Helminths Flashcards
List the helminths (9)
Clonarchis sinesis Diphyllobothrium latum Echinococcus granulosus Loa Loa Onchocera volvulus Enterobius vermicularis (Pinworm) Schistosoma Strongyloides stercoralis Taenia solium
Which helminths are trematodes (flukes)? (2)
Clonarchis
Schistosoma
Which helminths are nematodes (roundworms)? (4)
Loa Loa
Onchocera
Enterobius
Strongyloides
Which helminths are cestodes (tapeworms)? (3)
Diphyllobothrium
Echinococcus
Taenia
Clonorchis transmission
Undercooked fish - contracted by eating fish that is undercooked.
Fish are an intermediate host for the parasite - they burrow into the fish muscle and wait as cysts.
At this point they escape the cysts and infect humans when they consume the fish
Clonorchis presentation
Clonorchis is a liver fluke - it affects livers and gallbladders
1) Biliary tract inflammation
Once digested by human, the parasite burrows from SI to liver. From liver they feed on bile and travel to bile duct.
Clonarchis induces an inflammatory reaction from the body within the bile ducts and liver
2) Pigmented gallstones
Stones are typically brown in pigment and consist of cholesterol and calcium soaps of fatty acids.
These stones are seen in patients with mechanical obstruction to bile flow (like when this parasite induces inflammation in bile duct)
Associated with cholangiocarcinoma - it’s an oncogenic microbe
Clonorchis Tx
Praziquantel
Diphyllobothrium transmission
Ingestion of larvae from raw fish
Diphyllobothrium pathogenesis/presentation
It competes for Vitamin B12 - 80% of patients infected are asymptomatic and can go years without having their infection detected. Parasite then absorbs 80% of host’s B12 intake, leading to:
Megaloblastic anemia - indistinguishable from pernicious anemia - can also translate to subtle demyelinatie neuro symptoms
Diphyllobothrium Tx
Praziquantel (not FDA approved here)
How large is echinococcus?
tapeworm. 2-7mm in length
Echinococcus transmission
Ingestion of eggs from dog feces - proper hygiene helps prevent spread
Echinococcus presentation
1) Hydatid cysts in liver:
Infection causes slow-growing cysts in liver (rarely in lungs, spleen, heart too). These are the hydatid cysts - filled with clear fluid containing antibodies
Depending on the size, the cysts may be asymptomatic or present as an uncomfortable mass
2) Fibrosis and necrosis - how body reacts to the cyst growth
3) Anaphylaxis if antigens are released - if cysts rupture while in the body (during surg or trauma), the patient will go into anaphylactic shock - develop high fever, pruritis, edema, breathing trouble
Echinococcus Tx
Albendazole - usually combined with surgical removal of cysts (if accessible)
What disease does Loa Loa cause?
Subcutaneous filariasis
Loa Loa transmission
Fly bite - fly is the vector - When fly bites, the loa loa larvae penetrate the subQ tissue and are able to cause disease
Loa Loa presentation
SubQ filariasis
1) Calabar swellings in skin - worm travels through subQ tissue leading to inflammation wherever it goes. When it stops for a while, local inflammation (Calabar swelling) happens.
Presents as localized, tense, inflammatory edema in joints for 1-3 days
2) Conjunctiva - It can travel through and infect the eye causing eye swelling. It can often be seen when it enters the eye since it moves subcutaneously in the conjunctiva
Loa Loa Tx
Diethylcarbamazine (DEC): Treatment of choice for microfilariae and adult worms. Surgical removal of the worms can be done as well. Patients with serious infections may experience brain inflammation after DEC treatment.
Albendazole - sometimes used AFTER multiple DEC treatments. It causes death in adult worms, but not in microfiliariae. Fewer side effects than DEC.
Onchocera transmission
Female blackfly bite
It is in microfilarial form when it is in its vector (female blackfly). When they seek a bloodmeal, biting humans, the microfilaria are transmitted to us. These larvae then mature into adults in host’s subQ tissue.
