how to prevent aspergillosis in birds

1Programa de Pós-Graduação em Microbiologia e Parasitologia, Instituto de Biologia, Universidade Federal de Pelotas, Pelotas 96160-000, Brazil; moc.liamg@grufreivaxassilem

2Reference Unit for Parasitic and Fungal Infections, Department of Infectious Diseases, National Institute of Health, Dr. Ricardo Jorge, 1649-016 Lisbon, Portugal; tp.eduas-nim.asni@omissirev.anitsirc (C.V.); tp.eduas-nim.asni@onibas.leuqar (R.S.)Find articles by

3Division of Infectious Diseases and Geographic Medicine, Stanford University Medical School, Stanford, CA 94305, USA; ude.drofnats@snevets

5Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA; ude.sivadcu@lletalFind articles by

2Reference Unit for Parasitic and Fungal Infections, Department of Infectious Diseases, National Institute of Health, Dr. Ricardo Jorge, 1649-016 Lisbon, Portugal; tp.eduas-nim.asni@omissirev.anitsirc (C.V.); tp.eduas-nim.asni@onibas.leuqar (R.S.)Find articles by

2Reference Unit for Parasitic and Fungal Infections, Department of Infectious Diseases, National Institute of Health, Dr. Ricardo Jorge, 1649-016 Lisbon, Portugal; tp.eduas-nim.asni@omissirev.anitsirc (C.V.); tp.eduas-nim.asni@onibas.leuqar (R.S.)

1Programa de Pós-Graduação em Microbiologia e Parasitologia, Instituto de Biologia, Universidade Federal de Pelotas, Pelotas 96160-000, Brazil; moc.liamg@grufreivaxassilem

7Programa de Pós-Graduação em Ciências da Saúde, Faculdade de Medicina, Universidade Federal do Rio Grande, Rio Grande 96203-900, BrazilFind articles by

The One Health context considers health based on three pillars: humans, animals, and environment. This approach is a strong ally in the surveillance of infectious diseases and in the development of prevention strategies. Aspergillus spp. are fungi that fit substantially in this context, in view of their ubiquity, as well as their importance as plant pathogens, and potentially fatal pathogens for, particularly, humans and avian species. In addition, the emergence of azole resistance, mainly in Aspergillus fumigatus sensu stricto, and the proven role of fungicides widely used on crops, reinforces the need for a multidisciplinary approach to this problem. Avian species are involved in short and long distance travel between different types of landscapes, such as agricultural fields, natural environments and urban environments. Thus, birds can play an important role in the dispersion of Aspergillus, and of special concern, azole-resistant strains. In addition, some bird species are particularly susceptible to aspergillosis. Therefore, avian aspergillosis could be considered as an environmental health indicator. In this review, aspergillosis in humans and birds will be discussed, with focus on the presence of Aspergillus in the environment. We will relate these issues with the emergence of azole resistance on Aspergillus. These topics will be therefore considered and reviewed from the “One Health” perspective.

Aspergillosis is a fungal disease caused by Aspergillus, which can affect humans, dogs, cats, horses, marine mammals, wild and domestic birds and even invertebrates, such as bees and corals [1]. The common route of infection for vertebrates is inhalation of conidia present in the environment and the respiratory tract is the most common anatomical site for initial site of infection ( ) [1,2]. To date, aspergillosis is considered a non-contagious disease, however recent studies have raised the possibility of transmission of this fungus among hospitalized patients [3,4]. In this sense, due to its clinical manifestation in avian species [5,6], the hypothesis of fungal transmission among captive birds, as in the case of aviaries, wildlife rehabilitation centers and zoological institutions must be raised. This transmission may occur especially through environmental (particularly air) contamination by sick birds.

