Introduction

• Cause : Trematode infections include Alaria alata, Heterobilharzia Americana, Nanophyetus salmincola,and Paragonimus kellicotti.
• May also be infected by Fasciola hepatica but this is rare in cats and dogs.
• Signs :  Heterobilharzia Americana infection can lead to vomiting, diarrhea, anorexia, weight loss and renal failure. Infection with Nanophyetus salmincola can lead to enteritis or rapid death associated with Salmon poisoning complex. Paragonimus kellicotti infection can lead to coughing, dyspnea, pneumothorax, bronchiectasis, and hemoptysis.
• Diagnosis : clinical signs, trematode eggs in feces or sputum.
• Treatment : Praziquantel, fenbendazole, supportive.
• Prognosis : good with appropriate treatment with the exception of Heterobilharzia Americana where the prognosis is very guarded once clinical signs develop. Although Nanophyetus salmincola is relatively non pathogenic, salmon poisoning complex carries a grave prognosis.

Pathogenesis

Etiology

• Adult trematodes present in the lungs, alimentary system, mesenteric or portal veins.

Predisposing factors

General

• Access to raw or undercooked fish or shellfish. Swimming in water contaminated with cercariae of Heterobilharzia Americana.

Specific

Pathophysiology

• Source of infection for dogs is raw/undercooked fish and shellfish intermediate hosts.
• Young flukes rapidly penetrate the intestinal tract and enter the peritoneal cavity or in the case of  Alaria alata and Nanophyetus salmincola develop to adulthood in the small intestine.
•  Heterobilharzia Americana infection is acquired when swimming cercariae in contaminated water penetrate the skin.
•  Heterobilharzia Americana migration across the intestinal wall can cause severe granulomatous inflammation before subsequent migration through the portal vein to the mesenteric veins.
•  Heterobilharzia Americana infection can lead to secondary glomerulonephritis.
•  Paragonimus kellicotti migrates to the lungs where cysts form containing paired flukes. Eggs are passed in the sputum or coughed, swallowed and passed in the feces.
• Small number of worms well-tolerated.
• Presence of flukes may be associated with villous atrophy, malabsorption, increased thickness of intestinal muscle layers.
• The larger the worm burden the higher the risk of pathology and subsequent clinical signs.

Timecourse

• Pre patent period typically 5-7 weeks.
• Clinical signs may be seen earlier due to immature stages and fluke migration.

Diagnosis

Treatment

Prevention

Outcomes