Seasonal dynamics of Amblyomma hebraeum ticks on goats in the Mnisi Area (Mpumalanga), South Africa. Towards a sustainable tick control policy.

Abstract

The area of Mnisi (Mpumalanga), South Africa is a heartwater endemic area. Heartwater is a disease of all domestic ruminants, caused by the rickettsia Ehrlichia ruminantium, transmitted by ticks of the genus Amblyomma. Due to a mortality rate up to 90%, heartwater limits import possibilities and development of lifestock. Also direct effects of the ticks, like inflammation of the skin and abscesses resulting in lameness are found to be a problem in the Mnisi area. This study was performed in March and April 2014, as a continuation of previous studies performed by F. van der Steen and S. Busser in June, July and November 2013. 2884 ticks were collected from 169 goats in 17 different villages in the area of Mnisi, South Africa. The predominant tick was Amblyomma hebraeum, followed by Rhipicephalus (B.) microplus. By performing a PCR/RLB , infection rates of E. ruminantium could be detected. 47% of the nymphs and 7,8% of the adults turned out to be positive for E. ruminantium, indicating the presence of heartwater in the Mnisi area. The presence of clinical cases of heartwater is likely, since the occurrence of pedaling movements in goats before death were described by the residents. Since this research was performed in June and July 2013, November 2013 and March and April 2014, some things can be said about the seasonal dynamics. Only 23 adult Amblyomma ticks were found in the winter months (June and July 2013), whereas the summer months (November 2013) peaked with 522 adults. Most larvae were present in winter and the number of nymphs did seem to correlate to different seasons. Some seasonal fluctuations were observed, however, for the implementation of a sustainable intervention plan, more research in the remaining months is required.