Dr. Murai Éva szerk.: Parasitologia Hungarica 22. (Budapest, 1989)

animals; Ocsa, Holstein-Friesian x Hungarian Fleckvieh x Jersey crossbreds, dairy cows {5 to 7 years old), no IBK; Apajpuszta, Hungarian Fleckvieh and crossbred cows and heifers) in August of 1985 and 1987. Body and eye counts were made by a TASCO 10x50 binoculars. Altogether 83 pairs of data were collected, on at least 20 animals per locality. Since the results from the three localities do not differ significantly, all the data were combined and processed together. The duration of face fly visits on the eyes of cattle was observed through the binoculars and clocked by a Hanimex stop-watch. Timing was made in an Independent series of observations (160 data) but possibly on the same animals which were Involved in fly counts. Another two cows (Apajpuszta, Sept. 15, 1985, Hungarian Fleckvieh) suffering from IBK were also observed (fly counts and timing) but these data were not used later (but in one respect only, see below). Our field data are summarized in Diagrams 1-4. As it appears from these data, on the average 13.6 face flies per body and 2.63 face flies per head were found with 21.9% of flies on the eyes (the most frequent values /modes/ are 13.3 , and 23.077, respectively). Diagram 4 on the duration of fly visits on eyes shows an unusual form: this histogram is - in all probability - a summation of several behavioral elements of different length of time (simple sucking and food uptake after causing mlcroleslons by their mouthparts, cf. KOVÁCS-SZ. 1987, are suspected). Half of the face fly visits Is short in duration, i.e. less than 10 seconds but one-third of the visits (56 of the total of 160) is longer than one minute. The long-staying visitors can very likely use their prestomal teeth causing mechanical damage to the conjunctive and to other parts of bovine eyes. SIMULATION AND MODEL PARAMETERS We decided to link the elements of knowledge on the role of Musca autumnalis in transmitting and causing infectious bovine keratoconjunctivitis by constructing a computer simulation model. In this study our field data and some data of the literature were used. Since we believe that the role of face flies in contamination is mainly connected with their moving, we should have operated with matrices including their transition probabilities. The only problem is that the collection of observational data enough to construct such matrices may be said to be an almost impossible task. One fly may stay (i) on infectible parts (eye, nose, urogenital parts) of the body of cattle, (II) on other parts of the body, (iii) on excrements of cattle, (iv) somewhere else in the pasture. Data sufficient for estimating the pairwise transition probabilities could be hardly gained without very large efforts so this way of work had to be given up. When constructing our model we had to canalize our effort on the eye because this is the most important part of body in IBK, As we have seen earlier, the modus (5 seconds) of measures on time spent on the eye would be misleading. The flies were arbitrarily grouped into three categories. The members of the first group stay for a very short time (1-9.9 seconds). Possibly this time is not enough for the flies to hurt the eye with their mouthparts, but they possibly transmit the bacteria. Flies in the second group spend 10 to 59.9 seconds on the eye. The members of the third group spend more than one minute on the eye and they can be suspected of causing mechanical damage to the eye.