Lungworms in Goats

August 30, 2024Cheryl SmithHealth

Reading Time: 4 minutes

Lungworms in goats infest the respiratory tract of the animal host. Find out if your goats are at risk and what to do.

If you’ve ever had a goat with a chronic cough, you know how stressful it can be (for you and the goat). Coughing can be caused by dusty hay, pneumonia, mold, allergies, or, where I live, wildfire smoke. Although rare in the United States, according to the University of Oklahoma College of Veterinary Medicine, another possibility is lungworms. If other causes have been ruled out and you live in a wet area, it may be worth testing to determine if the goat is infected with lungworms.

What are lungworms?

Lungworms in goats are parasitic nematode roundworms that infest the respiratory tract of the animal host. The infection they cause is known as verminous pneumonia. Three different types of lungworms affect goats (and sheep) in the U.S.: Dictyocaulus filaria, Protostrongylus rufescens, and Muellerius capillaris.

D. filaria causes the most disease and is the only one whose lifecycle is direct (i.e., having no other host between the pasture and the goat). The other two are less likely to cause disease, and reproduce through an intermediate host.

How do they reproduce?

According to Goat Medicine, these parasites are more common in fall, when the weather is cool and wet. In the case of D. filaria, goats eat the larvae in the pasture, which irritate the trachea and airway after taking up residence in the lower lung, and are then coughed up, swallowed, and excreted in feces or through nasal secretions. They go through more development on the pasture and are eventually eaten again by the goats.

The other two types, P. rufescens and M. capillaris, live in the air sacs found in the lungs. They’re coughed up and swallowed, then excreted into the pasture. At that point, the parasites need slugs or snails to complete their development before being eaten again by the goat and starting the life cycle all over again. Check out www.GoatBiology.com for a good video showing the life cycle of these parasites.

How do I know if my goat has lungworms?

Goats on a dry lot aren’t at risk for lungworms; those that freerange are. Because the disease usually isn’t severe, it may not be obvious a goat has lungworms. The condition is sometimes an incidental finding on necropsy.

In the case of a heavy infestation, the animal may have a chronic fever and cough, discharge from the nose, increased respirations, dyspnea (difficulty breathing), failure to gain weight or weight loss, and decreased milk production if the goat is lactating. Although lungworms can infect goats of any age, younger goats have less immunity and, consequently, are more likely to have severe disease.

Once the lungs are infested with the parasites, secondary infections such as pneumonia or bronchitis, as well as emphysema or edema, can occur. Goats can also be infected with more than one type of lungworm.

The definitive test for lungworms is a fecal examination. A special method called a Baermann test is required, because rather than eggs, larvae are in the feces. Unfortunately, this test sometimes produces false negatives.

Baermann Technique

The Baermann technique is more complicated than doing a home fecal with a microscope, so submitting feces to a veterinary lab will give more accurate results. For those do-it-yourselfers, the Royal Veterinary College has a step-by-step guide to the equipment needed and the process. In short, feces are suspended in a cheesecloth in water, and the larvae sink to the bottom, where they’re collected for analysis and then viewed under a microscope.

How are lungworms treated?

If feasible, the first step is to move the goats off the infected pasture. Then, deworm the affected goat(s) with anthelmintics (dewormers) like for other parasites. The two classes of effective drugs are benzimidazoles (albendazole, fenbendazole, etc.) and macrocyclic lactones (ivermectin, moxidectin, etc.).

A 1988 study in Canada found that more than 25% of the 179 does treated for M. capillaris with ivermectin began to excrete firststage larvae from four to more than nine weeks after treatment, even though they were kept indoors and off pasture. Goats over 3-years-old were more likely to resume passing larvae.

The authors speculated that residual immature parasites — found in higher numbers in repeatedly infected goats — weren’t affected by the treatment with ivermectin and resumed the maturation process after a period of time. This result would argue for more frequent fecal exams in goats infested with lungworms.

Can lungworms be prevented?

Steps taken to prevent lungworms are, in many cases, similar to those for avoiding other parasites:

Avoid letting goats on pasture in the early morning, evening, and during rainy weather, since that’s when larvae crawl up the grass.
Fence-off wet areas so goats don’t graze on potentially infected areas.
Get geese or ducks to eat the slugs and snail that are part of the worm’s life cycle.
Do not overuse dewormers. Treat only those goats with a heavy parasite load rather than the whole herd, and don’t routinely deworm.

Fortunately, lungworms are not a huge problem in goats, especially those that don’t graze on damp pastures. In addition, goatkeepers may inadvertently eradicate them when they treat for other parasites. But it’s important to at least consider the possibility in the case of a chronically coughing goat.

CHERYL K. SMITH has raised mini dairy goats in the Coast Range of Oregon since 1998. She owns Karmadillo Press and is the author of Raising Goats for Dummies, Goat Health Care, Goat Midwifery, and Shed Boy, the first in a series of cozy mysteries set on a goat farm. www.GoatHealthCare.com

REFERENCES

Ballweber, Lora Rickard. Nov 2022. “Lungworm Infection in Animals.” Merck Manual Veterinary Manual. www.merckvetmanual.com/respiratorysystem/ lungworm-infection/lungworm-infection-in-animals
Engdaw, TW. 2015. “A Review on Lungworm Infection in Small Ruminants.” American-Eurasian Journal of Scientific Research 10(6): 375–80.
Harwood, David. 2006. Goat Health and Welfare: A Veterinary Guide. Wiltshire, UK: The Crowood Press. Pp. 102–03.
Jones, Meredyth. 2021. “Veterinary Viewpoints: Top 10 Things You Need to Know about Pneumonia.” https://news.okstate.edu/articles/veterinarymedicine/ 2021/veterinary_viewpoints_top_10_things_you_need_to_know_ about_goat_pneumonia.html
McCraw, BM, and PI Menzies. 1988. “Muellerius capillaris: Resumption of Shedding Larvae in Feces Following Anthelmintic Treatment and Prevalence in Housed Goats.” Canadian Veterinary Journal 29: 453–54.
Smith, Mary C., and David M. Sherman. 2009. Goat Medicine, 2nd ed. Wiley-Blackwell. Pp. 617–18.
The “Other” Worms that Infect Small Ruminants. Nov. 2022. American Association of Small Ruminant Practitioners. Wormx.info.
Verminous Pneumonia (Lungworms). 2019. Goats.extension.org/verminouspneumonia- Lungworms

Originally published in the 2024 Summer issue of Goat Journal and regularly vetted for accuracy.