Azoles such as itraconazole (ITC), voriconazole (VRC), posaconazole (POS) and isavuconazole (ISA) are the drugs of choice for prophylaxis and treatment of aspergillosis both in humans and animals [7,8,9,10,11,12]. Because of the difficulty on designing antifungal drugs that lack side effects in humans, effective therapeutic options to treat mycoses presently are limited [13]. Concurrently, triazoles are the main pesticides used in agriculture [14,15]. Thus, a concern about worldwide azole resistance arises from the large use of agricultural fungicides in the environment, leading to emerging resistant Aspergillus strains, and hence contributing to an increase of treatment failure rate in humans.

In this review, we will discuss relevant microbiologic aspects of these fungi, and of its infection, aspergillosis, in humans and birds. Aspects concerning Aspergillus in the environment, and the emergence of antifungal resistance of this pathogen will also be approached. We highlight these topics from a One Health perspective, where humans, animals and environment are all connected.

Aspergillus is a ubiquitous saprophytic genus, with worldwide distribution. It is frequently found in decomposing plants, playing an important role in this process and contributing to carbon and nitrogen recycling [16]. Fungi of this genus are widely used in industry owing to their high capability to produce a diversity of enzymes, such as amylases; in generating chemical additives, such as citric acid; the production of soy sauces; and in bioremediation processes, among others [17].

The taxonomy of Aspergillus is in flux, and four to eight subgenera, and from 16 to 25 sections, has been proposed by different authors, and more than 350 species. Most species are found in the environment, without reported clinical relevance thus far [18,19,20,21]. Sections Flavi, Nigri, Nidulantes, Terrei and Fumigati are of interest in clinical practice.

Species belonging to section Fumigati are the main etiologic agents of aspergillosis. Aspergillus fumigatus sensu stricto is the cause of the majority of those infections. However, it is estimated that between 3 to 6% of those infections are caused by cryptic species. A. lentulus, A. udagawae, A. viridinutans, A. thermomutatus, A. novofumigatus and A. hiratsukae are the most common cryptic species reported in medical practice to date. When compared to A. fumigatus sensu stricto, these cryptic species seem to have limited pathogenicity, since they have limited thermotolerance and have slower rates of production of different mycotoxins. On the other hand, most of these species have intrinsic resistance to azoles, which makes them refractory to the treatment of choice for aspergillosis [22,23,24,25].

Some characteristics present in Aspergillus fumigatus sensu stricto can partially explain why this species is the leading human and animal pathogen, such as rapid growth, small size of the conidia (1–4 µm), thermotolerance (growth between 15 °C and 55 °C, able to tolerate up to 70 °C), tolerance to high pH, low nutritional requirements, and production of secondary metabolites such as gliotoxin. The latter represents an important virulence factor [16,22,23,26] helping in tissue invasion. High thermotolerance is a factor that could benefit A. fumigatus in the environment, in comparison to other fungal species: its optimal growth temperature is 37 °C [27], which allows this species to be an important human pathogen. Given the current conditions of global warming, this feature could favor A. fumigatus growth and its dispersion in the environment [28].

How is aspergillosis diagnosed?

Many different tests may be employed if aspergillosis is suspected. Every test adds a piece to the puzzle, and more tests are frequently required to provide greater clarity.

Initially, a complete blood count (CBC) showing a marked increase in white blood cells could lead to concerns about an Aspergillus infection.

In the early stages of the disease, radiographs (X-rays) might only reveal mild lesions. Later in the illness, radiographs may show changes such as material in the trachea lumen, pneumonia, thickening of the air sacs, and fractures of bone segments.

Although serology (antibody) tests are available, they may yield false-negative results because the production of antibodies requires a functioning immune system. Many birds with aspergillosis have poorly functioning immune systems. False positive serology tests can also happen because Aspergillus spores are frequently found in the environment and many healthy birds can have antibodies to this fungus.

Aspergillus DNA can be found in blood or other tissues via DNA testing. The Aspergillus organism may be detected in the trachea or respiratory tract by a tracheal wash; nevertheless, even in healthy birds, spores may be present in trace amounts.

Surgical laparoscopy, which involves inserting a fiber-optic endoscope surgically into the bird’s airways to view the lungs, sinuses, air sacs, and trachea, is the most accurate diagnostic method. In a veterinary laboratory, samples of lesions are taken for microscopic examination and culture.

