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Epizootic ulcerative syndrome affecting fish in the Zambezi river system in southern Africa
  1. T. G. Andrew, PhD1,
  2. K. D. A. Huchzermeyer, BVSc, MSc, MRCVS1,
  3. B. C. Mbeha, Mbeha, BVSc, MSc, DLSTHM2 and
  4. S. M. Nengu, MSc3
  1. 1 Department of Ichthyology and Fisheries Science, Rhodes University, PO Box 94, Grahamstown, South Africa
  2. 2 Department of Animal Health and Production, P Bag 0032, Gaborone, Botswana
  3. 3 Department of Wildlife and National Parks, PO Box 131, Gaborone, Botswana
  1. Correspondence to Dr Andrew


In late 2006, diseased fish of a variety of species began to appear in the Chobe and upper Zambezi rivers in southern Africa. In April 2007, investigations showed that the levels of pesticides and heavy metals in the tissues of the fish were very low, discounting pollution as an underlying cause for the disease. However, histological evidence showed that the disease closely resembled the epizootic ulcerative syndrome caused by the oomycete Aphanomyces invadans, a serious aquatic pathogen that has been isolated from freshwater and estuarine fish in Japan, south-east Asia, Australia and the usa since the 1970s, but not previously recorded in Africa.

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