Hartz Companion Animal - Roundworms, Hookworms, and Pyrantel Pamoate

Roundworms, Hookworms, and Pyrantel Pamoate

Internal helminth parasites arepotential causes of primary disease in dogsand cats and zoonotic diseases in humans.Canine and feline parasite surveysfrequently list roundworms (Toxocaracanis, Toxocara cati, Toxascaris leonina) andhookworms (Ancylostoma caninum,Ancylostoma tubaeforme, Ancylostomabraziliense, Uncinaria stenocephala) ascommon helminths. Numerousanthelmintics, representing severalchemical classes, are available fortreatment and control of canine and felineroundworm and hookworm infections.

IN THIS ISSUE:Roundworms, Hookworms,and Pyrantel Pamoate................. 1The American Kennel ClubWelcomes Two New Breeds ...... 5Ask the Vet ................................ 7Hartz Mountain Partners with the AKC to Benefit Veterinarians ................. 8

T. leonina can infect both dogs and cats.Both T. canis and T. cati usually undergohepatotracheal migration before becomingestablished in the small intestine. In olderdogs and cats, a greater number (but notall) of migrating larvae are diverted toextraintestinal tissue. T. leonina does notundergo extraintestinal migration. Thetime from exposure to the parasite untilmature worms are present in the intestine

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Among them are the benzimidazoles(fenbendazole), the macrocyclic lactones(ivermectin, milbemycin oxime), thetetrahydropyrimidines (pyrantel pamoate),and the heterocyclic compounds(piperazine). Pyrantel pamoate has treatedroundworm and hookworm infectionssafely and effectively for many years.Specific knowledge of both parasites andparasite control products is essential forsuccessfully controlling parasitic diseasesand preventing their transmission tohumans. This article reviews the behaviorof common canine and feline ascarids andhookworms, as well as the properties ofpyrantel pamoate.

ROUNDWORMSRoundworms affecting dogs and cats

(T. canis, T. cati, T. leonina) are large (up to4.5 inches), stout worms that live as adultsin the lumen of the small intestine (Figure1). T. canis are commonly found in dogs,while adult T. cati are restricted to cats.

Byron L. BlagburnDistinguished University ProfessorDepartment of PathobiologyCollege of Veterinary MedicineAuburn University

Figure 1— Toxocara canis (onbottom) and Dipylidium caninumfrom a dog’s intestine.

2 HARTZ® COMPANION ANIMALSM • DECEMBER 2004 • VOL. 2, NO. 4

Consulting EditorsAlbert Ahn, DVM

Corporate Vice PresidentChief Scientific OfficerThe Hartz Mountain Corporation

Bruce TrumanDivisional Vice President Animal Health and NutritionThe Hartz Mountain Corporation

HARTZ® COMPANION ANIMALSM

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varies based on the infection route but isgenerally 2 to 5 weeks.

Recent surveys show that T. canis and T.cati remain prevalent in pets. One survey of6,458 dogs from U.S. shelters indicated thatT. canis eggs (Figure 2) were present in thefeces of almost 15% of the samplepopulation. Although the prevalence wasless in adult dogs, the survey results indicatethat T. canis is not restricted to puppies.

Regardless of geographic location, T.canis is a common parasite of dogs becausethere are several routes for potentialinfection. These include embryonated eggs(Figure 3), transplacental transmission,transcolostral transmission (less commonfor T. canis), and ingestion of transporthosts such as rodents and rabbits.Transplacental transmission accounts largelyfor the prevalence of T. canis in neonataland juvenile dogs. Although age-associatedimmunity aids in the expulsion of some T.canis adults as dogs mature, it is not

completely effective in parasitic elimination.T. canis is important because of its

ability to produce primary disease in dogsas well as several extraintestinal diseasesyndromes known as larva migrans inmany hosts, including humans. Wheningestion of embryonated eggs (Figure 3)results in migration and damage tointernal organs, the syndrome is referredto as visceral larva migrans (VLM). VLMis observed most often in childrenyounger than 3 years of age. Encystedlarvae induce nodules in such organs asthe liver, lungs, kidney, and brain. Theseinfections generally manifest as profoundeosinophilia, pneumonitis, andhepatomegaly. In older children (generally3 to 13 years), the larvae apparently have amore pronounced predilection for theposterior chamber of the eye. Theresulting granulomatous retinitis is thehallmark of this second syndrome, knownas ocular larva migrans (OLM). OLM canresult in severe ocular damage andsubsequent retinal detachment, loss ofvision, and even blindness. Interestingly,OLM can occur in the complete absenceof eosinophilia and signs or evidence ofVLM. Although T. cati is thought to beless-often associated with thesesyndromes, recent research indicates thatit, too, can cause them.

