MESOCESTOIDES SPECIES: CANINE PERITONEAL LARVAL CESTODIASIS
Although Mesocestoides species were first described in 1863, we still do not know the complete life history of these parasites. Species of Mesocestoides occur worldwide. Mature tapeworms live in the small intestine of a variety of birds and mammals, including domestic dogs
and cats (Table 1). It appears that some type of coprophagous invertebrate is the most likely first intermediate host. The typical metacestode
stage, the tetrathyridium, occurs within the second intermediate host, which includes amphibians, reptiles, birds, and mammals.
These tetrathyridia tend to localize within the peritoneal cavity, lungs, and liver. When eaten by the definitive host, they
mature in 16 to 21 days. Certain strains of the parasite can asexually reproduce within the intestinal tract of the definitive
host as well as within the tissues of the intermediate host. One study showed that ingestion of 500 tetrathyridia could result
in as many as 17,000 mature tapeworms in the dog.
Intestinal infections in the definitive host are not usually associated with clinical signs. However, dogs and cats can also
serve as second intermediate hosts, and infection in dogs can lead to a condition called canine peritoneal larval cestodiasis (CPLC). Clinical signs of CPLC range from none to abdominal enlargement, ascites, anorexia, vomiting, and peritonitis. Ascites
is the most common presenting sign, followed by anorexia and weight loss. CPLC is an incidental finding in approximately one-fourth
of all cases.10-12
CPCL is a life-threatening disease with a guarded prognosis. The most significant factors influencing survival are the severity
of clinical signs at the time of diagnosis and application of an aggressive treatment strategy after diagnosis. The most effective
approach appears to be a combination of surgery and anthelmintic treatment. Regardless of the treatment approach, the prognosis
is guarded, especially for dogs presenting with rapidly developing signs or severe disease.10
Peritoneal lavage or surgical removal of cysts is recommended before the initiation of anthelmintic therapy, especially in
cases where large volumes of fluid and parasites are present. The current suggested anthelmintic treatment is fenbendazole
at 100 mg/kg orally, twice daily for 28 consecutive days.10 It may be necessary to re-treat animals if clinical disease reoccurs in the months or years following initial treatment.
Praziquantel (5 mg/kg) is used to treat mature, intestinal infections with good results.
Lora R. Ballweber, DVM, MS
Department of Microbiology, Immunology and Pathology
College of Veterinary Medicine & Biomedical Sciences
Colorado State University
Fort Collins, CO 80523-1644