Background: Subclinical mastitis (SCM) is one of the most economically important diseases affecting the dairy industry. The SCM does not cause visible changes in the udder or physical changes of the milk as compared to clinical mastitis, and a clear overview of the prevalence and risk factors in the different regions of Africa is still lacking. The objective of this study was to investigate the prevalence of SCM and assess the associated risk factors and dominant bacterial pathogens among cattle in Africa. Materials and methods: Using a systematic review and meta-analysis approach, we gathered literature concerning SCM among cattle in Africa, published from 2020 through 2021in five databases. Results: A total of 1,560 records were retrieved and at the end of the screening, 38 studies were eligible for inclusion in the meta-analysis. The random-effects meta-analysis model showed that the weighted pooled prevalence of SCM in cattle in Africa was 51.5% (95% CI: 44.0-58.9%). Heterogeneity was high and significant as I2 (proportion of observed variation) was 98.4% (95% CI: 97.6-99.0%), τ2 was 0.0533 (95% CI: 0.035-0.089), and the Cochran Q statistic was 2244.97 (p<0.0001). Sub-group and meta-regression analyses showed that West Africa had the highest point estimate (85.3%), followed by East Africa (64.1%), and the least was for southern Africa (16.3%) (p=0.007). Other significant moderators for SCM were age (p<0.0001), breed (p=0.015) and parity (p=0.0001) of cattle. Staphylococcus species were the most predominant pathogens, followed by Streptococcus and Escherichia spp. Conclusions: The present study showed a high variation of subclinical mastitis prevalence in various parts of Africa. There is a need for more data on subclinical mastitis in some regions on the continent. The information gathered in this paper may be used to guide a multidisciplinary approach to the management, control and reduction of this infection.
Mastitis is a cow disease usually signalized by irritation, swelling, and soreness of the udder. It is characterized by physical, chemical, and biological changes in the udder and milk. The aim of this study was to detect and characterize pathogens causing subclinical mastitis (SCM) from the milk of dairy cows of small-scale farmers through culture and molecular techniques. Milk was collected from 32 cows belonging to 8 small-scale farmers around Harrismith District, South Africa. The results showed that screening of SCM by California mastitis test and somatic cell counts (SCC) was 21.87 and 25%, respectively. Culture methods revealed the presence of Staphylococcus aureus at 93% followed by Streptococci spp. and Escherichia coli at 36.4 and 13.3%, respectively. The PCR could only detect E. coli, while single-molecule real-time sequencing showed a total of 2 phyla, 5 families, 7 genera, and 131 species. Clostridiaceae was the most abundant family, while Romboutsia was the most abundant genus followed by Turicibacter spp. The present study has documented the occurrence of SCM causing pathogens in milk collected from cows of small-scale farmers in Harrismith, indicating that SCM may be present at higher levels than expected.
Background: Mastitis is an important disease in dairy industry causing major economic burden. Subclinical mastitis (SCM) is regarded as one of the most economically important diseases affecting the dairy industry due to the financial constraints incurred by it. Subclinical mastitis as compared to clinical mastitis does not cause visible changes in the udder or physical changes of the milk hence the need for routine testing and surveillance. Materials and methods: The aim of this study was to assess the prevalence of subclinical mastitis in dairy cows of small-holder farms in the Free State province using California mastitis test (CMT) and somatic cell counts (SCC) and further characterise staphylococcal species isolated by using Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) and Polymerase chain reaction (PCR). Results: The CMT results revealed that out of 166 cows, only 55 (33%) were positive for intramammary infection. The quarter level prevalence based on SCC was 87 (54%) for intramammary infections. Out of 50 bacterial culture isolates, 48 (96%) were identified as S. aureus (76%), S. epidermidis (4%), S. chromogenes (12%) and S. haemolyticus (4%) by MALDI-TOF MS. The 16S rDNA PCR products and obtained sequences indicated that S. aureus was the dominant species infecting tested cows at 76%, followed by S. chromogenes, S. agnetis, S. argenteus and S. devriesei at 10%, 4%, 4%) and 1% respectively. Conclusions: This study has shown the presence of diverse Staphylococcusspecies infecting subclinical mastitis cows in sampled areas of the Free State province. It further indicated the importance of using various diagnostic tools for bacterial infection surveillance involved in subclinical mastitis to ensure accurate species identification.
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