Parasitic worms are among the most common issues that are routinely addressed in veterinary medicine. They pose an ongoing threat to the wellbeing of all companion and working animals. Worm infestations are regularly reported in dogs, cats, horses, cattle and a wide variety of exotic companion animals. 

Worms can also impact the bond between humans and their companion animals due to the potential for cross-species infection (zoonosis).¹ To prevent this issue from arising, deworming practices have been developed over the years; these are important strategies in maintaining the relationships that owners and managers have with their animals.²

Parasitic worms live in the intestines of nearly all horses, with small numbers being tolerated and causing no noticeable effect on the horse’s overall health. Larger infestations of intestinal parasites can cause a wide range of problems however, including ill thrift, colic, digestive issues, diarrhea and death.³

Exotic animal species are also becoming more and more common among pet enthusiasts and on properties that are being managed for recreational or commercial hunting. In the former, the stress of captivity coupled with a closed environment can lead to potentially heavy burdens of parasites with direct life cycles.²

The method of transmission of worms to an animal is typically determined by the life cycle of the worm species involved. In most cases, worm eggs are inadvertently ingested and develop inside the digestive tract or lungs, where they may or may not cause disease. Eggs produced by adult worms are then shed in the animal’s feces where they can potentially infect humans or other animals.

Fenbendazole 

Fenbendazole is a broad spectrum methylcarbamate benzimidazole anthelmintic that is used for the reduction and removal of nematode and protozoal parasites in many species. In horses, fenbendazole is labeled for the removal of large strongyles (Strongylus edentatus, S equinus, S vulgaris, Triodontophorus spp), small strongyles (Cyathostomum spp, Cylicocyclus spp, Cylicostephanus spp, Cylicodontophorus spp), ascarids (Parascaris equorum) and pinworms (Oxyuris equi). Benzimidazole resistance has been noted in Cyathostomum spp found in the United States.⁴

Fenbendazole’s mechanism of action is believed to involve the disruption of intracellular microtubular transport systems by binding selectively and damaging tubulin, which prevents tubulin polymerization and inhibits microtubule formation. Fenbendazole has activity against adult life cycle stages of susceptible parasites and may have larvicidal and ovicidal activity against certain parasites.⁴

Fenbendazole does not typically cause side effects at labeled dosages, and its use is considered safe in pregnant animals. Hypersensitivity reactions secondary to antigen release by dying parasites may occur, particularly at high dosages. In rare instances, side effects of fenbendazole in dogs or cats may include salivation, vomiting, and diarrhea. Rarely, allergic reactions can develop.^4,5 If an animal shows signs of an allergic reaction (e.g., facial swelling, itchiness, hives, diarrhea, seizures, shock), veterinary care should be sought. 

Moxidectin

Moxidectin is a milbemycin-class antiparasitic that is FDA-approved for use in cattle, dogs, cats, ferrets, sheep, and horses. Its primary mode of action drugs is to affect chloride ion channel activity in the nervous system of nematodes and arthropods. The drug binds to receptors that increase membrane permeability to chloride ions, inhibiting the electrical activity of nerve cells in nematodes and muscle cells in arthropods and causing paralysis and death of the parasites.⁴

Milbemycins also enhance the release of γ-aminobutyric acid (GABA) at presynaptic neurons. GABA acts as an inhibitory neurotransmitter and blocks postsynaptic stimulation of the adjacent neuron in nematodes or the muscle fiber in arthropods.^4,5

In horses and ponies 6 months of age and older, moxidectin is indicated for the treatment and control of (Adapted from Plumb’s Veterinary Drugs):

Large strongyles: Strongylus vulgaris (adults and L4, L5 arterial stages), S edentatus (adults and tissue stages), Triodontophorus brevicauda (adults), T serratus (adults)

Small strongyles (adults and undifferentiated luminal larvae): Cyathostomum spp; Cylicocyclus spp; Cylicostephanus spp; Coronocyclus spp, Gyalocephalus capitatus (adults); Petrovinema poculatus (adults); undifferentiated lumenal larvae

Encysted cyathostomes: Late L3 and L4 mucosal cyathostome larvae

Ascarids: Parascaris equorum (adults and L4 larval stages)

Pinworms: Oxyuris equi (adults and L4 larval stages)

Hair worms: T axei (adults)

Large-mouth stomach worms: Habronema muscae (adult)

Stomach bots: Gasterophilus intestinalis  

Adverse effects with oral and topical formulations of moxidectin in dogs may include lethargy, vomiting, ataxia, anorexia, diarrhea, nervousness, weakness, increased thirst, and itching. Adverse effects are minimal in cattle and appear to be minimal in horses at labeled doses.⁴

Where to buy Fenbendazole + Moxidectin

Fenbendazole + Moxidectin is available in the U.S. through veterinary custom compounding companies. FENBENDAZOLE 10 GM/SCOOP + MOXIDECTIN 0.15 GM/SCOOP, ORAL POWDER, 5 SCOOPS (39CC SCOOP) by NexGen Pharmaceuticals provides superior relief from parasitic worm infestations cattle, dogs, cats, ferrets, sheep, horses and a variety of exotic species.

This product carries numerous potential drug interactions. Please consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

¹nsf.gov.

²Merck Veterinary Manual.

³extension.okstate.edu.

⁴Plumb’s Veterinary Drugs.

⁵Mason ME, Voris ND, Ortis HA, Geeding AA, Kaplan RM. Comparison of a single dose of moxidectin and a five-day course of fenbendazole to reduce and suppress cyathostomin fecal egg counts in a herd of embryo transfer-recipient mares. J Am Vet Med Assoc. 2014;245(8):944-951.

⁶Daniels SP, Proudman CJ. Ovicidal efficacy of fenbendazole after treatment of horses naturally infected with cyathostomins. Vet Parasitol. 2016;227:151-156.

⁷Pittman JS, Myers GH, Stalder KJ, Karriker LA. Effect of fenbendazole on shedding and embryonation of Ascaris suum eggs from naturally infected sows. J Swine Health Production. 2015;23(5):252-263.