This document summarizes key information about nematodes and some important parasitic nematode infections in humans. It describes how nematodes are roundworms that include many free-living and parasitic species. Parasitic nematodes can be intestinal or tissue-dwelling and cause significant diseases. Examples discussed in detail include trichinellosis caused by Trichinella spiralis, ascariasis from Ascaris lumbricoides, and trichuriasis caused by Trichuris trichiura. Their life cycles, clinical manifestations, diagnosis, treatment and prevention are outlined.

1. NEMATODES
Nematodes are elongated, symmetric roundworms and
constitute one of the largest phyla in the animal kingdom.
Most nematode species are free-living, but some have evolved
into parasites of plants and animals, including humans.
Parasitic nematodes of medical significance may be classified
as intestinal or tissue nematodes.
All are zoonotic infections caused by incidental exposure
toinfectious nematodes.

2. INTESTINAL NEMATODES
• More than a billion people worldwide are
infected with one or more species of
intestinal nematodes.
• These parasites are most common in regions
with poor fecal sanitation, particularly in
developing countries in the tropics and
subtropics
• Although nematode infections are not
usually fatal, they contribute to malnutrition
and diminished work capacity.
• Humans may on occasion be infected with
nematode parasites that ordinarily infect
animals; these are zoonotic parasites.

3. Trichinellosis / Trichinosis
Трихинелоза
• Develops after the ingestion of meat
containing larves of Trichinella spiralis -
pork or meat from a carnivore.
• While most infections are mild and
asymptomatic, but heavy infections can
cause:
- severe enteritis,
- periorbital edema,
- myositis,
- death

4. Five species of Trichinella are now recognized as causes of
infection in humans. Two species are distributed worldwide:
- Trichinella spiralis, which is found in a great variety of
carnivorous and omnivorous animals,
- Trichinella pseudospiralis, which is found in mammals and
birds.
- Trichinella nativa is present in Arctic regions and infects
bears;
- Trichinella nelsoni is found in equatorial Africa, where it is
common among felid predators and scavengers such as
hyenas and bush pigs;
- Trichinella britovi is found in temperate areas of Europe
and western Asia among carnivores but not among domestic
swine.

5. Life Cycle
- After the consumption of meat
by the host, encysted larvae are
liberated by digestive acid and
pepsin.
- The larvae invade the small –
bowel mucosa and mature
rapidly into adult worms.
- After about 1 week, female
worms release newborn larvae
that migrate via the circulation
to striated muscle.
- The larvae of all species except
T. pseudospiralis then encyst in
the muscle cell

6. • Human trichinosis is most often caused by the
ingestion of infected pork products and thus can
occur in almost any location where the meat of
domestic or wild swine is eaten.
• Human trichinosis also may be acquired from the
meat of other animals, including:
- dogs (in parts of Asia and Africa),
- horses (in Italy and France), and
- bears and walruses (in northern regions).

7. Pathogenesis And Clinical Features
• Clinical symptoms of trichinosis arise from the
successive phases of parasite enteric invasion, larval
migration, and muscle encystment.
• Most light infections (those with fewer than 10
larvae per gram of muscle) are asymptomatic,
• whereas heavy infections (which can involve more
than 50 larvae per gram of muscle) can be life-
threatening.
• Invasion by large numbers of parasites provokes
diarrhea during the first week after infection.
• Abdominal pain, constipation, nausea, or vomiting
also may be prominent.
• The prolonged and fulminant diarrhea noted
probably reflects a response to repeated infection.

8. The migrating Trichinella larvae provoke a
marked
local and systemic hypersensitivity reaction:
- fever
- hypereosinophilia,
- Periorbital and facial edema
- hemorrhages in the subconjunctivae, retina,
- nail beds ("splinter" hemorrhages).

9. Hypersensitivity reaction:
- Periorbital and facial
edema

10. • dysphagia sometimes develops
• Myocarditis with tachyarrhythmias or heart failure,
• less commonly, encephalitis or pneumonitis may
develop and accounts for most deaths of patients
with trichinosis.
• A maculopapular rash, headache, cough, dyspnea

11. 2 to 3 weeks after infection there are symptoms:
• myositis with myalgias,
• muscle edema,
• weakness develop, usually
• with the inflammatory reactions to migrating larvae.
• The most commonly involved muscle groups include:
- the extraocular muscles;
- the biceps; and
- the muscles of the jaw, neck, lower back, and diaphragm
Peaking about 3 weeks after infection, symptoms subside
only gradually during a prolonged convalescence.

