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Mycoses: Molds and Fungi. Introductory Comments  Fungi are members of the Kingdom Thallophyta  main characteristic: no chlorophyll  responsible for.

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Presentation on theme: "Mycoses: Molds and Fungi. Introductory Comments  Fungi are members of the Kingdom Thallophyta  main characteristic: no chlorophyll  responsible for."— Presentation transcript:

1 Mycoses: Molds and Fungi

2 Introductory Comments  Fungi are members of the Kingdom Thallophyta  main characteristic: no chlorophyll  responsible for a range of serious and economically important diseases in teleosts  no photosynthesis = no energy pathways = parasitic existence  famous members: icthyoparasites

3 Fungi Regularly Parasitic in Fish

4 Subphylum Eumycota  The Eumycota are true fungi, having several subdivisions  most pathogens are found in the Mastigomycotina (a subdivision of the Eumycota)  they have either a motile sexual stages (e.g., Saprolegnia) or non-motile asexual stage (Achlya)  the Zygomycotina, another group of true fungi, have no motile phases, but are still significantly pathogenic  of the Mastigomycotina, the most important pathogens are the Oomycetes

5 Class Oomycetes  First fish fungal infection 1748 (Arydon)  They produce a motile biflagellate spore (easy dispersal)  Also produce a thick-walled zoospore by the fusion of two gametes; thus, oospore and their name  usually manifested as hyphae

6 (1) Saprolegniasis  Four Orders, but most significant fish pathogens are within Family Saprolegniaceae  Saprolegniasis is the term used to describe infection with Saprolegnia parasitica-declina complex  It is typically external, affecting skin and gills, sometimes eggs

7 Saprolegniasis  As mentioned, the adult form is a mass of filaments known as hyphae  the mass is called a mycelium (looks like a wad of cotton in the water)  hyphae are unique in that they are non- septate (no divisions)  the asexual biflagellated zoospores are thought to initiate most infections

8 Saprolegniasis: life cycle

9 Saprolegniasis  Ecology: ubiquitous, most surface fresh waters, limited to no greater than 2.8 ppt salinity. (Treatment options?)  Can live on dead or live matter, affect only fish which have been compromised in some way: 1. suppression of immune system (unfavorable temps) 2. injury to skin (trauma) 3. spawning or precocious sexual maturity (thickened epithelium = more mucus) 4. no seasonal (temperature) restrictions to infections with eggs

10 Saprolegniasis  Clinical signs: gray-white lesions on skin  lesions start small and circular: spread  can damage internal organs  ALL fish susceptible!!  Unfertilized eggs can be attacked by hyphae (water hardening)

11 Saprolegniasis  Control: good management techniques  Treatment:  Malachite green-topical (not approved)  Bath: 1-2 mg malachite/litre (30 - 60 min.)  Formalin: Bath: 0.15 to 0.25 mls/litre (60 min.) approved, not as effective…why not just try salt!!

12 Saprolegniasis  More treatments…  Potassium Permanganate  Chloramine T  Methylene blue  Acetic acid (as a dip @ 5% up to 1 minute)

13 Saprolegniasis: hyphae

14 Saprolegniasis


16 mycelium

17 Saprolegniasis

18 Fish eggs with Saprolegniasis

19 (2) Branchiomycosis  This disease is commonly referred to as “gill rot”  due to massive necrosis of gills  Branchiomycosis sp. fungus invades gill blood vessels  either B. sanguinis (only in gill blood vessels); carp, goldfish  or B. demigrans (grows from blood vessels to tissue); bass, pike, striped bass

20 Branchiomycosis  Epizootiology: sudden on-set, rapid course, high mortality (within two days sometimes), overall mort’s = 30-50%  usually when temps above 20 o C  Why? High organic loads, algae, high temps, high density  transmission: probably horizontal from other necrotic gills (spores)

21 Branchiomycosis  Clinical features: disease course so fast that fish are dead before any signs; fish go off feed, school at surface, become sluggish  later: necrotic patches on gills (much clubbing, fusion of lamellae)  Histopath: hyperplasia of gill epithelium, fusion of lamellae, massive necrosis  Control: treatment ineffective due to rapid on-set; strict hygiene, remove dead fish, don’t overfeed, fertilize, crowd

22 Branchiomycosis

23 Fungal Disease (3): Ichthyophoniasis (Zygomycotina)  Originally found by Bruno Hofer in trout in 1893, called disease “the staggers”  caused by Ichthyophonus hoferi  thick, fungus-like resting spores  found in most cold water marine fish populations  disease transmitted orally  it is an obligate fish pathogen: life history varies from host to host

24 Ichythophoniasis  Life cycle complicated: produces large number of endospores and resting spores in most internal organs  Clinical Features: hyphae are not visible externally, can affect up to 70% of population if fungus is in epizootic years  Histopathology: gray-white lesions of organ, organ atrophy  Control: disease transmitted orally  Don’t feed infected fish to fish (some people feed raw marine fish offal to hatchery fish)

25 Ichythophoniasis


27 Ichthyophoniasis (I. hoferi)

28 Fungal Disease (4): Aspergillomycosis  Members of the Fungi Imperfecti  “Fungi imperfecti” = no sexual stage  Associated with genus, Aspergillus  Ubiquitous; involved in decay  Byproducts of degradation of feeds = aflatoxicosis

29 Aspergillomycosis  Recently discovered in farmed fish (1983), common in Tilapia  Pathology: abdominal distension, darkening of color, lethargy; ascites  Look for hyphae in liver, spleen, kidney, intestine, swim bladder  Epizootiology: mortalities of at least 20% of stock

30 Shrimp Mycosis: Lagenidium  This disease largely caused by Lagenidium callinectes or Sirolpidium sp.  Two fungal agents can cause rapid mortality of entire tank  fungi have similar life cycles, producing hyphae which spread throughout the body  major signs: dead or moribund larvae show obvious hyphae, death in 3-5 days if untreated

31 Larval Mycosis: Lagenidium  Epizootiology: unknown, possibly from broodstock, previously infected batches of larvae, contaminated source water; spread by motile zoospores  Diagnosis: simple hyphal structures on infected animals  Control: Treflan @ 10 to 100 ppb; Treflan unstable in water, must be “dripped” in or re-applied every 5-8 hrs; disinfection of tank and apparati

32 Lagenidium callinectes

33 Shrimp Mycosis: Fusarium sp.  Fungi affecting adults (fungi imperfecti)  Causes “fusariosis”  Largely associated with broodstock, particularly of Farfantepenaeus japonicus and Litopenaeus stylirostris  L. vannamei appears fairly resistant

34 Fusarium sp.  Fusariosis is a problem when…  shrimp are typically older  cuticle wounded  improper sanitation  Major Signs: melanized (splotches)  often found on tips of appendages

35 Fusarium sp.  Mortality rates of infected shrimp vary due to complex relationship between host, fungus and secondary bacterial infection  stress + infection = mortality (esp. shipping)  Transmission: Fusarium is naturally-occurring fungus of decaying organic matter, produces non-motile infective spores (macroconidia)  infection is passive through wound, hyphae penetrate underlying tissues

36 Fusarium sp.  Diagnosis: presence of lesions in broodstock or adults, demonstration of hyphae  Control Strategies: no practical treatment, prevention a matter of proper husbandry, sanitation, adequate facilities  Avoid rough handling  Remove infected broodstock, adults

37 Fusarium sp.

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