Acute ill-health in sheep farmers following use of pesticides.

Background: Sheep farmers often complain of acute ill-health, known colloquially as 'dipper's flu', immediately after treating sheep with pesticides. There have been few prospective epidemiological studies to determine it's nature and incidence. Aims To determine the nature and frequency of symptoms occurring in farmers treating sheep for ectoparasites.

Methods: In a longitudinal study, farmers who planned to treat their sheep for ectoparasites were recruited. Farmers kept a symptom diary for 7 days after starting pesticide treatment. Symptoms reported on days 1-6 were compared to those reported on day 7 via the McNemar's test and with previously published literature definitions of dipper's flu. A principal component analysis (PCA) was carried out on new symptoms occurring on days 1 and 2.

Results: Of 781 farmers recruited, 352 farmers (45%) completed the symptom diary. In the 7 days after starting pesticide treatment, symptom complex reporting typically peaked on day 2, but few farmers (7 or less; <2%) were identified as having dipper's flu using literature definitions. However, PCA identified two new patterns of symptom complexes that accounted for 35% of the variance. A pyrexial factor consisted of four symptom complexes (feeling generally ill; feeling sweaty, shivery, feverish, hot or cold; feeling unusually tired; and having a headache) and a respiratory factor consisted of three symptom complexes (runny, stuffy, blocked or irritated nose; cough, shortness of breath or wheeze; and eye irritation).

Conclusions: Existing definitions of dipper's flu do not adequately describe symptoms that occur following the treatment of sheep for ectoparasites.