Parasitology Overview

Parasitology Overview

Parasitology is a vast and complex subject encompassing various organisms. To better understand them, we will analyze the relationships between parasites and their hosts:

1. Symbiotic relationships:

– Mutualism: Two organisms live together, both benefiting. Example: Termites and protozoans living in the termite gut.

– Commensalism: Two organisms live together, one benefits while the other is neither harmed nor benefited. Example: Crabs and sea anemones.

– Phoresy: A smaller organism “carries” a larger one. Example: Protozoa, fungi.

2. Parasitism:

– Parasites depend on their host for survival, using the host as a food source and shelter.

– Parasites can harm the host, affecting their health and even causing death.

– Example: Plasmodium (malaria parasite) living in human red blood cells.

Parasite Classification:

– By location of parasitism:

– Endoparasites: Living inside the host’s body. Example: Roundworms in the human intestine.

– Ectoparasites: Living on the host’s surface. Example: Mosquitoes sucking blood on the skin.

– By relationship with the host:

– Permanent parasite: Parasites living in the host for a long time or throughout their lifespan. Example: Roundworms.

– Temporary parasite: Parasites only living in the host for a short time or when needed for food. Example: Mosquitoes.

– Based on parasitic ability:

– Monoparasite: Parasites living only in one host species. Example: Ascaris lumbricoides (roundworm).

– Polyparasite: Parasites living in various host species. Example: Liver fluke, Toxoplasma gondii.

– Aberrant host: Parasites cannot mature and reproduce in the aberrant host.

– Accidental/Incidental: Parasites parasitize the host accidentally. Example: Naegleria amoeba.

Host:

– Living organism exploited by parasites for nutrients.

Host Classification:

– Definitive host (permanent): Carries the adult parasite.

– Intermediate host: Carries immature parasites.

– Intermediate host: A temporary environment, necessary for parasite development. Parasites may reproduce in the intermediate host.

– Transport host (vector): Temporary shelter, a necessary means to find the definitive host. Example: Flies are vectors for single-celled parasites.

– Vector: Arthropods or vertebrates that transmit parasites from one host to another. Example: Anopheles mosquitoes transmit Plasmodium falciparum (malaria parasite).

Transmission of disease by vectors:

– Mechanical route: Parasites adhere to the surface or pass through the vector’s digestive tract but do not reproduce or develop. Example: Flies transmit amoebic dysentery (intestinal disease).

– Biological route: Parasites undergo developmental stages and may reproduce in the vector. Example: Plasmodium falciparum is transmitted by Anopheles spp. mosquitoes.

Life cycle of a parasite:

– The complete developmental process of the parasite through different stages.

– Life cycle types:

– Type 1: Entirely in the environment (e.g., mosquito life cycle).

– Type 2: Entirely on the host’s body (e.g., Trichomonas vaginalis).

– Type 3: Host…environment (e.g., intestinal worms).

– Type 4: Host…environment…intermediate host (e.g., liver fluke).

– Type 5: Host…intermediate host (e.g., Plasmodium species).

Ecological characteristics of parasites:

– Parasites are usually smaller than the host.

– Factors affecting the host indirectly influence parasites.

Parasite morphology:

– Round, oval, tube-shaped.

– Single-celled: Round and oval.

– Roundworms: Tubular.

– Tapeworms: Long, ribbon-like body.

Reproduction of parasites:

– Asexual: Single-celled, fungi.

– Sexual: Worms, ticks, fungi, single-celled organisms.

– Sporulation: In the larval stage, found in some flukes.

Harmful effects of parasites:

– Tissue damage:

– Albumin/fat degeneration/necrosis: Example: Trichinella spiralis causes degeneration of the surrounding tissues.

– Tissue structure changes:

– Hyperplasia: Clonorchis sinensis causes thickening of the bile duct.

– Hypertrophy: Plasmodium vivax causes red blood cell enlargement.

– Neoplasia: Paragonimus westermani (formation of a different type of tissue).

– Proliferation (tumor): Fasciola hepatica causes tumors in the liver. Schistosoma haematobium causes malignant tumors in the bladder.

Nomenclature:

– Latin.

– Family ending in IDEA, subfamily ending in INAE.

– Genus (capitalized) + species (lowercase).

6 Kingdoms:

– Bacteria

– Animals

– Plantae

– Fungi

– Chromista (multicellular)

– Prozota (single-celled)

Kingdom Animalia:

– Phylum Nematoda (roundworms)

– Phylum Platyhelminthes (flukes): divided into 4 classes, two commonly found:

– Cestoda (tapeworm): tapeworms.

– Trematoda (flatworm): flukes.

– Phylum Arthropoda (arthropods)

Kingdom Protozoa:

– 7 phyla

Some common parasites:

– Aspergillus: Mainly causes lung disease.

– Aspergillus flavus: Causes liver cancer.

– Aspergillus oryzae: Ferments food.

– Skin diseases: Trichophyton spp., Microsporum, Epidermophyton.

– Candida: Causes skin, intestinal, genital, and organ diseases.

– Coccidioides immitis: Causes severe pneumonia.

– Blastomyces dermatitidis: Acute respiratory infection.

– Cryptococcus neoformans: Central nervous system disease.

– Enterocytozoon bienusi: Diarrhea, cholecystitis.

Note:

– This is just a basic understanding of parasites.

– For a deeper understanding of this subject, further research is necessary.

– Always follow healthcare guidelines to prevent and treat parasitic diseases.