African Horse Sickness In Lesotho

African horse sickness (AHS) has claimed the life of another horse in Lesotho, in southern Africa, raising the death toll to two and the confirmed 2004 case count to 23 as of late April. According to Dr. Malefane Moleko, Chief Veterinary Officer in the Department of Livestock and Veterinary Services in Lesotho's Ministry of Agriculture and Marketing, the latest outbreaks occurred in Maseru (the country's capital) and Qacha's Nek.

African horse sickness has been dormant in Lesotho since March 1998, but with warm evening temperatures, Culicoides immicola and C. bolitinos midges, the small flies that transmit the virus, have continued to spread the disease. The midge life cycle is only broken when the evening temperature drops below 50-59ºF (10-15ºC).

According to the World Organization for Animal Health, AHS has a mortality rate of 70-95%. The three forms of the disease are lung , heart, and mixed. The lung form is the most lethal, with clinical signs including a high fever, breathing difficulties, and frothy nasal discharge, followed by sudden death. The heart form is characterized by severe swelling of the head and eyes, bleeding from mucous membranes, and colic clinical signs. Animals with the mixed form display both the lung and heart forms.

Lesotho was free of AHS outbreaks during May 2004. For more information, see African horse sickness under Infectious Diseases at

About the Author

Marcella M. Reca Zipp, MS

Marcella Reca Zipp, M.S., is a former staff writer for The Horse. She is completing her doctorate in Environmental Education and researching adolescent relationships with horses and nature. She lives with her family, senior horse, and flock of chickens on an island in the Chain O'Lakes.

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