Chapter 15-NEMATODES(SHAYNE SUNICO).pptx

NEMATODES
By: Shayne G. Sunico

Nematodes or roundworms are unsegmented, bilaterally symmetrical
worms with elongated, cylindrical bodies. The life cycle of these
parasites consists of three stages: embryonated egg or ova, larva, and
adult worms. The body covering is called the cuticle.
Adult worms are equipped with a complete digestive system, simple
nervous system, an excretory system, and a reproductive system. The
digestive system consists of three structures: the stomodeum (mouth,
esophagus, and buccal cavity), intestines, and anus (proctodeum).
INTRODUCTION TO NEMATODES

Nematodes have a sensory organ called amphid, which is usually located in
the anterior end of the head region of the worms. Some nematodes
(Ascaris, Necator and Wuchereria) are equipped with a pair of caudal
chemoreceptors called phasmids.
Most patients with nematode infection are asymptomatic. The severity of
the disease depends on the worm burden and the host’s immunity. The
nematodes may be divided into three groups based on their primary
location in the body: intestinal nematodes, intestinal-tissue nematodes,
and the blood-tissue nematodes.
INTRODUCTION TO NEMATODES

Nematodes Are Divided Into Three (3)
Groups, And These Are:
a.INTESTINAL NEMATODES
b.BLOOD-TISSUE NEMATODES; and
c.INTESTINAL-TISSUE NEMATODES

Ascaris lumbricoides (Large Intestinal Roundworm)
Important properties and Life cycle
Ascaris lumbricoides is the largest intestinal roundworm infecting humans. The
worm is creamy-white in color with an outer covering of cuticle. Humans acquire infection
ingestion of food or water contaminated with human feces containing the infective
ova.
Epidemiology and Pathogenesis
Ascaris infection considered as the most common helminth infection worldwide.
children are the most affected when they play in soil contaminated with human feces. The
are more common in areas characterized by warm climates and poor sanitation.
INTESTINAL NEMATODES

Disease: Ascariasis
Asymptomatic infection is usually seen with low worm burden. Symptomatic infection
occurs due to migration of the parasite through the host. During larval migration, the larvae may
induce allergic reactions, manifesting as asthmatic attacks accompanied by the eosinophilia
(Loeffler’s Syndrome).
An adult worm can obstruct the appendix leading to appendicitis. Other organs that can be
obstructed include the liver and the bile ducts. Due to tough, flexible body of the worms, it may
cause perforation of the intestines, leading to peritonitis which can be fatal.
Laboratory Diagnosis
Diagnosis is established by finding of the eggs in a stool specimen. In cases of heavy
worms burden, the adult worm may be present in the stool or be regurgitated. Larvae may be
recovered from the sputum during the pulmonary phase of the disease.

Treatment
Drugs that have been proven effective are mebendazole, albendazole, and
pyrantel pamoate.
Prevention and Control
The preventive measures are measures used to prevent other parasitic
infections such as proper disposal of human feces, health education of the
population, and improved personal hygiene. It is also recommended to avoid using
human feces as fertilizers. A program of mass chemotherapy is recommended
especially for children and in areas with high incidence of parasitism.

Enterobius vermicularis (Pinworm, Seatworm)
Important properties and Life cycle
The egg of E. vermicularis is typically oval and flat on one side. The adult
small and yellowish-white in color. The common name pinworm is based on the
a clear, pointed tail of the adult female that resembles a pinhead. Some infective
eggs may migrate back into the host body rather than being dislodge leading to
Autoinfection occurs as a result of hand-to-mouth transmission.
Pinworm infection occurs worldwide, especially in temperate regions.
eggs in the anal area incite a hypersensitivity reaction that leads to the prominent
manifestation of the disease- anal itchiness. Like Ascaris, some pinworms may obstruct
appendix leading to appendicitis.

Disease: Enterobiasis
Most cases of Enterobiasis are asymptomatic. The most common
manifestation is intense itching with inflammation in the anal area (pruritus ani) or
the vaginal area which occurs most frequently at night.
Definitive diagnosis is established by demonstration of the eggs or adult
female using the Scotch Tape Method or Cellophane Tape Method. The small size
of the eggs may make recovery from stool difficult.

Treatment
Drugs of choice for treatment are albendazole, mebendazole, or
pyrantel pamoate.
Good personal hygiene, clipping of fingernails, thorough washing
of beddings, and prompt treatment of infected persons contribute to
the control and prevention of the parasite spreading to the other
individuals.

