The Facets of Aspergillosis in Humans

There have been over 185 fungal species identified as belonging to the family of Aspergillus. While infection is quite common in many forms, among birds, only 20 species have been identified as causative organisms of opportunistic illness in humans (Aspergillus species, n.d.). Human illness tends to strike at those suffering from immunosuppression, although some few infected are immunocompetent hosts with an underlying pulmonary condition (Remicade, 2004). Humans can contract any of four forms called acute (or invasive) pulmonary aspergillosis, chronic pulmonary aspergillosis, allergic bronchopulmonary aspergillosis or allergic sinusitis. Birds can also die from toxicosis due to the ingestion of large amounts of Aspergillus vegetative cells or spores. The search is ongoing for better methods of early detection and treatment. Aspergillus niger has also recently been shown to breakdown the causative toxin in a common scab disease of potatoes.

The Facets of Aspergillosis

Introduction

Aspergillosis is the most common fungal respiratory disease among birds (Aspergillosis, 2002). Birds can develop toxicosis through ingestion of a large number of spores. It can also become an opportunistic infection among humans, in which the fungus can manifest itself in four ways; acute, chronic, and allergic bronchopulmonary aspergillosis in asthmatics, as well as allergic sinusitis due to spore inhalation (Aspergillus spp., 2006).

Responsible Organism

Of 185 identified species of Aspergillus, only 20 have been shown to be pathogenic. Some species, such as Aspergillus fumigatus and A. flavis have been proven to develop toxins. Other species frequently identified in infection are A. niger, A. nidulans, A. terreus, A. glaucus, and Pennicillium.

Environmental Factors

Spores (conidia) produced by the vegetative fungal cells, can cause infection through inhalation in humans, and inhalation and/or ingestion in birds. Ingestion of the spores in large amounts can result in toxicosis and death in birds (Pesek, 1996). Aspergillus conidia are found all over the world. They are located in building materials, foul water, unwashed food, ornamental plants, hospitals, closed air environments, household dust, dead leaves, compost, dead fall, decaying vegetation, in soil, inadequately cleaned bird cages, moldy seed, and other fungus producing matter.

Characteristics

The fungus has been described as "filamentous, cosmopolitan, and ubiquitous (Aspergillus spp., 2006)." Some few have been found to have a teleomorphic state. Most create mitospores, with no identified sexual spores (diploid).

Diseases

Chronic Aspergillosis

In chronic aspergillosis scar tissue of the lungs, caused by smoking or previous pulmonary illness, become colonized by pockets of fungal tissue called aspergilloma. Patients with this form may be immunocompetent, but suffer from an underlying lung disease. Aspergillosis can be picked up in the hospital (nosocomial illness), with outbreaks of cutaneous infection occasionally reported in connection with medical devices contaminated with the fungus.

Acute Aspergillosis

Acute, or invasive, pulmonary aspergillosis manifests initially as a colonization of the lung tissue with symptoms resembling pneumonia, with a deep cough and chest pain. The fungus then enters the blood stream through the aveolar sacs and migrates to other parts of the body. The eye is often affected, causing the patient to go blind. The bone, heart, lungs, brain, and kidneys are all at high risk of invasive infection. This illness affects almost noone who is not immunosuppressed. Mortality rate can be very high with out early detection.

Population Most Affected

Aspergillus is the second most commonly identified fungus in opportunistic fungal infections. Infection occurs primarily in those people with suppressed or compromised immune systems. This would include AIDS patients, organ transplant recipients, cancer patients, those on corticosteroid medications, suffering from an autoimmune disease such as lupus, or other diseases affecting blood cells.

Works Cited

Allergic bronchopulmonary aspergillosis. (2002). Retrieved May 1, 2006, from http://www.healthatoz.com/healthatoz/Atoz/ency/allergic_bronchopulmonary_aspergillosis....
Aspergillosis. (2002). Retrieved May 1, 2006, from http://www.michigan.gov/printerFriendly/0,1687,7-153-10370_12150_12220-26360--CI,00....
Aspergillosis. (2005). Retrieved April 26, 2006, from http://www.cdc.gov/ncidod/dbmd/diseaseinfo/asperfillosis_t.htm
Aspergillosis. Retrieved April 26, 2006, from http://www.multiscope.com/hotspot/aspergil.htm
Aspergillus spp. January 19, 2006. Retrieved April 26, 2006, from http://www.doctorfungus.org/Thefungi/asperfillus_spp.htm
Lazarovits, G., Hill, J., King, R., and Calhoun, L. A. (2004). Biotransformation of Streptomyces scabies phytotoxin thaxtomin A by the fungus Aspergillus niger. Canada: NRC Research Press.
Pesek, L., DVM. (1996). Ask the Vet (Aspergillosis Part I). Retrieved May 1, 2006, from http://theaviary.com/s1295-60.shtml
Remicade and aspergillosis. (2004). Retrieved May 1, 2006, from http://www.remicade-lawyer.com/aspergillosis.html