Mastitis

Mastitis is a major problem in dairy industry throughout the world. This disease causes huge economic losses to farmers in terms of production and price of milk. Price of dairy animal is based in its milk production. In case of cow front teats produce more milk (60%) than rear teats (40%) and vice versa in case of buffalo. If cow loses its front left or front right teat then there will be a huge economic loss.

According to National Mastitis Council (NMC), USA:

“Mastitis is an inflammation of mammary glands that happens in response to the injury for purpose of neutralizing infectious agent to prepare way for healing and turned to normal function.”

Normal somatic cell count in milk is 200,000 and in case of mastitis it goes to several thousands. Mastitic milk has 90 % neutrophils and 10% somatic cells. If 40 % neutrophils, there will be mild mastitis while in case of 90 % neutrophils; there will be severe mastitis.

Effect of Mastitis on Milk

• Mastitis affects the quality of milk and there is increase in the number of bacteria. Common sources of bacteria are inadequate cleaning of milking utensils, hands not properly washed, skin of udder not properly

cleaned and contamination of the teat skin. There is a direct relationship between skin and mastitis. If dirty skin then more chances of mastitis. By providing hygienic conditions mastitis can be controlled and quality of milk and its byproducts can be improved.

• Increased somatic cell count and increased neutrophils and macrophages also deteriorate the quality of milk. Increased somatic cell count claims mastitis. So there is direct relationship between mastitis and somatic cell count. But in late lactation and newly parturating animals, there is also increase in somatic cells.

• Whenever there is rise in somatic cell count, casein content falls down (which is very important protein). Similarly leakage of certain proteins from serum like albumin, immunoglobulin and transferrin into milk also occurs.

• There is also an increase in sodium and potassium ions.  

• Calcium level decreases.

• Normal pH of milk is 6.6 but it may raise upto 6-9 or more in the milk collected from subclinically mastitic animal and even more in clinically mastitic animals.

• There is release of proteolytic enzyme from blood like plasmin. Plasmin is excessive in blood but low in milk. It cannot be destroyed at 140 ^oC. If it is high in milk then deteriorate the quality of milk. Milk heated at 140 ^oC for 1.5 minute destroys the Plasmin and some other enzyme like lipase. Lipase attack triglycerides to convert them into free fatty acids, which produce offensive smell and rancid flavour in milk.

• Watery milk shows chronic type of inflammation. If watery secretion present in first few streaks (about 10 streaks) then normal but if more than it then chronic mastitis.

• Plaques present in milk show severe infection. If present at start of milking then shows infection due to S. aureus. If at the end of milking then indicates animal having TB. These plaques are normally present in milk in 1-2 days of lactation and in last 2-3 days of lactation.

Changes in Cow Milk Associated with High Somatic Cell Count

Types of Mastitis

Latent Mastitis:
Pathological organisms present in milk but no swelling of udder and normal cell count.

Sub Clinical Mastitis:
Bacteria and somatic cells present in milk and change in composition of milk but no gross lesions.

Clinical Mastitis:
It is divided into three categories depending upon severity:

(a): Acute: There are obvious symptoms of inflammation present on udder, change in colour and composition of milk and increased temperature.

(b): Subacute: No obvious change in udder but clots and plaques present in the milk.

(d): Chronic: Every acute infection develops into chronic infection if not treated. In this phase major changes are fibrosis of udder. There may be fibrotic mass particularly in teat canal.

Aseptic/Non Specific Mastitis:
It is due to trauma or injury to the udder.

Pathogens Involved in Mastitis

Contagious Pathogens:
They spread from quarter to quarter through contamination by hands, flies, wounds etc. They always require host e.g. Staph aureus, Mycoplasma, Pasteurella. They have very limited life in environment. In Pakistan mastitis caused by Staph aureus and Streptococcus agalectia is 70-80 % of mastitis and rest of it is caused by environment (E. coli)

Environmental Opportunist:
The primary source is the environment in which the animal lives. They spread by direct contact of the teats to the bedding or mud, dirt and manure. Examples are Coliform species like E.coli, Klebsella, Streptococcus uberis, streptococcus agalactae, and streptococcus faecalis etc.