Trichuris trichiura (Whipworm)
Important Properties and Life Cycle
The eggs of the human whipworm have a characteristic barrel or football shape
prominent hyaline plug at each end of the egg. The anterior end of the adult worm appears
colorless while the posterior end is pinkish in color. The male worm has a recognizable
The posterior end is larger and resembles the handle of a whip while the anterior end
whip itself.
Humans acquire the infection through ingestion of food or water contaminated by
s containing the infective eggs. The larvae emerge from the eggs in the small intestines,
immature adults, and migrate to the colon where complete maturation and mating occur.
Thousands of eggs are produced each day, which are then passed in the feces.

The whipworms is the third most common roundworm affecting humans. Infection
seen worldwide, especially in tropical countries and areas with poor sanitation
practices The parasite, like dicari, is seen in locales where human feces is used for
fertilizer and where humans defecate directly on the soil. Children are at highest
risk for development of infection when they play in contaminated soil. Infection is
acquired primarily by ingesting food o contaminated by human feces containing
the infective eggs. Adult worms burrow their hair. When anterior ends into the
intestinal mucosa but do not cause significant anemia.

Disease:Trichuriasis
Severity and occurrence of manifestations of trichuriasis are related to the intensity of
the worm burden. Heavy infection in children resemble manifestations of ulcerative colitis, a
chronic inflammatory condition of the colon that has an autoimmune etiology Manifestations
may include chronic dysentery (bloody, mucoid diarrhea), severe anemia, or growth
retardation. Rectal prolapse and hyperperistalsis are also seen in infected children. Rectal
prolapse occurs due to irritation and straining during defecation. Manifestations in adults
resemble those of inflammatory bowel disease and include abdominal pain and tenderness,
weakness, and dysentery.
Diagnosis is confirmed by demonstrating the presence of characteristic eggs in stool
specimens.

This is Rectal prolapse is a condition that can result from whipworm infections. It occurs when the rectum loses
its attachment to the internal body structure and protrudes from the anus.

Treatment
Drugs of choice for treatment are mebendazole or albendazole.
Effective preventive and control measures include health
education, proper sanitation, good personal hygiene, and avoidance of
use of human feces as fertilizer.

Ancylostoma duodenale (Old World Hookworm) and Necator americanus
(New World Hookworm)
There are two common species of hookworms, Ancylostoma duodenale and the
Necator americanus, both of which share the same four stages in the life cycle eggs,
rhabditiform larvae, filariform larvae, and adults. The eggs of the two hookworms vary only in
size. The rhabditiform larva is the immature, newly hatched larva. It is an actively feeding form
that consists of a long oral cavity called buccal cavity or buccal capsule, and a small genital
primordium. The filariform larvae is the non-feeding, infective larva that has a distinct pointed
tail. The adult worms of the two hookworms are differentiated by the appearance of their
buccal capsule. The N. americanus buccal capsule is equipped with a pair of cutting plates while
that of Aduodenale consists of teeth.
Ancylostoma duodenale (Old World Hookworm) and Necator americanus (New World
Hookworm)

Ancylostoma duodenale (Old World Hookworm) and Necator americanus
(New World Hookworm)
Unlike the other intestinal roundworms, the infective stage for hookworms is the larva
and transmission through skin penetration by the filariform larva. The feet or legs are
the usual sites of penetration. After penetration, the larvae are carried by the blood to
the lungs, migrate to the air sacs, pass up the bronchi and trachea, are coughed up and
then swallowed with sputum, imilar to the larval migration phase of Ascaris
lumbricoides. Once in the small intestines, the larvae mature into adult worms and
attach themselves to the intestinal wall using their Mating occurs in the small intestines,
where thousands of eggs are laid each day. The eggs are cutting plates or teeth. The
adult worms feed on blood from the capillaries of the intestinal villi. then passed out
with the feces.
Ancylostoma duodenale (Old World Hookworm) and Necator americanus (New World Hookworm)

Hookworms are found worldwide, especially in tropical countries. Walking barefoot on soil puts one
at risk of acquiring the infection. Irritation of the skin at the site of penetration may be seen, as well
as inflammatory reactions in the lungs during the larval phase. The major damage to the host is due
to chronic blood loss at the site of attachment in the small intestines.
Disease: Hookworm Infection
Penetration of the skin by the filariform larvae produces a pruritic papule or vesicle This is called
"ground itch." Pneumonia with eosinophilia may occur during the lung phase. The presence of
adult worms in the intestines can manifest nausea, vomiting, and diarrhea As the worm feeds on
blood, a microcytic, hypochromic anemia akin to iron-deficiency anemia may occur. Intestinal sites
may be secondarily infected by bacteria.

