, goby and etc.) Figure 2 . Fungal hyphae (black stain) in the connective tissue of the ovary of EUS-infected snakehead, Ophicephalus striatus . ( Gomori methenamine silver stain , 100x)

10. Ulcerative Epizootic Syndrome (EUS) c.) Signs : 1. Darker discoloration and loss of appetite 2. Fish may be hyperactive with very jerky movements 3. Ulcerative lesions throughout the fish’s body 4. Fish becomes lethargic in later stages with exposed head, bone tissues, visceral organs or vertebral column , tail erosion 5. Histopathologically , massive infiltration of the tissues, severe necrosis and minimal inflammation can be observed .

11. d.) Diagnosis Isolation of A. invadans from internal tissues . e.) Prevention and Control: - common among wild fish stocks, prevent the entry of any infected fish in the area a.) Eradication of the causative agent (e.g. fungi) b.) Proper management by reducing stocking densities during prevalence of EUS c.) Farming of EUS-resistant fish species (e.g. tilapia) d.) Application of treatments like: 5 ppm Coptrol (a chelated copper compound or 0.1 mg/L malachite green. Ulcerative Epizootic Syndrome (EUS)

12. Ulcerative Epizootic Syndrome (EUS) Fig . 3 Atlantic menhaden ( Brevoortia tyrannus ) with deep ulceration caused by Aphanyomyces invadans . (Courtesy of Christine Densmore , National Fish Health Research Laboratory, US Geological Survey, Kearneysville , WV.)

13. Branchiomycosis (Gill rot) a.) Causative agents : Branchiomyces spp . b.) Species affected: Carps , goldfish, eels c.) Signs: 1. Gills become pale with brownish areas 2. Necrotic areas susceptible for saprolegnian infections. 3. Gill fungal hyphae obstruct blood circulation 4. Necrosis, lamellar epithelial cells and lamellar fusion proliferate d.) Diagnosis: Microscopic examination (branched and coenocytic mycelia of pathogen

14. Branchiomycosis (Gill rot) e.) Prevention and Control: Treatments with the use of chemicals: • malachite green (0.3 mg/L for 24 h) • benzalkonium chloride (1-4 ppm active ingredient for 1 h) • copper sulfate (100 ppm for 10-30 min) • sodium chloride (3-5 %) Outbreaks = feeding of the fish should be stopped dead fish should be removed from the ponds and buried in a lime pit. Prevent outbreaks = pond should be drained, dried-out and disinfected with quicklime .

15. Branchiomycosis (Gill rot) Figure 5. Carp with branchiomycosis (gill mycosis): Photo Bayerische Biologische Versuchsanstalt (Adopted from Fish pathology by Reichenbach-Klinke's ) Fig. 6. Branchiomyces species, intravascular, located at the base of the gill arch. GA, base of gill arch . (B) Branchiomyces species; GC, gill cartilage, support structure of primary lamellae . ( Courtesy of Lester Khoo , University of Pennsylvania, Philadelphia.)

16. Ichthyophoniasis ( Ichthyosporidiosis ) a.) Causative agent: Ichthyophonus sp. ( Ichthyosporidium sp.) b .) Species affected: Groupers , trouts , flounders, herrings and cods c.) Signs: 1. Erratic swimming behavior and swelling of the abdomen. 2. Spleen , liver and kidney become swollen with numerous whitish nodules (2mm in diameter) 3. fish lose their appetite and become lean and anemic . 4. loss of apetite , emaciation, lethargy and color changes 5. Rough skin “sandpaper effect” d.) Diagnosis: Microscope examination: nodule (early cysts, develop cysts and fungal hyphae

17. Ichthyophoniasis ( Ichthyosporidiosis ) e.) Prevention and Control: no known treatment occur when fed with raw trash fish (pathogen) carefully avoided to avoid trash fish

18. Figure 7. Juvenile Pacific herring demonstrating external signs of ichthyophoniasis including pigmented skin ulcers and general emaciation. Photo : P. Hershberger, U.S. Geological Survey. Figure 8. Rainbow trout with ichthyophoniasis demonstrating petechial hemorrhages on the skin surface. Photo: Dr. Scott LaPatra , Clear Springs Foods, Inc.

19. Figure 8. Ichthyophonus sp. in Dicentrarchus labrax . Scale bars = 20 µm (Bobadilla and Pellitero , 1990) Figure 9. Characteristic macroscopic hepatic lesions of Ichthyophonus of a heavily infected yellowtail flounder. The liver is covered with small firm white, clear or yellowish nodules (I). Also note the severe epicarditis and pericarditis of the heart (II).

