Air Microbiology (Aerobiology) and Causes of Air-Borne Diseases
Aerobiology is defined as the study of life present in the air. Aeromicrobiology relates to the study of environmentally relevant micro-organisms. Intramural Aerobiology deals with indoor environment while Extramural Aerobiology deals with outdoor environment. No organism is indigenous to the atmosphere.
Micro-organisms exist within 300-1000 feet of earth‘s surface that have become attached to fragments of dried leaves, straw or dust particles light enough to be blown by wind. In dry weather, the microbial load of air is high while in wet weather the rain washes the micro-organisms from the air.
Air is not a medium in which micro-organisms grow, but it is a carrier of dust and droplets that may be laden with microorganisms. Large droplets settle out quickly while the droplet nuclei remain afloat.
The spore formers and cyst formers are likely to survive better in the atmosphere for longer period. Depending upon the type and the climatic conditions the persistence of micro-organisms is observed. The micro- organisms come into the air via both land and water. Wind creates dust laden with microbes.
From the ocean surface water droplets laden with microbes arise. Various agricultural, industrial and municipal processing facilities have the potential for generating microbe laden aerosols. The irrigation sprinkler, grain thrashing, sewage treatment facility, abattoirs etc., can serve as sources.
Air-Borne Diseases
Air-borne diseases are caused by hardy micro-organisms and include diseases of plants, animals and human. The impact of plant pathogens esp. fungi on agricultural economy is enormous. Infection of pet and livestock by airborne pathogens is also significant as are the diseases in humans.
The kinds of pathogenic micro-organisms present in the atmosphere associated with humans are viruses, protozoa, molds and bacteria. The table below summarizes the wide adverse effects on humans by contaminants present in the air which also includes the bacterial and fungal toxins.
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Air pollution by exhausts from industries is another matter. The consequences of industrial air pollution are irritation of skin, eyes and respiratory tract, thereby posing health hazards.
Toxins of Clostridium botulinum is a potential biological warfare agent Bacillus anthracis has been used effectively in germ or biological warfare. A sophisticated training and machinery is required to tackle these agents.
Table: Air-borne Human Diseases of Importance and their Causative Agent
| Bacteria | Disease | Virus | Disease | |
| Streptococcus pyogenes | Sore throat | Influenza virus | Influenza | |
| Corynebacterium diphtheriae | Diphtheria | Hantavirus | Pulmonary syndrome | |
| Mycobacterium tuberculosis | Tuberculosis | Hepatitis virus | Hepatitis | |
| Streptococcus pneumoniae | Pneumococcal pneumonia | Herpes virus | Chicken pox | |
| Klebsiella pneumoniae | atypical pneumonia | Picorna virus | Common cold | |
| Neisseria meningitidis | Meningococcal meningitis | Flavivirus | Dengue fever | |
| Yersinia pestis | Bubonic plaque | Rubella virus | Rubella | |
| Bordetella pertussis | Whooping cough | Measles virus | Measles | |
| Haemophilus influenzae | Influenza | Influenza virus | Influenza | |
| Nocardia asteroids | Nocardiosis | Hantavirus | Pulmonary syndrome | |
| Fungi | Disease | |||
| Aspergillus fumigatus | Aspergillosis | |||
| Blastomyces dermatiridi | Blastomycosis | |||
| Coccidioides immitis | Coccidioidomyosis | |||
| Cryptococcus neoformans | Cryptococcosis | |||
| Histoplasma capsulatum | Histoplasmosis | |||
| Pneumocystis carinii | Pneumocystitis |
Table: Adverse Effects on Humans and Environment Associated with Exposure to Airborne Micro-organisms
| S/N | Agent | Humans | Environment |
| 1. | Algae | Allergy | Odor |
| 2. | Bacteria | Hypersensitivity, respiratory infections | Plant diseases, odor |
| 3. | Fungi | Allergy, skin problems, respiratory infections | Deterioration of building materials, odor, plant diseases |
| 4. | Endotoxin | Cough, headache, respiratory distress | None |
| 5. | Mycotoxin | Cough, headache, respiratory distress | Disease in livestock |
| 6. | Protozoa | Encephalitis, hypersensitivity infections | Protect other bacteria, disease to livestock |
| 7. | Virus | Infections | Crop and livestock disease |
Without the knowledge of microbiology, the above ideas would have been strange before man and death of humans would have been recorded in their millions.
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