|hookworms in dogs diseases|
hookworms in dogs diseasesetiology. the most common and most pathogenic hookworm of dogs is ancylostoma caninum. other, less pathogenic canine hookworms found in north america are a. braziliense, which can be found in the american tropics and the southern united states, and uncinaria stenocephala, which is distributed in the northern united states and canada.
clinical signs. only a. caninum infestation typically results in clinical illness, because of the amount of blood that it consumes. Puppies with a. caninum infestations are typically pale and weak (from anemia), with bloody diarrhea or melena. other clinical signs include lethargy, anorexia, dehydration, vomiting, and poor weight gain.
Epizootiology and transmission. infective larvae (L3) are typically ingested by puppies and develop directly in the intestinal tract. Ingestion can be from the bitch's milk (transmammary migration occurs with a. caninum), from food or objects contaminated with infective larvae, or from ingestion of a paratenic host. transplacental migration does occur with a. caninum, but to a much lesser extent than is seen with toxocara canis. Larvae can also penetrate intact skin, migrate to the lung via somatic or circulatory routes, and be coughed and swallowed to reach the intestine. The prepatent period is 3 weeks.
Pathologic findings. infected puppies often have severe anemia and eosinophilia. the anemia can be from acute blood loss or can also be iron-deficiency anemia caused by chronic blood loss coupled with limited iron reserves. on gross necropsy, the small-intestinal tract contains worms admixed with intestinal contents containing fresh or digested blood. ulcerative enteritis caused by hookworm attachment is evident on histopathologic examination, and worms with mouthparts embedded in the mucosa can be identified in some sections .
Pathogenesis. the severe pathogenicity of a. caninum is a direct result of its voracious consumption of blood and body fluids. Each adult hookworm can consume 0.01-0.2 ml of blood; thus an extensive infection could deplete a puppy of 20 ml of blood per day, which is approximately 15% of the blood volume of a 2.0 kg animal. In contrast, a. braziliense and U. stenocephala consume 0.001 and 0.0003 ml per worm, respectively.
Diagnosis and differential diagnosis. diagnosis of ancylostomiasis is made by identification of eggs or larvae from fecal samples by either flotation or direct smear. parvovirus should be considered for puppies with bloody diarrhea, and autoimmune hemolytic anemia should be considered in the diagnosis of a young dog with anemia.
Prevention and control. purchase of purpose-bred animals will limit the exposure to hookworm larvae, and effective sanitation programs will easily eradicate the infective larvae. unlike ascarid eggs, hookworm eggs are readily killed by drying, sunlight, or cold; however, they do survive readily in warm, moist environments. monthly administration of milbemycin or ivermectin plus pyrantel pamoate (Heartgard Plus) is recommended for prevention and control of canine ascarid infestation (Hall and Simpson, 2000).