Stool examination will show the characteristic thin-shelled eggs. Occult blood in the stool and blood
cosinophilia are frequent findings. Peripheral blood smear will show microcytic pochromic anemia.
Larvae may be recovered from sputum.
Treatment
The recommended drugs for treatment are mebendazole and pyrantel pamoate. Iron placement
therapy is recommended for the anemia. In severe cases, blood transfusion may be necessary.
The preventive measures are similar to those for Ascaris lumbricoides and the other intestinal
mundworms. Wearing shoes or any protective footwear is also important, especially in endemic.

Strongyloides stercoralis (Threadworm)
The eggs of Strongyloides stercoralis are similar to those of
except for two larva of Strongyloides differ from that of hookworms in
longer buccal cavity and features-Strongyloides ova are smaller and contain
developed larvae. The rhabditiform A smaller genital primordium. Like
the infective stage is the filariform larva. The 5 stercoralis differs from
filariform larva in that the former has a longer esophagus and a notched
the hookworm filariform larva's tail pointed.

Strongylides stercoralis is unique among the intestinal roundworms for
having two distinct life cycles one within the host and a free-living cycle in soil.
infection through three possible means. The first is through direct skin
filariform larva, as that of hookworm acquisition. This direct mode of
beginning of the human cycle. The direct or human cycle resembles that of the
where a lung phase also occurs. It differs from the hookworm cycle in that it is
rhabditiform larvae that are passed out with the feces instead of the eggs. The
transform directly to the infective filariform larvae in warm, moist soil.
Infection may also occur through autoinfection. This occurs when the
develop into filariform larvae in the intestines of the infected person. These then
lymphatic system or the bloodstream of the infected host, thus starting a new

Threadworn infection occurs worldwide but is more common in tropical,
sub-tropical, and warm, temperate areas. The parasite is frequently seen in
agricultural areas where there is constant contact with soil. As in hookworm
infection, irritation at the site of skin penetration also occurs (ground itch) similar
to a hookworm infection. The larvae in the lungs can produce an inflammatory
reaction similar to Ascaris. The adult worms in the small intestines can initiate an
inflammatory reaction on the intestinal wall, resulting in diarrhea. This is especially
seen in autoinfection, where significant damage can occur in the intestinal mucosa
which may lead to secondary bacterial infection and sepsis.

Disease: Strongyloidiasis (Cochin China Diarrhea)
Patients with light infection are usually asymptomatic. Like hookworm
infection, skin irritation at the site of entry is seen. Migration of the larvae into the
lungs lead to pneumonitis. Just like that of hookworm and dicari infections. The
presence of numerous adult worm in the intestines lead to diarrhea and
abdominal pain. In some patients, the parasite can stimulate recurrent allergic
reactions resulting to urticaria and cosinophilia. In patients with very high worm
burden, which is seen in autoinfection, malabsorption syndrome may occur due to
involvement of the biliary ducts, pancreas, small intestines, and colon.

This can lead to steatorrhea (fat in the stool) and resulting
nutrient deficiencies, epigastric pain and tenderness, and increasing diarrhea.
These symptoms constitute a hyper-infection syndrome. In some instances,
disease presentation is mistaken for peptic ulcer disease. Autoinfection can also
lead to development of chronic infection, increasing the risk of developing hyper-
infection syndrome, which can prove fatal in patients who are
immunocompromised (commonly in patients under corticosteroid therapy or
other immunosuppressive therapies). Aside from the potentially fatal electrolyte
abnormalities, fatal complications of the hyper-infection syndrome include
bacterial sepsis, peritonitis, and endocarditis.

Eggs, although not commonly present, may be recovered from stool of
patients with heavy worm burden who have severe diarrhea. The usual diagnostic
method is through the recovery of Eggs, although the rhabdititorm larva in fresh
stool samples. It is recommended that three sample collections be done, one per
day for three days, as the larvae may occur in "showers with many seen in one.
Examination of duodenal aspirates may also yield the larvae. Larvae may also be
recovered from during the lung phase of the parasite's life cycle. Striking
eosinophilia may occur in a he infection. Serologic tests such as ELISA have already
been developed.

Treatment
The drug of choice for treatment is ivermectin with mebendazole and
thiabendazole as bernative drugs.
Preventive and control measures for Strongyloides are similar to those for
hookworms. These include thorough health education of the population at risk,
proper sanitation and sewage disposal, wearing of protective footwear, and
prompt treatment of infected individuals.

