Diphyllobothriasis: Causes, Symptoms, Diagnosis And Treatment

Diphyllobothriasis is an fish-borne parasitic caused by tapeworms (Diphyllobothrium latum) that can affect humans and other animals.

In this article, we will discuss the causes, symptoms, diagnosis, prevention and treatment for diphyllobothriasis.

Diphyollobothriasis — **Image: Diphyllobothriasis symptom (abdominal pain**).

Anisakiasis: Causes, Symptoms, Diagnosis & Treatment

History

Diphyllobothriasis is defined as a human intestinal infection with the Cestode parasite Diphyllobothrium latum, Diphyllobothrium nihonkaiensese, and other broad tapeworm species. It is the largest parasite of fish in the intestine.

It is a most common zoonotic disease as well as a food-borne disease. The parasite has a long recorded history of infecting people. In the 1970s, the most common case of Diphyllobothriasis came from Europe (5 million), then Asia (4 million), and a few cases came from North America, South America, and Africa. No reliability came from Australia.

Geographical Distribution of Diphyllpbothrium latum

Diphyllobothrium latum is found in Palearctic and Nearctic areas: in the Freshwater lakes and streams of North America and the Great lakes, as well as the Mediterranean and Baltic seas, South America, Asia, Europe, and Central Africa including Italy, France, Switzerland, Finland, Ireland, Israel, Siberia, Japan, Chile, Canada.

Habitat

Diphyllobothrium latum is found in and around freshwater lakes, rivers, and streams. They pass different stages in different habitats. The eggs inhabit fecal matter in a definitive host, the larvae live first in a copepod and then in the flesh of fish, and adults live in mammalian intestines.

Species Used as Host

Copepoda
Teleostei
Mammalia

Fish Species Affected by Diphyllobothrium latum

Salmon, Trout, Perch, Walleyed pike, burbot, whitefish, shad, and other species-usually freshwater fish.
Diphyllobothrium latum not only affects fish and humans but also fish-eating carnivores, cats, mongoose, mink, foxes, bears, seals, and sea lions.

Location in Human Body:

Intestine.

Food Habit
Carnivorous. Feeds on body fluids of mammals. They deplete the Vit B-12 from the host body.
Life Span
30 years or more.

Epidemiology of Diphyllobothriasis

The people at high risk of being infected by Diphyllobothriasis who have traditionally and regularly consumed raw and undercooked fish. E.g.-
Sushi and sashimi in Japanese cuisine.
Marinated herring in Scandinavia.
Ceviche in Latin American Cuisine
Carpaccio di persico in Italian Cuisine
Tartare Maison in French-speaking populations.

Causes of Diphyllobothriasis Disease

–Diphyllobothriasis is caused by the fish tapeworm Diphyllobothrium, which is found in freshwater fish such as salmon, trout, and pike. The infection occurs when a person ingests raw or undercooked fish that contains the tapeworm’s infective larvae.

–In some cases, the infection can be acquired through consumption of raw or undercooked fish in sushi, ceviche, or other dishes popular in some cultures.

Another way of becoming infected is by consuming water from lakes, rivers, or streams that are contaminated with tapeworm larvae, this is not common but it’s possible, especially in areas where sanitation is poor.

What is Diphyllobothrium latum

Diphyllobothrium latum, more commonly known as the fish tapeworm, is a species of parasite that can infect humans.

The tapeworms are commonly found in parts of Europe, North America, and Asia where freshwater fish are consumed raw or undercooked.

The adult worm lives in the small intestine and attaches itself to the intestinal wall by its suckers and hooks.

It then begins to consume nutrients from food passing through the intestines while releasing eggs into feces that can contaminate water sources such as lakes and rivers if not disposed of properly.

If left untreated, the infection can cause deficiencies in vitamins B12 and folate which can lead to anemia.