3. Aspergillosis in Humans

The Global Action Fund for Fungal Infections (GAFFI) estimates that aspergillosis affects over 15 million people’s health and results in over 1 million deaths annually [29]. As fungal infections have become more common in clinical medicine [30, 31, 32], so too have aspergillosis cases over the past few decades. According to an epidemiological study conducted in the US, the number of invasive aspergillosis (IA) cases per 10,000 hospital admissions may have increased from 3 in 1996 to 10 in 2009–2013 (data obtained between 2009 and 2013) [33].

Human aspergillosis clinical symptoms are categorized based on the degree of mycelial colonization or tissue invasion, and they are impacted by the host’s ability to mount an immune defense. The range of consequences includes allergic reactions and invasive infections. Individuals who have co-morbid conditions such as chronic granulomatous disease, bone marrow or solid organ transplantation, prolonged neutropenia, AIDS, or who have received prolonged treatment with steroids or other immunosuppressive drugs are at risk for developing IA [8,32], and mortality rates from acute IA can reach 80% in the first year following diagnosis [34, 35]. Recent research highlights the significance of IA in intensive care units, where its numbers have impressively increased over the last few decades, reaching mortality rates of up to 10% [36]. This is particularly the case for patients diagnosed with COVID-19, those receiving novel cancer chemotherapy modalities, and influenza patients [37, 38, 39, 40, 41, 42].

The most prevalent etiological agents in all of the aspergillosis presentations previously described are Aspergilli found in the section Fumigati. The species A. The most commonly isolated agent of aspergillosis in humans is fumigatus sensu stricto. However, Aspergillus sections have been the subject of more extensive molecular research since the early 2000s, and obscure species of the Fumigati section, like A lentulus, A. thermomutatus, and species of the viridinutans complex such as A. pseudofischeri and A. felis and other species have also been reported in cases of aspergillosis [22,43,44,45,46].

The National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) and the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group have established guidelines for classifying cases of aspergillosis [47]. However, aspergillosis case definitions may vary depending on the examined group and the clinical manifestations due to growing knowledge of new risk groups and their unique characteristics. There have been established case definitions for influenza-associated pulmonary aspergillosis in patients in the intensive care unit [49] and chronic pulmonary aspergillosis [48]. Additionally, epidemiological studies are being conducted to support the case definition of Covid-associated pulmonary aspergillosis (CAPA) in light of certain differences already discovered in cases [42,49,50].

4. Aspergillosis in Avian Species

Due to their unique anatomical and physiological features, such as the presence of air sacs with poor vascularization and limited mucociliary function, which create an ideal environment for fungal growth, birds are particularly vulnerable to aspergillosis. Furthermore, birds lack neutrophils and have heterophils instead, which may make them less effective against hyphal invasion [6,51,52]. Thus, aspergillosis is a leading cause of morbidity and mortality in birds, harming the environment and the economy. Moreover, this illness may have an effect on avian species in zoological parks and on wild animals undergoing rehabilitation [51,53,54,55].

Aspergillus section Fumigati is accountable for as many as 90% of deaths in birds suffering from aspergillosis [12, 52, 53]. A. The only etiologic agent of this section that has been found in birds thus far is fumigatus sensu stricto [55,56,57]. This might be connected to the virulence characteristics of this species, which include its capacity to grow at temperatures higher than those of birds (38–42 °C); the conidia’s smaller size relative to other genus sections, which facilitates penetration into the lower respiratory tract; and its increased gliotoxin production [23,53,58].

