Prevalence and Risk Factors of Bovine Mastitis on Conventional Dairy Farms in Northwestern Algeria

F. Seddar-Yagoub1,*, A.A. Dahou1, Z. Meskini1, K. Doukani1, A. Homrani1
1Laboratory of Sciences and Technics of Animal Production, Abdelhamid Ibn Badis University, Mostaganem, Algeria.

Background: Algeria’s dairy sector is experiencing various obstacles, such as a high frequency of diseases in dairy farms, particularly mastitis. Nonetheless, there has been a scarcity of research on mastitis occurrence, notably in Algeria’s Western area. As a result, the purpose of this study was to investigate the prevalence of mastitis and its associated risk factors in Algeria’s northwest area.

Methods: The study included 130 dairy cows from 17 farms. The California mastitis test (CMT) and visual inspection were used to determine the prevalence of subclinical and clinical mastitis. 

Result: The total cow-level prevalence was 68.50% (89/130), with clinical cases accounting for 3.10% (4/130) and subclinical cases accounting for 65.40% (85/130). The quarter-level prevalence of mastitis was 35.19% (183/520), with 3.08% (16/520) clinical cases and 32.11% (167/520) subclinical cases. The study found that parity, lactation stage and age were all significant intrinsic risk factors for mastitis (P<0.05). Additionally, cow cleanliness level, cleaning solution, wiping udder after washing and dry cow treatment were significant extrinsic risk factors linked with mastitis (P<0.05). Given the high prevalence of mastitis in this region, regular screening and treatment are crucial to minimize the risk of mastitis and enhance cow health.

Despite worldwide efforts and numerous management programs, mastitis remains a serious problem for the dairy sector in terms of economic effect. It is anticipated to cost roughly 72 billion dollars every year (Bradley, 2002; Kumar et al., 2014). Cow mastitis is a complicated and multifaceted illness caused mostly by a variety of pathogens categorized as infectious and environmental (Radostits, 2007; Kumar et al., 2014). The disease is caused by the interplay of animals, pathogens, the environment and management variables.
       
Mastitis can appear clinically or subclinically. Atypical milk production, udder oedema and systemic symptoms such as fever, lethargy and anorexia define clinical cases (Eraskine, 2001). Subclinical mastitis, on the other hand, is difficult to detect since there are no visible changes in milk or udder appearance, but it can have a substantial impact on dairy producers by lowering milk production, changing milk quality and limiting reproductive activity (Ghallache et al., 2021).
       
Subclinical mastitis infections are especially problematic in dairy farming since 90-95% of animals do not exhibit clinical signs, although milking output might be decreased by 5-20%, according to Juozaitiene et al., (2006). Algeria consumes 5 billion liters of milk per year, whereas domestic output is roughly 3.5 billion liters. To compensate for the gap, the country imports 1.5 to 2 billion liters of milk powder, which cost US$1.50 billion in 2021 (Demmad, 2021). Mastitis was the first prevalent disease identified in dairy farms in Algeria’s northwest area (Meskini et al., 2021a).
       
Mastitis is a serious impediment to the growth of the dairy sector in Algeria, particularly in the west, where information on the frequency of bovine mastitis is limited. As a result, the goal of this study is to give insight into the existing status of mastitis, both clinical and subclinical, at dairy farms in Algeria’s northwestern region. We are seeking a better knowledge of the disease’s occurrence in the region by performing this study and identifying the main risk factors that contribute to mastitis development and recurrence. This data may then be used to develop more effective mastitis prevention and control techniques, ultimately enhancing the health and productivity of the region’s dairy cattle.
Study area and sample size
 
Cross-sectional research was undertaken in the provinces of Sidi bel abbes, Oran, Mascara and Mostaganem in Algeria’s northwestern area, which are key producers to milk production in western Algeria. The research comprised 17 dairy farms ranging in herd size from 5 to 15 cows. The study included 130 lactating cows of various breeds, principally Holstein, Red Holstein and Montbeliarde, who were handled in both semi-intensive and traditional farming systems. The research was carried out from January 2021 to May 2022 with the goal of evaluating the prevalence of bovine mastitis and identifying risk factors. The farms were chosen based on the owners’ willingness to participate in the study and all lactating dairy cows present on the farms were included in the analysis without exception.
 