Preferentially infects tissues over intestines
Onchocera presentation
1) Hyperpigmented skin
Since it likes to migrate to subQ tissues, infections usually have derm symptoms - skin nodules, pruritis, inflammation, and hyperpigmentation
2) River Blindness
Patients can develop vision loss - disease most often occurs in Subsaharan Africa blackflies are found near rivers
Ochocera Tx
Ivermectin
Relieves derm symptoms (itching, nodules, hyperpigmentation) and helps stop progression of blindness
It only kills adult worms, so it usually has to be re-administered
Enterobius transmission
Pinworm
Ingestion of pinworm egg: fecal-oral through contaminated hands, food, or water.
Enterobius presentation
Pinworm
1) Intestinal infection
After eating the pinworm eggs, a 4-6 week incubation ensues and patients develop intestinal infection of adult pinworms. Infection is called enterobiasis.
This is asymptomatic in 1/3 of patients
2) Anal pruritis
Most common symptom of enterobius infection is intense anal itching
This happens bc adult pinworms exit the digestive tract to lay eggs around host’s anus at night
Pruritis is seen around perineum and anus - tickling, tingling, even pain
Enterobius diagnosis
Scotch Tape Test - transparent adhesive tape applied to patient’s anal area. Tape is removed and viewed under low-power microscope to look for pinworm eggs.
Enterobius Tx
Albendazole - inhibits glycogen metabolism in worms, starving them to death. This kills only adults though so it must be re-administered to fully eradicate.
Pyrantel Pamoate (2nd line) - causes neuromuscular blockage in worm
Schistosoma transmission
It is a blood fluke
Snail-infested water! Snails are the host - humans develop infection from being exposed to snail-infested water.
Schistosoma presentation
1) Intense immune response - symptoms of schistosomiasis happen after an intense immune response from host to worms and trapped eggs. This leads to cellular infiltrant that leads to granulomas, inflammation and fibrosis
2) Intestinal disease - As eggs pass through GI, many pathologic events take place
Ulceration, eggs getting lodged in intestines, worms being trapped in mesenteric intestinal veins
3) Hepatosplenic granuloma - parasites usually go to liver sinusoids where they feed on RBCs
From this liver migration, hepatorenal blood flow can become interrupted (through obstruction via worm or egg), leading to hepatosplenic dysfunction and granuloma formation.
Schistosoma mansoni and japonicum are specifically known for this.
4) Squamous cell cancer of bladder - some types can travel to urethral areas or the bladder and kidneys - can lead to urinary granulomas and GU issues in patients. Schistosoma hematobivin can lead to SCC of bladder in those who are chronically infected.
Patients display painless hematuria
Schistosoma diagnosis
ELISA - look for parasitic antigens
Schistosoma Tx
Praziquantel
Strongyloides transmission
This nematode is adapted to living in top 15cm of soil. We get infected when larvae burrow through our skin (usually barefoot)
Once in skin, the larvae burrow into bloodstream where they mature and invade organs
Strongyloides presentation
Uncomplicated Disease:
1) GI distress - most often it affects GI and leads to intestinal infection. This can be asymptomatic for a while. Sometimes, symptoms like vomiting, diarrhea, epigastric pain are seen
2) Loffler’s Syndrome - a pulmonary eosinophilia which occurs from parasitic invasion (eosinophilic pneumonia)
3) Dermatitis - patients can develop urticarial rashes at the site of larval penetration and other classic areas - feet, buttocks, waist.
Disseminated Disease:
Occurs in immunocompromised - can then cause septicemia, meningitis, maybe death
Strongyloides Tx
Ivermectin - only kills adults. Re-dose to eradicate
Albendazole - when ivermectin fails or when disseminated disease occurs.
What 2 diseases does Taenia cause?
Taeniasis (larval ingestion)
Cysticercosis (egg ingestion)
Taenia infection transmission
Taeniasis - from ingestion of larvae in undercooked pork
Cysticercosis - from ingestion of cestode eggs
Taenia infection presentation
1) Taeniasis
Ingestion of larvae from undercooked pork. Larvae grow into adults in SI. Infection is generally harmless and can be asymptomatic. Sometimes, GI upset is reported.
2) Cysticercosis
More dangerous. When eggs are ingested instead. Larvae mature in body and form cysts that embed into various parts of the body (skin, muscles, CNS)
Neurocysticercosis - most severe form - affects the brain and is a cause of epilepsy
Taenia Tx
Albendazole - indicated for neurocysticercosis
Praziquantel - treats intestinal taeniasis and non-neuro forms of cysticercosis
