




































East


East Afr. J. Biophys. Comput. Sci. (2024), Vol. 5, Issue. 1, 40-50 
 

 

 

 

 

 

Staphylococcus aureus in Bovine Mastitis: Prevalence and Risk Factors in Small holder Dairy Farms 

located in and around Hawassa, Ethiopia 

 

Nebyu Mje 1* , Birtukan Abebaw 2 

 
1College of Veterinary Medicine & Agriculture, Addis Ababa University, P.O.Box 34, Bishoftu, Ethiopia 
2Faculty of Veterinary Medicine, Hawassa University, P.O.Box 05, Hawassa, Ethiopia 

 

KEYWORDS:  

California Mastitis Test (CMT); 

Dairy cows;  

Hawassa town; 

Mastitis; 

Staphylococcus aureus  

 

 

 

 

 

 

 

 

 

 

 

ABSTRACT 

Mastitis is a widespread disease in dairy cattle that is known for its economic and public 

impact globally, including Ethiopia. Among others, Staphylococcus aureus is frequently 

isolated bacterial pathogen from milks of mastitis positive dairy cows. This cross-sectional 

study, conducted from March to August 202l in and around Hawassa, Ethiopia, aimed to 

estimate the prevalence of mastitis, to identify S. aureus in bovine mastitis milk and 

explore the associated risk factors. From 29 smallholder dairy farms, 250 lactating cows 

were purposively selected and screened using clinical signs and the California Mastitis 

Test (CMT) to diagnose clinical and subclinical mastitis, respectively. A standard 

bacteriological study was performed on 127 mastitis-positive milk samples, and the 

resulting data were analyzed using STATA (version 12), with significance set at p<0.05. 

The study findings indicated a mastitis prevalence of 50.8% at the cow level (4.8% 

clinical, 46% subclinical) and 27.4% at the quarter level (2.9% clinical, 24.5% 

subclinical). In the Lgistic regressin model, cw’s age, lactation stage, and farm 

cleaning frequency were significantly assciated (p < 0.05) with mastitis. Accordingly, 

Highest odds of mastitis were recorded in cows ≥ 6 years old (Odds ratio [OR] =17.61, 

95% confidence interval [CI] = 5.3, 58.44) and in farms less frequently cleaned (OR= 5.1, 

95%CI= 1.88, 13.71). Staphylococcus aureus was identified in 47.2% (60/l27) of milk 

samples, and more frequently in subclinical (47.8%) than clinical (41.6%) cases. In 

conclusion, our study confirmed a high prevalence of mastitis in the study area, 

particularly subclinical cases associated with S. aureus. The detection of S. aureus in 

nearly half of the mastitic milk samples suggests the potential involvement of other 

pathogens, warranting further research to identify additional causative agents. These 

findings highlight the need for routine screening of cows for timely treatment control 

intervention, and community awareness creation activities. 

  

INTRODUCTION 

Mastitis, characterized by inflammation of the 

udder and teats, is a prevalent condition in dairy 

cattle. It can manifest in two primary forms: 

clinical and subclinical mastitis (Ruegg et al., 

2017; Taponen et al., 2017). The disease is 

knwn for its damage to the udder tissue, which 

can happen in numerus mammalian species, 

East African Journal of Biophysical and Computational Sciences 

Journal homepage : https://journals.hu.edu.et/hu-journals/index.php/eajbcs 
 

Hawassa University

College of Natural & Computational Sciences

Year 2021

Volume xx No xx

 

 

*Corresponding author: 

  Email: nebhawas@gmail.com  +251910248878 https://dx.doi.org/10.4314/eajbcs.v5i1.4S 

 

 
Research article

https://dx.doi.org/10.4314/eajbcs.v5i1.4S


East Afr. J. Biophys. Comput. Sci. (2024), Vol. 5, No. 1, 40-50 
 

41 
 

mainly in domestic dairy animals. Being under 

constant state of physiological stress and most 

productive nature, mastitis is the most frequent 

disease of highly producing dairy cattle and can 

be potentially fatal (Gutierrez-Chavez et al., 

2019). Bovine mastitis has been reported as the 

most critical disease on most dairy farms 

associated with reduction of farm profitability 

due to decreased milk yield and quality, 

decreased reduced reproductive performance, 

discarded milk, high costs of treatment, death of 

the affected cow, and forced culling of young 

cows (Radostits et al., 2007; Julian, 2016).  

Subclinical mastitis (SCM) is an inflammation 

of the mammary gland characterized by the 

absence of visible lesions in the udder or its 

secretions, despite the presence of pathogenic 

microorganisms and an elevated somatic cell 

count (SCC) in the milk (Smith, 1996; Radostits 

et al., 2007). While both clinical and subclinical 

mastitis cause significant economic losses in the 

dairy industry, clinical mastitis remains a 

prevalent issue in many dairy herds (Gezehagn 

et al., 2020). Furthermore, mastitis poses a 

zoonotic risk due to the potential shedding of 

bacteria and toxins in milk.  

