Vector Control

The control of the vector of Bluetongue, Culicoides midges, can partly be achieved by management measures such as modification of the habitat (storage of manure apart from animals, dry-off of ponds) or keeping the animals indoors during peak hours for night-flying insects (at night, especially at dawn). The use of insecticides is however inevitable.

Insecticides

Targeted application of adulticides with known low mammalian toxicity (e.g. the synthetic pyrethroids) in and around animals housing and directly to the target animals themselves are favored over broad scale aerial application.

Treatment of housing with insecticides is important as ruminants are bitten by female Culicoides midges in housing as well as at pasture. Application of larvicides to Culicoides breeding sites is also suggested.

Ectoparasiticides that target Culicoides

The control of Culicoides in ruminants has previously been neglected as they were not known to be vectors of disease. Most insecticides have instead targeted flies and tabanids which usually attack the head and upper body of ruminants. Culicoides, however, prefer biting along the sides of the belly and just above the claws. It is thus vital that insecticides which are poured along the backline of animals reach these target areas in sufficient concentrations to kill Culicoides.

Butox^® 7.5 is a pour on containing the synthetic pyrethroid, deltamethrin, it has proven to be effective for protecting cattle and sheep against Culicoides bites. Some systemically applied ectoparasiticides may also be effective at killing biting Culicoides.

Advantages of reducing Culicoides bites in cattle and sheep

• The risk of Bluetongue transmission is reduced.
• By killing female Culicoides midges the amount of possible progeny in the surroundings of ruminants are reduced.
• Treatment early in the season helps to minimise midge populations around farmed ruminants.