The primary eye disease linked to birds is presumed ocular histoplasmosis syndrome (POHS), caused by the fungus Histoplasma capsulatum.
Understanding Presumed Ocular Histoplasmosis Syndrome (POHS)
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Cause: POHS occurs when the fungus Histoplasma capsulatum infects the body and subsequently affects the eyes. This fungus thrives in soil contaminated with bird and bat droppings.
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Geographic Prevalence: POHS is most common in areas with high concentrations of Histoplasma capsulatum, particularly in the central United States (e.g., the Ohio and Mississippi River valleys).
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Risk Factors: Exposure to environments with bird and bat droppings increases the risk of contracting histoplasmosis, which can then lead to POHS. Activities such as farming, construction, and exploring caves can elevate the risk.
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Symptoms: The initial Histoplasma capsulatum infection is often asymptomatic or presents with mild flu-like symptoms. However, the ocular manifestations of POHS can include:
- Chorioretinal scars: Small, white or gray spots on the retina.
- Neovascularization: Abnormal blood vessel growth in the retina, potentially leading to bleeding and vision loss.
- Macular complications: Involvement of the macula (central part of the retina) can severely impair central vision.
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Diagnosis: Diagnosis typically involves:
- Ophthalmologic examination: A thorough eye exam to identify characteristic retinal lesions.
- Fluorescein angiography: A test that uses dye to visualize blood vessels in the retina and detect abnormal vessel growth.
- Optical coherence tomography (OCT): An imaging technique that provides detailed cross-sectional views of the retina.
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Treatment: Treatment depends on the severity and location of the lesions. Options include:
- Observation: For inactive lesions that do not threaten vision.
- Anti-VEGF injections: To reduce neovascularization and prevent vision loss.
- Laser photocoagulation: To seal off abnormal blood vessels.
- Corticosteroids: In some cases, to reduce inflammation.
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Prevention: While avoiding areas with high concentrations of bird and bat droppings is ideal, it's often impractical. Regular eye exams are crucial for early detection and management of POHS, especially for individuals at increased risk.
In summary, while other pathogens carried by birds could theoretically cause eye infections, the most well-known and significant connection between birds and eye disease is through the Histoplasma capsulatum fungus found in soil contaminated with bird droppings, leading to presumed ocular histoplasmosis syndrome (POHS).
