Review on Epidemiology of Clinical and Subclinical Mastitis on Dairy Cows

Abstract

Mastitis is a complex and multi-factorial disease, the occurrence of which depends on variables related to the animal, environment and pathogen. It reduces the quality and quantity of milk, and is one of the most important and expensive disease of dairy industry. Among the pathogens, bacterial agent are the most common one, the greatest share of which resides widely distributed in the environment of dairy cows, hence a common threat to the mammary gland. Mastitis is very common in cows of both developed and developing countries. Based on clinical symptoms, it can be classified into two types, namely, clinical and subclinical mastitis. Clinical mastitis is often diagnosed directly by visual assessment of udder inflammation or by changes in milk’s organoleptic properties whereas, Subclinical mastitis is non observable form of mastitis, which is with no visible abnormalities of either the milk or the udder and is characterized by sudden rise in milk somatic cell count. Mastitis pathogens can be divided into contagious and environmental. The primary reservoir of con­tagious pathogens is an infected udder whereas a contaminated environment is the primary reser­voir of pathogens causing environmental mastitis. As in the rest part of the world, mastitis is one of the most economically important disease of dairy sector and is an important factor that limits dairy production in Ethiopia, giving emphasis only to clinical mastitis and subclinical mastitis, (with prevalence of 23% to 85%) is with little attention, causing heavy financial loses and public health hazards. Early diagnosis of mastitis is vital because changes in the udder tissue take place much earlier before they become apparent. Many factors influence the incidence of mastitis, such as Age, parity and lactation stage of a cow, lactation number, herd management, husbandry environment, temperature, humidity, seasons, breeds, and milking characteristics, and nature of the pathogen. If detected early, antibiotic therapy is very effective in curing and controlling the spread of contagious pathogens. However, The use of antimicrobials have, over time, increased the number of antimicrobial-resistant microbes globally, and any use of these agents will to some extent benefit the development of resistant strains and also inappropriate usage of antimicrobials such as wrong dose, drug or duration may contribute the most to the increase in antimicrobial resistance without improving the outcome of treatment.

Keywords: Mastitis, Ethiopia, dairy cows, antibiotic