Paragonimus spp.. Paragonimus westermani Definitive HostsDefinitive Hosts

Paragonimus Paragonimus spp.spp.

Paragonimus westermaniParagonimus westermani

• Definitive HostsDefinitive Hosts

• Definitive HostsDefinitive Hosts

Paragonimus kellicottiParagonimus kellicotti

Pathology and SymptomsPathology and Symptoms• JuvenilesJuveniles

– AsymptomaticAsymptomatic• AdultsAdults

– Tissue damageTissue damage• Ciliated epitheliumCiliated epitheliumInflammatory responseInflammatory response• Worms become encapsulatedWorms become encapsulated• Fibrosis (Granuloma)Fibrosis (Granuloma)

– Fibroblasts, eosinophils, Fibroblasts, eosinophils, lymphocyteslymphocytes

– Chest pain, dry cough, rusty Chest pain, dry cough, rusty sputum, dyspnea etc.sputum, dyspnea etc.

– Loss of lung functionLoss of lung function– Ectopic infectionsEctopic infections

• EggsEggs– FibrosisFibrosis

Normal bronchiole

Worm pair

DiagnosisDiagnosis

• Look for eggsLook for eggs• In ________________In ________________• Or in ______________Or in ______________

85 X 50 μm

TreatmentTreatment

• PraziquantelPraziquantel

EpidemiologyEpidemiology

• How do people get infected?How do people get infected?– Infective stage?Infective stage?– Mechanism?Mechanism?

EpidemiologyEpidemiology

• Rice PaddiesRice Paddies

STRIGEOID TREMATODES - trematodes that STRIGEOID TREMATODES - trematodes that inhabit the small intestine of birds and mammals inhabit the small intestine of birds and mammals

  Alaria spp. 

Many species of Alaria occur in the small intestine of carnivores.

Alaria canis in dogs.

Alaria americana in foxes.

Alaria mustelae in mink and weasels.

Alaria taxideae in badgers  

Morphology of AdultMorphology of Adult Alaria Alaria

Body is divided into 2 regions.

Three suckers are present

Common genital pore is posterior.

Life Cycle ofLife Cycle of Alaria Alaria LIFE CYCLE is unusual in

that 3 or 4 hosts may be involved.

 1. Adults in small intestine of carnivore definitive host.

 2. Eggs in feces hatch in water releasing miracidia that penetrate snail first intermediate host.

 3. Cercariae released from snail penetrate a tadpole second intermediate host and transform into an unencysted stage called the Mesocercaria.

1

2

3

Life Cycle ofLife Cycle of Alaria Alaria

4. If tadpole is eaten by frogs, snakes, or mice the mesocercariea can serve in these peratenic hosts and mesocercariae undergo no further development. 

5. Carnivore becomes infected by eating tadpole or paratenic host. 4

5

Life Cycle ofLife Cycle of Alaria Alaria 6. The mesocercariae penetrate the intestine, burrow through the diaphragm, and reach the lungs. Here they become metacercariae.

7. Metacercariae migrate up the respiratory tree and are swallowed.

Adults in the carnivore's intestine. 

6 & 7

Life Cycle ofLife Cycle of Alaria Alaria

• In one species, the mesocercariae can be In one species, the mesocercariae can be transmitted to juvenile definitive hosts transmitted to juvenile definitive hosts through the milk of the mother!through the milk of the mother!

• When a lactating cat ingests mesocercariae, When a lactating cat ingests mesocercariae, they disseminate throughout the tissues and they disseminate throughout the tissues and are transmitted through the milk of the are transmitted through the milk of the mother to the offspring!mother to the offspring!

Pathology ofPathology of Alaria Alaria infections infections

• PATHOLOGY - Adult parasites cause severe damage to the small intestine of the carnivore.

• HUMAN INFECTION – few cases involved infection with mesocercariae!– Most cases involved mesocercariae

• We had two cases in Asian American men from Chinatown in San Francisco!  

What did they eat?What did they eat?

Frog LegsFrog Legs

Dr. Kevin KazacosDr. Kevin Kazacos

BullfrogBullfrog

Over 70% of them were infected with Alaria sp.!

Alaria Alaria sp. in bullfrog leg musclessp. in bullfrog leg muscles

Pathology ofPathology of Alaria Alaria infections infectionsPATHOLOGY - Adult parasites cause severe damage to the small intestine of the carnivore.

HUMAN INFECTION – few cases involved infection with mesocercariae!

• Most cases involved mesocercariae migrating to the eye

• One fatal case occurred in Canada from ingestion of poorly cooked frogs!

• Mesocercariae were identified in nearly every organ at autopsy.

• Photo shows mesocercaria in lung.

Blood Flukes (Schistosomes)Blood Flukes (Schistosomes)

• Infect mammals, and birds. Infect mammals, and birds.

• Live in the mesenteric veins (most species); Live in the mesenteric veins (most species); some in urinary plexus veins, nasal veins, some in urinary plexus veins, nasal veins, and dorsal aorta. and dorsal aorta.

