Disease Information

Bovine Mastitis

Mastitis (commonly known as saroo) is one of the most contagious disease of dairy animals. Out of all the livestock diseases in Pakistan, many field surveys have ranked mastitis as number one disease of dairy animals. It is the inflammation of udder that often leads to infection. Inflammation results either due to bacterial invasion in teat canal or as a result of mechanical, chemical and thermal injury to cow’s udder. According to an estimation, almost 25% of the milking animals suffer from Mastitis.

Economic losses due to Mastitis

Mastitis (commonly known as saroo) is one of the most contagious disease of dairy animals. Out of all the livestock diseases in Pakistan, many field surveys have ranked mastitis as number one disease of dairy animals. It is the inflammation of udder that often leads to infection. Inflammation results either due to bacterial invasion in teat canal or as a result of mechanical, chemical and thermal injury to cow’s udder. According to an estimation, almost 25% of the milking animals suffer from Mastitis.

Effect on milk composition

Mastitis cause considerable changes on milk composition including:

  1. The amount of major milk protein, casein, decreases and lower quality whey proteins increases which adversely affects the quality of dairy products such as cheese.
  2.  Most of the calcium in milk is associated with casein and the disruption of casein contributes to lower calcium level in milk. 
  3. Lower levels of calcium in milk results in impaired coagulation characteristics of milk.
  4. Increased vascular permeability causes other serum proteins such as serum albumin, immunoglobulins and transferrin pass into the milk which reduces heat stability of mastitis milk. 

Types of Mastitis

There are basically two major kinds of mastitis; clinical and sub-clinical mastitis. But there are some uncommon types as well.

  • Latent Mastitis
  • It is asymptomatic.
  • Pathogens are present in milk.
  • But there is no swelling of udder. 
  • Milk somatic cell count is also normal.
  • The infection can become active under favorable conditions.


  • Clinical Mastitis

In this type, one or more than one teat in udder is inflamed. The udder turns reddish and the animal feels severe pain. Milk production and quality decreases as flakes and clots can be visible in the milk. Sometimes, there is no milk production as well. It is further divided into 3 subtypes depending upon the severity of disease.

  1. Acute: 
    1. Changes in udder occurs such as udder inflammation and redness.
    2. Systematic illness such as fever, weakness, and increased heart rate.
  2. Subacute: 
    1. There is no obvious change in udder. 
    2. Clots and plaques present in the milk.
  3. Chronic: 
    1. If infection persist, it can develop into chronic mastitis. 
    2. If not treated on time, one or more teat becomes fibrosed and the udder shrinks.
    3. The milk becomes saline.
    4. Chances of recovery are very low so culling of infected cow is recommended.

Note: In case of clinical mastitis, consult the doctor immediately.

  • Sub-clinical Mastitis
  • This type of mastitis is far dangerous than the clinical one as there are no visible signs of infection in this case.
  • There is no inflammation of udder and no gross lesions are found.
  • The animal does not suffer from fever in this case, but animal becomes sluggish.
  • Milk production does not stop completely. But reduction in milk production and quality takes place.
  • Pathogens and somatic cells are present in milk changing its composition.
  • It is difficult for farmers to detect the presence and intensity of this disease visually. But its diagnosis is very easy and can be done by different farm testing including CMT (California Mastitis Test), and SFMT (Surf Field Mastitis Test).

Causes of Mastitis Spread

There are many causes that can help in the quick spread of mastitis. These include:

  1. Microbe entry into the teat canal
  2. Grazing or feeding at unhygienic environment
  3. Feeding the calves immediately after the milking
  4. Fungal contamination in the fodder
  5. Unsanitary farm and its environment
  6. Presence of ticks in the farm
  7. Milking the animals without sanitizing the hands
  8. Milking the animals without sanitizing the teats and udder
  9. Milking of the animals by inexperienced persons as it can cause mechanical injury to animals
  10. Ignoring the teat injuries and left them untreated
  11. Milking in the dirty utensils
  12. Dung and urine in the farm shed 

Pathogenesis of Mastitis 

  • After milking, the teat canal remains open for about 20-25 minutes. This is the perfect time for microbes to enter in the canal. 
  • Microbe generally invades the udder by entering through the teat canal and after entry, they grow in the udder in the form of the colonies.
  • After growth, these microbes secrete toxins that destroys milk producing cells that adversely affects milk yield and quality.
  • The milk producing cells that are dead once can’t be recovered or regenerated and results in the low milk yield from the infected animal. 
  • Inflammation of udder occurs due to the microbes and their toxins and the animals may suffer from severe pain and fever.
  • The treatment of mastitis is costly and any delay in the treatment of animals can result in the reduction of animal value or premature culling of the animal.
  • The mastitis causing microbes grows rapidly in the following environment:
  1. Unhygienic farm environment
  2. Affected udder surface
  3. A dirty and muddy place
  4. Heaps of dung around shed

