Chickens With Worms and Deworming Chickens
There was this great practical joke my friends and I used to talk about when I was around seven. We would ride our bikes along the shore of the local lake, and as we passed by one of the townsfolk fishing from the shore, one of us would ask “Hey! You got worms?” “Yah! Shoor!” the angler would reply. In Minnesotan, that means “yes”. Then we would all shout, “Better go see a doctor then!” and ride away from the flabbergasted fisherman in a cloud of riotous laughter.
To be clear, we never actually did this prank. But we talked about it a lot for a while. We thought it was hilarious.
Someone could have explained to us that the humor in this unrealized joke was based on a homographic pun. Annelids used as fishing bait, such as leeches, earthworms, and nightcrawlers are commonly referred to as worms, and so are parasitic helminths like tapeworms and roundworms.
And then, presented with that explanation, we all would have said, “Um…What?”
Later in life I would be up close and personal with all sorts of parasitic helminths. A development that would have been uncomprehensible to seven-year-old me.
Worms
My close relationship with parasites was not what you’re probably imagining. It was professional. I spent a long stretch early in my career working as a microbiologist in the clinical lab of a large Minnesota medical center. One of my responsibilities was examining patient stool specimens for parasites. Mostly I would run across giardia, the most common human parasite in the US. And occasionally, on a really exciting day, I would find tapeworm eggs. But most samples were negative. Public health and sanitation are good in Minnesota.
Then, in the early 1980’s, the US saw a massive influx of refugees from camps in Thailand and other parts of Southeast Asia; as many as 10,000 new refugees each month. Many of these folks settled in Minnesota and the medical center where I worked is where many sought medical treatment.
Examination of stool specimens for parasites was a frequently ordered lab test, and performing these tests on this population was an eye-opening, educational experience for me and the rest of the staff. Probably over half of the samples submitted were positive for parasites. And while there certainly was giardia, there was also a cornucopia of other exotic protozoan and helminth parasites. Some samples contained two, three, or even four different parasites.
The people submitting these parasite-laden samples had fled their home countries and had been living harsh lives. Many had been living in overcrowded camps with bad environmental sanitation. Due to the substandard living conditions, it was impossible to maintain good personal hygiene. So, of course, these unfortunate people had parasites. The conditions they were living in were exactly the sort of conditions where parasites thrive. I felt like I was doing important work. Every day I was discovering significant information regarding the health these patients, thus allowing them to get treated and get better.
Chickens With Worms
But this is about chickens, right? Let me quickly scroll up to the top. Yep. It says “Randy’s Chicken Blog.” So, here’s the segue. One day I stopped being a medical microbiologist, retired and got chickens. And, as a flock keeper, I worried about things that could harm my birds. Like worms. Not earthworms, of course, but parasitic helminths. And this article is about that. So, if you’re wondering about worms in your flock, read on!
And just to keep it simple, for the rest of this article when I talk about worms, you and I will both know that I’m really talking about parasitic helminths and not the critters that crawl around freely in the dirt.
Do My Chickens Have Worms?
People infested with worms, as I’ve already mentioned, have probably been living in substandard conditions with bad sanitation and are unable to maintain good personal hygiene. But those same conditions are normal conditions for chickens. Do chickens use toilets? The world is a chicken’s toilet! Personal hygiene? A hen will happily scratch and peck her way through an area that she and her flock-mates have just used as a latrine.
Tapeworm
A picture of a tapeworm (or probably a piece of a tapeworm) sent to me by a reader - found on the coop floor
Many worm species that infest chickens are spread when chickens peck up food contaminated with worm eggs that come from the poop of other chickens that are worm-infested. Given how easily that can happen, you can see that transmission is pretty easy. Other species of worms have specific intermediate hosts such as earthworms, slugs, and insects like beetles and flies. Chickens consider all those critters delicious! Once again, transmission is pretty easy.
So, are the chickens in your flock infested with worms? If you are a large commercial operator and your hens are kept indoors, off the ground, in wire cages where they have access to a very limited number of other hens, and are sent to slaughter after a couple years of egg laying, your hens are probably worm-free. They’ve never had the opportunity to come in contact with worms. Oh, and btw, your chickens are also sad and abused.
If you keep multiple generations of chickens on the same plot of ground for a number of years, like we backyard flock-keepers do, then yes. These happy chickens are probably harboring worms.
