Parasites such as fleas, ticks, mites and intestinal worms are all canine parasites and all parasites depress your dog's immune system.  Conversely, a weak immune system can't fight off the toxins and damage done by parasites, whether internal or external.




Most canine worm medicines are actually large animal wormers.  Horse wormers are used for hookworms, heartworm, and roundworms.  Canine tapeworms require special de-wormers.





by Fred Lanting


Fred Lanting(2015 Update) The Changing Scene Wormers, like flea and tick killers, are constantly in a state of flux, so make sure your vet and you keep up to date on the latest studies. But don’t automatically assume that if something new is highly effective, that it is the best. Many old and relatively safe approaches can still be used.


Telmin™ (mebendazole), Scoloban™ (bunamidine), DNP, Vermiplex™, and Styquin are effectively off the market in the USA now. Wormers similar to Vermiplex may kill a fairly high percentage of hookworms, roundworms, and considerable numbers of tapeworms, but not enough to completely eradicate an infestation; many of these are principally toluene or similarly offensive solvents. They usually require fasting before effective administration.





Hook- or













Pyrantel pamoate

(Nemex, Strongid)**

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Prazi + Febantel™ (Paracitide-10™) +++ +++ +++ ---


(prazi- & pyr. pamoate)

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*When Packaged for cattle and swine and bought from a feed store or on-line without prescription; same ingredient as, but cheaper than Heartgard brand. Ivermectin may come in multiple strengths—I use the 1% solution. Ivermectin had long been sold “off-label” for dogs; it has been considered dangerous in some Collies, Shelties, and crosses of these, if given in doses large enough for treating intestinal worms. In these breeds, you may wish to consider lower dosage, or use of fenbendazole instead, a drug that is also moderately successful against Giardia.

**Pyrantel pamoate is also sold as a paste for horses, but dividing doses of that form is difficult; the pleasant-tasting liquid sold for very young pups is easiest to administer. Tablets are also available. For hookworm, which can be hard to rid from the premises, every other week for 6 weeks may be required. Better to switch to ivermectin after the first dose.

***Panacur is effective against only one type of tapeworm (Taenia, not Dipylidium); it is administered for 5 days for the tapeworm and 3 days for other worms.

In all cases, it is wise to treat the dam 2-3 weeks after whelping, or after her pups start eating “solid” food in the last stage of the weaning process. I have found that almost all intestinal worm problems seen in North America can be prevented by dosing pups when they are 2 weeks old with Nemex, effective against canine roundworms and hookworms, and then start oral Ivermectin another two weeks after that.


For both worms and ticks, I get ivermectin (Ivomec™ is just one brand name)—it’s labeled “for cattle and swine”—at feed stores in 50-ml bottles of 1% injectable ivermectin (it’s the active ingredient in Heartgard™). It takes care of various worms in the canine. One bottle will possibly last most of a little dog’s life, but even with large breeds, you won’t be spending the small fortune that others do. I store mine in the refrigerator, even though there doesn’t appear to be a shelf-life problem at room temperature. It’s up to you (and maybe your vet, if you wish) what you choose, but I have had good results for several decades with this protocol.


The Heartgard dosage to prevent heartworm, as I once wrote down from their old literature, is 6 micrograms per kilogram of body weight. But buying the high-priced pills from the vet is too expensive for most people, and you get the same results by shopping where the livestock farmers shop. The insert in some packages of 1% ivermectin recommends one milliliter (1 ml = approx. 1 cc) per 110 pounds of bovine, and 1 ml per 75 pounds of swine. Anatomically and medically speaking, dogs are more similar to pigs than to cows, and the swine dosage is a fair starting point for almost all breeds. Equivalent in medical jargon is 300 micrograms per kilogram of body weight in swine, much higher than what I use monthly. These cattle/swine dosages are designed both “for the treatment and control of internal and external parasites,” the box says.


I would use that level for the first dose if I were to bring in a new dog to my kennel, to make sure I got rid of any roundworms and hookworms they may have brought with them. But then, I reduce the roundworm dosage to a regular monthly heartworm-preventative maintenance dose. If ticks get especially troublesome, I give a little more every other month (see below).