20. Major Fungal Disease of Crustaceans

21. Larval Mycosis a.) Causative Agents : Lagenidium spp., Sirolpidium spp., Haliphthoros spp. b.) Species affected : All Penaeus species, crabs (e.g. Scylla serrata ) c.) Signs: 1. Onset of Larval mortalities in shrimps (mortality of 20-100% within 48-72 h after onset of infection) 2. Progressive systemic mycosis accompanied by little or no host inflammatory response. Figure 3 . Lagenidium infection in crustacean larvae. A – Larva of Penaeus monodon heavily infested with the fungus. B – Infected Scylla serrata larva in brain-heart-infusion (BHI) broth after 2 days (fresh mount, 40x)

22. Larval Mycosis d.) Diagnosis: Microscopic examination (extensive, non- septate , highly branched fungal mycelia) Specialized hyphae or discharge tubes (identification of causative agent) Classification of the causative organism is dependent upon the microscopic examination of sporogenesis as follows: 1. Lagenidium – zoospores are released from terminal vesicle 2. Sirolpidium and Haliphthoros – absence of terminal vesicles; zoospores are released through discharge tubes formed by the zoosporangia.

23. Larval Mycosis Figure 4. Filaments of Lagenidium in the tail of Penaeus monodon larva (arrows ). Zoospores in a vesicle (arrowhead) are about to be released by the fungus (fresh mount, 40x ) Figure 5 . Zoosporangial development of Haliphthoros sp. by hyphal fragmentation (arrowheads=discharge tubes ) ( fresh mount, 200x)

24. Larval Mycosis e.) Prevention and Control: Disinfection of contaminated larval rearing tanks Chlorination and/or filtration of the incoming water Recommended chemicals for therapeutic and prophylactic treatments: 0.2 ppm Treflan 1-10 ppm formalin egg disinfection with 20 ppm detergent followed by thorough rinsing before hatching Salinities 7-15 ppt – control motile zoospores

25. Black Gill Disease ( Fusarium Disease ) a.) Causative agent: Fusarium solani b.) Species affected: All Penaeus species c.) Signs: 1. Appearance of black spots 2 . Infection usually starts on damaged tissues such as wounds, gills damaged from chemical treatments or pollutants, and lesions. 3.Lesions may also serve as a route of entry for other opportunistic pathogens. Figure 6. Canoe-shaped macroconidia of Fusarium sp. (fresh mount, 400x)

26. Black Gill Disease ( Fusarium Disease) d.) Diagnosis: Microscopic examination of infected tissues (canoe-shaped macroconidia ) Fusarium spp. are soil fungi. Fusarium solani - opportunistic pathogen of penaeids (stresses or overcrowding. e.) Prevention and Control: E limination 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.

27. Black Gill Disease ( Fusarium Disease) Fig. 10. Parrotfish with Fusarium infection. Note ulcer on ventrolateral aspect extending into deep musculature. (Courtesy of Scott Terrell, University of Florida, Gainesville, FL.) Fig. 11. Closer view of deep ulcer in parrotfish. (Courtesy of Scott Terrell, University of Florida, Gainesville , FL.)

28. Aflatoxicosis (Red Disease) a.) Causative agent: Aflatoxin produced by Aspergillus flavus and other Aspergillus spp. (contaminants of not-properly stored or expired feeds) b.) Species affected: Penaeus monodon or other Penaeus spp . c.) Signs: 1. Yellowish or reddish discoloration of the shrimp body and appendages. 2. L ethargic with weak swimming activity near pond dikes. 3. Soft shelling 4. Retarded growth 5. Histopathologically , necrosis in the tubule epithelium can be observed.

29. Aflatoxicosis (Red Disease) d.) Diagnosis: Confirmation is through bychemical analysis for the presence of aflatoxin in the suspected feed/ingredient . e.) 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 Figure 7 . Mass of sporangia of Aspergillus sp . on contaminated feed particles (fresh mount, 200x)

30. References: Lavilla-Pitogo CR, de la Peña LD. 2004. Diseases in farmed mud crab Scylla spp.: Diagnosis, Prevention and Control. SEAFDEC Aquaculture Department, Iloilo, Philippines, 89 p. Nagasawa , K. and E.R. Cruz- Lacierda (eds.) 2004. Diseases of cultured groupers. Southeast Asian Fisheries Development Center, Aquaculture Department, Iloilo, Philippines, 81 p. Leaño , E. M. (2001). Fungal diseases. In G. D. Lio -Po, C. R. Lavilla , & E. R. Cruz- Lacierda (Eds.), Health management in aquaculture (pp. 43-53). Tigbauan , Iloilo, Philippines : SEAFDEC Aquaculture Department . Roy P.E. Yanong , VMD. (2003). Fungal diseases in of fish . Vet Clin Exot Anim 6, pp. 377–400. Sitja -Bobadilla, A. and Alvarez- Pellitero , P. 1990. First report of Ichthyophonus disease in wild and cultured sea bass Dicentrarchus labrax from the Spanish Mediterranean area. Dis . aquat . Org ., Vol. 8. pp. 145-150.

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