Trematodes of Dogs & Cats

Trematodes: General Info

Phylum: Platyhelminthes

Life Cycle: Indirect (1-2 intermediate hosts)

Appearance: flatworms (dorsoventral flattened), symmetrical, 2 suckers, only has a mouth

True or False: Flukes are hermaphroditic.

True

General Life Cycle

1. Adult flukes in definitive host

2. Egg shed without miracidium

3. Miracidium finds a snail

4. Develops in snail

5. Release of cercaria from snail

6. Becomes metacercaria cyst on vegetation OR finds second intermediate host

7. Cercaria become metacercaria in second intermediate host

8. Metacercaria ingested by definitive host

Nanophyetus Salmincola: Common Name, Definitive Host, Intermediate Hosts, Location, Geography, PPP

Common Name: Salmon Poisoning Fluke

Defintive Host: fish-eating mammals (racoons & skunk, canines, bear, otter, etc)

Intermediate Hosts: 1st = fresh water snails; 2nd = salmonid fishes

Location: Small Intestines

Geography: Pacific NW

PPP: 7 days

Why is N. salmincola clinically significant if it does not cause major disease?

It releases Neorickettsia helminthoeca (bacteria) that spreads to lymph nodes and causes severe hemorrhagic enteritis and HIGH mortality (50-90%)

True or False: Survivors of N. Salmincola are immune to reinfection.

TRUEHo

How do you treat N. Salmincola?

Praziquantel (Doxy for 5 days for the bacteria)

True or False: Humans can become infected by N. salmincola but cannot be infected with N. helminthoeca.

TRUE

Platynosum Fastosum: Common Name, Definitive Host, Intermediate Hosts, Location, Geography, PPP

Common Name: Lizard Poisoning Fluke

Definitive Host: Cats

Intermediate Hosts: 1st-terresterial snail; 2nd-terrestrerial isopod; 3rd-lizards

Location: liver & bile ducts

Geography: Tropics, southern US

PPP: 30 days

Why is P. fastosum concerning clinically?

Infected hosts can develop cirrhosis and liver failure from blockages and it is associated with hepatic neoplasia

Heterobilharzia Americana: Common Name, Defintive Hosts, Intermediate Hosts, Location, Geography, PPP

Common Name: Canine Schistosomiasis

Defintive Host: dogs, racoon, mink, horse

Intermediate Host: Snail

Location: Mesenteric Veins

Geography: Gulf Coast states and parts of Midwest

PPP: 60-120 days

True or False: Cercaria of H. americana cannot penetrate skin of their definitive host.

FALSE

What are the most common clinical signs of a dog infected with H. americana?

• hypercalcemia

• formation of granulomas on liver, spleen, kidney

Swimmer’s Itch

schistosome-associated dermatitis in humans from cercaria penetrating skin from the water. It can be caused by H. americana and bird schistosomes

Flukes with Operculated Eggs

• N. salmincola (indistinct)

• P. Fastosum

Flukes with Non-Operculated Eggs

• H. americana