-do- Man, wildcats, foxes, wolves, dogs, rats, pigs, weasels 178 Concise Book of Medical Laboratory Technology: Methods and Interpretations TABLE 8.12: Fluke diseases of man Disease and etiology Clinical features Laboratory diagnosis

 

Methods and Interpretations

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 as completion of worm development and microfilariae production required. Diagnosed by clinical signs, eosinophilia (3000 or more absolute count, usually over 35%), high hemagglutination or complement fixation titer that drops following Heterazan therapy, elevated ESR, mottled lung lesions visible under X-ray

Medical Parasitology 163

The Filarial Worms

164 Concise Book of Medical Laboratory Technology: Methods and Interpretations Wuchereria bancrofti

Medical Parasitology 165

(Filarial Worms)

166 Concise Book of Medical Laboratory Technology: Methods and Interpretations Dracunculus medinensis (The Guinea Worm)

Medical Parasitology 167

Tapeworms of Man (Tables 8.9 and 8.10)

TABLE 8.9: Tapeworms of man

Diphyllobothrium latum, 80–100% in highly endemic areas; Taenia saginata commonest of the large tapeworms; Hymenolepis nana, probably

quite common. Echinococcus granulosus, 3–16% in some endemic areas; Taenia solium, where pork is eaten raw.

Parasite and

distribution

Infection Cycle in

intermediate route

Host fate Cycle in definitive

maturation

of worm

Host exit Summary of

hosts

Taenia saginata

(beef tapeworm)

worldwide

Ingestion of

egg (cattle)

Egg hatches

in intestine;

Oncosphere

released,

penetrates

intestine, enters

bloodstream of

vertebrate

Encysts in muscles

or organs, forms a

Cysticercus larva

(bladder worm)

in cattle called

Cysticercus bovis

Man ingests

cysticercus in raw

beef: scolex attaches

to duodenum,

becomes adult in 6–12

months

Gravid

segments

per anus

Definitive: Man

Intermediate;

Cattle buffalo,

giraffes. llamas,

goats

Taenia solium

(pork tapeworm)

worldwide

Ingestion of

egg (hogs,

man);

autoreinfection

-do- Similar to

T. saginata,

cysticercus larva

(in hogs) called C.

cellulosae

As for T. saginata, but

infection source is

undercooked pork

-do- Definitive: Man

Intermediate:

Pigs, man

(autoreinfection)

Echinococcus

granulosus

(hydatid worm)

Sheep raising

areas

Ingestion of

egg (sheep,

accidental

ingestion in

man)

-do- Forms hydatid cyst

with thousands of

infective scoleces

in fluid, although

cysts may also be

sterile. Chiefly in

liver, also in lungs

rarely in brain

Sheep, dogs ingest

hydatid sand (infective

scoleces) from hydatid

cyst in sheep carcass

Worms attach to

canine intestinal wall;

become adult

Eggs in

feces

Definitive: Dogs,

all canids;

rarely cats.

Intermediate:

Sheep, hogs,

cattle, man

Hymenolepis nana

(dwarf tapeworm)

 worldwide

Ingestion of

egg by man or

rodent (direct

cycle) or by

various insects

(indirect cycle)

Egg hatches

in intestine;

oncosphere

released. In man,

it invades villus; in

insect it penetrates

gut and enters

hemocoel

Cysticercoid larva

containing scolex of

future adult worm,

formed either in

villus of human

host or hemocoel of

insect

In man, larva leaves

villus, attaches to small

intestine, becomes

adult. If infected insect

ingested, cysticercoid

digested out, hatches,

attaches, grows to

adult in 10–12 days

Cysticercoid derived

either from insect or

direct egg-to-cercoid

cycle in man can

produce infection

Eggs in

feces

Man, rats and

mice, gerbils in

Africa. Common

tapeworm of

man; possibly

distinctive strain

in man and

rodents

Diphyllobothrium

latum

(fish or

broad tapeworm)

