The role of houseflies (Musca domestica) in harbouring Corynebacterium pseudotuberculosis in dairy herds in Israel

A study was conducted to assess the role of houseflies, Musca domestica L. in harbouring Corynebacterium pseudotubercolosis in dairy farms in Israel. The bacterium was isolated in June 1993 from 40 wild houseflies which had f ed on a lesion on a cow, and from 28 laboratory flies fed on contaminated m ilk from a cow infected with mastitis. The bacterium was recovered from the body surface of 10 flies (of a total of 160) 10 min after being dipped ent irely in a bacterial broth. The bacterium was recovered from the body surfa ce of 10 flies (of a total of 40) 5 min after being fed on contaminated mil k. When 110 flies were fed on contaminated sugar cubes, the bacterium was r ecovered externally from 70 flies 5 min later, and from an additional 20 fl ies 10 min after feeding. Of 110 flies, 80 excreted bacteria in saliva from 5 min to 3 h after feeding on contaminated milk. Bacteria were isolated fr om the intestine of 40 of 60 flies between 1 h and 4 h after feeding on con taminated milk. Bacteria were found in the faeces of 30 of 60 flies, betwee n 1 h and 4 h after feeding on contaminated milk. In the light of these findings, and given the fact that this species of fly has a predilection to feed on milk residues of cow teats, the authors conc luded that the housefly plays an important role in harbouring and dissemina ting C. pseudotuberculosis in dairy herds in Israel. In contrast, stable fl ies (Stomoxys calcitrans L.) are not important in the habouring and dissemi nation of the bacteria, since bacteria were not recovered 5, 10, 15, 30 min , 2 h or 24 h after membrane feeding on a mixture of bacterial broth and bl ood.