Paragonimus spp.

Paragonimus westermani Definitive Hosts

Paragonimus kellicotti Definitive Hosts

Chest roentgenogram of a patient with North American paragonimiasis

Pathology and Symptoms Juveniles Asymptomatic Adults Tissue damage Ciliated epithelium Inflammatory response Worms become encapsulated Fibrosis (Granuloma) Fibroblasts, eosinophils, lymphocytes Chest pain, dry cough, rusty sputum, dyspnea etc. Loss of lung function Ectopic infections Eggs Fibrosis

Normal bronchiole Worm pair

Plain skull film of a patient with chronic cerebral paragonimiasis

Diagnosis Look for eggs In ________________ Or in ______________ 85 X 50 μm

Treatment Praziquantel

Epidemiology How do people get infected? Infective stage? Mechanism?

Epidemiology Rice Paddies

STRIGEOID TREMATODES - trematodes that 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 Adult Alaria Body is divided into 2 regions. Three suckers are present Common genital pore is posterior.

Life Cycle of 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 of 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. 5 4

Life Cycle of 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 of Alaria In one species, the mesocercariae can be transmitted to juvenile definitive hosts through the milk of the mother! When a lactating cat ingests mesocercariae, they disseminate throughout the tissues and are transmitted through the milk of the mother to the offspring!

Pathology of Alaria 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?

Frog Legs

Dr. Kevin Kazacos

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

Alaria sp. in bullfrog leg muscles

Pathology of Alaria 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 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) Infect mammals, and birds. Live in the mesenteric veins (most species); some in urinary plexus veins, nasal veins, and dorsal aorta.

Blood Flukes Veins Mesenteric veins Anterior (superior) Small intestine Posterior (inferior) Large intestine Urinary bladder

Schistosoma Small elongate 1-2 cm Dioecious Gynecophoric canal Male helps female eat

Schistosomiasis Major Parasitic disease, with 200-300 million people infected. many are school age children

Schistosomiasis Schistosoma Bilharzia Egyptian papyri Egyptian mummies 1850 Theodor Bilharz Egyptian papyri Egyptian mummies Joshua’s curse on Jericho 1800 Napoleon’s army

Species that infect humans Schistosoma japonicum Anterior mesenteric veins Schistosoma mansoni Posterior mesenteric veins Schistosoma haematobium Veins draining the urinary bladder Schistosoma intercalatum Intestinal schistosomiasis in Africa Schistosoma mekongi Small intestine like S. japonicum (Vietnam)

} Species Schistosoma japonicum Schistosoma mansoni Big three! Anterior mesenteric veins Schistosoma mansoni Posterior mesenteric veins Schistosoma haematobium Veins draining the urinary bladder Schistosoma intercalatum Intestinal schistosomiasis in Africa Schistosoma mekongi Small intestine like S. japonicum (Vietnam) Big three!

Schistosomiasis Estimates 1947: 114,000,000 1968: 118,000,000 1972: 125,000,000 1979: 200,000,000 Current: More than 200,000,000

Why the Increase? Due to irrigation farming and building of dams to facilitate irrigation. Snail habitat has expanded and increases exposure to people.

Life Cycle Schistosomes live in blood vessels that drain tissues such as the bladder, S. intestine and L. intestine. They produce eggs within blood vessels!

Eggs have spines, no operculum, also have prominent secretory glands! S. mansoni S. japonicum S. haematobium

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

Chemical Signaling with arginine Life Cycle Chemical Signaling with arginine Adults can live 20-30 years 3 weeks Release Eggs in 5-8 Weeks

Distribution

Distribution

How do the eggs get out of the body?

How do the eggs get out of the body? Female worm leaves the male and migrates down to lay eggs.

How do the eggs get out of the body? Female worm leaves the male and migrates down to lay eggs. Egg spines help the eggs work their way into the tissue, but the miracidia also produces enzymes.

Granuloma can move with the eggs by peristaltic action. Immune response Granuloma (Eosinophils, macrophages, neutrophils) Granuloma can move with the eggs by peristaltic action.

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