Airsacculitis, also known as air sacculitis, aerosacculitis, air sac disease, air sac infection, air sac syndrome and simply sac disease, is a common inflammatory condition of

air sacs Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase in the pneumatization (presence ...

that occurs in

birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

and is caused by various

microbial A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

(mostly

bacterial Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

) taxa. Having multiple different causative agents, the condition is widely distributed around the world. Since the disease is highly

infectious An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...

it is especially dangerous for domesticated birds (

poultry Poultry () are domesticated birds kept by humans for their eggs, their meat or their feathers. These birds are most typically members of the superorder Galloanserae (fowl), especially the order Galliformes (which includes chickens, quails, a ...

) bred on big farms. Occurrence of airsacculitis in big flocks can mean high economic loss, as infected poultry needs to be carefully observed, with all of the infected tissue disposed of and not used for human food. In severe cases of the disease whole infected bird carcasses need to be disposed.Compliance Guideline for Training Establishment Carcass Sorters in the New Poultry Inspection System (NPIS)
Food Safety and Inspection Service U.S. Department of Agriculture (September 2014). Retrieved 19. September 2021. Usually the disease affects younger birds, aged between 6 and 12 weeks. The most characteristic sign of airsacculitis is an inflamed

mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

of bird air sacs, which swells and becomes red, with infected birds exhibiting different symptoms, such as coughing,

lethargy Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overwo ...

, swelling of the neck, difficult breathing, appetite and weight loss etc. The same term is used for

bacterial infection Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases. The number of ...

and subsequent inflammation of laryngeal air sacs in

non-human primates Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...

In birds

Anatomical background

The respiratory system of birds differs significantly from that found in

mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

. Birds have relatively small

lungs The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of th ...

that are rigid and not contractile like those of

, in which lungs expand and contract during the breathing cycle. Another critical difference is the absence of so-called

in mammals. Such structures help birds to regulate air flow through their respiratory system. Birds also lack the

diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...

Cranial sinus and postcranial air sac systems in birds

Signs and symptoms

Airsacculitis is an inflammatory condition, that appears as a consequence of infection with various species of

microbes A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

, mostly bacteria. The condition itself resembles mammal

bronchitis Bronchitis is inflammation of the bronchi (large and medium-sized airways) in the lungs that causes coughing. Bronchitis usually begins as an infection in the nose, ears, throat, or sinuses. The infection then makes its way down to the bronchi. ...

and

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...

, even though different body parts are infected and inflamed. In a few cases the condition is

asymptomatic In medicine, any disease is classified asymptomatic if a patient tests as carrier for a disease or infection but experiences no symptoms. Whenever a medical condition fails to show noticeable symptoms after a diagnosis it might be considered asy ...

. Infected birds usually appear sick; lower part of their neck can swell and animals experience difficulties breathing. They may cough, lose their appetite and subsequently their weight, often exhibit nasal discharge, apparent clogged nares, ruffled feathers, have watery eyes and appear

lethargic Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overwo ...

. Affected adult females (hens) lay fewer eggs, while juveniles exhibit stunted growth. When doing an

autopsy An autopsy (post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination of a corpse by dissection to determine the cause, mode, and manner of death or to evaluate any di ...

congestion of air sacs, throat and nares is evident. Air sacs are red, swollen and produce a lot of liquid.

Cause

The cause of airsacculitis is a

of air sacs. The common disease causative agents are species, such as pathogenic ''Escherichia coli'', ''

Mycoplasma gallisepticum ''Mycoplasma gallisepticum'' (MG) is a bacterium belonging to the class Mollicutes and the family Mycoplasmataceae. It is the causative agent of chronic respiratory disease (CRD) in chickens and infectious sinusitis in turkeys, chickens, game bi ...

'' (MG)'', Mycoplasma synoviae'' (MS), '' Mycoplasma meleagridis'' (MM), ''

Ornithobacterium rhinotracheale ''Ornithobacterium rhinotracheale'', or ORT, is a bacteria, bacterium that causes Respiration (physiology), respiratory disease in poultry. It can cause disease in birds of all ages and is potentially fatal. ''O. rhinotracheale'' is found worldw ...

'' (ORT) and '' Bordetella avium''. Airsacculitis can also be caused by other microbes, such as

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

and in rare cases even

viruses A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

. Only rarely airsacculitis is a consequence of improper

vaccine A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifie ...

or its administration. This disease is highly infectious in birds, but the

infectivity In epidemiology, infectivity is the ability of a pathogen to establish an infection. More specifically, infectivity is a pathogen's capacity for horizontal transmission — that is, how frequently it spreads among hosts that are not in a parent� ...

is dependant on the causative agent itself. Specific bacteria species (particularly ''E. coli''), causing the airsacculitis in birds, can be transmitted to people. In some cases this disease can be latent, meaning bacteria remain dormant in survivors and potentially attack non-infected birds after a while.

Diagnosis and treatment

Typical symptoms should be observed. The disease can be diagnosed with a help of

radiography Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...

and

endoscopy An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are insert ...

. After a close inspection (eg. an air sac

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a diseas ...

) veterinarians usually prescribe

antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention o ...

for the exact infectious agent. It is also important to diagnose any additional (

comorbid In medicine, comorbidity - from Latin morbus ("sickness"), co ("together"), -ity (as if - several sicknesses together) - is the presence of one or more additional conditions often co-occurring (that is, concomitant or concurrent) with a primary c ...

) diseases.

Abscess An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends b ...

and

granuloma A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectious ...

can be removed surgically. To prevent the disease poultry should be kept in dry and warm (not chilled or over-heated) conditions, with appropriate sanitation, source of clean water and an access to enough fresh air (ventilation).

