Screening of commercial milk samples using ELISA for immuno-epidemiological evidence of infection by the cattle grub (Diptera: Oestridae).

Pasteurised and ultra high temperature (UHT)-treated milk were tested over the period November 1997-February 1998 in order to evaluate the applicability of an hypodermosis ELISA test on commercial milk samples. Milk samples from six dairy companies were analysed and the development of anti-Hypoderma antibodies recorded for the period from September 1998 to June 1999. For one dairy (no. 3) bulk milk samples were also obtained from the tankers, transporting milk away from the farms, and analysed; the results were compared to the parasitological status of the cows whose milk had been collected on the farms. Out of 32 pasteurised samples tested, 23 were positive, exceeding the cut-off (22%), while 9 samples were negative. UHT milk was always negative. The antibody levels in milk samples from four of the six companies were highest during January and decreased gradually during February to May 1999. The bulk milk samples also had high antibody levels and 47.2% of milk producing cows had lesions of hypodermosis. It was concluded that testing commercial milk for antibodies is an efficient way of detecting the presence of hypodermosis in cattle, especially in those countries for which no data on this disease are available.