Lecture 30: Pseudophyllidian Tapeworms of Dogs & Cats: Overview of Trematodes of Veterinary Importance

What happens when humans ingest tapeworm eggs?

They become an intermediate host and may develop neuro disease

What happens when humans eat tissues containing the infective Cysticercius stage?

They become the definitive host and develop adult tapeworms.

What are key characteristics of Pseudophyllidean cestodes?

Segmented tapeworms with specialized holdfast structures called "Bothria" (slit-like suckers).

Describe the life cycle of Pseudophyllidean cestodes.

They have an aquatic lifecycle requiring two intermediate hosts.

What are the two genera of Pseudophyllidean cestodes with veterinary and public health significance?

Diphyllobothrium and Spirometra mansonoides.

Describe the life cycle of Diphyllobothrium latum.

It has an aquatic, two-host life cycle involving a copepod, a fish, and an endothermic vertebrate (e.g., dog, cat, bear, or other fish-eating mammals).

How can humans acquire Diphyllobothrium latum?

By consuming raw or undercooked fish containing infective larvae.

What zoonotic concern is associated with Diphyllobothrium latum?

It can cause infection in humans.

What nutritional deficiency is associated with Diphyllobothrium latum?

Vitamin B12 deficiency, potentially leading to anemia.

What is the size and appearance of Diphyllobothrium latum eggs?

Gold-brown, operculated eggs measuring 65-75 x 35-45 μm.

What human dietary habits influence the prevalence of Diphyllobothrium latum in the U.S.?

It follows ethnically defined dietary preferences, including Scandinavian, Russian, Finnish, Jewish, Japanese, and Hispanic communities, due to the popularity of fresh, raw, and pickled fish.

What is the reported size of Diphyllobothrium latum tapeworms?

The strobila can reach up to 12 feet in length.

How is Diphyllobothrium latum diagnosed?

Identification of eggs or proglottids in stool samples.

What are the clinical signs of Diphyllobothrium latum infection?

Generally asymptomatic in the GI tract, but B12 deficiency-related disease is well documented.

What is the treatment for Diphyllobothrium latum infection?

Praziquantel 10 mg/kg BW, PO SID, x1 dose.

When and where was Adenocephalus pacificus first described?

In 1931, in a fur seal host.

How was Adenocephalus pacificus reclassified?

It was originally classified under Diphyllobothrium but later reclassified based on molecular and morphological characteristics.

What type of fisheries is Adenocephalus pacificus associated with?

Marine "salt-water" fisheries.

In which countries has Adenocephalus pacificus become a significant source of human outbreaks?

Spain, Chile, Peru, Ecuador, Brazil, and Argentina.

How do humans acquire Adenocephalus pacificus infections?

Through the consumption of chilled raw or undercooked marine fish.

What type of tapeworm is Spirometra mansonoides?

A Pseudophyllidian tapeworm with an aquatic lifecycle and two intermediate hosts.

What happens during the larval stage (plerocecoid) of Spirometra mansonoides?

It multiplies asexually in the second intermediate host.

What are the natural definitive hosts of Spirometra mansonoides?

Canids and felids.

What role do humans play in the life cycle of Spirometra mansonoides?

Humans serve as a second intermediate host, not a definitive host.

What distinguishes the life cycle of Cyclophyllidian tapeworms?

They have an exclusive terrestrial lifecycle with one intermediate host.

What are the typical intermediate hosts of Cyclophyllidian tapeworms?

Endothermic vertebrates

Arthropods (fleas, lice, mites)

What is the exception to the typical lifecycle of Cyclophyllidian tapeworms?

Mesocestoides, which does not strictly follow the single intermediate host rule.

How host-specific are Cyclophyllidian tapeworms?

They are generally host-specific.