Prognosis

Prognosis is usually favorable, with poultry experiencing moderate pain for some time.Forbes NA & Altman RB (1998) Self-Assessment Colour Review Avian Medicine ''Manson Publishing Ltd''Stanford, M (2009) Respiratory Disease in Birds Royal Veterinary College Integrated Course ''RVC'' It has been reported that commonly about 2/3 of infected birds recover after exhibiting symptoms for some time. Prompt care increases the likelihood of survival. In specific birds unwanted

feather-plucking Feather-plucking, sometimes termed feather-picking, feather damaging behaviour or pterotillomania, is a maladaptive, behavioural disorder commonly seen in captive birds that chew, bite or pluck their own feathers with their beak, resulting in da ...

can occur as a consequence of infection and inflammation.

Differential diagnosis

Some other diseases that affect bird's respiratory system and have similar signs are

rhinitis Rhinitis, also known as coryza, is irritation and inflammation of the mucous membrane inside the nose. Common symptoms are a stuffy nose, runny nose, sneezing, and post-nasal drip. The inflammation is caused by viruses, bacteria, irritants o ...

(coryza), avian infectious bronchitis (IB), infection of

trachea The trachea, also known as the windpipe, is a Cartilage, cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends ...

with a gapeworm and chronic respiratory disease (CRD). Among other diseases associated with the onset of airsacculitis are also avian chlamydiosis (AC),

newcastle disease Virulent Newcastle disease (VND), formerly exotic Newcastle disease, is a contagious viral avian disease affecting many domestic and wild bird species; it is transmissible to humans. Though it can infect humans, most cases are non-symptomatic; ...

(ND),

aspergillosis Aspergillosis is a fungal infection of usually the lungs, caused by the genus ''Aspergillus'', a common mould that is breathed in frequently from the air around, but does not usually affect most people. It generally occurs in people with lung dise ...

and ornithobacteriosis.

In primates

Disease and pathology

Sometimes, the term airsacculitis is used for bacterial infection of the laryngeal air sacs in

, the most commonly

primates Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...

. Such airsacculitis in non-human primates often leads to various chronic respiratory diseases. The infected air sacs thicken. Under the microscope one can detect

hyperplasia Hyperplasia (from ancient Greek ὑπέρ ''huper'' 'over' + πλάσις ''plasis'' 'formation'), or hypergenesis, is an enlargement of an organ or tissue caused by an increase in the amount of organic tissue that results from cell proliferati ...

hypertrophy Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It is distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number.Updated by Linda J ...

epithelium Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...

, cell

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

fibrosis Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perma ...

, cellular infiltrates, as well as an occurrence of bacterial colonies. Among typical symptoms of the disease are

halitosis Bad breath, also known as halitosis, is a symptom in which a noticeably unpleasant breath odour is present. It can result in anxiety among those affected. It is also associated with depression and symptoms of obsessive compulsive disorder. Th ...

(bad breath), coughing,

rhinorrhea Rhinorrhea, rhinorrhoea, or informally runny nose is the free discharge of a thin mucus fluid from the nose; it is a common condition. It is a common symptom of allergies ( hay fever) or certain viral infections, such as the common cold or COVID- ...

(nasal discharge), depression,

anorexia Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. ''Anorexia'' is a term of Gre ...

and

weight loss Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat (adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other conn ...

Anatomy and function

It is critically important to note, that laryngeal air sac is not a synonym of

pulmonary alveolus A pulmonary alveolus (plural: alveoli, from Latin ''alveolus'', "little cavity"), also known as an air sac or air space, is one of millions of hollow, distensible cup-shaped cavities in the lungs where oxygen is exchanged for carbon dioxide. Al ...

(sometimes also called an air sac), which represents the end of the

bronchiole The bronchioles or bronchioli (pronounced ''bron-kee-oh-lee'') are the smaller branches of the bronchial airways in the lower respiratory tract. They include the terminal bronchioles, and finally the respiratory bronchioles that mark the start o ...

and serves as an exchanging agent of gases between

and

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...

. Infected lungs and inflamed lung tissue (with alveoli) is a sign of

and not airsacculitis. In primates laryngeal air sacs occur in

apes Apes (collectively Hominoidea ) are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and as well as Europe in prehistory), which together with its sister g ...

and

gibbons Gibbons may refer to: * The plural of gibbon, an ape in the family Hylobatidae * Gibbons (surname) * Gibbons, Alberta * Gibbons (automobile), a British light car of the 1920s * Gibbons P.C., a leading American law firm headquartered in New Jersey ...

, while such structures are absent in

people A person (plural, : people) is a being that has certain capacities or attributes such as reason, morality, consciousness or self-consciousness, and being a part of a culturally established form of social relations such as kinship, ownership of pr ...

and some smaller gibbon species. These air sacs are useful when producing fast and extended call sequences. Such behaviour often leads to the risk of

hyperventilation Hyperventilation is irregular breathing that occurs when the rate or tidal volume of breathing eliminates more carbon dioxide than the body can produce. This leads to hypocapnia, a reduced concentration of carbon dioxide dissolved in the blood. ...

if there are no air sacs to allow re-breathing of an exhaled air. Researchers proposed the absence of laryngeal air sacs in humans is a result of people's ability to adjust their speech breathing patterns and consequently lower probability of hyperventilation. It is thought that the lack of laryngeal air sacs in humans represents a derived feature.

References

{{Reflist, 3 Poultry diseases Animal bacterial diseases Animal viral diseases Animal fungal diseases Bird diseases