PARASITOLOGY LECTURE 7 – Flukes (Lungs and Intestines)Notes from Belizario,V.Y, Malte,B.I., Tiu,W.U.USTMED ’07 Sec C – AsM

PARAGONIMUS WESTERMANI (Oriental Lung Fluke) main species that causes human paragonimiasis in

the Philippines (P.philippinenesis and P.siamensis [cats] also cause this disease)

patients often complain of cough and hemoptysis, clinical manifestation consistent with pulmonary tuberculosis (PTB); patients with this parasitic infection are often misdiagnosed with PTB

DISEASE Paragonimiasis (lung fluke disease, or pulmonary

distomiasis or endemic hemoptysis or parasitic hemoptysis)

MORPHOLOGY1. Adult

- Color: reddish brown- Dimensions: 7-

12mm x 4-6mm x 3.5-5mm (lwt)

- Shape: resembles coffee bean; round anteriorly, tapers posteriorly

- Integument: covered with single spaced spines

- Reproductive organs: o 2 lobed testes opposite each other

midway between ventral sucker and posterior border

o ovary anterior to testes and posterior to ventral sucker; w/ six unbranched lobes

- other: vitellaria extensively branched2. Cercaria

- covered with spines- has ellipsoidal body and a small tail- stylet present at dorsal side of oral sucker

3. Metacercaria- round- measures 381-457 um.

4. Egg- Color: yellowish-brown- Shell: thick- Shape: oval- Operculum: flattened but prominent

operculum- Aboperculum: thickened- Unembryonated at oviposition- Dimensions: 80-118um x 48-60 um

LIFE CYCLE Adult worms

- Found in pairs or in threes in fibrotic capsules or cysts in lungs of the host

- Capsules have openings that allow eggs to escape into the respiratory tract where they are moved up and out by ciliary epithelium along with lung exudates

- In the pharynx, are either coughed out or swallowed into the alimentary canal and

passed out with feces

Eggs- immature egg embryonates in water, moist

soil or leached feces

Miracidium- develops from eggs w/in 2 to 7 weeks- it pushes the operculum and swims in search

of an appropriate snail host- 1st intermediate host: Antemelania

asperata and Antemelania dactylus

Sporocyst and Redia- inside the snail the miracidium passes

through one sporocyst and 2 redial stages

Cercaria- cercariae emerge from the snail to seek a 2nd

intermediate host- 2nd intermediate host: mountain crab

(Sundathelphusa philippina)

Metacercaria- The cercaria penetrates the soft parts of the

crustacean and encysts as a metacercaria in the gills, body muscles and viscera or legs

- crab may also be infected by eating infected snails

- Infective stage: metacercaria- Definitive host: Man

Adolescent worm- following ingestion, the metacercaria excysts

in the duodenum- it traverses the intestinal wall, into the

peritoneal cavity where it wanders and embeds itself in the abdominal wall for several days

- parasite returns to the coelom, migrates throught the diaphragm to the pleural cavity where it penetrates the lungs and develops into adulthood

completion of development in the definitive host is 65 to 90 days

worms persist for as long as 20 years Reservoir hosts: dogs, cats, field rats, rodents

PATHOGENESIS AND CLINICAL MANIFESTATIONS in the lungs, worms provoke a granulomatous

reaction that proceeds to the development of fibrotic encapsulation

within the cyst is a blood-tinged purulent material containing eggs

early stages of infection are asymptomatic in heavy infections, patient may suffer from dry

cough and later produce bloodstained or rust-colored sputum with foul fish odor (pronounced in the morning)

Symptoms: chest pains, dyspnea, hemoptysis, low-grade fever, fatigue, myalgia

often misdiagnosed for PTB symptoms less severe after five to six years complications:

- lodge in abdominal wall, abdominal cavity, mesenteric lymph nodes, omentum, pericardium, myocardium and intestinal wall causing erratic paragonimiasis

- cerebral involvement most serious and may cause:o Jacksonian epilepsyo Cerebral hemorrhageo Edemao Visual disturbanceso Meningitis

prognosis with light infection is good and chemotherapy has a high cure rate

DIAGNOSIS based on detection of characteristic eggs in

sputum, stool, or less frequently, aspirated material from abscesses or pleural effusions

serology helpful; standard test is complement fixation (CF) – has advantage to detect rapid decline in antibody levels

EIA and Immunoblot (IB)

TREATMENT *Praziquantel; higher doses required in ectopic

paragonimiasis Bithionol (alternative) Triclabendazole also effective

EPIDEMIOLOGY global distribution in freshwater crabs major endemic areas: Asia (Japan, South Korea,

Thailand, Taiwan, China and Phil.)

PREVENTION AND CONTROL Proper food preparation; the usual….

