1. The severity of clinical symptoms largely depends on the degree of infection. When the infection is mild, the sick dog will show symptoms such as anemia, weight loss, poor growth and development, pica, vomiting, diarrhea and other symptoms; when the infection is severe, the sick dog will show loss of appetite or exhaustion, weight loss, pale conjunctiva, anemia, hunched back, mucus and bloody stools or Tarry stool with a putrid smell, and eventually death from extreme exhaustion.

2. The affected dog has heterophilia, loss of appetite or loss of appetite, vomiting, digestive disorders, and alternating episodes of diarrhea and constipation.

3. The feces contains blood, mucus or is black and oily, with a putrid smell.

4. If a large number of larvae invade through the skin, some limbs will be edematous, or symptoms of erosion and ulceration will appear. Sick dogs can develop hookworm dermatitis, causing local redness, itching, pustules, and dermatitis (mainly on the claws and between toes), and may be secondary to bacterial infection, and the trunk may show acanthosis and hyperkeratosis.

5. Intra-abdominal fetal hookworm infection or puppies under 3 weeks old may cause severe anemia or even death.

6. Dogs with chronic infection generally only show weight loss, mild anemia, heterophilia and digestive dysfunction.

7. In a small number of sick dogs, a large number of larvae migrate to the lungs, which can cause pneumonia.

8. The mucous membranes are pale and thin, and the hair is dry and easy to fall off.