12. Laboratory Findings And Diagnosis
• Blood eosinophilia develops in more than 90 % of
patients with symptomatic trichinosis and may peak at a
level of greater than 50 %
• Serum levels of IgE and
• muscle enzymes, including
- creatine phosphokinase,
- lactate dehydrogenase, and
- aspartate aminotransferase, are elevated in most
symptomatic patients.

13. Epidemiological Diagnosis
- Patients should be questioned about their consumption of
pork or wild-animal meat and about illness in other
individuals who ate the same meat.
- A presumptive clinical diagnosis can be based on fevers,
eosinophilia, periorbital edema, and myalgias after a
suspect meal.
- Arise in the titer of parasite-specific antibody, which
usually does not occur until after the third week of
infection, confirms the diagnosis.
- Alternatively, a definitive diagnosis requires surgical
biopsy of at least 1 g of involved muscle; the yields are
highest near tendon insertions. The fresh muscle tissue
should be compressed between glass slides and examined
microscopically

14. TREATMENT
Current anthelmintic drugs are ineffective against
Trichinella larvae in muscle.
Glucocorticoids like prednisone (1mg/kg daily for 5 days)
are beneficial for severe myositis and myocarditis.
Mebendazole, like thiabendazole, appears to be active
against enteric stages of the parasite, but its efficacy against
encysted larvae has not been conclusively demonstrated.
• Mebendazole (Vermox) tb. 0,1 gr., 20 mg/kg
/day, 3x1, 10-14 days; children - 5 mg/ kg/day
• Albendazole (Zentel) tb. 0,2 gr, 10 mg/kg /day, 7-10 days
• Pyrantel (Combartin) tb. 0,25 gr 10 mg/kg/twice a day, 5
days
• antipyretics, and analgesics.

15. Prevention
Larvae may be killed by:
- cooking pork until it is no longer pink or
- by freezing it at -15°C for 3 weeks.
- However, Arctic T. nativa larvae in walrus or bear meat
are relatively resistant and may remain viable despite
freezing.

16. Ascariasis
/Ascaridosis/
Ascaris lumbricoides is the
largest intestinal nematode
parasite of humans, reaching
up to 40 cm in length.
1 billion people are infected
worldwide.
Most infected individuals
have low worm burdens and
are asymptomatic. Clinical
disease arises from
pulmonary and intestinal
complications.

17. Life Cycle
• Adult worms live in the lumen of
the small intestine.
• Mature female Ascaris worms are
producing up to 240,000 eggs a
day, which pass with the feces.
• Ascarid eggs, which are
remarkably resistant to
environmental stresses, become
infective after several weeks of
maturation in the soil and can
remain infective for years.
• After infective eggs are
swallowed, larvae hatched in the
intestine invade the
mucosa, migrate via the circulation
to the lungs, break into the
alveoli, ascend the bronchial
tree, and return via swallowing to
the small intestine, where they
develop into adult worms.

18. Between 2 and 3 months elapse between initial
infection and egg production.
• The adult worms live for approximately 1 to 2 years.
Epidemiology
• Ascaris is widely distributed in tropical and
subtropical regions as well as in other humid areas.
• Transmission typically occurs via fecally
contaminated soil

19. Clinical Features
During the lung phase of larval migration, about 9 to 12
days after egg ingestion, patients may develop an:
- irritating nonproductive cough and
- burning substernal discomfort that is aggravated by
coughing or deep inspiration.
- Dyspnea and blood-tinged sputum are less common.
- Fever is usually reported, with temperatures sometimes
exceeding 38.5°C.
- Chest x-rays may reveal evidence of eosinophilic
pneumonitis (Loeffler's syndrome), with round or oval
infiltrates a few millimeters to several centimeters in size.
These infiltrates may be transient and intermittent.