Opportunist Pathogens:
This group of mastitis pathogens includes around 30 different species of the genus Staphylococcus (other than Staph aureus) and Corynebacterium bovis. They are normally present on the teat skin and streak canal. Therefore they are in an opportunistic position to colonize the teat canal and penetrate the udder.  

Endogenous Pathogens:
Etiological agents of systemic diseases with mammary gland involvement like Leptospira, Mycobacterium bovis etc.

Sources of Mastitis

• Hands of milker. Staph aureus is present on skin, naries of human if no proper bath. He will shift from one herd to other.

• Lack of proper management i.e. proper teat dipping is not carried out, no antiseptic solution is used and no sanitation measures are taken.

• Trauma during sitting posture or due to kicking udder leads to mastitis.

• Folded thumb milking particularly in villages damages the teat and causes adhesion and increases the chances of mastitis.

• In old animals teat canal is fragile and immune system is weak. So there are more chances of infection in old animals.

 
Pathogenesis of Mastitis

There are three phases of mastitis:

1. Invasive/Invasion Phase:
It depends upon no. of bacteria. When bacteria enter, they multiply and increase in population. So certain no. of bacteria is required for invasion. This determines the infection rate. Any damage to teat canal provides opportunity to bacteria to invade and multiply. Loose sphincter will also provide the opportunity of entrance and adhesion to bacteria.

2. Infection Phase:
Whenever bacteria enter, the infection depends upon the nature of bacteria. If highly pathogenic, then severe infection.

Some bacteria are susceptible to antibiotics and some are resistant. Staph aureus if capsulated it resists and more chances of infection.

If less immunoglobulins present in udder or teat canal then more chances of infection.

Pre existing leukocytes if more in number; less chances of infection. They cause phagocytosis of bacteria.

Stages of lactation also affect the severity of infection e.g. in lactating phase milk flow does not allow bacteria to attach. Similarly during lactation, treatment is difficult because antibiotics may flow in milk. Dry period is the best time to treat mastitis because antibiotics will stay for longer time in udder. The best time for infection is also the dry period; bacteria once entered, remain there and cause infection.

3. Inflammation Phase:
Inflammation depends upon the pathogenecity of bacteria and the production of endotoxins, particularly the endotoxins of S. aureus (α and ß) and E.coli that cause damage to the capillaries of udder and cause the release of fluid in subcutaneous parenchyma tissue. In case of E. coli there is huge number of endotoxins and huge damage and inflammation. But S. aureus endotoxins cause less damage to the vessels. They cause chronic mastitis and more fibrosis. Their ultimate target is to damage milk alveoli. 

Clinical Findings of Mastitis

• There is change in udder size; size increases in acute cases while in chronic cases it decreases due to fibrosis and atrophy

• Consistency of udder is soft and hot in acute but hard in chronic due to fibrosis

• In case of endogenous spread (like E.coli) systemic reaction may occur and cause temperature, anorexia, depression and whenever increase in fever animal is off feed

• In S. aureus infection there is rise in temperature in early stages

• In case of streptococcus no rise in temperature while in case of E.coli high temperature.

Diagnosis of Mastitis

Direct Microscopic Method:
Put 0.1 ml of milk sample on slide, dry it and stain it with Newman Lampert’s Stain and then count somatic cells with the help of microscope in certain area. Multiply the cell counted with a working factor of microscope, it will give the number of cells per ml of milk.

The Coulter Counter:
It allows the rapid and accurate determination of the number of particles above a certain size in a suspension.

Fossomatic Instrument:
It is an automatic microscopic method for counting cells in liquids. Cells are stained with ethidium bromide and are then excited with a high energy lamp, causing them to emit light energy which is detected electronically, the results being displayed are printed out for each successive sample. From the sample 0.2 ml is taken and transferred to a glass container on a rotary table where it is mixed with preheated buffer and dye and stirred well. Part of the mixture is then transferred to the periphery of a rotating disc, which serves as an object plane for the microscope. The film is illuminated by a xenon arc lamp, the light passes through lenses and a blue filter. Each cell produces an electrical pulse, which is fed to an amplifier. The printout of the count needs to be multiplied by 1000 to give number of cells per ml.

