Praziquantel

The life cycle of the parasite is based on a predator-prey relationship, as depicted above.

The adult tapeworm is small (1-4 mm) and resides in the intestinal tract of the definitive host (wild or domestic canids). Eggs from the adult tapeworm are shed in the feces of the infected canid. Rodents such as mice and voles serve as the intermediate host for E. multilocularis. Eggs ingested by rodents develop in the liver, lungs and other organs to form multilocular cysts. The life cycle is completed after a canid consumes a rodent infected with cysts. After ingestion of the infected rodent, larvae within the cyst develop to adult tapeworms in the intestinal tract of the canid. Eggs may begin to be passed in the feces of the canid approximately 28 days later.

This parasite poses a serious public health problem because of the possibility for human involvement in the life cycle. If eggs shed by an infected canid are accidentally ingested, a highly pathogenic condition (Alveolar Hydatid Disease) results from development of the cyst stage in humans.

The original geographic distribution of E. multilocularis was primarily confined to northern areas of North America. Current evidence indicates migration of the parasite well into the continental United States.^2,3

Domestic dogs living in E. multilocularis endemic areas that roam freely with the opportunity to catch wild rodents are at risk for infection. Pet owners should be advised on how to minimize this risk. Proper restraint of roaming dogs should be encouraged, along with regular treatment with Praziquantel Injection solution, following the dosing schedule aforementioned and precautions indicated below.

Additional information on the life cycle and epidemiology of this parasite is available in veterinary parasitology texts.^4,5

Diagnosis:

Diagnosis of E. multilocularis in canids is difficult. The adult tapeworm produces no clinical signs of infection.Tapeworm segments (proglottids) are usually not observed in the feces. E. multilocularis eggs, observed using microscopic fecal examination procedures, are similar in appearance to the common taeniid species of canids such as Taenia pisiformis.

Assistance in the diagnosis of E. multilocularis may be available from a state veterinary diagnostic laboratory. Additional information regarding areas where E. multilocularis is suspected or has been confirmed may be obtained from area veterinary schools or the Centers for Disease Control in Atlanta, GA.

Treatment:

Dogs infected with E. multilocularis should be treated to prevent exposure of humans to infective eggs and to reduce perpetuation of the parasite’s life cycle.

The dosage of Praziquantel Injection solution for removal of E. multilocularis is the same as that indicated for the removal of the other tapeworm species listed on the label. Laboratory efficacy studies have demonstrated the recommended dosage is 100% efficacious for removal of this tapeworm.

Under condition of continual exposure to wild rodents, retreatment of the dog at 21-26 day intervals is recommended to prevent the shedding of infectious eggs

Precautions:

Strict hygienic precautions should be taken when handling dogs or feces suspected of harboring E. multilocularis. Infected dogs treated for the first time with Praziquantel Injection solution and dogs treated at intervals greater than 28 days may shed eggs in the feces after treatment. The animal should be held in the clinic during this interval and all feces should be incinerated or autoclaved. If these procedures are not possible, the eggs can be destroyed by soaking the feces in a sodium hypochlorite (bleach) solution of 3.75% or greater.⁶ All areas where the animal was maintained or in contact with should be thoroughly cleaned with sodium hypochlorite and allowed to dry completely before reuse.

OVERDOSAGE:

The safety index has been derived from controlled safety evaluations, clinical trials and prior approved use in foreign countries. Dosages of 5 times the labeled rate at 14 day intervals to dogs as young as 4 weeks did not produce signs of clinical toxicity following either intramuscular or subcutaneous injections. No significant clinical chemistry, hematological, cholinesterase or histopathological changes occurred. Dosages of 5 times the labeled rate at 14 day intervals to kittens as young as 5 1/2 weeks did not produce signs of clinical toxicity following either intramuscular or subcutaneous injections. Symptoms of overdosage (33.8 to 40 times the labeled dosage rate) in adult dogs included vomition, excessive salivation and depression, but no deaths. Symptoms of overdosage (10 to 20 times the labeled dosage rate) in adult cats included vomition, depression, muscle tremors and incoordination. Deaths occurred in 5 of 8 cats treated subcutaneously and in all 8 injected intramuscularly at doses greater than 20 times the label rate.

CONTRAINDICATIONS:

There are no known contraindications to the use of praziquantel.

PREGNANCY:

Praziquantel Injection has been tested in breeding and pregnant dogs and cats. No adverse effects were noted.

ADVERSE REACTIONS:

Mild side effects were observed in 18 of 189 dogs (9.5%) and 8 of 85 cats (9.4%) administered Praziquantel Injection in field trials. For dogs the majority of these were described as brief pain responses following injections to larger dogs (weighing over 50 lbs.) Two dogs exhibited a brief period of mild vomiting and/or drowsy or staggering gait. The eight cats exhibited either diarrhea, weakness, vomition, salivation, sleepiness, burning on injection and/or a temporary lack of appetite. Local irritation or swelling at the site of subcutaneous injections have been reported for cats.

CAUTION:

Federal law restricts this drug to use by or on the order of a licensed veterinarian.

HOW SUPPLIED:

10 mL vial

50 mL vial

REFERENCES:

¹ Andrews P. Pharmacokinetic Studies with Praziquantel Injection in Animals Using a Biological Assay. Veterinary Medical Review, 2/76, pg. 154-165.

² Hildreth MB, Johnson MD and Kazacos KR. 1991. A Zoonosis of Increasing Concern in the United States. Compendium for Cont Ed. 13(5) 727-740.

³ Lieby PD, Carney WP and Woods CE. 1970. Studies on Sylvatic Echinococcosis, III. Host Occurrence and Geographic Distribution of Echinococcus multilocularis in the North Central United States. J Parasit 56 (6) 1141-1150.

⁴ Georgi JR and Georgi ME. 1990. Parasitology for Veterinarians. W.B. Saunders Co. 118-138.

⁵ Soulsby EJL. 1982. Helminths, Arthropods and Protozoa of Domesticated Animals. 7th Edition. Lea & Febigir. 118-138.

⁶ Craig PS and McPharson CNL. 1998. Sodium Hypochlorite as an Ovicide for Echinococcus. Ann Trop Med and Parasit 82(2) 211-213.

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81575053, R.0

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Bimeda, Inc.
Le Sueur, MN 56058
www.bimeda.com
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