Parasites, Fungi, and Acanthamoeba Flashcards
(28 cards)
What is the definition of parasitism?
Parasitism is a symbiotic relationship where one organism (the parasite) benefits at the expense of the host, causing harm or disease.
What are the two main categories of parasites?
Protozoa: Single-celled organisms that can be motile or non-motile.
Helminths: Multicellular parasitic worms, including roundworms, flatworms, and flukes.
How do protozoa move?
Protozoa can move through pseudopodia (amoebas), flagella (flagellates), or cilia (ciliates).
What are Acanthamoeba and its significance in ocular health?
Acanthamoeba is a free-living amoeba found in water and soil that can cause Acanthamoeba keratitis (AK), a severe eye infection, especially in contact lens wearers.
What are the common risk factors for Acanthamoeba keratitis (AK)?
Poor contact lens hygiene, including the use of tap water to clean lenses.
Swimming in contaminated water while wearing contact lenses.
Trauma or scratch to the cornea.
What are the symptoms of Acanthamoeba keratitis?
Symptoms of AK include severe eye pain, redness, blurry vision, photophobia, and a foreign body sensation in the eye.
How is Acanthamoeba keratitis diagnosed?
Diagnosis is confirmed by corneal scraping and microscopic examination, PCR, or culturing for Acanthamoeba.
What are the treatment options for Acanthamoeba keratitis?
Topical antimicrobial treatment with chlorhexidine and polyhexamethylene biguanide (PHMB), along with oral medications, are typically used to treat Acanthamoeba keratitis.
What is fungal keratitis, and what are its causes?
Fungal keratitis is an eye infection caused by fungi like Fusarium, Aspergillus, and Candida, often due to trauma involving vegetative matter or contact lens use.
What are the symptoms of fungal keratitis?
Symptoms of fungal keratitis include pain, redness, photophobia, decreased vision, and the presence of a white or grayish corneal infiltrate.
What is the pathogenesis of fungal keratitis?
Fungal keratitis is characterized by invasion of the corneal epithelium and stroma by fungal hyphae, leading to granular infiltrates, ulceration, and corneal scarring.
What is the treatment for fungal keratitis?
Treatment involves antifungal agents like natamycin, amphotericin B, or voriconazole. In some cases, surgical intervention (e.g., corneal transplant) may be needed for severe cases.
What are apicomplexa protozoa, and what role do they play in ocular health?
Apicomplexa are non-motile protozoa that include species like Plasmodium (causing malaria) and Toxoplasma, which can cause ocular toxoplasmosis.
What is the life cycle of Plasmodium and how does it relate to ocular infections?
Plasmodium is transmitted to humans by Anopheles mosquitoes. It undergoes an asexual phase in the liver and sexual phase in mosquitoes. Ocular manifestations of malaria include retinal hemorrhages and retinopathy.
What is ocular toxoplasmosis, and what are its symptoms?
Ocular toxoplasmosis is caused by Toxoplasma gondii, a protozoan that infects the eye, leading to retinitis, chorioretinitis, and vision loss.
What are the common causes of ocular infections due to parasites?
Common causes include Acanthamoeba (keratitis), Toxoplasma gondii (ocular toxoplasmosis), and Plasmodium falciparum (malaria), which affect different parts of the eye like the cornea, retina, and choroid.
What is the role of immune suppression in increasing the risk of ocular parasitic infections?
Immune suppression (e.g., due to HIV, corticosteroid use, or organ transplantation) increases the risk of ocular infections due to parasites like Acanthamoeba and Toxoplasma because the immune system is less capable of controlling the spread of these organisms.
What is malaria retinopathy and its ocular implications?
Malaria retinopathy refers to the retinal changes caused by Plasmodium falciparum infection. This can include retinal hemorrhages, cotton-wool spots, and retinal pigmentary changes, which can impair vision.
How do helminths (parasitic worms) impact ocular health?
Helminths, such as Loa loa and Onchocerca volvulus, can migrate to the eye and cause uveitis, corneal opacities, and blindness. Onchocerciasis (river blindness) is a major cause of blindness in some tropical regions.
What are the common helminth infections that affect the eye?
Onchocerciasis (river blindness): Caused by Onchocerca volvulus, leading to blindness.
Loa loa: African eye worm that can migrate to the conjunctiva and cornea.
Toxocariasis: Caused by Toxocara canis, affecting children and causing ocular granulomas.
: How does Acanthamoeba cause eye infections in contact lens wearers?
Acanthamoeba can infect the cornea of contact lens wearers through contaminated water (e.g., tap water or swimming pools) and cause keratitis, potentially leading to vision loss if untreated.
What are the treatment options for Acanthamoeba keratitis?
Treatment for Acanthamoeba keratitis includes topical antimicrobial agents such as chlorhexidine and polyhexamethylene biguanide (PHMB), and in some cases, oral medications. Surgical options like corneal transplant may be required for severe cases.
What is the significance of fungal keratitis in contact lens wearers?
Contact lens wearers are at a higher risk for fungal keratitis, particularly when they have trauma or poor lens hygiene. Fungi like Fusarium and Aspergillus can invade the cornea, causing persistent infections.
the locomotion of an amoeba?
Pseudopods
