21.5 Protozoan and Helminthic Infections of the Skin and Eyes

Acanthamoeba is a genus of free-living, opportunistic protozoan parasites that can infect the skin, eyes, and central nervous system in humans. These amoebae are ubiquitous in the environment and can cause serious infections, particularly in individuals with compromised immune systems.

Amoebic Keratitis: A serious eye infection caused by Acanthamoeba that can lead to vision loss if not promptly treated.

Granulomatous Amoebic Encephalitis (GAE): A rare but often fatal infection of the central nervous system caused by Acanthamoeba, typically seen in immunocompromised individuals.

Acanthamoeba Castellanii: The most common species of Acanthamoeba that is responsible for the majority of human infections.

Loa loa, also known as the African eye worm, is a parasitic nematode that infects humans and can cause a range of skin and eye-related conditions. It is primarily found in certain regions of West and Central Africa and is transmitted through the bites of infected deerflies.

Onchocerciasis: A parasitic infection caused by the nematode Onchocerca volvulus, which is transmitted by blackflies and can lead to river blindness.

Filariasis: A group of diseases caused by parasitic filarial worms, including Loa loa, which can lead to lymphatic system damage and elephantiasis.

Deerfly: A type of biting fly that can transmit the Loa loa parasite to humans through its blood-feeding behavior.

The African eye worm, also known as Loa loa, is a parasitic nematode worm that can infect the eyes and subcutaneous tissues of humans. It is primarily found in tropical regions of West and Central Africa and is transmitted by the biting mango fly.

Onchocerciasis: Also known as river blindness, this is a disease caused by infection with the parasitic worm Onchocerca volvulus, which is transmitted by blackflies and can lead to severe eye and skin disease.

Lymphatic Filariasis: A tropical disease caused by parasitic filarial worms that are transmitted by mosquitoes and can lead to swelling of the limbs, a condition known as elephantiasis.

Mango Fly: The biting midge fly that serves as the vector for transmission of the African eye worm, Loa loa, by feeding on infected human hosts.

A trophozoite is the active, feeding, and replicating stage of a protozoan parasite that infects a host. It is the form of the parasite that is responsible for causing disease and symptoms in the infected individual.

Cyst: The dormant, non-feeding, and environmentally resistant stage of a protozoan parasite that allows it to survive outside a host and facilitate transmission to a new host.

Sporozoite: The infective stage of a protozoan parasite that is introduced into the host during the bite of an infected vector, such as a mosquito or tick.

Merozoite: The stage of a protozoan parasite that is responsible for the repeated cycles of infection and replication within the host's cells.

A cyst is a closed, membrane-bound structure that contains liquid, gaseous, or solid material. Cysts can develop in various parts of the body and are commonly associated with parasitic infections, particularly in the context of unicellular eukaryotic parasites, protozoan and helminthic infections of the skin and eyes, and protozoan infections of the gastrointestinal tract.

Trophozoite: The active, feeding stage of a protozoan parasite that is responsible for the clinical manifestations of the infection.

Encystment: The process by which a protozoan parasite transforms from the active trophozoite stage into the dormant, resistant cyst stage.

Excystment: The process by which a protozoan parasite emerges from the cyst stage and reverts to the active trophozoite stage.

Contact lenses are thin, curved lenses placed directly on the surface of the eyes to correct vision or for cosmetic reasons. They can create a favorable environment for microbial growth if not properly maintained.

Microbial Keratitis: An infection of the cornea caused by bacteria, fungi, or protozoa, often linked to contact lens use.

Acanthamoeba: A genus of amoebae that can cause severe eye infections in contact lens wearers.

Biofilm: A structured community of microorganisms encapsulated within a self-produced matrix, adhering to surfaces such as contact lenses.

Acanthamoeba keratitis is a serious eye infection caused by a free-living, opportunistic protozoan parasite known as Acanthamoeba. It primarily affects the cornea, the clear, dome-shaped front part of the eye, and can lead to severe vision impairment or blindness if left untreated.

Acanthamoeba: A genus of free-living, opportunistic protozoan parasites that can infect the human eye, central nervous system, and other organs.

Keratitis: Inflammation of the cornea, the clear, dome-shaped front part of the eye.

Opportunistic Infection: An infection caused by a microorganism that takes advantage of a weakened or compromised immune system.

