Yellowtail kingfish diseases

Yellowtail kingfish diseasesDr Matt Landos BVSc(HonsI) MANZCVS(Aquatic Animal Health Chapter)Future Fisheries Veterinary ServiceMatty.landos@gmail.com

Health Management• Identify infectious diseases– Outbreak investigation (Field + Lab)• Implement monitoring• Undertake clinical trials/novel treatments• Define non-infectious disease syndromes• Implement improved husbandry• Collaborate with feed companies• Research areas of unknowns

Bacterial diseases• Photobacterium damselae ssp damselae– Reported in other fish to cause systemic disease– Identified from swabs from sick YTK duringmortality spikes– Identified as a component of the gut flora

IP vaccination location

Vaccine CRC study-PSFC NSW DII• No significant impact on growth• No reduction in survival in 30 days postvaccination• No evidence of serious tissue reactionaffecting product quality at injection site• Commercial trial results indicated improvedsurvival in vaccinated pen

Vaccination location-IP

Parasitic disease- gill fluke• Zeuxapta seriolae• Gill damage• Anaemia• Requires bathing with hydrogen peroxide• Praziquantel bath also efficacious• Requires constant load monitoring to assistwith bath timing• Fallowing critical for control

Parasitic disease- skin fluke• Benedenia seriolae• Cause severe skin irritation• Growth reduction and mortality• Requires hydrogen peroxide bathing• Timing of baths critical to control• Fallowing critical for control

Juvenile skin flukes recruit onto eyes

Parasitic disease- blood fluke• Paradeontacylixspp.• Uncertain ofclinical impact• Eggs observedin freshpreparations ofgill• Fallowing criticalfor control

Weight loss- YTK enteritis syndrome

YTK normal intestine

Thickened intestinal wall- full length

Reddened gut lining- thick wallchronic disease

Lymphocytic enteritis

Gut protozoa

Complex enteritis- players• Coccidia-like parasites• Myxidia-like parasites• Cryptosporidia-like parasites• Bacterial adhesion• Soyabean meal• Other potential diet factors

Proliferative lymphocytic enteritis

Sloughing enterocytes and protozoa

Similarities to European enteromyxum• Experimental treatment with coccidiostats– Amprolium + salinomycin• More research required to document– Species of protozoa– Efficacy of treatments– Environmental impacts– Precursors to infections

Proliferative enteritis- occluding gutlumen

Renal myxosporea

Parasitic copepods

Epitheliocystis

Parasitic disease- Others• Liver microsporidia• Muscle myxosporea (eg Kudoa sp.)• Migrating cestodes

Nutritional disease- SBM enteritis• CRC-SARDI research identified that highsubstitution rates resulted in reducedthickness of gut mucous• Potentially causing:– Increased risk of bacterial adhesions to gut lining– Increased permeability of gut wall– Increased presentation of enteric antigen to fishimmune system– Dysfunctional liver lipid metabolism

Canola oil substitution- SARDI CRC• Led to change in liver coloration• Reduced growth• May not provide sufficient long chain fattyacids

Nutritional disease- SBM enteritis• Some species of fish appear to be sensitive toSoya Bean Meal in their diet– Saponins and antinutritional factors implicated• Processing can remove some of these antinutritionalfactors, creating different soyaproducts such as Soya Protein Concentrate (SPC)• YTK may not have a high tolerance for SBMsubstitution in diets• Effects of substitution can be slow to be observed

Nutritional unknown- FM FOsubstitution• Fish have net requirement for long chain fattyacids that are only found in the fish meal andfish oil components of diets• Substitution in diets can result in a relativedeficiency• Deficiency can result in poor immunity,general increase in disease, poor gut mucosalimmunity

• Sensitive fish to grow• Many challenges indisease control• Many unknownsrequiring research• Species growthpotential and marketopportunities remainattractiveConclusions