Flies

Haematobia irritans infestation (Australia)

Flies in grazing cattle include biting flies, gadflies and nuisance (non-biting) flies. Cattle flies damage their hosts by annoyance and blood loss, thus causing decreased production.

The transmission of causal agents of diseases is an additional risk. They constitute an economic problem for grazing cattle in tropical regions throughout the year and in zones with moderate climate the during summer months. Transmission of the causative agents of specific diseases.

This has been proved in the case of FMD, IBR/IPV, brucellosis, etc. Hydrotaea irritans is the most important transmitter of summer mastitis (pyogenic mastitis, pasture mastitis, Holstein udder disease), an acute infection of the udder in dry cows or heifers in Northern and Central Europe due to the combined action of several bacteria. The face-fly (Musca autumnalis) is considered to be the major transmitter of infectious keratoconjunctivitis (bovine enzootic keratitis, pinkeye), a disease of cattle caused by Moraxella bovis.

Biting Flies

Haematobia irritans

The most common cattle fly is the horn fly (Haematobia irritans) and in Australia / Southern Asia the buffalo fly (H. irritans exigua). Infestation rates of several hundred flies per cow have been observed, in tropical regions several thousand. The flies live permanently on their hosts, leaving only for oviposition or when disturbed.

Sites of predilection are the base of the horns and the back. Another species, H. stimulans, which is encountered in European countries, occurs in smaller numbers of not more than 200 flies per cow. Stomoxys calcitrans, the typical stablefly, is only occasionally seen on grazing cattle. Biting flies feed on the blood of their host. Horn flies suck blood 12-24 times daily, Stomoxys calcitrans feeds twice a day on average. The mean daily blood loss per H. irritans is 14.3 mg.

Gadflies

Damalinia bovis (cattle hair coat)

The gadflies which are up to 25 mm long tend to attack grazing cattle on hot sultry days. They suck up to 1 ml blood per bite, and the bites often result in allergic reactions. Most prevalent are gadflies of the genera Tabanus, Pangonia, Haematopota, Chrysops and Hybomitra.

Nuisance Flies

The most common nuisance flies in grazing cattle are the face-fly (Musca autumnalis), the head-fly (Hydrotaea irritans) and other species of the genera Hydrotaea and Morellia.

In the vicinity of barns the common housefly (Musca domestica) and the little housefly (Fannia canicularis) are also encountered. For most of the time the flies swarm around the livestock or stay nearby on grasses, faeces, etc.

Nuisance flies feed on protein-rich secretions from natural body orifices such as nose, mouth, teat orifices, from skin wounds and bleeding bites left behind by gadflies and biting flies.

They can also inflict small scratch wounds themselves on thin mucous membranes and healing wounds using tiny teeth on their proboscis.