Causative Organisms of Mastitis

  • Contagious Pathogens: 
  • Contagious microorganisms are usually found on the udder or teat surface of infected cows. 
  • They are the primary source of infection between uninfected and infected udder quarters, usually during milking. 
  • They are mostly involved in sudden outbreaks of clinical mastitis.
  • Pathogens included are Staphylococcus aureus, Streptococcus agalactiae, (both account for 70-80% of bovine mastitis in Pakistan) Corynebacterium bovis and Mycoplasma bovis.
  •  
    1. Environmental Pathogens: 
    • They are found in the immediate surroundings of cows and buffalos such as on bedding material, manure and on soil as well. 
    • Mastitis caused by environmental organisms is essentially opportunistic in nature. 
    • It only becomes established if the immune system of the host is compromised or if sanitation and hygiene is not adequately practiced.
    • These include streptococcal strains other than S. agalactiae, such as Streptococcus dysgalactiae, Streptococcus uberis and Streptoccous bavis. Enterococcus faecium, Enterococcus faecalis and coliforms such as Escherichia coli, Klebsiella pneumonia and Enterobacter aerogenes are also included. 
    1. Opportunistic Pathogens: 
    • They colonize on teat skin and are less frequently involved in clinical mastitis.
    • This category involves coagulase-negative staphylococci (CNS). 

    Detection of Mastitis

    • Clinical mastitis is detected based on physical appearance of udder and milk. Milk may have an abnormal color, may contain pus or blood. Udder may be inflamed and swollen.
    • Subclinical mastitis cannot be detected easily, as milk appears normal but has an increased somatic cell count. On-farm screening tests are performed for the detection of subclinical mastitis.

    On-Farm Screening Tests:

    • Surf Field Mastitis Test: 
    • Researchers at University of Agriculture, Faisalabad, Pakistan have discovered this test. 
    • For this test, 3% solution of detergent (5 spoons of detergent in half liter water) is used as a reagent. 
    • Milk sample form each quarter is collected in four-compartment plastic puddle and mixed with 3% detergent solution for 10 seconds. 
    • Note the change in composition of milk (thickening of milk in case of mastitis).
    • California Mastitis Test:
    • It is the most reliable and rapid method for the detection of subclinical mastitis. 
    • It helps to determine somatic cell counts in infected cow. 
    • Sample of milk is collected from each quarter into a four-compartment plastic puddle and CMT reagent is added. 
    • Rotate the plastic puddle to mix the contents for 10 seconds. 
    • Note the results. The more gel formation, the higher the score.
    • Strip Cup Method:
    • Strip cup is used for detection. 
    • First stream of milk from each teat is squirted on strip cup. 
    • Examine the lumps, clots or other abnormality in milk.
    •  

Causes of Mastitis Spread

There are many causes that can help in the quick spread of mastitis. The

    • Ground Test:
    • Few streaks of the milk are dropped on the ground.
    • If the streak is quickly absorbed in ground, then the animal is negative for mastitis and vice versa.
    • Slow absorbance is due to the presence of clots and pus in the milk.

    Laboratory tests:

    • Direct Microscopic Counts:
    • In this method, 0.01ml milk is spread over a circular 1 cm2 area on a special slide. 
    • It is dried, stained and examined microscopically under oil-immersion lens.
    • Nucleated somatic cells are counted and multiplied with working factor of microscope. 
    • It will give the number of cells per ml of milk.
    1. pH determination Test:
    • Normal pH of milk is 6.4 to 6.8 whereas mastitic milk becomes alkaline due to elevated amount of chloride ions.
    • Methylene Blue Reduction Test:
    • Microorganisms present in milk remove oxygen. 
    • When all oxygen and reducible components of milk are removed, the color of methylene blue will be changed to methylene white.

    Identification of Pathogen:

    • ELISA, Probe-based assay, Bacterial culture and multiplex PCR are run for the identification of pathogens present in milk sample.

se include:

  1. Microbe entry into the teat canal
  2. Grazing or feeding at unhygienic environment
  3. Feeding the calves immediately after the milking
  4. Fungal contamination in the fodder
  5. Unsanitary farm and its environment
  6. Presence of ticks in the farm
  7. Milking the animals without sanitizing the hands
  8. Milking the animals without sanitizing the teats and udder
  9. Milking of the animals by inexperienced persons as it can cause mechanical injury to animals
  10. Ignoring the teat injuries and left them untreated
  11. Milking in the dirty utensils
  12. Dung and urine in the farm shed 

Pathogenesis of Mastitis 

  • After milking, the teat canal remains open for about 20-25 minutes. This is the perfect time for microbes to enter in the canal. 
  • Microbe generally invades the udder by entering through the teat canal and after entry, they grow in the udder in the form of the colonies.
  • After growth, these microbes secrete toxins that destroys milk producing cells that adversely affects milk yield and quality.
  • The milk producing cells that are dead once can’t be recovered or regenerated and results in the low milk yield from the infected animal. 
  • Inflammation of udder occurs due to the microbes and their toxins and the animals may suffer from severe pain and fever.
  • The treatment of mastitis is costly and any delay in the treatment of animals can result in the reduction of animal value or premature culling of the animal.
  • The mastitis causing microbes grows rapidly in the following environment:
  1. Unhygienic farm environment
  2. Affected udder surface
  3. A dirty and muddy place
  4. Heaps of dung around shed

Causative Organisms of Mastitis

  • Contagious Pathogens: 
  • Contagious microorganisms are usually found on the udder or teat surface of infected cows. 
  • They are the primary source of infection between uninfected and infected udder quarters, usually during milking. 
  • They are mostly involved in sudden outbreaks of clinical mastitis.
  • Pathogens included are Staphylococcus aureus, Streptococcus agalactiae, (both account for 70-80% of bovine mastitis in Pakistan) Corynebacterium bovis and Mycoplasma bovis.
  •