Bacterial infections in the early phase of Nile tilapia production in Zambia

Abstract

Globally tilapia is the third most farmed group of fish, and it is an important food source in many parts of the world. Tilapia is a fast-growing freshwater fish, which tolerates more than many other fish species in terms of environmental variabilities like changes in temperature and salinity, as well as low dissolved oxygen levels in the water. The main object of this thesis was to assess the production principles and environments in tilapia production in Zambia, including characterization of potential pathogenic bacteria in fingerlings and fry in the early stages of production. 22 bacterial isolates previously collected in Zambia, were characterized by Gram-staining and biochemical characterization with API 20 E and API 20 NE, and further analyzed using molecular methods including PCR, followed by sequencing, and combined with Maldi-Tof analyses. During our field study in Zambia, we used a structured questionnaire to collect information about production principles and routines from tilapia managers and farmers. Some potentially pathogenic and non-pathogenic bacteria were found during our laboratory work, suggesting the fish lives in suboptimal environment, and are exposed to stressors making them less resilient to disease. Increased mortality in the early phase of production may cause massive economic consequences because the entire production chain is affected. The tilapia farms we visited during our field study is still under development with little resources and economic input, producing cheap fish to the local market.