DiphylobotriDiphylobotriozaoza

EpidemiologyEpidemiology

EpidemiologyEpidemiology

The fish tapeworm occurs worldwide (Europe, northern The fish tapeworm occurs worldwide (Europe, northern Siberia, North America, western Africa, South-East Asia, Siberia, North America, western Africa, South-East Asia, Japan, Australia)Japan, Australia)

Humans become infected by eating raw or undercooked Humans become infected by eating raw or undercooked fish (e.g. pike, perch, salmon)fish (e.g. pike, perch, salmon)

Besides humans, as an important final host, wild and Besides humans, as an important final host, wild and domestic carnivore animals serve as reservoir hostsdomestic carnivore animals serve as reservoir hosts

Life cycle of Diphyllobothrium latumLife cycle of Diphyllobothrium latum

Life cycle of Diphyllobothrium latumLife cycle of Diphyllobothrium latum

PathologyPathology

Pathology – provoked in Pathology – provoked in most cases by a single most cases by a single worm – is lightworm – is light

Hosts might be depleted of Hosts might be depleted of vitamin B12, resulting in vitamin B12, resulting in rare cases in a macrocytic rare cases in a macrocytic anaemia (especially in anaemia (especially in Scandinavia)Scandinavia)

  Scolex of Scolex of D. latumD. latum..

A. ScolexA. Scolex

Diphyllobothrium latum morphologyDiphyllobothrium latum morphology

The fish tapeworm of humans has a The fish tapeworm of humans has a world-wide distribution. Infected world-wide distribution. Infected

persons are usually asymptomatic persons are usually asymptomatic but may have diarrhea or but may have diarrhea or

abdominal pain. Prolonged abdominal pain. Prolonged infection results in vitamin B 12 infection results in vitamin B 12

deficiency.deficiency.

B. Proglottid.B. Proglottid.

C. Egg.C. Egg.

Section of an adult D. latum containing many proglottids.

Close-up of a few of the proglottids, showing the rosette-shaped uterus at the center of each proglottid.

Proglottids of Diphyllobothrium latum.  Proglottids of Diphyllobothrium latum.  These proglottids tend to be passed in strands of variable These proglottids tend to be passed in strands of variable length in the stool.  The proglottids tend to be broader than length in the stool.  The proglottids tend to be broader than long. long. 

Proglottids of Proglottids of Diphyllobothrium latum.  Diphyllobothrium latum.  The species characteristics The species characteristics are: the proglottid is are: the proglottid is broader than it is long; size 2 broader than it is long; size 2 to 4 mm long by 10 to 12 mm to 4 mm long by 10 to 12 mm wide; uterus coiled in rosette wide; uterus coiled in rosette appearance; genital pore at appearance; genital pore at the center of the proglottid.the center of the proglottid.

Carmine-stained proglottids of Carmine-stained proglottids of D. latumD. latum, showing the rosette-, showing the rosette-shaped ovaries.shaped ovaries.

The main body of the worm is virtually filled with male and The main body of the worm is virtually filled with male and female reproductive organs allowing it to produce an female reproductive organs allowing it to produce an incredible number of eggs, often more than 1,000,000 a day.incredible number of eggs, often more than 1,000,000 a day.

Diphyllobothrium latumDiphyllobothrium latum

in human intestine. in human intestine. 

It is the longest tapeworm invading humans with as many as It is the longest tapeworm invading humans with as many as 4,000 segments (proglottids).4,000 segments (proglottids).

The adult is ivory or grayish-yellow in color and can live in The adult is ivory or grayish-yellow in color and can live in humans for 20 years.humans for 20 years.

Some people are constantly hungry because the tapeworms Some people are constantly hungry because the tapeworms are eating most of the food. There are times when the worm are eating most of the food. There are times when the worm gets so large that it will cause a colon blockage. gets so large that it will cause a colon blockage.

In some people a severe anemia may develop, because of this In some people a severe anemia may develop, because of this tapeworm's ability to consume most of its host's vitamin B12.tapeworm's ability to consume most of its host's vitamin B12.

Diagnostic methodsDiagnostic methods

Parasitological Parasitological diagnosisdiagnosis

Patients often Patients often observe short observe short segments of the segments of the tapeworm (chain of tapeworm (chain of proglottids) in their proglottids) in their stools.stools.It is not difficult to It is not difficult to confirm diagnosis by confirm diagnosis by detecting the detecting the numerous eggs by numerous eggs by microscopy. microscopy.

TTreatmentreatment

The standard treatment for diphyllobothriasis, as well as many The standard treatment for diphyllobothriasis, as well as many other tapeworm infections is a single dose of Praziquantel, 5-other tapeworm infections is a single dose of Praziquantel, 5-10 mg/kg PO once for both adults and children. 10 mg/kg PO once for both adults and children. 

An alternative treatment is Niclosamide, 2 g PO once for An alternative treatment is Niclosamide, 2 g PO once for adults or 50 mg/kg PO once (8).  adults or 50 mg/kg PO once (8). 

Prevention and ControlPrevention and Control

Cestode larvae in fish are killed by heat or after freezingCestode larvae in fish are killed by heat or after freezing The control of transmission is difficult due to many reservoir The control of transmission is difficult due to many reservoir

hostshosts