This disease is mainly acquired through eating raw, undercooked, slightly salted, slightly smoked, and frozen fish. The main causative organisms are Diphyllobothrium latum and Diphyllobothrium nihonkaiense. But other Diphyllobothrium and similar species have also been reported as infecting agents such as-

Diphyllobothrium dendriticum
Diphyllobothrium pacificus
Diphyllobothrium balanopterae
Diphyllobothrium alascense
Diphyllobothrium cameroni
Diphyllobothrium latum (Dibothriocephalus latus)

Classification

Kingdom; Animalia
Phylum: Platyhelminthes
Class: Cestoda
Subclass: Eucestoda
Order: Pseudophyllidea
Family: Diphyllobothridae
Genus: Diphyllobothrium
Species: Diphyllobothrium latum

Morphology of Diphyllobothrium latum

The Diphyllobothrium latum body is dorsoventrally flattened.
The body is narrower than long.
Body color Grayish.
The length can reach up to 12 meters (3-12 m) and increases throughout its life.
Their body is divided into the head (Scolex), neck, and body (strobilia).
The scolex is finger-shaped and attaches to the neck.
In the head, two slit-like suckers with grooves are present but there are no hooks.
Narrow weakly-muscular grooves (bothria) run longitudinally along the body.
They have no oral opening, so they feed through absorption.
The strobila is composed of 3000-4000 segments which are called proglottids.
Mature segments are wider than they are long.
They are hermaphroditic and have both sex organs.
Strobilia contains proglottids, each proglottid contains testes and vitelline follicles.
The uterus is bilobed in a structure that loops and extends from the ovary to the uterine pore on the mid-ventral surface of the segment.
The mature proglottids release eggs through the uterine pore.
The eggs are oval-shaped, un-embryonated, and have a lid-like operculum and these eggs are continuously produced.
As they are Pseudophyllidean cestodes, the genital pores open midventrally.
They have no alimentary canal or body cavity.
The life cycle involves more than 1 intermediate host, mainly invertebrates but sometimes small vertebrates.

Life Cycle of Diphyllobothrium latum

The life cycle of Diphyllobothrium latum includes the following stages:

Egg: The tapeworm releases eggs into the host’s feces, which then enter freshwater or brackish environments.

Coracidium: The eggs hatch into a free-swimming larvae called a coracidium in freshwater or brackish environments.

Procercoid: The coracidium is then ingested by a copepod, a small aquatic crustacean. Inside the copepod, the larvae develops into a procercoid.

Plerocercoid: The procercoid is then ingested by a fish, where it develops into the plerocercoid stage.

The plerocercoid develops into the adult tapeworm in the small intestine.

Adult tapeworm: The adult tapeworm lives in the small intestine of the human host, where it attaches to the intestinal wall and absorbs nutrients. The tapeworm can grow up to 30 feet in length.

It’s important to note that the life cycle is not completed until the human host excretes eggs in feces and the cycle starts over again.

Adult worms have been reported as long as 10-30 ft long and 10-20 mm wide and composed of 3000-4000 proglottids.
The ovoid eggs do not completely form embryos when laid.
Eggs lay dormant in winter after passing out of the host, these eggs actively consume oxygen.
Within the shell, the embryo becomes fully developed in 8-12 days.
Typical of the Pseudophyllidea, the individual embryo is covered with a ciliated embryophore and is known as a coracidium.
Upon hatching, the coracidium may become free swimming or free crawling. Coracidium must be ingested by a specific copepod such as Diaptomas spp. Or Cyclops within 24 hours otherwise they perish.
Coracidium is quite host-specific.
Coracidia loses its ciliated coat and becomes a naked oncosphere upon successful entry into the appropriate copepod host.
The oncosphere bores through the copepod’s intestinal wall and ultimately lodges in the coelomic cavity.
Oncosphere has metamorphosed into solid elongated larvae called procercoid within 14-18 days.
The larva processes six hooks embedded into its cercomer, which projects from the posterior end.
When an infected copepod is ingested by a fish, the escaping procercoid in the piscine host’s intestine slowly works its way through the intestinal wall and eventually becomes situated in the body muscles where it develops into a long, solid plerocercoid of D. latum may measure 2-4 cm lengths.
The encystment of the plerocercoid is in the muscle of the body wall; encystment does not occur, however, if it should settle in or on the viscera a cyst is formed around the plerocercoid.
Eating plerocercoids in poorly cooked or raw fish causes infection in the definitive host such as humans, dogs, cats, etc.
Humans (or other mammals) ingest raw or undercooked infected fish. Plerocercoid larvae are not digested, but instead remain in the small intestine of their new host and grow to adulthood. Proglottids release immature eggs, completing the life cycle

Diphyllobothriasis Signs & Symptoms

The signs and symptoms of diphyllobothriasis, an infection caused by the fish tapeworm Diphyllobothrium, can vary depending on the number of worms present and the duration of the infection.

