Mastitis, Biology


Mastitis is one the important diseases in cows that has serious economic impact on livestock production. The inflammation of mammary gland is associated with physical, chemical or bacteriological changes in the milk of farm/ lactating animals.

Etiology: Large number of infectious agents is responsible in causing the disease in dairy animals. Bacterial agents like Streptococcus, Staphylococcus, Escherichia, Campylobacter, Corynebacterium, Klebsiella, Mycobacterium, Bacillus, Pasteurella and Pseudomonas species, and mycoplasma and fungal agents like Trichophyton, Aspergillus, Candida and Cryptococcus species are associated with mastitis (details are given in chapter....)

Pathogenesis: The organisms pass through teat canal, localize in the alveoli and develop inflam­mation. From the outer surface of teat or from the environment, the organisms penetrate in to the teat canal and multiply there. When the number of causal agents is increased, they reach into mammary tissue to start inflammatory reaction. Due to this inflammatory reaction, changes are noticed in the milk as well as udder. (details are given in chapter....)

Clinical signs: Acute mastitis is associated with severe inflammatory reaction and significant alteration in milk quality. The udder shows diffuse swelling which is hot and painful. Milk from affected quarter contains large number of clots or flakes and its colour gets changed. Sometimes systemic reaction characterized by high rise of body temperature, ruminal stasis, depression, anorexia and toxaemia are observed. In severe cases, blood mixed milk comes out of the teat. Fibrosis and atrophy of the quarter develops in subacute or chronic form of mastitis. The affected quarter becomes almost dead with no milk present. On repeated attempts, a little amount of milk flakes may come out or the secretion becomes watery.

Diagnosis: It is diagnosed by clinical symptoms and palpation of udder. However, subclinical cases are difficult to diagnose clinically as there will be no apparent signs of mastitis except gradual loss in milk production. Milk of suspected animal can be examined by number of tests to detect abnormality. The milk should be collected in strip cup as it helps in detecting the discolouration of milk, presence of pus, clot, flake or any other abnormality. During inflammatory reaction, there is increase in leukocyte count in the milk. Leukocytes can be counted directly in the milk or can be known by indirect tests like California mastitis test (CMT) or White side test. These are based on cell count as well as chloride content. Subclinical mastitis can also be diagnosed by bromothymol blue (BTB) test. The strips for such test are available and are dipped in milk sample. In positive cases, strip colour changes on dipping in the milk. This test is more useful in diagnosing subclinical form of the disease. In the affected milk samples, there is change in electrical conductivity (EC) which can be measured by conductivity meter. If the leukocyte count is up to 0.3 million, it is considered as negative sample while count above 0.5 million is indicative of positive case.

The milk samples with leukocyte count above 0.5 million should be cultured for bacteriological isolation. The bacterial count is also quite high in mastitis. In normal milk samples, count is less then 1,000/ml which increases to 10,000/ml in subclinical and over 10 million in clinical cases. Measurement of lactose content or estimation of N-acetyl-(3)-D-glucosaminidase and lactate dehydrogenase enzymatic activity also helps in diagnosis. The activity of these enzymes is increased in mastitis due to high leukocyte counts.

Treatment: A large number of intramammary infusions are available and new preparations are continuously added. Main reason of drug resistance is the indiscriminate use of antibiotics. Therefore, it is desirable to perform drug sensitivity of the causal organisms for effective treatment. Antibiotics should be selected on the basis of its activity against infective agent, diffusion in mammary gland and cost. Intramammary infusions available presently contain ampicillin, cloxacillin, penicillin G, tetracyclines, neomycin, nitrofurazones, etc. Some of these intramammary infusions contain prednisolone and hydrocortisone. In emergency cases, broad spectrum antibiotics like cephalosporins or combination of penicillin G with other drugs should be infused till we get the laboratory reports. If fibrosis has developed in udder, use of fibrinolytic agents along with antibiotics is of some value. The best line of treatment for mastitis is the use of antibiotics by parenteral route and infusion of intramammary preparations. Usually, treatment is continued for 4 to 7 days. As a supportive therapy, use of analgesics and antihistaminic is advised for early recovery. The milk from treated quarter should not be consumed at least for 72 h after last treatment as it contains residues of antibiotics.

Dry cow therapy is practiced to prevent the occurrence of disease and when the disease is very much re-occurring and chronic. Anti-bacterial intra-mammary infusions are given in all the teats after drying of the animals. Usually, ampicillin and cloxacillin combinations are used for dry herd therapy. However, some preparations are specifically meant for this purpose, and it is better to use such drugs. Milk from such animal should not be used for 4 days after calving.

Control: It is difficult to control the disease as it is caused by a number of causal organisms. However, use of strict hygienic conditions, proper washing of udder and teats before and after milking with 0.2% quaternary ammonium compound solution or iodophors solution (100 ppm available iodine), adoption of correct milking techniques avoiding injury to teats, and dry cow therapy are of greater importance in reducing the occurrence of disease.

Posted Date: 9/19/2012 1:39:29 AM | Location : United States

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