Alaria

Synopsis

CAPC Recommends

• Fecal sedimentations should be used for diagnosis of Alaria in infected dogs or cats.
• Keeping dogs and cats from hunting can prevent fluke infections, such as Alaria.

Species

Dogs and Cats

Alaria

Egg of Alaria recovered by fecal sedimentation from dog, 110x69 µm

Overview of Life Cycle

• Trematodes (flukes) have indirect life cycles that require one or two intermediate hosts to reach their infective stage.
• Alaria are trematodes and adults are in the small intestine of their host. Operculated eggs leave the host via feces. Miracidia hatch from the eggs and enter the snail intermediate host, where they develop into cercariae. Cercariae leave the snail and penetrate the tissue of tadpoles, and are referred to as mesocercariae. If the infected tadpole is ingested by a frog, snake or mouse, the mesocercariae will wait in the tissues for a dog or cat host.
• When the infected frog, snake or mouse is ingested by the dog or cat, the mesocercariae migrates to the lungs, transforms to metacercariae, migrates up the trachea and makes its way to the small intestine, where they mature.
• If the mesocercariae are ingested by a lactating queen, they can migrate to the mammary glands and are transmitted to the puppies/kittens.

Stages

• Adult flukes are 2-4mm long.
• Eggs are large, operculated and 108-116 x 64-76 µm.

Disease

• Severity of disease is proportional to the number of flukes and duration of infection.
• Alaria spp. adults develop in the small intestine and are not usually associated with intestinal illness. However, migration of immature Alaria through the lungs may result in pulmonary hemorrhage and subsequent respiratory compromise.

Prevalence

• Alaria prevalence can vary across the country. A recent study found the parasite in 13.4% of free-roaming cats in Oklahoma.
• Most common in animals that are allowed to hunt.

Host Associations – Transmission between Hosts

• Alaria spp. infections are acquired by dogs and cats via ingestion of a wide variety of intermediate or paratenic hosts (particularly frogs and snakes) that harbor immature flukes.

Prepatent Period – Environmental Factors

• Eggs are found in the feces about 3-5 weeks after ingestion of the mesocercariae.

Site of Infection and Pathogenesis

• Adults of Alaria are present in the small intestine of infected dogs and cats.
• Immature Alaria migrate through the lungs prior to being swallowed and developing into adult flukes in the small intestine.
• When infection levels are high, pulmonary damage and hemorrhage may lead to clinical disease.

Diagnosis

• Eggs can be found in feces by fecal sedimentation. Eggs are dense and rarely float.
• Multiple fecal exams may be necessary.

Treatment

• No drugs are labeled for Alaria, however praziquantel and epsiprantel are often used.

Control and Prevention

• Prevention of predation (hunting) and scavenging activity by confining dogs on a leash or in a fenced yard and keeping cats indoors will limit the opportunity for dogs and cats to acquire infection with trematodes.

Public Health Considerations

• A case of fatal disease associated with systemic infection with Alaria larvae and several cases of ocular infection have been reported following ingestion of undercooked frogs legs.

Selected References

• Bowman DD. Georgis’ Parasitology for Veterinarians. 10ed. Elsevier. 2014.

• Nagamori Y, Payton ME, Duncan-Decocq R, Johnson EM. Fecal survey of parasites in free-roaming cats in northcentral Oklahoma, United States. Vet Par: Regional Studies Report. 2018; 14:50-53.