Cruz-Vázquez C, Bautista HJ, Vitela MI, Ramos PM, Quintero MMT, García VZ

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ABSTRACT

The aim of the study was to study the annual distribution of the horn fly, Haematobia irritans (L.), in confined dairy cattle in the State of Aguascalientes in Mexico. Three dairy farms which had 92, 165, and 490 Holstein cows in milk production were selected at convenience. Maintenance took place in a free-pen housing dairy cow system. Throughout the study, farmers did not apply any insecticide treatment. Dairy farms were monitored weekly from February 1997 to February 1998. Ten percent of the dairy cows were selected at random in each occasion. Direct counts of adult flies, resting or feeding, over both sides of the animal body were recorded. Weekly average fly number per animal, and weekly average infestation percentage were described. In the study period, the annual distribution was seasonal; it began early spring and finished early winter (nine months) with a bimodal trend with peaks in the summer (28 July to 10 August), and in the fall (29 September to 5 October). The summer-fall period had the highest infestation, and intolerable parasitic levels for dairy cattle were observed. The diapause was present in the winter with a duration of approximately 60 days.