Fascioloides magna Giant Deer Fluke Different behavior and pathology in different hosts. Fascioloides magna Giant Deer Fluke Deer and Elk (normal hosts)Liver migration, then
matures in thin-walled fibrous cysts connected with bile ducts. (Well tolerated; eggs shed in feces). Fascioloides magna Giant Deer Fluke Cattle, bison and swineLiver
migration, then encapsulation in thickwalled, closed cysts and no eggs are shed! Fascioloides magna Giant Deer Fluke Sheep and goats: extensive, uninterrupted hepatic migration with out
encapsulation; usually fatal; 1 fluke can kill a sheep or goat! Pathology Pathology in C. sinensis and D. dendriticum: distended bile ducts and erosion of epithelium lining, but no secondary pathology like in F. hepatica!
Treatment Praziquantel (except for F. hepatica). Rafoxanide: is the drug of choice for F. hepatica! Diagnosis Look for eggs in feces! But hard to diagnose (why?).
SPURIOUS INFECTIONS! Aquatic Vegetation Water Chestnuts Pickled Fish Digestive Tract Trematodes
Fasciolopsis buski Humans, pigs Orient
Large (7.5 cm) Life cycle similar to Fasciola Pathology and Symptoms
Severity depends on worm burden Irritation Excess mucous secretion Ulceration, hemorrhage, Abscess Obstruction
Chronic diarrhea Sensitization to worm metabolites
Leukocytosis Anemia Eosinophilia Nausea/diarrhea Edema of face and intestinal wall Death Treatment Praziquantel
Epidemiology Who gets infected? Rural to semi-urban areas School age children Prevalence
57% China 25% Taiwan 50% Bangladesh 60% India 10% Thailand
Epidemiology How do you get fasciolopsiasis? Ingest metacercariae Commercially raised aquatic plants Water chestnut
Water caltrop Water hyacinth Water lotus Water lily Watercress Epidemiology
Lack of regulation on food industry Food preparation Sanitation (sewage)
Night soil Pigs Habitat Food Digestive Tract Trematodes FAMILY ECHINOSTOMATIDAE intestinal parasites recognized by their anterior collar of spines. Echinostoma revolutum - Cosmopolitan
parasite of birds and mammals shows low host specificity Human cases? Morphology of Adult Echinostoma revolutum Adults are elongate, up to an inch in length. Characteristic structure
is: their circumoral collar of spines arranged in two rows. 37 spines in E. revolutum. Internal organs are distinct and easy to identify.
Morphology of Adult Echinostoma revolutum Collar of spines around oral sucker uterus Vitellaria
Testes Mehlis gland Ovary Life Cycle of Echinostoma revolutum Parasite shows low host specificity throughout
cycle 1. Adults occur in birds and mammals. 2. Eggs are released via the feces into an aquatic habitat. 3. Miracidia hatch, swim to snail, and penetrate.
Life Cycle of Echinostoma revolutum 4. Sporocysts and rediae occur within snail. Cercariae are released. 5. Cercariae penetrate (2nd intermediate hosts) and encyst as metacercariae.
6. Definitive host is infected by ingesting 2nd intermediate host, metacercariae excyst in stomach, and adults mature in small intestine. Order Plagiorchiformes
Family Troglotrematidae: these are oval thick flukes with a spiny tegument and dense vitellaria. Parasites of lungs, intestine, nasal passages, cranial cavities, and various ectopic locations. Nanophyetus salmincola
Fish Eating Mammal (Birds) Salmonid fish Freshwater Snail
Nanophyetus salmincola Northwest N. America Northeast Asia Crypts of the small intestine
Human infections 98% prevalence in Siberian villages Pathology Nanophyetus salmincola
Salmon poisoning Highly pathogenic Neorickettsia helminthoeca Rickettsia Intracellular bacterium Typhus
Nanophyetus salmincola is a vector for Neorickettsia helminthoeca. Nanophyetus salmincola Disease
High Fever Edema of face Vomiting Diarrhea Death in 10 days to 2 weeks.
Lung Flukes Paragonimus bronchiolar lumen and peribronchial tissues Antigenic Become encapsulated granuloma
Paragonimiasis Paragonimus 9 species in Asia, SubSaharan Africa, Central, North and South America Paragonimus westermani Life cycle of Paragonimus
Paragonimus westermani 1st Int. Host Freshwater snails Streams Rice paddies
Melanoides tuberculata Paragonimus cercaria Paragonimus westermani 2nd Int. Hosts: Potamon Rice Paddies
Eriocheir Streams Larvae develop in brackish water Paragonimus kellicotti Crayfish serve as
2nd IH in North America. Metacercariae are found in the heart. Paragonimus A number of birds and mammals are know to
serve as PH! Guinea pigs are known to serve as PARATENIC HOSTS for Paragonimus spp. in South America! 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 m 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 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.
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 5. Carnivore becomes infected by eating tadpole or paratenic host.
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.
