Abstract:
The cumulative effect of co-infections between pathogen pairs on the haematological response of East African Short-horn
Zebu calves is described. Using a longitudinal study design a stratified clustered random sample of newborn calves were
recruited into the Infectious Diseases of East African Livestock (IDEAL) study and monitored at 5-weekly intervals until
51 weeks of age. At each visit sampleswere collected and analysed to determine the infection status of each calf aswell as their
haematological response. The haematological parameters investigated included packed cell volume (PCV), white blood cell
count (WBC) and platelet count (Plt). The pathogens of interest included tick-borne protozoa and rickettsias, trypanosomes
and intestinal parasites. Generalized additive mixed-effect models were used to model the infectious status of pathogens
against each haematological parameter, including significant interactions between pathogens. These models were further
used to predict the cumulative effect of co-infecting pathogen pairs on each haematological parameter. The most significant
decrease in PCV was found with co-infections of trypanosomes and strongyles. Strongyle infections also resulted in a
significant decrease in WBC at a high infectious load. Trypanosomes were the major cause of thrombocytopenia. Platelet
counts were also affected by interactions between tick-borne pathogens. Interactions between concomitant pathogens were
found to complicate the prognosis and clinical presentation of infected calves and should be taken into consideration in any
study that investigates disease under field conditions.
Description:
The work was done as part of the Infectious Diseases
of East African Livestock (IDEAL) project, which is
a collaboration between the University of Pretoria,
University of Edinburgh, University of Nottingham and
the International Livestock Research Institute (ILRI),
Nairobi, Kenya.