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Aspergillosis is the name given to a wide variety of diseases caused by fungal infections from species of Aspergillus. Aspergillosis occurs in humans, birds and other animals.

Aspergillosis occurs in chronic or acute forms which are clinically very distinct. Most cases of acute aspergillosis occur in people with severely compromised immune systems, e.g. those undergoing bone marrow transplantation.[1] Chronic colonization or infection can cause complications in people with underlying respiratory illnesses, such as asthma,[2] cystic fibrosis,[3] sarcoidosis,[4] tuberculosis, or chronic obstructive pulmonary disease.[5] Most commonly, aspergillosis occurs in the form of chronic pulmonary aspergillosis (CPA), aspergilloma, or allergic bronchopulmonary aspergillosis (ABPA).[6] Some forms are intertwined; for example ABPA and simple aspergilloma can progress to CPA.

Other, noninvasive manifestations include fungal sinusitis (both allergic in nature and with established fungal balls), otomycosis (ear infection), keratitis (eye infection), and onychomycosis (nail infection). In most instances, these are less severe, and curable with effective antifungal treatment.

The most frequently identified pathogens are Aspergillus fumigatus and Aspergillus flavus, ubiquitous organisms capable of living under extensive environmental stress. Most people are thought to inhale thousands of Aspergillus spores daily but without effect due to an efficient immune response. Taken together, the major chronic, invasive, and allergic forms of aspergillosis account for around 600,000 deaths annually worldwide.[disputed ][4][7][8][9][10]

Risk factorsRisk factors

People who are immunocompromised — such as patients undergoing hematopoietic stem cell transplantation, immunocompromised — such as patients undergoing hematopoietic stem cell transplantation, chemotherapy for leukaemia, or AIDS — are at an increased risk for invasive aspergillosis infections. These people may have neutropenia or corticoid-induced immunosuppression as a result of medical treatments. Neutropenia is often caused by extremely cytotoxic medications such as cyclophosphamide. Cyclophosphamide interferes with cellular replication including that of white blood cells such as neutrophils. A decreased neutrophil count inhibits the ability of the body to mount immune responses against pathogens. Although tumor necrosis factor alpha (TNF-α) — a signaling molecule related to acute inflammation responses — is produced, the abnormally low number of neutrophils present in neutropenic patients leads to a depressed inflammatory response. If the underlying neutropenia is not fixed, rapid and uncontrolled hyphal growth of the invasive fungi will occur and result in negative health outcomes.[15]

Prevention

Prevention of aspergillosis involves a reduction of

Prevention of aspergillosis involves a reduction of mold exposure via environmental infection-control. Antifungal prophylaxis can be given to high-risk patients. Posaconazole is often given as prophylaxis in severely immunocompromised patients.[16]

Screening

A systematic review has evaluated the diagnostic accuracy of polymerase chain reaction (PCR) tests in people with defective immune systems from medical treatment such as chemotherapy.[17] Evidence suggests PCR tests have moderate diagnostic accuracy when used for screening for invasive aspergillosis in high risk groups.[17]

Treatment

The current medical treatments for aggressive invasive aspergillosis include voriconazole and liposomal amphotericin B in combination with surgical debridement.[18] For the less aggressive allergic bronchopulmonary aspergillosis, findings suggest the use of oral steroids for a prolonged period of time, preferably for 6–9 months in allergic aspergillosis of the lungs. Itraconazole is given with the steroids, as it is considered to have a "steroid-sparing" effect, causing the steroids to be more effective, allowing a lower dose.[19] Other drugs used, such as amphotericin B, caspofungin (in combination therapy only), flucytosine (in combination therapy only), or itraconazole,[20][21] are used to treat this fungal infection. However, a growing proportion of infections are resistant to the triazoles.[22] A. fumigatus, the most commonly infecting species, is intrinsically resistant to fluconazole.[23]

EpidemiologyAspergillosis is thought to affect more than 14 million people worldwide,[24] with allergic bronchopulmonary aspergillosis (ABPA, >4 million), severe asthma with fungal sensitization (>6.5 million), and chronic pulmonary aspergillosis (CPA, ∼3 million) being considerably more prevalent than invasive aspergillosis (IA, >300,000). Other common conditions include Aspergillus bronchitis, Aspergillus rhinosinusitis (many millions), otitis externa, and Aspergillus onychomycosis (10 million).[25][26] Alterations in the composition and function of the lung microbiome and mycobiome have been associated with an increasing number of chronic pulmonary diseases such as COPD, cystic fibrosis, chronic rhinosinusitis and asthma.[27]

Animals

While relati

While relatively rare in humans, aspergillosis is a common and dangerous infection in birds, particularly in pet parrots. Mallards and other ducks are particularly susceptible, as they often resort to poor food sources during bad weather. Captive raptors, such as falcons and hawks, are susceptible to this disease if they are kept in poor conditions and especially if they are fed pigeons, which are often carriers of "asper". It can be acute in chicks, but chronic in mature birds.

In the United States, aspergillosis has been the culprit in several rapid die-offs among waterfowl. From 8 December until 14 December 2006, over 2,000 mallards died near Burley, Idaho, an agricultural community about 150 miles southeast of <

In the United States, aspergillosis has been the culprit in several rapid die-offs among waterfowl. From 8 December until 14 December 2006, over 2,000 mallards died near Burley, Idaho, an agricultural community about 150 miles southeast of Boise. Mouldy waste grain from the farmland and feedlots in the area is the suspected source. A similar aspergillosis outbreak caused by mouldy grain killed 500 mallards in Iowa in 2005.

While no connection has been found between aspergillosis and the H5N1 strain of avian influenza (commonly called "bird flu"), rapid die-offs caused by aspergillosis can spark fears of bird flu outbreaks. Laboratory analysis is the only way to distinguish bird flu from aspergillosis.

In dogs, aspergillosis is an uncommon disease typically affecting only the nasal passages (nasal aspergillosis). This is much more common in dolicocephalic breeds. It can also spread to the rest of the body; this is termed disseminated aspergillosis and is rare, usually affecting individuals with underlying immune disorders.

In 2019, an outbreak of aspergillosis struck the rare kakapo, a large flightless parrot endemic to New Zealand. By June the disease had killed seven of the birds, whose total population at the time was only 142 adults and 72 chicks. One fifth of the population was infected with the disease and the entire species was considered at risk of extinction.[28]