Taenia & Echinococcus Parasites

Taenia saginata vs. Taenia solium

• Taenia solium's intermediate host is the pig, while Taenia saginata's is cattle.
• Transmission of Taenia solium occurs through ingesting raw pork meat containing Cysticercus cellulose.
• Transmission of Taenia saginata occurs through ingesting raw beef containing Cysticercus bovis.
• The infective stage for both Taenia solium and Taenia saginata is Cysticercus cellulosa and Cysticercus bovis respectively.

Cysticercosis

• This is the invasion of human tissue by the larva stage of T. solium (cysticercus cellulosa).
• Infection Modes:
  • Consumption of T. solium eggs in food or drink.
  • External auto infection
  • Internal auto infection.

Echinococcus granulosus

• The definitive host of this parasite is the Dog.
• The intermediate host is typically Sheep, but can also be humans (accidentally).
• Infection occurs through consuming food or drink contaminated with eggs.
• Playing or kissing with an infected dog is another way of contracting the parasite.

Hymenolepis nana

• The infective stage is the ingestion of H. nana egg.
• Transmission occurs through consuming food or water contaminated with eggs.
• External auto infection (hand to mouth) and internal auto infection can occur when eggs are released in the intestinal hatch itself.
• Accidental ingestion of rat flea (I.H) leads to cysticercoid larva

Parasites Transmitted by Autoinfection

• Enterobius vermicularis:
  • Habitat: Large intestine (colon, cecum)
  • Infective stage: mature egg
• Strongyloides stercoralis:
  • Habitat: Small intestine
  • Infective stage: Filariform larva
• Hymenolepis nana:
  • Habitat: Small intestine (ileum)
  • Infective stage: Embryonated egg

Types of Females of Nematodes

• Oviparous: lay unsegmented eggs; for example, Ascaris, Trichuris, Ancylostoma, Necator, and Enterobius.
• Ovoviviparous: lay eggs containing fully formed larvae that hatch immediately; for example, Strongyloides.
• Viviparous: Produce larvae; for example, Dracunculus, Trichinella, Wuchereria, and Brugia.

Small Intestinal Nematodes

• Ascaris lumbricoides: Transmitted through ingesting embryonated eggs, children playing in soil containing egg
• Strongyloides stercoralis: Transmitted through skin penetration by filariform larva

Large Intestinal Nematodes

• Trichuris trichiura: Transmitted through ingesting embryonated eggs
• Enterobius vermicularis: Transmitted through ingestion of eggs from contaminated sources (hands, food, drink, clothes, or bed sheets) or via external autoinfection.

Parasites Causing Loeffler's Syndrome

• Ascaris lumbricoides: Transmitted through ingesting embryonated eggs from soil.
• Strongyloides stercoralis: Transmitted through skin penetration by filariform larva.
• Ancylostoma duodenale: Transmitted through skin penetration by filariform larvae.

Parasites Causing Specific Medical Conditions

Intestinal Obstruction

• Parasite: Ascaris lumbricoides
• Habitat: Small intestine
• Mode of infection: Ingestion of embryonated eggs from contaminated food or water

Iron Deficiency Anemia

• Parasite: Ancylostoma duodenale (Hookworm)
• Habitat: Small intestine
• Mode of infection: Skin penetration by 3rd stage Filariform larva from contaminated soil

Pruritis Ani

• Parasite: Enterobius vermicularis (Pinworm)
• Habitat: Large intestine
• Mode of infection:
  • Ingestion of eggs from contaminated sources, external autoinfection, retroinfection.
  • Airborne transmission via polluted eggs in dust.

