Can fleas transmit tapeworm?

Summary

Fleas can transmit tapeworms, namely Dipylidium caninum. Fleas act as intermediary hosts for the worms. Flea larvae ingest tapeworm eggs in the environment. The worms grow inside the larvae as they mature into adult fleas. The infected fleas then find a host. If the host animal accidentally consumes an infected flea while oral grooming, it will get infected with the tapeworm.

Details

Fleas as Intermediate Hosts for Tapeworms

Dipylidium caninum

Cat fleas (C. felis), dog fleas (C. canis), and human fleas (P. irritans) can serve as intermediate hosts of several species of cestodes. Dipylidium caninum, the common tapeworm of dogs and cats, is the most prevalent. D. caninum is also called the ‘dog tapeworm’ or ‘double-pored tapeworm’.

D. caninum has a worldwide in distribution. This intestinal parasite mostly affects wild and domestic dogs and cats, but it can also infect human beings. D. caninum is mainly transmitted by fleas and by dog biting lice (Trichodectes canis). The cat flea (Ctenocephalides felis) is the primary intermediate host.

Other Cestodes

Cat fleas can also carry Hymenolepis nana (dwarf tapeworm), Hymenolepis diminuta (rat tapeworm), Hymenolepis microstoma (rodent tapeworm), Hymenolepis citelli, and Dipetalonema reconditum.

How Fleas Transmit Tapeworms

Tapeworm Morphology

Adult tapeworms are long, flat, and ribbon-shaped. They’re usually a light reddish-yellow color. The whole worm is 10-50 cm long, and 2-3 mm wide. The body, or strobila, is made of segmented rectangular units called proglottids. The anterior end holds a suckered hold-fast organ called a scolex. New segments are continually grown behind the scolex to create a chain. This area is called the neck or budding zone.

Each proglottid contains two sets of both male and female reproductive organs. Mature segments have a characteristic elongate, oval shape. They resemble pumpkin or cucumber seeds. Each sexually mature segment (gravid proglottid) contains numerous eggs enclosed in a packet. The round eggs are 38-55 microns in diameter.

Tapeworm Eggs Enter the Environment

Gravid proglottids are expelled from the anus of infected cats or dogs. The egg-containing segments may be excreted in feces, or they may actively wander out of the anus and disseminate eggs as they crawl about. When the proglottids are ruptured or disintegrate, they release many eggs. There are typically 8-16 eggs in each packet. The liberated eggs end up scattered about the ground.

Flea Larvae Consume Tapeworm Eggs

Only larval fleas have chewing mouth-parts. Thus, they’re the only life stage capable of ingesting tapeworm eggs. Flea larvae live in the environment, usually carpeting. There, the flea larvae graze for food. They are voracious feeders, continuing until they’ve had their fill.

While scavenging for food, flea larvae may inadvertently encounter and consume tapeworm eggs. The tapeworm eggs then develop into oncospheres and cysticercoids (larval tapeworm forms) inside the flea larvae.

Tapeworms grow within the flea larvae as it matures and pupates. Due to crowding within the larva, the worms don’t grow much until the flea reaches adulthood. Size significantly increases once flea larvae begin to pupate. Maximum worm size and maturity is reached soon after fleas become adults. One study showed that D. caninum can’t complete development until the flea finds a host. This is due to the increased body heat of the animal.

On arrival in the larval body cavity, tapeworm cysticercoids have an average volume o 1,834 cu. microns. Before flea pupation, the average volume is about 22,984 cu. microns. In the flea pupal stage, the cysticercoids increase in size to 53,000 cu. microns. In the first week of flea adulthood, the worms increases enormously in size to an average of 650,000 cu. microns.

How Dogs & Cats Become Infected

Fleas act as intermediary hosts for tapeworms, eventually passing them on to cats, dogs, and rarely humans.

Tapeworm-infected fleas get accidentally swallowed by dogs and cats during oral grooming. Then the cysticercoids are released into the new host. The cysticercoids reach their final destination in the intestine of the definitive host. They attach themselves with their scolex, growing into adult (strobilate) worms in about 15 days. Ripe proglottids are eventually passed in the feces of the host, starting the cycle all over again.

Pets that are fastidious groomers are more likely to ingest adult fleas carrying D. caninum. Effective oral grooming in removing fleas has been exploited by the worms. In addition, the worms cause ill effects in adult fleas, making them more susceptible to getting groomed off by animals.

Human Infections

Humans who accidentally consume cysticercoids can also develop dipylidiasis. This may occur when a person ingests the saliva of infected pets. For example, if a dog with cysticercoids on its tongue licks a person’s mouth. This is most common with children. Over 80% of human patients with tapeworms are less than 8 years of age. This is because children are generally in closer contact with family pets.

How to Identify Tapeworms Infections

Segments in Stool

Single or chains of proglottids may be noticed in pet feces, or on the fur near their anus. Pet stool is often examined for D. caninum segments to diagnose tapeworms. The stool is usually diarrhea and contains white specks. The worm segments look like small grains of rice, or seeds of pumpkins or cucumbers. Diagnosis can be made by examining potential proglottids under a microscope.

Asymptomatic Infections

D. caninum infections are rarely associated with clinical signs in infected dogs and cats. Many infections remain asymptomatic. Symptoms depend on the degree of infection, as well as age, condition, and breed of host.

Itchiness & Scratching

Pruritus is caused when gravid segments pass through the anus of infected host. The irritation and itchiness is similar to pinworms. It may lead dogs to exhibit scooting behavior, where they drags their anus across carpets. Thus, anal rubbing and scratching may be a sign of tapeworm infection.

Diarrhea & Gut Disease

The worms aren’t very harmful in adult animals. However, there may be hemorrhaging at point of attachment, leading to intestinal inflammation and diarrhea. In some cases, gut disease manifests as upper abdominal pain, weight loss, reduced growth rate, weakness, malaise, gastrointestinal stasis, irritability, lack of appetite, shaggy coat, and general ill health. Infrequently, there’s intussusception or blockage of the intestine, emaciation, and seizures.

How to Treat Tapeworm Infections

Anthelmintics

Dipylidium infections are successfully treated with oral de-wormers (anthelmintics). The most common active ingredient is praziquantel, which resolves a tapeworm infection in around a week. It can be used to treat both animals and humans. After treatment, stool will contain intact tapeworms and strands of proglottids. Bayer Tapeworm Dog De-Wormer and Bayer Tapeworm Cat De-Wormer use praziquantel as the active ingredient.

Long-term Management

Tapeworm management involves a strict de-worming schedule for current infections, along with a persistent flea control program to prevent future infections. After successful anthelmintic treatment, pets can be re-infected at any time by ingesting an infected flea. D. caninum eggs remain viable in the environment for weeks or months, available for flea larvae to consume. Thus, flea control ties into tapeworm control. For example, one study observed that Seresto flea collars were 96.6 % effective in preventing D. caninum infections in the dogs.

References