Potential Public Health Risks of Pathogenic Bacteria Contaminating Marine Fish in Value Chain in Zanzibar, Tanzania

Aims: Marine sourced food, to a large extent, provides protein and nutrients to people of Zanzibar where 85% of Zanzibar population consume fish at least five times a week. This study was carried out to investigate the safety of marine foods consumed in Zanzibar.

Study Design: A longitudinal study design was used to investigate variations in colony forming units along the value chain of fishermen, vendors and consumers. A cross sectional study design was used to study the profile and number of microbial pathogens. A repeated cross sectional study was used for value chain analysis.

Place and Duration of Study: The study was carried out in Zanzibar, Tanzania between August 2014 and June 2015.

Methodology: A total of seven hundred and eighty fish samples were collected seasonally through the value chain from fishermen, through vendors to ready-to-eat food (consumer), between 2014 and 2015 with the aim of assessing bacterial contamination (colony forming units (CFUs), identify prevalent bacterial species and investigate if the pattern of CFUs is influenced by ambient temperatures, rainfall or human activities. The study was also intended to investigate antibiotic sensitivity profile of some of the prevalent bacteria. Sample collection was done from 8 different landing sites. Moreover, an additional 60 samples were collected from one recreation site.

Results: It was observed that bacterial load tended to increase in January-March season when ambient temperatures were high and fell down during the cool season July-September even though the difference was not statistically significant (p>0.05). Bacterial loads were higher in fish collected from vendors than in fishermen or consumers, again the difference was not significant (p>0.05). Bacterial load of fish from consumers in a recreation site (Forodhani) were highly significant (p<0.0001) compared with the rest of the counts in the value chain. There was no evidence that anthropogenic activities like tourism affected bacterial load. However, fish collected from town based landing sites tended to have higher bacterial loads which could be attributed to sewage disposal and human activities. Thirty one bacterial species were identified and many of them were of public health importance. Antibiotic disc sensitivity tests revealed existence of multidrug resistance among 21% of Staphylococcus aureus isolates.

Conclusion: To improve the hygiene situation food safety rules must be enforced, food tracing system must be strengthened and mass awareness for improvement of hygiene standards be implemented to all fish stakeholders.