Quaglio - Parasitic Diseases Flashcards
What are the common parasitic diseases affecting fish?
- Whirling Disease (Myxobolus cerebralis)
- Eye Flukes (Diplostomum spp.)
- White Spot Disease (Ichthyophthirius multifiliis, “Ich”)
- Swim Bladder Nematode (Anguillicola crassus)
- Cestode Infections (Triaenophorus crassus)
These diseases can significantly impact fish health and aquaculture practices.
What is Whirling Disease and its causative agent?
Caused by Myxobolus cerebralis (a myxosporean parasite). Affects cartilage in salmonid fry, causing deformities and blackened tails.
What are the symptoms of Whirling Disease?
- Erratic, spinning swimming behavior (“whirling”)
- Skeletal deformities (e.g., bent tails, spinal curvature)
- Blackened tail tips and poor growth
How is Whirling Disease transmitted?
- Spores released into water from infected fish
- Tubifex worms act as intermediate hosts
- Fish ingest actinospores from the environment
What is Diplostomum spp. and its associated disease?
A trematode (fluke) causing Eye Fluke Disease. Larvae encyst in the eye lens, leading to cataracts and vision loss.
What are the symptoms of Eye Fluke Disease?
- Cloudy or opaque eyes
- Blindness in severe cases
- Reduced ability to feed or avoid predators
What is White Spot Disease (“Ich”) and its causative agent?
Caused by the protozoan Ichthyophthirius multifiliis. Characterized by visible white cysts on skin and gills.
What are the clinical signs of White Spot Disease?
- White, raised cysts on the skin and gills
- Gasping at the surface and increased mucus production
- Flashing behavior (scraping against surfaces)
How is White Spot Disease transmitted?
- Free-swimming theronts released from mature cysts infect new hosts
- High water temperatures accelerate the lifecycle
How is Ich controlled in aquaculture?
- Raise water temperature to interrupt the parasite’s lifecycle
- Use treatments like formalin, copper sulfate, or potassium permanganate
What is Anguillicola crassus and the disease it causes?
A parasitic nematode infecting the swim bladder of eels. Causes Swim Bladder Disease.
What are the symptoms of Swim Bladder Disease caused by Anguillicola crassus?
- Thickened swim bladder walls
- Impaired buoyancy control
- Secondary infections due to tissue damage
How is Anguillicola crassus transmitted?
- Eels ingest infected intermediate hosts (copepods)
- Direct transmission through ingestion of nematode larvae
What are cestode infections in fish?
Caused by larval tapeworms (e.g., Triaenophorus crassus). Encyst in muscle tissues, causing visible white cysts and weight loss.
What are the symptoms of cestode infections?
- Weight loss and reduced growth
- Visible white cysts in muscle tissues
- Skeletal muscle damage in severe cases
What is the lifecycle of Triaenophorus crassus?
- Eggs released into water from adult worms in piscivorous fish
- Copepods ingest coracidia larvae
- Fish eat infected copepods, allowing larvae to encyst in tissues
How are parasitic infections diagnosed in fish?
- Clinical examination for external signs (e.g., cysts, lesions)
- Microscopic analysis of skin and gill scrapes
- Histopathology to confirm internal infestations
What are the common laboratory methods for identifying parasites?
- Wet mounts of tissues for microscopic examination
- Staining techniques (e.g., Giemsa stain)
- PCR for specific parasite detection
How do water quality parameters influence parasitic infections?
- Poor water quality increases stress and susceptibility
- High temperatures accelerate parasite life cycles
What biosecurity measures help prevent parasitic diseases?
- Quarantine new fish stocks
- Disinfect equipment and water systems
- Monitor and maintain optimal water quality
What are fungal-like parasites and their significance?
Includes organisms like Aphanomyces invadans (Epizootic Ulcerative Syndrome). Cause severe ulcerative dermatitis and systemic infections.
What is the treatment for Epizootic Ulcerative Syndrome (EUS)?
- Broad-spectrum antifungal treatments
- Improve water quality and reduce stress
What role do intermediate hosts play in parasitic life cycles?
Many parasites require intermediate hosts (e.g., copepods, Tubifex worms). Essential for completing their lifecycle and infecting fish.
How do parasites impact fish growth and reproduction?
- Parasites cause nutrient loss and energy diversion
- Lead to stunted growth, reduced reproductive output, and mortality
How does “flashing” behavior indicate parasitic infection?
Fish scrape against surfaces to relieve irritation from ectoparasites. Common in infections like Ichthyophthirius multifiliis.
What is the impact of Diplostomum on fish populations?
- Causes vision impairment, making fish more vulnerable to predation
- Reduces feeding efficiency and growth
What are the characteristics of nematode infections in fish?
- Include species like Contracaecum
- Encyst in visceral organs or swim bladder
- Cause inflammation and tissue damage
How are parasitic infections treated in aquaculture?
- Use of antiparasitic drugs (e.g., formalin baths, praziquantel)
- Management practices like regular water changes
What is “Ich” commonly referred to, and why is it significant?
Known as “White Spot Disease.” One of the most widespread and economically significant parasitic infections in aquaculture.
How do parasites contribute to secondary bacterial or fungal infections?
- Damage tissue barriers, creating entry points for opportunistic pathogens
- Increase stress and reduce immune responses in fish