Orient, Latin

America, Great

Lakes, Northern

Europe

Water flea

ingests

swimming

embryo

(coracidium)

hatched from

egg in water

Hooked embryo

penetrates gut

wall, develops into

procercoid larva in

hemocoel

Freshwater fish eats

water flea; larva

digested out in

intestine, penetrates

to muscles or

organs, becomes

third stage larva

(plerocercoid or

sparganum)

Man ingests fish with

sparganum; larva

liberated in intestine,

attaches to intestinal

wall, becomes adult

Eggs in

feces into

water

Definitive: Fisheating mammals

Intermediate:

Water fleas

(Diaptomus),

then various

freshwater fish

168 Concise Book of Medical Laboratory Technology: Methods and Interpretations TABLE 8.10: Tapeworm diseases of man

Disease and etiology Clinical features Laboratory diagnosis

Hymenolepiasis

Hymenolepis nana

Symptomless to systemic toxemia depending on worm load

Eosinophilia, nervous manifestations, with or without diarrhea,

and pain. Heavy worm load, probably following autoreinfection,

may produce convulsions, insomnia, dizziness

Feces: Direct smear or concentration to

show eggs

Teniasis saginata

Taenia saginata

Abdominal and hunger pains, chronic indigestion, weight loss,

persistent diarrhea or alternating with constipation; nervous

manifestations. Eosinophilia

Feces: Not reliable. Recovery of gravid

segments which actively crawl from

anus; can be found in underwear or bed

linen. Segments or eggs may be rare in

feces

Teniasis solium

Taenia solium

Intestinal: Same as T. saginata. Cysticercosis: Symptoms may

vary with number of larvae and site in tissues. Foreign body

response and inflammation, followed by fibrosis and necrosis of

parasite, later calcification. Shows affinity for CNS, symptoms

resemble brain tumor, epilepsy, and other disorders. Chief sites:

Subcutaneous tissues, eye, brain

Feces: Recovery of gravid segments

Recovery of larvae by biopsy from

infected tissue. Detection of calcified

larvae by X-ray

Hydatid disease

Echinococcus granulosus

E. multilocularis

E. granulosus produces unilocular cysts, 80–90% in liver and

lungs. The host becomes sensitized following escape of fluid

through fissures

Pressure symptoms. Anaphylactic shock may occur upon

rupture. Cachexia results from secondary metastases, pulmonary

or cerebral emboli may occur. Manifestations resemble

cholelithiasis or renal, hepatic or intestinal colic, sometimes

of long standing. E. multilocularis produces uncontrolled,

untreatable metastases in liver with final destruction of most of

parenchyma

Cyst contents in urine. Sputum: Direct

smear

Serology: Complement fixation,

bentonite flocculation, hemagglutination,

intradermal tests. X-rays for pulmonary

cysts or calcified cysts elsewhere

Clinical history and picture of great

value

Diphyllobothriasis (fish

tapeworm disease);

Diphyllobothrium latum

Symptomless to systemic toxemia. Pain, Weight loss, diarrhea,

eosinophilia. Severe macrocytic anemia, similar to pernicious

anemia, found in some cases. Worm competes with host for

vitamin B12

Feces: Direct smear or concentration to

show eggs

Medical Parasitology 169

Cestoda

Cyclophyllidean Tapeworms of Man

170 Concise Book of Medical Laboratory Technology: Methods and Interpretations Taenia solium (The Pork Tapeworm)

Medical Parasitology 171

Taenia saginata (The Beef Tapeworm)

172 Concise Book of Medical Laboratory Technology: Methods and Interpretations Echinococcus granulosus (Causing Hydatid Disease)

Medical Parasitology 173

Dwarf Tapeworm Hymenolepis nana

Hymenolepsis diminuta

174 Concise Book of Medical Laboratory Technology: Methods and Interpretations (Cestoda)

Medical Parasitology 175

Cestoda (General Morphology)

Contd...