This complex disease is caused by diverse 

pathogens (mainly bacteria) that are commonly 

categorized epidemiologically as contagious or 

environmental. Contagious pathogens, primarily 

reside in the udder of infected cows and spread 

from cow to cow during milking, tend to cause 

chronic subclinical infections with intermittent 

clinical flare-ups at times of stress (Abebe et al., 

2016). Environmental bacteria, opportunistic 

organisms present in the cow's surroundings, 

typically cause shorter-term clinical infections 

(Blowey and Edmondson, 2010). 

Diagnosis of subclinical mastitis often relies on 

indirect tests, such as somatic cell count (SCC) 

and the California mastitis test (CMT), which 

measure the cellular response of the udder/cow 

to infection. Cows with healthy udder usually 

produce milk that contain SCC below 200,000 

cells/mL, however, if the SCC is over 400,000 

cells/mL the udder should be considered as 

having an intramammary infection (Idriss et al, 

2013). During mastitis (particularly during 

SCM), the presence of bacteria triggers an 

immune response, leading to increased 

migration of macrophages and neutrophils from 

blood into the milk, and a high SCC. This is also 

accompanied by inflammation of the gland, 

damage to host defense system, and epithelial 

cells (Douaa et al., 2016). The CMT, performed 

by mixing proportional amount of suspected 

milk with a reagent, detects increased leukocyte 

numbers by dissolving cell walls and releasing 

DNA, resulting in a stringy gel formation 

proportional to the degree of infection 

(Melleneger, 2001). 

Based on the existing literatures, over 140 

potentially pathogenic organisms (including 

bacteria, fungi, algae, Mycoplasma, and 

Nocardia) have been recorded as potential cause 

of cow mastitis. However, most bovine mastitis 

cases involves various bacterial pathogens, 

classified as contagious, teat skin opportunistic, 

or environmental (Radostits et al., 2007). 

Staphylococcus aureus is a frequent etiological 

agent incriminated for both subclinical and 

chronic infections, causing substantial economic 

losses in dairy farming (Kubota et al., 2007). 

Due to the increasing prevalence of mastitis, and 

calls to investigate its causes more thoroughly, 

this study aimed to determine the prevalence of 

both clinical and subclinical mastitis in small-

holder dairy farms in and around Hawassa town, 



East Afr. J. Biophys. Comput. Sci. (2024), Vol. 5, No. 1, 40-50 
 

42 
 

Southern Ethiopia, while isolating and 

identifying S. aureus from mastitic milk and 

identifying the associated risk factors. 

Considering the number of studies already done 

on the isolation of S. aureus in Ethiopia, this 

study aimed to update existing information and 

investigate if the epidemiology of the bacteria 

has changed. 

MATERIALS AND METHODS 

Study Area 

The study was carried ut in and around 

Hawassa City (Fig. 1). Hawassa, the capital city 

of the Sidama Region, is located at about 275 

km suth of Addis Ababa. The city has a total of 

157,879 inhabitants. Hawassa city, lies between 

7°03’l.35”N latitude and 38°29’43.81”E 

lngitude at an altitude of l750 meters above sea 

level. Annually, the area receives an average of 

800 - l000 mm of rainfall, and an average 

annual temperature of 22°C and 5l.8% mean 

relative humidity. Dry savanna and bush-type 

vegetation covers major part of the area. 

According to the central statistics authority 

(CSA, 2020), the region comprises about 

2,413,482 cattle, 308,903 goats, 467,858 sheep, 

34,709 horses, 16,376 donkeys, 1,824,841 

poultry, and 44,364 beehives. 

 

Figure 1. Study area map 

 

 



East Afr. J. Biophys. Comput. Sci. (2024), Vol. 5, No. 1, 40-50 
 

43 
 

Study Animals 

The study was carried out on lactating cross-

bred cows selected randomly from 29 small 

holder dairy farms and the associated risk 

factors were recorded on the sheet designed for 

it. Host related risk factors such as age, parity, 

lactation stage, body condition score (BCS), and 

average milk yield per day, were properly 

recorded on data recording sheet designed for 

this purpose. The age of the study animals 

(cows) were determined based on dentition as 

per the recommendation of Johnson (1998). 

Whereas, body condition score (BCS) of the 

cows were estimated using the standard guide 

developed by Sharad et al. (2016). For ease of 

data analysis and result presentation, the age 

classification was made into three as <3, 4 to 5 

and > 6 years. Moreover, the available records 

were used to collect data on the remaining host-

related risk factors, including parity, lactation 

stage, and average milk yield per day. Once the 

months of lactation is known, the cows were 

classified into three stages of lactation: early 

(first 3 months), mid (4 to 6 months), and late (7 

months or more). 

Study Design 

A prospective cross-sectional study design was 

used to investigate the problem from March 

2021 to August 2021. 

