Mastitis

• Inflammation of mammary gland regardless of its cause is called mastitis.
• It is characterized by physical, chemical and usually bacteriological changes in milk and pathological changes in glandular tissue of udder.
• Clinical cases are characterized by abnormal milk, udder swelling and systemic signs such as elevated temperature, lethargy and anorexia.
• In subclinical cases, there is no visible changes in appearance of milk or udder but milk production decreases, composition is altered and bacteria are present in secretion.

Etiology:

• Bacteria: Staphylococcus aureus, agalactiae, Str. zooepidemicus, Str. pyogenes, Corneybacterium pyogenes, E. Coli, Brucella abortus, Pseudomonas pyocyaneus, Leptospira pomona, Pasteurella multicoda, Kleibsella spp
• Mycoplasma: Mycoplasma bovis
• Fungus: Trichosporon sps., Aspergillus fumigatus, Candida spp, Cryptococcus neoformans
• Virus: IBR, Vesicular stomatitis

Epidemiology:

• It is recognized as one of the costliest diseases affecting dairy cows.
• It is estimated that there is reduction in milk yield by 30% and butter fat by 25%.
• Milk are of inferior quality and considered unfit for human consumption.
• Disease has got morbidity rate of 40% and quarter infection rate is 25%.
• The average incidence of episodes of clinical mastitis is about 10%
• Case fatality rate varies widely depending largely on the identity of the causative organism.
• In most countries, surveys in dairy herd indicate that prevalence of infection of mastitis pathogens about 50% of cows.
• Infection may occur at any time, for example, milking, between milking, during the dry period, or prior to the first calving.
• Prevalence of sub-clinical mastitis was found to be 62.77% in commercial dairy cattle in a study conducted in Rupandehi district.

Economic Importance:

• The economic losses sustained by farmers due to mastitis has been identified as follows:
  • Milk discarded due to abnormal characters and presence of antibiotics.
  • Reduced milk production due to clinical and sub-clinical mastitis.
  • Decreased market value of cow due to damage of quarters.
  • Cost of veterinary services to treat acute and chronic cases.
  • Cost of drugs to render treatment.
  • Cost of increased labor to care infected cow.

Transmission:

• The site for infection is teat canal. Through teat canal, infection reaches to mammary gland.
• Infective agents usually come from two sources; udder and environment.
• Through contamination by milkers with infected hand
• Contamination of milker’s hand, clothes and machine cup by milk from affected quarter may lead to the spread of disease to other non-infected teats.
• Fly and other insect may also spread the infection from one place to other.
• Through bedding ground by discharges of affected gland.

Pre-disposing factors:

• Age: Prevalent in higher age group. Incidence increase with increase parity.
• Breed: Common in exotic and crossbred cows than zebu
• Stage of lactation: More incidence at start and end of lactation
• Incomplete Milking: Milk retained in udder acts as conducive factor.
• Size of herd: More frequent in large herd
• Trauma: Mechanical injury to teat or udder helps microorganism to enter organ
• Hygiene: Poor sanitation and bad hygiene help bacterial multiplication
• ROP: Frequent case of mastitis in cows with ROP
• Infected Udder: Previously infected udder is more likely to be infected.

Pathogenesis:

Infection takes place through teat canal. It occurs in two stages:

a. Invasive stage

• Organism in environment gets contact with teat orifices through bedding, urine, feces.
• Through exterior of teat canal during milking, organism invade the mammary gland.
• Organism reaches to glandular tissue through teat canal and set up infection there.

b. Infection stage:

• Organism reaches the secretory cells and colonize there.
• Organism starts to multiplies in secretory cells and starts damaging cells.
• Some organism produces toxins inside the cells causing toxemia.
• Due to inflammatory process, edema of interstitial tissues occurs. Exudation process give rise to changes like fibrosis and involution of acini
• Due to fibrosis, udder becomes hard. Acini collapse and replaced by granulation tissues, interstitial spaces are infiltrated by lymphocytes.
• Glands becomes reduced in size and turn hard in consistency which is termed as “shrunken quarter”.

Clinical Findings:

• Clinical findings vary on type and extent of injury. Clinical mastitis can be classified as:

i. Per-acute cases

ii. Acute mastitis

iii. Sub-acute mastitis

iv. Chronic mastitis

i. Per-acute mastitis:

• It is most serious form which endangers the life of animal.
• Body temperature gets elevated; usually 106-107°F
• Off-fed, Respiratory distress
• Udder is swollen, hot and painful to touch
• Decreased milk production and exudates are usually blood stained.

ii. Acute mastitis:

• Udder becomes swollen and painful.
• Milk may be replaced by custardy yellow material or brown fluid with flakes or clots.
• Infection may be localised in one quarter or entire udder may be involved.
• Udder may become non-functional and recovery is achieved only through judicial treatment.

iii. Sub-acute mastitis:

• Visible changes are observed in milk but practically no change in udder tissues.
• Milk secretion becomes watery.

iv. Chronic mastitis:

• It is the terminal stage of disease.
• Udder becomes hard due to fibrosis.
• Supra-mammary lymph nodes become palpable.
• Quarters may be thickened, firm, nodular and at times atrophic.
• Milk may appear as yellowish fluid or white with clots and flakes. Sometime, it may look green or yellow-green and foul smelling.