The insert explains that ivermectin’s “wide margin of safety [in mammals] is attributable to the fact that... [the active ingredients, lactones]... do not readily cross the blood-brain barrier. In other words, the chemical/drug acts so much more on the brainless parasite than on your smart, “brainy” dog. In cattle and swine, the insert says, ivermectin is effective against gastro-intestinal worms, lice, and mites.


Some people ask, “Can I figure out the dosage from the label on the bottle?” Yes, but is it necessary? You may have to do a lot of converting of volume measurements, metric system designations, etc. What others use (it already has been done for you) may be close enough, as long as you feel comfortable with its use in your breed. I have had many years of success, treating my GSDs, Shibas, and Whippets with never a sick dog because of ivermectin.


I dose orally, not by injection, even though I buy the “injectable” form from my local farm supply & feed store. You should understand that less of almost any drug gets into the circulatory system if ingested, than if injected. Keeping that in mind, the manufacturers’ suggested levels (designed for hypodermic injection) are usually a good bit below what they probably would recommend for oral administration. Leave the needle and syringe stuck in the bottle's rubber stopper when not in use. Turn the bottle upside-down, draw the desired amount into the syringe, pull out the syringe while leaving the needle in the stopper (you'll re-connect these after dosing the dog). Squirt the liquid into the dog's mouth. Can't be any simpler than that!


Heartworm, Only mosquitoes apparently can incubate the heartworm nematode, and only certain species of mosquito seem willing to do the job; unfortunately, they seem to be everywhere. Reportedly, foxes as well as coyotes can keep the problem alive in any given area, but there are enough dogs around that are not on a preventative, that they don’t need any help from wild animals to spread this disorder. A good blood test can uncover microfilariae. An old control measure once used in some parts of the South was the twice yearly treatment with “arsenic” (thiacetarsamide), to kill adult heartworm. A newer, far less harsh, and far superior preventative is the once-a-month dosage with either ivermectin or milbemycin (see comparisons at the end of this article). Ivermectin has long been used by farmers as a cattle wormer; they found it got rid of all worms (except tapeworms) in their dogs, too.


The lifecycle of the heartworm begins with the mosquito feeding on an infested dog. It picks up, with the blood, some tiny heartworm embryos called microfilariae. Within minutes, the microfilariae begin to migrate from the gut to another part of the mosquito, changing into an infective form called larvae. In a couple of weeks these larvae move to the mosquito’s mouth and when the insect bites the dog they escape into the blood, fat, and mucous tissues of that victim.


There they continue to develop in the fatty tissue under the dog’s skin and undergo more molts. In a few weeks they enter the veins as immature worms and reach the heart three months after entering the dog. Growing to a length of some seven inches for males and almost twice that for females, they lodge in the heart, copulate, and produce eggs that then hatch into microfilariae, and the cycle is complete.


The danger to the dog is in the worms’ interference with flow of blood, proper opening and closing of the heart valves, effective oxygenation of cells, and proper blood flow to the lungs, especially when the worms die and clog up the pulmonary arteries. The principal danger to the dog with an adult heartworm population being treated with arsenic is when the dead worms let go and obstruct the pulmonary arterial flow; pneumonia is then the most likely cause of death, so the dog must be kept from exercise or exertion during this treatment period.


For heartworm prevention - I aim for approximately 0.15 ml (milliliters) of the 1% ivermectin for every 50 lbs. of dog body weight, 0.21 ml for 75 lbs., and 0.27 for 100 lbs. Naturally, you can’t be accurate to two decimal places, even when you use a 1-ml “TB” syringe, but I don’t have to be precise, because it is quite a safe drug for almost all breeds, especially at this low preventive/maintenance level. One ml is the same as one cc. Any diabetic can get a 1-cc hypodermic syringe and needle for you, if you can’t get one at a drugstore. You will see veterinary journals use micrograms per kilogram, but remember that 50 pounds equals 22.7 kg, and 0.15 ml equates to 1500 milligrams (mg). This can also be stated as 66 micrograms (mcg) per kg of body weight. While this may not be enough to kill all adult intestinal worms in already-infested dogs, it does inhibit their development from eggs. Dr. Mary Straus, a researcher and reporter in this field, says that it also is “far more than is needed to kill heartworm larvae/prevent heartworm infection (6 mcg/kg).”


