Fish Tapeworm By Samantha Bizuns

Fish Tapeworm

(Diphyllobothrium latum )

https://mcdinternational.org/trainings/malaria/english/dpdx5/html/Frames/A-F/Diphyllobothriasis/body_Diphyllobothriasis_mic1

Key Points

Acquired by the consumption of under or uncooked infected fish
Multicellular endoparasites
Diphyllobothriasis is often asymptomatic

Classification

Fish tape worms, scientifically known as Diphyllobothrium latum , are multicellular animal parasites. They are considered to be endoparasites, as most of their life cycle takes place within another organism. They are Helminthes, belonging to the Platyhelminthes phylum.

Biology and Mode of Transmission

https://www.cdc.gov/parasites/diphyllobothrium/biology.html

Unembryonatred eggs are released in the definitive hosts feces. In water the eggs are able to develop an embryo. Coracidia are then born from the eggs. Crustaceans act as the first intermediate host and ingest the coracidia. The first stage of larvae develop within the crustaceans. The crustacean is then ingested by the second intermediate host. Typically the second intermediate host is a fish. In the second intermediate host, procercoid larvae are able to develop into plerocercoid larvae. Larger fish may become paratenic hosts, but are not required in the life cycle. Plerocercoid invade the tissues of intermediate host. Definitive hosts are organisms that then consume the improperly cooked infected intermediate or paretenic host. The fish tape worm infection, called Diphyllobothriasis, can occur in both humans and fish eating animals. Diphyllobothrium latum resides in the small intestine of the definitive host where it reaches sexual maturity. Eggs are released in host feces and the life cycle repeats.

https://www.researchgate.net/figure/Diphyllobothrium-latum_fig12_233727096

Site of Infection, Pathology and Disease Symptoms

Diphyllobothriasis, in humans, occurs only in the small intestine. It is generally asymptomatic and only discovered in the incidence that the host notices eggs of tapeworm segments in their stool. Symptoms occur in less than 22% of infections and may include:

abdominal cramps
nausea
loose bowel movement
A deficiency of vitamin B12 causing anemia

Treatment

Drugs for multicellular endoparasites include:

Mebendazole which blocks cytoskeleton formation and inhibits glucose uptake; working together to deter the worms mobility
Ivermectin paralyzes intestinal worms

Most often prescribed drugs include praziquantel, which causes muscles spasms effecting the worms ability to attach to the intestinal wall, and niclosamide which kills the worm. Peristalsis then forces the worm to exit the host.

In some cases surgical intervention may be required to remove tapeworm.

Prevention

Physical methods of microbial control must be used; including Heat and Low Temperatures

When cooked, Fish should reach an internal temperature of at least 145° F
Flash freezing is an effective technique used for killing multi-cellular parasites
Fish being stored should be kept frozen at a temperature below 14°F

Victoria Roberts
https://www.nytimes.com/2015/05/19/science/freezing-fish-killing-parasites.html

Other methods of preventing Diphyllobothriasis

Research food handling practices in developing countries you intend to visit and take the necessary precautions before consuming food there
Ensuring proper disposal of human waste and adequate water treatment (this can not eliminate the risk of diphyllobothriasis completely as other fish eating mammals and birds can be definitive hosts)

Anatomy of a Tapeworm

Can be 2-10 meters long!

The Scolex

The “head”
Usually contain hooks and suckers which allow for attachment to intestinal wall ( Diphyllobothrium latum is an exception)
Different tapeworms can be identified by the shape of the scolex