If you are reading this blog post, chances are it’s due to our video of a Dipylidium caninum proglottid releasing its egg packets. If you do not know what I am referring to, have a look at either our Instagram or Facebook pages to see the video!
Dipylidium caninum is a cestode and is the most common tapeworm of dogs and cats. It is a segmented intestinal parasitic flatworm. The segments are called proglottids and each proglottid is roughly the size of a grain of rice. Adult tapeworms are usually 6-30 inches in length.
For this tapeworm to be infectious in dogs, cats and rarely humans (known as the definitive hosts), it has to first pass through an intermediate host, the flea (Ctenocephalides spp.). Note that less frequently, the louse can also serve as an intermediate host. The reason an intermediate host is required, is for completion of the tapeworm life cycle. When more than one host is required it is known as an indirect life cycle. Dipylidium caninum is therefore commonly referred to as the flea tapeworm of dogs and cats.
The life cycle
A flea larva (immature flea) has to ingest a tapeworm egg packet. A tapeworm egg packet is filled with multiple eggs. The tapeworm egg develops into a tapeworm larva (immature tapeworm) and then into a cysticercoid as the flea larva matures into an adult flea. The adult flea harbors the infective cysticercoid. When a dog or cat ingests a cysticercoid infected adult flea, the cysticercoid is released into the intestines of the dog or cat and develops into an adult tapeworm. A mature adult tapeworm consists of a head segment (scolex), a neck segment and a body (strobila) made up of multiple segments (proglottids). The head attaches to the small intestinal wall. New proglottids form at the neck and older proglottids are pushed to the posterior (tail). The posterior proglottids at the end of the tail are filled with egg packets. These egg-filled posterior proglottids, also called gravid proglottids, detach and migrate to the anus or are excreted with the feces of the dog or cat. The gravid proglottids dry out and disintegrate, releasing the egg packets into the environment, where the life cycle continues when an egg packet is ingested by a flea larva.
The prepatent period is 14-21 days, therefore approximately 2-3 weeks after the dog or cat ingests a cysticercoid infected adult flea, the dog or cat will start to shed proglottids.
Dogs, cats and humans can not get infected directly from a proglottid since the egg needs to develop further before it can infect mammals.
Since fleas are the intermediate host, for a dog or cat to have this tapeworm, the dog or cat must have ingested a flea. The discussion needs to be had with the owner regarding the presence of fleas in the environment, even if the owner has not actually seen any fleas.
Diagnosis and clinical signs
Dipylidium caninum infections are rarely diagnosed on fecal floats and are more commonly diagnosed based on clinical signs and/or identifying the proglottids on or in the feces, in the perianal region or on the patient’s bedding. Freshly passed proglottids are white, moist, soft, motile and look like cooked grains of white rice or cucumber seeds that are crawling. Dried proglottids are hard, golden in color, not motile and look like sesame seeds. Proglottids can get stuck to the fur in the perianal region and cause perianal irritation and anal pruritus, which is why the most commonly appreciated clinical signs are excessive grooming of the perineum and “scooting” or dragging the perineum across the ground. Migration to the stomach may occur occasionally, which could result in the dog or cat vomiting an adult tapeworm several inches long.
In order to definitively diagnose Dipylidium caninum, the egg packets and/or individual eggs may be identified via fecal float. Another method is examining the proglottid under the microscope. Place the proglottid on a microscope slide to see if the proglottid is releasing its egg packets - as seen in our video! Another technique is to squash the proglottid (+/- a few drops of water or saline) between a slide and a cover slip to see if egg packets are appreciated. Each egg packet contains about 5-30 individual eggs.
Other than perianal irritation, Dipylidium caninum infections don’t usually cause harm to dogs and cats. Heavy infections can however cause weight loss, poor growth, poor coat, abdominal pain, intestinal obstruction, vomiting or diarrhea.
Anthelmintic treatment options include one of the following:
- Praziquantel Injection: use labeled directions
- Praziquantel Tablets (Droncit): use labeled directions
- Drontal Tablets: use labeled directions
- Drontal Plus Tablets: use labeled directions
- Epsiprantel Tablets (Cestex): dog dosage is 5.5 mg/kg PO once, cat dosage is 2.75 mg/kg PO once
Only a single treatment with one of the above anthelmintic medications is required. Sometimes however, a repeat treatment in about 3 weeks is recommended, most notably when there is a significant flea infestation problem due to the risk of the patient reinfecting him/herself by ingesting another cysticercoid infected adult flea.
Part of the treatment protocol should include flea control. The patient and all pets in the household should be placed on a good quality monthly flea prevention, as well as treating the environment.
Prevention consists of keeping dogs and cats on good quality monthly flea prevention.
Dipylidium caninum has a zoonotic potential, but a human must ingest a cysticercoid infected adult flea or louse for infection to occur, making infection in humans low.
*Disclaimer: The information in this blog post is not intended to replace clinical judgement or guide individual care in any matter. Please check any information and values prior to use and use at your own risk.