Helminth| helminth classification|Clinical features|Medical World

What is Helminths?

It is a large macroparasites, it can be seen with the necked eye. it is also known as the Parasite worm.Many intestinal worms that are soil-transmitted and infect the gastrointestinal tract.

Helminth classification

There are consists of the following terms-

Nematodes

Introduction

There are >60 species of nematodes or roundworms that infect humans.they are comments human parasites and are estimated to infect 3-4 billion people worldwide. Helminth infections are a major public health burden in the developing world. All nematodes are elongated, cylindrical, non-segmental organisms, with a smooth cuticle and body-cavity containing a digestive tract and reproductive organs.

Types of Nematodes

Intestinal nematodes

Intestinal nematodes are the largest group of human helminths. The commonest intestinal nematodes cannot reproduce in human and are referred to as geohelminths, as their eggs have to develop in the soil. The exceptions are S.stercoralis and E. Vermicularis , which can be transmitted from person to person.

Tissue nematodes

The tissue-dwelling roundworms are also a major public health problem. particularly in the topics. Some affect human only, while others have an animal reservoir. All of the parasites have a complex life cycle involving intermediate hosts, except Trichinella spp. Adult worms do not multiply in humans, so the warm load and severity of disease depend on intensity of exposure.

Ascaris lumbricoides

Ascariasis is the commonest helminths infection of humans, with an estimated prevalence of >1 billion. It is caused by A. Lumbricoides and is found worldwide, most commonly in the tropics.

The parasites

The adults warms live in the small intestine and have a lifespan of 10-24 months. Each female produces up to 200,000 ova/day. Which pass out in the faeces. When ingested, the eggs hatch in the small intestine, penetrate the intestine wall, migrate through the venous system to the lungs where they break into the alveoli, migrate up the bronchial tree, before they are swallowed and develop into mature worms in the intestine.

Epidemiology

Ascaris infection is commonest in young children but can occur at any age. Transmission is by the face-oral route and is enhanced by the high output of ova and their ability to survive unfavourable environmental conditions. In endemic areas, most people have light to moderate worm burdens.

Clinical features

Clinical features depend on the site and intensity of infection.

• GI manifestation include malnutrition, malabsorption, steatorrhea
• Biliary obstruction may cause abdominal pain, cholangitis, pancreatitis
• Ectopic infections occur rarely, e.g. umbilical or hernial fistula, Fallopian tubes, bladder, lungs, and heart.

Treatment

• Albendazole are the treatment of choice
• Alternative agents include ivermectin, nitazoxanide, piperazine citrate
• Endoscopic or surgical intervention may be required for biliary/intestinal obstruction

Trichuris trichiura

Introduction

Trichuriasis is one of the most prevalent helminthic infections—it is estimated that one-quarter of the world's population carries the parasite. Infection is mainly asymptomatic, but heavy infection may cause anaemia, bloody diarrhoea, growth retardation or rectal prolapse.

The parasite

T.trichiura principally infects humans, residing in the caecum and ascending colon. The mean lifespan of adult worms is 1 year, and each female worm produces 5-20,000 eggs per day. After execration, embryonic development occur over 2-4 weeks. The embryonate egg is ingested, and the larva escapes its shell, penetrating the small intestinal mucosa, before migrating down into the caecum or colon.

Epidemiology

T. Trichiura has a worldwide distribution but is commoner in most tropical environments. Infection results from ingestion of embryonate eggs by direct contamination of hands, food, or drink, or indirectly through flies or other insects.

Clinical features

• Iron deficiency anaemia
• Rectal prolapse
• Acute GI symptoms- diarrhoea
• Chronic colitis with growth retardation

Treatment

Albendazole or mebendazole are the treatment of choice.

Ancylostoma duodenale and Necato americanus

Human hookworm infection is estimated to affect 740 million people worldwide. It is caused by two species A.duodenale and N.americanus.

The parasite

Adult hookworms are small, cylindrical , and greyish-white in colour. They live in the upper small intestine, attached to the mucosa. Adult worms produce about 7000 eggs per day. They pass out in the stool and hatch into larvae. Skin penetration requires contact with contaminated soil. The larvae are carried in the venous circulation to the lungs where they migrate up the respiratory tree to be swallowed and carried to the small intestine.

Epidemiology

The prevalence of hookworm infection is highest in sub-Saharan Africa, Asia, Latin America, and the Caribbean. Transmission requires human faecal contamination of the soil, favourable conditions of larvae and contact of human skin with contaminated soil.

Clinical features

• Skin rash—— patients may present early in the disease with 'ground itch' intense pruritus, erythema, and a popular/vesicular rash at the site of larval penetration.
• Pulmonary manifestation
• Acute GI symptoms— nausea, vomiting, diarrhoea and abdominal pain.

Treatment

• Albendazole or mebendazole are treatment
• Iron replacement therapy for iron deficiency anaemia.

Enterobius Vermicularis

Infection with E. vermicularis is highly prevalent in both temperature are and tropical climates. Pinworms infection is commonest in children and institutionalised populations.

The parasite

E. Vermicularis is a small, white, thread-like worm inhabits the caecum and ascending colon of humans. Female worms contain about 11,000 ova and live for 11-35 days. The gravid females migrate at night to the perianal region where they deposit their eggs.

Epidemiology

The prevalence of pinworm is highest in children aged 5-10years. Pinworm is primarily a family or institutional infection, with no particular socio-economic associations. As the lifespan of the worm is relatively brief, and eggs can only survive out of the body for 20 days, long-standing infections must be due to continuous reinfection.

Clinical features

• Most infected patients are asymptomatic
• Perianal /perineal pruritus and disturbed sleep are the commonest symptoms

Treatment

Albendazole or mebandazole are the treatment of choice