Helminths Flashcards
Foodborne trematode (Fluke) lifecycle
- Eggs released in faeces
- Miracidia hatch and enter snail
- In snail Miracidia become sporocysts
- In snail - Sporocysts –> Rediae –> Cercariae
- Cercariae swim from snail and encyst on intermediate host
- Cercariae become metacercarie and are ingested by host
- Become adults in gut and migrate to specific organ to lay eggs (hemaphroditic reproduction)
Adult trematode body parts
Leaf shaped
Tegument cover
oral sucker
ventral sucker
blind ending gut
reproductive organ.
Name of liver flukes
Fasciola - hepatica/gigantica
Opisthorchis
Clonorchis - liver/biliary
Name of lung fluke
Paragonimus
Name of gut fluke
Fasciolopsis
Which trematodes have pathogenic eggs?
Schistosomiasis only
Food associated with each foodborne trematode
Fasciola - Aquatic vegetables/ contaminated water
Opisthorchis/Clonorchis - Fish
Paragonimus - Crustaceans
Fasciolopsis - Aquatic vegetables
Fasciola egg description
Egg: 120-150 um
Oval, yellow, operculum.
Fasciola snail
lymnaea truncatula
Opisthorchis egg description
Egg: 27-30um
Yellow, flask shaped, operculum with shoulders
Opisthorchis snail
Bithynia
Symptoms of foodborne trematode infection
Eosinophilia
GI symptoms
Urticaria
Fever
Hepatomegaly and abdominal pain
Weight loss/ malnutrition
Chronic → clinical syndrome from biliary obstruction → RUQ pain, nausea, jaundice.
Cholangiocarcinoma - more common in Opisthorchis/Clonorchis
Extra-heaptic infection → brain, lungs, heart, skin, gut.
Treatment for Trematode infections (including Schistosomiasis)
Praziquantel
(except Fasciola –> give Triclabendazole)
Paragonimus egg description
Egg - 70-95um. Yellow, operculum with shoulders. Unsegmented ovum and mass of yolk cells.
Paragonimus snail
Potodoma/ Semisulcospira
How to kill trematode eggs
cooking/ freezing
Temp >60, <20.
Schistosomiasis - leave water for 24hrs before use.
Schistosomiasis snails
Biomphalaria spp. - S. mansoni
Bulinus spp. - S. haematobium
Oncomelania spp. - S. japonicum (right)
Which sex is more significantly affected by Schistosomiasis and why
Females due to effect on gynecological system, PID and malignancies. Increased risk of catching HIV.
Method of Schistosomiasis innoculation
Any water contact
- via skin
- bathing
- drinking contaminated water
3 types of Schistosomiasis and their locations
S.masoni (GIT) - South America + Africa
S.haematobium (genitourinary) - Africa
S. Japanicum (GIT) - Japan/Asia
How does Schistosomiasis cause disease?
Eggs are potents toxins which stimulate immune reaction and fibrosis. Lead to organ failures, micro-perforations and malignancy
Schistosomiasis lifecycle
- Egg released in faeces (and urine in haematobium and japanicum)
- Eggs hatch in water releasing miracidia which enters snail
- In snail Sporocysts –>Cercariae
- Cercariae swim and penetrate human
- Become Schistosomulae in human and enter bloodstream
- Mature into adults in liver
- Adult worms migrate to venules of bowel/genitourinary tract and lay eggs (sexual reproduction).
Schistosomiasis lifespan
60 years
Early Schistosomiasis symptoms
Cercarial dermatitis “Swimmers itch”
- Acute papular disease
- Occurs from cercariae penetration from skin
- Praziquantel not effective at this stage
Acute schistosomiasis - Katayama fever
- 2-4 weeks post exposure. A serum sickness type illness
- Urticaia, cough, abdo pain, fever.
