Seasonal Dynamics in Bacteriological and Physicochemical Water Quality of the Southern Gulf of Lake Tana

Proximate Composition, Microbiological Quality and Safety of Raw and Open Sun-Dried Fish Products in Lake Tana, Ethiopia

The quality and safety of fish products are crucial because poorly handled fish products can result in foodborne illnesses, spoilage, and economic losses. Data on the nutritional and microbiological quality of fish products in Ethiopia, especially in Lake Tana, is limited. This study assessed the proximate composition and microbial quality of raw and open sun-dried fish products in Lake Tana. Using the standard procedures, 60 fish tissue samples were collected and analyzed for proximate composition and microbial quality. The open sun-dried fish had significantly higher ash (10.08% ± 1.98%), fat (6.01% ± 1.59%), protein (48.76% ± 8.55%), water activity (0.7358 ± 0.0368) and salt contents (5.89% ± 3.17%) compared to the raw fish (p < 0.05). A significant difference was observed between raw and dried fish in aerobic mesophilic bacteria, Staphylococcus aureus, yeast and mold counts (p < 0.05). The mean total and fecal coliform counts were not significantly different between the raw and dried fish (p > 0.05). In raw fish, 16.6% and 83.3% of samples had total coliforms and fecal coliforms exceeding the recommended limits, respectively. Both raw and dried fish samples tested positive for Salmonella and Shigella spp. There was a strong positive correlation between water activity and microbial load (r = 0.756, p < 0.05) and also between moisture content and microbial load (r = 0.786, p < 0.05). Most of the assessed raw and sun-dried fish samples were above the international microbial specification limits, which need attention to ensure the safety of fish consumers.

Proximate composition, microbial quality and heavy metal concentration of fresh Nile tilapia fillet in Lake Tana, Ethiopia

Nowadays, consumption of fish is becoming a public health concern due to quality and safety issues. This study was designed to assess the proximate composition, microbial quality, and heavy metal accumulation in the Nile tilapia fillet at three selected landing sites in Lake Tana. Fifteen samples were collected and analyzed. The mean moisture, ash, fat, protein, salt, and water activity were 81.76%, 0.98%, 1.88%, 14.04%, 0.14%, and 0.9869, respectively. The proximate contents varied slightly among sites but were not significantly different (p > 0.05). The mean aerobic mesophilic bacteria, Staphylococcus aureus, total coliform, and fecal coliform counts were 6.30 log CFU/g, 2.91 log CFU/g, 1.51 log MPN/g, and 0.89 log MPN/g, respectively. Such high microbial loads and the high counts of fecal coliforms are indicative of poor handling practices and unsanitary processing that might lead to foodborne illnesses and economic losses. In addition, the mean concentration of heavy metals in the tissue samples decreased in the order of chromium (0.165 mg/kg) > arsenic (0.085 mg/kg) > lead (0.054 mg/kg) > cadmium (0.010 mg/kg). Except for chromium, the concentrations of the assessed metals were below the maximum permissible limits. Long-term chromium exposure, especially in its hexavalent form, can pose significant health risks like respiratory issues, gastrointestinal distress, and even cancer. Therefore, identifying contamination sources, employing proper waste management strategies, continuous monitoring of heavy metal levels, and proper fish handling practices are highly recommended to address the health implications of microbial contamination and elevated chromium concentrations.

Histopathology based study of Nile tilapia fish (Oreochromis niloticus) as a biomarker for water pollution evaluation in the southern gulf of Lake Tana, Ethiopia

In the past decade, the increasing distribution of pollutants in the aquatic environment has been observed, causing integrative effects on fish. Likewise, due to anthropogenic activities, the southern gulf of Lake Tana is an impacted region, and the production of Nile tilapia fish is reduced. For this reason, the aim of this study was to conduct a histopathological-based study of 48 Nile tilapia fishes' health status at the southern gulf of Lake Tana and aquaculture using a cross-sectional study from February 2023 to May 2023. The study evaluated the histopathology of the gill, liver, gonads, and spleen organs using descriptive statistics accompanied by a 2 × 2 contingency table and t-test analysis. During the study, different histological alterations were detected, and the numbers of fish affected by a specific histological alteration were presented as percentage prevalence; hence, from the total fish examined, hyperplasia (54.15%), followed by pigment deposits (52%), hemorrhage (50%), and immune cell infiltration (50%), respectively, were the most frequently detected alterations. However, Nile tilapias from the southern gulf of Lake Tana were 1.4 (odds ratio) times more likely to show histopathological alterations than those from aquaculture, although statistically, was not significant (p > 0.05). In addition, the study found the mean value of the fish index (95.3) and regressive indices of the gill (13.6), liver (14.8), and gonad (12.3); moreover, the inflammatory indices of the spleen organ (11.3) and mean severity grade value of the gill (2.35) and gonad (1.7) organs, respectively, were obtained from the southern gulf of Lake Tana, and all those values were significantly higher (p < 0.05) from this site as compared to the aquaculture. In general, it has been found that tilapias from the southern gulf of Lake Tana showed higher pathological severity as compared with aquaculture. Among the four target organs evaluated, liver organs were observed to be the most damaged, while gonads were the least impacted organs. Therefore, it has been concluded that tilapia fish are living in abnormal conditions, so to ensure a sustainable fishery, water pollutant sources from Bahirdar city must receive proper attention, and future studies should consider age differences, seasonal variation, and the detection of specific pollutants.

Assessing the quality of drinking water from selected water sources in Mbarara city, South-western Uganda

This study assessed the physical, chemical, and microbiological quality with emphasis on risk score, source apportionment, geochemistry, feacal coliforms and water quality index of drinking water from selected water sources. A cross-sectional study was conducted in six villages in Mbarara city, south-western Uganda. Each selected source was inspected using a WHO-adopted sanitary inspection questionnaire. Each source's risk score was calculated. Thirty-seven samples were taken from one borehole, nine open dug wells, four rain harvest tanks, and twenty-three taps. The values for apparent color and phosphate were higher than the permissible level as set by the World Health Organization and Ugandan standards (US EAS 12). The isolated organisms were Klebsiella spp. (8.11%), Citrobacter divergens (62.16%), Citrobacter fluendii (2.7%), E. coli (35.14%), Enterobacter aerogenes (8.11%), Enterobacter agglomerus (5.4%), Proteus spp. (2.7%), Enterobacter cloacae (13.5%), and Proteus mirabilis (2.7%). Twelve water sources (32.4%) had water that was unfit for human consumption that was unfit for human consumption (Grade E), Five sources (13.5%) had water that had a very poor index (Grade D), nine (24.3%) had water of poor index (Grade C), eight (21.6%) had water of good water index (Grade B), and only three (8.1%) had water of excellent water quality index (Grade A). The piper trilinear revealed that the dominant water type of the area were Mgso4 and Caso4 type. Gibbs plot represents precipitation dominance. PCA for source apportionment showed that well, tap and borehole water account for the highest variations in the quality of drinking water. These results suggest that drinking water from sources in Mbarara city is not suitable for direct human consumption without treatment. We recommend necessary improvements in water treatment, distribution, and maintenance of all the available water sources in Mbarara City, South Western Uganda.