I dose with 1% ivermectin once a month, and I don’t worry about giving a little more than the above amounts. I don’t even do stool checks anymore; just use that dosage as a prophylactic (preventive) approach against heartworm and intestinal worms.


Washington State U. Vet School says, re ivermectin: “While the dose of ivermectin used to prevent heartworm infection (6 micrograms per kilogram) is safe in dogs with the [MDR1] mutation, higher doses such as those used for treating mange (300-600 micrograms per kilogram) [are not].” But you don’t have to use that fifty- or hundred-times dosage for intestinal worms.


For actual round, hook, or whipworm presence, or high exposure risk such as weekly exhibition on probably-contaminated dog show grounds, I would give my dogs a higher dose: 0.3 to 0.4 ml per 25 lbs., or 1 ml per 75 lbs. every 4 or 6 months instead of their regular low-dose level. I also use the higher dose (or normal dose twice a month) to combat ticks when they get especially bothersome. Dr. Straus says that this level, which provides approximately 6-8,000 mcg ivermectin per 50 pounds of body weight, “is appropriate” for intestinal parasites. She also says “There are plenty of safer alternatives, such as Panacur (fenbendazole)” but that does not affect heartworm, and I prefer a single wormer for both heartworm and intestinal worm prevention other than tapeworms. Roundworms (Toxocara Ascarids) and hookworms (Ancylostoma) are the main intestinal pests.


TICKS and Ivermectin - While I still maintain that the best way to control ticks is to go over your dog every day and pluck them off with a tweezers (some people drown them in soapy water or other detergent), you can also get an additional measure of control by using ivermectin. Especially if you have an unusually bad tick year. Higher doses than I use against worms are used in Australia as a public health measure in rural Aboriginal communities (where the children and some of the adults sleep and otherwise are in intimate contact with their crossbred Dingoes) to kill ticks and sarcoptic mites on family dogs. There it has been found that dosing every six weeks was adequate in controlling the tick problem on both the pets and their owners. In that country, the use of ivermectin as a public health measure has favorably affected mortality rates of both man and dog, and greatly improved the health of both. When their dogs are made tick-free and cleared of Sarcoptes, the children benefit because they no longer contract these diseases from their furry friends. There is much history elsewhere of using it for mites & ticks. In much larger, more frequent long-term doses, it has been used against demodectic mange. My personal experience, verified by anecdotes from others, is that ivermectin has considerable action against ear mites and ticks (which are non-insects) but not against fleas (insects).


The higher de-worming level I mentioned earlier is what I use two to four times a year if ticks get very bad. Or else, I’ll give the dogs an extra mid-month (roundworm-control-size) dose, and that helps control the ticks a great deal. The nasty little arthropods still bite, but very few survive long enough to suck much blood. They tend to “die and dry.” By the way, this “larger dose” (as I call the one I give for other than heartworm preventive), is the same that pigs get by injection. And as I said, not as much gets absorbed through the gut as would if injected subcutaneously.


Procedure: I stick a 1-ml “hypo” (the size used by diabetics, and what used to be called a “TB syringe”) into the rubber-stoppered 50-ml bottle. The first of the month, I hold it upside-down and pull the desired amount into the barrel, disconnect it so that the needle stays in the bottle (stuck in the rubber seal), and squirt the selected volume into the mouth of the dog.


The website has more on efficacy of medications like this. This information is not a medical recommendation; by law in most states, you need to confer with your veterinarian for that.


BREED CAUTIONS: Owners of certain at-risk Collies, Shelties, Silken Windhounds (Whippet/Sheltie cross), and perhaps Australian Shepherds, Kelpies, etc. might want to check current knowledge on vet websites for information on “the MDR1 mutation” which is a genetic abnormality found in Collies and some of their relatives. As the moderator of a veterinary medicine Internet chat list says, “Mixes of unknown pedigree should be treated with caution at the higher ivermectin doses.” Which higher doses, you may ask? Well, that’s a reference to using the drug for killing intestinal worms, not the levels for ascarid or heartworm control.