- Need to treat with Praziquantel twice
S. Haematobium signs/symptoms
Haematuria/ Haematospermia
obstructive uropathy
Increased risk of bladder cancer SCC
Cervical inflammation and cysts/papules
Vaginal bleeding/dyspaeunia
Subfertility and infertility
pulmonary granuloma
S. mansoni signs/symptoms
Bowel changes
Bacteremia
Malignancies
portal hypertension
hepatosplenomegaly
Anaemia
Management of CNS Schistosomiasis
praziquantel and steroids
Population management of Schistosomiasis
- population chemotherapy
- snail control (expensive, toxic)
- water and sanitation (difficult to implement – no def/urine in water).
WHO recommends in endemic countries (>10%) get annual preventative chemo from the age of 2. If the prevalence does not go down, you treat twice yearly. If the prevalence is reduced you can start to switch to a test and treat base.
→ praziquantel: very short half-life. Only adult worms are praziquantel sensitive.
Schistosomiasis diagnostic techniques
Bladder US - characteristic appearance
Stool OCP
Urine filtration + concentration
Serology
Antigen testing - highly specific
Rectal biopsy for eggs
S. Haematobium egg description
100 - 170um with terminal spine
S. Mansoni egg description
100 - 170um with lateral spine
Cestode anatomy
Head (Scolex) - with 4 suckers and Rostellum (line of hooks)
Body segements (Proglottids) in a chain (Strobila) - with last proglottid containing the eggs
Excretory canal
Haemaphroditic reproductive organs
Cestode lifecycle
Proglottids containing eggs
Eggs released in faeces
Ingested by intermediate host
Eggs change into onchospheres
Develops into metacestode in muscle (juvenile) (called cysterceri in taenia and plerocercoid in diphyllobothrium)
Metacestode consumed by definitive host
Metacestode matures to adult in intestine
Cyclophyllidea egg description (pork/beef/dwarf/hydatid tapeworms)
40um size. Round onchosphere containing hooks. Gelatinous outer ring with middle ring called an embryophore.
Difference between Taenia Solium and Taenia Saginata adult tape worms
Solium - more defined head, less uterine branches <15
Saginata - less defined head, more uterine branches 15-30
What organism causes Cysticercosis
The juvenile stage of Taenia Soilum (Pork Tapeworm)
Cysticercosis symptoms
Seizure
Headaches
Visual disturbance
Confusion
Focal neurology
Cysticercosis imaging
rice grain calcification in thighs
hole punch brain (invaginated scolex creating a target shape is diagnostic)
Neurocysticercosis treatment
Albendazole + Dexamethasone.
Add praziquantel in high helminth load.
Dexamethasone alone if raised ICP
Treatment/ Preventative Chemotherapy for Taenia
Praziquentel
Albendazole
Niclosamide
Taenia egg description
Round, 33 to 43 μm with a thick radially striated dark brown wall.
Inside each shell is an embryonated oncosphere with 3 pairs of hooks.
Diagnostics for Taenia
Faecal OCP
Kato-Katz
Less used: PCR, Serology
Intermediate hosts for Diphyllobothrium
Copepod and Fish
(Note usually only single worm infection in human)
Treatment for Diphyllobothrium
Praziquentel
Niclosamide
Description of Diphyllobothrium egg
The egg is pale yellow
-brown and oval in shape, it measures about 65-70 μm.
There is an operculum at one end which can be difficult to see.
The egg contains a mass of granulated yolk cells surrounding an undeveloped ovum
Which Cestode does not require intermediate host
Dwarf Tapeworm (Hymenolepis nana) - However rodents can also be a host
Treatment for Dwarf Tapeworm (Hymenolepis nana)
Praziquantel
Which Cestode is common in children
Dwarf Tapeworm (Hymenolepis nana)
Description of Hymenolepis nana egg
Fried egg appearance with of hooks in the central oncosphere
and polar filaments within the space between the oncosphere and outer shell.
Definitive host for Echinococcus (Hydatid)
Fox (multilocularis) and Dog (granulosus) (Humans are a dead-end accidental host)
Hydatid symtpoms
Cysts form wherever eggs become stuck
Mainly large liver lesions. Hepatosplenomegaly.
