Microbiology: Nematodes/ flukes/ ectoparasites Flashcards
What are the common species of nematodes and their route of infection
Ingestion: “EATTT”
- Enterobius
- Ascaris
- Toxocara
- Trichinella
- Trichuris
Cutaneous: “SANd”
- Strongyloides
- Ancylostoma
- Necator
Bite wounds: “LOW”
- Loa-loa
- Onchocerca volvulus
- Wuchereria bancrofti
Strongylodies stercoralis
Threadworms
Filariasis disease that is endemic to tropical regions
- can cause pulmonary infections and septic shock in immunocompromised individuals.
Life cycle:
- larvae live in contained ground soil enter host through broken skin lesions -> hematologists spread -> pulmonary alveolar -> tracheobronchial tree -> esophagus and gets swallowed and passed through the GI system to the duodenum and jejunum
- mature in the duodenum and jejunum and then are reproduced in feces
- can auto infect oneself again*
Signs/symptoms: Cutaneous - edema, petechiae, prutitus GI - bloating, diarrhea, nausea/vomiting - anorexia - epigastric pain - malabsorption Pulmonary - dry cough - dyspnea/wheezing/ hemoptysis
- can produce a hyper infection syndrome from auto infection causing dissemination into blood stream*
Treatment:
- ivermectin*
- Albendazole
- must combined both if hyper-infection is present
Hyper infection syndrome
A syndrome caused by autoinfecting ones self with already infected worms.
- causes worms to be in the blood stream and disseminated throughout body
highly vulnerable is immunocompromised individuals
Symptoms:
- depends on organ hit
- also usually causes septic shock
Treatment:
- ivermectin + Albendazole
Loffler syndrome
A transient pulmonary disease that can occur due to autoinfection or normal infection in a immunocompromised individual of a worm.
Only certain worm species can cause this
- Necator Americanus
- Strongyloides
- Ascaris Lumbricoides
- Toxocara canis
Symptoms: - dry irritating cough - substernal burning discomfort - dyspnea - wheezing - fever - bloody sputum (hemoptysis) -
Ancyclostoma duodenale and Necator Americanus
Both are hookworms
Most common hookworm species that cause GI infections. Are transmitted via cutaneous wounds on contaminated soil or oral route.
- mild = less 100 worms
- moderate = 100-500 worms
- heavy = 500-1000 worms
can cause microcytic anemia and/or cutaneous larva migrans
Feed on RBCs and intestinal epithelium as well as produce anticoagulant peptides (promote bleeding in the GI system and anemia)
3 phases:
1) cutaneous phase:
- local puritic dermatitis w/ papular focal rash (usually between toes or at site of infection) cutaneous larva migrans
2) pulmonary phase:
- usually asymptomatic but can show sore throat/fever/cough
3) GI phase:
- mid epigastric pain, appetitive loss, nausea/vomiting, diarrhea
- GI bleeding (severe infection only)
- heavy infections can also show hypoproteinemia (weight loss and anasarca (body wide edema)), anemia (fatigue, AMS, dyspena, pallor*
Treatment:
- bendazoles
- Pyrantel pamoate
Angiostrongylus
Eosinophilic meningitis
Is a nematode that is transmitted via undercooked snails/fish/frogs or contaminated vegetables. Also rat droppings
- most common cause of eosinophilic menigitis
Signs/symptoms: (takes 3wks -2 months)
- meningitis symptoms w/ parasthesia/hyperasthesia
- encephalitis symptoms
- also can show visual impairment, pain on eye movements and retinal edema
- quadriparesis/areflexia/respiratory failure/death (ONLY if not treated)
Treatment:
- DONT use antihelminthic agents (killing them causes increased inflammation and increases chances of death since they are in the Brain)
- corticosteroids and analgesics (helminths usually are self-lifting in this case)
- can also drain CSF as needed
Ascaris Lumbricoides
Giant roundworm
Intestinal roundworm that is the causative agent for ascariasis.
- transmitted via contaminated pig/chicken consumption, contained chicken egg consumption, infected soil and chicken/pig feces.
2 phases
1) pulmonary phase (loffler syndrome)
- dry cough
- dyspnea
- fever
- wheezing
- substernal burning
- hemoptysis
2) intestinal phase
- ab discomfort
- anorexia/ weight loss
- nausea/vomiting
- diarrhea
- ascariais* (enlargement of the duodenum and ileum and Ileocecal valve with worms causing intestinal obstruction and possible necrosis/infarct of the intestine)
- pancreatitis (sometimes)
Treatment:
- bendazoles
- pyrantel pamoate (pregnant patients only)
Enterobius Vermicularis
Pinworms
Small roundworm infection that infects colon and rectum tissues
- is usually caused by an autoinfection from touching a contaminated surface and then scratching either the mouth or anus region (hence why kids get this most often compared to adults)
- there is a rare chance that inhalation of eggs can cause infection*
Signs/symptoms:
- initially is asymptomatic
- then moves to nocturnal pruritis ani (perinatal itching that is more common at night)
- then under high worm load, causes ab pain/nausea/vomiting
Diagnosis is by the scotch tape test:
- take adhesive clear tape and press against perinatal surface, remove and then place on glass slide. If (+) will show worm eggs and sometimes actual worms.
