Parasitology Lab 2 Flashcards
W bancrofti & Brugia Life cycle (human)
Mosquito takes a blood meal, L3 larvae enter skin. Over 3 months larvae mature to adult worms in lymphatics. Adults live 6-8y, produce sheathed microfilariae that migrate into lymph and blood channels. Mosquito ingests microfilariae on blood meal.
W bancrofti & Brugia Life cycle (mosquito)
Mosquito takes a blood meal ingesting microfilariae. Mf shed sheaths, penetrate mosquito’s midgut and migrate to thoracic muscles. Mature from L1 to L3 larvae over 10d. L3 larvae migrate to head and mosquito’s proboscis. Mosquito takes a blood meal injecting L3 larvae into skin.
Lymphatic filariasis Adult worm
Double uterus
Lymphatic filariasis Mf: Wuchereria vs Brugia
Both sheathed, look at the tail (pointy) end of the larvae (not end of sheath)- Wuchereria nuclei are not present in the tail. Brugia has a gap, then one, then a gap, then one more final nuclei - two nuclei in the end of the tail - remember: Brugia - B is 2nd letter - there are two nuclei at the end of the tail. Loa loa - the nuclei go lower and lower into the bottom of the tail
Onchocerca Life cycle (human)
Simulium fly takes a blood meal injecting L3 larvae into the bite wound. L3 penetrate subcutaneous tissues and create subcutaneous nodules where adult male and female reside. Adults produce unsheathed microfilariae that typically are found in skin and lymphatics of connective tissues, but also occasionally in peripheral blood, urine and sputum. Simulium fly takes a blood meal ingesting microfilariae
Onchocerca Life cycle (Simulium)
Simulium fly takes a blood meal ingesting microfilariae. Mf penetrate fly’s midgut and migrate to thoracic muscles where they mature (~10d) from L1 to L3 larvae which migrate to head and proboscis. Simulium fly takes a blood meal injecting L3 larvae into bite wound
Onchocerca Adult worm
Within subcutaneous nodules, double uterus
Onchocerca Microfilaria
no sheath, tail free of nuclei, (Mansonella spp smaller with nuclei to tip of tail)
Loa loa Life cycle (human)
Chrysops takes a blood meal, L3 larvae enter bite wound. Mature and migrate in subcutaneous tissue. Adults produce sheathed microfilariae that are found in spinal fluid, urine, sputum, peripheral blood and in the lungs (adults live up to 20y, Mf live up to 1y). Chrysops takes a blood meal and ingests microfilariae
Loa loa Life cycle (Chrysops)
Chrysops takes a blood meal and ingests microfilariae. Mf shed sheath, penetrate midgut and migrate to thoracic muscles. Mature to L1 to L3 larvae, migrate to head and proboscis. Chrysops takes a blood meal and L3 larvae enter bite wound
Loa loa Adult worm
Female 40-70mm long, exterior cuticle lacks ridging
Loa loa Microfilaria
Ghost sheath on Giemsa, flattened nuclei go to tip of tail
Microfilaria Sheathed
Wb empty tail, Bm two termina nuclei, Loa loa tail full of nuclei
Microfilaria Unsheathed
Onchocerca, Mansonella
Microfilaria Blood
Wb, Bm, Loa, Mansonella spp
Microfilaria Tissue
Onchocerca, Ms, Mo
Microfilaria Mosquito vector
W bancrofti, B malayi
Microfilaria Simulian black fly vector
Onchocerca volvulus
Microfilaria Deerfly vector
Loa loa
Microfilaria Culicoides midges & Simulium blackflies vector
Mansonella spp
Lymphatic filariasis Vector
Culex, Mansonia, Anopheles, Aedes. Mosquitoes of various genera pick up Mf larvae (L1) with blood meals, the larvae develop to L3 inside mosquito and can then find their way into a new host after being deposited in the skin during blood feeding. Mating occurs between adult male and female worms lodged in the lymphatic system and millions of Mf are produced. Symptoms of LF predominantly results from the presence of adult worms residing in the lymphatics.
