Gauteng Smallholder Gauteng Smallholder November 2011 - Page 29

ANIMAL HEALTH All about ticks and how to control them A ll Gauteng's livestock are vulnerable to various species of ticks. There are more than 20 different tick species found in South Africa and most of them carry diseases that affect livestock, pets and, some- times, humans. The effects of ticks on sheep, goats, horses and cattle should not be underesti- mated, particularly on young animals. We might think that the amount of blood loss caused by a tick would be negligible. However the animal is likely to be carrying many more than one tick and this has been shown to cause loss of weight and to retard growth. Tick bites also cause discomfort to the animal and might even affect its appetite, which will also affect its condition. Furthermore, the bites leave small wounds which can become infected and lead to deterioration in wellbeing. These wounds also leave the animal vulnerable to infesta- tion by screw-worms, which is very difficult to eradicate. In the case of horses and cattle, infestations of ticks can damage the tail brush, which might result in the loss of the ability to wave away flies. All feedings of ticks at each stage of their life cycle are parasitic. Ticks feed only on the blood of their hosts. The ticks crawl on to their host and attach to the skin. They use a combination of cutting mouthparts which penetrate the skin and often an adhesive or glue is secreted in the saliva to aid attachment to the skin. All ticks spend most of their life cycle away from their hosts, hiding in soil and vegetation. Some ticks crawl onto vegetation and wait for their hosts to pass by. The ticks grab onto the hosts using their front legs and then crawl over the skin to find a suitable place to attach and feed. Adult ticks of the genera Amblyomma and Hyalomma are active hunters and will run across the ground to seek hosts that are resting nearby. The tick has three phases in its life cycle: larvae hatch out of eggs, then later moult to nymphs. Nymphs feed once and moult in the same way as larvae. From the nymphal moult either a female or male adult emerges. The female feeds once and lays one huge batch of eggs. Eggs of all ticks are laid in the physical environment, never on the host. She then dies. The males may take several small feeds, mate and then die. 27 In some species there is a different host for each of the phases. Immature Amblyomma hebraeum for example feed on scrub hares or guinea fowl, while the adults feed on cattle, sheep, goats and horses. Some Continued on page 29