176 Concise Book of Medical Laboratory Technology: Methods and Interpretations Contd...

Medical Parasitology 177

Flukes of Man (Tables 8.11 and 8.12)

TABLE 8.11: Flukes of man

Parasite and

distribution

Definitive host Intermediate host cycle

outside man

Reservoir host

Enters man Habitat Exit

Schistosoma

haematobium

Middle East, Africa,

Egypt is classical focus

Cercaria

penetrates skin

Vesical and pelvic venous

plexuses draining urinary

bladder

Terminal spined large

egg in urine or feces

(rare)

Egg hatches to release

swimming miracidium in

water. Invades appropriate

snail (Clonorchis egg ingested

by snail)

Man, monkeys

Schistosoma mansoni

Africa, Latin America,

Carribean Islands

-do- Branches of inferior

mesenteric veins draining

rectum and sigmoid colon

Lateral spined large

egg in feces

In snail tissues each

miracidium becomes a

sporocyst, which forms

a number of embryos

(sporocysts or rediae,

depending on species)

which in turn produce many

cercariae

Man, baboons

monkeys,

Possums, wild rats

Schistosoma

japonicum

Japan, East Asia,

Philippine Islands

-do- Same as for S. mansoni but

occurs chiefly in superior

mesenteric veins draining

small intestine

Round small spined

eggs in feces

Cercariae swarm from snail Man, horses, pigs,

sheep, goats,

cows, dogs, cats,

water-buffaloes,

rodents

Fasciolopsis buski

East and South Asia

Ingested

metacercaria on

water plant or

other vegetation

Small intestine, attached to

intestinal wall

Encyst on water plants

(Fasciola and Fasciolopsis)

or invade fish (Clonorchis)

crayfish or crab

(Paragonimus) or directly

penetrate human skin

(Schistosoma)

Man, pigs

Fasciola hepatica

Worldwide, sheep and

cattle raising areas

Major bile ducts after

migrating from intestine

through peritoneal

cavity, liver capsule, and

parenchyma

Egg in bile to feces -do- Sheep, cattle, other

herbivores, man an

accidental host

Clonorchis sinensis

South Asia,

immigrants in

America

Ingested

metacercaria in

raw fish

Bile ducts migrating from

intestine through ampulla

of Vater

-do- -do- Man, dogs,

cats, fish-eating

mammals

Paragonimus

westermani

Ingested

metacercaria in

crayfish, crab

Encysted in lungs, pleural

and peritoneal cavities, liver,

migrating from intestine

through peritoneal cavity

Egg in sputum or

feces

-do- Man, wildcats,

foxes, wolves,

dogs, rats, pigs,

weasels

178 Concise Book of Medical Laboratory Technology: Methods and Interpretations TABLE 8.12: Fluke diseases of man

Disease and etiology Clinical features Laboratory diagnosis

Schistosomiasis or

bilharziasis

Schistosoma

haematobium

mansoni

japonicum

Initial: Skin penetration by cercariae producing itching,

erythema, petechiae, usually a hypersensitization following

repeated exposures. Eosinophilia in later case, with fever

Maturation of worms: Fever, hepatomegaly with

tenderness, edema, diarrhea; eosinophilia variable.

Adult worms: Systemic and histologic changes mainly due

to granulomatous reaction against eggs acting as foreign

bodies. Symptoms vary with duration, frequency, and

severity of exposure and degree of host reaction, itself

related to age, nutrition and concurrent infections.

Generally with bowel and vesical disturbances, lasting

for months to years. Chronic disturbances: Portal

hypertension with resulting esophageal varices; liver and

intestinal or bladder granulomata and fibrosis

Thickening and calcification in bladder wall

(S. haematobium), thickening of small intestine (S.

japonicum), prolapse of rectum (S. mansoni), loss of gut