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Heartwater, a rickettsial disease of ruminants, is one of the most important diseases of livestock in Africa. This tick-borne illness can significantly decrease productivity in regions where it is endemic. It is particularly serious in nonindigenous livestock that are moved into heartwater areas; many of these animals may die. Wild ruminants can also be infected. Most wildlife species appear to carry the organism asymptomatically, but serious illness has been reported in lechwe moved into endemic areas, as well as in experimentally infected white-tailed deer.

Heartwater is readily introduced into new regions in infected animals or ticks. Known and potential host ticks are widely distributed, and can be found on a variety of animals including reptiles. On at least one occasion, leopard tortoises and African spurred tortoises imported into Florida were found to be carrying infected ticks. Once the tick vector becomes established, eradication of heartwater is difficult. One host tick, Amblyomma variegatum, was introduced into the Caribbean early in the 19th century. During the 1970s and early 1980s, this tick spread rapidly from island to island; in some cases, it may have been carried by cattle egrets. The presence of heartwater in the Caribbean increases the risk of introducing this disease into the Americas.

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Iowa State University



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