Electrolyte Imbalance

• Parasite: Capillaria philippinesis
• Habitat: Small intestine (jejunum)
• Mode of infection: Ingestion of undercooked fish containing infective larvae

Elephantiasis

• Parasite: Wuchereria bancrofti
• Habitat: Adult in lymphatic vessels and nodes in abdominal or inguinal region
• Mode of infection: Bite of Culex mosquito carrying 3rd stage filariform larvae

Calabar Swelling

• Parasite: Loa loa
• Habitat: Subcutaneous tissues of eye
• Mode of infection: Bite of Chrysops fly (deer fly) carrying third stag larvae

River Blindness

• Parasite: Onchocerca volvulus
• Habitat: Adult in subcutaneous tissue
• Mode of infection: Bite of blackfly (Simulium)

Dysentery

• Parasite: Entamoeba histolytica
• Habitat: Large intestine (cecum)
• Mode of infection: Ingestion of mature cyst in food, drink, or from contaminated hand

Steatorrhea

• Parasite: Giardia lamblia
• Habitat: Small intestine (duodenum)
• Mode of infection: Ingestion of cysts in contaminated water or food

Skin Ulcer

• Parasite: Leishmania tropica
• Habitat: Skin (macrophages in dermis)
• Mode of infection: Bite of infected sandfly (Phlebotomus)

Kala Azar

• Parasite: Leishmania donovani
• Habitat: Reticuloendothelial system (liver, spleen, bone marrow)
• Mode of infection:
  • Bite of sand fly or Congenital transmission from mother to fetus
  • Blood transfusion

Chronic Sleeping Sickness

• Parasite: Trypanosoma brucei gambiense
• Habitat: Blood, lymph, and later cerebrospinal fluid (CNS)
• Mode of infection: Bite by infection testse fly Conjential transmission and Blood transfusion

Hemolytic Anemia

• Parasite: Plasmodium falciparum (or any Plasmodium species)
• Habitat: Liver cell and RBC
• Mode of infection:
  • Bite of infected Anopheles mosquito
  • Blood transfusion
  • Congenital

Lymphadenopathy

• Parasite: Toxoplasma gondii
• Habitat: Intracellular (muscle, Brain)
• Mode of infection:
  • Ingestion of sporulated oocyte in food or water with cat feces
  • Eating uncooked meat containing (tissue cyst, Bradyzoite)
  • Congenital toxoplasmosis (Tachyzoite)
  • Blood transfusion (Tackzoite)
  • Organ transplantation (tissue cyst, Bradyzoite)

Parasites Transmitted by Skin Penetration

• Strongyloides Stercoralis:
  • Habitat: Small intestine (Duodenum and Jejunum)
  • Infective stage: 3rd Stage of Flariform larvae
• Ancylostoma:
  • Habitat: Small intestine
  • Infective stage: 3rd stage filariform larva

Parasites Transmitted by Eating Undercooked Pork

• Taenia solium:
  • Habitat: Jejunum of the small intestine
  • Infective stage: Cysticercus cellulosae
• Toxoplasma Gondii:
  • Habitat: Intestinal cells (in cats), tissue (in humans)
  • Infective stage: Tissue cysts or oocysts

Locomotor Structures in Protozoa

• Pseudopodium: Extension of ectoplasm followed by endoplasmic (entameba histolytica trophozoite)
• Cilia: Numerous short hair-like threads covering the surface (Balantidium coli)
• Flagellum: Long whip-like structure found on the cell surface (Trypanosoma)
• Gliding and twisting: Movement propagated through the myonemes (plasmodium spp)

Types of Reproduction in Protozoa

Asexual Reproduction

• Binary fission: Flagellates, Ciliates, Entamoeba
• Multiple fission: Plasmodium in man
• Budding: Toxoplasma gondii

Sexual Reproduction

• Gametogony: Plasmodium in female Anopheles
• Conjugation: Balantidium coli

Medical Importance of Arthropods

Cause a disease by adults:

• Transmission of allergenic or poisonous subs through their bites * Ticks and Scorpions
• Invasion of skin causing cutaneous manifestations scabie mites
• Annoyance of domestic animals

Cause a disease by larvae

• Invade different tissue of animals or man causing Myiasis *larvae of some dipterous flies

Transmit a disease

• By inoculation of a pathogen into the bite wound * Glossina in Trypanosoma
• By contamination of bite wound with insect feces containing Pathogen winged bugs in Trypanosoma Cruzi
• By crushing of infected arthropod on skin

