Parasitology & Parasites

Parasitology & Parasites: An Overview

Parasitology is the branch of biology and medicine that studies parasites, their hosts, and the relationship between them. It covers a wide range of organisms, from protozoa to helminths and arthropods, which can cause diseases in humans, animals, and plants.

Types of Parasites

Parasites can be classified based on their nature, host dependency, and life cycle.

1. Classification by Type

• Protozoa (Single-Celled Parasites)
  • Example: Plasmodium spp. (Malaria), Entamoeba histolytica (Amebiasis), Giardia lamblia (Giardiasis)
• Helminths (Worms)
  • Nematodes (Roundworms) – Ascaris lumbricoides, Enterobius vermicularis
  • Cestodes (Tapeworms) – Taenia solium, Echinococcus granulosus
  • Trematodes (Flukes) – Schistosoma spp., Fasciola hepatica
• Arthropods (Ectoparasites)
  • Example: Sarcoptes scabiei (Scabies), Pediculus humanus (Lice)

2. Classification by Host Dependency

• Obligate Parasites – Completely dependent on a host (e.g., Plasmodium spp.).
• Facultative Parasites – Can live freely but may become parasitic (e.g., Naegleria fowleri).
• Temporary Parasites – Only attach to a host for feeding (e.g., mosquitoes, ticks).
• Permanent Parasites – Live their entire life inside the host (e.g., Tapeworms).

3. Classification by Life Cycle

• Direct Life Cycle – Parasite completes its cycle within a single host (e.g., Enterobius vermicularis).
• Indirect Life Cycle – Requires multiple hosts (e.g., Schistosoma spp., Taenia solium).

Parasitic Diseases & Their Impact

Parasites cause a wide range of diseases, including:

1. Malaria – Plasmodium spp., transmitted by Anopheles mosquitoes.
2. Schistosomiasis – Schistosoma spp., infects via freshwater snails.
3. Filariasis – Wuchereria bancrofti, causes elephantiasis, spread by mosquitoes.
4. Leishmaniasis – Leishmania spp., transmitted by sandflies.
5. Amoebiasis – Entamoeba histolytica, causes dysentery.
6. Cysticercosis – Taenia solium larvae, can cause brain infections.
7. Hydatid Disease – Echinococcus spp., affects liver/lungs.

Diagnosis & Treatment

• Diagnosis: Stool tests, blood smears, serology, molecular tests (PCR).
• Treatment:
  • Antiprotozoal drugs: Metronidazole, Chloroquine.
  • Antihelminthic drugs: Albendazole, Praziquantel.
  • Ectoparasite treatments: Permethrin, Ivermectin.

Prevention & Control

• Hygiene & Sanitation: Clean water, handwashing.
• Vector Control: Mosquito nets, insecticides.
• Proper Cooking: Avoid raw or undercooked meat/fish.
• Vaccines: In development for malaria and other parasitic diseases.