Granulomatous amebic encephalitis (GAE) is a rare and severe infection of the brain caused by free-living amoebas, primarily Acanthamoeba species and Balamuthia mandrillaris. It typically affects individuals with compromised immune systems and can lead to progressive and often fatal inflammation of the brain and central nervous system.

Acanthamoeba: A genus of free-living amoebas that can cause granulomatous amebic encephalitis and other serious infections in humans.

Balamuthia mandrillaris: A free-living amoeba that can also cause granulomatous amebic encephalitis, especially in immunocompromised individuals.

Opportunistic infection: An infection caused by a microorganism that typically does not cause disease in healthy individuals but can cause serious illness in those with weakened immune systems.

Pathogenesis refers to the biological mechanisms by which a disease or disorder develops and progresses within a host organism. It encompasses the complex interplay between the pathogen and the host's immune system, leading to the manifestation of clinical symptoms and the establishment of the disease state.

Virulence Factors: Specific molecular components or mechanisms that enable a pathogen to cause harm or damage to the host, contributing to the pathogenesis of the disease.

Host-Pathogen Interactions: The dynamic interplay between the pathogen and the host's immune system, which can determine the outcome of the infection and the development of the disease.

Evasion of Host Defenses: The ability of a pathogen to circumvent or suppress the host's immune responses, allowing it to establish and propagate the infection, a crucial aspect of pathogenesis.

Loiasis is a parasitic infection caused by the filarial nematode Loa loa, commonly known as the African eye worm. It primarily affects the skin and eyes of humans.

Onchocerciasis: A parasitic disease caused by Onchocerca volvulus, also known as river blindness.

Filariasis: A group of tropical diseases caused by thread-like filarial nematodes.

Microfilariae: The larval stage of filarial worms that circulate in the bloodstream.

Calabar swellings are localized, transient, and non-pitting edematous swellings that occur in certain parasitic infections, particularly those caused by filarial nematodes. They are an important clinical manifestation in the context of protozoan and helminthic infections of the skin and eyes.

Filariasis: A parasitic disease caused by thread-like filarial worms that are transmitted by mosquitoes and can lead to various clinical manifestations, including Calabar swellings.

Onchocerciasis: Also known as river blindness, this is a parasitic disease caused by the filarial worm Onchocerca volvulus, which can result in Calabar swellings as well as eye and skin complications.

Edema: The abnormal accumulation of fluid in the tissues, leading to swelling, which is the key characteristic of Calabar swellings.

Microfilariae are the larval stage of filarial nematodes, which are parasitic worms that can infect the skin and eyes. These microscopic, thread-like larvae are a crucial part of the life cycle of these parasites and are responsible for the transmission and spread of filarial infections.

Filarial Nematodes: A group of parasitic worms that can cause various diseases, including lymphatic filariasis and onchocerciasis, by infecting the skin, lymphatic system, and eyes.

Lymphatic Filariasis: A tropical disease caused by filarial nematodes that can lead to the obstruction of the lymphatic system, resulting in the swelling of limbs, a condition known as elephantiasis.

Onchocerciasis: Also known as river blindness, a disease caused by the filarial nematode Onchocerca volvulus, which can lead to severe skin lesions and vision impairment or blindness.

Diethylcarbamazine is an antihelminthic medication used to treat infections caused by certain parasitic worms, including those affecting the skin and eyes. It works by paralyzing and killing microfilariae and adult worms.

Filarial Infections: Diseases caused by infection with filarial nematodes such as Wuchereria bancrofti.

Loiasis: A parasitic disease caused by the African eye worm Loa loa.

Microfilariae: The larval stage of filarial nematodes that circulate in the blood.

Encephalopathy is a general term that refers to any disease or dysfunction of the brain, often characterized by altered mental state, impaired cognitive function, and neurological abnormalities. It can have various underlying causes, including infections, toxins, metabolic disorders, and structural brain damage.

Neuropathy: A disease or dysfunction of the nerves, often causing weakness, numbness, and pain.

Myelopathy: A disease or dysfunction of the spinal cord, leading to impaired motor and sensory function.

Encephalitis: Inflammation of the brain, often caused by viral or bacterial infections, which can result in encephalopathy.

