Helminths Flashcards
What is the classification of Ascaris Lumbricoides
Soil transmitted helminth
Nematode
What is the epidemiology of ascariasis
Children aged 3-8
800 million people affected
Associated with poor environmental hygiene
What is the lifecycle of Ascaris Lumbricoides
- Eggs from contaminated vegetables, water, soil are ingested
- Eggs hatch within the stomach and small intestine and release larva
- The LARVA migrate through the walls of the gut and cause acute ascariasis symptoms
- They migrate into the lymphatics and eventually reach the lungs (via liver —> heart) and are coughed up, swallowed and re-enter the digestive tract, where they develop into adults
- Female adults produce up to 200000 eggs per day
What are the clinical features of ascariasis?
Loefflers syndrome (usually lasts about 10 days)
Anaemia
Eosinophilia
Bowel obstruction
Biliary duct obstruction
Malnutrition and reduced vitamin A
How is ascariasis diagnosed?
Stool microscopy via Kato Katz
FLOATAC — stool centrifugación
CXR
Barium swallow
Eosinophilia
How is ascariasis managed?
Albendazole 400mg STAT
How is ascariasis prevented?
WASH
MDA of albendazole to school aged children
What are the two species of worm which cause Hookworm infections?
Necator americanus
Ancylostoma duodenale
What is the clsss of necator americanus and ancylostoma duodenale
Hookworms
Soil transmitted helminths
Nematodes
What is the epidemiology of Hookworm infections?
Causes 30-40% of maternal anaemia
Found globally
Adults > children (because associated with people who go out and work in fields with Night Soil
600 million people infected globally
What is the lifecycle of hookworms?
- Hookworm eggs are excreted in the stools of infected hosts
- The eggs hatch in warm soil and produce rhabditiform larvae
- Under the right condition rhabditiform larvae become filariaform
- Mature larvae enter into humans through the skin, either via cuts in the skin or through hair follicles
- The worms enter circulation in the lymphatics and venous circulation and travel to the liver — heart — lungs and are swallowed by the host
- When swallowed they travel to the small intestine where they mature into adults and attach themselves to the intestinal walls and feed off blood
- After 3-5 weeks the worms start to produce eggs
Who is most at risk of symptomatic hookworm infection?
Children
Pregnant women
People with underlying anaemia
What are the symptoms of hookworm infection?
- Asymptomatic
- ACUTE: Wakana syndrome, ground itch
- CHRONIC: IDA
How are hookworm infections diagnosed?
Eosinophilia
IDA
Stool microscopy +/- concentration methods
What is the management of hookworm infection?
Albendazole 400mg stat
+/- iron replacement
How is hookworm infection prevented?
Improved hygiene and sanitation
MDA of school aged children and childbearing aged women
Wear Shoes
Alternative fertilisers to Night Soil
What is the classification of whip worm?
Trichuris trichiura
STH
nematode
What is the epidemiology of whip worm?
600 million infections world wide
Warm humid climates
What is the lifecycle of trichuris?
- Eggs are ingested from contaminated food and water and soil
- Eggs pass through the stomach and are de-embryonated within the caecum where they burrow into the mucosa of the large bowel
- The worms feed on bowel juices, rather than blood
- After several weeks the female worm starts to produce eggs and releases several thousand eggs per day
What is the clinical presentation of Whip worm infection?
ASYMPTOMATIC
can occasionally cause symptoms of IBD in heavy worm burdens
Rectal prolapse in children
How is whip worm infection diagnosed?
Stool microscopy
Eosinophilia
How is trichuriasis managed?
Albendazole 400mg stat
How is whip worm infection prevented?
WASH
MDA women and children
What clinical sign is seen in toxocariasis?
Visceral larva migrans
How is visceral larval migrans managed?
Albendazole 400mg stat
What is strongyloides Stercoralis?
STH
nematode
What is the only STH that is capable of auto infection?
Strongyloides
What is the epidemiology of strongyloides?
Unknown.
Tropical climates»_space; but does occur almost worldwide
What are the complications of strongyloides?
Hyper infection secondary to immunosuppression, which can lead to death
What virus is associated with strongyloides?
HTLV-1
What is the lifecycle of strongyloides?
- Female worms, which are embedded in the mucosa of the small intestine, produce eggs, which soon hatch and release rhabditiform larvae
- Rhabditiform larvae can then become: - filariaform within the gut and reinfect by entering into the body at perianal mucosa -filariaform in good soil conditions, which then eventually infect people through the skin
- The worms then migrate through the skin into blood vessels and eventually travel to the lungs, are coughed up and swallowed, where they can then colonise the small intestine
- Due to auto infection people can have strongy infection for >40 years
What is the presentation of Strongyloides infection?