Sample Size Determination 

Thrusfield et al. (2017) formula was used to 

calculate the minimum sample size required for 

this study. Accordingly, an expected prevalence 

of 81.1% (Duguma et al., 2014), 95% 

confidence interval and a significance level of 

5% were used and computed to be 236. 

Although the minimum number of lactating 

dairy cows needed for the study was 236, we 

increased the sample size to 250. 

Study Methodology 

Dairy cows were purposively selected from 29 

smallholder farms located within and adjacent to 

the Hawassa city administration to assess the 

prevalence and risk factors of mastitis. Each 

selected lactating cow underwent screening for 

mastitis using clinical examination and the 

California Mastitis Test (CMT). Cows 

exhibiting either clinical signs of mastitis or a 

positive CMT result were considered to have 

mastitis, and hence milk samples from these 

cows were collected for bacteriological culture. 

The primary aim of the culture was to identify 

the presence of Staphylococcus aureus. 

Moreover, farm visit (observation) and 

interviews with farm owners were conducted to 

gather relevant information on the putative risk 

factors for both clinical and subclinical mastitis, 

including host related risk factors (i.e. age, body 

condition score, parity, lactation stage, and daily 

milk yield), husbandry system, hygienic status 

of the farms, and past occurrences of mastitis 

within the herd.  

Clinical Inspection of the Udder 

To diagnose clinical mastitis, the udders of all 

study cows were subjected to both visual 

inspection and palpation. Special attention was 

given for indicators of acute or chronic 

inflammatory reactions, including: hardened 

(chronic) and swollen udder quarters, pain 

responses to udder palpation (manifested by 

kicking), localized heat and redness, and 

alterations in milk secretions such as the 



East Afr. J. Biophys. Comput. Sci. (2024), Vol. 5, No. 1, 40-50 
 

44 
 

presence of clots or flakes, a watery 

consistency, or blood tinge. 

California Mastitis Test  

California Mastitis Test (CMT) was used to 

detect subclinical mastitis. From each quarter of 

a suspected cow, a squirt of milk was dispensed 

into separate wells of the CMT paddle, followed 

by an equal amount of CMT reagent. The 

mixture was gently agitated, and the resultant 

gel formation, if there is any, was visually 

scored based on its thickness. Accordingly, 

scores were assigned as follows: 0 (negative), T 

(trace), 1 (weak positive), 2 (distinct positive), 

and 3 (strong positive), reflecting the level of 

infection. Quarters with a score of 1 or greater 

were classified as positive for subclinical 

mastitis, while those with a score of 0 were 

classified as negative (Quinn et al., 2002) 

Milk Sample Collection 

The teats of mastitis positive cows were 

properly washed and disinfected with 70% 

alcohol, and then approximately 10 mL of milk 

was collected aseptically into sterile bottle from 

each affected quarter after discarding few squirt 

(the initial three streams) of milk. The bottles 

were properly labeled, immediately placed in a 

chilled icebox containing ice packs and then 

transport to the Veterinary Microbiology 

Laboratory at Hawassa University. Upon 

arrival, samples were stored at +4°C and held 

for no more than 24 hours prior to bacterial 

culture. 

Isolation and Identification 

Bacteriological culture was made following the 

standard microbiological techniques (Quinn et 

al., 2002). Briefly, a loop-full of each milk 

sample was streaked onto sterile blood agar base 

(Himedia, India) enriched with 5% sheep blood. 

Plates were incubated aerobically at 37°C and 

examined after 24–48 hours for colony growth. 

Colonies were initially characterized based on 

morphology, hemolytic pattern, and Gram 

staining reaction. Gram-positive colonies 

exhibiting a typical grape-like arrangement 

under microscopy were selected for further 

analysis. 

The selected colonies were subcultured onto 

nutrient agar plates (Oxoid, UK) and incubated 

at 37°C for 24 hours. Subsequently, a catalase 

test was performed using 3% hydrogen peroxide 

(H2O2). Catalase-positive, Gram-positive cocci 

were then subcultured onto Mannitol Salt Agar 

(MSA) and incubated at 37°C. After 24–48 

hours, MSA plates were examined for growth 

and color change. The presence of growth 

accompanied by a color shift from red to yellow 

on the MSA (i.e. a change in the medium's pH) 

was considered presumptive evidence of salt-

tolerant Staphylococcus species (Quinn et al., 

2002). 

A tube coagulase test, following the method of 

Robertson et al. (1999), was performed. Fresh 

cultures of suspected staphylococci, grown in 

nutrient broth for 18-24 hours, were mixed with 

0.5ml of 10 fold diluted sterile rabbit plasma 

(Sigma). This mixture was incubated at 37°C 

and examined every 4-24 hours for clot 

formation. Any degree of visible clotting was 

considered a positive result (Tallent et al., 

2001). Additionally, suspected S. aureus 

cultures were inoculated onto purple agar base 

(PAB) media supplemented with 1% maltose 

and incubated at 37°C for 24 hours. S. aureus 

isolates were expected to rapidly ferment 



East Afr. J. Biophys. Comput. Sci. (2024), Vol. 5, No. 1, 40-50 
 

45 
 

maltose, leading to the production of acidic 

metabolites that turn the medium and colonies 

yellow. 

