Bovine Mastitis: An Important Dairy Cattle Disease

by Anita Tiwari

Ph.D. Scholar, School of Public Health & Zoonoses, GADVASU, Ludhiana – 141004

Mastitis involves an inflammation of the mammary gland through bacterial infection, trauma, or injury to the udder. One of the most common diseases incurring huge losses to the diary industry, it not only reduces the productive capacity of the cows but is also expensive to treat. Mastitis, mainly of tow types – sub-clinical and

clinical, is responsible for heavy economic losses due to reduced milk yield, milk discard after treatment, treatment costs and premature culling.

Mastitis an inflammation of the mammary gland caused by bacterial infection, trauma, or injury to the udder, remains the most common and expensive disease affecting dairy

cattle throughout the world. Mastitis is caused by several different bacteria that can invade the udder, multiply there and produce harmful substances that result in inflammation.

It reduces the productivity of the cow as well as the quality of  milk causing enormous losses for breeders and consequently, to the national income of the country.

Etiology

This disease can be caused by an infectious or non-infectious etiological agent. The infectious type of mastitis is the most important one that frequently occurs due to infection by one and / or the other pathogens, such as bacteria, viruses, mycoplasma, yeasts and algae (DaRong et al, 2010). Classically, the mastitis pathogens may either be contagious or environmental. The contagious pathogens are the organisms which are adapted to survive

within the host, in particular within the mammary gland, and are capable of establishing sub-clinical infections, which are typically spread from cow to cow at or around the time of milking (e.g. Staphylococcus aureus, Streptococcus agalactiae, Str. Dysgalactiae) (Bradley 2002). The environmental pathogens are opportunistic invaders of the mammary gland which typically invade, multiply, engender a host immune response and are rapidly eliminated (e.g. Escherichia coli, Klebsiella species, Enterobacter aerogees, Streptococcus uberis,  Corynebacterium bovis, Mycoplasma species, Serratia, Pseudomonas, Proteus species, environmental Streptococci) (Bedada and Hiko, 2011). Despite intensive research, the etiology of around 20-35% of clinical cases of bovine mastitis cannot be established readily.

Types of mastitis

Mastitis is mainly of two types. It may be Sub-clinical type in which although there are no visible changes in the appearance of the milk and / or the udder, milk production decreases by 10% to 20% with undesirable effect on its constituents and nutritional value rendering it of low quality and unfit for processing (Rady and Sayed, 2009). Sub-clinical mastitis is the most common and economically most harmful; and gradual decline in milk production is its characteristic feature although there are no visible or palpable external changes inspite of the presence of infection and inflammation in the udder. The milk has a normal or slightly increased somatic cell count. Normally the bacterial count of herd milk is not affected and will remain below 50,000 per ml. It is estimated that 50% of all cows have subclinical mastitis in one quarter of their udder. The other type is Clinical Mastitis in which there is an

inflammatory reaction characterized by heat, pain, swelling and redness of the udder, along with reduced as well as an abnormal nature of milk yield. It is usually accompanied by a mild fever and the animal is depressed. The affected quarter is sensitive to

touch and painful to the animal. If acute mastitis is not attended and the inflammatory process persists for long, it gets converted into chronic mastitis which may further lead to a progressive fibrosis (hardness) of the gland thereby rendering the milk secreting tissue unable to produce any more milk. These changes are generally incurable and permanent. Often one or more quarters or even the whole udder may become permanently dysfunctional.

Effect on dairy industry

Mastitis is responsible for heavy economic losses due to reduced milk yield (up to 70%), milk discard after treatment (9%), treatment costs (75), premature culling (14%) (Bhikane and Kawitkar, 2000), decrease in milk quality and price due to high bacterial / somatic cell count,

increased risk of subsequent mastitis, herd replacement, antibiotics residue in milk and its products and rejection by processor and consumer (Harmon, 1994). Though cows with clinical mastitis have more dramatic changes in milk yield and composition than cows with subclinical mastitis, the losses due to latter are more severe than those due to the former (Muhamed et al, 2011). The Indian diary industry suffers and annual loss of approximately 526 millions dollars due to mastitis, 70% of which is due to subclinical mastitis (Rady and Sayed, 2009).

