Parasitic agents are organisms that live on or in a host, deriving nutrients at the host’s expense. They include protozoa, helminths (worms), and ectoparasites like lice and ticks.
Table of Contents
Protozoan Parasite
Causative Agent: Giardia intestinalis
- Primary (Definitive) Host: Humans
- Secondary (Intermediate) Host: None
- Habitat: Small intestine
- Disease/Pathogenicity: Giardiasis
- Drugs Used for Treatment: Metronidazole, Tinidazole, Nitazoxanide
Causative Agent: Trypanosoma brucei gambiense
- Primary (Definitive) Host: Humans
- Secondary (Intermediate) Host: Tsetse fly (Glossina sp.)
- Habitat: Bloodstream and central nervous system
- Disease/Pathogenicity: African trypanosomiasis (sleeping sickness)
- Vector/Carrier: Tsetse fly
- Drugs Used for Treatment: Pentamidine, Suramin, Melarsoprol, Eflornithine, Nifurtimox
Causative Agent: Leishmania donovani
- Primary (Definitive) Host: Humans
- Secondary (Intermediate) Host: Sandfly (Phlebotomus sp.)
- Habitat: Reticuloendothelial system (spleen, liver, bone marrow)
- Disease: Leishmaniasis (kala-azar)
- Vector/Carrier: Sand fly
- Drugs Used for Treatment: Amphotericin B, Miltefosine, Sodium stibogluconate, Paromomycin
Parasitic Agents: Platyhelminthes
Causative Agent: Taenia saginata
- Primary (Definitive) Host: Humans
- Secondary (Intermediate) Host: Cattle
- Habitat: Small intestine
- Disease: Taeniasis, Cysticercosis
- Vector/Carrier: Cattle
- Drugs Used for Treatment: Praziquantel, Niclosamide
Causative Agent: Schistosoma haematobium
- Primary (Definitive) Host: Humans
- Secondary (Intermediate) Host: Freshwater snails (Bulinus sp.)
- Habitat: Uterine plexus
- Disease: Schistosomiasis
- Vector/Carrier: Freshwater snail
- Drugs Used for Treatment: Praziquantel
Parasitic Agents: Nematode
Causative Agent: Ascaris lumbricoides
- Primary (Definitive) Host: Humans
- Secondary (Intermediate)Host: None
- Habitat: Small intestine
- Disease: Ascariasis
- Drugs Used for Treatment: Albendazole, Mebendazole
Causative Agent: Ancylostoma duodenale
- Primary (Definitive) Host: Humans
- Secondary (Intermediate) Host: None
- Habitat: Small intestine
- Disease: Hookworm infection
- Drugs Used for Treatment: Albendazole, Mebendazole
Causative Agent: Wuchereria bancrofti
- Primary (Definitive) Host: Humans
- Secondary (Intermediate) Host: Mosquitoes (Culex, Aedes, Anopheles spp.)
- Habitat: Lymphatic system
- Disease: Filariasis or Elephantiasis
- Vector/Carrier: Mosquito
- Drugs Used for Treatment: Diethylcarbamazine (DEC), Ivermectin, Albendazole
Causative Agent: Trichinella spiralis
- Primary (Definitive) Host: Humans
- Secondary (Intermediate) Host: Various mammals (pigs, wild boars)
- Habitat: Muscle tissue
- Disease: Trichinosis
- Drugs Used for Treatment: Albendazole, Mebendazole
Causative Agent: Brugia malayi
- Primary (Definitive) Host: Humans
- Secondary (Intermediate) Host: Mosquitoes (Mansonia, Aedes spp.)
- Habitat: Lymphatic system
- Disease: Lymphatic filariasis
- Vector/Carrier: Mosquitoes
- Drugs Used for Treatment: Diethylcarbamazine (DEC), Ivermectin, Albendazole
Parasitic Agents: Arthropods
Soft Tick (Ornithodoros spp.)
- Primary (Definitive)Host: Various mammals (including humans)
- Secondary Host: None
- Habitat: Rodent burrows, nests, crevices
- Disease: Tick-borne relapsing fever
- Control Measures: Environmental control (cleaning and sealing rodent burrows), acaricides, personal protective measures
Hard Tick (Ixodes spp.)
- Primary Host: Various mammals (including humans, deer, mice)
- Secondary Host: None (multiple host cycle: larva, nymph, adult stages feed on different hosts)
- Habitat: Forested areas, grasslands
- Disease: Lyme disease
- Control Measures: Tick repellents, protective clothing, environmental management (removing leaf litter, controlling wildlife), acaricides
Mites (Sarcoptes scabiei)
- Primary Host: Humans
- Secondary Host: None
- Habitat: Human skin
- Disease: Scabies
- Control Measures: Topical scabicides (permethrin, ivermectin), washing clothing and bedding, treating close contacts
Lice (Pediculus humanus)
- Primary Host: Humans
- Secondary Host: None
- Habitat: Human scalp (head lice), clothing (body lice)
- Disease: Pediculosis
- Control Measures: Topical insecticides (permethrin, pyrethrin), regular combing, washing clothing and bedding, maintaining personal hygiene
Flea (Xenopsylla cheopis)
- Primary Host: Rodents (rats)
- Secondary Host: Humans (accidental host)
- Habitat: Animal nests, human dwellings (especially where rodents are present)
- Disease: Plague, murine typhus
- Control Measures: Flea control on pets, rodent control, environmental sanitation, insecticides
Bug (Cimex lectularius)
- Primary Host: Humans
- Secondary Host: None
- Habitat: Human dwellings (mattresses, furniture)
- Disease: No direct diseases, but cause allergic reactions and secondary infections from scratching
- Control Measures: Regular cleaning, heat treatment, insecticides, encasing mattresses and pillows, professional pest control services.
Parasitic Vertebrates:
Cookiecutter Shark (Isistius brasiliensis)
- Habitat: Warm temperate ocean basins
- Prey (Host) : Cetaceans, pinnipeds, sharks, and bony fishes.
- Feeding: Feed on body parts of preys.
Hood Mockingbird (Mimus macdonaldi)
- Habitat: Espanola island
- Prey (Host): Sea birds, humans
- Feeding: Eggs, dead animals
Vampire Bat (Desmodus rotundus, Diphylla ecaudata, Diaemus youngi)
- Habitat: South and Central America ( dark caves)
- Prey (Host): Mammals
- Feeding: Blood (Hematophagy)