Airsacculitis

Airsacculitis is a lower respiratory-associated disease in chickens, and is defined as inflammation of one or more of the air sacs. Air sacs serve as an integral part of a chicken's respiratory system. Chickens have nine air sacs, which are thin-walled bubble-like pockets that work as a system to circulate oxygen throughout their bodies. There are four paired air sacs (cervical, cranial and caudal thoracic, and abdominal) and one unpaired air sac (clavicular).

When a chicken's air sacs become inflammed, it causes them to thicken and accumulate purulent, or caseous material within the air sac cavity. This is usually caused by a bacterial or fungal infection, and less commonly a virus. Some of the most common pathogens isolated from chickens with airsacculitis include Escherichia coli and Mycoplasma gallisepticum. Specific diseases associated with onset of airsacculitis include:

• Avian chlamydiosis: Avian chlamydiosis (AC) is a zoonotic respiratory disease of chickens caused by gram-negative bacteria from the Chlamydia genus. The genus consists of 11 different species from the Chlamydiaceae family. Chickens are predominately affected by C. psittaci, C. gallinacea and C. suis. Clinical signs vary depending on the virulence of the chlamydial strain and immune status of the bird. The most frequently reported signs in chickens include nasal and ocular discharges, difficulty breathing, diarrhea, weight loss, reduced egg production in hens, hyperthermia, lethargy and dullness.
• Newcastle disease (ND): Newcastle disease is a highly contagious viral infection of domestic and wild birds worldwide. Since wild birds can sometimes carry the virus, outbreaks can occur anywhere poultry is raised. ND is caused by Newcastle disease virus (NDV), also known as Avian paramyxovirus-1 (APMV-1). The severity of ND varies widely and is dependent on factors such as: the strain of the virus, the age of the chicken (young chicks are more susceptible), concurrent infection with other organisms, stress and immune status. Some virus strains attack the nervous system, others the respiratory, or digestive systems.
• Chronic respiratory disease (CRD): Chronic respiratory disease (CRD), also known collectively as mycoplasma gallisepticum (MG) infection, is considered to be one of the major pathogens that cause respiratory disease in poultry. It tends to develop slowly in flocks and associated with progressive and chronic respiratory signs. Chickens with chronic respiratory disease often show clinical signs associated with the respiratory system, which include tracheitis, sinusitis, airsacculitis and conjunctivitis.
• Aspergillosis: Aspergillosis is a common fungal disease of chickens caused by infection with the genus Aspergillus, which consists of approximately 600 different species. A. fumigatus is the most common species isolated from infected chickens. Aspergillosis manifests as two different forms in chickens. Acute aspergillosis, also referred to as brooder pneumonia is characterized by severe outbreaks in newly hatched chicks and is associated with high morbidity and high mortality rates. Chronic aspergillosis usually occurs in adult birds living in poorly ventilated, dusty or moldy environments.
• Ornithobacteriosis: Ornithobacteriosis is an emerging, acute and highly contagious disease of chickens, caused by Ornithobacterium rhinotracheale bacterium. It causes respiratory disease in chickens and turkeys worldwide. O. rhinotracheale is a rod-shaped, gram-negative, bacterium with several serotypes. The disease often presents as pneumonia or airsacculitis in affected flocks.