Some common symptoms include:

Abdominal pain and discomfort
Diarrhea
Nausea and vomiting
Weight loss
Anemia (due to vitamin B12 deficiency)
Fatigue
Weakness
Abdominal distension
Loss of appetite
In some cases, patients may also have visible segments of the tapeworm, called proglottids, in their stool or around their anus.

It’s important to note that many people with this parasite may have no symptoms at all. And some symptoms can be mistaken for other illnesses, making it hard to diagnose.

Abdominal pain
Vomiting
Nausea
Anorexia
Diarrhea
Weight loss
Eosinophilia
Vitamin B12 deficiency (Parasite absorbs 80% of host’s Vit B12)
Skin tingling and numbness.
Headache
Megaloblastic anemia.
Paresthesia
Allergy
Fatigue
Constipation and
Discomfort.
Obstruction of the bowel

Diphyllobothriasis Diagnosis

Clinical examination: Symptoms such as abdominal pain, diarrhea, and weight loss may suggest the presence of a tapeworm infection.

Stool analysis: A sample of the patient’s stool can be examined for the presence of tapeworm eggs or segments of the worm.

The definitive diagnosis is based on the detection of the eggs or proglottids in the feces, so a stool analysis is essential to confirm the presence of the parasite.

Blood tests: Elevated levels of vitamin B12 in the blood may indicate an infection with Diphyllobothrium.

Imaging studies: X-rays or a CT scan of the abdomen may reveal the presence of a tapeworm in the intestine.

Endoscopy: A thin tube with a camera on the end can be inserted into the intestine to directly visualize the tapeworm.

Diagnosis of Diphyllobothrium latum

The diagnosis of Diphyllobothrium species as well as the detection of their sources for human infection (through anamnestic data) are of great importance concerning epidemiology. The diagnosis is-

Proglottid identification: identified by proglottid segments.
Stool Examination: Identified by characteristics of eggs in feces. It is the most relevant, accurate and easiest method of diagnosis.
Epidemiological study: RFLP (Restrictions Fragment Length Polymorphism) can be effectively used.
PCR: By using it, purified eggs are identified.
CBC :Complete Blood Count. Eosinophilia present.
Mean Cell Volume: May be above or at the higher end of the reference range.
Hemoglobin level and hematocrit: Hemoglobin level is below or at the lower end of the reference range. Diphyllobothriasis causes anemia which is typically associated with increased free hydrochloric acid in gastric juice, in contrast to the relative achlorhydria invariably observed in true pernicious anemia.
Peripheral smear
Vitamin B-12 level
Folate level

Diagnosis Methods In Human

Finding eggs in feces or duodenal content.
Percutaneous trans-hepatic cholangiography
Abdominal X-ray
Magnetic Resonance Imaging (MRI)
An Enzyme-linked Immunosorbent Assay (ELISA)
Immunoblot
Ribosomal DNA (rDNA) sequencing.

Prevention and Control of Diphyllobothrium latum

Prevention of Diphyllobothrium latum includes-
To avoid infection, ponds to be stocked with new fish, particularly fry or juveniles should be disinfected.
The pond should be drained. After 2-3 days of drying, the bottom should be treated with Quicklime at 2 kg/ha.
If the pond drying is not possible, disinfect the pond with Quicklime at 2.5 tons/ha. Another method of disinfection is to apply Methylene blue to the pond at 1g/10 m3.
Break the life cycle of the parasite.
Prevent water contamination.
Treatment of people harboring the parasite.
Prevent transmission of infective larvae from fish to humans.
Prevent the eggs from reaching water by providing adequate latrines combined with health education.
Avoid eating raw or undercooked fish.
The fish should be cooked properly at a temperature of ≥63°C [≥ 145° F].
The fish should be refrigerated at recommended temperature to kill the tapeworms. The recommended temperatures include the-
Refrigerate at -20° C [-4°F] or below for 7 days.
Refrigerate at -35°C [-31°F] or below for 15 hours.
Refrigerate at -35°C [-31°F] or below until become solid and stow at-20° C [-4°F] or below for 24 hours.

