New disinfectant for marine finfish eggs

As the egg surface is a favourable substrate for bacterial growth good hygiene is important in marine hatcheries is important in marine hatcheries in achieving higher survival rates in marine hatcheries. Rather than apply the routine immersion technique site disinfection in the egg incubators was examined as handling of eggs can cause damage and can incur large losses.
Pyceze (Bronopol 50% W/V in an inert carrier to 100%W/V, Novartis Animal Vaccines Ltd) is licensed in the and elsewhere for the treatment and prevention of fungal infection in farmed, fertilized salmonid eggs, and in Atlantic salmon. Bronopol, in addition to being a fungicide, is also a potent bactericide and has been widely used as a preservative in health care, cosmetic products, and as a disinfectant of potable water.
Disturbance of fish eggs in the early stages may be damaging and handling of eggs should be minimised. Therefore bath treatment of eggs in incubation units in situ may provide a more effective daily dosing system and may reduce the requirement to handle eggs.
Haddock eggs were stocked undisinfected, in 75 l standard cylindrico-conical incubation units at commercial stocking densities (up to 1 kg haddock eggs per unit). After 30 minutes acclimation the water flow was stopped and aeration provided. Pyceze was added to give a concentration of 50 mg l-1 bronopol and eggs left for 30 mins before recommencing the flow. Aeration was maintained to ensure adequate mixing. This procedure was followed in a control treatment with no Pyceze. This disinfection routine was applied once daily for 8 days. Moribund eggs were removed daily before disinfection. Survival of disinfected eggs, calculated from non-viable eggs removed from the incubator throughout the incubation period, was 63.2%, compared with 35% for untreated, indicating the benefit of the disinfection. Daily disinfection resulted in a 100-fold reduction in bacterial colonies compared with undisinfected eggs.

Visual assessment of bacterial colonisation revealed marked difference in appearance between treatments. Haddock eggs treated daily with 50 mg l-1 bronopol showed a smooth and ‘clean’ chorion. Typical haddock eggs from the untreated batch displayed a ‘hairy’ growth on the chorion.
Pyceze has been shown to be an effective a disinfectant of marine finfish eggs, producing higher survival rates. Pyceze and is a Prescription Only Medicine (POM). in the UK for the treatment and prevention of fungal infection in farmed, fertilized salmonid eggs, of Atlantic salmon, Therefore use with eggs intended for on-growing for human consumption is a medicinal use and subject to regulation. The indication described here is outwith the product data sheet (`off label`) and subject to The Medicine (Restrictions on the Administration of Veterinary Medicinal Products) Regulations 1994 as amended. This means that the use of Pyceze as described in this article may only be authorised by a veterinary surgeon.