Nematodes

Question 1

What are nematodes

Answer 1

Free living parasites. Round worms with unsegmented bodies.
Body cavity filled with pressurized fluid (100 mm Hg), hydroskeleton, allows for wriggling and locomotion.

Complete digestive system.
Transmission ingestive or invasive.

Question 2

Pinworm

Enerobius Vermicularis

Answer 2

Humans are only host!

Transmission
Ingestion of eggs, self to or person to person / Autoinfection (retroinfection)

Epidemiology
occurs world wide

Pathology
Intense Peri Anal Itching
Urogenital problems rare, if it gets into the vagina

Diagnosis
Persistant perianal itch
observation of eggs with the Scotch Tape Test

Treatment and Prevention
Albendazole, mebendazole, pyrantel pamoate
Treat whole family

Question 3

Trichuris Trichiura

Whipworm

Answer 3

Humans are the only host
Has an Obligatory Soil stage

Transmission
Ingestion of embryonated eggs
No person to person infection because of obligatory soil stage

Epidemiology
occurs world wide

Pathology
Trichuriasis
low to moderate, some bleeding (adults in Cecum)
High, disrupted mucosa, bloody stool, anemia, prolaps, abdominal pain

Diagnosis
Characteristic bile-stained eggs in stool

Treatment
3 days of albendazole, mebendazole, ivermectin; iron supplement

Prevention
Avoid using human waste as fertilizer
wash and prepare vegetables and fruit

Question 4

Ascaris Lumbricoides

Roundworm

Answer 4

Humans are the only host
Obligatory soil stage

Transmission
Ingestion of embryonated eggs, no direct person to person transmission

Epidemiology
tropical and subtropical
Most common worm infection
Associated with poor public hygiene and human waster as fertilizer

Pathology (Ascariasis)
Low; usually none, worms don’t attach to intestinal mucosa
High; abdominal tenderness, distension, intestinal obstruction, growth impairment in children, stressed worms (fever or drugs attack them) may migrate to nose, peritoneum etc.

Immunity
inflammation from larval migration in the lung, pneumonitis, eosinophilia

Diagnosis
Bile-stained fertilized and unfertilized eggs in stool
Pulmonary larval phase, larva and eosinophils in sputum

Treatment
1-3 days of albendazole, mebendazole, ivermectin

Question 5

Hookworms
Necator Americanus
Ancylostoma Duodenale

Other variants

Answer 5

Obligatory Soil Stage

N. Americanus has 2 teeth
A. Duodenale has 4 teeth

Other variants (for dogs and cats) can hook into human feet/skin but not get into your bloodstream b/c they die.

Transmission, through skin by filariform larvae

Eggs in poop not larvae

Epidemiology
Worldwide, tropical

Pathology
Rash and itching at penetration site
Microcytic Hypochromic anemia because they eat your blood
Eosinophilic enteritis with episodes of abdominal pain, nausea, vomiting, and diarrhea

Immunity
Inflammation from larval migration in the lung, pneumonitis, eosinophilia

Diagnosis
Eggs in stool, anemia
Larvae for species differentiation

Treatment
1-3 days of albendazole, mebendazole, pyrantel pamoate, iron supplementation, blood transfusion in severe cases of anemia

Prevention
Wear shoes

Question 6

Strongyloides Stercoralis

Answer 6

3 development options for rhabitiform larvae

1. Direct
   Hookworm-like, except larvae in feces, no amplification
2. Indirect
   Sexual Reproduction in soil; Environmental amplification
3. Autoinfection
   Maturation in host, penetration of colonic mucosa or perianal skin
   Host amplification

Transmission
Penetration of skin by filariform larvae, autoinfection possible

Epidemiology
Occurs globally in tropical and subtropical areas

Pathology (Strongyloidiasis)
Pulmonary Symptoms as in ascariasis and hookworm infections
Heavy worm load leads to dysentery, malabsorption
Rash on butt, legs and lower back (autoinfection)

Immunity
Inflammation from larval migration in the lung

Diagnosis
Larvae in tool or sputum (pulmonary phase)
Eggs are not usually in stool
Serology

Treatment
All infected persons treated, 1 -2 days ivermectin, 7 days albendazole

Prevention
Good hygiene, wearing shoes

Question 7

Trichinella Spiralis

Answer 7

Adult worms and encysted larvae develop in a single vertebrate host
1. infected ANIMAL serves as DEFINITIVE HOST
2, Secondary host is required to complete the life cycle
3. HUMANS are a DEAD-END host

Transmission
Raw/undercooked meat containing cysts

Epidemiology
Worldwide, lots of pork products

Pathology (Trichinosis)
Mild infection, asymptomatic or slight fever (flu-like)
More extensive infections results in persistent fever, GI distress, muscle pain, peri orbital edema, splinter hemorrhages beneath nails
Heavy infections lead to muscle destruction (diaphragm), myocarditis, encephalitis, pneumonitis and can result in death

Immunity
Humoral immune response, (eosinophilia)

Diagnosis
Esinophilia, myositis, fever, periorbital edema
Serology, muscle biopsy

Treatment
Early treatment with albendazole, mebendazole
Symptomatic treatment with steroids

Prevention
Thorough cooking of pork, freeze for 3 weeks

Question 8

Toxocara Canis

Toxocara Cati

Answer 8

No direct person to person transmission b/c Obligatory soil stage!
Humans are accidental host

Transmission
Ingestion of embryonated eggs

Epidemiology
30 - 100% of puppies infected
estimated 1 - 3 million humans infected (CDC top 5)
More common in warm climates

Pathology (Toxocariasis)
Light infections often asymptomatic
Heavier infections; can lead to severe damage in any location due to VLM (Visceral Larval Migrans), OLM (Ocular Larval Migrans) NLM
Fever, enlarged liver, pulmonary symptoms, ocular disease (70 people blinded per year in US), seizure, death may result

Immunity
Immune Hypersensitivity common, eosinophilic granulomas

Diagnosis
Clinical signs of visceral or ocular toxocariasis, eosinophilia
Serology

HUMANS ARE ACCIDENTAL HOST