Terry Golson, who used to blog prolifically over at Hen Cam (We all miss you, Terry!) has explained the situation well: “If you build a coop in your suburban backyard that hasn’t seen a chicken in 50 years, then it’s unlikely that for the first few seasons of hen keeping that your birds will harbor any parasites at all. Eventually, though, the parasites will come in via wild birds. Or maybe you’ll visit a friend who has chickens and you’ll get mud (and the parasites’ eggs) on your boots. Maybe you’ll pick up a[n infested] bird at a sale. Eventually parasites will lurk on your property.”
Do your chickens have worms? The straight and short answer is most likely. Every chicken in any backyard flock is potentially host to any number of worm species. Do you feel gross now? Are you worried about your flock’s health? How unhealthy is it for chickens to have worms? Well, let’s talk about that.
Is It Unhealthy for My Chickens to Have Worms?
Most of us humans living in stable, sanitary conditions in developed countries normally don’t have worms. And the pets who share our homes are also worm-free. They also live in sanitary conditions and probably get worm checks as part of their routine vet screenings.
The “worm-free” standard for chickens just is not realistically practical or achievable. And chickens can live normal healthy lives with a reasonable worm burden. Dr. Mike Petrik, writing on The Chicken Chick blog, suggests “There are few worms that cause true disease in hens…Hens will often carry quite a load of worms before showing any signs.” Chicken expert Gail Damerow states, “Most chickens have worms, yet they don’t exhibit any signs of disease.” Some veterinarians even maintain that having a few worms helps chickens develop a healthy, robust immune response.
But what if the worm burden is high? What if one of your hens, or your entire flock becomes host to a bazillion worms? What are the signs of a high worm load? A disgusting, but sure sign is when you notice actual worms in your chickens’ poop. An even more disturbing clue is the appearance of worms inside eggs. This can happen when the worm, specifically a roundworm, migrates up a hen’s oviduct from her cloaca and becomes enclosed in a developing egg.
Chicken Roundworms (Ascaridia galli) - (Chhandama - Creative Commons)
Other signs are less specific. When hens have a high worm load, they can have diarrhea, lose weight, look scruffy, lay fewer eggs, and become less active. But, of course, they can also display all of those same symptoms as the result of all sorts of other maladies.
Deworming
What should you do if your flock or some individuals in your flock are noticeably unhealthy with some or all of these nonspecific symptoms? One option: You can treat for worms using a chemical dewormer. If you see a noticeable improvement after deworming, you know that worms were the problem and that you’ve solved it. A better option: You can perform a fecal test for worms. A positive test showing a high worm burden would show that worms really are causing your flock’s health issues.
Routine Flock Deworming (And Six Reasons Why I’ve Stopped)
Some avian vets and chicken experts maintain that you should proactively deworm your flock on a regular basis to periodically knock down the worm population and prevent a high worm load. Most recommend once or even twice a year. I’ve always followed that advice and have been routinely deworming my flock ever since I got my first chickens.
Recently, though, after some reading and research, I’ve changed my mind. I’ve discovered that there are also avian vets and chicken experts who caution against regular deworming. I’ve come to see their point. There are compelling reasons not to deworm my birds on a regular schedule. I’ve stopped. It’s a big shift for me and my flock. Here’s why I changed my mind.
1 - Chickens can carry around a reasonable number of worms and live normal healthy lives
Deworming carries certain risks and can be disruptive and stressful to my flock. If my hens are healthy, why should I subject them to that?
2 - There is only one approved treatment option
Fenbendazole is currently the only FDA cleared chicken dewormer in the US. It has clearance for the treatment and control of two worms; roundworms (Ascaridia spp.) and cecal worms (Heterakis spp.) in chickens and turkeys.
Any other wormers suggested to me by my neighbor, my vet, or that on-line forum, are potentially effective. But I would be using them “off label.” None of them are FDA cleared, and no licensed clinical trials have been done. Without the scientific rigor of clinical trials, any directions regarding dosage, toxicity, efficacy, and carryover of the drug into eggs are based on studies and trials that lack the stringency and comprehensiveness required for clearance.
Deworming chemicals that are commonly used off-label to deworm chickens are all approved for deworming other animals. So, why haven’t the manufacturers of these dewormers worked to get their products approved for chickens?