Albendazole is a broad-spectrum anthelmintic (antiparasitic) drug primarily used to treat infections caused by various types of parasitic worms, including those that can infect the skin, eyes, and gastrointestinal tract. It works by interfering with the structural integrity and function of the parasites, leading to their death and expulsion from the host's body.

Anthelmintic: A class of drugs that are effective against parasitic worms, also known as helminths, by killing or expelling them from the host's body.

Benzimidazole: A class of organic compounds that includes albendazole and other antiparasitic drugs, which target the structural components of parasitic worms.

Helminth: A parasitic worm that can infect the human body, including various types of roundworms, tapeworms, and flukes.

Ivermectin is an antiparasitic drug used to treat various helminthic infections. It works by binding to glutamate-gated chloride channels in the parasite's nerve and muscle cells, causing paralysis and death of the parasite.

antiparasitic drugs: Medications used to treat infections caused by parasites such as protozoa, helminths, and ectoparasites.

helminthic infections: Diseases caused by parasitic worms, including roundworms, tapeworms, and flukes.

glutamate-gated chloride channels: Ion channels targeted by certain antiparasitic drugs, crucial for nerve signal transmission in some parasites.

Chrysops is a genus of flies, commonly known as deer flies, that are vectors for the transmission of certain protozoan and helminthic infections affecting the skin and eyes. These biting flies are found worldwide and are known for their aggressive feeding behavior and ability to transmit diseases to humans and animals.

Tabanidae: The family of flies that Chrysops belongs to, also known as horse flies or deer flies, which are characterized by their large size, brightly colored eyes, and painful bites.

Onchocerciasis: A parasitic disease caused by the nematode worm Onchocerca volvulus, which is transmitted by Simulium blackflies and can lead to severe skin and eye infections, including river blindness.

Loiasis: A parasitic infection caused by the filarial worm Loa loa, which is transmitted by Chrysops flies and can cause intermittent swelling, skin rashes, and eye problems.

Vector-borne transmission refers to the mode of disease transmission where pathogens are carried and transmitted by living organisms, known as vectors, to human hosts. This mode of transmission is particularly relevant in the context of protozoan and helminthic infections affecting the skin and eyes.

Vector: An organism, often an insect or arachnid, that can transmit infectious pathogens from one host to another.

Zoonosis: An infectious disease that can be transmitted from animals to humans, often via a vector.

Arthropod-Borne Diseases: Diseases transmitted by arthropod vectors, such as mosquitoes, ticks, and sand flies, which can carry and spread pathogens.

Zoonotic infections are diseases that can be transmitted from animals to humans. These types of infections are caused by pathogens, such as viruses, bacteria, parasites, and fungi, that are able to cross the species barrier and infect both animal and human hosts.

Reservoir Host: An animal species in which a pathogen can survive and multiply, serving as a source for potential transmission to humans.

Vector: An organism, such as an insect or tick, that can transmit a pathogen from an infected animal to a human.

Spillover Event: The process by which a pathogen jumps from an animal host to a human, often due to increased contact or disruption of natural habitats.

Parasitology is the study of parasites, their hosts, and the relationship between them. It encompasses the investigation of protozoan and helminthic (worm) infections that can affect the skin and eyes, as outlined in the topics 21.5 Protozoan and Helminthic Infections of the Skin and Eyes.

Parasite: An organism that lives on or inside another organism (the host) and benefits by deriving nutrients, shelter, or other necessities from it, often to the detriment of the host.

Protozoan: A single-celled eukaryotic organism that can act as a parasite, causing various infectious diseases in humans and animals.

Helminth: A parasitic worm, such as a tapeworm, roundworm, or fluke, that can infect the skin, eyes, and other parts of the human body.

Global health is an area of study, research, and practice that places a priority on improving health and achieving health equity for all people worldwide. It encompasses the transnational approach to health issues that transcend national boundaries, with a focus on the socioeconomic, political, and environmental determinants of health.

Epidemiology: The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to control health problems.

Neglected Tropical Diseases (NTDs): A diverse group of communicable diseases that prevail in tropical and subtropical conditions in 149 countries, affecting more than 1 billion people and costing developing economies billions of dollars every year.

Social Determinants of Health: The conditions in which people are born, grow, live, work and age, including the health system. These circumstances are shaped by the distribution of money, power, and resources at global, national, and local levels.