Do the Worm!

Instructional Guide

Learners will explore different intestinal parasites.

Intended Grade Level

This lesson is intended for college students. Students should be familiar with general anatomy and physiology of the GI system.

Learning objectives

• Students will be able to identify and describe the life cycles, transmission routes, and anatomical locations of common intestinal parasites in dogs and cats

• Students will be able to analyze the clinical signs and health impacts associated with each parasite and explain how these symptoms relate to the parasite’s location and feeding behavior within the gastrointestinal tract.

• Students will be able evaluate and compare diagnostic, treatment, and prevention strategies

Lesson Format

Student page

This can be done in any size group. The material can be printed and disseminated. Activities require a computer and internet access.

• First students will read about different kinds of intestinal parasites, their symptoms and treatment. Afterwards, students will watch a brief video to recap what they read (20 minutes)
• Next, students play a game to match intestinal parasites to their symptoms and treatment in a case-based manner (15 minutes)
• The assessment is a multiple-choice quiz to test their new knowledge (5 minutes)

Lesson Background

Intestinal parasites are organisms that live inside the gastrointestinal (GI) tract of a host and steal nutrients, damaging the host’s health. They can cause a range of symptoms such as weight loss, diarrhea, vomiting, lethargy, anemia, and inability to gain weight. Many parasites are transmitted via the fecal-oral route or through intermediate hosts (like fleas or rodents). Young, growing animals are especially vulnerable.

Whipworms (Trichuris vulpis) are transmitted through ingestion of microscopic eggs from contaminated soil or feces, and settle within an animal’s cecum. Symptoms include bloody diarrhea, lethargy, weight loss, weakness. The best form of treatment is prevention with monthly parasitic prevention, but if infected, treatment includes deworming with medication and giving supportive care.

Tapeworms (Dipylidium caninum) are transmitted through ingesting infected fleas or wildlife carcasses. Symptoms include scooting, rice-like segments in feces, anal irritation, and in severe cases, weight loss. Young animals are at risk for complication such as delayed growth, anemia, and intestinal blockage. Tapeworms are of significant interest due to their zoonotic risk, especially to children. Therefore treatment with deworming targeting tapeworms, and prevention such as flea control, and avoiding wildlife ingestion, is extremely important.

Roundworms (Toxocara spp.) are transmitted through ingestion of eggs from feces, contaminated soil, or prey animals, and settle within the intestines where they feed on partially digested food. Symptoms include a pot-bellied appearance, diarrhea, malnutrition, and growth delays. Roundworms can be see in the stool, looking like spaghetti. Treatment includes deworming every 2 weeks until cleared, and prevention include monthly preventatives, as well as sanitation.

Hookworms (Ancylostoma spp.) are transmitted through oral ingestion or skin penetration, and they settle within the small intestine but can migrate to the lungs.  Areas with warm, humid climates are higher risk for hookworms.  Symptoms include bloody diarrhea, anemia, and respiratory distress if lungs are affected. Treatment includes dewormer, and severe cases may need a blood transufion. Prevention includes monthly preventatives and general hygiene.

Giardia is a protozoan, not a worm,  which are transmitted through the fecal-oral route, especially in high-traffic dog areas (parks, kennels). Reinfection is common due to contamination of fur/environment Symptoms include watery diarrhea, weight loss, dehydration, sometimes vomiting. Treatment includes dewormer (like fenbendazole/metronidazole) and a bath on day 1 and final day of treatment to remove cysts. To prevent giardia it is recommended to keep clean environments, reduce exposure to shared water sources.

Activities

Students will be presented with a case and will be asked to choose which type of worm is the culprit, and what their plan to treat the patient would be. Both questions are multiple choice, so students have the option to pick which worm they think is most appropriate for the clinical presentation. 

Common misconceptions and challenge points

• Students may think that only young animals get intestinal parasites due to their high risk. While young animals are at higher risk, adult animals can still become infected, especially if immunocompromised, stressed, or exposed to contaminated environments.
• Students may expect to see worms in feces, but this is often not the case. Many intestinal parasites (like Giardia or whipworm eggs) are microscopic and require laboratory testing (e.g., fecal flotation, ELISA) to identify.
• Students may think that general monthly preventatives cover all parasites, however, not all preventatives are broad-spectrum. Some cover only heartworms and a few GI parasites; others omit tapeworms or protozoa. Students should learn to read product labels and match preventatives to the most common local risks.

Assessment

The assessment consists of a short multiple-choice quiz which reflects the learning objectives.

Further exploration

Other lessons within this textbook may be interesting for students. Links to some sample lessons are included below:

Got Diarrhea?

Got Worms?