Onchocerca Vector
Simulium fly - most commonly S damnosum. Bites outdoors in daytime, only females bite, painful bite. Short mouth piece does not bite through clothes. Breeds in fast-flowing rivers. ‘White water’ = well oxygenated
Loa loa Vector
Chrysops spp ‘Mango fly’ ‘Deer fly’ - day biting
Diphyllobothrium Adult worms
Yellowish, 3-10m (up to 25m), lives 5-15y. Absorb vit B12, cause deficiency -> pernicious anaemia. Scolex has two sucking grooves (bothrias), centrally located rosette shaped uterus
Diphyllobothrium Life cycle
Human ingests raw or undercooked fish -> larva develops to adult worm in small intestine, which then starts releasing eggs - eggs leave the body as unembryonated eggs. Embryonate and hatch in water (after ~12d) and release ciliated coracidia (swimming L1 larva) - consumed by copepod (1st intermediate host), larvae develop procercoid L2 larva. Copepod ingested by fish -> development of plerocercoid L3 larva
Diphyllobothrium Eggs
60um, shed in large numbers in faeces. Unembryonated (very granular), oval, does not float in salt solutions. Operculum at one end, Small knob at other end (abopercular knob). Not directly infective to humans.
Spirometra Life cycle
Human is accidental intermediate host and becomes infected from ingesting plerocercoid larva in fish, reptiles, amphibians. Unembryonated eggs passed in faeces of definitive host (dogs/cats) - eggs embryonate in water, coracidia hatch from eggs and are ingested by crustaceans -> procercoid larvae in body cavity of crustaceans -> infected crustacean ingested by second intermediate host (unembryonated > embryonated > coracidia > procercoid > plerocercoid)
Spirometra Human sparganosis
Normally acquired in three different ways: 1 Drinking contaminated water in which there is an infected cyclops 2 Eating raw or undercooked flesh (fish, frogs, turtle, snakes) containing spargana (plerocercoid larvae 3 By use of a poultice of raw infected flesh applied to skin, conjunctiva, or mucosa (traditional medicine in Asia). This allows the plerocercoid larvae in the infected flesh to crawl directly into human tissues. Raw frogs and snakes used in this way, or eaten, are the most likely reservoirs for spargana. Larvae are believed to be able to survive for up to 20y in humans.
Hymenolepsis nana Life cycle
Human ingest arthropod with cysticercoid stage, or ingest embryonated egg from contaminated food, water or hands. Within the intestine, onchosphere hatches, cysticercoid develops in intestinal villus , scolex attach in ileal portion of small intestine, eggs can be released through the genital atrium of the gravid proglottids -> embryonated eggs can be passed in faeces, or hatch in intestine causing autoinfection - hexacanth embryo penetrates intestinal villus and continues the cycle (egg > oncosphere hatches > cysticercoid > scolex > gravid worm releases eggs)
Hymenolepsis nana Adult worms
15-40mm (smallest tapeworm infecting humans), short lifespan but worms may be present in large numbers [1000s] and autoinfection). Scolex has a retractable rostellum with 20-30 hooks and 4 suckers. Worm is 100-200mm wide,
Hymenolepsis nana Eggs
40-60x30-50um. Slightly oval with two membranes - outer is thin and transparent
Taenia saginata Adult worms
Adult size usually 4-8m (up to 24m). Lifespan 10y. Small scolex <2mm 4 suckers with no hooks. Proglottids are characteristic - gravid uterus with >15 main branches, 1000-2000 proglottids/worm. Proglottids release 5-10 egg/day, 100,000 eggs/proglottid = up to 1 million eggs/day/worm!. Gravid proglottids may crawl out of anal orifice and oviposit on perianal skin.
Taenia saginata Life cycle
Human ingest undercooked muscle meat containing cysticercus. Scolex attaches to small intestine and develop as adult worm. Human release eggs and proglottids in faeces, cows ingest eggs from environment, larvae hatch in cow intestine, move out to muscle tissue where it forms cysts (cysticercus - contain larval stage - invaginated protoscolex) (protoscolex is invaginated, when it hatches, it evaginates from protoscolex to scolex. (egg > oncosphere > Cystcercus >hatch with scolex > tape worm >egg)
Taenia saginata Eggs
45um, thick striated shell, contains oncosphere. Only infective to cattle. Highly resistant to environment conditions. Eggs not infectious to humans but indistinguishable from T solium eggs.
