Trends in udder health and emerging mastitogenic pathogens in South African dairy herds

Abstract

The aim of this study was to retrospectively analyse the results of milk samples obtained from South African dairy herds during the period 1996 to April 2007 in order to identify possible trends in isolates of microorganisms and their pathogenicity under field conditions. Milk samples were obtained from 7 of the 9 provinces in South Africa where there are low numbers of dairy cows. Although there is scientific limitation to a country wide survey, such as the variation in herd size, management skills, parity, milk yield, milking frequency and other parameters, the size of this database helps to give a fair indication of general udder health in South Africa. Cytology and routine bacteriology were performed on 379 000 milk samples of lactating cows and bacteriology on 11 946 samples from non-lactating cows. According to the results obtained, mastitis did not decrease in South Africa over the test period. The prevalence of mastitis and teat canal infection was lowest in 2002. Mastitis and teat canal infection increased from 2002 to 2006 from 8.1 % and 24.1 % to 15.4 and 30.0 % respectively. The percentage of mastitogenic pathogens isolated from cows over these years also varied. Previously unknown or almost eradicated mastitogenic pathogens such as αβ haemolytic Staphylococcus aureus which is thought to be of human origin, Streptococcus agalactiae and Enterococcus canis were responsible for numerous mastitis outbreaks seen in the test samples. Coagulase-negative staphylococci were the most frequently isolated bacteria in milk samples from both lactating and dry cows, followed by Staphylococcus aureus and Streptococcus agalactiae. Although Staphylococcus aureus remained the principal mastitogenic pathogen in South Africa, owing to its chronic nature and resultant economic losses, most cases of mastitis were caused by coagulase-negative staphylococci. This finding increases the importance of coagulase-negative staphylococci (formerly described as a minor pathogen) significantly. Isolations of Streptococcus agalactiae peaked between 2000 and 2005 and decreased again by 2007. Coagulase-negative staphylococcal isolates increased from 2002 and were still on the increase in 2007. Streptococcus agalactiae, Streptococcus uberis and Enterococcus canis were isolated more frequently from milk samples of lactating cows compared with dry cows, while Enterococcus faecalis was isolated more frequently from dry cow samples

Phenotypic, antimicrobial susceptibility profile and virulence factors ofKlebsiella pneumoniaeisolated from buffalo and cow mastitic milk

“…4,24,32,33 By contrast, Klebsiella mastitis outbreaks are only occasionally reported in Europe, 34,35 although a high rate has been reported in a study from the Alps in France (92%). 36 Our low prevalence rates are closely related to the findings in Canada 37 and significantly lower from several other global surveys on the prevalence of Klebsiella intra-mammary infections in Europe, Asia and South America 38-41 which have reported values ranging between 33.5% and 45.0 % and in Africa [42][43][44][45][46][47][48][49] which have reported a prevalence of 15-16%. The absence of Klebsiella spp.…”

Prevalence of mastitis in dairy cows from smallholder farms in Zimbabwe

“…from mastitic cows in this study supports findings from previous studies conducted in both commercial and smallholder dairy farms in Zimbabwe (Perry et al 1987;Makaya et al 1996;Kudinha & Simango 2002), South Africa (Swartz, Jooste & Novello 1984) and smallholder dairy farms in other regions of Africa (Getahun et al 2008;Lakew et al 2009). As observed in other studies in Zimbabwe and elsewhere (Makaya et al1996;Kudinha & Simango 2002;Petzer et al 2009), sub-clinical mastitis is most commonly associated with CNS. This highlights the importance of the role of CNS in sub-clinical mastitis and that some of them are more pathogenic than is generally assumed.…”

Sensitivity and specificity of a hand-held milk electrical conductivity meter compared to the California mastitis test for mastitis in dairy cattle

“…Non-informative prior probability distributions (beta 1,1) were employed for components of Se and Sp and a mildly informative prior was used for prevalence (beta 4.7, 10.4). The prior for prevalence was based on the quarter-level mastitis prevalence (31%; 212/683) using the number of cows with SCC >400,000/ml and isolation of bacterial pathogen as an approximate gold standard (Petzer et al, 2009). Receiver-operating characteristic (ROC) curves were plotted for evaluated cutoffs by connecting the points of the 1 -Sp (x-axis) by Se (y-axis).…”

“…Coagulase-negative staphylococci were the most frequently isolated bacteria in milk samples from both lactating and dry cows during 2000 to 2007, followed by Staphylococcus aureus and Streptococcus agalactiae (Petzer et al, 2009). Staphylococcus aureus can be considered the most important mastitis pathogen in South Africa because of the economic impact (Wilson et al, 1997) and potential for chronic infections and treatment failures.…”