For drug manufacturers to get clearance, they must perform rigorous testing on each drug with each type of animal and each species of parasite. Then they have to formally submit their research results to the federal licensing bodies. It costs millions of dollars to get one dewormer approved for one animal.
And most commercial egg producers keep their hens in cages; indoors, sequestered in small groups, and off the ground. Thus, while the millions of chickens living in cages are living tortured lives, they don’t have worms and don’t need dewormers.
That leaves that small subset of happy birds scratching in the dirt as the only ones exposed to worms: Commercial chickens free-ranging in pastures, breeder flocks, and backyard chickens. Dewormer manufacturers simply aren’t going to spend all that cash to get clearance for this tiny market.
3 - Worms become resistant
Worms can become resistant after frequent, repeated use of the same dewormer. And worms subjected to different but related dewormers can develop resistance to all the dewormers that are in the same chemical family. The Poultry DVM website’s comprehensive directory of dewormers for chickens lists a mere ten deworming drugs for chickens: Fenbendazole and nine off-label drugs. Three of the off-label drugs are in the same benzimidazole family as Fenbendazole. The arsenal is small. So, frequent, repeated use of the same dewormer is unavoidable when flock owners are deworming on a regular basis.
The Merck Veterinary Manual affirms that “the number of medications approved for treatment of helminthiasis in poultry is decreasing. There are also reports of resistance developing.” Their suggested solution to that dilemma? “To decrease the potential spread of resistance, treatment should be limited to birds with severe infestation that show clinical signs of disease.” (my emphasis) “Such targeted treatment also seems to more effectively decrease worm burden and cumulative environmental parasite egg numbers than untargeted routine treatment.”
4 - Not all dewormers treat all worms
FDA-approved fenbendazole has demonstrated good broad-spectrum effect against all the common nematodes (capillary worms, cecal worms, gapeworms and roundworms) and is also effective against tapeworms. Fenbendazole’s off-label cousins, the various benzimidazoles, are also fairly broad-spectrum. Most of the other off-label wormers have a narrower range. Ivermectin, for example doesn’t work against tapeworms.
If I want broad-spectrum coverage, my choice is to always treat with fenbendazole or a related off-label dewormer. But, if I’m worming my flock a couple of times a year, that’s a terrible strategy! Constant repeated use risks developing resistance. The alternative is to alternate fenbendazole with a one or more of the off-label wormers that are more narrowly focused. And with that strategy I know that I’m not treating for whole categories of worms. Neither choice is a good one.
5 - Reinfestation
The Chicken Coach website explains reinfestation succinctly. “There's no point in worming your flock unless you first address their environment and diet. If you don't, you'll just have the problem return in a few weeks' time.”
If my hens have worms, I can assume that they’ve been pooping worm eggs all over their run. Some worm eggs can remain viable in the soil for several years. If I don’t want my hens to consume worm eggs when they peck and scratch at the soil and become immediately reinfested, I would need to move them to a completely new area. Unfortunately, the fence surrounding my run is a pretty permanent structure. So, a new run isn’t going to happen. I’m sure that most backyard flock keepers can tell the same story.
So, what’s the point of taking my birds through a deworming process when they’ll become reinfested in short order?
6 – Toxicity
A doctor once presented me with this interesting idea: “All medicines are poisons with one good side-effect.” He was probably riffing on the classic toxicology aphorism coined by the 16th century Swiss physician, Paracelsus, who said, "All things are poison, and nothing is without poison; the dosage alone makes it so a thing is not a poison." Most toxicologists remember this as: "The dose makes the poison"
The point is that wormers are powerful chemicals that kill worms. Worms are animals - and chickens are animals, so any chemical toxic enough to kill worms can also potentially harm chickens. A chemical that is medicinal becomes poisonous when it’s used incorrectly. So, read labels carefully. Follow instructions scrupulously, and if the product is off-label, follow the guidelines of known, trusted sources.
Also, be aware of potential side-effects. Fenbendazole, for instance, can cause deformed feathers if it is administered during a molt while feathers are being formed.
And finally, don’t use dewormers indiscriminately. Which brings us back to my point that if your flock is loaded with worms, deworm them. If they appear healthy, don’t stress them with deworming chemicals.
