Contagious bovine pleuropneumonia (CBPP)
This is a highly infectious disease and is of major economic importance in certain tropical countries. The causative organism is Mycoplasma mycoides subsp. mycoides Type SC. The organism being very pleomorphic may pass through standard bacterial filters. The disease is specific for cattle confined to lungs and pleura. Rarely the disease affects buffaloes, bison and reindeer. India has been recently declared free of this disease.
Transmission: Under natural conditions the disease spreads through infected droplets excreted from the respiratory tract or urine from diseased animals. The recovered animals continue to harbour the organism and remain as a source of infection up to 18 months. The incubation period varies from 1 to 4 months. Cattle of all ages suffer from the disease.
Symptoms: The symptoms are high temperature (about 40°C) with dry cough. Later,the cough becomes more severe and animals show signs of pain. The temperature declines before death due to asphyxia. The course of disease is 2-6 weeks. Pregnant animals abort during acute phase of illness. Sometimes oedema occur at the throat. A discharge of thick mucus appears at nose and mouth. In acute cases death occurs 1-3 weeks after the first clinical signs appear. In chronic cases the disease may persist for seven weeks. Sometimes only mild symptoms appear and these animals survive, but infection persists and animals continue to excrete the organism.
Lesions: The lung lesions are characteristic; normally only one lung is affected. The characteristic lesion found on post-mortem is varying degrees of hepatization of lobules separated from each other by thickened interlobular septa. The thorax contains several litres of blood-stained pleuritic fluid. The pleura shows oedematous thickening with a layer of fibrin. Sometimes a section of lung is necrosed and surrounded by fibrous tissue. In living animal this encapsulated area may break down under certain conditions and redistribute the organisms.
Diagnosis: Diagnosis is based on history of the case, symptoms and characteristic lesions. If the characteristic lesions are seen laboratory examination together with complement fixation testing of blood sera of in-contact animals should be carried out.
Control: Control and prevention of contagious bovine pleuropneumonia depend upon the diagnosis of infection, slaughter of diseased animals, prohibiting the movement of animals and protecting individual animals by vaccination. A live attenuated strain is used by inoculating intradermally in the ear-tip. The immunity lasts for about 18 months. M. bovigenitalium causes bovine mastitis and is associated with vulvovaginitis and infertility. The infection of udder causes swollen udder, sudden decrease in milk and a rise of temperature.