Adult female roundworms are prolificegg producers. For example, T. canis femalesare estimated to produce between 25,000and 85,000 eggs/day while T. cati femalescan produce between 19,000 and 24,000eggs/day. Given these egg-production rates,it is easy to see how environments caneventually harbor large numbers of eggs.Parasite reproductive rates, combined withresistance of embryonated eggs to adverse

environmental conditions, can increaseexposure and infection risks to both petsand humans.

HOOKWORMSHookworms are small (up to about

0.75 inch), whitish or reddish-brownworms with hooked anterior ends (hencethe name). Adults reside in the smallintestine of dogs or cats (Figure 4).Ancylostoma spp include A. caninum (theuniversally distributed canine hookworm),A. tubaeforme (the feline hookworm), andA. braziliense (found in both dogs and catsin the subtropical United States). In theaforementioned survey, almost 20% of6,458 fecal samples from shelter dogs

Figure 2— Unembryonated eggof Toxocara canis from dog feces.

Figure 4— Ancylostoma caninumfrom a dog’s intestine.

Figure 3— Embryonated egg ofToxocara canis from a public park.

yielded A. caninum eggs. A singleUncinaria species (U. stenocephala) occursin dogs (but rarely in cats) living intemperate regions worldwide.

The hookworm developmental cycleincludes a free-living phase in which larvaehatch from eggs (Figure 5) and developthrough three distinct stages. The thirdenvironmental larval stage (infective stage)enters the host by either oral ingestion orskin penetration. Most (but not all) orallyingested larvae establish in the intestinewithout extraintestinal migration. Thosethat penetrate the skin follow a vascular orpulmonary migration before becomingestablished in the small intestine. Inaddition, both prenatal (transplacental)and transmammary transmission canoccur. The reservoir for such larvae issomatic, as is the case with T. canis.

Hookworms may cause dermal,pulmonary, and intestinal diseases (Figure6). The latter is most common in dogs.In young dogs, A. caninum–relatedhemorrhagic enteritis can be a peracute,life-threatening disease. The

transmammary route of infection can leadto the establishment of very high wormburdens in neonatal dogs in a short time.The remaining species are less significantbut not always innocuous pathogens.A. caninum, similar to T. canis, is a prolificegg producer. It is estimated that matureA. caninum females can produce up to20,000 eggs/day, resulting in substantialenvironmental reservoirs of infectivelarvae in a rather short period.

Free-living infective larvae of someAncylostoma spp may penetrate humanskin and subsequently migrate for briefperiods, causing reddish, pruritic,serpentine lesions. This condition isreferred to as cutaneous larva migrans(CLM) or creeping eruption. Althoughless significant than the larva migranssyndromes caused by roundworms, thehookworm-related cutaneous syndromeremains a concern for veterinarians andpet owners. A. braziliense larvae appear tobe the most common cause, althoughcases of A. caninum– and U. stenocephala–induced CLM have been documented.

PYRANTEL PAMOATE:CHEMICAL PROPERTIES,EFFICACY, AND SAFETY

Pyrantel salts have been usedeffectively for parasite control for almostfour decades. Although initiallyintroduced to control sheep parasites,subsequent formulations were producedfor cattle (not currently FDA approved),swine, horses, dogs, and cats. Pyrantel is atetrahydropyrimidine compound. Pyrantel

pamoate (also called pyrantel embonate;Figure 7) is the derivative currentlymarketed in several formulations for usein dogs and cats (Table 1). It is poorlyabsorbed from the stomach and intestinefollowing oral administration. Between50% and 70% of pyrantel pamoate appearsunchanged in feces, which accounts for itsefficacy and safety (it does not enter theblood system). Pyrantel pamoate is foundin the blood of treated animals at a rate ofless than 1 µg/ml of blood. Anotherbenefit of poor absorption is that efficacyis enhanced because pyrantel pamoateremains in contact with the parasitestargeted for removal.

Pyrantel pamoate kills parasites byattacking their nervous system, resultingin irreversible paralysis of the parasite’smusculature. This is important becauseparasites can recover from brief exposureto other parasiticides but not fromexposure to pyrantel pamoate. When dogs and cats are allowed to eat beforetreatment, the passage of pyrantelpamoate through the intestinal tract isslowed, permitting prolonged contact timewith parasites and thus increasing efficacy.