Ultimately, the isolates were considered positive 

for S. aureus if they exhibited catalase-positive 

and coagulase-positive results, combined with 

growth on MSA and PAB media with an 

associated yellow coloration of the media 

(Quinn et al., 2002).. 

Data Analysis 

Following data collection, records were entered 

into Microsoft Excel, coded appropriately, and 

then subjected to statistical analysis. Mastitis 

prevalence was calculated as the proportion of 

cows diagnosed with mastitis (encompassing 

both clinical and subclinical forms) relative to 

the total number of examined lactating cows. To 

explore the association between putative risk 

factors and mastitis prevalence, odds ratios 

(OR) were computed. On top of that, a logistic 

regression model was utilized with STATA  

Corp. (version 12.0) software to assess the 

independent contribution of each risk factor to 

the likelihood of mastitis. Statistical significance 

for all analyses was set at a 95% confidence 

level, with a p-value < 0.05. 

RESULTS 

Prevalence of Mastitis 

This cross-sectional study investigated mastitis 

in 250 lactating cows. The results showed that 

50.8% (l27/250) of the cows had some form of 

mastitis (either clinical or subclinical). Among 

these, 4.8% (l2/250) exhibited clinical mastitis, 

while a larger proportion, 46% (ll5/250), had 

subclinical mastitis. When considering 

individual udder quarters, the overall mastitis 

prevalence was 27.4% (274/l000). Clinical 

mastitis was identified in 2.9% (29/l000) of 

quarters, while subclinical mastitis affected 

24.5% (245/l000) (Table l). 

 

 

 

Bacterial Isolation 

Bacteriological analysis was performed on the 

l27 milk samples obtained from cows diagnosed 

with mastitis to determine the presence of S. 

aureus. Accordingly, S. aureus was isolated 

from 4l.6% (5/l2) of samples from cows with 

clinical mastitis and from 47.8% (55/ll5) of 

samples from cows with subclinical mastitis. 

The overall prevalence of S. aureus among all 

mastitis-positive samples was 47.2% (60/l27), 

as shown in Table 2. 

. 

 

 



East Afr. J. Biophys. Comput. Sci. (2024), Vol. 5, No. 1, 40-50 
 

46 
 

 

Table 2. Prevalence of S. aureus in clinical and subclinical mastitis 

 
 

Risk Factors Associated with Mastitis 

Multivariate lgistic regression analysis 

revealed that age of the cows, late lactation 

stage, and farm hygiene frequency were 

significantly assciated with mastitis. In 

contrast, milk yield, parity, and husbandry 

system were not identified as significant risk 

factors in this model (Table 3). 

 

Table 3. Logistic regression analysis of potential risk factors for the occurrence of mastitis in the 

study area 

OR: odds ratio, lit.: liter, No.: number 

DISCUSSION 

The present study found an overall mastitis 

prevalence of 50.8% at the cow level and 27.4% 

at the quarter level. These prevalence are 

consistent with those reported in earlier studies 

by Hundera et al. (2005) and Abera et al. 

(2010). In most developing cuntries, mastitis 

prevalence tends to be approximately 50% in 

 

Risk 

factors 

 

Categories 

No. of cows  

Crude  

OR (95% CI) 

 

Adjusted  

OR (95% CI) 

 

p-

value 

 

Examined 

Psitive 

(proportion) 

Age (years) <3  

4-5  

>6  

93 

98 

59 

21 (22.6) 

47 (47.9) 

47 (79.7) 

1 

3.16(1.68, 5.92) 

13.43(6.04, 29.85) 

1 

3.7 (1.63, 8.43) 

17.61 (5.3, 58.44) 

 

0.002 

0.000 

Parity  <2  

>3  

134 

116 

43 (32.1) 

72 (62.1) 

1 

3.46 (2.06, 5.83) 

1 

1.29 (0.59, 2.79) 

 

0.512 

Lactation 

stage 

(Months) 

Early 

Mid 

Late 

85 

89 

76 

27 (31.7) 

43 (48.3) 

45 (59.2) 

1 

2.01 (1.08, 3.72) 

3.11 (1.63, 5.95) 

1 

1.81 (0.9, 3.62) 

2.1 (1.0, 4.32) 

 

0.094 

0.049 

Milk yield 

per day 

(lit.) 

