Globally, ticks are second to mosquitoes in terms of veterinary and public health importance. A study carried out in the country recently indicated that although most farmers could describe the symptoms of the main tick-borne diseases, they cannot accurately identify the tick vectors of the ailments. A better understanding of the ticks would thus assist in control and reduction of diseases
They are blood-sucking external parasites of most livestock and sometimes human beings. They have eight legs and thus more related to spiders than insects. Apart from being transmitters of diseases, they also induce illnesses such as sweating sickness and tick paralysis. Besides that, they puncture the skin of animals thus reducing the value of hides and skins as well as creating a favourable environment for bacterial invasion. Further, ticks suck a lot of blood leading to anaemia and death.
Ticks are classified as soft or hard depending on their backside covering. Apart from the body texture, the two families differ in their feeding and reproductive patterns, behaviour and body functioning, among others. Ticks are a problem in the warm areas like the tropics and zones that are permanently cold do not have difficulties with ticks.
The early stage of a tick (larva) has six legs like insects but the later stages (nymphs) and adults have eight. In the absence of food, ticks can survive for some months. By their body marking/colouring, one can suspect the kind of disease that the tick will transmit.
Members of this group prefer poultry and pigs especially in the warm environment. High infestation with the parasites leads to retarded growth, anaemia and losses through death. The parasites are a serious problem of chicken that are sitting on their eggs for purposes of incubating/hatching them. In such cases, the bird might be found dead on the eggs. Some of the diseases transmitted by soft ticks include fowl cholera and tick paralysis. In the absence of a favourable host, these ticks can also feed on human beings, posing a challenge to individuals that house birds at night for security purposes.
While the various development stages of the soft ticks hide in the host or dwelling places of their host, the various growth stages of hard ticks are either on or off their host. Thus, this group is further subdivided into three categories depending on whether all the four developmental stages take place on the same animal (one host), two animals (two host) or three animals (three host). The two and three host can be the same animal hosting the ticks two or three times. These stages are eggs, larva, nymph and adult.
Mating takes place mostly while on the host but it can also happen on the ground. Hard ticks of great economic importance in Kenya include brown ear tick, red legged tick, bont tick and blue tick
a) Red ear tick
The parasite transmits East Coast Fever (ECF), a disease of great economic importance not only due to the high death rates of affected animals but also the cost of treating the disease. Red ear tick is a three host parasite with adults, nymph and larva feeding on different hosts. The adult attaches to ears, while the nymphs are mostly found on the ears, head, legs and feet. The larva prefers head, neck, legs and feet. The ticks are brownish in colour and adults are medium in size (3-5mm).
b) Bont legged tick
This is a one host tick which is advantageous in that application of tick control agents eliminate all the cycles of the parasite thus it is easier to clear the pest on a farm. The tick’s legs are brightly coloured with red and pale rings hence the name.
The tick is of major economic importance in cattle but also transmits diseases to other livestock and dogs. Major clinical signs of Babesiosis, the disease transmitted by the tick include bloody (red) urine, anaemia and jaundice (yellowish coloration of the mucus membranes). Calves less than six months old and recovered animals are resistant to the disease.
c) Bont tick
The body and legs of this tick are brightly coloured. It transmits organisms that cause heart water disease in cattle, sheep and goats. The clinical signs of the disease include circling and nervous signs. The disease is easy to treat but difficult to diagnose.
d) Blue tick
The tick is grey or bluish in colour and is a vector to the organisms that cause the disease anaplasmosis in cattle, sheep and goats. The disease is characterised by constipation, rumen inactivity, anaemia and lack of appetite.