Diagnosis

While acute clinical mastitis is easily suspected/recognized even by farmers and is readily diagnosed due to udder swelling, pain and drastic decrease in milk production, the sub-clinical mastitis has neither visual abnormalities in the mammary gland (swelling, hotness, cracks etc.) nor in the milk (blood, clots, flakes etc.). Therefore, routine physical examination of udder and diagnostic screening tests for early detection of mastitis and proper treatment

of affected animal are of paramount importance in order to minimize losses due to sub-clinical and clinical mastitis. Physical examination of udder: It can be done by visual

observation and digital palpation. Physical examination of each gland must be made immediately after milking when the hormone stimulation has ceased and the udder is

completely relaxed and empty (Sharma et al, 2009).

Milk examination

The visible abnormalities like presence of flakes or clots in the milk, changes in the consistency and colour of milk (which may be thin or watery and at times yellow in color)

are noted (Sharma et al, 2009). For convenience milk examination tests may be divided into two groups, viz: — Direct or cultural test: These are the standard tests for determining the presence and identity of mastitis organisms in the milk, but are time consuming and

require technical skill and laboratory facilities. — Indirect Tests: These depend upon the development of palpable lesions in the udder or changes in the composition of milk. Indirect tests (e.g. Somatic cell count, California Mastitis Test, Strip cup test etc.) are useful in determining the quality of milk in the absence of laboratory facilities. These are simple,

economical, fast and easy to use as a cow-side test.

Treatment

The treatment of clinical mastitis is generally based on clinical signs, number of episodes and the likelihood of response. It should include supportive therapy, milk-out, and observation until culture results are available the following day. In case of contagious pathogen, all 4 quarters should be treated to ensure elimination of pathogen and to prevent possible cross-infection of a non infected quarter. Drug manufacturer's instructions

regarding frequency, duration and level of treatment should be precisely followed. Udder balm may be applied on the udder to reduce inflammation. For anti bacterial treatment, the drug (usually an antibiotic) must reach the causative bacteria in the udder. Therefore, an intra-mammary treatment is by far the most common method for all forms of mastitis. The antibiotic must be administered into the teat of the affected quarter after it has been emptied of milk.

Antibiotic therapy

a)Parenteral administration-Severe mastitis is usually treated systemically, although intra-mammary therapy will often be used adjunctively.

b)Intra-mammary administration-This route is accepted as the route of choice in the treatment of subclinical, chronic or mild clinical mastitis and as prevention during dry clinical mastitis and as prevention during dry cow therapy. It permits delivery of the antibiotic directly intothe mammary gland.

Hygiene and management:

The infection easily spreads from one cow to the other during milking via contaminated milk, hands of the milker, and udder cloths (in case of milking machine). Infection may also occur

during the interval between milking. Possible routes are contaminated beddings, licking of teats and udder, contact of the udder with the tail and legs and files. Therefore strict

hygiene has to be maintained. Cows with a high cell count can be separated from healthy

cows with a low cell count. Disinfection of the entire teats immediately after milking in a safe and effective teat dip is perhaps the most important single measure a dairy farmers

can take to reduce new infections in a herd. Most commercially available teat dips will reduce new infections by atleast 50%.

Control and prevention

Cows suffering from mastitis may recover spontaneously, but usually drug therapy is required to maintain productivity. It is a good practice to empty the affected quarters as often as possible by stripping the concerned teats several times per day. Improved animal husbandry, hygiene and good management are the only practical methods of prevention and disease control. To prevent cows from damaging their teats barbed wires should be

removed from the premises.In conclusion the most effective measures to prevent

mastitis are:

— Maintaining a consistent high standard of management and hygiene before, during and after milking;

— Using a good milking technique or an adequately functioning milking machine;

— Use of teat-dip with a disinfectant on all cows after every milking;

— Treating all cows with evidence of clinical mastitis promptly;

— Applying the somatic cell count monthly to monitor the health status of the herd;

— Applying antibiotics to all cows after the last milking at the time they are dried off;

— Attending immediately to any minor injury to the teat or udder tissue;

— Culling of cows suffering from recurrent clinical mastitis.

— Providing adequate nutrition to preclude increased susceptibility to mastitis.

Conclusion

Mastitis not only reduces the productive capacity of the cows, it is also expensive to treat. Therefore, its prevention should be the prime concern of each farmer. Effective mastitis control strategies including prudent use of antibiotics, adequate strategies including prudent

use of antibiotics, adequate housing with proper sanitation and regular screening for early detection and treatment, follow up of chronic case, culling of older cows with repeated attacks, avoiding consecutive milking and susceptibility testing of the mastitis pathogens before treatment are recommended to alleviate the problem.