Safety of medical feed additives in the food chain

Praziquantel use in aquaculture – Current status and emerging issues

“…Delivery of PZQ as medicated feed in sea-cages is expected to result in the presence of PZQ in sediment ( Hormazábal and Yndestad, 1995 ). Lunestad et al (2015) reported only limited degradation of PZQ in seabed sediment over a month; a 50% reduction in PZQ levels in the top layer of sediment (<2 cm) and no reduction in a lower layer (5–7 cm). This persistence of PZQ in sediment would result in extended exposure to bottom-dwelling organisms.…”

“…Another example of PZQ use in aquaculture occurs in Norway, where it is used as an oral treatment for tapeworms in Salmonidae, such as rainbow trout Oncorhynchus mykiss and Atlantic salmon Salmo salar ( Lunestad et al, 2015 ). However, PZQ is not listed for use in fish for human consumption by all governments and its use in aquaculture is typically ‘off-label’ under special veterinary justification.…”

“…have been recognised as a problem in salmon farming in Norway for decades ( Bristow and Berland, 1991a , 1991b ; Mitchell, 1993 ; Saksvik et al, 2001a , 2001b ; Noga, 2010 ), and PZQ is used widely in Norwegian fish farming; however, there is only limited information on its application ( NIPH, 2016 ). The recommended dose is 5 mg/kg BW for 2 days orally in feed ( FHF, 2006 ; Lunestad et al, 2015 ). The low dose rate, and implied low dietary inclusion level, indicates palatability should not be an issue when treating this parasite.…”

“…Adverse effects have not been reported following injections in several fish species at therapeutic concentrations from 5 to 25 mg/kg BW ( Foreyt and Gorham, 1988 ; Lorio, 1989 ; Poynton et al, 1997 ; Bader et al, 2018 ); however, mortality has been recorded in S. lalandi post-administration of a 100 mg/kg BW intravenous dose ( Tubbs and Tingle, 2006b ). Several fish species, such as Atlantic salmon and yellowtail kingfish, show no toxic effects when exposed to PZQ levels several fold higher than the recommended dose ( Lunestad et al, 2015 ; Forwood et al, 2016a ), and no haematological or biochemical indices indicated stress in S. lalandi intubated with 500 mg/kg BW ( Forwood et al, 2016a ).…”

“…Platyhelminths, along with a variety of other organisms are present in seabed sediments. This is an environment where PZQ has been shown to accumulate, resulting in the potential for extended exposure to bottom-dwelling organisms ( Lunestad et al, 2015 ). Bottom-dwelling organisms are important in organic decomposition and sediment leaching, and toxic effects on these organisms can detrimentally affect these processes.…”