Cysts form daughter cysts within - tumor like growth.
Pulmonary cysts (In multilocularis)
Can have fever, pain, coughing up salty liquid/haemoptysis.
Collapsed cyst have ‘water lily’ appearance on imaging.
Hydatid treatment
Albendazole, Mebendazole
Praziquantel (first choice in dogs).
Surgical / PAIR.
Hydatid subtypes
multilocularis (liver + pulmonary)
granulosus (liver)
Echinococcus (Hydatid) egg description
round/oval shaped with thick wall and central onchosphere.
Nematode anatomy
Cylindrical with a body cavity
Full GIT with anus
Lips
Teeth
Filariaeform extremeties
Vector for Geohelminths
No vector
Peak age of Trichuris infection
5-10 yr olds
Peak age of Ascaris infection
5-10 yr olds
Peak age of hookworm infection
> 30yrs old
Ascaris life cycle
- Eggs ingested
- Larvae hatch and move from small intestine –> liver –> heart –> lungs –> swallowed in saliva –> small intestine
- Larvae mature into adults in small intestine
- Eggs pass in faeces
Ascaris CANNOT auto-infect –> eggs need to embryonate in soil
Symptoms of Ascaris infection
- Loefflers syndrome / Pulmonary eosinophillia - cause wheeze, dyspnoea and blood tinged sputum. Fluctuating infiltrates on CXR. Usually occurs in first infection.
- Abdominal symptoms - associated with heavy worm burden. Can get bowel obstruction.
- Malnutrition
- Moving abdominal mass that changes in size.
- Hepatobiliary and pancreatic obstruction/symptoms
- Vit A deficiency
Diagnostics for ascaris
- Kato Katz
- Stool OCP - need multiple
- PCR
What is the name if the eosinophillic lung disease caused by some Nematodes
Loefflers syndrome
(Ascaris and Hookworm as per their lifecycle)
Treatment for common Geohelminths
All albendazole except strongyloides
Ascaris - Albendazole (or Ivermectin)
Trichuris - Albendazole (or Ivermectin) - repeat twice
Hookworm - Albendazole (NO Ivermectin unless it is a non-human species)
Strongyloides - Ivermectin (or Albendazole)
Description of Ascaris Eggs
Fertile egg - oval in shape, brownish colour. 60
microns in length. Thick shell is rough/bumpy with dark staining
Decorticated egg - Occasionally the coat of the egg is not present and the egg instead has a thick smooth colourless shell.
Trichuris lifecycle
- Eggs ingested
- Larvae hatch in small intestine and mature into adults
- Eggs passed in faeces and embryonate in soil
Cannot auto-infect - eggs embryonate in soil
Mechanism of anaemia and GI damage in Trichuris
Head and neck burrows into intestines and releases enzymes - this dissolves that part of bowel which they then consume - can dissolve capillaries and cause anaemia.
Trichuris symptoms
Rectal prolapse
IBD type symptoms
Bloody dysentery
Eosinophilia
Trichuris egg description
light brown, lemon shaped, clear mucoid polar plugs at the end. 50um
Hookworm lifecycle
- Eggs passed out in faeces
- Larvae quest (wave about) on blades of grass
- Cutaneous entrance into human (very itchy)
- bloodstream –> heart –> lungs –> sputum swallowed –> small intestine
- Larvae mature into adults in small intesting
Hookworm symptoms
Itch + cutaneous larva migrans
Enteritis/ Abdominal pain
Eosinophillia
Anaemia, hypoproteinemia
Loeffers syndome/ pulmonary disease.
Hookworm egg description
57 to 76 μm. Oval or ellipsoidal shape. Morulated appearance
Thin shell.