NAGase Assay:
NAGase (N-acetyl glucosamide) is a lysosomal enzyme. Its level increases due to mastitis which can be detected for the diagnosis of mastitis. Kits to detect are available.

California Mastitis Test:
A reagent is used in California Mastitis Test which is alkaline in nature. Whenever mastitis occurs, there will be destruction of leukocytes due to phagocytosis. As a result DNA content increases in milk which is acidic in nature and causes the increase in the acidity of milk. Any alkaline reagent if added, it will neutralize the milk. The reagent added in California mastits has alkyl aryl sulfoxide which will cause the precipitation or gel formation in milk.

Surf Field Mastitis Test:
A test discovered by Prof. Dr. Ghulam Muhammad, Department of Clinical Medicine and Surgery, Faculty of Veterinary Science, University of Agriculture, Faisalabad. Make 3 % surf field solution: add 6 teaspoons of surf in half litre water, mix it, filter the solution and heat it. Take milk and add equal volume of 3% solution, swirl this mixture for half minute and then examine for precipitation or gel formation (In case of mastitis). The test solution is stable for 6 months at room temperature. The solution should be shaken well before use.

Strip Cup Method:
It is the simplest method. Take few streaks in cups with black background and observe any abnormality e.g. clots.

Ground Test:
Take few streaks on ground. If the absorbance of streak is quick in ground then animal is –ve for mastitis but if the absorbance is slow then milk is mastitic. Late absorbance is due to pus as mastitic milk is pus containing milk.

Measuring Electrical Conductivity of Milk:
The concentration of sodium and chloride increases in milk as a result of mastitis. These ionic changes together with increase in milk pH and decrease of milk fat lead to increased electrical conductivity of milk. Electrical conductivity measuring can be converted into computer readable signal. Therefore, this method is easily applicable to online automatic monitoring of udder health and can be installed in milking machines. The method however, is not very specific for mastitis.

Treatment of Mastitis

We have to target three things:

• Specific treatment

• Symptomatic treatment

• Supportive treatment

First of all determine the nature of mastitis and on the basis of nature of mastitis and its etiological agent select antibiotics. Antibiotics can be administered through intramuscular or intramammary route. Whenever given through intramuscular route the best drugs to be given are macrolides (erythromycin, tylosin), oxytetracyclin, cephlosporin, chlorofluracin, and quinolines (norfloxacin). Tribrissen is also good. The best approach is to give antibiotics through intramammary route. Commercial Intramammary tubes are also available in market. For subsiding inflammation steroids may be used in acute inflammation otherwise NSAIDS.

Vitamin AD₃E may be used to increase immunity. To enhance immunity, trace elements like zinc, copper, and iodine may also be used. Biotechnological products like Interleuken-1, Interleuken-2, and lysostaphin are also used.

Udder Toilet:
It refers to infusing larger quantity of weak antiseptic solution into quarter and withdrawing it. For this purpose acriflavin solution (1:10000 boiled in water) is generally used. Remove milk from the udder and infuse the solution, remain there for 5 minutes and then remove out with the help of syringe.

Permanent Drying/Blocking of Affected Quarter:
If quarter does not respond to antibiotic, infuse tincture iodine into that quarter; it will cause irritation and block that quarter permanently. 50 ml of chlorhexadene can also be used.

Basic Remedies:
Garlic, lemon , ginger, red chilies, black pepper, black zera, dried ginger….dry for 5 days. Mix them in flour, sprinkle water and wrap in newspaper. Give for 5 days.

250 ml lemon and 500 gram sugar may also be given.

250 gram garlic and 1000 ml milk is cooked and given to animal for 2-3 days.

Control of Mastitis

Two main objectives of control:

1.    Prevention of new infection in the herd

2.    Reduction of duration of existing infection

There are five different plans to control mastitis which were devised by NMC (National Mastitis Council), USA in 1990.