Mechanical and Biological Transmission of Diseases by Arthropods

Mechanical

• Contaminating different parts by stool
• House flies and Entamoeba histolytica cysts or passive carrier by their wet proboscis
• stable flies and blood parasites

Biological

• Propagative organisms: Multiplies without development all arthropod-borne bacterial, rickettsial and viral disease as fleas in plague
• Cyclodevelopmental
  • Parasites develop without multiplication all helminth Parasite transmitted by arthropods as mosquitos in filarial worms
• Cyclopropagative
  • The causative organism undergoes multiplication and development (malaria)
• Transovarian
  • Parasites are transmitted to the offspring's through the eggs e.g. tick-borne diseases especially in one host tick as in babesiosis
• Trans-stadial (stage to stage)
  • Parasites transmitted from the infected larvae to nymph to adult's e.g. Dipylidium caninum

Metamorphosis in Arthropods

Complete Metamorphosis (Holometabola)

• Egg → Larva → Pupa → Adult
• Larvae and pupa are completely different in morphology, habitat, feeding habits than adult.
• Example: mosquitoes.

Incomplete Metamorphosis (Hemimetabola)

• Egg → Nymph → adult
• Nymph is similar to the adult but smaller in size, paler in color, sexually immature, similar in feeding habits to adult
• Example: bugs and lice

Medical Importance of Fleas

As vector of diseases:

• Plague: Established in rats with transmission to humans via rat and human fleas (Pulex irritans).
• Endemic or murine typhus: Causative organism is Rickettsia mooseri.

As an intermediate host of parasitic diseases:

• Rat fleas act as I.H. for H. nana & H. diminuta
• Dog and cat fleas act as I.H. for D. caninum

Tunga penetrans:

• Female penetrates skin between toes/fingers, sole of feet (chigger/jigger disease).

Medical Importance of Lice

• Bites of adults/nymphs cause severe itching and dermatitis. Scratching worsens inflammation and may cause secondary bacterial infection.
• Prolonged/severe infestation with body lice: Darkening and thickening of skin (vagabond's disease)
• Vectors of:
  • Epidemic (louse-born) typhus, caused by Rickettsia prowazekii, and mainly transmitted by Pdiculus humanus.
  • Trench fever, caused by Quintana, transmitted by the bite of the louse or by contamination of the abraded skin.
  • Relapsing fever, caused by Borrelia recurrentis.

Medical Importance of Mosquitoes

• Anopheles: Transmit malaria.
• Culex: Transmit "Bancroft's filariasis" and encephalitis.
• Aedes: Transmit yellow fever and Dengue fever

Medical Importance of Simulium

• Transmit Onchocerca volvulus → River blindness
• Painful bite → itching, fever, nausea, headache
• May cause Black fly fever

Medical Importance of Sand Fly

• Leishmaniasis caused by leishmania donovani, L.tropice ( Phlebotomous ) and L. Braziliensis ( Lutzomyia)
• Sand Fly fever

Medical Importance of Musca domestica

Disease transmission:

• Transmits microorganisms to our food or body directly, mechanically
• Bacteria: Vibrio cholera, Streptococci, Shigella, Salmonella, Escherchia coli
• Protozoa: E. histolytica cysts, Giardia cysts, Balantidium cysts.
• Helminth eggs: As Taenia, Ascaris, Trichuris, Oxyuris, and Hymenolepis nana

Disease causation:

• Larvae of flies may cause myiasis

Medical Importance of Glossina palpalis & Glossina morsitans

• G. palpalis: vector of Gambian (chronic) sleeping sickness
• G. morsitans: vector of Rhodesian (acute) sleeping sickness

Medical Importance of Cyclops

• Intermediate host for:
  • Diphyllobothrium latum
  • Diphyllobothrium mansoni
  • Dracanculus medinensi

Parasites Transmitted by Blood Transfusion

• Leishmani donovina
• Toxoplasm
• Trypanosoma cruzi
• T. Gambiense
• T. Rhodesiense
• Plamodium vivax
• P. Malaria
• P. Ovale
• P. Falciparum