My Six “Best Practices” Suggestions for Controlling Worms
-1-
Worms come from worm eggs. The eggs are either consumed by your chickens or by a slug/earthworm/insect intermediate host which is then consumed by your chicken. And worm eggs come from chicken poop of infested chickens (or other birds). Control the poop and you control the problem.
-2-
Periodically switch to new a run space if you can. Caveat: That’s simply not practical for most backyard flock keepers.
-3-
If your flock is permanently in the same run, keep the run meticulously clean. If your run is small, it would probably not be too odious to remove and compost the top few inches of soil occasionally and replace it with fresh sand.
-4-
Worms thrive in warm, humid environments. You can’t control the weather, but you can respond to it. Don’t build your run in low areas where water pools. If the run area is low, build it up with dirt or sand. If your run area is small, roof it to keep it dry.
-5-
To avoid the spread of resistance, and for all the reasons listed in the previous sections, do NOT deworm periodically and indiscriminately.
-6-
I’m bolding this, because it’s so important. Check for worms on a regular basis by fecal exam and if the worm load is high, THEN deworm. And THEN think about how you can improve your flock’s environment.
Fecal Exam for Worms: Three Approaches
While there have been some recent advances in methods for testing for worms, like PCR and antigen testing, most of the new methods are not readily available for routine vet testing and are mostly being used for research purposes. The gold standard is to concentrate a fecal specimen by flotation or sedimentation, and then examine the concentrate under a microscope for the presence of worms and other parasites. While it’s possible to find an actual worm in a fecal specimen, what you’re really looking for is the presence of worm eggs. There are three ways this test can be accomplished.
Do it yourself
Gail Damerow, in The Chicken Health Handbook suggests that anybody can check their flock for worms. She offers up some good solid instructions for collecting a sample and concentrating it using a flotation method.
If you follow her advice and do your own testing, you will, of course, need a microscope. You can purchase pretty decent used microscope online for a couple hundred bucks. You can also find a serviceable used centrifuge priced in that range as well.
I’ve spent many years peering into microscopes, and I’ll offer this caveat regarding their use. There’s a learning curve. You’ll have to spend some time becoming proficient. Then, when you’ve figured out the microscope, you’ll need to know what you’re looking for. While you can find pictures of a variety of worm eggs in The Chicken Health Handbook and online, there are lots of different worm species that could be infesting your flock. And worm eggs come in a variety of sizes and shapes depending on the species. They often look similar to each other and to plant cells and other debris that may be present. Again, there’s a learning curve.
If you aren’t willing to invest in the time and expense you would need to accomplish do-it-yourself testing, go to the professionals. There are two options.
Check With Your Local Vet
Most vet clinics do fecal parasite screening even if they don’t see chickens. Some vets that don’t do the testing on-site will send samples out to an affiliated reference lab for testing. So, contact your local vet clinic! They’ll tell you how to collect the sample and how to bring it to the clinic.
Send A Sample to A Testing Lab
By sending a fecal sample from your flock directly to a lab, you skip the middleman (the vet clinic). You can quickly find a list of labs by doing a Google search for “veterinary parasite testing labs.” Bear in mind, that while this may be a less expensive option than going to a vet, if the results are positive, you should consult with a vet for interpretation of the results and treatment guidance.
Raillietina echinobothrida - a tapeworm from a chicken (Chhandama - Creative Commons)
Looking for Worms via a Fecal Exam – How I Did It
As I’ve already said, I’ve always periodically treated my chickens for worms as a preventative. Then I had my epiphany and realized it would be better to test rather than blindly treat. I could easily set up a little lab in my basement. I have the background and experience that would allow me to be up to speed fairly quickly.
But, quite frankly, I don’t need another project. I have lots of projects already. Like all those chickens. And like writing this blog. And like a bazillion other things. So nope. No basement lab for me! My best option, I decided, was to get a sample to the professionals and let them take it from there.
Collection
I cleaned the coops in the evening. The next morning, I harvested a bounty of chicken poop that the chickens had generously left for me on the coop floor. They had deposited it overnight, so I knew it was fresh. I collected from both of the coops as well as from several hens that are living separate from the flocks. Everything went into one Ziplock bag, which I closed and kneaded to homogenize the sample. Since my birds all live in the same space, any worm infesting one chicken is undoubtedly infesting the entire flock. So, one collective sample from a variety of birds would be representative of the whole flock.
