Alaria spp

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Adult Alaria alata

Alaria spp are a relatively common parasitic intestinal fluke of dogs worldwide[1].

Pathogenic species include:

  • Alaria alata[2]
  • Alaria canis[3]

These flukes are small (0.5 - 1.5 mm) and the anterior part of the body is flat, and the posterior part is conical. The eggs are oval, light brown, and fairly large (120 × 65 µm). The life cycle includes freshwater snails (eg, Helisoma spp) as first intermediate hosts. Cercariae emerge from the snails, penetrate tadpoles, and develop into mesocercariae. Frogs, snakes, and mice then acquire infection by eating tadpoles; the mesocercariae transfer to their tissues and remain as this life-cycle stage. Dogs and other definitive hosts become infected by feeding on these animals.

The young flukes migrate through various organs of the definitive host, including the diaphragm and lungs, before reaching the small intestine. Although the flukes are generally considered to be nonpathogenic[4], large numbers may cause pulmonary hemorrhages during migration or enteritis when they mature in the small intestine.

Praziquantel is considered to be the drug of choice for elimination of this parasite.


  1. Gaunt MC & Carr AP (2011) A survey of intestinal parasites in dogs from Saskatoon, Saskatchewan. Can Vet J 52(5):497-500
  2. Bružinskaitė-Schmidhalter R et al (2012) Helminths of red foxes (Vulpes vulpes) and raccoon dogs (Nyctereutes procyonoides) in Lithuania. Parasitology 139(1):120-127
  3. Bridger KE & Whitney H (2009) Gastrointestinal parasites in dogs from the Island of St. Pierre off the south coast of Newfoundland. Vet Parasitol 162(1-2):167-170
  4. Papazahariadou M et al (2007) Gastrointestinal parasites of shepherd and hunting dogs in the Serres Prefecture, Northern Greece. Vet Parasitol 148(2):170-173