P. multocida are nonmotile, small, coccoid, or rod-shaped bacillus that often exhibit bipolar staining (Campbell et al., 1999).

P. multocida are inhabitants of the upper respiratory tract of a wide range of vertebrate host species (i.e. chickens, turkeys, cattle, swine, cats, dogs, rabbits). The host species are considered the primary reservoir for these bacteria and their presence in the external environment is thought to be transitory in nature.

According to Campbell et al. (1999), bacteria reproduce asexually using binary fission. Binary fission is a type of cellular division in which each dividing daughter cell receives a copy of the single parent chromosome.

Campbell et al. (1999) write that in order to grow in nature or in the laboratory, a bacterium must have an energy source, a source of carbon, other required nutrients, and a permissive range of physical conditions such as oxygen concentration, temperature, and pH.

Mensik and Samuel (2002) observed that avian cholera often affects the same wetlands and bird populations each year. Outbreaks of the disease also tend to follow the migration routes of some species, most notably snow geese. These disease patterns have caused wildlife biologists to hypothesize that bacteria either live year round in affected wetlands or are transmitted by carrier birds.

This species is an important cause of disease in wild and domesticated animals. According to Mensik and Samuel (2002), during cholera outbreaks in waterfowl, owls, hawks and eagles may become infected after feeding on diseased carcasses. Clinical signs of fowl cholera following infection may be manifested peracutely or acutely, with previously healthy birds suddenly being found dead or profoundly ill. This bacterium kills swiftly, sometimes in as few as six to twelve hours after infection. Before death, the birds may exhibit convulsions, uncoordinated fluttering, stiffness and rapid breathing. Birds that do not die acutely may show signs of listlessness, shivering and huddling. Respiratory sound, sneezing and sticky nasal discharges are sometimes observed. The feathers surrounding the vent, eyes and beak may become matted with secretion. The droppings, which may start out as pasty and yellow, may become bloodstained due to intestinal ulceration. Birds chronically affected with fowl cholera show weight loss, abdominal distention, lameness, and joint enlargement. Live bacteria released into the environment by dead and dying birds can subsequently infect healthy birds, and as a result, avian cholera can spread quickly through a wetland and kill thousands of birds in a single outbreak.

Preventative measures: Since infections caused by P. multocida are usually secondary to overcrowding and other stresses that reduce the overall health of the animals, measures to limit overcrowding and exposure to other stressors would reduce the risk of infection.

\r\nPhysical: In the face of an outbreak, control is directed at attempts to limit transmission of the disease. In outbreaks of avian cholera in waterfowl it is recommended that all carcasses are collected and burned. Dead birds floating on the water not only serve as a source of contamination but also act as decoys to lure more waterfowl into infectious water. Contaminated pools can be drained and then cultivated or flushed by flooding with pumped or floodwaters. In severe outbreaks, it is occasionally recommended that attempts be made to limit the scavenging activities of gulls, which are resistant and can act as transmitters of fowl cholera.