Archive | 2019
Infectious Diseases in Dairy Cattle
Abstract
Abstract Among the infectious diseases of the dairy herd, mastitis is the main cause of direct and indirect economic losses. Mastitis etiological agents are usually bacteria, but fungi and algae may be involved. Staphylococcus aureus is commonly isolated from mastitis and deserves special attention due to the numerous hospital infections related to methicillin resistant strains. Although the mammary gland presents different defense mechanisms, in many cases the etiologic agent can escape of the immune system and multiply, resulting in mastitis. Several nonspecific antimicrobial factors are found in the mammary gland, such as lactoperoxidase–thiocyanate¬–hydrogen peroxide, lysozyme, lactoferrin, and complement system. Adaptive or acquired immunity can lead to an immediate response in repetitive exposure to the same microorganism. Two types of adaptive responses are described: humoral and cellular immunities. Conventional diagnostic methods are widely considered for mastitis detection, like microbiological isolation and somatic cell count; however, alternative diagnosis methods are being increasingly used, like infrared thermography that measures the surface temperature of mammary gland skin and sphincters of the teats. Conventional therapy based on antibiotics is not always efficient, resulting in cases of persistent infections. Recent research using inhibitors of multidrug efflux systems and biofilms has been tested in vitro with reliable results. Studies have also demonstrated that bioactive substances extracted from plants with and without chemical modifications have shown synergistic associations with the traditional antimicrobials against bacteria causing mastitis. Other infectious diseases, such as brucellosis, tuberculosis, Johne s disease, leptospirosis, Salmonellosis, bovine viral diarrhea (BVD), and infectious bovine rhinotracheitis (IBR) can affect the dairy cattle herd, compromising the milk production chain in economic, social, and public health aspects.