Treatment of Diphyllobothrium latum
A single dose of Praziquantel (5-10 mg/kg)
[N.B.: Side Effects of Praziquantel-weakness, headache, dizziness, abdominal pain, fever, and urticaria]
Niclosamide bithionol as Yomesan 1g in the morning and 1g after an hour for adults. And 50 mg in a single dose for children.
Bithionol (50-60 mg/kg body weight in a single dose)

Economic Importance

Diphyllobothrium latum is not beneficial at all. Rather it is very harmful to humans. It causes anemia and Vit B-12 deficiency. In this case, Vit B-12 supplement should be used for treatment and the worm should be eradicated medically by taking a drug named Praziquantel.

How To Avoid Diphyllobothrium latum Infection | Diphyllobothriasis Prevention

In addition to taking medication, it is important to practice good hygiene and sanitation to prevent reinfection.

Here are some preventive measures to help avoid Diphyllobothrium latum infection:

Cook fish thoroughly: Make sure to cook fish to an internal temperature of at least 145°F to kill any tapeworm larvae that may be present.

Avoid raw or undercooked fish: Especially from lakes, rivers, or other bodies of freshwater.

Wash hands thoroughly: Before eating and after handling raw fish or meat.

Practice good hygiene and sanitation: This includes washing hands frequently, keeping food preparation areas clean, and avoiding cross-contamination of raw and cooked foods.

Be cautious while traveling: Be careful while consuming raw or undercooked fish while traveling to areas where the infection is common.

Be selective: Be selective about the fish you eat, and avoid consuming fish that are known to be carriers of Diphyllobothrium latum, such as salmon and pike.

Seek medical attention: If you develop symptoms of tapeworm infection, such as abdominal pain, diarrhea, or malnutrition, seek medical attention immediately.

It’s important to note that these preventive measures are not guaranteed to protect you from infection, but they can significantly reduce the risk of infection.

Diphyllobothriasis Treatment

The treatment involves the use of one of the following medications:

Niclosamide: This medication is highly effective in killing the adult tapeworm and can be taken as a tablet or capsule.

Praziquantel: This medication is also highly effective in killing the adult tapeworm and can be taken as a tablet or capsule.

These medications are highly effective in killing the adult tapeworm, and can be taken as a tablet or capsule.

It’s important to note that these are prescription medications and should be taken under the supervision of a healthcare professional.

These medications are prescription drugs and are not recommended to be taken without a medical prescription.

Prevention and Control of Diphyllobothrium latum

Prevention of Diphyllobothrium latum includes-
To avoid infection, ponds to be stocked with new fish, particularly fry or juveniles should be disinfected.
The pond should be drained. After 2-3 days of drying, the bottom should be treated with Quicklime at 2 kg/ha.
If the pond drying is not possible, disinfect the pond with Quicklime at 2.5 tons/ha. Another method of disinfection is to apply Methylene blue to the pond at 1g/10 m3.
Break the life cycle of the parasite.
Prevent water contamination.
Treatment of people harboring the parasite.
Prevent transmission of infective larvae from fish to humans.
Prevent the eggs from reaching water by providing adequate latrines combined with health education.
Avoid eating raw or undercooked fish.
The fish should be cooked properly at a temperature of ≥63°C [≥ 145° F].
The fish should be refrigerated at recommended temperature to kill the tapeworms. The recommended temperatures include the-
Refrigerate at -20° C [-4°F] or below for 7 days.
Refrigerate at -35°C [-31°F] or below for 15 hours.
Refrigerate at -35°C [-31°F] or below until become solid and stow at-20° C [-4°F] or below for 24 hours.

Treatment of Diphyllobothrium latum

A single dose of Praziquantel (5-10 mg/kg)
[N.B.: Side Effects of Praziquantel-weakness, headache, dizziness, abdominal pain, fever, and urticaria]
Niclosamide bithionol as Yomesan 1g in the morning and 1g after an hour for adults. And 50 mg in a single dose for children.
Bithionol (50-60 mg/kg body weight in a single dose)

Economic Importance

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