Blood FlukesBlood Flukes

• VeinsVeins

• Mesenteric veinsMesenteric veins

– Anterior (superior)Anterior (superior)

• Small intestineSmall intestine

– Posterior (inferior)Posterior (inferior)

• Large intestineLarge intestine

• Urinary bladderUrinary bladder

SchistosomaSchistosoma

• Small elongate 1-2 cmSmall elongate 1-2 cm

• DioeciousDioecious

• Gynecophoric canalGynecophoric canal

• Male helps female eatMale helps female eat

SchistosomiasisSchistosomiasis

• Major Parasitic disease, with 200-300 Major Parasitic disease, with 200-300 million people infected. million people infected.

– many are school age childrenmany are school age children

SchistosomiasisSchistosomiasis

• SchistosomaSchistosoma

• BilharziaBilharzia– 1850 Theodor Bilharz1850 Theodor Bilharz

• Egyptian papyriEgyptian papyri

• Egyptian mummiesEgyptian mummies

• Joshua’s curse on JerichoJoshua’s curse on Jericho

• 1800 Napoleon’s army1800 Napoleon’s army

Species that infect humansSpecies that infect humans• Schistosoma japonicum Schistosoma japonicum

– Anterior mesenteric veinsAnterior mesenteric veins

• Schistosoma mansoniSchistosoma mansoni– Posterior mesenteric veinsPosterior mesenteric veins

• Schistosoma haematobiumSchistosoma haematobium– Veins draining the urinary bladderVeins draining the urinary bladder

• Schistosoma intercalatum Schistosoma intercalatum – Intestinal schistosomiasis in AfricaIntestinal schistosomiasis in Africa

• Schistosoma mekongiSchistosoma mekongi– Small intestine like Small intestine like S. japonicumS. japonicum (Vietnam) (Vietnam)

• Schistosoma japonicum Schistosoma japonicum – Anterior mesenteric veinsAnterior mesenteric veins

• Schistosoma mansoniSchistosoma mansoni– Posterior mesenteric veinsPosterior mesenteric veins

• Schistosoma haematobiumSchistosoma haematobium– Veins draining the urinary bladderVeins draining the urinary bladder

• Schistosoma intercalatum Schistosoma intercalatum

– Intestinal schistosomiasis in AfricaIntestinal schistosomiasis in Africa

• Schistosoma mekongiSchistosoma mekongi

– Small intestine like Small intestine like S. japonicumS. japonicum (Vietnam) (Vietnam)

SpeciesSpecies

Big three! }

Schistosomiasis EstimatesSchistosomiasis Estimates

• 1947: 114,000,0001947: 114,000,000

• 1968: 118,000,0001968: 118,000,000

• 1972: 125,000,0001972: 125,000,000

• 1979: 200,000,0001979: 200,000,000

• Current: More than 200,000,000Current: More than 200,000,000

Why the Increase? Why the Increase?

• Due to irrigation farming and building of Due to irrigation farming and building of dams to facilitate irrigation.dams to facilitate irrigation.

• Snail habitat has expanded and increases Snail habitat has expanded and increases exposure to people. exposure to people.

Life CycleLife Cycle

• Schistosomes live in blood vessels that drain Schistosomes live in blood vessels that drain tissues such as the bladder, S. intestine and tissues such as the bladder, S. intestine and L. intestine.L. intestine.

• They produce eggs within blood vessels!They produce eggs within blood vessels!

Eggs have spines, no operculum, also Eggs have spines, no operculum, also have prominent secretory glands! have prominent secretory glands!

S. mansoni S. japonicum S. haematobium

EggsEggs

• Eggs are shed to outside through excrement Eggs are shed to outside through excrement (feces or urine).(feces or urine).

Life CycleLife CycleChemical Signaling

with arginine

3 weeksRelease Eggs in

5-8 Weeks

Adults can live 20-30 years

DistributionDistribution

DistributionDistribution

How do the eggs get out of the body?How do the eggs get out of the body?

How do the eggs get out of the body?How do the eggs get out of the body?

• Female worm leaves the Female worm leaves the male and migrates down male and migrates down to lay eggs.to lay eggs.

How do the eggs get out of the body?How do the eggs get out of the body?

• Female worm leaves the Female worm leaves the male and migrates down male and migrates down to lay eggs.to lay eggs.

• Egg spines help the eggs Egg spines help the eggs work their way into the work their way into the tissue, but the miracidia tissue, but the miracidia also produces enzymes. also produces enzymes.

• Immune responseImmune response• GranulomaGranuloma

– (Eosinophils, (Eosinophils, macrophages, macrophages, neutrophils)neutrophils)

• Granuloma can Granuloma can move with the eggs move with the eggs by peristaltic action.by peristaltic action.

SchistosomiasisSchistosomiasis

• Big picture the key to schisto pathology is Big picture the key to schisto pathology is the eggs not the adult worms!the eggs not the adult worms!