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June 2012
Contents / home
Hornbills get taste of the wild
International Year of the Rhino
DIY: Build a bat box
Holiday courses
Biodiversity Youth Symposium
Community produce animal food
Debunking myths around owls
Air Force knee deep in mud!
NZG display draws crowds
Solving wildebeest dilemma
Tick-borne disease mystery
Inspiring aspirant vets
ZooClub in scientific mode
Science going places
Talkin' about takins
Conservation Grapevine
 

Solving the mystery of tick-borne diseases

 
  Tick-borne diseases can have a devastating impact on livestock production.
 
  Tick-borne diseases play an important role in the local economy as they impact negatively on the economic well-being of both communal and commercial farmers in South Africa.
 
  An NZG study undertaken on tick-borne diseases is aimed at sequencing the complete genomes of three Anaplasma marginale parasites originating from South African cattle. The genome sequence data will make it possible to identify parasite-specific targets that can be used for the development of diagnostics, drugs and vaccines.
Tick-borne diseases can have a devastating impact on livestock production. Chief among these are anaplasmosis, babesiosis and ehrlichiosis, which cause illness and high mortalities in cattle.

Bovine anaplasmosis, the most prevalent of these diseases, is caused by the parasite Anaplasma marginale, which has a worldwide distribution. In South Africa, a large number of cattle mortalities are due to tick-borne diseases, and it is estimated that more than 99% of the cattle population is at risk of contracting bovine anaplasmosis.

There are still limited tools available for the prevention of anaplasmosis. By far the most recommended approach for controlling ticks and tick-borne diseases in South Africa is by integrating the strategic use of acaricides (the pesticides used for killing the ticks) and the application of vaccines.

However, more than 90% of farmers believe that the dip wash is not effective in killing the ticks. As a result, farmers complement the government dipping service with their own initiatives, which include spraying with conventional acaricides, using household disinfectants (such as Jeyes fluid) and manual removal of ticks.

Major setbacks associated with the use of conventional drugs include the presence of residues in milk and meat, and the development of chemical-resistant tick strains.

Impact on the economy

From an economic point of view, tick-borne diseases play an important role in the local economy as they impact negatively on the economic well-being of both communal and commercial farmers in South Africa. There is a dire need for increased research efforts aimed at controlling or eliminating this disease.

On account of genetic variability derived from gene mutations and various environmental issues, genomes of parasitic organisms can differ from strain to strain in countries. This was observed in previous studies which reported a considerable genetic and biological heterogeneity among strains within A. marginale. Therefore, studying the genetic relatedness among A. marginale strains originating from various countries is important in virulence and vaccine development studies.

The main objective of a study undertaken on tick-borne diseases at the National Zoo is to sequence the complete genomes of three A. marginale parasites originating from South African cattle. The genome sequence data will make it possible to identify parasite-specific targets that can be used for the development of diagnostics, drugs and vaccines.

Collaborative efforts

The project is undertaken in collaboration with Professors Jasper Rees and Abdalla Latif, who are based at the Agricultural Research Council and Onderstepoort Veterinary Institute in Pretoria respectively, and Dr David Herndon from Washington State University in the USA.

Dr Senzo Mtshali and Dr Sibusiso Mtshali, Research and Scientific Services Department, NZG


 
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