Levamisole triggers immune factors in fish

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A study of a drug normally used as an anti-helmintic has shown that it can affect the immune response of Turbot.

Levamisole, a synthetic imidazothiazole derivative, has historically been used to treat worm infections in mammals, but new research has suggested that it may have immune-stimulating properties in Turbot.

The study by Spanish scientists, which has just been published in the International Journal of Immunopathology and Pharmacology, is one of the first to study the effects of the drug upon fish, and the first of its kind for Turbot.

Oral doses of levamisole at doses of 500mg/kg of dry food (D1) and 250mg/kg of dry food (D2) were fed over a two week period and the fish were sampled to record the effects of the drug.

The findings show that the drug did have an effect on the immune system in all fish - but could act as a stimulant or depressant depending on the dose and immune factor in question.

The authors wrote: "Specific growth rate was higher in the medicated groups than in the control (C), but the difference was statistically significant only for D1 fish at day 49 p.t. The leucocytes/thrombocytes ratio was significantly higher in D1 than in C fish at 14 days p.t., but decreased subsequently.

"At most samplings, the percentage of the circulating lymphocytes was lower and that of the progranulocytes was higher in the medicated fish than in the C ones.

"The percentage of fish with high haemotopoietic activity in the kidney was clearly higher in D1 and D2 fish than in C ones at some sampling points. The respiratory burst activity of blood leucocytes was significantly higher in D1 fish than in C ones in all samplings, except at day 77 p.t. when control fish experienced a rebound effect.

"In all medicated fish, an initial increase of such activity was observed, followed by a further decrease. Their serum peroxidases followed a contrary pattern, with a decrease in the second sampling and a subsequent and non-significant recovery, a situation also observed for serum lysozyme and complement."

Levamisole is sometimes used as a wormer for fish.

Anecdotal evidence suggests that the drug is a possible cure for a condition in Clown loaches, Chromobotia macracanthus, known as Skinny disease.

It is not known whether the apparent positive effects of levamisole upon this condition are due to the drug's anti-helmintic effects or its possible effects upon the immune system.

For more information see the paper: Alvarez-Pellitero P, Sitja-Bobadilla A, Bermudez R, Quiroga MI (2006) - Levamisole activates several innate immune factors in Scophthalmus maximus (L.) Teleostei. International Journal of Immunopathology and Pharmacology. 2006 Oct-Dec;19(4):727-38.