Title : Helminths & Worm

 

 

 

 

 

                Helminths

Definition: Parasitic worms, also known as helminths, are large macro parasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as schistosomes reside in blood vessels.

 

Classification of Helminths: Helminths are large, multicellular organisms that are visible to the eye once in the adult stage of their life cycle. Helminths and multicellular eukaryotes, can either be free-living or parasitic.

In their adult form, helminths are unable to multiply in humans and utilize numerous mechanisms of transmission to ensure reproductive success. These parasites live in and feed on hosts which allow them to obtain nourishment while disrupting the hosts’ nutrient absorption. Parasitic worms are commonly found within the intestine and thus, are called intestinal parasites. They are able to live in both humans and animals.

The major groups of parasitic helminths include:

•           Platyhelminthes (flatworms)

•           acanthocephalans (thorny-headed worms)

•           cestode (tapeworms)

•           trematodes (flukes)

•           nematodes (roundworms).

The classification and identification of helminths are dependent on numerous factors including body shape, body cavity, body covering, digestive tubing, sex and type of attachment organs.

 

Difference between cestode, trematode and nematode:

Common helminths in Bangladesh

These soil-transmitted helminths (hookworms, roundworms, whipworms) are transmitted through the fecal-oral route as a result of poor sanitary practices. The most common infections that can affect travellers are Ascariasis, Hookworm, and Trichuriasis which are Neglected Tropical Diseases (NTDs).

 

                 Tape Worm

Definition: A worm that is flat like a tape measure and functions as an intestinal parasite, unable to live freely on its own but able to live within an animal's gut.

 

 

Clinically importance : Tapeworms (Cestoda) continue to be an important cause of morbidity in humans worldwide. Diphyllobothriosis, a human disease caused by tapeworms of the genus Diphyllobothrium, is the most important fish-borne zoonosis caused by a cestode parasite. Up to 20 million humans are estimated to be infected worldwide.

Morphology: Tapeworms are bilaterally symmetrical (i.e., the right and left sides are similar). Some consist of one long segment; others have a definite head, followed by a series of identical segments called proglottids. The head, or Scolex, bears suckers and often hooks, which are used for attachment to the host.

Properties: The Skin. tough outer covering that. protects against host's digestive juices. ...Heterotrophic. live on other living things in which they depend on for food. ...Sessile. cannot move on their own. ...Body Segments. Scolex (head) has several suckers.

Life circle: All tapeworms (cestode) cycle through 3 stages—eggs, larvae, and adults. Adults inhabit the intestines of definitive hosts, mammalian carnivores. Several of the adult tapeworms that infect humans are named after their main intermediate host: The fish tapeworms (members of the family Diphyllobothriidae).

Mode of transmission: Tapeworm infection is caused by ingesting food or water contaminated with tapeworm eggs or larvae. If you ingest certain tapeworm eggs, they can migrate outside your intestines and form larval cysts in body tissues and organs (invasive infection).

Diseases production: Human taeniasis is a parasitic infection caused by three tapeworm species, T. saginata (known as the beef tapeworm), T. solium (pork tapeworm), and T. asiatica (the Asian tapeworm). Humans are the only hosts for these Taenia tapeworms.

Laboratory diagnosis: A doctor diagnoses intestinal tapeworm infection by finding worm segments or eggs in a stool sample. In people with cysticercosis, cysts in the brain or other tissues can be seen using computed tomography (CT) or magnetic resonance imaging (MRI). Blood tests for antibodies to the pork tapeworm may also be helpful.

 

 

                                     Pin Worm

Definition:  A small nematode worm,Enterobius vermicularis, infesting the intestine and migrating to the rectum and anus, especially in children.

  

 

 

Clinically importance : The pinworm is the most common helminth parasite of temperate regions. These infections are found worldwide and affect all socioeconomic groups. Less attention is paid to the pinworm in tropical regions, presumably because of the prevalence of more important parasites.

Morphology: The female worm measures 8 to 13 mm long and has a pointed tail (hence the common name "pinworm"). The male worm is inconspicuous, about 2～5 mm long. The eggs are oval, compressed laterally, and flattened on one side and measure 50 to 60 ㎛ long by 20 to 30 ㎛ wide.

Properties: Pinworms are thin and white, measuring about 1/4 to 1/2 inch (about 6 to 13 millimeters) in length. While the infected person sleeps, female pinworms lay thousands of eggs in the folds of skin surrounding the anus.

Life cycle: The entire life cycle, from egg to adult, takes place in the human gastrointestinal tract of a single host, from about 2–4 weeks or about 4–8 weeks. The life cycle begins with eggs being ingested. The eggs hatch in the duodenum (i.e., first part of the small intestine).

Mode of transmission: Pinworm infection is spread by the fecal-oral route, that is by the transfer of infective pinworm eggs from the anus to someone's mouth, either directly by hand or indirectly through contaminated clothing, bedding, food, or other articles.