Study methodology
 
Field survey
 
A pre-designed questionnaire was used in the study to collect information about the dairy farms and animals involved. The questionnaire was split into two sections. The first section intended to gather general information regarding farm management techniques and risk factors. The second section was more thorough, focusing on the farmers’ cleanliness and prophylactic methods. This section’s data included information regarding milking hygiene methods and preventative measures, including dry cow treatment. The questionnaire was carefully designed to offer a thorough knowledge of the elements that may contribute to the prevalence of bovine mastitis in the research region.
 
Clinical inspection
 
The udder was inspected and physically examined for symptoms of mastitis such as changes in size, consistency, lesions, fibrosis, pain, heat, redness and swelling. Moreover, milk quality was visually assessed using a black-bottomed bowl to detect any anomalies such as clots, flakes, or blood. A clinical case of mastitis was judged positive if one or more of these indications were present in any quarter or the entire udder. This method offered a thorough assessment of the occurrence and severity of mastitis.
 
California mastitis test (CMT)
 
The first step in screening for subclinical mastitis was a thorough washing of the udders with a biocide solution and water, followed by individual wiping as recommended by Quinn et al., (1999). A total of 504 teats were tested by taking 2 mL of milk from each quarter (Fig 1a) and combining it with an equivalent quantity of commercial CMT reagent (RAIDEX GmbH, Germany) as shown in Fig 1b. The viscosity of the resultant mixture was graded on a scale of 0 to 4, with scores of 0 and 1 categorized as negative and trace, respectively and scores of 2, 3 and 4 classifieds as positive. A cow was judged to have subclinical mastitis if at least one quarter tested positive with a score of 2 or above.
 

Fig 1: CMT test.


 
Data analysis
 
The number of cows or quarters that tested positive for mastitis was divided by the total number of cows or quarters examined to establish the overall prevalence of mastitis.
       
The study’s information was recorded in a Microsoft Excel spreadsheet and analyzed with the statistical program SPSS version 21. To examine the link between mastitis infection and other risk factors, the Chi-square (2) test was performed. A p-value less than 0.05 (p<0.05) was judged statistically significant, showing a significant relationship between mastitis infection and the particular risk factor under consideration.
The goal of our study was to investigate the frequency of bovine mastitis in dairy cows and identify potential risk factors.
 
Mastitis prevalence
 
Cow level
 
According to the results shown in Table 1, we discovered a significant incidence of mastitis at the cow level, with a rate of 68.5%, using both clinical inspections of the udder and the California Mastitis test (CMT). The prevalence rate contrasts from that reported by Hocine et al., (2021) in Algeria and Belay et al., (2022) in Ethiopia, where the prevalence rates were 41.66% and 17.1%, respectively. Our findings, however, are consistent with prior research in Ethiopia, such as studies by Abebe et al., (2016) and Melesse and Minyahil (2019), which found prevalence rates of 64.3% and 73%, respectively, as well as Maalaoui et al., (2021) in Tunisia, who reported a prevalence rate of 60.3%. These discrepancies may be attributable to regional, environmental and agroecological variables, changes in farm management, husbandry methods, production systems and the investigators’ research methodology or equipment. Mastitis is also a complicated illness involving the combination of animal risk factors and causative agents, and its incidence varies (Radostits et al., 2007).
 

Table 1: Prevalence of clinical and subclinical mastitis at a cow and quarter levels.


