Cestodes 2

What are the species of mesocestoides?

M. Variabilis, M. Corti and M. lineatus

What are the hosts for mesocestoides species?

Dogs, coyotes, raccoons, foxes, and cats

What is the geographic distribution for mesocestoides species?

-Widely distributed but uncommon

-Appears to be more common in the western U.S.

What is the morphology of mesocestoides species?

-4 suckers with an unarmed rostellum

-Mature segments have a mediodorsal uterine pore

What is the first I.H. for mesocestoides species?

Likely a free-living mite or dung beetle (still unknown)

What is the second I.H. for mesocestoides species?

Amphibians, reptiles, birds, and mammals that eat the mite of dung beetle containing a tetrahyridia

What is the 1st metacestode stage for mesocestoides species?

Cysticercoid

When do dogs become a secondary I.H.?

If they consume the infected mite or dung beetle

When do dogs become a definitive host?

If they ingest the tetrathyridia when preying on an infected secondary intermediate host

What condition do dogs get if they consume a mite or dung beetle infected with mesocestoides species?

Peritoneal larval cestodiasis

What is the PPP for mesocestoides species?

2-3 weeks

What is the life cycle of mesocestoides species?

1. Gravid proglottids are shed in feces

2. Oncospheres/proglottids ingested by an unidentified arthropod intermediate host

3. The second intermediate host consumes the arthropod and tetrahydria (infective larval stage) develop in the peritoneal cavity and organs

4. Carnivore definitive host infected after ingesting tetrahthyridia in infected intermediate host

5. Adults in small intestine

What is the diagnostic stage for mesocestoides species?

Gravid proglottids shed in feces

What is the infective stage for mesocestoides species?

Tetrahydria

Where do tetrathydridia live in the secondary intermediate host?

Found free floating and adhered to various surfaces in the peritoneal cavity

How do tetrathyridia reproduce in the secondary intermediate host?

Asexual reproduction

What are the clinical signs of Peritoneal Larval Cestodiasis?

-Abdominal distension (ascites)

-Anorexia and weight loss

-V+ and D+

-Depression

-Fever

-PLC is a life-threatening disease with a guarded prognosis

How is Peritoneal Larval Cestodiasis diagnosed?

-Ascites and other clinical signs

-Demonstration of tetrathyridia in abdominal effusion (whitish, flat, 2-5cm long, invaginated scolex with four circular, well-developed suckers without rostellum and hooks)

-Diagnosis is challenging (there are no parasite stages passed in feces and no serologic tests)

What are the clinical signs of having adult mesocestoides?

-Usually none

-Anorexia

-Loose, mucoid stools with tapeworm segments

How are adult mesocestoides infections diagnosed?

-Observe motile segments in stools or from around perineum (requires correct I.D.)

-Recover eggs in fecal (rarely)

What is the treatment for adult mesocestoides?

Praziquantel

What is the treatment for peritoneal larval cestodiasis?

-Treating tetrathyridia

-Fenbendazole

-Current recommendation is to also conduct open or closed perioneal lavage

-FBZ treatment and lavage significantly increase survival rates

-Recurrence is common

Are mesocestoides species zoonotic?

Humans have become infected with mature adult mesocestoides spp. after ingestion of tetrathyridia in undercooked meat

What are diphyllobothriidea?

False tapeworms

What is the common name for Dibothriocephalus latus?

Broad fish tapeworm

What are the two species of diphyllobothriidea?

-Dibothriocephalus latus

-Spirometra mansonoides

Where are adult Dibothriocephalus latus found?

In the small intestine

What are the definitive hosts for Dibothriocephalus latus?

Dog, fox, bears, human and other fish-eating mammals

What are Dibothriocephalus latus associated with?

Aquatic food chains

What is the geographic distribution of Dibothriocephalus latus?

Found primarily in the great lakes, central canada and Alaska

Where is the common name for Spirometra mansonoides?

Zipper tapeworm

Where are adult Spirometra mansonoides found?

Small intestine

What is the definitive host for Spirometra mansonoides?

Cats, raccoons, dogs, bobcats

What are Spirometra mansonoides associated with?

Aquatic food chains

What is the geographic distribution for Spirometra mansonoides?

Occurs widely but uncommonly in North America; more common in Gulf Coast states

What is the hold-fast organ for Spirometra mansonoides?

Elongated with two bothria (no suckers or hooks)

What do Spirometra mansonoides eggs look like?

Operculated

What is the size of Spirometra mansonoides eggs?

60-65 x 35-40 nanometers

How many intermediate hosts are required for Dibothriocephalus latus?

2

What is the first intermediate host for Dibothriocephalus latus?

Aquatic crustacean (copepod)

What is the secondary intermediate host for Dibothriocephalus latus?

Copepod eaten by a fish (may be two or more fish involved)

How many intermediate hosts are required for Spirometra mansonoides?

Requires 2 intermediate hosts

What is the first intermediate host for Spirometra mansonoides?

Aquatic crustacean (copepod)

What is the secondary intermediate host for Spirometra mansonoides?

Copepod eaten by a frog, water snake, or rodent

What is the life cycle of diphyllobothriidea?

-Operculated eggs are shed in the feces of infected animals

-If operculated eggs reach water, a ciliated larva called a coracidium develops and hatches in the water

-The coracidium develops into a procercoid in the 1st I.H.

-The procercoid develops into a plerocercoid in the 2nd I.H.

What is the PPP for dibothriocephalus latus?

40 days

What is the PPP for Spirometra mansonoides?

15-30 days

What is the pathology and clinical signs of Diphyllobothriidea?

-Adult worms are not very pathogenic in dogs and cats

-The adult worms usually produce no clinical signs

How is Diphyllobothriidea diagnosed?

-Fecal flotation (Eggs can be damaged/degraded during centrifugation)

-Fecal sedimentation (Identification of operculated eggs, easily confused with Trematode eggs, recovery of gravid segments in feces)

What is the difference between dibothriocephalus latus and spirometra mansonoides eggs?

Both are very similar in size but spirometra spp. eggs tend to be narrower at end with operculum

What is the treatment for Diphyllobothriidea?

-No FDA approved products,, but praziquantel can be given at large doses

What is the control for Diphyllobothriidea?

-Prevent ingestion of raw fish or scavenging animals

-Do not feed raw or undercooked vertebrate tissue

Where is dibothriocephalus latus seen in humans?

In countries where the consumption of raw or marinated fish is a frequent practice

What kind of hosts are humans for dibothriocephalus latus?

Definitive hosts

What kind of hosts are humans for spirometra mansonoides?

Humans can serve as paratenic or second intermediate hosts and develop sparganosis (infection with plerocercoids)

What is sparganosis?

Infection with plerocercoids

How do humans acquire sparganosis?

By either drinking water contaminated with infected copepods or consuming the flesh of an under-cooked second intermediate host (often frogs)

Where might spargana migrate to?

-Subcutaneous tissue

-Orbit

-Urinary tract

-Pleural cavity

-Lungs

-Abdominal viscera

-Central nervous system

What symptoms may spargana cause in humans?

-Neurological symptoms including weakness, headache, seizure and blindness