Well-versed and careful researcher John Cargill says, “Moxidectin (in Proheart™ tablets) is given once a month to prevent heartworm disease. [Several] products contain macrocyclic lactones which kill the tissue stages of heartworm larvae and are given once a month. They are generally very safe, but should not be used in young pups as they can enter the brain and cause nervous system symptoms such as depression and signs of stupor. Collie-type dogs are more sensitive to nervous-system effects than other dogs, but even in these breeds, the products are safe at recommended doses.” See:


Ivermectin vs. other drugs: Here, as additional information, is a collection of some of the statistics on adverse effects of the various heartworm preventatives currently on the market. The data in the following list was compiled from the Food and Drug Administration listing of Adverse Drug Experience Reports. The number of deaths per year is significant, although comparative percentages are not given. Selected other adverse events are also reported.


Bonnie Dalzell, Borzoi breeder and another respected data researcher, says: “The dose I got from a vet working for Merck, using the 1% liquid ‘horse Ivomec’: for dogs who do not have the MDR1 gene, 1 cc orally for 135 lbs of dog; the heartworm prevention dose, safe for MDR1 dogs: 0.1 cc orally per 135 lbs of weight. I do not try to get an accurate low heartworm dose for a 10-lb. dog—I would use the Heartgard or Interceptor instead. Breeds that have been shown to have around 30% individuals with the MDR1 gene include Silken Windhounds, Shetland Sheepdogs, Collies, and Australian Shepherds. If you are in doubt, there is now a PCR test for this gene. Since you can test to find carriers, you could even eliminate it from a lineage of dogs.”


In case you have not heard of that gene Bonnie talked about, here is a news item from 2007: A MYSTERY OF DRUG SENSITIVITY IN DOGS CAN BE PUT TO REST! “When given a high dosage of ivermectin heartworm medication, many Collies developed severe neurological signs that often resulted in death due to respiratory arrest. Statistical data on drug sensitivity included Collies, Australian Shepherds, Bearded Collies, Border Collies[?], Shetland Sheepdogs, etc. and drugs ranging from an over-the-counter anti-diarrhea medication (Loperamide) and pain controller Butorphanol to some chemotherapy drugs. The mystery has finally been solved. A recent study by Dr. Katrina Mealey has identified that the problem of drug sensitivity relates to a genetic mutation in the multidrug-resistance gene (MDR1). One of the responsibilities of the gene MDR1 is the production of a protein called P-glycoprotein (P-gp). This protein allows many toxins and drugs to be removed from the brain. An affected dog lacks functional P-glycoprotein that leads to toxins not being pumped out of the brain and, as a consequence, to an abnormal neurological reaction. The mutation has an autosomal recessive mode of inheritance which means that, in order to be affected (super-sensitive to these drugs), a dog has to have both gene [alleles] mutated. However, even the presence of a single mutation increases drug sensitivity in a dog. A new DNA test for the presence of the mutation MDR1 gene allows for the detection of affected dogs as well as dogs carrying a single mutation. Knowing the dog’s status will help veterinarians to properly administer treatment and will help breeders to eliminate this disease in their bloodlines. To learn more about ordering the test, see


A report from Washington State University listed these dubious statistics: “Shetland Sheepdogs (Shelties) 15%, Long-haired Whippets 65%, Silken Windhounds 30%.” However, the Long-haired Whippet and the Silken Windhound are the same “breed”, having begun by people surreptitiously cross-breeding Whippets and Shelties. The only reason there are two names is “politics”... people who wanted to control the “new breed” not getting along with each other and breaking off to start a new breed club. So, when you give two widely different percentages for the same [recent] breed, it casts a shadow of doubt on your statistics. Since Whippets are not listed as affected by MDR1, and the crossbreed statistics are much higher than purebred Shelties, the conclusion is that the “inventors” of the Silken/Longhaired-W. started their lines with affected Shelties in that 15% or 65% gene pool.


