Abstract
The tropical and sub-tropical climate in Africa favours multiplication and maintenance of tick vectors and transmission of various pathogens to cattle. Key challenges including acaricide resistance, policy issues, transboundary animal movements, and inadequate veterinary services compromise effective control of tick-borne diseases (TBDs). This chapter discusses important host, pathogen, climatic, and management factors that impact the control of TBDs among cattle in Africa, and which affect the productivity and overall contribution to economic development. The economic losses in cattle production attributed to tick infestation and TBDs in Africa are also reviewed. The use of a sustainable integrated control approach, including vaccination, strategic tick control, surveillance for acaricide resistance, and multi-stakeholder involvement is also evaluated.
TopBackground
Important Tick-Borne Diseases of Cattle in Africa
Tick-borne diseases that mostly affect cattle in Africa are anaplasmosis, heartwater, babesiosis and theileriosis. Anaplasmosis is the most prevalent TBD of cattle, mainly caused by Anaplasma marginale, which is distributed in tropical and sub-tropical regions in all six continents (reviewed by Aubry and Geale, 2011). Anaplasma centrale causes a mild form of anaplasmosis, and is used as a live vaccine to protect against A. marginale infection (reviewed by Kocan et al., 2010). Heartwater, caused by E. ruminantium affects cattle in almost all of sub-Saharan Africa as well as on the islands of Reunion, Mauritius, Madagascar, Grande Comore and São Tomé, and several islands in the Caribbean (Allsopp, 2010). In Africa, bovine babesiosis is caused mainly by B. bigemina and B. bovis (De Vos et al., 2004). Babesia bovis causes the more virulent form of the disease, while B. bigemina is more prevalent on the continent. Theileriosis is commonly caused by Theileria parva, which affects cattle in eastern central and southern Africa (reviewed by Bishop et al., 2020), and was recently found for the first time in West Africa (Cameroon) (Silatsa et al., 2020). It was also reported in the Comoros Island (De Deken et al., 2007). Theileria parva causes East Coast fever (ECF) (Lawrence et al., 2004b), Corridor disease (Lawrence et al., 2004a) and January disease (Lawrence et al., 2004c).
Key Terms in this Chapter
Epidemiology: Is the study of the distribution and determinants of health-related states or events in specified populations.
Two-Host Tick: Tick that remains in one host for the larval and nymphal stages, drops off to molt an adult, and seeks a second host on which to take another blood meal and copulate.
Prevalence: Is a measure of disease frequency. It quantifies the number of existing cases (animals with a disease) in a population at a point in time or during a period of time.
Carrier: An apparently healthy animal which is infected with a pathogenic organism. The carrier can transmit the organism to other animals which may then develop disease.
One-Host Tick: Tick that completes all its molts on the same individual host animal.
Acaricide: Chemicals used for controlling ticks.
Host: Is an animal that harbours an infectious agent.
Incidence: Is a measure of disease frequency. It quantifies the number of new cases (animals newly acquiring a disease) in a population at risk of developing the disease over a given period of time.
Seroprevalence: Frequency of animals with antibodies to a specific parasite.
Antigenic/Genetic Diversity: Variation in the genetic composition or within the antigen-encoding genes.
Three-Host Tick: Tick that seeks a new host animal for a blood meal after each of its three molts.