Lancet Fluke in Dogs

Although infestation by the dicrocoelium dendriticum fluke is mainly seen in cattle and other grazing animals, it can infest both humans and dogs. This fluke has been found on continents throughout the world and tends to spread quickly within suitable environments. In mammalian hosts like grazing animals, humans, and dogs, the parasites move to the bile ducts, stretching them out of shape as well as potentially clogging them. This can lead to serious problems such as anemia or canine cholangiohepatitis, an inflammation of both the biliary system and the liver.

Dicrocoelium dendriticum, also known as the lancet fluke, is a parasitic flatworm with a complicated life cycle with multiple hosts that are known to infect bovines, canines, and humans.

Most cases of infestations by the lancet fluke are small and produce only minor symptoms. If large numbers of the flatworms are involved, bile ducts may be stretched out of shape, and chronic infestations may cause critical symptoms to develop, such as blood loss, anemia, and cirrhosis, if left untreated. A rare disorder known as canine cholangiohepatitis may also develop with critical infestations. Symptoms of this disease can include gastrointestinal distress such as:

• Vomiting
• Diarrhea
• Lethargy
• Fever

Dogs can acquire this parasite the same way that grazing animals do, by eating the grass that an infected ant is clinging to or by ingesting an infected ant incidentally when drinking water or eating other items that the ant is in or on. Although it is rare for an infested liver to cause an infection in an animal that eats it, it does happen on occasion. It is more common for eggs obtained through eating another animal’s liver to pass through the digestive tract unchanged.

The symptoms of the Dicrocoelium dendriticum fluke are very similar to the symptoms of other types of flukes, as well as other parasites and mild toxins. When you bring your pet into the veterinarian’s office, she will perform a thorough physical exam, checking for evidence of toxins or infections. If the infestation has become severe, the examining veterinarian may be able to detect an enlarged liver when palpating the abdomen. General tests will be done to detect if any toxins, parasites, or imbalances are present in the blood or urine, but dicrocoelium dendriticum does not generally reside in either the blood or urine, so is unlikely to be located by these tests. 

This liver fluke is generally first seen when the feces of the infected animal is examined, and eggs are found. Eggs in the feces may indicate an infestation, but they may also be present due to ingestion of a contaminated liver, even without further infiltrations. Testing the contents of the bile fluids or the fluids within the intestine tends to give a more accurate representation of the extent of the problem. The enzyme-linked immunosorbent assay (ELISA) method of testing for the Dicrocoelium dendriticum has recently been proven to be effective in detecting this flatworm.

Although it is a relatively rare disorder in canines, it is still relatively easy to treat successfully. Several anthelmintic medicines formulated for dogs have proven very effective against this particular parasite. Praziquantel is commonly used both in the treatment of tapeworms and of flukes due to its ability to paralyze the parasites, inhibiting their ability to hold on to any surface areas. This allows them to be excreted through the bile and the liver.

Triclabendazole and Albendazole are additional varieties of anthelmintic which uses paralyzation to eliminate flukes that invade the liver. Each of these medications is highly effective and come in both human and canine formulations. Most anthelmintic medications can cause fetal abnormalities and spontaneous abortion and should not be given to pregnant animals, although there are a few exceptions. The medications themselves are known to have side effects that can include lack of appetite, vomiting, and abdominal pain.

Infestations by dicrocoelium dendriticum in canines are exceedingly infrequent and rarely life-threatening as it takes massive populations of the flatworms or an extended period of infection for the parasite to damage the liver. Lancet flukes are much more likely to infect grazing animals than carnivores, and they often go unnoticed. The parasitic infection is sometimes uncovered at an incidental autopsy.  Unless there has been extensive damage to the liver, prognosis for this disease is good, but it is important to give your pet the anthelmintic medication for the full measure of time that it is prescribed by your dog’s doctor to prevent a reoccurrence of the infection.