Title page for ETD etd-09182012-184202


Document Type Doctoral Thesis
Author Conradie van Wyk, Ilana
Email ilana@conradie.net
URN etd-09182012-184202
Document Title Anaemia in East African short-horn Zebu calves : field diagnosis, infectious causes and pathogen interactions
Degree PhD
Department Veterinary Tropical Diseases
Supervisor
Advisor Name Title
Prof J A W Coetzer Co-Supervisor
Prof B L Penzhorn Supervisor
Keywords
  • East African short-horn Zebu calves
  • Western Kenya
  • East African livestock
  • infectious diseases
Date 2012-09-07
Availability unrestricted
Abstract
This study formed part of the collaborative IDEAL (Infectious Diseases of East African Livestock) project, which focused on the sedentary mixed crop-livestock smallholding system in Western Kenya. This was a longitudinal study where calves were recruited at birth and followed at 5-weekly intervals until 51 weeks of age. The main aim was to investigate the total disease burden of cattle in the study area for the first year of life.

The main objectives of the study concerned anaemia as a syndrome in the calves. Anaemia can provisionally be diagnosed based on clinical signs, but a confirmatory diagnosis is based on measuring of red blood cell parameters, such as packed cell volume (PCV), red cell counts (RCC) or haemoglobin (HGB). The FAMACHA© score card, a field diagnostic test developed to detect anaemia and haemonchosis in sheep, was designed to test pallor by measuring the colour of the ocular mucosa against a colour chart. The FAMACHA© as a field diagnostic tool was validated for use in East African short-horn Zebus, using PCV as the gold standard. The red cell parameters and indices as well as white cell and platelet parameters and indices of the East African short-horn Zebu were measured by a Sysmex® automated cell-analyzer.

The age-related changes in the haematological profile of East African short-horn Zebu were investigated. The haematological profile of the study population, particularly during the neonatal period, differed from reference ranges for European breeds, both in levels and agerelated trends. These differences could not be explained by what is known about the physiology for other cattle breeds. Anaemia was a significant syndrome in the general study population based on the high incidence of anaemic episodes and the longitudinal trend in the general study population towards an anaemic state.

In a tropical environment calves are exposed to a myriad of pathogens, even from early calfhood, many of which potentially cause anaemia. The prevalence and cumulative incidence of pathogens, in particular tick-borne parasites, trypanosomes and intestinal parasites, was investigated. The variation in prevalence with age has allowed the identification of high-risk periods. The prevalence of co-infection of pathogens was also found to be considerable, in particular pathogens known to cause anaemia. The relative contribution of different pathogens to the development of anaemia was investigated through their impact on the haematological profiles of calves infected by specific pathogens. Strongyle-type nematodes and trypanosomosis were found to be the major causes of anaemia in the calves during their first year of life.

Co-infections with pathogens were shown to have a significant impact on the haematological profile of calves. In many cases the cumulative effect of, or interactions between concomitant pathogens affected the severity of clinical symptoms, such anaemia, and in turn affected the prognosis of such calves. The impact of concomitant infections also complicates any diagnostic, treatment or intervention programmes in livestock and should be considered in any study on epidemiology in livestock kept under field conditions.

© 2012 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Conradie van Wyk, I 2012, Anaemia in East African short-horn Zebu calves : field diagnosis, infectious causes and pathogen interactions, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-09182012-184202/ >

D12/4/162/ag

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