African and Asian blue ticks – African and Asiatic redwater and tick-borne gall sickness
African farmers are constantly aware that ticks and tick-borne diseases can cause major problems in their herds. Ticks have a profound and negative impact on profitable animal production, causing enormous losses, both economical and physical.
Ticks vector (provide pathways or access for transmission) a number of bacterial, viral and protozoal diseases in cattle, horses, small-stock and game animals.
Heavy tick infestations mean that a number of ticks are taking up the animal’s blood which leads to anaemia and creates injuries at attachment sites.
These lesions provide gateways for further infections and add pressure to a compromised immune system.
To conquer the enemy, let us first know him. I encourage every stockman, and woman, to become as informed as possible about one of his greatest enemies – the tick and its accompanying diseases.
The African blue tick (Rhipicephalus decoloratus) transmits African redwater through a protozoal parasite, and tick-borne gall sickness through a bacterial parasite. Actually the tick is not blue except when it appears as an engorged female prior to dropping off.
Blue ticks prefer cattle but will feed on horses, donkeys, sheep and goats.
The blue tick is a one-host parasite which means that the various stages of its life cycle (larva, nymph, adult) take place on a single host animal.
When the adult female is full of blood (engorged) she drops off the animal and lays her eggs. It takes about five weeks for the larva to hatch and climb onto a fresh host.
Obviously there could be a number of generations of blue tick in one year. When temperatures fall the hatching is delayed. When it gets warmer the larvae (seed ticks) wait on grass and other vegetation, literally in their thousands, for animals to brush past so that they can attach.
Engorging ticks are infected through the blood of a redwater- infected animal or a carrier animal. The redwater parasite passes through the egg and larval stages and is transmitted to the host animal by the nymph.
This parasite can actually survive through several generations of blue tick, without the tick being re-infected.
Redwater causes high fever (40°C – 41,5°C), anaemia (loss of red blood cells), loss of appetite, drop in milk production, jaundice, abortion and death.
Tick-borne gall sickness is caused by the transmission of a bacterial parasite through the male blue tick as it migrates from animal to animal, rather than through the female.
The symptoms of tick-borne gall sickness are anaemia, fever, weight loss, pale gums and eye membranes, breathlessness, difficulty in walking, jaundice and constipation through lack of rumen activity.
Asiatic redwater is more virulent than African redwater but the symptoms are the same with anaemia, jaundice and red urine.
Cerebral redwater is indicated when animals develop nervous symptoms.
The tick does not retain the parasite as it does with African redwater.