Submitting Samples
I put a tablespoon of the homogenized fecal sample from my flock into a Ziplock bag, sealed it, and delivered it to the Countryside Veterinary Clinic in New Richmond, Wisconsin, a nearby clinic with a wonderful, caring vet who sees chickens. The folks at Countryside didn’t do the testing in house, but sent it to their reference lab, Moichor Labs, a veterinary reference lab.
I put another tablespoonful into another bag, double-bagged that bag, put it in a mailer, and sent it to Pet Home Tests, a veterinary testing lab that does fecal testing for parasites on a variety of animals.
Results
Within a few days I had results from both labs. Pet Home Tests reported a “negative” result. Negative means that they found zero worm eggs. That, of course, doesn’t mean that my flock is 100% worm-free. It does mean that any worm eggs that may have been present in the sample that I submitted were there in such low numbers that they were below the level of detection of the testing method used in the Pet Home Tests lab.
Pet Home Tests pointed out in their report that it is possible that my flock could have a new infestation and the worms are not yet egg-producing adults. If that were the case, there would certainly be eggs the next time I submit a sample for testing.
The Moichor Lab results reported to me by Countryside Veterinary Clinic was not negative, but it essentially matched the Pet Home Tests result. Moichor found a grand total of one worm egg in the entire sample they examined. They described that one egg as a “large oval, tan and granular to globular internal structured ova” and suggested that it “appears to be a potential Strongyle type ovum, however, it also appears more compatible with a trematode ovum based on its morphologic appearance.” I know from experience that it can be difficult to nail down a specific identification based on the appearance of a single egg.
These results from two different labs have confirmed that the worm load in my flock is really, really low. My hens look and act healthy, so these results validate what I see when I walk into my coops.
A year ago, as we moved into autumn, I would have been subjecting my flock to a wormer, because that’s how I thought you were supposed to do things.
This year, based on these results, I will not be worming my chickens.
Endnote 1
According to the Merck Veterinary Manual, “approximately 100 worm species have been recognized in wild and domestic birds in the US.” This is a broad general description of the groups that these worms can be divided into, and a listing of the most important and common worms. For a more complete list of parasitic helminths, see the link at the bottom of this endnote.
Worms are divided into two groups, roundworms and flatworms. Flatworms can be further subdivided into two groups – flukes and tapeworms.
Roundworms:
Scientific name: Nematodes (Latin: nemat = thread. Thus, threadlike worm.)
Roundworms come in a variety of sizes but are all nondescript, thread-like critters that are difficult to tell apart from each other. If you see white things in chicken poop that look like short pieces of spaghetti, you’re seeing roundworms. If that description just put you off spaghetti forever, I’m really sorry.
Cecal worms (Heterakis gallinae)
The cecal worm is a half-inch long roundworm that lives in the ceca of chickens. It is one of the most common, if not the most common chicken parasite in North America. Heterakis eggs can remain viable in the soil for years. While symptoms are generally mild (a scruffy appearance, weight loss, a decrease in egg count), cecal worms can carry the the more severe histomonas parasite that causes blackhead in chickens, turkeys and other fowl.
Roundworms (Ascaridia galli)
Confusingly, there is a species of roundworms that is commonly referred to as “roundworms,” or sometimes “large roundworms.” These nasties are 4-5 inch-long yellow-white worms about the thickness of, well, a strand of spaghetti. Sorry. They live in a chicken’s small intestine. These are the guys that will occasionally migrate down the intestine and up the cloaca and wind up inside an egg. Symptoms are usually mild unless the worm load becomes heavy. They are very common parasites.
Capillary worms (Capillaria spp.)
Capillary worms are tiny, thread-like roundworms. There are six species that parasitize chickens. They live in the mouth, esophagus, crop or upper intestines, depending on the species. They can cause mild to severe infestations or death, depending on species and/or worm load.
Gapeworms (Syngamus trachea)
Gapeworms live in a chicken’s trachea and lungs and cause them to open their beak wide and gasp for air. I think everybody with chickens has heard of this worm, and at one time or another every one of us has worried that one of our chickens is infested with it. Gapeworms are not actually that common, and chickens yawn for a variety of reasons. This red, forked worm lays eggs in a chicken’s trachea. The chicken then coughs up the eggs, swallows them, and they pass out of the chicken and can be pecked up by other chickens or eaten by earthworms or slugs, which can serve as intermediate hosts. While uncommon, gapeworms can cause severe infestations and death by blocking a chicken’s airway and suffocation.