Enterobius lifecycle
- Eggs ingested then hatch in small intestine
- Larve move to large bowel then mature into adults
- Adults lay eggs in perianum. Eggs also embryonate here
Can auto-infect
Enterobius diagnostics
Peri-anal swab
Anal adhesive tape
Enterobius egg description
Oval in shape, colourless with a clear shell and are slightly flattened on one side, eggs are about 55microns in length.
Strongyloides lifecycle
Only females are parasitic - Could live their whole lives as a free living worm.
- Eggs hatch in soil –> Larve penetrate skin
- Blood –> lungs –> sputum –> intestine
- Larvae pass out in intestine or penetrate into bloodstream to auto infect
Adult only lives in soil - not found in human.
Asexual reproduction of larvae in body, sexual reproduction in soil.
Disease which increases the risk of high burden Strongyloides infection
HTLV-1 –> due to TH2 pathology
Alcoholics
Malnutrition
High dose steroids
Strongyloidiasis symptoms
Intensely itchy migratory paths - larvae currens
Sporadic diarrhoea, weight loss, abdo pain.
Pulmonary symptoms rare
Eosinophillia
Strongyloides diagnostics
Multiple methods required due to poor diagnostics
Faeces (multiple techniques - formalin, baermann, koga agar, charcoal) sensitivity <50%
Sputum
Duodenal fluid
Larvae on mucosal biopsy
Serology - high false positives, false neg in immunocomprimised
Fluctuating infiltrates on CXR
Strongyloides CXR findings
fluctuating infiltrates
Strongyloides faecal findings
Nothing!
Larvae not seen unless specimen is fresh
Eggs not seen
Coiled larvae in muscle
Trichinella
Cause of Ocular Larva Migrans
Toxocara
- Human is wrong host. Dies in human body
Strongyloides hyperinfection syndrome symptoms
Asthma like syndrome
Liver/biliary obstruction
Endocarditis and Endomyocardial fibrosis
Renal disease
CNS disease
Types of Filarial Nematodes
Lymphatic filariasis - Wuchereria Bancrofti, Brugia Malayi, Brugia Timori
Mansonella Species
Onchocerca (river blindness)
Loa Loa (Eye worm)
Dracunculus (Guinea worm)
Symptoms of Lymphatic filariasis
Develop lymphadenopathy, lymphoedema, lymphangitis and elephantitis
Acute dermatolymphangioadenitis (secondary bacterial infection)
Genital lymphoedema (chyluria, hydrocele, epididymitis, orchitis)
Chylous diarrhoea
Tropical pulmonary eosinophillia
Lymphatic filariasis diagnostics
Thick blood smear
Concentration techniques
Membrane filtration
Staining techniques - identifies which species
CFA antigen detection
Brugia rapid dipstick
IgG4 test
Ultrasound of lymphatics
Management and Treatment of lymphatic filariasis
Exercise, Elevation and inversion of hydroceles.
Triple therapy - Di-ethyl-Carbamazine (DEC) + Ivermectin + Albendazole.
EXCEPTION - Avoid DEC in Onchocerciasis or Loa Loa co-infection (in which case they should be treated first with doxy, or give regimen without DEC)
Issues with Di-ethyl-Carbamazine (DEC) and Ivermectin in Filariasis
In onchocerciasis DEC can cause Mazotti reaction (sepsis like picture with swelling and urticaria) and eye damage
In Loa loa DEC and ivermectin can cause fatal encephalopathy
Issue with CFA test for lymphatic filariasis
Highly cross reactive with Loa Loa
Wuchereria Bancrofti mosquito vector
Anopheles (Africa)
Culex (S. America, Asia)
Aedes (Asia, Pacific)
Brugia Malayi mosquito vector
Mansonia, Anopheles, Aedes
Lymphatic filariasis larvae appearance (and how to tell each species apart)
Wuchereria Bancrofti - long empty sheath at tail, pink stained sheath
Brugia Malayi - kinked with 2 nuclei at tip, clear sheath
Mansonella - small and unsheathed
Loa loa - nuclei to top, kinked
Oncho - only found in skin snip
Mansonella life cycle
- Bite by Culicoides (Biting Midge fly) and larvae enter
- Adults live in peritoneal or pleural cavity –> release microfilariae into blood stream
- midge takes blood meal –> Larvae mature L1 –> L3
Mansonella larve appearance
small and unsheathed
Onchocerciasis Vector
Black fly (Simulium)
Onchocerciasis lifecycle
- Black fly takes blood meal - L3 larve enter
- Adult migrates to subcutaneous tissue and lymphnodes to live
- Release microfilariae to skin, lymph, tissue, blood, urine, sputum.