FASCIOLOPSIS BUSKI (intestines)

a digenetic trematode that parasitizes intestines of humans and pigs

mode of transmission is by ingestion of encysted metacercariae on aquatic plants or when the hull or skin of the fruits of these plants is peeled off between the teeth (?)

DISEASE Fasciolopsiasis

MORPHOLOGY1. Adult

- Dimensions: 20-75mm x 8-20mm (lw)

- Shape: elongated, oval- Reproductive organs:

o 2 testes are dendritic and arranged in tandem in the posterior half

o branched ovary lies to the right of the midline

- other: o vitellaria (fine)o does not have a cephalic

cone and intestinal ceca are unbranched and reach up to posterior end (as compared to F.hepatica and F.gigantica)

2. Egg - Indistinguishable from eggs

of F.hepatica and F.gigantica

- Large and operculated- Unembryonated at

oviposition- Dimensions: 130-140um x 80-85um

LIFE CYCLE

Adult- lives in the duodenum, attached to the

intestinal mucosa by its suckers

Egg- immature eggs are released together with

feces into the water- embryonates in the water and gives rise to

miracidium in three to seven weeks

Miracidium- seeks out 1st intermediate host- 1st intermediate host: snail (genus

Segmentina or Hippeutis)

Sporocyst and Redia- miracidium transforms into sporocyst, which

subsequently produces mother rediae, daughter redia and finally cercaria

Cercaria- leave daughter redia and undergo

development in the snail tissues- cercaria emerge 7 weeks after initial infection- attach themselves on surfaces of seed pods,

bulbs, stems or roots of various aquatic plants- 2nd intermediate host: water caltrop (Trapa

bicornisI), water chestnut (Eliocharis tuberose), water morning glory (Ipomea obscura), and lotus (Nymphaea lotus)

Metacercaria- encyst on the surface of water plants- excysts in the duodenum and attaches to the

intestinal wall where it becomes sexually mature in 3 months

- Infective stage: metacercaria- Definitive host: Pigs and humans

PATHOGENESIS AND CLINICAL MANIFESTION in heavy infections, worms may be found

throughout the intestinal tract and cause obstruction

pathological changes caused by worms are traumatic, obstructive and toxic

inflammation and ulceration occur at site of worm attachement, produces an increase in mucus secretion and minimal bleeding

gland abscesses are occasionally formed intoxication results from absorption of worm

metabolites by host patient experiences generalized toxic and allergic

symptoms such as edema of face, abdominal wall and lower limbs

profound intoxication can cause death

DIAGNOSIS detection of parasite eggs in stool

TREATMENT Praziquantel

EPIDEMIOLOGY endemic in countries of SEA, China, Korea and

India not endemic in the Philippines (yet)

PREVENTION AND CONTROL metacercaria are very sensitive to dryness,

soaking of aquatic plants in water should be avoided (eh? …so hindi na siya aquatic…)

time between harvest and consumption could also be prolonged to prevent infection

washing of plants to remove metacercaria or boiling them can also prevent infection

HETEROPHYID FLUKES (intestines)

heterophyids live in the intestines of fish-eating hosts

major species are Heterophyes heterophyes, Metagonimus yokogawai, Haplorchis taichui and Haplorchis yokogawai

DISEASE mode of transmission is via ingestion of

metacercariae encysted in fish intestinal heterophyidiasis

MORPHOLOGY1. Adult

- Shape: elongated, oval or pyriform- Dimensions: 2mm in length- Integument: fine, scale-like spines- Some species have gonotyl or a genital sucker

that is located near the left posterior border of the ventral sucker

- Reproductive organs:o testes – variously arranged; in the

posterior part of bodyo ovary – globular or slightly lobed; located

submedian, pre- or post-testicular

Metagonimus yokogawai adult Heterophyes heterophyes adult

2. Miracidium- fully developed, symmetrical miracidium is

already present w/in the egg when it is deposited by the adult worm

3. Egg- color: light brown- shape: ovoid- operculated; operculum fits into eggshell

smoothly- does not have abopercular protuberance- dimensions: 20-30 um x 15-17 um

