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Insecticide-treated nets for the protection of cattle against Muscinae and Stomoxyinae were evaluated using four identical pens in Kumasi, Ghana, 2005. Two pens served as controls: pen A as negative control and pen C as a positive control containing two zebus and no netting protection. Pens B and D had two zebus each: B was protected with an untreated net (1 m height) while D had the same but deltamethrin-treated net with a persistency attaining 9 months. Nuisance fly densities were weekly monitored using mono-conical traps outside each pen at distances of 20-30 m. No Glossinidae were detected in an otherwise suitable habitat and fewer than ten Tabanidae per catch were recorded. Insect attacks were counted twice per week with photos of selected body regions. Video footages of each animal allowed recordings of defensive movements during 30 s. For the first 3 weeks, mean outside catches were highest around B and C with, respectively, 9.0 and 8.0 insects per trap per day compared with catches outside A and D with 1.8 and 3.3 insects. Catches increased sharply around pens B and C with, respectively, 155.7 and 172.8 insects during week 4 and following, while outside pens A and D significantly fewer insects (11.8 and 7.3) were caught. Pictures of selected body regions showed significantly fewer attacking insects inside pen D, leading to significant nuisance reductions. Feed-uptake and resting was undisturbed, contrasting with relentless disturbance of animals in pens B and C. Protecting confined cattle with a treated net prevented attacks by nuisance insects and reduced their densities.