Contagious bovine pleuropneumonia (CBPP)
This is a highly fatal disease of cattle and of major economic importance in certain tropical countries. It also affects buffaloes, bison and reindeer.
Epidemiology: The disease is widespread in tropical regions. It causes serious economic losses in Africa, Asia and Australia. It still exists in China and is prevalent in tropical Africa. In India, the disease existed in districts of upper parts of Asom, but now it has been completely eradicated from our country (May 2007, OIE). Under natural conditions, the disease spreads through infected droplets excreted from the respiratory tract of affected animals. The recovered animals continue to harbor 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.
Etiology: The causative organism is Mycoplasma mycoides subsp. mycoides type SC (Mmm SC). The organism is pleomorphic and may pass through standard bacterial filters. The disease is generally confined to lungs and pleura.
Clinical symptoms: High temperature (about 1040F) along with dry cough is the main symptom. 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 edema occurs at the throat. A discharge of thick mucus appears at nose and mouth. In acute cases, death occurs within 1 – 3 weeks after the first clinical signs appear. In chronic cases, the disease may persist for 7 weeks. Sometimes only mild symptoms appear and these animals survive, but infection persists and animals continue to excrete the organism.
Postmortem lesions: The main lesions are found in lung, but characteristic lesion found on postmortem is varying degrees of hepatization of lobules separated from each other by thickened interlobular septa. The thorax contains several liters of blood- strained pleuritic fluid. The pleura shows edematous thickening with a layer of fibrin. Sometimes, a section of lung is necrosed and surrounded by fibrous tissue. In living animal, this encapsulated area (sequester) may burst under certain conditions and redistribute the organisms.
Diagnosis: Diagnosis is based on history of the case, symptoms and characteristic lesions. The confirmatory diagnosis is carried out by testing the serum samples of the suspected animals by using complement fixation test. The molecular techniques, viz. PCR, RE analysis and DNA probes are also helpful in diagnosis of the disease.
Control: Prevention and control of contagious bovine pleuropneumonia depends upon the diagnosis of infection, slaughter of diseased animals, prohibiting the movement of animals and protecting individual animal by vaccination. A live attenuated vaccine (T1- 44) is recommended by the OIE for vaccination of the cattle. Since the disease has been eradicated from India, there is no need of vaccination in animals.