WSU’s listing of 5% incidence in the German Shepherd Dog (GSD) might also be suspect—pedigrees and assurance of ancestry are not available from them. I have been a GSD owner since 1947, have bred them since 1966, have produced hundreds of puppies, and have handled & judged GSDs owned by hundreds of other people, and have never come across a case of MDR1 mutation shown by reaction to ivermectin. I do not believe it is in the breed.

Ivermectin vs. other drugs: Here, as additional information, is a comparison of some of the statistics on adverse effects of the various heartworm preventatives currently on the market. The data in the following list was compiled from the Food and Drug Administration listing of Adverse Drug Experience Reports, . The number of deaths per year is significant, although comparative percentages are not given. Selected other adverse events are also reported.

Ivermectin, Oral, Dogs (Heartgard & other brands) Year approved: 1987
Number of Adverse Drug Experience (ADE) Reports in FDA through 7 June 2007: 1,069 (per year: 53)
Total Deaths: 126 (6 per year since FDA approval); Anemia: 6; Platelets low: 3; autoimmune hem: 3.
Reports of ineffectiveness against heartworm: 10 per year

Ivermectin & Pyrantel combination, Oral, Dogs (Heartgard Plus): Year approved: 1993
Number of Adverse Drug (ADE) Reports in FDA through 7 June 2007: 9,871 (705/yr)
Total Deaths: 97 (7/yr); Selected other adverse events reported: Convulsion(s): 197; Anemia: 25; Autoimmune hemolytic anemia: 20; Platelets low: 9. Reports of ineffectiveness against heartworm: 156/yr

Milbemycin, Oral, Dog (Interceptor™ brand name) Year approved; 1995
ADE Reports in FDA through 7 June 2007: 4,745 (395/yr)
Total Deaths: 159 (13/yr); Convulsions: 268; Anemia: 29; autoimmune hem: 15; Platelets low: 1
Reports of ineffectiveness against heartworm (total): 2757.
Ineffective against heartworm reports per year: 230

Milbemycine oxide with Luferon, Oral, Dogs (Sentinel™): Year approved: 1995
ADE Reports in FDA through 7 June 2007: 1,777 (148/yr)
Total Deaths: 43 (5/yr); Convulsions: 109; Anemia: 10; autoimmune hem.: 8; others: 4; Platelets low: 12
Total reports of ineffectiveness against heartworm: 775 (65/yr)

Selamectin, Topical, Dogs (Revolution™) Year approved: 1999
ADE Reports through 7 June 2007: 10,917 (1,365/yr)
Total Deaths: 217 (27/yr); Convulsions: 339; Anemia: 60; Autoimmune hem: 16; Other anemia: 37; Platelets low: 59
Total reports of ineffectiveness against heartworm: 3,855 (481/yr)
Selected other ineffectiveness reports: fleas: 1,622; ticks: 501; ear mites: 206; mites: 61; sarcoptes mites: 56; other ectoparasites: 11; treating for hookworms: 11; hookworm prevention: 45. Selamectin lufenuron* is a once-monthly topical liquid applied to the skin at the back of the neck and sold as a preventative for heartworm and to control fleas (by preventing flea eggs from hatching, but it does not kill adults) plus sarcoptic and ear-mites in dogs. Revolution has about 4 to 5 times the fatality rate of other wormers.
     * Luferon, Lufenuron is also sold under the brand name of “Program.” Lufenuron is an insect egg killer; will not work on adult nematodes, it is said. It is sold by dog weight. The active ingredient is Luferon and is promoted as a “flea contraceptive”—prevents fleas from successfully breeding but does not kill adult fleas. Program (Lufenuron) and Sentinel (Luferon/Mibemycin Oxime) break the reproductive cycle by preventing flea eggs from developing. Sentinel also kills heartworm larvae, adult roundworm, hookworm and whipworm. There may be more recent and improved medications you can research. #09111312



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Fred Lanting is an internationally respected show judge, approved by many registries as an all-breed judge. He consults and presents seminars worldwide on such topics as Gait-&-Structure, HD & Other Orthopedic Disorders, and The GSD.


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