       
In our study, 65.4% of dairy cows had subclinical mastitis. This number is comparable to other studies done in Algeria (Fartas et al., 2017; Meskini et al., 2021b; Ghallache et al., 2021), which showed prevalence rates of 61.6%, 62.8% and 66.4%, respectively. Nonetheless, the prevalence rate in our research was greater than that discovered by KAKI et al., (2019) in Bejaia (26%) and Ferroudj et al., (2021) in Algeria’s Dry land area (12.9%). The prevalence rate in our study was also lower than the findings of Boufaida et al., (2012) in Algeria’s Est area (79%) and Ouakli et al., (2022) in Blida province (71%).
       
In this study, the prevalence of clinical mastitis at the cow level was 3.1%, which is similar with the findings of Abebe et al., (2016) in Ethiopia (3.4%) but higher than the prevalence reported by Belay et al., (2022) of 1.9%. It is crucial to note, however, that the prevalence of subclinical mastitis was significantly greater than that of clinical mastitis. This disparity might be attributed to a failure to pay attention to subclinical mastitis when treating clinical infections (Lakew et al., 2019). Subclinical mastitis is 15-40 times more common than clinical mastitis, lasts longer, has a large economic burden and frequently precedes clinical mastitis, according to Seegers et al., (2003). According to Erskine (2003), the udder’s defensive mechanism tends to reduce the degree of infection and it has been hypothesized that the risk of subclinical mastitis is higher than that of clinical mastitis.
 
Quarter level
 
The Table 2 indicates that the total prevalence of mastitis in the quarters was 35.19%, which is comparable to the findings of Abebe et al., (2016) in Ethiopia (34.7%), Dinaol Belina et al., (2016) with (29.2%) and Elbably and Asmaa (2013) in Egypt (29.08%). The hindquarters were more impacted than the forequarters, particularly the right hindquarters, which is consistent with earlier study noted above. Zeryehun et al., (2013) ascribed the higher infection rates in these quarters to their high production capacity and greater risk of fecal and environmental contamination.
 

Table 2: Prevalence of clinical and subclinical mastitis at quarter level.


 
Mastitis risk factors
 
Intrinsic risk factors (animal risk factors)
 
As shown in Table 3, the findings revealed a substantial connection between the frequency of bovine mastitis and age and parity number (p<0.05).
 

Table 3: The prevalence of mastitis in milking cows based on intrinsic risk factors.


       
Older cows showed a greater frequency of mastitis than younger cows, with cows aged 6-7 years having the greatest prevalence (87.50%) compared to cows aged 2 or 3 years (57.50%). In addition, mastitis was shown to be more prevalent in multiparous cows (76.47%) than in primiparous cows (63.33%), which is similar with earlier studies by Zeryehun et al., (2013) and Belay et al., (2022). The greater prevalence of mastitis in older cows in this research may be attributable to bigger teats and more relaxed sphincter muscles, making it easier for infectious agents to enter and grow in the udder (Radostits et al., 2007). According to Abebe et al., (2016), older cows with four or more parities are especially sensitive to mastitis due to their pendulous udders and mastitis history, which render the teats and udder more susceptible to damage and infection.
       
The research additionally showed that the stage of lactation had a significant effect on the prevalence of mastitis (p< 0.05), with a larger relative frequency in the late lactation stage (80.56%) compared to the early (67.21%) and mid-lactation phases (60.53%). This conclusion supports previous findings by Youssif et al., (2021) and Maalaoui et al., (2021). Mastitis is more common in late lactation due to recurrent and continuous exposure to infections with infectious germs during milking procedures or the removal of the teat “plug” (Youssif et al., 2021).
       
According to the findings of this study, no statistically significant correlation (P>0.05) was found between breed and mastitis or between milk output level and mastitis prevalence. This contrasts previous studies that demonstrated a substantial influence of these parameters on mastitis incidence, such as (Asmare and Kassa, 2017; Melesse and Minyahil, 2019) for milk output production and Moges et al., (2012) and Belay et al., (2022) for breed risk factors.
       
This lack of significance in our analysis might be related to breed sample variations. Our study used only imported breeds, whereas other studies used native and crossbred animals, which are known to be more resistant to mastitis infection. High-yielding cows are more prone to mastitis than low-yielding cows, according to (Radostits et al., 2007).
       