- Black fly takes blood meal - larvae mature L1 –> L3
Symptoms of Onchocerciasis
- Ochodermatitis - itchy nodules from microfilariae
- Highly pruritic
- Depigmentation
- Lizard skin - Blindness from microfilariae in eye (occurs due to wolbachia secretion)
- Sclerosing keratitis
- Optic neuritis and optic atrophy - CNS
- nodding syndrome
- hypopituitary
Onchocerciasis diagnostics
Skin smear/ skin snip (must be bloodless to ensure you are not finding the lymphatic type)
DEC patch test
Rapid diagnostic test
Serology
Onchocerciasis treatment
Doxycycline for 6 weeks followed by Ivermectin STAT (If Loa loa co-infection avoid Ivermectin)
Ivermectin also used as population control measure
Loa Loa distrubution
Only found in Central Africa
Loa Loa vector
Deer fly (lives in forest canopy)
Loa loa lifecycle
- Blood meal by Deer fly –> larvae enter
- Adults live in subcut tissue
- Adults produce microfilariae which spread to all fluids (blood, urine, CSF, sputum)
- Fly takes blood meal, larvae mature L1–>L3
Loa Loa Symptoms
Highly pruritic
Seen migrating across eye
Calabar swelling - transient migrating angioedema
Rare renal, cardiac and neuro pathology
Proteinuria and haematuria
Endomyocardial fibrosis
Meningoencephalitis
Hypereosinophilia
Loa loa diagnostics
Thick film microscopy
Loa Loa treatment
If <2000 microfilaria - DEC for 3 weeks
If 2000-8000 microfilaria - Ivermectin STAT then again in 1-3 months - then treat with DEC once microfilaria <2000 (beware risk of encephalopathy)
If >8000 microfilaria - Albendazole for 3 weeks then Ivermectin STAT - then treat with DEC once microfilaria <2000 (beware risk of encephalopathy)
Loa Loa larvae description
sheathed and the nuclei extends to the tip of the tail, which is often bent to one side.
Dracunculus (Guinea worm) lifecycle
- Human drinks water containing copepods
- Larvae released when copepods die in the stomach. Larvae mature into adults in the stomach.
- Female migrates to skin and discharges larvae through the skin via making a hole
- Larve consumed by copepod and matures
(Dog is also a host)
Treatment/Diagnostics for Dracunculus (Guinea worm)
None!
Can manually extract female from the blister (submerge in water)
What bacteria is symbiotic with filaria?
Wolbachia - is required by filaria to reproduce
Concentration method for filariasis
Thick blood film
Membrane filtration
Knotts concentration - centrifuge blood + water
Faecal concentration methods
- direct wet mount
- floatation technique (high specific gravity solution)
- Kato Katz (for schistosomiasis)
- sedimentation technique (low specific gravity solution)
concentration technique for enterobius
sellotape on anus
strongyloidiasis filtration techniques
Faecal charcoal
Agar plate
Filter paper
Terms for different helminths and ova
All eggs are called ova
Trematodes (flukes) - larval forms are miracidia/cercariae
foodborne termatodes ova have operculum.
Cestodes (land) - eggs are oncoshperes. larval form is cyctercerci.
Cestodes (water) - eggs are granulated yolk cells, has an operculum, larvae are coracidia
Nematodes - larval form is filariae
Which ova are embryonated in faecal sample?
Enterobius
Opisthorchis
