Pasteurella
Pasteurella is also called Fowl Cholera. It can cause acute mortality without any previous symptoms. It is also associated with pneumonia. Infection occurs mainly through infected air droplets and infected drinking water but it can also enter through wounds. Samples should be taken for bacteriology and sensitivity to find what antibiotic therapy can be given.
Rodents and wild birds are often carriers and should be discouraged as much as possible. Sheep can be another vector.