This might be due to the increased possibility of injuries developing in bigger udders, resulting in a higher risk of disease introduction. Also, the stress associated with excessive milk production may have an impact on the animal’s defensive system.
 
Extrinsic risk factors (management risk factors)
 
Data in Table 4 show that Cow cleanliness, particularly of the legs and udder, has been recognized as a risk factor for mastitis; Cows with low hygiene had a greater mastitis incidence (68.18%) than cows with good hygiene (55.56%), consistent with findings by Abebe et al., (2016) and Melesse and Minyahil, (2019).
 

Table 4: Prevalence of mastitis based on extrinsic risk factors the at cow level.


       
According to Weigel et al., (2018), environmental conditions and herd management practices have a substantial influence on animal well-being and health,  keeping the herd clean and comfortable helps lower the occurrence and severity of mastitis.
       
While using a biocide or soap to clean the udder (instead of using only water) was proven to have a substantial influence on lowering mastitis cases with rates of 42.86%, 60.53% and 74.12%, respectively. Farmers frequently refuse to use detergents for fear of affecting milk quality during milk control.
       
Wiping the udder after cleaning had a considerable influence on the incidence of mastitis 60.98% when this operation is performed versus 71.91% when it is not.
       
Whereas Idriss et al., (2013) claim that teat canals can be partially open for 1-2 hours after milking, feeding cows soon after milking is critical to prevent infections from readily infiltrating via the open teat canal. However, this study observed no significant influence on mastitis, which might be ascribed to the animals not standing for 1-2 hours due to a lack of acceptable quality and amount of feed (Asmare and Kassa, 2017).
       
This research reveals that previous mastitis history had no significant impact on mastitis incidence, in contrast to several studies such as Melesse and Minyahil (2019), who reported that previous udder infections were more likely to be re-infected than those with no previous exposure. This could be attributed to previously exposed cows retaining carriers and the limited efficacy of medications used to treat mastitis in the research area.
       
According to the findings of this study, treating dry cows had a favorable effect on lowering the prevalence of mastitis (p<0.05). As shown by Peterson-Wolfe et al., (2010), cows are most vulnerable to mastitis infections in the last seven to ten days of the dry season. As a result, it is advised that the early dry phase therapy be repeated two weeks before calving. Yet, because of fears about abortion, many farmers in the study declined to carry out systematic treatments during this time period.
The study found a high prevalence of mastitis, particularly subclinical mastitis, in the region, which can be attributed to a number of factors, including a lack of farmer awareness about the existence and diagnosis of subclinical mastitis, as well as insufficient farm management and hygiene practices. Efforts must be done to address and reduce the consequences of this problem. The study suggests educating farmers about the dangers of this disease and urging them to check for subclinical mastitis on a regular basis. Moreover, suitable management techniques for cows should be adopted during both the dry and lactation seasons, with clinical situations addressed with caution. It is thought that by doing so, the prevalence of mastitis in the region will be minimized.
       
According to the study findings, additional research is required to better understand the causes and prevention techniques of mastitis in the region. Future research should focus on identifying the mastitis-causing pathogens, as well as the specific management and hygiene practices that contribute to its high prevalence. Farmers must be taught on the importance of mastitis management, as well as how to diagnose and treat it. They should also be made aware of the negative impact of mastitis on cow health and milk production, as well as the need of maintaining correct hygiene and management procedures to reduce the risk of mastitis. Therefore, future research should focus on developing and implementing effective mastitis management strategies, as well as enhancing dairy cow health and production.
I would like to thank Dr. Benabdelmoumene Djilali and Seddar-Yagoub Abdelnour for their help, as well as everyone in the Laboratory of Sciences and Technics of Animal Production, particularly Mr. Benharrat Noureddine. My gratitude also goes to all of the veterinarians and breeders who assisted me and allowed me to conduct this study.  Finally to the Directorate General of Scientific Research and Technological Development “DGRSDT” for its support in the development of our scientific research results.
The authors declare no conflict of interest.

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