In the period November 1, 1985 to January 31, 1986, 703 cases of giardiasis were reported in Pittsfield, Massachusetts (population 50,265). The community obtained its water from two main reservoirs (A and B) and an auxiliary reservoir (C). Potable water was chlorinated but not filtered. The incidence of illness peaked approximately two weeks after the city began obtaining a major portion of its water from reservoir C, which had not been used for three years. The attack rate of giardiasis for residents of areas supplied by reservoir C was 14.3/1000, compared with 7.0/1000 in areas that received no water from reservoir C. A case-control study showed that persons with giardiasis were more likely to be older and IntroductionWaterborne giardiasis is becoming an important public health problem in the United States: during the period from 1965-84, 90 outbreaks and 23,776 cases of giardiasis were reported. Sixty-nine per cent of outbreaks and 74 per cent of

Fenvalerate ear tags reduced fly loads on dry dairy cattle by 95 % between July and September. Fly dislodging behaviour, such as ear flicks which correlated with numbers of Musca autumnalis on the face and stamps/kicks which correlated with numbers of Stomoxys caldtrans on the legs, was also significantly reduced. There was no significant difference between the tagged and untagged groups in the total time spent grazing each day. Milk yields were not statistically significantly different, but the tagged group showed a greater increase in milk yield between lactations, of 1-45 kg/cow daily in the first 12 weeks of the lactation.

In two trials using diary heifers, in the south of England, ear-tags, containing flucythrinate, completely controlled Haematobia irritans (L). Musca autumnalis De Geer on the face were reduced by 41% using one tag and by 76% using two tags per heifer. A single ear-tag reduced numbers of Hydrotaea irritans (Fall6n) on the body by 90O/o and on the teats by more than 55~ Other minor pestering flies were similarly controlled. Control was sustained over the entire 14 weeks duration of the trials which effectively encompassed the fly season of the three main pests.Ear-flicks by the heifers were related to dislodging M. autumnalis from the face, and tail flicks to dislodging Hy. irritans from the belly. These are the two commonest species of nuisance flies and are known to carry pathogenic bacteria.A management plan intended to maximise effective use of insecticidal ear-tags while minimising risks of insecticide resistance is described.

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