Metagoniums yokogawai egg Heterophyes heterophyes

egg

LIFE CYCLE

life cycle of eterophyes heterophyes

Adult- larva develops into a sexually mature adult

that has a typically short life span of less than one year

- adult worm inhabits the small intestines of the definitive host

Eggs- large numbers of eggs are produced and

passed out with the feces- eggs are ingested by 1st intermediate host- 1st intermediate host: snails (freshwater,

brackish water or marine) Miracidium

- hatches from the egg inside the snail- transforms into a sporocyst

Sporocyst and Redia- sporocyst develops into one or two

generations of redia that give rise to cercaria

Cercaria- liberated form the snail and encyst as

metacercaria on or under the scales in the muscles, fins, tails or gills of fish

Metacercaria- often found in the muscles at the base of the

fin- reaches duodenum and excysts liberating a

young larva that attaches to intestinal wall- 2nd intermediate hosts: In the Philippines there

are 30 species of fish harboring metacercaria

life cycle of Metagonimus yokogawai

PATHOGENESIS AND CLINICAL MANIFESTATION inflammation at the sites where the worm is

attached to or burrowed in the mucosa excessive mucus production and sloughing off of

the superficial layers may occur most common manifestions were consistent with

peptic ulcer disease (PUD) or acid peptic disease (APD)

symptoms: - upper abdominal discomfort/pain- gurgling abdomen- colicky abdominal pain- mucoid diarrhea

In Africa, worms were shown to burrow deep into the intestinal walls and eventually die

o Eggs of degenerating worms may be filtered through the intestinal lymphatics and blood vessels and deposited in various tissues

o Eggs and adults of heterophyids have been observed in the heart and brain of Filipino patients who died of heart failure and intracerebral hemorrhage

o Eggs can be lodged in the spinal cord and may result in sensory and motor losses

DIAGNOSIS it is important to consider intestinal fluke infection

when dealing with bowel disturbance and a history of consumption of raw fish in cases with same presentation as APD

definitive diagnosis: detection of eggs in stool using the Kato-Katz method

hard to distinguish between eggs of heterophyid species

TREATMENT Praziquantel

EPIDEMIOLOGY Egypt, Greece, Israel, western India, Central and

South China, Japan, Korea, Taiwan and the Philippines

worldwide distribution due to the fact that they have adapted to snails belonging to various families and are not very specific with respect to 2nd intermediate hosts

both intermediate hosts may be found in different habitats (fresh, brackish and salt waters) and climates

Reservor hosts: dogs, cats and birds

PREVENTION AND CONTROL avoid ingestion of raw or improperly cooked fish

ECHINOSTOMA ILOCANUM (intestines)

echinostomids are digenetic trematodes characterized by a collar of spines around their oral suckers

several species infect humans (2 in the Philippines E.ilocanum and Artyfechinostomum malayanum)

DISEASE mode of transmission is ingestion of

metacercariae encysted in snails

MORPHOLOGY1. Adults

- Color: reddish-gray- Dimensions: 2.5-6.6mm x 1-1.35mm (lw)- Shape: resembles coffee bean; round

anteriorly, tapers posteriorly- Integument: covered with single spaced

spines- Reproductive organs:

o 2 lobed testes arranged in tandem at the third quarter of the body

o ovary anterior to testes and posterior to ventral sucker; w/ six long unbranched lobes

o other: vitellaria are follicular and

located in the posterior half of the body

tapered at posterior end and has 49-51 collar spines

oral sucker lies in center of circumoral disk

ventral sucker situated at the anterior fifth

uterine coils found between the ovary and ventral sucker

2. Egg - Color: straw-colored- Shape: ovoid- Operculated- Dimensions: 83-116um x 58-

69um

LIFE CYCLE Adults

- once attached to the wall of the S.I., they mature sexually into adult worms

- live in the intestines of definitive hosts- Devinitive host: Man, dogs, cats, rats, pigs

Eggs- released by adult

worms and transported to the environment through the feces

- matures in water

Miracidium - hatches from the egg after 6-15 days

- infects snail- 1st intermediate host: Snail (Gyralus

convexiusculus and Hippeutis umbilicalis)

Redia- No sporocyst stage- develops from the miracidium inside the snail- mother redia produce daughter redia and

cercaria after 42-50 days

Cercaria- escapes from the snail and swims in water- seeks 2nd intermediate host

Metacercaria- Cercaria develops into metacercaria in 2nd

intermediate host- 2nd intermediate host: snail (Pila luzonica

“kuhol” and Vivipara angularis “susong pampang”)

- once ingested, metacercaria excyst and juvenile flukes attach themselves to the wall of the small intestine

PATHOGENESIS AND CLINICAL MANIFESTATION heavy infections – inflammation develops at site of

attachment ulceration and consequently diarrhea (sometimes

bloody) and abdominal pain may develop general intoxication after absorption of

metabolites of worms

DIAGNOSIS detection of eggs in the stool echinostomes, fasciola and buski eggs look very

much alike

TREATMENT Praziquantel

EPIDEMIOLOGY endemic in Northern Luzon, Leyte, Samar and

provinces of Mindanao also in SEA and East Asian countries endemicity is related to eating habits of

population 2nd intermediate host are abundant in rice fields

especially during the wet months Reservoir host : rat

PREVENTION AND CONTROL avoiding ingestion of improperly cooked 2nd

intermediate hosts

-fin-

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