Diagnosis:

• Physical examination of udder: Shape, size, consistency and contour of udder should be viewed properly. Signs of inflammation and shape changes are usually observed.
• Tests for abnormalities in milk; strip cup test, bromothymol blue test (BTB), bromocresol purple test, chloride test, Hotis test
• CMT: It is based on increased leukocyte count and increased alkalinity of milk sample. For this test, equal amount of milk is collected in CMT paddle. Equal amount of test reagent is added. Milk and the reagent are rotated by movement of paddle. Positive milk will turn to greenish blue due to alkalinity. Due to increased number of leukocytes, a precipitate or gel is formed.
• Culture examination of milk in various media such as blood agar media, nutrient agar, Mac-Conkey agar
• Serological test: Slide agglutination test, precipitation test

Differential Diagnosis:

1. Udder edema:

• Usually observed in first calf heifer after parturition.
• Doughy swelling which extends upto navel region
• No abnormality in milk.
• Respond to diuretic therapy

2. Blood in milk:

• Observed following calving
• It usually disappears after few days
• It may respond to hemostatic therapy

3. Leptospirosis:

• Routine bacteriological test may fail to reveal causative agent.
• Blood in milk
• Agglutination and dark field illumination are required for confirmation.

4. Tuberculosis of udder:

• Gradual enlargement of udder.
• There is no pain or hotness.
• Reduction in milk yield but no abnormality in milk initially.
• Z-N stain may reveal causative agents.
• Supramammary lymph glands are swollen and hard.

5. Actinomycosis of udder:

• There is development of hard nodules.
• They are not painful.
• Examination of pus may reveal sulfur granules.

6. Cyst and abscess:

• They produce localised swelling.
• In case of abscess, they erupt.
• In case of cyst, there is enlargement due to accumulation of broken-down milk.

Treatment:

• Removal of secretion as much as possible. If necessary, sterile teat syphon should be used to drain out milk.
• Intramammary antibiotic preparations should be used for local treatment. Intramast or Zymast; Penicillin Cloxacillin
• Parenteral administration of antibiotics; Gentamicin sulphate @3-5 mg/kg, IV or IM, BID for 5-7 days. Cephalosporin; ceftiofur, ceftriaxone is used intravenously.
• Supportive treatment includes parenteral administration of large quantities of isotonic fluid containing glucose, antihistamines and corticosteroids. Isoflupredone acetate @10-20 mg/cow at 24 hours interval.
• Hot fomentation of mammary gland with magnesium sulphate to relieve inflammation.
• Enzymes such as streptopeptidase, streptodornase hylase gives valuable help.
• NSAID; Meloxicam @0.5 mg/kg, IM or IV to relieve fever
• Antihistaminics preparation such as chlorpheniramine maleate @ 10-15 ml, IM to counter allergic reaction and irritation.
• Hormonal therapy such as oxytocin may be infused to let down all milk or complete removal of milk.
• Nutritional therapy such as Vitamin E-selenium preparation, Zinc for aid in recovery.

Control Measures:

• Isolation of affected animals and treatment as soon as possible after diagnosis.
• Treatment of all quarters at drying off.
• Dipping of teats in iodophor solution containing 1% available iodine after each milking.
• Cleaning and disinfecting milking machine and cup where the machine are used.
• Bedding of concrete floor with straw, saw dust or sand. Sand is ideal bedding material.
• Supplementation of vitamins and minerals. Vit. A increases provide immunity and resistance against disease.
• Disinfection of hands prior to milking and after milking.
• Udder and hand of milker should be washed with antiseptic lotion before and after milking.
• Sealing of teat: it is done by making a film by dipping teats in solution of acrylic latex.
• Healthy non-infected udder should be milked first and known infected cows/teat should be milked.
• Newly introduced cow should be milked separately until the position of it is known. Cows should be screened through CMT.
• Udder should be washed and dried prior to milking.
• Calves should be prevented from suckling milk of mastitis cow.
• Mastitis milk should be properly disposed off. 5% phenol may be added to the infected milk at the time of disposal.
• Floor of the milking shed should be washed with running water. First strip of milk shouldnot be allowed to fall on the floor, they may be stripped in separate container.
• All the equipments and containers should be cleaned and washed properly.
• Control of fly population should be attempted. Insecticides fly repellant spray are to be made in house and surrounding.