Gastrointestinal Parasites in Dogs (NAVLE Notes)
Gastrointestinal parasites in dogs can lead to a variety of symptoms, ranging from mild discomfort to severe anemia. Here’s an overview of each major type: roundworms, hookworms, whipworms, and tapeworms.
Classic Case
- Roundworms:
- Signs:
- Usually asymptomatic
- Diarrhea, vomiting (adult worms may appear in stool or vomit)
- Poor growth, distended abdomen, dull coat
- Coughing due to migrating larvae (eosinophilic pneumonia)
- Hookworms:
- Signs:
- Anemia, weakness, emaciation, anorexia, poor growth
- Interdigital dermatitis due to cutaneous larval invasion
- +/- Diarrhea and melena (dark, tarry stool)
- Whipworms:
- Signs:
- Often asymptomatic in mild infections
- Weight loss, diarrhea
- +/- Hematochezia, anemia
- Tapeworms:
- Signs:
- Generally asymptomatic
- Proglottids visible on perineum or in feces
- +/- Weight loss, diarrhea
Diagnosis
- Roundworms:
- Etiology: Toxocara canis
- Fecal flotation: Spherical, thick-walled, pitted ova
- Hookworms:
- Etiology: Ancylostoma caninum, sometimes A. braziliense in southeast U.S. or Uncinaria stenocephala in northern U.S.
- Fecal flotation: Thin-shelled, oval ova
- CBC: Normocytic, normochromic anemia progressing to hypochromic, microcytic anemia
- Whipworms:
- Etiology: Trichuris vulpis
- Fecal flotation: Elongated ova with bipolar plugs
- Tapeworms:
- Etiology: Dipylidium caninum (most common), occasionally Taenia spp.
- Observation: Proglottids seen on perineum or in feces; egg packets may not appear on fecal flotation
Treatment
- Roundworms:
- Pyrantel: Administer to puppies as early as 2 weeks old, repeated every 2-3 weeks until 3 months
- Prevention: Pyrantel for pregnant bitches
- Hookworms:
- Pyrantel: Administer to puppies every 3-4 weeks until 3 months old
- Prevention: Regular cleaning of kennels
- Whipworms:
- Fenbendazole: Administered at monthly intervals
- Prevention: Clean, dry environment (whipworm eggs desiccate easily)
- Tapeworms:
- Praziquantel
- Prevention: Effective flea control
Key Points
- Roundworms:
- Zoonotic; T. canis can cause visceral larval migrans in humans.
- Nearly all puppies are born with roundworm infections due to transplacental transmission.
- Life cycle involves migration to the lungs in young puppies before returning to the intestines.
- Hookworms:
- Zoonotic potential with A. braziliense, which can cause cutaneous larva migrans.
- Whipworms:
- No zoonotic concern; transmission occurs via ingestion of infective eggs.
- Tapeworms:
- Zoonotic; intermediate stages of Taenia spp. can affect various organs.
- Transmission mainly through ingestion of infected prey or fleas.
NAVLE-Style Practice Questions on Gastrointestinal Parasites
Question 1
A 2-month-old puppy with a distended abdomen and dull coat presents for evaluation. The owner reports occasional coughing and that the puppy has vomited a few times. Fecal flotation reveals spherical, thick-walled ova. What is the most likely diagnosis?
- A) Hookworm infection
- B) Roundworm infection
- C) Tapeworm infection
- D) Whipworm infection
Correct Answer: B
Explanation: The scenario describes signs consistent with roundworms, including a distended abdomen, coughing, and thick-walled ova on fecal flotation. The coughing is due to larval migration to the lungs, which is common in roundworm infections in puppies.
Question 2
A 4-year-old dog presents with intermittent diarrhea and melena. The dog is underweight and lethargic, and physical examination reveals pale mucous membranes. Fecal flotation shows thin-shelled, oval ova. What is the most likely cause?
- A) Tapeworm infection
- B) Roundworm infection
- C) Hookworm infection
- D) Whipworm infection
Correct Answer: C
Explanation: Hookworm infections cause anemia, melena, and poor body condition. Thin-shelled, oval ova on fecal flotation are characteristic of hookworms, which can cause significant blood loss in severe cases.
Question 3
An owner reports finding small, rice-like segments around their dog’s perineum. The dog is otherwise healthy, with no history of gastrointestinal upset. What is the most likely diagnosis, and what should be recommended?
- A) Whipworm infection; prescribe fenbendazole
- B) Tapeworm infection; recommend praziquantel and flea control
- C) Roundworm infection; administer pyrantel
- D) Hookworm infection; recommend frequent deworming
Correct Answer: B
Explanation: The rice-like segments around the perineum are tapeworm proglottids. Treatment with praziquantel is effective against tapeworms, and flea control is necessary to prevent reinfection, as fleas are intermediate hosts.
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