Internal parasites in cattle

Instructional Guide

Learners will explore the life cycle of parasites in an animal and the different parasites found in cattle. The lesson will include activities to check for understanding followed by a self-assessment.

Intended Grade Level

This lesson is intended for 3rd- 5th graders. Prior to the lesson, the students should know what a parasite is and that they can cause various problems if they are too many of them. Students should also be familiar with the general anatomy of the GI system in cattle, such as the esophagus, the four stomach chambers (rumen, reticulum, omasum, abomasum), and intestines. 

Learning Objectives:

By the end of the lesson….

• Students will be able to define what a parasite is and be able to provide examples of different kinds of parasites.
• Students will be able to explain the basic life cycle of a parasite.
• Students will be able to the put the organs of the GI system of a cow in order of the mouth to the anus and name the four chambers of the cow stomach.
• Students will be able to understand the negative effects of parasites in cows and how this relates to physiology.

Lesson Format

Student page

This lesson should take about 50 minutes, this includes time to complete the two check your understandings, one main activity, and a self-assessment. The lesson is designed to be an independent learning session. The teacher should be available to students during the lesson to answer any questions or confusion pops up. The students will want a notebook and writing utensil to take notes and/or work through the activities. They should have access to an iPad or computer to complete the lesson as well as participate in the activities and self-assessment at the end.

Lesson Plan Steps:

1. Students read through the lesson, stopping at knowledge check activities and check your understanding activities (30 minutes)
2. Once students have gone through the lesson, they should read through the “Farmer Jo” cases, working through the case information and answering a question to diagnose the case at the end of each section.  (15 minutes)
3. After making it through the cases, students can take a quick assessment to check what they have learned throughout this lesson. (5 minutes)

Background Activity Information

In order to be prepared for this lesson and the activity in particular, you should be able to explain the order of digestion and the four chambers of the stomach in ruminants (cows) in a way that the age group will understand. 

The cow’s rumen is a fermentation vat designed to digest hay. The rumen houses the microbes that do the actual digesting. Cattle use the microbial by products for energy, rather than the hay. Cows regurgitate in order to make the hay more digestible. After the food is swallowed the first time, larger particles go back up the esophagus and are chewed again (chewing cud).  Once the swallowed hay pieces are small enough and are mostly digested, they move from the rumen (fermentation vat) and reticulum (sorting chamber) into the omasum. The omasum removes the water and dries out the ingesta. The fourth compartment, the abomasum,  is the “true stomach” and digests the grains and fats, just as we do.

You may also want to have additional information available on the parasites in the stories. We have added three different sources; you can find information on all 3 in most of the sites.

• Barber pole worm
• Brown stomach worm
• Stomach hairworm

Activity

For the class activity follow the steps below:

1. Have the students read through each of the three cow cases on Farmer Jo’s farm.
2. Encourage students to jot down signs or significant pieces of each case on a piece of paper.
3. Using the notes the students took the signs Farmer Jo saw, have them compare those to the characteristics and impacts of the three example intestinal worms provided.
4. The students should use everything they’ve noted and learned thus far to help them complete the quiz questions following each case description.
5. Once everyone has the chance to complete all three cases, open the floor for questions or to go over why the answers are what they are.

Common Misconceptions and Challenge Points

• Something we often forget is that parasites can be found both internally and externally. While this may not be an extremely challenging concept, it is more common for us to think parasites are only found internally. This may be a concept you might want to briefly remind the class throughout this chapter of learning. Examples of questions students might ask are provided below. Potential responses to these questions will be green following the question.
  • Can parasites be transmitted from animals to humans? Some parasites can be transmitted from animals to humans, those are called zoonotic. Some examples of transmittable parasites are roundworms, hookworms, tapeworms, and Toxoplasma gondii (toxoplasmosis).
  • Can farmers do anything to prevent their animals from parasites? Farmers can do several things to prevent or minimize extreme negative effects of parasites on their farm animals. Farmers can implement pasture management techniques (maintain proper forage height), rotation grazing of pastures, administer deworming treatments or topicals, and more. 
  • How do external parasites impact animals? External parasites can be irritating to the animal and cause visible lesions and/or serious disease.
• One of the more challenging or misconceptions about the life cycle of intestinal parasites is how they get to the GI tract in the first place. This is also a step that is not clearly stated in the illustration of the life cycle of rounds worms. Make sure to discuss this important leading step as the start of the life cycle of a round worm in cows. In addition, tying all the steps back into the continuation of the cycle is also important.
  • How are parasites introduced into the environment? Parasites are introduced to an environment primarily through the movement of infected hosts, either by migration, travel, or the transport of contaminated materials like food, water, or soil. 
  • When are parasites most dense in population? For many parasites, particularly in regions with distinct wet and dry seasons, the wet season is typically when parasite populations are most dense due to favorable conditions for their life cycle
  • Does the cycle ever come to a stop? In general the life cycle of a population of parasites never ends. Parasites continue to lay eggs, hatch, and get reintroduced to other animals. However, an individual parasite’s life cycle does eventually end when they die.
• The ruminant digestive tract is likely the most difficult concept to understand within this lesson. Ruminant’s have much more complicated GI tracts and digestion takes a lot longer to digest food than other animals.
  • Why do cows have different stomachs than humans and some other animals? Cows have different stomachs because they are designed to eat strictly plant material, which humans and some other animals cannot easily break down. Since cows have their unique four-chambered stomach, it allows for extensive fermentation and digestion with the help of microbes.
  • In what order does the parts of the GI tract of a cow go in? Mouth, esophagus, stomach (rumen, reticulum, omasum, and abomasum), small intestine, cecum, large intestine, anus
  • How long does it take a cow to digest food? It takes a cow 1-3 days to digest its food.

Further Exploration

Sources Cited

Corwin, R. M., and Randle, R. F. (1993, October). Common Internal Parasites of  Cattle. University of Missouri Extension. https://extension.missouri.edu/publications/g2130

Kustritz, M. R. (2022). Parasite Control, Veterinary Preventive Medicine (pp. 135-176). University of Minnesota Libraries Publishing. https://pressbooks.umn.edu/vetprevmed/chapter/chapter-5-parasite-control/

VanHoy, G. (2023, June). Common Gastrointestinal Parasites of Cattle. Merck Veterinary Manual. https://www.merckvetmanual.com/digestive-system/gastrointestinal-parasites-of-ruminants/common-gastrointestinal-parasites-of-cattle

VanHoy, G. (2023, June). Overview of Gastrointestinal Parasites of Ruminants. Merck Veterinary Manual. https://www.merckvetmanual.com/digestive-system/gastrointestinal-parasites-of-ruminants/overview-of-gastrointestinal-parasites-of-ruminants

Student resource links are included in the student page.

Other chapters within this textbook may be interesting for students. Some options can be found linked below:

Scruffy’s Tale

Dazzling Dory’s Digestion