Aspergillosis in birds can present with nonspecific clinical signs that are frequently not noticeable until the illness is advanced. Regarding specific bird species, like penguins and albatrosses receiving care in rehabilitation facilities [12,55], as well as poultry (i e. , turkeys and chicks) in production settings [51,59]. Because managing flocks of birds is more common than managing a single bird, getting a diagnosis earlier can be even more difficult. Serological assays appear to be the most promising approach thus far in this context, where early diagnosis is crucial for determining treatments [59,60,61,62,63,64,65]. However, aspergillosis in birds is typically only diagnosed through post-mortem examination because there isn’t a reliable or affordable way to make an early diagnosis. White-yellow granulomas in the pulmonary parenchyma and/or air sac membranes are among the macroscopic findings observed during necropsy. In certain instances, the disease has spread to other organs, including the heart, liver, kidneys, and spleen. Furthermore, it has been documented in a number of bird species [5,6,51,66,67] that the lower respiratory tract can experience the growth of fungal colonies with a moderate to large production of conidia. The identification of the fungus in culture along with tissue invasion evidence and the finding of hyphae in histopathology confirm the diagnosis [6,53].

Poultry production and various avian livestock, including chickens, turkeys, geese, ducks, pigeons, emus, and ostriches, have been linked to aspergillosis cases. Young birds are the most affected [59,68,69,70]. Aspergillosis outbreaks in poultry are frequently observed, with mortality rates ranging from 4 5 and 90% [51]. The annual economic losses in this group due to turkey production can amount to US$ 11 million [66]. The losses stem from the condemnation of carcasses in slaughterhouses due to fungal pneumonia and air sacculitis, as well as from a decrease in bird growth and an increase in mortality [1,51,69]. High levels of humidity in the surroundings, inadequate ventilation in housing, the buildup of organic matter, and the use of bedding litter enriched with organic matter are risk factors for chickens [51, 71, 72]. These environmental conditions are optimal for Aspergillus growth. One risk factor for the development of avian aspergillosis is inhaling a larger inoculum, which is increased by high humidity levels and rich organic matter, which also promotes fungal multiplication and more airborne conidia [12,16,51,52,54].

Given the high death rate of wild birds housed in captivity, including zoological parks, avian wildlife rehabilitation facilities, and captive birds of prey utilized in falconry, aspergillosis is also a concern [54,55,56,73,74]. Aspergillosis is regarded as a significant fungal disease for rehabilitation of penguins in wildlife rehabilitation centers [54], with a mortality rate of approximately 50% in Magellanic penguins (Spheniscus magellanicus) kept in captivity [12]. Aspergillosis-related deaths are frequent in zoological institutions, in addition to Aspergillus outbreaks [75,76,77]. Although some reports have been published regarding the frequency of aspergillosis in comparison to what is known regarding aspergillosis in captive birds, there are still many unanswered questions regarding aspergillosis in wild birds that roam freely [78,79,80].

Given the high prevalence of fungal diseases in rehabilitation facilities and the possibility of increased exposure, azoles are frequently given to wild birds kept in captivity for both prophylactic and therapeutic purposes [9,11,12,55,81]. Prophylactic treatment of captive bird populations in zoological institutions can also be linked to environmental challenges and species susceptibility. Because of worries about the presence of medication residues in meat and the cost of treating aspergillosis, azoles are not often used in poultry farms. On farms, antifungal prophylaxis may be necessary, though, in certain exceptional cases [82]. However, azoles are frequently used for disinfecting environments and decontaminating bedding [51,70,71,82,83,84,85].

FAQ

How can avian aspergillosis be prevented?

Good hygiene, frequent cage cleaning, fresh and nutritious food, and good ventilation are all necessary for treating and preventing outbreaks of aspergillosis in birds.

How can Aspergillus be prevented?

Avoid activities that involve close contact to soil or dust, such as yard work or gardening. If this isn’t possible, Wear shoes, long pants, and a long-sleeved shirt when doing outdoor activities such as gardening, yard work, or visiting wooded areas. Wear gloves when handling materials such as soil, moss, or manure.

How do you prevent and control aspergillosis in poultry?

Prevention and treatment Clean and disinfect the hatchery on a regular basis. Commercial preparations of enilconazole have been used successfully to disinfect hatcheries and poultry farms. Develop a plan to monitor the presence of Aspergillus in the hatchery. Use clean, mold-free litter and feed.