Diseases production: Pinworm infection, also known asenterobiasis, is a human parasitic disease caused by the pinworm. The most common symptom is itching in the anal area. This can make sleeping difficult. The period of time from swallowing eggs to the appearance of new eggs around the anus is 4 to 8 weeks.

Labrotory diagnosis: The most common means of diagnosing pinworm infection is via the “Scotch tape” test, where a clear adhesive cellulose tape is applied to the anal area early in the morning before bathing or defecation. This is then observed under a microscope for the presence of pinworm eggs.

 

 

                              Hook worm

Definition: Hookworms are intestinal, blood-feeding, parasitic roundworms that cause types of infection known as helminthiases.

 

 

Clinically importance:. The public health significance of hookworm disease is briefly reviewed. The latest evidence confirms that blood loss caused by the worms' feeding activity in the gut is a contributing factor in the development of poor iron status leading to iron-deficiency anaemia.

Morphology: The adults are cylindrical with a head bent sharply backwards giving them a hooked appearance. The average adult hookworm usually measure about 5-10 ㎜ in length by 0.2 to 0.5 ㎜ in width. The hookworm species are mainly differentiated by their buccal capsule and the arrangement of rays in the bursa.

Properties: The worm is pinkish-white. Adult male hookworms range in size from 8-11 mm long, whereas adult females range in size from 10-13 mm long. This species is dimorphic, with the males having bursa characteristics and needle-like spicules with small tips, which are distally fused.

Life cycle: Eggs are passed in the stool , and under favourable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. The released habit-forming larvae grow in the faces and/or the soil , and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective .

 

Mode of transmission: The larvae mature into a form that can penetrate the skin of humans.Hookworm infection is transmitted primarily by walking barefoot on contaminated soil. One kind of hookworm (Ancylostoma duodenal)can also be transmitted through the ingestion of larvae.

 

 

Diseases production: Human hookworm disease is a common helminth infection that is predominantly caused by the nematode parasites Necator Americanos and Ancylostomaduodenale; organisms that play a lesser role include Ancylostoma ceylonicum, Ancylostoma Brazilians, and Ancylostoma caninum.

 

 

Labrotory diagnosis:

The standard method for diagnosing the presence of hookworm is by identifying hookworm eggs in a stool sample using a microscope. Because eggs may be difficult to find in light infections, a concentration procedure is recommended.

 

 

Virulence Factor

While the larvae are able to penetrate skin they still need at least 5 minutes to fully penetrate into the host. The hookworm is able to survive the brief amount of time it takes for it to travel to the small intestine. A. duodenale can also infect by means of ingestion.

 

 

 

 

 

 

 

 

 

                            Round Worm

 

Definition:  A type of parasitic worm that hatches in the intestines and lives there. The eggs of the roundworm usually enter the body through contaminated water or food or on fingers placed in the mouth after the hands have touched a contaminated object.

 

 

Clinically importance: Among these diseases, ascariasis (round worm infection) is a chronic and potent fatal parasitic disease, caused principally by Ascaris lubricities. The disease is important with enormous health and social implications for school going children in many developing countries of Africa, Asia, and Latin America.

 

 

Morphology: Ascaris lubricities is characterized by its great size. Males are 2–4 mm (0.08–0.2 in) in diameter and 15–31 cm (5.9–12 in) long. The male's posterior end is curved ventrally and has a bluntly pointed tail. Females are 3–6 mm (0.1–0.2 in) wide and 20–49 cm (7.9–19 in) long.

 

Properties:

the roundworms have a body cavity with internal organs. A roundworm has a complete digestive system, which includes both a mouth and an anus. ... Roundworms also have a simple nervous system with a primitive brain.

 

Life cycle: Worm eggs that have passed from the sheep in dung hatch and develop through first (L1) and second (L2) larval stages to become infective larvae (L3). The success and speed of this development depends on weather conditions, specifically warmth and moisture, and require a minimum of 4 days and rarely more than 10 days.

 

 

 

 

 

Mode of transmission: Transmission occurs when eggs are swallowed from soil contaminated with human faeces or consumed with produce contaminated with soil containing infective eggs. Transmission does not occur from direct person-to-person contact or from fresh faeces.

 

Diseases production: Ascariasis is a disease caused by the parasitic roundworm Ascaris lumbricoides. Infections have no symptoms in more than 85% of cases, especially if the number of worms is small. Symptoms increase with the number of worms present and may include shortness of breath and fever in the beginning of the disease.

 

Laboratory diagnosis: Health care providers diagnose roundworms by taking a thorough clinical history, looking at the symptoms, and then taking special blood test sand/ or looking at the swabbed eggs under a microscope.

 

   ( Ref by Google)

 

           The End

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