Environmental pathogens, such as Escherichia coli and Streptococcus uberis, are
currently the major cause of mastitis within dairy herds. This leads to severe financial
losses, lower production rates and deterioration of the general health of the herd. E. coli
mastitis is becoming a major threat to high milk-producing dairy herds. This is because of
its increasing resistance to antibiotics, rendering antibiotic treatment regimes against E.
coli infections mostly ineffective. The aim of this study was to develop a method to select
mastitis causing E. coli isolates for the formulation of effective herd specific vaccines.
Two methods, namely a genotyping method (Random Amplification of Polymorphic DNA;
RAPD) and an antibiogram based method, were used. A dairy farm milking
approximately 1000 Holstein cows in the Darling area, Western Cape Province, was
selected for this study. The study was conducted over a period of 48 months and mastitis
samples were analysed for mastitis pathogens. Antibiogram testing (disk diffusion
method) and an in-house developed RAPD analysis method were used to analyse the E.
coli isolates. A total of 921 milk samples were analysed from which 181 E. coli isolates
were recovered. The number of all other common mastitis pathogens combined was 99
isolates (Streptococcus uberis 18, Streptococcus dysgalactiae 46, Streptococcus
agalactiae 1, Staphylococcus epidermidis 21, Arcanobacterium pyogenes 13). All E. coli
isolates, except for one, were resistant to at least three antibiotics. Antibiotic variance
profiles were also highly erratic. The RAPD analysis revealed high levels of
polymorphisms and clear epidemiological trends were observed over time. No similarities
in the variance profiles between the antibiotic variance data and phylogenetic data were
observed. Formalin inactivated autogenous vaccines were produced containing E. coli
isolated from the herd. The vaccines were formulated using the RAPD or antibiogram
data of the E. coli isolates. A total of 5 vaccines were formulated using RAPD data (Rvaccines)
and one vaccine was formulated using antibiotic variance data (A-vaccine).
The RAPD formulated vaccines were more effective than the antibiotic variance
formulated vaccine. After each R-vaccination, the number of E. coli mastitis cases
declined within the herd. The A-vaccinations seemed to have had no effect, which lead to
a rise in E. coli mastitis cases. RAPD analysis on new emerging isolates was able to
detect genetic variation from vaccine strains, which in turn facilitated the formulation of
new updated vaccines with higher effectiveness than the previous vaccine. Mastitis data
prior to and after the vaccination period revealed significant higher incidences of mastitis
in the herd than during the vaccination period. This study demonstrated that sufficient sampling practices coupled with a reliable genotyping method, resulted in the formulation of updatable vaccines which were highly effective in controlling E. coli mastitis within the herd. / Thesis (M Environmental Sciences)--North-West University, Potchefstroom Campus, 2012
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/11080 |
| Date | January 2012 |
| Creators | Goosen, Daniël Johannes |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.0022 seconds