Tapeworms:
Scientific name: Cestodes (Latin: cestoda, from the Greek kestos = girdle or band).
Tapeworms are ribbon (band) shaped. They are made up of a “head” or scolex that attaches a chicken’s intestinal wall. Trailing off from the scolex is a long chain of segments called proglottids. Each proglottid is a reproductive organ that when mature is filled with eggs. Sometimes sections of proglottids become detached and you can find these “ribbons” in poop. The scolex usually remains attached even when proglottid segments become detached and the scolex continues to churn out new proglottids.
Fowl tapeworm (Davainea proglottina)
This is one of the smallest tapeworms. It never has more than nine proglottids and never grows more than a quarter inch long. It also causes the most severe symptoms. It damages the intestinal wall when it attaches, leading to gut perforation, peritonitis, and death.
Nodular tapeworm (Raillietina echinobothrida)
Nodular tapeworms are the most common chicken tapeworms. They are large – they grow up to a foot long. They do not cause intestinal damage per se. But do compete for nutrients which can become a big problem if the worm load is heavy. They also cause the formation of nodules on the intestinal wall, leading to tissue degradation and enteritis. This worm requires an ant as an intermediate host.
Sawtooth tapeworm (Choanotaenia infundibulum)
Sawtooth tapeworms live in a chicken’s small intestine, attached to the intestinal wall and usually cause only moderately severe symptoms. They typically form about 30 proglottids and grow to about 10 inches long. Their intermediate hosts include several fly species as well as locusts, ants and termites.
Flukes:
Scientific name: Trematodes (Latin: trematoda, from the Greek tremat = holes.)
Flukes are flat, oval, and worm-like and range from a millimeter to an inch in size depending on the species. Their most obvious feature is two suckers or “holes.” While flukes can parasitize other animals, they are not problematic to chickens in the US. I mention them here only for academic completeness. So feel free to completely erase them from your memory and concentrate on worms that pose a threat to your flock.
Thorny-Headed Worms:
Scientific name: Acanthocephala (Greek: acanthos = thorn and cephala = head.)
In any nicely organized scheme, there always has to be an outlier to spoil the symmetry, and in this scheme, thorny-headed worms are it. They are neither roundworms or flatworms or even worms at all but are rotifers – relatives of the tiny creatures that live in the ocean as plankton.
Plagiorhyncus formosus is the species of thorny headed worm that infests the intestines of certain wild birds and has also infested chickens - almost always baby chicks. The intermediate host of this parasite is pillbugs, so keeping chicks away from environments where pillbugs lurk is the easiest preventative strategy for this unusual “worm.”
More Worms
For a larger list of chicken worms, go to the Merck Helminthiasis in Poultry webpage and click on “table” in the bar at the top of the page for a table of common helminths of poultry.
Endnote 2
First – A List of Dewormers NOT to Consider:
Hygromycin B and Piperazine
Not so many years ago, both of these drugs were FDA approved for treating worms in chickens. They were, for a time, the only FDA-approved anthelminthics for chickens. If you’re searching for information on treating worms, you will probably run across references to both of these drugs in older books and on websites that have not recently been updated. Both of these drugs are no longer available in the US.
Hygromycin B used to be regularly incorporated into feed provided to commercial chickens, a really bad practice since it is actually an antibiotic that also happens to be toxic to certain parasitic worms. It’s in a class of drugs known as aminoglycosides. If you’ve ever been treated with amikacin, gentamycin, or tobramycin for an infection or an infectious disease, they are aminoglycosides, too – cousins to Hygromycin B. Overuse of any antibiotic creates resistant bacteria that no longer respond to that antibiotic or class of antibiotics. This is no small thing. The British medical journal, The Lancet, published a finding in 2019 that antimicrobial resistance was one of the leading causes of death worldwide. The FDA banned Hygromycin B for poultry in 2005.