• Pre milking teat dipping

• Post milking teat dipping

• Dry cow therapy

• Prompt treatment of clinical cases

• Culling of chronic mastitic animals from the herd

Pre Milking Teat Dipping:
Dip the teats before milking with the . Dry the teats after pre dipping by towel or tissue. Do not use same towel for more than one animal. Teat cups are available having antiseptic in it like iodofores (0.1-1 % iodine). Dip the teats one by one for 2-3 seconds. Quaternary ammonium compounds, chlorhexidine, and sodium hypochlorite may also be used as dip solution.

Post Milking Teat Dipping:
Organism is present in environment and teat skin. In order to avoid it we go for post milking dipping. After milking teat sphincter remains open for 30 minutes to 2 hours. It is ideal time for entry of organism to teat canal. So perform teat dipping after milking. Solutions for post milking teat dipping are same as for pre milking teat dipping.

Dry Cow Therapy:
The rate of new udder infections increases dramatically shortly after drying off and remains elevated during the first 3 weeks of mammary involution. During the first few days after drying off, the animal goes through a period of stress that may predispose her to infections.  Up to 40% of all new intramammary infections are established during the first two weeks of the dry period and without dry cow therapy, 10 to 15% of the quarters will become infected during the dry period. Dry cow treatment is aimed at preventing new infection from occurring during this period of increased susceptibility as well as curing existing infection and is beneficial against both contagious and environmental pathogens. Advantages of dry cow treatment include the following:

• The cure rate is higher than during lactation

• Higher concentrations of drugs can be used

• New infections during the dry period are reduced except first 3 weeks after drying off

• Drug residues in milk are avoided

Prompt Treatment of Clinical Cases:
Despite implementation of effective mastitis control measures, clinical cases still occur. These cases should be treated promptly to maximize the chances of recovery. Treatment of clinical cases involves intramammary and parenteral administration of antibiotics. Extreme care must be taken whenever anything is being infused into udder. Careless treatment procedures can result in udder infections resistant to treatment. Approach treatment in the same way a surgeon approaches surgery.

• Wash hands with soap and water

• Wash teats and udder in sanitizing solution

• Thoroughly dry teats and udder with single service individual paper towels

• Dip teats in an effective germicidal teat dip

• Allow 30 seconds of contact time before wiping off teat dip with an individual towel

• Thoroughly scrub the teat end with a cotton swab soaked in alcohol. If all four quarters are being treated, start by cleaning the teat farthest from you and work toward the closest teat.

• Preferably use commercial antibiotic products in single dose containers designed with partial insertion arrangement formulated for dry cow therapy in single dose containers. Do not allow the sterile cannula to touch anything prior to infusion.

• After infusion, remove cannula, squeeze teat end with one hand, massage antibiotic up into the quarter with the other hand. Dip teats in an effective germicidal teat dip after treatment.

• One can also prepare infusion solutions and infused with the help of plastic part of IV catheter (Branula # 18 or 20).

Culling of Mastitic Animals:
Cull mastitic animals from herd.

Managemental Control

• Segregation of healthy and infected animals and milking of healthy animals ahead of infected animals

• Cull chronically infected animals

• Purchase mastitis-free animals (Surf Field Mastitis test -ive animals). Keep them segregated for about 2 weeks. Retest with Surf test before adding to already existing herd.

• Mastitis control in heifers: The gradual building up of a separate heifer herd, clean at the outset, is of great importance. The occasional appearance of mastitis in first-calving heifers is said to be due to the habit of female calves sucking one another's teats. This problem should be addressed through appropriate managemental practices.

• Proper treatment of teat and udder wounds

• Fly control

• General cleanliness of farm

• Proper disposal of mastitic milk of clinical cases

• Prepartum milking of animals which develop mastitis close to calving: Many dairy animals which have subclinical infections during the dry period often develop severe swelling of the udder and teat a few weeks or days before calving. If such is the case, one should start milking the diseased quarter (s) before parturition. Appropriate treatment should also be given.

• Proper nutrition: The feed should be balanced in terms of energy, protein contents, as well as vitamins and minerals.

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