放牧牧野におけるマダニ駆除に関する生態学的研究

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The tick is known as a vector of the infectious diseases of domestic animals. The diseases are called large or small piroplasmosis. The damages with the ticks themselves in the pasture have been discussed, and various investigations have been made on the method to control the ticks, all over the world, but there has been no good result gained up to now. In Japan most of about 70% of the total area, the unutilized land, is in the mountain regions, which is being made into the pasture by employing the method which makes possible the cultivation of the land with the helps of hoofs of domestic animals. This is purposed to maintain the source of the stockbreeding. If the following trials are organized without investigating the correlation between the abiotic environments and the ecology of ecto-parasites, such as ticks, horse-flies, etc., it will be diffiicult to materilize the effective maintaning of the source in the stockbreeding. Therefore, for the effective tick control in the pasture, on the basis of the ecological characters of the ticks, I have surveyed the ecological characteristics of the tick (Haemaphysalis longicornis) in the farm of Kiyosato Educational Experimental Project (KEEP) and have experimented diurnal activity and behaviour in relation to CO₂ in the larvae of ticks, and have tested the BHC resistances in each developemental stage of the tick m laboratory, and then have carried out field tests in the farm of KEEP from May in 1966 to August m 1972. KEEP includes a new plan for turning the uncultivated land into the pasture, and producing milk and beef on a commercial basis. The investigated area is about 200 ha. in total sloping at about 10° degree and acidic soils which do not contain AI, Mg, phosphate and lime (Figs. 2・3, Table 2). Bush (200 hal), sown pasture (30ha) and pasture (50 hal are found in this area which are different from each other in climatic conditions (Figs. 1,4-29). To capture the ticks in the field, two methods were used, one is to drag the frannel (50cm x 50cm), the other is a new method which uses the rabbit as a host. The rabbits were exposed in the individual areas for 6 hours, and killed, after which the ticks leaving the corpse were collected and calculated. The rabbit method is more effective for capturing the ticks in the field than the frannel dragging method. The species of the tick in KEEP is Haemaphysalis longicornis (Table 6). The habitat of the tick is the shade and humid places with tall grasses such as Pearl grass, Japanese pampasgrass and bamboo grass, which provide grazing cattle with water places or rest places (Figs. 33・34, Tables 4・11). The period of multiplication is observed twice throughout a year; one is in the rainy season and the other in summer. The tick is found almost in the whole area in summer, but only in some particular blocks in autumn (Fig. 30). The main factor of controlling tick's dipersal is grazing cattle (Figs. 35-37, Tables 15-17). Although it is presumed that the dispersal of ticks are also caused by the small and medium-size mammals, especially wild mice such as Apodemus speciosus or Microtus montebelli, they were not available for transporting factors in the present areas (Table 12). In bush zones, especially the block 8-B, the density of ticks throughout a year was highest, where 3848 individuals were captured from one rabbit in summer (Fig. 30). In this block 8-B, the main factor of controlling tick's dispersal is grazing cattle, Hereford (Fig. 35, Table 15). Therefore, two years after cattle ceased to graze in this block, all of the ticks have disappeared. The nymph and adult are active in May and the ticks in all of the stages are found almost in the whole area in summer, but in autumn, they are restricted to some particular areas and in winter, they hybernate among the roots of grasses which are from in 0 cm to 10 cm deep in soils (Fig. 30, Tables 20・21). The larvae are selected in early winter. The female tick of this species in KEEP is capable of multiplying their offspring whithout mating which is termed "parthenogenesis" . Investigating the relationship between the vegetation and the distribution of ticks, it was observed that the larvae of tick ascend on the plants, especially Pearlgrass, Japanese pampas grass and bamboo grass, up to the 20-40 cm height and wait for the hosts(Tables 18 ・19, Figs. 33・34). For the purpose of studing the above, a measurement apparatus for recording the movement of larvae of the tick was newly developed. The structure of the apparatus is explained in the following. A red light of diameter of 1mm by a tungsten lamp is projected close to the inside glass wall of an experimental box, from a flood light projector to a flood light receptor, and the light is cut off by the tick which ascend from ground to wall or descend from wall to ground. As a result, a stimulus is caught by a flood light receptor and the stimulus is transmitted from the flood light receptor to a control box (made by Takenakadenshi K. K.) (Photos. 