Treatment:
- bendazoles
- pyrantel pamoate (pregnant patients only)
Dracunculiasis
Guinea worm
Rare Water-borne worm that causes GI/cutaneous disease in infected host.
- endemic to Eastern Africa
Signs/symptoms:
- usually intimates with broad systemic symptoms
- fever, pruritis, dizziness, nausea/vomiting. Diarrhea
- later, develops cutaneous painful papules, which get more painful as they enlarge.
- ultimately, the papule will burst and the worm will come out of the ulceration
Diagnosis:
- history
- can see the worm in the ulcer sometimes
- x-rays can also sometimes see the worm
Treatment:
- worm extraction over multiple days
- must be careful to not break the worm, or will lead to seriously painful, erythematous and swelling at lesion site*
Loa Loa
African Eye worm
Vector based nematode that spreads via deer/horse or mango fly bites
- endemic to eastern/central Africa
Worm initially enters skin, then enters blood stream and then can go to any of the following sites (but usually picks the eye)
- heart (cardiomyopathy
- extremities (calabar swellings)
- brain (encephalitis)
- kidneys (nephropathy)
- joints (arthritis)
- lymph nodes (lymphadenitis)
Signs/symptoms:
1) Calabar swellings:
- 5-20cm non-erythematous lesions that are transient
- lesions have localized swelling and are usually in the face or extremities
- also localized pain, pruritis and sometimes entrapment disorders in the extremities
2) subconjunvtical eye infections:
- non-painful infiltration of the subconjunctival areas and cases eye lid swelling
- sometimes the worm is visible
Treatment:
- Diethylcarabmazine (DEC)*
- corticosteroids (only in calabar swelling)
Onchocerca volvulus
river blindness
Filarial nematode that is transmitted via the female black fly.
- endemic to Western Africa and Eastern South America
Can infect subcutaneous tissue or anterior/posterior chamber of the eye
Signs/symptoms:
1) ocular onchocerciasis:
- infection of the anterior or posterior chambers of the eye
- causes punctate keratitis, sclerosisi in the cornea
- visual acuity decreases overtime and eventually leads to blindness if not treated (this is caused by eosinophilic reaction and inflammation to the parasite)
2) cutaneous (Onchocercal skin disease)
- black/brown papules begin to develop all over the body, also destruction of elastic fibers is seen
- causes pruritis, depigmentation/hyperpigmentation
- can rupture and becom ulcers
Treatment:
- ivermectin* (only kills immature worms)
- doxycycline* (stops maturity and reproduction)
- both are usually used in tandem and may require a second dose 2-3 months after initial treatment.
Toxocara Canis
Visceral larva migrans
Vector nematode that is carried by dogs/cats/pigs (usually in the stool), as well as contaminated soil.
- untreated sandboxes are common ares for this
Worms start in the GI tract and reproduce in the small intestine. Here they penetrate the small intestine and migrate throughout the blood stream, usually to the pulmonary system/liver/CNS system and eyes.
Visceral larva migrans signs/symptoms:
- pruritic urticaria (papules along the skin that are very itchy/burning)
- fever
- anorexia/weight loss
- malaise
- irritability
Ocular larva migrans signs/symptoms:
- unilateral vision impairment
- uveitis
- papilitis
- endopthalmmitis (inner eye inflammation)
- both can also show hepatomegaly and ARDS*
Treatment:
- Albendazole*
Trichinella spiralis
Trichinosis
Roundworm infection that is seen worldwide and is most commonly obtained via uncooked/raw meat of carnivores animals
Are consumed and mature in the small intestines. Eventually migrate out to the blood stream and then into striated muscles where they form cysts.
- this cycle is continued as animals each other.
Signs/symptoms:
- nausea/vomiting
- ab pain
- diarrhea
- severe muscle pain that gets worse with use*
- tenderness
- swelling
- muscle weakness
- high fever
- (+/-) periorbital swelling
- (+/-) retinal hemorrhages on fundoscopic examination
- diagnosis usually requires lab values suggestive of muscle damage as well as muscle biopsy showing worm larva in the muscle
Treatment:
- self-resolving if not severe (no muscle symptoms)
- bendazoles and corticosteroids if severe
Trichuris Trichuria
whipworm
Human specific nematode that is commonly seen in unsanitary conditions or consumption of undercooked/rcontamined vegetables
- is a human specific intestinal parasite (so often seen in children)
can cause rectal prolapse with heavy infectious load
Signs/symptoms:
- can be asymptomatic unless heavy infection load
- ab pain and distention
- diarrhea
- bloody stool and mucus
- nocturnal spontaneous bowel unloading
- constant having to use the bathroom
Treatment:
- bedazoles
Wuchereria Bancrofti
Lymphatic Filariasis) (elephantiasis
Mosquito-borne nematode infection that is notorious for causing extreme cases of elephantiasis.
- endemic to Africa, India and pacific islands
Enter blood stream through mosquito bite and travel to lymph nodes/lymph vessels, where they mature and reproduce.
Signs/symptoms
- extreme limb swelling
- extreme painful lymphadenopathy
- Chyluria (milky white urine due to lymph draining into the kidneys)
- fever
- hydroceles may be present
- lymphangiectasis
- hyperpigmentation of skin
Treatment:
- Diethylcarbamazine
- can also use doxycycline as adjuvant
