RESUMO
Essential oil was extracted from Ocimum suave Willd leaves by water distillation and tested for repellency effectiveness against Anopheles gambiae adult mosquitoes. The percentage yield of the essential oil was 0.2%. Six concentrations of O. suave essential oil were applied on human skin of four volunteers, and the repellency effectiveness which was analyzed by PoloPlus (LeOra software version 1.0, 2002-2014), revealed promising RC50, RC75, RC90 and RC99 with their confidence limits as 0.1161 mg/cm2 (0.02067 - 0.1767 mg/cm2), 0.2823 mg/cm2 (0.22328 - 0.3654 mg/cm2), 0.4319 mg/cm2 (0.35226 - 0.58862 mg/cm2) and 0.98934 mg/cm2 (0.54731 - 0.99972 mg/cm2), respectively. O. suave essential oil exhibited high Anopheles mosquitos’ repellency effectiveness which merits further scientific attention for the development of natural repellents for the control of malaria and other mosquito borne diseases. These findings provides a scientific evidence and base for formulation for further mosquito repellency semi-field and field trials for the development of cheaper and affordable new mosquito repellent product(s) to meet human healthcare needs in the prevention and control of malaria and other mosquito transmitted infections.
RESUMO
Background: There is currently an increased demand and consumption of bottled water in Tanzania especially among the middle and high income earners as it is generally perceived to be pure, clean and of good quality. This has led to the sale of different brands of bottled water on the Tanzanian market. Due to increased demand and consumption of bottled water in Tanzania, there has been a growing concern about the microbiological quality of this product. The objective of this study was to assess the physico-chemical quality parameters and microbial contamination level with thermotolerant fecal coliform bacteria commercial bottled water Dar es Salaam city in Tanzania. Materials and Methods: This cross sectional study was done in randomly selected ten different commercial brand of bottled water available in commercial market of Dar es Salaam city in Tanzania. Tap water from Dar es Salaam Water Supply Company (DAWASCO) was also sampled for comparison. Fecal coliform were enumerated by the membrane filtration and commercial field testing DelAgua®kit. The physicochemical examination of the water samples was done to determine pH, turbidity and Total Dissolved Solids (TDS) of the water samples using a Hach spectrophotometer (Hach Company, Loveland, Colorado, USA). Results and Discussion: All samples of bottled water (100%) analyzed did not show the presence of thermotolerant faecal coliform bacteria and thus meet the World Health Organization (WHO) acceptable value of zero cfu/ml. All the surveyed brands of bottled water were safe for drinking as they were devoid of any thermotolerant fecal coliforms bacteria. Tap water from DAWASCO revealed thermotolerant fecal coliforms contamination with mean CFU counts of 4.0/100ml. Coliform organisms found in tap water in this study were above the recommended levels by regulatory agencies such as Tanzania Bureau Standard (TBS), International Bottled Water Association (IBWA), Food and Drug Administration (FDA), United States Environmental Protection Agency for (USEPA), World Health Organization (WHO) and the European Community (EC). The overall mean results of the physicochemical parameters of bottled water brands and tap water studied were within the recommended limits by TBS and WHO. Conclusions: The absence of thermotolerant fecal coliform bacteria in the bottled water is indicative of safety for public consumption. Tap water from DAWASCO is unfit for human consumption and it needs to be treated to render it safe for human drinking. Physicochemical parameters revealed that the pH, TDS and turbidity were within the required levels by TBS and WHO. This indicates that, the manufacturers of bottled water brands and DAWASCO are conforming to the TBS and WHO standards on physicochemical requirements for drinking water.