<10  

11-15  

>16  

86 

82 

82 

45 (52.3) 

34 (41.5) 

36 (43.9) 

1 

1.56 (0.84, 2.80) 

1.41 (0.76, 2.58) 

1 

1.26 (0.61, 2.63) 

1.39 (0.66, 2.94) 

 

0.531 

0.384 

Husbandry 

system 

Intensive 

Semi-intensive 

233 

27 

102 (43.7) 

13 (48.1) 

1 

1.10 (0.49, 2.45) 

1 

1.97 (0.68, 5.88) 

 

0.213 

Frequency 

of farm 

cleaning 

per day 

> 4 times 

3  

2  

 36 

130 

84 

10 (27.7)  

53 (40.7) 

52 (61.9) 

1 

2.36 (1.37, 4.15) 

4.24 (1.80, 9.90) 

1 

2.94 (1.58, 5.81) 

5.1 (1.85, 13.7) 

 

0.002 

0.002 



East Afr. J. Biophys. Comput. Sci. (2024), Vol. 5, No. 1, 40-50 
 

47 
 

cows and 25% in quarters. Nevertheless, our 

findings are notably lower than those observed 

in several other Ethiopian studies (Abebe et al., 

2016; Zeryehun & Abera, 2017; Elem et al., 

2017; Tegegne et al., 2020), which documented 

cow-level prevalence ranging from 62.6% to 

70%. Conversely, the prevalence in this study 

was higher than earlier reports by Workineh et 

al. (2002), Mungube et al. (2004), and Kerro 

and Tareke (2003), which ranged from 38.2% to 

40%. The prevalence difference across studies 

suggests that differences in husbandry practices 

and environmental factors play a critical role in 

mastitis incidence (Radostits et al., 2007).  

The higher prevalence of sub-clinical mastitis 

(46%) than clinical mastitis (4.8%) encountered 

in the current study supports previus studies 

conducted in various parts of the country, which 

have consistently determined that sub-clinical 

mastitis is prevailing than clinical mastitis. In 

line with this, subclinical and clinical mastitis 

prevalence were 62.9% and 37.0% (Kerro & 

Tareke, 2003), 59.2% and 3.4% (Abebe et al., 

2016), 48.6% and 22.4% (Mekbib et al., 2010), 

36.7% and 10.0% (Abera et al., 2010), and 

27.86% and 11.45% (Tassew et al., 2017) 

respectively. The consistently higher prevalence 

of subclinical mastitis in these studies, including 

ours, is likely due to its insidious nature and 

lack of overt symptoms which often delays 

detection and treatment (Radostits et al., 2007). 

Our study also found that mastitis prevalence 

was significantly higher during late lactation 

(59.2%), which is consistent with Almaw et al. 

(2008), Getahun et al. (2008), and Abera et al. 

(2012). However, this contrasts with Kerro and 

Tareke (2003), who reported higher rates during 

early lactation. Such discrepancies may stem 

from differences in cow age and parity (Isae & 

Kurtu, 2018).  

The present study also showed that older cows 

(>6 years) had a higher prevalence of mastitis 

(79.7%) than younger cows (<3 years) (22.6%), 

supporting the findings of Kerro and Tareke 

(2003) and Busato et al. (2000). This increased 

risk in older cows has been attributed to 

anatomical changes, such as larger teats and 

weaker sphincter muscles, facilitating pathogen 

entry (Radostits et al., 2007).The findings of the 

current study regarding the increased prevalence 

of mastitis with parity are consistent with 

previous reports by Zeryehun et al. (2013), 

Abunna et al. (2013), Belayneh et al. (2014), 

and Dabele et al. (2021). The likelihood of 

mastitis was 3 to 13 times higher in multiparous 

cows compared with primiparous cows. In line 

with this a study conducted by Abebe et al. 

(2016) also reported odds of 24.8 for cows with 

four or more calvings.  This association may be 

attributed to the fact that primiparous cows 

possess a more effective defense mechanism 

against mastitis compared to multiparous cows 

(Erskine, 2001). The likelihood of infection 

increases over time in multiparous cows, 

leading to a prolonged duration of infection 

(Radostits et al., 2007). 

A key finding of this study was that mastitis 

prevalence was significantly higher (61.9%) in 

cows housed in facilities cleaned twice daily, 

compared to those cleaned four or more times 

daily. This suggests that the frequency of cow 

house cleaning is an important factor in mastitis 

control, particularly of the environmental ones. 

Notably, the study did not find a significant link 

between husbandry system (such as grazing, 

confinement) or a prior history of mastitis and 

current mastitis prevalence. These results should 



East Afr. J. Biophys. Comput. Sci. (2024), Vol. 5, No. 1, 40-50 
 

48 
 

be interpreted with consideration for the context 

of this particular study.  

The microbiological investigations identified S. 

aureus in 47.2% of mastitic cows, which 

corresponds with similar studies in Holeta 

(Mekibib et al., 2010) and Addis Ababa 

(Legesse et al., 2015). However, some other 

studies have reported both lower (Workineh et 

al., 2002; Tesfaye et al., 2013; Yohannis and 

Molla, 2013; Zeryehun et al., 2013) and higher 

(Abebe et al., 2016; Zenebe et al., 2014) 

prevalence of S. aureus. Such variations among 

studies are likely due to husbandry practices and 

environmental differences.  

