A total of 8.2% of flies caught outside a broiler house in Denmark had the potential to transmit Campylobacter jejuni to chickens, and hundreds of flies per day passed through the ventilation system into the broiler house. Our study suggests that flies may be an important source of Campylobacter infection of broiler flocks in summer.

The role of volatile semiochemicals in mediating the location and selection within herds of Holstein-Friesian heifers by nuisance and disease-transmitting cattle flies was investigated using coupled gas chromatography-electrophysiology (GC-EAG), coupled gas chromatography-mass spectrometry (GC-MS), electrophysiology (EAG), laboratory behaviour and field studies. Using volatile extracts collected by air entrainment from heifers in the Netherlands, a number of active peaks were located by coupled GC-EAG for Musca autumnalis (de Geer) (Diptera: Muscidae) and Haematobia irritans (L.) (Diptera: Muscidae). Volatile samples were also collected from two heifers in Denmark shown in previous counting experiments to differ significantly in their fly loads. Coupled GC-EAG using Ha. irritans antennae revealed differences in the EAG response to the samples, with additional EAG activity in the sample collected from the heifer with the lower fly load. To identify more EAG active compounds, volatiles were also collected from 48-h-old urine by air entrainment. In total, 23 compounds were located and identified by coupled GC-EAG and GC-MS. Further electrophysiological testing of these compounds with five fly species [M. autumnalis, Ha. irritans, Hydrotaea irritans (L.) (Diptera: Muscidae), Stomoxys calcitrans (L.) (Diptera: Musicidae) and Wohlfahrtia magnifica (Schiner) (Diptera: Sarcophagidae)] showed that only some of the compounds were physiologically active across the range of flies tested. These included 1-octen-3-ol, 6-methyl-5-hepten-2-one, (Z)-3-hexen-1-ol, naphthalene, and all EAG active compounds identified from urine. Compounds showing significant EAG activity were tested for behavioural activity using a wind-tunnel designed for measuring upwind flight behaviour. At certain concentrations, 1-octen-3-ol, 6-methyl-5-hepten-2-one and 3-octanol increased upwind flight, whereas naphthalene, propyl butanoate and linalool reduced upwind flight. In field studies using small herds of heifers ranked according to their fly load, individual slow-release formulations of 1-octen-3-ol and 6-methyl-5-hepten-2-one, when applied to low and high fly loading heifers, reduced fly loads on these individuals. This study provides evidence for the hypothesis that the natural differential attractiveness within herds of Holstein-Freisian heifers, i.e. a single host species, for cattle flies is partly due to differences in volatile semiochemicals emitted from the host. It is suggested that this phenomenon applies to other vertebrate host species and their associated insect pests.

No abstract

Heifers were treated with the recommended doses of ivermectin: 0.2 mg/ kg bw by subcutaneous injection or 0.5 mg/kg bw by pour-on. An analytic procedure is described and used for the detection of ivermectin residues excreted in dung. A large amount of the higher pour-on dose was excreted during the first five days after dosing due to a more rapid distribution to intestinal contents. Later faecal concentrations after the pour-on treatment were lower than those found after subcutaneous injection. No degradation of ivermectin was detected in pats exposed in the field for up to 45 days. Ivermectin excreted in dung voided 1–2 days after both treatments significantly reduced the number of dung inhabiting larvae of Aphodius spp. (Coleoptera: Scarabaeidae), but no effect was seen in dung deposited 13–14 days after treatments. Development of cyclorrhaphan larvae was inhibited in dung deposited up to 28–29 days after subcutaneous injection treatment, but only inhibited in dung deposited up to 13–14 days after pour-on treatment. The numbers of Nematocera larvae were not affected. In a laboratory bioassay the Diptera Musca autumnalis DeGeer and Haematobia irritans (Linnaeus) suffered higher mortality in dung from heifers treated by the subcutaneous injection 13–14 days earlier than in dung from heifers treated by pour-on at the same time. After subcutaneous injection, a significant reduction in the rate of decomposition was found in dung from heifers treated 1–2 days earlier, whereas pour-on led to a delayed decomposition in dung collected up to 13–14 days after treatment.

Wild animals living close to cattle and pig farms (four each) were examined for verocytotoxin-producing Escherichia coli (VTEC; also known as Shiga toxin-producing E. coli). The prevalence of VTEC among the 260 samples from wild animals was generally low. However, VTEC isolates from a starling (Sturnus vulgaris) and a Norway rat (Rattus norvegicus) were identical to cattle isolates from the corresponding farms with respect to serotype, virulence profile, and pulsed-field gel electrophoresis type. This study shows that wild birds and rodents may become infected from farm animals or vice versa, suggesting a possible role in VTEC transmission.