Did you know that ticks can cause energy loss in animals through blood loss, toxicosis, reduced appetite, and physical damage? In this Ask Afrivet article, Dr Stefan Steyn, technical and regulatory veterinarian for Afrivet Technical and Training Services, shares information on various tick species, their distribution, life cycles, associated diseases, and methods of control.
Parasites. The word conjures up images of loss and unnecessary baggage. Upon seeing a tick, do we consider them sucking money directly out of our livestock? If you consider that for one visible bluetick, there are up to 147 of its family hiding on the animal.
In production, the farmer fights a battle for energy. Ensure that enough energy is consumed, digested and turned into a product. By reducing the energy lost, production increases and the happier the producers and consumers.
Ticks cause energy loss directly through blood loss, toxicosis, anorexic effect (limited eating) and physical damage to the animal. Indirect losses are due to diseases that the ticks transmit.
Sustainable tick control is aimed at reducing the tick burden on the animal as well as the environment by disrupting the life cycle of the parasite. The number of hosts for the various stages of the ticks is important for control to be effective.
1. One host ticks
- African Bluetick (Rhipicephalus decoloratus)
- Pan-tropical Bluetick (Rhipicephalus microplus)
These ticks have a short life cycle of two months (three generations per season). To develop from eggs to adults takes three weeks on the same host. They are active from September to June, but activity in warmer parts of the country will be all year round. It overwinters as eggs hatch in the spring and attach to their host leading to a high burden on the animals in autumn. They are found on the underside and side of the body and rarely in the ears and under the tail.
Diseases they carry are African Redwater (African bluetick), Asiatic Redwater (Pantropical bluetick), gall-sickness (anaplasmosis) and decreased appetite (anorexic effect) associated with tick burden.
Acaricides are used to control tick burdens. Due to the short lifecycle on one host, it is easy to select acaricide-resistant ticks, therefore strategic control is important.
Animals should be treated in early spring, 10-14 days after the first rains. This reduces adults during the autumn peak. Another treatment is done in autumn to reduce the eggs on the veld.
During active months, treatment is usually repeated every 2-3 weeks until the tick burden is at a suitable level. For systemic treatment (injectables) to be effective, tick attachment is needed, and tick-borne diseases can still be transferred.
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2. Two host ticks
Bont-legged tick (Hyalomma sp.)
The bont-legged ticks have alternating coloured bands on their legs. The primary hosts include cattle, sheep and goats. The secondary hosts for the immature ticks are birds and rodents. Multiple host ticks have longer lifecycles and fewer generations per season but lay considerably more eggs.
Depending on rainfall, larvae will be active from May to July, nymphs from June to August and adults from November to March. They are usually seen around the anus, between the hooves, the underline and the tip of the tail.
Diseases associated with Hyalomma sp. include gall sickness, Crimean congo haemorrhagic fever (deadly to humans) and sweating sickness in calves. The long mouth parts cause wounds, abscesses and contribute to screwworm infestations. Acaricide treatment during the active period with a repeat treatment every 7-14 days according to the burden and then spot-treatment can be used for control.
3. Host ticks
Bont tick (Amblyoma hebraeum)
These ticks have a colourful back plate and long mouthparts. They are mostly found in the northern and eastern parts of the country with high temperatures and rainfall. It is not present in open grassland. The lifecycle is between 5 months and 3 years because the intermediate stages survive on secondary hosts.
The immatures will actively hunt and attach for 7-14 days. The male tick occupies the host for 2 – 5 months and attracts the females. She attaches and engorges over 7-14 days and drops off after mating. She lays up to 18 000 eggs. One female can suck 5ml of blood. The larvae are active in the late summer to autumn, nymphs in the winter to spring and adults peak in the summer. In the coastal areas, all three stages will be found all year round.
On cattle the adults are found on the hairless areas, nymphs around the feet and legs and the larvae on the head, muzzle, feet, legs and neck. On sheep, they favour the hairy area behind the hooves, the loins, axilla, sternum and around the anus. Mature ticks attach to the lions and underside of goats, whilst the nymphs and larvae will attach to the feet and legs.
Larvae are also found in the ears of goats. Heartwater is the most important disease they carry. Control is done every 7-14 days depending on the burden and spot treatment might also be needed.
Karoo paralysis tick (Ixodes rubicundus)
This little tick is found in the semi-arid interior of the country, it has long mouth parts and a rusty-coloured body. It feeds on sheep, goats and cattle. They can be found along the underside of the body, neck and upper parts of the legs.
The population usually spikes between April and May after a sudden wet, cold spell. The secondary hosts for the immature stages are small mammals. The disease is caused by a toxin a large number of female ticks excretes while feeding. A quick-acting contact acaricide is used as control similar to other multi-host ticks. Avoid grazing southerly sloping rocky outcrops during the autumn and winter.
South Africa has numerous important tick species with very specific distribution. Knowing which ticks occur on your farm and how and when to treat them, from larvae to nymph will assist in better production and less money spent on dips and delay acaricide resistance in ticks.
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