Staphylococcus aureus, a mastitis causing 

contagious pathogen, is known for its ability to 

establish chronic, subclinical infections, as well 

as acute and clinical mastitis. Consistent with 

Tassew et al. (2017), our study found that S. 

aureus was more common in subclinical 

mastitis cases than clinical cases. This indicates 

that S. aureus is a key causative agent in these 

less visible infections, as they have a tendency 

to establish chronic long term infections and act 

as a source of transmission (Radostits et al., 

2007). The propensity of the bacteria to induce 

subclinical mastitis could be related to the 

numerous virulence factors including its 

capacity to produce biofilm, toxins, or various 

enzymes capable of damaging the udder tissue 

and concomitantly establish itself in the infected 

area (Artursson et al., 2016).  

CONCLUSION & RECOMMENDATIONS 

Mastitis remains a significant infectious disease 

in dairy cows, affecting the dairy industry 

significantly. In this study, subclinical mastitis 

was the most prevalent form, likely due to a 

greater focus on clinically visible forms by farm 

owners and animal health workers, which 

allows subclinical cases to go unnoticed. 

Mastitis prevalence varied significantly with 

cow age, lactation stage, and farm hygiene 

practices. These findings highlight the need for 

routine screening and early intervention to 

detect and treat subclinical mastitis. 

Furthermore, raising awareness about the public 

health risks and economic impacts associated 

with S. aureus is critical. 

Acknowledgements 

The dairy farmers who gave permission to 

perform this study on their dairy farms are duely 

acknowledged. We also extend our appreciation 

to Tesfaye Tlesa and Dr. Mesele Abera for 

technical support in the lab and provision of the 

CMT reagent, respectively. 

References 

Abebe R., Hatiy H., Abera M., Megersa B. and Asmare 

K. 2016. Bovine mastitis: Prevalence, risk factors 

and isolation of Staphylococcus aureus in dairy 

herds at Hawassa milk shed, south Ethiopia. BMC 

Vet. Res. 12(270): 2-11. 

Abera M., DemieB., Aragaw K., Regassa F. and Regassa 

A. 2010. Isolation and identification of 

Staphylococcus aureus from bovine mastitic milk 

and their drug resistance patterns in Adama town, 

Ethiopia. J. Vet.Med. Anim. Health. 22(3): 29-34. 

Abera M., Habte T., Aragaw K., Asmare K. and Sheferaw 

D. 2012.Major causes of mastitis and associated risk 

factors in smallholder dairy farms in and around 

Hawassa, Southern Ethiopia. Trop. Anim. Health 

and Prod. 44: 1175-1179. 

Abunna F., Fufa G., Megersa B. and Regassa A. 2013. 

Bovine Mastitis: Prevalence, Risk Factors and 

Bacterial Isolation in Small-Holder Dairy Farms in 

Addis Ababa City, Ethiopia. Glob.Veterinaria. 

10(6): 647-652. 

Almaw G., Zerihun A. and Asfaw Y. 2008. Bovine 

mastitis and its association with selected risk factors 

in smallholder dairy farms in and around Bahir Dar, 

Ethiopia. Trop. Anim. Health and Prod. 40:427-432. 



East Afr. J. Biophys. Comput. Sci. (2024), Vol. 5, No. 1, 40-50 
 

49 
 

Artursson K., Söderlund R., Liu L., Monecke S. and 

Schelin J. 2016. Genotyping of Staphylococcus 

aureus in bovine mastitis and correlation to 

phenotypic characteristics. Vet. Microbiol. 193:156–

161. 

Belayneh R., Belihu K. and Tesfaye A. 2014. 

Microbiological study on bacterial causes of bovine 

mastitis and its antibiotics susceptibility patterns in 

East Showa Zone, Akaki District, Ethiopia. J. Vet. 

Med. Anim. Health. 6(4): 116-122. 

Blowey R. and Edmondson P. 2010. Mastitis control in 

dairy herds (2nded.). CAB International, UK. 

Busato A., Trachsel P., Schallibaum M. and Blum J. 

2000. Udder health and risk factors for subclinical 

mastitis in organic dairy farms in Switzerland. Prev. 

Vet. Med. 44(3-4): 205-220. 

Central Statistical Authority (CSA). 2020. Federal 

democratic republic of Ethiopia central statistical 

agency Agricultural sample survey. Report on 

Livestock and livestock Characteristics. 

Dabele D.T., Borena B.M., Admasu P., Gebremedhin 

E.Z. and Marami L.M. 2021. Prevalence and risk 

factors of mastitis and isolation, identification and 

antibiogram of staphylococcus species from mastitis 

positive zebu cows in Toke Kutaye, Cheliya, and 

Dendi districts, West Shewa Zone, Oromia, 

Ethiopia. Inf. and Drug Resis.14: 987-998. 