1・ 2), and in the control box the stimulus is changed into an electric rectangular wave with the power 500mv and the electric wave is transmitted from the control box to a recorder. And then it is recorded by the recorder (Photo. 3, Fig. 38). The behaviour of the larvae under the constant conditions in the dark, and in the light, 800-1000 Lux by the fluoresent light, at the room temperature of 20°C and 26- 28°C, it was found out that there were two peaks, the hours from 9:00 to 12:00 a. m. and from 17:00 to 24:00 p. m., in the diurnal activity of the tick larvae which ascend or descend. The organization of the behaviour of the tick larvae in the waiting for the hosts in the field, has been found out by these experimental data as shown below. They ascend on the plants up to the 20-40 cm height and wait for the hosts in the forenoon hours from 9:00 to 12:00 a. m. and in the evening descend on the mat of piled fallen leaves in case hosts do not come, waiting for the hosts. If the hosts come in the place where the ticks wait, they are attached and fed by them. On the basis of these data relating the diurnal activity of the tick larvae, the experiments were conducted on the behaviour of the tick larvae in relation to CO₂. These data have made clear that they are active in response to CO₂ and that in case CO₂ is given for 5 minutes in the experimental box, they are active, and begin to ascend or descend on the inside glass walls, and that as time passes their activity becomes gradually low, and they return to their pattern of diurnal activity (Phot.4, Figs. 43-44). On the other hand, most of damages of stockbreeding by the ticks are caused by tick as the transmitter of large or small piroplasmosis. For the purpose of decreasing the injuries by the ticks, the trials of the elimination of the ticks have been made. But it is thought that it makes the host stressed strongly to attach the host and to suck the blood by ticks themselves, and that as a result, the deterioration of the quality of beef and/or the quantity of milk is caused by the tick themselves. So, for the purpose of making clear the fact, the trials of quantifying the injuries by figures have been made. A great number of the ticks in all stages cast or put into the sack which covers an ear of a rabbit, and they suck blood for about seven days, and then after they drop off into the sack, the sack is cut off. Throughout the period of experiment, the constant volumes of food and water are given and the body weight of the rabbit is measured every day (Figs. 45-48). Based on the data, it has been made clear that about 7-8 % of the body weight of the host decreased for a week, and that the ticks made the host stressed. For the purpose of controlling the tick in the field, the BHC resistances in each developmental satge of the tick were tested in laboratory (Tables 22-23). The following results were obtained (Fig. 49, Tables 25-30). Namely, there is no significant difference in the BHC effect upon resistance between γ-BHC and its emulsion for the tick. There are some correlations between density of BRC emulsion and mortality of the tick. Mortality of the tick in 0.1% and 0.05% BRG emulsion is equal and that in 0.025% BRC emulsion is lower than the former. Therefor, the 0.05% emulsion of γ-BRC is most effective for the tick control. From the view-point of the developmental stage of the tick, it was found that the nymph is of highest resistance to low humidity for the tick. Field tests were also carried out at the block 8-B, 9 and 15 in the farm of KEEP from June in 1966 to June in 1969. About 10 1 of the emulsion of 0.05% γ-BRC per 100m² was sprinkled. It is found that the sprinkling of the emulsion of 0.05% BRC is effective for controlling the tick, and that in addition to this result, keeping cattle from grazing in the block is also effective for controlling the tick in the field (Tables 31-34). It is most effective for the tick control in the pasture and sown pasture to make the combined use of the following two methods. One is to keep cattle from grazing in the block, and the other is the use of chemicals concentratedly in the pasture, in which a great number of the ticks are found, for the purpose of controlling the larvae and adults of the ticks in the early autumn. Recently, BRC has ceased to be used completly, lest it shall be accumulated into the fat of milk and beef, but BHC is so effective to insecticide the ticks in fact. If a new chemical for the tick control is found, it must have the same effectiveness as BRC. It is impossible to control the ticks in the field if not. Therefore, considering the above, we must need to think an organic combination, the effect of chemicals which act on partially for the tick control, for keeping cattle from grazing in the block. Based on the above-mentioned, we can conclude concerning the tick control in the pasture, that we can do it effectively if we practice the elimination of the tick on the basis of the synthetic judgements of the ticks, in addition to the effective use of chemicals, and while considering the plan of keeping cattle from grazing for several years.
信州大学教養部の論文
1975-03-15

放牧牧野におけるマダニ駆除に関する生態学的研究

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