Capillaria philippinensis (Pudoc worm)
The parasite was first described in the Philippines in 1963, when the first human
from the infection. From 1967-1968, outbreaks of the infection occurred leading to the
more than a hundred infected individuals. Unlike the other intestinal roundworms,
eating birds are the natural hosts. Typically, the unembryonated eggs are passed out to the
environment with the feces of the birds or infected humans, usually in fresh water. The
become embryonated and are ingested by freshwater fish (usually bagsit in the Ilocos
larvae encyst in the tissues of the fish. Humans acquire the infection by cating improperly
or raw freshwater fish. Once in the small intestines, the larvae Some of the eggs may
embryonated in the intestines which leads to development mature into adult worms that
into the wall of the intestines, where the worms lay eggs.

Capillaria philippinensis is endemic in the Philippines, especially in the Ilocos region. Cases

Diagnosis is confirmed by demonstration of the characteristic eggs in stool specimens. In
high worm burden, larvae as well as adult worms may also be demonstrated in stool.
Treatment
The drug of choice for treatment is albendazole, with mebendazole as alternative,
especially for adult patients. Chemotherapy is given for atleast 20 days in order to totally eradicated
the parasite.
Preventive measures include adequate and thorough cooking of seafood before
consumption, especially in endemic areas. Other measures include proper human waste disposal,
health education, and prompt treatment of infected persons.

Wuchereria bancrofti (Bancrofti’s Filarial Worm) and Brugia malayi (Malayan Filarial Worm)
W. bancrofti and B. malayi are both mosquito-borne parasites. Both have two important
two important morphologic forms – the adult worm and the larvae (called microfilariae). The adult
male is usually the size of the female worm. Both are thread-like in appearance with creamy white
color. The microfilariae have a delicate transparent covering called a sheath. Migration of the
parasites exhibit periodicity, where the parasite is present in the bloodstream during specific times
of the day, which corresponds to the feeding schedule of the mosquito vector. Migration may occur
at night (nocturnal), during the day (diurnal), or with no clear-cut timing (sub-periodic).
BLOOD-TISSUE NEMATODES

Majority of filarial worm infections worldwide are caused by Wuchereria
bancrofti. Infections in Asia are frequently due to Brugia malayi. In the Philippines,
bancroftian filariasis is more common. Mosquito vectors for W. bancrofti include
Cules spp., Anopheles spp, Aedes spp., and Mansonia spp. The typical vectors for
B. malayi are Mansonia and Aedes mosquitoes. In rural areas in the Philippines,
the major vector is Anopheles minimus falvirostris. In urban areas, the parasite is
transmitted chiefly by Culex spp., which can breed in latrines, sewage, and ditches.

Disease: Filariasis
Symptoms of filariasis may vary depending on the species. The clinical course may
bedivided into three stages asymptomatic, acute, and chronic.

1. Asymptomatic stage - is characterized by the presence of thousands of
microfilariae in the peripheral blood. Adult worms may be found in the lymphatic
system with pat clinical manifestations of Filariasis.

2. Acute stage of infection is marked by fever, with
inflammation of the lymph nodes (lymphadenitis), particularly those of the male
genitalia (in bancroft's filariasis) and of the extremities (due to Brugia). In females,
involvement of the lymphatics of the breast may be seen. Recurrent attacks are
characterized by epididymitis (inflammation of the epididymis), orchitis
(inflammation, of the restes), retrograde lymphanginis, and localized inflammation
of the arms and legs. The acute stage is also called adenolymphangitis. Transient
swellings of subcutaneous tissues may also occur called Calabar swellings.

3. Chronic filariasis develops slowly after several years of infection. Manifestations
include chronic edema and repeated acute inflammatory episodes. The edeau and
fibrosis gradually lead to lymphatic obstruction of the legs and genitalis (especially
the scrotum). The enlarged extremity hardens with loss of skin elasticity producing
elephantiasis. Obstruction of the lymphatics of the tunica vaginalis of the testes
lead to accumulation of edema fluid in the scrotum (called hydrol), Hydrocele,
chronic epididymitis, and lymphedematous thickening of the scrotal skin are
commonly seen in bancroft's filariasis. Deformities resulting from Malayan filariasis

Deformities resulting from Malayan filariasis are not as severe and include
enlargement of the epitrochear, inguinal, and axillary lymph nodes. In more
advanced cases of Malayan filariasis, elephantiasis of one more limbs, usually
involving the area below the knee may occur however the scrotum is rarely
involved.

