Fowl cholera
Fowl cholera, a highly contagious disease of poultry caused by Pasteurella multocida, was one of the first infectious diseases to be recognized by Louis Pasteur in 1880. The infection can range from acute septicemia to chronic and localized infection and in acute cases, very high morbidity and mortality that may reach up to
100%. Predisposing factors include high density and concurrent infections such as respiratory viruses. The disease is transmitted via oral or nasal route. The bacterium is susceptible to environmental factors and disinfectants, but may persist for prolonged periods in soil. Reservoirs of infection may be present in other species such as rodents, cats and possibly pigs.
P. multocida is non motile Gram-negative coccobacillus. Capsule is seen in freshly isolated culture. It can grow both aerobically and anaerobically. The bipolar nature of the bacteria is the characteristic feature on staining with methylene blue or Leishman' stain and is helpful in easy identification.
Symptoms and lesions: Ruffled feathers, loss of appetite, coughing, nasal, ocular and oral discharge, swollen and cyanotic wattles and face are the common signs. In some cases, diarrhoea, swollen joints, lameness may also be seen. Sometimes PM changes are not seen or limited to hemorrhages at few sites but generally focal hepatitis, consolidation of lungs, suppurative pneumonia (especially in turkeys), cellulitis of face and wattles, purulent arthritis or enteritis are noted.
Diagnosis: Typical bipolar stained, dumbbell-shaped organisms are seen in blood smears/ impression smears. Isolation can be easily done by aerobic culture on blood agar and further confirmed with biochemical tests.
Prevention and control: Biosecurity, rodent control, hygiene and healthy diet are enough to prevent the disease. This is mostly opportunistic infection; special care is to be taken during stress or other respiratory viral infections.