CASES/YEAR
1,000 (US); 20,000,000 (Global)
OTHER NAMES
Fish tapeworm infection; Diphyllobothrium latum infection;
INCUBATION
3-6 weeks from ingestion to presence of eggs in stool; [CCDM]
INITIAL SYMPTOMS
Usually an asymptomatic infection of long duration; One species, Diphyllobothrium latum, has been linked to pernicious anemia, based on reports from Scandinavia; [Cecil, p. 2117]
PRECAUTIONS
"No direct person-to-person transmission." [CCDM, p. 603]
COMMENTS
Some patients develop vitamin B12 deficiency from this tapeworm infection. Some heavily infected patients experience diarrhea or obstruction of the bile duct or intestines. Besides humans, hosts include dogs, bears, other fish-eating mammals, and seagulls. Humans become infected after eating raw or undercooked, freshwater fish (trout, pike, turbot, perch, Pacific salmon, Atlantic salmon, whitefish). [CCDM, p. 602-3] Patients may vomit or pass segments of worm and may have mild abdominal pain and weight loss. 40% of patients have decreased B12 levels, and 2% have megaloblastic anemia with glossitis. [5MCC-2020] This tapeworm matures in 3-6 weeks. It may reach a length of 25 meters and survive more than 30 years. Patients with heavy or prolonged infections (lasting more than a couple of years) may develop vitamin B12 deficiency and megaloblastic anemia. Secondary peripheral neuropathy may also develop. Other hosts are seals, cats, bears, minks, foxes, and wolves. [PPID, p. 3465] Mild eosinophilia is not uncommon. In the small proportion of patients with megaloblastic anemia, thrombocytopenia and mild leukopenia may occur. [Guerrant, p. 843]
DIAGNOSTIC
Identification of eggs or segments in feces; Examination of several stool specimens may be necessary; [CCDM, p.603]
SCOPE
Endemic to Northern Hemisphere (Europe, former Soviet Union, North America, Asia) plus Uganda & Chile; [www.dpd.cdc.gov/dpdx/HTML/diphyllobothriasis.htm] Now rare in Scandinavia, but common in Russia, Japan & S. America; [Cecil, p. 2117]
SIGNS & SYMPTOMS
-
>fatigue, weakness
-
G abdominal pain
-
G diarrhea
-
G nausea, vomiting
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H anemia
-
H eosinophilia
-
H leukopenia
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H thrombocytopenia
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*bowel obstruction
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*peripheral neuropathy
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*weight loss
SOURCE
Animal Tissue, Eating Contaminated Food, Eating Infected or Toxin-Containing Fish
RESERVOIR
Cats, Dogs, Fish and Shellfish, Human, Wild Animals
RISK FACTORS
- Eat undercooked meat or fish
REFERENCES FOR CASES/YEAR
1. (US) Guesstimate: 1000
2. (Global) Highly endemic (>2% prevalence) lake and delta areas include Siberia, Scandinavian & Baltic countries, N. America, Japan, and Chile. [PPID, p. 3465] "This study has shown that several dozen cases have been reported each year in Finland and Sweden, that there have been numerous cases in the French or Italian speaking areas of subalpine lakes, and that sporadic cases only have been observed in Austria, Spain, Greece, Romania, Poland and Norway. Over 30 cases have been identified on the Swiss shores of Lake Maggiore since 1990, and 70 cases on the Swiss and French shores of Lake Leman between 1993 and 2002." [PMID 15208471] Estimated 20 million people infected; [Cecil, p. 2117]