The impact of parasites, infections and diseases on the development of aquaculture in sub-Saharan Africa

Total African aquaculture production in 1994 amounted to 76660 metric tonne s (t). Of this, 53.8% (41211 t) was produced by five countries bordering th e Mediterranean, while the remainder (35449 t or 46.2%) was produced by 30 sub-Saharan countries. These figures highlight the low-level intensity of a quaculture in sub-Saharan Africa. A comprehensive literature search was und ertaken to gauge the extent of disease and pathogenic agents in fish and sh ellfish aquaculture in Africa south of the Sahara. The study revealed that bacterial infections as well as parasitic ectoprotozoans, cestodes, tremato des, nematodes, polychaetes and crustaceans are the most prevalent problems in African freshwater, brackish water and marine aquaculture. There have b een isolated reports of viral diseases (infectious pancreatic necrosis (IPN ), lymphocystis and spring viraema). Bacterial diseases are restricted to c ommon agents such as Aeromonas, myxobacteria and some other ubiquitous facu ltative bacteria. Saprolegnia is the most common problematic fungus affecti ng fish under culture conditions. Currently the most widely used chemicals for prophylaxis and treatment include wide spectrum antibiotic formulations ? malachite green, methylene blue, formalin, copper sulphate, salt, and sev eral organophosphates. From an aquaculture perspective it was noteworthy th at disease and parasite infestation have been poorly studied in Africa as a whole and in sub-Saharan Africa in particular (South Africa being the exce ption). It is hypothesized that this is mainly due to the low-level intensi ty of aquaculture in the region. At present the paucity of research on fish diseases in Africa is not seen as a factor that will negatively impact on aquaculture development and as such is not a target research area. Africa i s considered to be the sleeping giant of aquaculture and at the present mom ent it is relatively disease free. It is vitally important that African cou ntries take steps to safeguard this status. One method of accomplishing thi s is to restrict the importation of fishes into Africa. The importation of ornamental aquarium fish as well as hybrid and genetically improved fish st rains pose the greatest threats. The smorgasbord of fish and shellfish para sites and diseases that occur in Israel, for example, can to a large extent be ascribed to uncontrolled translocations. Every effort needs to be made to prevent a similar occurrence in Africa.