20. • Adult worms in the small intestine usually cause no
symptoms.
• In heavy infections, particularly in children, a large bolus of
entangled worms can cause pain and small-bowel
obstruction,
• complicated by perforation
• A large worm can enter in the biliary tree, causing biliary
colic, cholecystitis, holangitis, pancreatitis, and
intrahepatic abscesses.
• Migration of an adult worm up the esophagus can provoke
coughing and oral expulsion of the worm.
• intestinal and biliary ascariasis can rival acute appendicitis
and gallstones as causes of surgical acute abdomen.

21. Laboratory Findings
• Microscopic detection of
characteristic Ascaris
eggs (65 by 45 um) in
fecal samples.
• Larvae can be found in
sputum
• A plain abdominal film
• Worms can be detected
by ultrasound and
cholangiopancreatograpy

22. TREATMENT
- Mebendazole 2 x 0,2 gr. 3 days
- Albendazole 0,4 gr.
These benzimidazoles are contraindicated in
pregnancy
• Pyrantel pamoate – 10 mg/kg and
• piperazine citrate are safe in pregnancy

23. TRICHURIASIS
Most invasions with the
whipworm Trichuris trichiura
are asymptomatic, but
heavy infections may cause
gastrointestinal symptoms.
Like the other soil-transmitted
helminths, whipworm is
distributed globally in the
tropics and subtropics and is
most common among poor
children.

24. Life Cycle
The adult worms reside in the
colon and cecum, into the
superficial mucosa.
Thousands of eggs laid daily by
adult female worms pass via the
feces and mature in the soil.
After ingestion, infective eggs
hatch in the duodenum, releasing
larvae that mature before
migrating to the large bowel.
The entire cycle takes about 3
months, and adult worms may live
for several years.

25. Clinical Features
Most infected individuals have no symptoms
Heavy infections may result in abdominal
pain, anorexia, and bloody or mucoid diarrhea resembling
inflammatory bowel disease.
Rectal prolapse can result from massive infections in
children, who often suffer from malnourishment and other
diarrheal illnesses.

26. Diagnosis
The characteristic - 50- by 20-um lemon-shaped
whipworm eggs are readily detected on stool
examination.
Treatment
• Adult worms, which are 3 to 5 cm long, occasionally
can be seen on proctoscopy.
- Mebendazole
- Albendazole
- Pyrantel pamoate

27. ENTEROBIOSIS
PINWORM
Enterobius vermicularis is
more common in temperate
countries than in the tropics.
• Enterobius adult worms are about 1
cm long and dwell in the bowel
lumen.
• The gravid female worm migrates
nocturnally out into the perianal
region and releases up to 10,000
immature eggs.

28. Life Cycle
The eggs become infective
within hours and are transmitted
via hand-to-mouth passage.
This life cycle takes about 1 month,
and adult worms survive for
about 2 months.
Self- infection results from
perianal scratching and transport
of infective eggs on the hands or
under the nails to the mouth.
Owing to the ease of person-to-
person spread, pinworm
infections are common among
family members
andinstitutionalized populations.

29. Clinical Features
• Most pinworm infections are asymptomatic.
• Perianal pruritus is the cardinal symptom. The itching is
often worse at night owing to the nocturnal migration of the
female worms, and it may lead to excoriation and bacterial
superinfection.
• Heavy infections have been claimed to cause abdominal
pain and weight loss.
• On rare occasions, pinworms invade the female genital
tract, causing vulvovaginitis and pelvic or peritoneal
granulomas.
• Eosinophilia or elevated levels of serum IgE are rare.

30. Diagnosis
Since pinworm eggs are not usually
released in the bowel, the diagnosis
cannot be made by looking for eggs
in the feces.
Instead, eggs deposited in the
perianal region are detected by the
application of clear cellulose tape to
the perianal region in the morning.
After the tape is transferred to a
microscope slide, will reveal the
characteristic pinworm eggs, which
are oval, measure 55 by 25 um, and
are flattened along one side.

31. TREATMENT
Mebendazole 2 x 0,2 gr. 3 days
Albendazole 0,4 gr.
These benzimidazoles are contraindicated in pregnancy
Pyrantel pamoate – 10 mg/kg and
piperazine citrate are safe in pregnancy
All affected individuals should be given a dose of
mebendazole or pyrantel pamoate, with treatment repeated
after 10 to 14 days.
• Treatment of household members is also advocated to
eliminate asymptomatic reservoirs of potential reinfection.