Comparative efficacy of different insecticides in the treatment of cattle hypodermosis in north-eastern Algeria.

The efficacy of different drugs (microdose of ivermectin, doramectin and moxidectin at the recommended doses and topically applied rotenone) against the first, second and third instar larvae of Hypoderma bovis and H. lineatum was studied in cattle in the El Tarf area (northeastern Algeria). Before performing the efficacy trials, the life cycle of the warble fly was studied at the slaughterhouse between July 1993 and June 1994. This survey revealed that both species of warble fly were present in this area: L1 larvae of H. lineatum were found around the oesophagus between August and January, whereas L1 larvae of H. bovis were observed around the spine from November until March. Warbles were present under the skin from the end of October until May. The nymphal phase took place between February and May. As a result of this study the authors recommend applying chemoprophylaxis (treatment against L1) in September. This work also confirmed the excellent efficacy of avermectins and milbemycins against the three instar larvae of Hypoderma sp. under the field conditions prevailing in Algeria. Rotenone has a lower efficacy (95%) which is limited to the second and third instar larvae. However, this drug appears useful in dairy cattle.