Piperazine, which was FDA approved for the control of roundworms, became increasingly popular in the 1990’s as a street drug. It has been reported to have stimulant effects similar to ecstacy (MDMA). Piperazine derived synthetic drugs were becoming widespread at raves and dance clubs under names such as “Frenzy", "Bliss", and "Charge." It was classified as a Schedule I controlled substance in the United States in 2002.
Diatomaceous Earth (DE)
DE is a rock made up of the fossilized shells of diatoms. Ground into a powder, it is popular with many gardeners and flock-keepers as an insecticide. It works by desiccating insects that come in contact with it. Since it works as a drying agent, as it becomes saturated, it becomes ineffective.
Even though many flock-keepers swear by it as a wormer, it does not work. The minute a hen pecks up some DE, it comes in contact with the saliva in the hen’s beak. Then, as it travels through the digestive tract, it comes in contact with other fluids. In its saturated state, it is totally ineffective against internal parasites. If it did have the ability to desiccate worms inside a chicken’s body, it would also desiccate the internal organs of the chicken. I am not aware of any conclusive, reproducible clinical studies demonstrating that DE works against worms.
Pumpkin Seeds
Pumpkin seeds have been bandied about as a folk remedy for worms by a lot of people for a long, long time. People use folk remedies because Grandpaw used them and swore by them. As folk remedies are put to the test using scientific methods, we find that sometimes Grandpaw was on to something and sometimes Grandpaw was one sandwich short of a picnic.
An internet search on pumpkin seeds turns up a bounty of information. At one end there are bizarre recommendations for chowing down fistfuls of pumpkin seeds to destroy parasites that are perhaps only imagined. At the other end are actual controlled studies in peer-reviewed journals.
The scientifically conducted experiments test pumpkin seeds or pumpkin seed extracts on a variety of animals infested with an assortment of parasites. Some studies have found them to have an effect. Other studies have shown them to be ineffective.
I only found two studies involving worm infested chickens. Both were conducted in 2018. An Egyptian study published by the Beni-Suef University Journal of Basic and Applied Sciences found an alcohol extract of pumpkin seeds to be almost on par with fenbendazole against roundworms. A study conducted in The Philippines and published in The Turkish Journal of Veterinary & Animal Sciences found the efficacy of ground pumpkin seeds against a variety of worms to be “moderate” to “marginal.” Do you imagine that the authors of these two papers recommend that everybody go out and get pumpkin seeds and start treating their chickens? Nope. Both sets of authors recommend further study.
My recommendation: When you’re carving jack-o-lanterns or baking pumpkin pie, save the pumpkin seeds, along with all the rest of the pumpkin innards and give them to your chickens. Because they love them! And if you discover that your flock has been infested with a high load of worms, treat them with a proven dewormer!
Apple Cider Vinegar, Cabbage, Garlic and So On
In addition to pumpkin seeds, there are a whole host of “natural” dewormers that have been touted here and there. When someone promotes the use of one of these supposed cures, they usually use say that it is “felt” or “thought” to be an effective dewormer without explaining who is doing the feeling or thinking. My thoughts and feelings: As with pumpkin seeds, they are probably not harmful to chickens. They may or may not work. Chickens probably find most of them to be quite delicious. As with DE and pumpkin seeds, there’s a dearth of conclusive, reproducible clinical studies demonstrating that any of these products work against worms.
Dewormers Proven To Be Effective
Fenbendazole
Fenbendazole, which belongs to a class of drugs called “benzimidazoles”, received FDA approval for laying hens in October 2020 and is currently the only FDA cleared chicken dewormer in the US. It has clearance for the treatment and control of two worms; roundworms (Ascaridia spp.) and cecal worms (Heterakis spp.) and has also been shown to be effective against certain tapeworms.
Other Benzimidazoles
Flubendazole, Oxfendazole, Thiabendazole are three other benzimidazoles that are used as dewormers in a variety of animals, have been shown to be effective against a broad range of worms that infest chickens, but are not approved for chickens, thus require off-label use.
Other Off-label Chicken Dewormers
Ivermectin, levamisole hydrochloride, milbemycin oxime, praziquantel, and pyrantel pamoate have shown to be effective against a variety of worms infesting chickens.
Brand Names, Suggested Dosage, Etc.
The Poultry DVM website contains excellent information on the dewormers I’ve listed in this section that includes brand names, range of coverage, and suggested dosage. To see the full list of dewormers, click on “dewormer” in the “drug type” box.