Pyrantel pamoate is available as aflavored suspension, tablet, or chewabletablet (Table 1). It is 95% effective againstascarids (T. canis, T. leonina) andhookworms (A. caninum, U. stenocephala) indogs at a dose of 5 mg/kg. Because efficacymight be decreased in puppies weighingless than 2.2 kg, a dose of 15 mg/kg given 30 minutes after a light meal isrecommended. Pyrantel pamoate may be

HARTZ® COMPANION ANIMALSM • DECEMBER 2004 • VOL. 2, NO. 4 3

Figure 5— Unembryonated eggsof Ancylostoma caninum from dogfeces.

Figure 6— Severe hookwormdisease caused by Ancylostomatubaeforme in a cat.

S

CH CH

N

N

CH3

CH2

HO2C

2

OH

Figure 7— Chemical structure of pyrantel pamoate (embonate).

4 HARTZ® COMPANION ANIMALSM • DECEMBER 2004 • VOL. 2, NO. 4

combined with other compounds (e.g.,ivermectin, febantel, praziquantel) toprevent heartworm infection and eliminatetapeworms and whipworms as well asascarids and hookworms (Table 1).Formulations containing ivermectin andpyrantel pamoate are available as chewabletablets and are effective against A.braziliense. Though pyrantel pamoate is notapproved for use in cats as a stand-aloneproduct, it is used safely and effectively incats at a dose of 20 mg/kg. Pyrantelpamoate is combined with praziquantel ina tablet formulation for removal of ascarid(T. cati), hookworm (A. tubaeforme), andtapeworm infections (Table 1).

The safety of pyrantel pamoate isexceptional. The toxic dose in dogsexceeds the therapeutic dose by almost140 times. Pyrantel pamoate can beadministered to dogs at four times therecommended dose daily for up to 3months without inducing adverse events.Another safety attribute is that it can besafely administered to pregnant animals.This is important because deworming

spectrum of activity. Few anthelminticshave retained their utility and widespreaduse in the companion animal market for40 years. Continued success of pyrantelpamoate is testimony to its safety,efficacy, and convenience.

SUGGESTED READINGBlagburn BL, Lindsay DS, Vaughan JS, et al: Prevalence

of canine parasites based on fecal flotation. CompendContin Educ Pract Vet 18:483–509, 1996.

Clark JN, Daurio CP, Barth DW, Batty AF: Evaluationof a beef-based chewable formulation of pyrantelpamoate against induced and natural infections ofhookworms and ascarids in dogs. Vet Parasitol40:127–133, 1991.

Lynn RC: Antiparasitic drugs, in Bowman DD (ed):Georgis’ Parasitology for Veterinarians, ed 8.Philadelphia, WB Saunders, 2003, pp 244–286.

Nolan TJ, Hawdon JM, Longhofer SL, et al: Efficacy ofan ivermectin/pyrantel pamoate chewableformulation against the canine hookworms Uncinariastenocephala and Ancylostoma caninum. Vet Parasitol41:121–125, 1992.

Reinemeyer CR, Courtney CH: Antinematodal drugs, inAdams HR (ed): Veterinary Pharmacology andTherapeutics, ed 8. Ames, Iowa State UniversityPress, 2001, pp 947–979.

Vanden Bossche H, Theinpont D, Janssens PG (eds):Chemotherapy of Gastrointestinal Helminths. NewYork, Springer-Verlag, 1985.

bitches and queens before they whelp orqueen reduces the number of eggs shedinto the environment, which in turndecreases the challenge rate fromenvironmental eggs and larvae.

However, most ascarid and hookworm infections are acquired either transplacentally or via milk andcolostrum. Pyrantel pamoate is approvedfor use in puppies as young as 2 weeks ofage. This, too, is important becausetreating puppies regularly at a very earlyage (i.e., at 2, 4, 6, and 8 weeks) can bothprevent acute ascarid- and hookworm-related disease and reduce or eliminatethe shedding of ascarid and hookwormeggs in feces. The latter is important inpreventing the transmission of ascaridsand hookworms from pets and theirenvironments to humans.

