In search for low-cost, safe and environmentally benign plant-based alternatives to commercial pesticides, the efficacy of Lippia javanica aqueous leaf extracts in controlling ticks on cattle, acute oral toxicity in mice and phytochemistry were evaluated. L. javanica aqueous leaf extracts at 10% and 20% w/v were effective at controlling cattle ticks but not as good as an amitraz-based acaricide Tickbuster®. However, they can provide an effective tick control option where synthetic products are unavailable or unaffordable, particularly in remote parts of southern Africa. Peripheral blood samples collected showed no haemoparasites in treated cattle implying that animals did not suffer from clinical tick-borne diseases. The leaf aqueous extracts of L. javanica were tested for toxicity in BALB/c mice. While anecdotal evidence suggests L. javanica has low mammalian toxicity, within 48 h all mice fed with the L. javanica leaf aqueous extract at 12.5-37.5% v/v were lethargic, and overall mortality was 37.5% (n=24). Thus, despite their apparent safety, water extracts of L. javanica leaves may have deleterious health implications on humans and animals if consumed at very high doses. Many compounds have been identified from L. javanica including an array of phenolic glycosides, flavonoids and essential oils but none of these are known to have acute toxic properties.

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In response to farmer requests after milk from their herds was rejected by processors due to poor quality, a study was carried out from April to October 2011 to determine the prevalence of subclinical mastitis, associated risk factors and causative micro-organisms. Samples were collected from 195 dairy cows on 23 randomly selected dairy farms delivering milk to Isangano, Kirebe and Nyagatare milk collection centres in Nyagatare District, Rwanda. The Draminsk® Mastitis Detector was used to detect subclinical mastitis in individual cows based on milk electrical conductivity changes. Risk factors for mastitis that were evaluated included teat-end condition, cow dirtiness, breed, parity, age and stage of lactation. Relationships of these factors with mastitis status were determined using Chi-square analysis, and relative importance as causes of mastitis was assessed using logistic regression. Samples from 16 subclinical mastitis positive dairy cows were analysed to identify causative micro-organisms using Dairy Quality Control Inspection analytical kits. Subclinical mastitis prevalence was 52% across the farms. It was higher with increases in, amongst other risk factors, teat-end damage severity, cow dirtiness, and level of pure dairy breed genetics. The risk factors considered accounted for 62% of mastitis prevalence; teat-end condition alone accounted for 30%. Most of the mastitis cases (87.5%) were caused by coliform bacteria. Considering that farmers are upgrading their local Ankole cows to cross-breed dairy cows that are more susceptible to mastitis, results from this study indicate the need to dip the teats of cows in sanitisers, improve cow hygiene, and introduce mastitis prevention and control programmes.

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