The sudden appearance of chytridiomycosis, as the cause of amphibian deaths and population
declines in several continents suggests that its etiological agent, the amphibian chytrid fungus
Batrachochytrium dendrobatidis, was introduced into the affected regions. However, the origin
of this virulent pathogen is unknown. Efforts were directed to determine the occurrence of
chytridiomycosis in Africa, whether the disease had been introduced into South Africa in recent
years and how wild frog populations were affected by infection. A chytridiomycosis survey of
2,300 archived and live specimens involving members of the Pipidae family in sub-Saharan
Africa, as well as a number of unrelated frog species in South Africa was conducted by
histological diagnosis of skin samples. The epidemiological evidence indicated that
chytridiomycosis has been a stable endemic infection in southern Africa for 23 years before any
positive specimens were found outside Africa. The occurrence of chytridiomycosis in South
Africa can be described as widespread both in terms of geographical distribution and host
species and generally infection is not associated with adverse effects at the individual or
population level. It was proposed that the amphibian chytrid originated in Africa and that the
international trade in the African clawed toad Xenopus laevis that commenced in the mid 1930s
was the means of dissemination. A risk assessment of the X. laevis trade demonstrated that
chytridiomycosis could spread through this pathway and culminated in the development of a
management protocol to reduce the risks of spreading disease through this animate commodity.
Initial comparative genetic analysis of B. dendrobatidis strains isolated from South African frogs
with a global set of 35 strains, suggests that analysis of a more geographically diverse set of
southern African strains is needed before this line of argument can support or reject the "out of
Africa" hypothesis. / Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2005.
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/860 |
| Date | January 2005 |
| Creators | Weldon, Ché |
| Publisher | North-West University |
| Source Sets | North-West University |
| Detected Language | English |
| Type | Thesis |
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