Douaa A., Rasha M. and BassamY. 2016. Isolation and 

identification of staphylococcus aureus from 

buffalo’s milk infected with subclinical mastitis and 

milk workers. Basrah J. Vet. Research.15 (2): 304-

312. 

DugumaA., Tolosa T. and Yohannes A. 2014.Prevalence 

of clinical and sub-clinical mastitis on cross bred 

dairy cows at Holleta Agricultural Research Center, 

Central Ethiopia. J. Vet. Med. Anim. Health .6(1): 

13-17. 

Elemo K.K., Sisay T., Shiferaw A. and Fato M.A. 2017. 

Prevalence, risk factors and multidrug resistance 

profile of Staphylococcus aureus isolated from 

bovine mastitis in selected dairy farms in and around 

Asella town, Arsi Zone, South Eastern Ethiopia. 

African Jour. of Microb.Research.11:1632-1642. 

Erskine R. 2001. Intramuscular administration of ceftiofur 

sodium versus intramammary infusion of 

penicillin/novobiocin for treatment of Streptococcus 

agalactiae mastitis in dairy cows. J. American Vet. 

Medical Assoc.208: 258-260. 

Geleta B., Beyene D., Wubete A. and Abunna F. 2019. 

Sub Clinical Mastitis in Dairy Farms of Addis 

Ababa and Sebeta Towns, Ethiopia. Biol. l and. 

Med. Jour. of Science and Tech. Research, 12(5): 

9566-9571. 

Getahun K., Kelay B., Bekana M. and Lobago F. 2008. 

Bovine mastitis and antibiotic resistance patterns in 

Sealle smallholder dairy farms, central Ethiopia. 

Trop. Anim. Health Prod. 40: 261-268. 

Gezehagn K., Betelhem T.and Belege T. 2020.Isolation 

and identification of major pathogenic bacteria from 

clinical mastitic cows in Asella town, Ethiopia. Vet. 

Med. Inter. 2020. 

Gutierrez Chavez A.J., Guzman-Rodriguez J.J., Leon-

Galvan F.M., Barboza-Corona J.E., Valencia 

Posadas M., Ochoa-Zarzosa A., et al. 2019. 

Staphylococcus agnetis: An emergent pathogen 

isolated from subclinical mastitis with capacity to 

internalize into bovine mammary epithelial cells. 

Jour. of Adv. Dairy Research.7: 221. 

Hundera S., Ademe Z. and Sintayehu, A. 2005.Dairy 

cattle mastitis in and around Sebeta, Ethiopia. Inter. 

Jour. of Appl. Vet. Med. 3 (4): 1525-1530. 

Idriss S.E., Foltys V., Tančin V., Kirchnerová K. and 

Zaujec K. 2013. Mastitis pathogens in milk of dairy 

cows in Slovakia. Slovak J. Anim. Sci. 46: 115–119.  

Isae A.A. and Kurtu Y.M. (2018).Mastitis and its effect 

on chemical composition of milk in and around 

Worabe Town, Siltie Zone, Ethiopia. Amer. Scien. 

Res. Jour. for Eng., Tech. and Sc. 42(1): 210-220. 

Johnson R.F. 1998. The Stockman’s Handbook by 

Ensminger, 2nd ed., Pp. 539. 

Julian R. 2016. Streptococcus agalactiae subclinical 

mastitis epidemiology and control in Colombian 

dairy herds. Vet. Med. Inter. 13 (5): 690-695. 

https://islandscholar.ca/islandora/object/ir%3A2024

2/datastream/PDF/view 

Kerro D. and Tareke F. 2003.Bovine mastitis in selected 

areas of Southern Ethiopia. Trop. Anim. Health and 

Prod.35: 197-205. 

Kubota M., Hayashi T., Iwasaki K., Ohtsuka H., 

Kohiruimaki M., Kawamura S. and Abe R. 

2007.Rapid and effective method for separation of 

Staphylococcus aureus from somatic cells in mastitis 

milk. Jour. of Dairy Sc. 90(9): 4100-4107. 

Legesse G., Beemnet M. and Reta T. 

2015.Staphylococcus aureus in mastitic crossbreed 

cows and its associated risk factors in Addis Ababa 

City, Ethiopia. Ethiop. Vet. Jour. 19 (1): 107-116. 

Mekibib B., Furgasa M., Abunna F., Megersa B. and 

Regassa A. 2010. Bovine mastitis: prevalence, risk 

factors and major pathogens in dairy farms of Holeta 

town, central Ethiopia.Vet.World.3 (9): 397-403. 

Mellenger R. 2001. California mastitis test (CMT): An 

invaluable tool for managing mastitis. Department 

of Animal Science, Michigan State University, 

USA, Pp. 9. 