T solium Adult worms
2-8m, adult worms live up to 25y. 800-900 proglottids, 50,000 eggs/proglottid. Gravid uterus <15 main branches
T solium Eggs
45um, thick striated shell, contain oncosphere with 6 hooklets. Infective to pigs and humans. Highly resistant to environment conditions. *Indistinguishable from T saginata eggs
Echinococcus granulosis Life cycle
Sheep ingest eggs from environment, oncosphere hatches, penetrates intestinal wall, migrates into tissues and develops hydatid cysts. Dogs scavenge on sheep infected with larval stage. Humans are accidentally infected by ingestion of eggs in dog faeces, will penetrate the stomach, and develop hydatid cysts in liver, lungs etc. (egg > oncosphere >hydatid cyst > [protoscolex in definitive host will attach to small intestine as scolex with adult worm]) - same life cycle for E multilocularis
Echinococcus granulosis Eggs
Not found in human faeces - ovoid in shape, resembles Taenia. Infective to human, cattle, sheep and other herbivores
Echinococcus granulosis Free hooks
Hook is diagnostic of hydatid cyst, even if one single hook is seen in an aspirate
Histopathology Liver
Malaria, Entamoeba histolytica, Ascaris lumbricoides (L3 larvae), Toxocara canis (granulomas & eosinophilic tracks), Leishmania, Echinococcus granulosus (protoscolices ‘hydatid sand’ or free hooks)
Histopathology Skin
Leishmania (intracellular amastigotes), Onchocerca volvulus (adult worm in subcutaneous tissue, Mf in dermis), Loa loa (adult worm migrate)
Histopathology Brain
Malaria, Toxoplasma (tachy or bradycyst), Acanthamoeba (cyst), Balamuthia (trophozoite), Trypanosoma brucei (Morula cells), Toxocara canis (granulomas & eosinophilic tracks), Angiostrongylus cantonensis (larvae in meninges, granuloma & necrosis), Taenia solium (neurocysticercus - invaginated protoscolex with hooks)
Histopathology Muscle
Cardiac (central nucleus): T cruzi. Skeletal (peripheral nucleus): Trichinella (nurse cell contains coiled L1 larva), Taenia solium (cysticercus - invaginated protoscolex with hooks)
Histopathology Lung
PCP, Ascaris lumbricoides (L3 larvae), Hookworm (L3 larvae), Toxocara canis (granulomas & eosinophilic tracks)
Histopathology Large intestine
Entamoeba histolytica (trophozoite, flask ulcer), Enterobius vermicularis (adult worm - lateral alae), Trichuris trichura (whip in villi, thick worm in lumen), Ascaris, Trichuris
Histopathology Small intestine
Trichuris trichura (whip in villi, thick worm in lumen), Hookworm (adult worm attaches to mucosa), Strongyloides stercoralis (adult female embedded in mucosa +/- submucosal damage), Capillaria philippensis (adult worm, severe inflammation), Anisakis (L3 and ulceration)
Histopathology Blood smears
Malaria (all stages), Trypanosoma brucei (trypanosome), Lymphatic filariasis (10pm-2am Wuchereria bancrofti, Brugia malayi), Loa loa (10am-2pm)
Histopathology Skin smears
Leishmania (amastigotes may be extracellular due to cell rupture during making smear), Onchocerca volvulus (Mf)
Histopathology CSF
Naegleria fowleri (trophozoite), Trypanosoma brucei (trypanosome)
Histopathology Spleen aspirate
Leishmania (intracellular amastigotes)
Histopathology Bone marrow aspirate
Leishmania (intracellular amastigotes)
Histopathology Eye
Toxocara canis (granulomas & eosinophilic tracks)
Histopathology Lymph vessel
Lymphatic filaria (adult worm Wuchereria bancrofti, Brugia malayi)
Definition Direct transmission
Passed directly from one infected host to another
Definition Indirect transmission
Transmitted via an intermediate host or vector - very common amongst parasites. Sometimes just mechanical transfer, but usually one or more essential life-cycle stages. The stage where the sexual stages of the life cycle take place is the definitive host - may or may not be the human
Definition Zoonosis
Any disease which can be transmitted to humans from animals
Definition Anthroponosis
A disease that is spread from humans to humans
Definition Trophozoite
Ill-defined term for the feeding, growing and dividing stage of a protozoan
Definition Cyst
1 In the tissue, a distinct walled off cavity containing multiple organisms, often important in transmission (eg Trichinella, Toxoplasma) or 2 a microscopic, resistant form, shed into the environment and responsible for transmission (eg Entamoeba)
Definition Koch’s postulates
1 The organism occurs in every case of the disease in question 2 the organism occurs in no other disease as a fortuitous and non-pathogenic organism and should not be found in healthy organisms. 3 Induce the disease anew when introduced into a healthy organism. 4 The organism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original, specific causative agent.
Definition 3 groups of parasitic helminths
Nematodes (round), Cestodes (tape-worms, Trematodes (flukes) - the last two comprise Platyhelminths
Definition Definitive host
The host harbouring the sexually mature adult worms
Definition Intermediate host
The host harbouring the larval stages
Giardia Trophozoite
Two nuclei, ventral disc, median bodies with axonemes, generally in stool will see cysts not trophozoites