In summary, pyrantel pamoate isamong the safer and more effectiveanthelmintics for removing ascarids andhookworms from dogs and cats. It isavailable in convenient formulations andcombination products, which extends its

TABLE 1: Examples of Parasite Control Products Containing Pyrantel Pamoate

Product Name Host Species Formulation Ingredients Target Parasites

D-Worm 60, D-Worm120 (Farnum)

Dogs Chewabletablet

Pyrantel pamoate Toxocara canis, Toxascaris leonina, Ancylostomacaninum, Uncinaria stenocephala

Hartz® Rid Worm™(Hartz)

Dogs Chewabletablet


Nemex Tabs, Nemex-2Suspension (Pfizer)

Dogs Tablet/Suspension


Heartgard Plus (Merial) Dogs Chewabletablet

Pyrantel pamoate,ivermectin

Toxocara canis, Toxascaris leonina, Ancylostomacaninum, Ancylostoma braziliense, Uncinariastenocephala, Dirofilaria immitis

Iverhart Plus (Virbac) Dogs Chewabletablet



Tri-Heart Plus(Schering Plough)

Dogs Chewabletablet



Drontal (Bayer) Cats Tablet Pyrantel pamoate,praziquantel

Toxocara cati, Ancylostoma tubaeforme, Taeniaspp, Diplydium spp

Drontal Plus (Bayer) Dogs Tablet Pyrantel pamoate,praziquantel,febantel

Toxocara canis, Toxascaris leonina, Ancylostomacaninum, Uncinaria stenocephala, Trichuris vulpis,Taenia spp, Diplydium spp, Echinococcus spp


Black Russian Terrier

Neapolitan Mastiff

The American Kennel Club WelcomesTwo New Breeds

reliable.” Black Russian Terriers thrive in every clime, from theArctic to Australia. The breed’s tousled, double coat is not knownto shed profusely. Grooming fashions for this dog may call tomind the Bouvier or the Giant Schnauzer, but the Black RussianTerrier is unmistakably a breed unto itself.

The Neapolitan Mastiff (above) is an ancient breed datingfrom the time of Alexander the Great. Also known as the“Mastino,” he is a heavy-boned, massive dog bearing loose skin allover the body, abundant wrinkles and folds on the head, plus avoluminous dewlap. Referenced in the works of Greek and Latinwriters and artists, the ancient molossus developed by Alexanderthe Great is believed to be the forefather of the modernNeapolitan Mastiff. While the molossus was used to fight tigers,lions, elephants, and men in battle, today’s Mastino is a calm,docile creature—not a fighting dog. Breed lore holds that thedog’s unique type was developed purposely as an alarmingly uglydog whose looks alone were enough to intimidate any intruder.Fanciers of the breed report that Neapolitan Mastiffs arecourageous but not aggressive, wary yet approachable. In additionto considering its massiveness (average weight of mature dogs is150 lb), potential owners must also take into account the breed’stendency to drool and a distinctive odor characterized as a“woodsy” smell. Clients seeking a canine jogging partner shouldlook elsewhere, as the Mastino was not bred for endurance.

I n the ever-changing landscape of companion animal ownership,it can often be challenging to discern just what that furryquadruped is on the other end of a client’s leash. As of May 1,

2004, The American Kennel Club (AKC) officially recognizes 152breeds of dogs within seven groups: Sporting, Hound, Working,Terrier, Toy, Non-Sporting, and Herding. Counting nine breedsthat are divided into varieties (a division of a breed based on coat,color, or size), the grand total of distinct breeds that are eligible tocompete for championship points at AKC shows climbs to animpressive 164 breeds and varieties. Newest to join the ranks of theWorking Group are two formidable breeds: the Black RussianTerrier and the Neapolitan Mastiff.

The Black Russian Terrier (below) is a relatively new breedcreated in the 1930s in the then Soviet Union to meet the needfor security dogs. The main crosses of the breed’s developmentwere made among Giant Schnauzers, Rottweilers, and AiredaleTerriers. The Black Russian Terrier also bears traces ofNewfoundlands, Great Danes, and several Russian breeds, such asthe Ovcharka. Once known as the Black Pearl of Russia, the“Blackie” is a loyal companion and loving pet, a nimble black flashon the agility course, a keen-witted obedience dog, and a guardianwithout peer. Mature dogs measure between 27 and 30 inches,while mature bitches are between 26 and 29 inches. According tobreed experts, elbows and hips are the breed’s only significanthealth issues. The breed standard describes the temperament: “TheBlack Russian Terrier is a calm, confident, andcourageous dog with a self-assurance which issometimes rather aloof toward strangers. Theyare highly intelligent,(and) extremely

FREE POSTER OFFERConsult the Hartz/AKC Guide to Purebred Dogs poster to seethese new breeds within the context of the American purebreduniverse. To obtain a free copy for your office, call the HartzConsumer Affairs Department at 1-800-275-1414,or email usat [email protected]. Call today; quantities are limited.