Examination of Giemsa-stained peripheral blood smear is the diagnostic method of
choice demonstrating the microfilariae. In light infections, the blood specimen
(approx. 1 mL) may be immersed in 10 mL of a 2% formalin solution to lyse the red
blood cells. Optimal sampling collection is at night, especially for species that
demonstrate nocturnal periodicity (usually Wuchereria). The ideal times for
specimen collection are between 9:00 pm and 4:00 am, the peak periods for the
appearance of the mosquito vectors. Antigen detection methods and serologic
tests have been developed as alternative diagnostic methods.

Treatment
The recommended drugs for treatment are diethylcarbamazine (DEC) and
ivermectin in combination with albendazole. Both DEC and ivermectin are effective
in killing the microfilariae, however, higher doses are necessary to kill the adult
worms. Microsurgery may necessary to remove the obstructing parasite from the
lymphatics. Other supportive measures include anti-inflammatory drugs to reduce
the inflammation. The use of elastic bandages or elevation of the involved limbs
may help reduce the size of the involved limb.

PREVENTION AND CONTROL
The WHO Division of Control of Tropical Diseases recommend mass treatment in
demic areas. In the Philippines, a Filariasis Control Program was implemented in
2001 which entailed mass treatment in endemic areas using a combination of DEC
and albendazole This resulted in the elimination of infection in some endemic
areas. Other meamires include the use of mosquito nets and repellents, the use of
insecticides to control the mosquito sectors wearing of protective clothing, and
thorough health education of the population.

Trichinella spiralis (Muscle Worm, Trichina Worm)
Important Life Cycle
There are two important morphologic forms of the parasite-larva and adult wortes.
The larvae have a coiled appearance and encysts in muscle tissues, surrounded by
striated muscle cells called nurse cells. The adult worms are small and rarely
recovered. The usual, natural host is the pig but any mammal can be infected.
Humans are accidental hosts and acquire the infection by ingesting of raw or
improperly cooked pork meat containing the encysted larva.
Intestinal-Tissue Nematode

Important Life Cycle
The larvae are released from the cysts with exposure to gastric acid and pepsin,
after which they invade the mucosa of the small intestines where they mature into
adult worm. After mating, the gravid female "gives birth" to the larvae in the
intestinal submucosa. Among the nematodes, the life cycle of the muscle worm
has no egg stage. The larvae then migrate through the bloodstream and localize to
striated muscles where they undergo encystation.

Infection with T. spiralis is seen worldwide, especially in parts of Europe and the
United States where meat can be eaten raw. Aside from the pig, other animals
that may be infected include deer, bear, walrus, and rodents (rats). The severity
of the symptoms depends on the intensity of the infection. Patients harboring a
hundred or more worms are usually symptomatic. Encystation of the larvae may
lead to inflammation, then granuloma formation, which can later become
calcified.

Trichinosis may be divided into three phases-enteric phase, invasion
phate, and convalescent pore. These correspond to the incubation and intestinal
invasion stage (enteric phase), the larval migration and muscle invasion stage
(invasion phase), and the encystation and encapsulation stage of the larva
(convalescent phase). The enteric or intestinal phase may manifest with diarrhea,
abdominal pain, and vomiting In the invasion phase, potentially any organ with
striated muscles may be the target of the parasite.

Symptoms may include periorbital and facial edema, conjunctivitis, fever, muscle
pain (myalgia), splinter hemorrhages, rashes, and peripheral eosinophilia.
Involvement of the heart can lead to life-threatening myocarditis. During the
convalescent phase, the manifestations start to decline. The disease is self-
limiting, hence full recovery is expected. Rare causes of death art congestive
heart failure and respiratory paralysis.

Definitive diagnosis is done by demonstrating the encysted larvae in muscle
biopsy specimen. Blood examination results include cosinophilia, leukocytosis,
and elevated serum Muscle enzyme levels (lactate dehydrogenase, aldolase,
creatine phosphokinase). Serologic tests are available. False negative results may
be seen during early infection, hence it is often ecessary to perform multiple
tests.

Treatment
The disease is self-limiting and therefore does not require
medication. Supportive mess include bed rest as well as the giving of
analgesics and anti-pyreties to relieve muscle pain and fever.
Corticosteroids may be given for severe infections. Thiabendazole
may be given during the early stages of the disease, especially during
the first week, to kill the adult worms. The d has no effect on the
migrating larvae.

Health education is important in preventing infection. It is also
important to thoroughly and adequately cook meat before
consumption. Freezing meat may also kill the encysted larvae.
Avoidance of feeding pork scraps to hogs may help break the life
cycle of the parasite. Other measures include strict meat inspection
and keeping pigs and other farm animals in rat-free pens.

THE END!
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Chapter 15-NEMATODES(SHAYNE SUNICO).pptx

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