Importance

Ticks are among the most important vectors of human and animal diseases caused by protozoa, rickettsiae, bacteria, viruses and even helminths of vertebrates. They rank second only to mosquitoes as vectors of life threatening or debilitating human and animal diseases. Moreover, ticks transmit a greater variety of infectious agents than any other arthropod group.

Ticks are also important as pests, affecting humans, livestock and wildlife. Apart from the discomfort they cause, these blood-feeding ectoparasites cause considerable production losses especially to improved animal breeds in the Afrotropical region. Each engorging female tick takes between 1 and 5 ml of blood depending on species and size.

Disease transmission

Only a small number of tick species are vectors of important economic diseases or toxicosis in sub-Saharan Africa. These are Amblyomma hebraeum, Amblyomma variegatum, Hyalomma dromedarii, Hyalomma truncatum, Ixodes rubicundus, Rhipicephalus (Boophilus) microplus, Rhipicephalus (Boophilus) decoloratus, Rhipicephalus appendiculatus, Rhipicephalus evertsi evertsi, Rhipicephalus zambeziensis and argasid or soft ticks of the Ornithodoros moubata/porcinus complex. Each of these ticks occurs in specific areas suitable for survival and reproduction. In cattle they transmit diseases of economic importance such as heartwater, babesiosis, theileriosis and anaplasmosis but also non-pathogenic or mild theileriosis, spirochaetosis, benign anaplasmosis, benign babesiosis and ehrlichiosis. Tick-borne diseases affecting sheep and goats are heartwater, anaplasmosis, theileriosis, spirochaetosis and Nairobi sheep disease. Tick-borne diseases that affect horses, mules and donkeys are piroplasmosis, spirochaetosis and those of pigs are porcine babesiosis and African swine fever.

Routes of transmission

Pathogens can be transmitted by the following routes / mechanisms: transovarial, transtadial, intrastadial, co-feeding, mechanical, venereal, by coxal fluid or ingestion. Knowledge of the above-mentioned is important to have a better understanding of the epidemiology and control of tick-borne diseases these pathogens cause and to control the diseases.

Find out more

• Identification of ticks: The systematics and taxonomy of ticks, the seasonal occurrence, different life cycles, tick morphology and identification and differential diagnosis of ticks of veterinary importance are described.
• Tick surveillance: Information is provided on the different collection methods of ticks, including vegetation sampling, nest/burrow sampling, tick traps and host sampling methods.
• Control of ticks: Different control strategies (chemical, biological and vaccines), principles of acaricide resistance, and the effect of tick control on endemic stability of tick-borne diseases are described, and information is provided on the different chemical products available.