Albert Ahn, DVM, is a veterinarian, Corporate Vice President, andChief Scientific Officer of The Hartz Mountain Corporation.

ASK THE VET


WE WANT TO HEAR FROM YOU!• Have questions or comments? Call our Consumer Relations Department at 800-275-1414 and ask to speak to a Hartz staff

veterinarian or email us at [email protected].• To obtain a Hartz Veterinary Catalog of products, please call 800-999-3000 x5118 or email us at [email protected].

QA

Can pyrantel pamoate be used inpregnant or nursing animals?

Pyrantel pamoate, a pyrimidine anthelmintic, iscommonly used to treat and prevent hookworm(Ancylostoma caninum, Uncinaria stenocephala) andascarid (Toxocara canis, Toxascaris leonina) infestationin dogs. Pyrantel causes paralysis in susceptibleparasites through neuromuscular blocking effects.According to veterinary pharmacology references,pyrantel is considered safe to use during pregnancyand in nursing animals.

Articles found in the Hartz Companion AnimalSM newsletter can be copied and distributed to your colleagues, staff, and clients.Additional newsletters may also be obtained by contacting us at [email protected] or by phone at 800-275-1414.

QA

How will Hartz be observing Pet DentalMonth in February?

To help celebrate Pet Dental Month, Hartz hascreated a dental care brochure for pet owners thatdetails the many benefits of regular veterinary visits,teeth cleaning, and home dental care. Hartz will alsobe giving away sample packs of Hartz Breath Strips.To order brochures and breath strips for your clinic,you can call the Hartz Consumer RelationsDepartment at 800-275-1414 or [email protected].

QA

What types of products should beincluded in a home dental care routine?

In addition to regular veterinary examinations andteeth cleaning, home dental care is an importantpart of maintaining a pet’s oral health. Studies showthat brushing a dog’s teeth on a regular basis is thebest method of removing plaque and preventing itsbuildup.

Rawhide dog treats have been used for many yearsto satisfy a dog’s natural chewing needs. Theabrasive action of rawhide chewing also helpsreduce plaque and calculus. Hartz® Dental™ Flavor Infused™ Chew-Dent™ chews are madethrough a patented process that allows flavor topermeate throughout the beef hide. Dogs chewlonger, helping to remove plaque up to 54% andtartar up to 68%.

Chew toys are another option. Most have raised tipsthat massage gums and help decrease plaquebuildup. They also provide the necessary chewingexercise to strengthen gums as well as providingrelief from boredom, frustration, or anxiety.

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Hartz Mountain Partners with The AKC to Benefit Veterinarians

This summer, The Hartz Mountain Corporation becamethe official sponsor of The American Kennel Club’s VeterinaryOutreach Program. Uniting the world of purebred dogs withthe veterinary community, the program offers resources in sup-port of veterinary students, practitioners, and researchers, creat-ing a forum for the exchange of information about canine healthand welfare and providing scholarships for future practitionersand researchers.

“The Hartz Mountain Corporation values its relationshipwith the veterinary community as evidenced by the creation ofthe Veterinary Outreach Program,” said Albert Ahn, DVM,Corporate Vice President and Chief Scientific Officer at Hartz.“We are committed to providing high-quality pet products andcelebrating the human–animal bond.”

The sponsorship of the AKC’s Vet Outreach Program byHartz comes on the heels of a very successful venture between

the two organizations that brought the “DOGNY Help a Hero”toy series to market. Hartz’ sales of the popular dog toy, bearingthe likeness of real-life search and rescue dogs, have contributedover $1 million to the AKC CAR Canine Support and ReliefFund to support professional and volunteer canine search andrescue organizations throughout the United States.

AKC President Dennis B. Sprung stated, “The AKC isdelighted to be working with The Hartz Mountain Corporationon the many programs that heighten the appreciation andawareness of the role that dogs play in our lives, whether they be search and rescue dogs, working service dogs, show dogs,or household pets. Now, their sponsorship of the VeterinaryOutreach Program allows us to bring a greater level of supportto the professionals who uphold the human–animal bond—ourcurrent and future veterinarians, veterinary researchers, and vet-erinary technicians.”

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Hartz Companion Animal - Roundworms, Hookworms, and Pyrantel Pamoate