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The carrier status of sheep, cattle and African buffalo recovered from heartwater
1UF/USAID/Zimbabwe Heartwater Research Project, Causeway.
Insights
Sheep, cattle, and African buffalo can carry heartwater disease (Cowdria ruminantium) long after recovery. Transmission occurred via southern African bont ticks that fed on recovered animals as nymphs.
Area of Science:
- Veterinary Medicine
- Infectious Diseases
- Parasitology
Background:
- Heartwater, caused by Cowdria ruminantium, is a significant tick-borne disease affecting livestock in Africa.
- Understanding carrier states and transmission dynamics is crucial for disease control.
Purpose of the Study:
- To determine the duration of the carrier state for Cowdria ruminantium in sheep, cattle, and African buffalo.
- To investigate the transmission efficiency of Cowdria ruminantium from recovered hosts to ticks.
Main Methods:
- Sheep, cattle, and African buffalo were experimentally infected with Cowdria ruminantium.
- Recovered animals were exposed to southern African bont ticks (Amblyomma hebraeum) during their nymphal stage.
- Ticks that fed on recovered animals were then used to attempt transmission.
Main Results:
- Sheep, cattle, and African buffalo remained carriers for 223, 246, and 161 days post-recovery, respectively.
- Transmission of Cowdria ruminantium was successfully achieved using adult Amblyomma hebraeum ticks that had fed as nymphs on recovered hosts.
- These findings contrast with previous studies that used different transmission methods.
Conclusions:
- Livestock can act as long-term carriers of Cowdria ruminantium, posing a continued risk for disease spread.
- The nymphal stage of Amblyomma hebraeum is capable of acquiring and transmitting Cowdria ruminantium from recovered hosts.
- Effective control strategies must consider the prolonged carrier status of infected animals and specific tick transmission routes.
Abstract:
Sheep, cattle and the African buffalo (Syncerus caffer) were shown to remain carriers of heart-water (caused by Cowdria ruminantium) for long periods after recovery; 223, 246 and 161 days, respectively. Transmission was achieved using adults of the southern African bont tick (Amblyomma hebraeum) that had fed as nymphs on recovered animals. Our findings differ from those of other workers who attempted transmission using nymphs that had fed as larvae on recovered animals or with blood from recovered animals.