The treatment of microbial infections requires a large use of antibiotics which is, partially, responsible for the appearance of resistant strains to antibiotics in dairy cows. However, many photochemical compounds, including the essential oils, are becoming interesting as potential source of natural bioactive molecules. The antibacterial activity of the studied essential oils was evaluated by aromatogram and microdilution in medium liquid. The results show that the essential oil of Thymus fontanesii has the biggest antibacterial action against all the bacterial strains comparing with the Eucalyptus oil. However, the aqueous extracts of Thymus fontanesii and Eucalyptus indicate a moderate antibacterial activity against the strains of Staphylococcus aureus. On the other hand there is no effect on Escherichia coli strains. The most strong activity inhibitory was get with the essential oil of Eucalyptus against Staphylococcus aureus strains with CMI of 0.39 μl/ml for Staphylococcus aureus ATCC and 1.562 μl/ml for Staphylococcus aureus pathogen in comparison with the essential oil of Thymus fontanesii which is more active against the Escherichia coli strains. The aqueous extract of Eucalyptus showed the best CMI and CMB against the Staphylococcus aureus strains in comparison with the aqueous extract of Thymus fontanesii. Comparative tests to the activity have been made with cefoxitin and gentamicin discs.

Repellent and acaricidal activities of eucalyptus oil, permethrin, and DEET against Leptotrombidium pallidum larvae, which are a vector transmitting tsutsugamushi disease, were evaluated under laboratory conditions using a filter paper impregnated method. The LD₅₀ values of eucalyptus oil and DEET were 0.025 and 0.018 ㎎/㎠, respectively while that of permethrin was higher than 0.2 ㎎/㎠. In the repellency test of these materials at 6.14 ㎎/㎠, eucalyptus oil gave complete repellency, and the larvae crossed the treated zone killed. But permethrin showed 60% repellency at 9.20 ㎎/㎠ and the mites croosed the zone were not killed. The percent repellency of DEET at 0.53 ㎎/㎠ was 8.3 and 2.8 times higher than that of permethrin and eucalyptus oil, respectively. The acaricidal activities of emulsifiable concentrates-pump sprayers containing the eucalyptus oil as an active ingredient were assayed. The emulsifiable concentrates containing 1% and 3% eucalyptus oil showed weak mortality at 1 hour after treatment, while all ones containing more than 6% oil produced 100% activity against L. pallidum larvae. The mortality also increased as exposure time to the concentrates increase. These results suggest that the potential of eucalyptus oil highly expected to be used as a control or repellent agent against L. pallidum larvae may be very high.