Mungube E.O., Tenhagen B.A., Kassa T., Regassa F., 

Kyule M.N. and Greiner M. 2004.Risk factors for 

dairy cow mastitis in the central highlands of 

Ethiopia. Trop. Anim. Health and Prod. 36: 463-

472. 

https://islandscholar.ca/islandora/object/ir%3A20242/datastream/PDF/view
https://islandscholar.ca/islandora/object/ir%3A20242/datastream/PDF/view


East Afr. J. Biophys. Comput. Sci. (2024), Vol. 5, No. 1, 40-50 
 

50 
 

Quinn P.J., Carter M.E., Markey B. and Carter G.R. 

2002.Clinical Veterinary Microbiology. Spain: 

Mosby International Limited, Pp. 96-344. 

Radostits O.M., Gay C.C., Hinchcliff K.W. and Constable 

P.D. 2007. Mastitis in Veterinary Medicine: 

Textbook of the Diseases of Cattle, Horse, Sheep, 

Pigs, and Goats (10thed.). London: Elsevier. 

Rafik H.S., Selim S.S. andRafik T.S. 2014.Bacteriological 

evaluation of present situation of mastitis in dairy 

cows.Glob Veterinaria.13 (5): 690-695. 

Roberson J.R., Fox L.K., Hancock D.D. and Besser T.E. 

1999. Evaluation of methods for the differentiation 

of coagulase-positive staphylococci. Jour. of Clin. 

Micr. 30 (12): 3217-3219. 

Ruegg P. L. 2017. A 100-year review: mastitis detection, 

management, and prevention. J. Dairy Sc. 100 

(12):10381–10397. 

Sharad M., Kiran K. and Ashutosh D. 2016. Body 

condition scoring of dairy cattle: A review. J. Vet. 

Sc. 2 (1): 1-8. 

Smith B.P. 1996. Large animal internal medicine (2nded.). 

Mosby. 

Tallent S., Hait J., Bennett R.W. and Lancette G.A. 2001. 

Bacteriological Analytical Manual. 

Taponen S. Liski E. Heikkila A.M. and Pyorala S. 2017. 

Factors associated with intramammary infection in 

dairy cows caused by coagulase-negative 

staphylococci, Staphylococcus aureus, 

Streptococcus uberis, Streptococcus dysgalactiae, 

Corynebacterium bovis, or Escherichia coli” J. 

Dairy Sc. 100 (1): 493–503. 

Tassew A., Aki A. and Legesse K. 2017. Isolation, 

identification and antimicrobial resistance profile of 

Staphylococcus aureus and occurrence of methicillin 

resistant S. aureus isolated from mastitic lactating 

cows in and around Assosa town, Benishangul 

Gumuz region, Ethiopia. Jour. of Dairy, Vet.& 

Anim. Research.6 (3): 308-314. 

Tegegne D.T., Yalew S.T., Emeru B.A. and Equar Y. 

2020. Study of prevalence, associated risk factors 

and causative bacteria of bovine mastitis in Ethiopia. 

Inter. Jour. of Vet. Sc. and Tech. 4 (1): 001-006. 

Tesfaye A., Yohannes A., Hude A., Tezera T.and 

G/Tsadik Z. 2013.Mastitis: Prevalence, risk factors 

and antimicrobial sensitivity patterns of bacterial 

isolates in dairy cattle at Holeta farm in 

Ethiopia.Afric.Jour.l of Agr.Research.8(23): 2837-

2842. 

Thrusfield M., Christley R., Brown H., Diggle P. J., 

French N., Howe K., Kelly L., O'Connor A., 

Sargeant J.andWood,H. (2017). Veterinary 

Epidemiology: Fourth Edition. (4thed.) Wiley-

Blackwell. https://doi.org/10.1002/9781118280249.  

Workineh S., Bayleyegn M., Mekonnen H. and Potgieter 

L.N. 2002. Prevalence and etiology of mastitis in 

cows from two major Ethiopian dairies. Trop. Anim. 

Health and Prod.34: 19-25. 

Yohannis M. and Molla W. 2013.Prevalence, risk factors 

and major bacterial cause of bovine mastitis in and 

around Wolaita Sodo, Southern Ethiopia. Glob. 

Jour. of Micr.Research.1(1): 106-111. 

Zenebe N., Habtamu T. and Endale B. 2014. Study on 

bovine mastitis and associated risk factors in 

Adigrat, Northern Ethiopia. Afric. Jour. of 

Micr.Research.8: 327-331. 

Zeryehun T. and Abera G. 2017. Prevalence and bacterial 

isolates of mastitis in dairy farms in selected districts 

of Eastern Harrarghe zone, Eastern Ethiopia. Jour. 

of Vet.Med. 2017. https://doi.org/10.1155/2017 

/6498618.  

Zeryehun T., Aya T. and Bayecha R. 2013. Study on 

prevalence, bacterial pathogens and associated risk 

factors of bovine mastitis in smallholder dairy farms 

in and around Addis Ababa, Ethiopia. Jour. of Anim. 

and Plant Sc. 23: 50-55. 

  

 
 

https://doi.org/10.1002/9781118280249
https://doi.org/10.1155/2017%20/6498618
https://doi.org/10.1155/2017%20/6498618