- asymptomatic
- Acute: irritation at infection site, loefflers syndrome, abdo pain and diarrhoea, weight loss
- Chronic: larva currens, diarrhoea, weight loss
What are the symptoms of hyper infection syndrome in strongyloides?
Severe and bloody diarrhoea
Bowel microperforations
Peritonitis
Gram negative septicaemia
Pulmonary exudates and hypoxia
Encephalitis and bacterial meningitis
How is strongyloides infection diagnosed?
Eosinophilia (**suspect strongy in any unknown cause High eosinophils)
Stool sample - notoriously difficult to find, even with concentration techniques
Charcoal stool culture
ELISA
how is strongyloides managed?
Ivermectin 200ug/kg per day for 2/7
** you need to kill the filarial worms, which is why you need to use ivermectin; its the same theory as ivermectin with Onchocerciasis and Lymphatic FIlariasis (also nematodes)
What are the 4 common tissue flukes?
Fasciola Hepatica
Opisthorchis Spp.
Clonorchis
Paragonimus Westermani
What is Fasciola Hepatic
A trematode (tissue fluke) which is spread through ingestion of metacercariae on Watercress
What is the epidemiology of Fascioliasis?
South American Andes and Bolivia
In these areas prevalence may be >90%
What is the lifecycle of Fasciola Hepatica?
- Eggs are excreted in host (often human) stool
- Miracidia hatch from the eggs after about 2 weeks and find an intermediate host to attach onto (Lymnaeidae snail)
- Within the host the miracidia undergo multiple developmental changes to eventually become cercariae
- Cercariae leave the snail and encyst as metacercariae onto vegetation.
- Vegetation is consumed by final host.
- The metacercariae excyst within the duodenum, releasing larvae
- The larvae penetrate through the gut wall travelling through the peritoneal cavity to the liver
- From the liver the travel to the bile ducts where they mature into adults. Here they can live for up to 10 years.
What is the intermediate host of Fasciola Hepatica
Lymnaeidae snail
What are the Clinical Symptoms of Fascioliasis?
ACUTE: (symptoms caused by migrating flukes)
- Fever, malaise, weight loss, urticaria
CHRONIC: Recurrent cholangitis, biliary obstruction, fatigue
Has a tendency to cause ectopic infections too
What are the investigations for diagnosing Fascioliasis?
Eosinophilia
CT - hypodense lesions (numerous) from fasciola in liver
Serology Tests
Stool Microscopy (Ova) or Bile aspirates (adults or ova)
Fasciola Excretory Secretory Antigen on stool samples
How is fascioliasis managed?
THE ONLY FLUKE THAT PRAZY DOESN’T WORK ON!
Triclabendazole 10mg/kg STAT +/- repitiion in 12h
OR
Nitazaxondie 500mg 12h for 7/7
How can fascioliasis be prevented?
- sheep vaccine
- Treatment of plants
- Cooking of food before ingestion
What is the Oriental Liver Fluke?
Opisthorchis spp. and chlonorchis spp.
Food borne Trematodes
What is the epidemiology of Opisthorchis?
China, South East Asia
What are the natural hosts of Opisthorchis?
Domestic pets
What is the life cycle of Opisthorchis?
Eggs are excreted in host (often human) stool
2. Miracidia hatch from the eggs after about 2 weeks and find an intermediate host to attach onto (Bithynia snail)
3. Within the host the miracidia undergo multiple developmental changes to eventually become cercariae
4. Cercariae leave the snail and encyst as metacercariae onto fish.
5. Fish is consumed by final host (raw or undercooked)
6. The metacercariae excyst within the duodenum, releasing larvae
7. The larvae penetrate through the gut wall travelling through the peritoneal cavity to the liver
8. From the liver the travel to the bile ducts where they mature into adults. Here they can live for up to 15 years.
What is the clinical presentation of Oriental Liver Flukes?
ASYMPTOMATIC
Vague RUQ pain which most commonly occurs in the mid afternoon when adult worms are most active –> patients may state they feel something moving inside them
Anorexia, Flatulense, diarrhoea, fever
Hepatomegaly
Jaundice
What are the complcations of Oriental Liver Fluke
Biliary Cirrhosis
Cholangiocarcinoma (most common cause of liver cancer in SEAsia)
How is Oriental Liver Fluke infection diagnosed?
Stool microscopy
BIliary Aspirate Microscopy
USS Liver
Antigen tests under development
How is Opisthorchis/Clonorchis infection managed?
Praziquantal 40mg/kg STAT
How can Oriental Liver Fluke be prevented?
WASH
MDA with praziquantal
Improved food habits (cook your fish!!)
What is a lung fluke?
Trematode (food borne) from cray fish and shellfish caused by Paragonimus Westermani