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Helminth Infestation/infection and Treatment
 

Helminth Infestation/Infection and treatment

Introduction

Definitions:
Helminth is the medical/scientific term to describe a parasitic worm that infests the human body.
Helminthiasis is the term employed to describe all infections caused by helminths.
Anthelminthic is defined in Dorland's Medical Dictionary as "An agent destructive to worms".

Man is the definitive host for helminths, with a large number of the people on earth harbouring worms of one species or another. It has been stated that helminths affect more than one quarter of the world's population, contributing significantly to socioeconomic problems in developing countries. In most cases these infections do not result in ill health, causing nothing more than mild discomfort. On the other hand, there are some worms (such as schistomiasis [bilharzia] and hookworm disease) that can cause serious morbidity.

In tropical, or subtropical regions, almost all the indigenous population is infected with hookworms and/or other helminths, and the problem of helminthiasis is of significance medical importance.

Transmission of helminths can occur via several mechanisms, but in the case of the soil-associated NEMETODES (classifications to be discussed later) it occurs via faecal-oral transmission or percutaneous infection by infective larvae. The climatic conditions favouring transmission are warmth and humidity. Most worms reproduce sexually within the human host, producing eggs or larvae that pass out of the body and infect the secondary (intermediate) host.

Classification

There are two clinically important types of worm infections:
* where the worm lives in the host's alimentary canal
* where the worm lives in other tissues in the host

The main examples of worms include:

In the Alimentary canal
In other tissues
Tapeworms (cestodes)
Taenia saginata      the usual hosts are
Taenia solium         cattle and pigs
Hymenolepis nana - human/rodent hosts
Diphyllobothrium latum - crustacean/fish host

Intestinal roundworms (nemetodes)
Ascaris lumbricoides (common roundworm)
Enterobius vermicularis (threadworm)
Trichuris trichuria (whipworm)
Strongyloides stercoralis (threadworm)
Necator americanus (hookworm)
Ankylostoma duodenale (hookworm)

Tremetodes (flukes)
Schistosoma haematobium
Schistosoma Mansoni            cause bilharzia
Schistosoma Japonicum

Tissue roundworms
Trichinella spiralis
Dracunculus medinensis
Filariae species

Hydatid tapeworm (cestode)
Echinococcus species

It is estimated that 1 billion people harbour Ascaris lumbricoides, while at least 800 million have hookworm disease.









Some nemetodes that usually live in the GI tract of some animals may infect humans and penetrate tissues. A skin infection, termed "creeping eruption" or "cutaneous larvae migrans", is caused by the larvae of dog (toxicara canis) and cat (toxicara cati) hookworms.

Helminth Infections

Helminth infections may be due to one worm type, or several (mixed infection).

Condition
Helminth
Enterobiasis

Ascariasis

Trichuriasis

Hookworm

Strongyloidiasis

Visceral larvae migrans

Trichinosis
Enterobiasis vermicularis (pruritis ani)

Ascaris lumbricoides (most common worm)

Trichuris trichiura (stunted growth)

Ankylostoma duodenale (iron supplements)
Necator americanus (iron supplements)
Strongylus species (in older children/adults)

Toxicariasis (hepatomegaly/anaemia)

Trichinella spiralis


Symptoms of helminth infection

As stated previously, infection with worms is usually only accompanied by minor symptoms; however, there is also some evidence of subtle effects of parasitism on cognitive function and nutrition. A curious finding from some research, is that helminth infection is paradoxically associated with a reduced incidence of atopy (the genetic predisposition to develop hypersensitive reactions).

The following are general symptoms that have been reported:

Common Symptoms
Serious Symptoms
Abdominal distension
Abdominal pain
Diarrhoea (+bleeding)
Itching
Impaired (stunted) growth
Impaired intellectual function
Iron-deficiency anaemia


Treatment of helminth infections

There is ongoing research to come up with a vaccine against worm infections. Otherwise, treatment is generally aimed at eradicating the parasite from the host's system. To be an effective anthelminthic, a drug must be able to penetrate the cuticle of the worm or gain access to its alimentary tract. Anthelminthics therefore, work in the following ways:
* causing paralysis of the worm
* damaging its cuticle

Combantrin (pyrantel pamoate) acts to eradicate worms by paralysing them, thereby preventing the worms from clinging to the inner lining of the gut. Combantrin is chemically different from other anthelminthics, in that it promotes high concentrations of acetylcholine at the neuro-muscular level of the worm. This neurotransmitter mediates in muscular relaxation by preventing the pro-contractile neurotransmitter adrenaline (epinephrine) from entering the smooth muscle cells. Without the ability to cling to tissue, the worm is paralysed and is excreted.

THE FOLLOWING TABLE IS TO BE INSERTED AFTER THE GELUSIL RANGE OF PRODUCTS AT THE BACK OF THE GI SYSTEM

Combantrin Tablets/Suspension
(6's/45ml)
Composition (per 5ml/tablet)
250mg Pyrantel pamoate
Indications
Removal of intestinal worms (helminths)
Helminths ("Drug of Choice")
Roundworm
Ascaris lumbricoides
Threadworm
Enterobiius vermicularis
Trichostrongylus species
Hookworm
Ancylostoma duodenale
Necator americanus
Ternidens deminutus
Dosages
10mg/kg body weight - SINGLE ORAL DOSE
Adults: (~70kg) 750mg
Children:
1-4 years (10-15kg) - 2.5ml (125mg)
5-9 years (16-25kg) - 5ml (250mg)
10-12 years (26-40kg) - 10ml (500mg)
Side effects*
Minor and transient
Nausea/vomiting
Tenesmus
Anorexia
Diarrhoea
Abdominal pain/cramps
Precautions
Due to transient elevation in SGOT, use in patients with liver disease with caution
Benefits
Broad spectrum anthelminthic
Palatable oral suspension
Need for 2nd dose rare
Purging not necessary
* Combantrin has a low absorption into the circulation
Additional treatment recommendations:
* when one family member is infected, treat the whole family
treat prophylactically every 6 months, especially with children








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