CHAPTER ONE

INTRODUCTION

1.0     DEFINITION OF ENTERIC WORM

Enteric worm are define as organisms that live in the intestine of humans or animals and invest their food from the intestine to grow.  The most common of the parasitic-worms that infect the human intestine are viz.:

Reound Worms   (-Asearis spp)

Hook Worms       (Ancycostoma duodenate and Necator spp).

Whip worms        (Irichuris trichiura)

Pin Worms           (Enterobius Vermicularis)

The presence of these various types of worms in large numbers coupled with the poor living habits of large segments of the world population has made the control of these worms difficulty and their eradication nearly impossible.  That human life and the worms have been in separately interrelated is quite a challenge to mouth transmission dynamics and also that man cannot control the entry into his mouth of materials that pass through his anus is a puzzle.  Here, helminthiasis (literally means infections and parasites caused by worms) is the worst culprite.

1.1     SOURCES OF INFECTION

The primary source of worm infestation is the food or water contaminated with infected faeces.  When these parasites are passed out through the anus, some of them find their way to food used by man and get it contaminated.  Examples are Ascaris eggs on vegetables such as Solanium, lettuce, Cabbage and other vegetables eaten raw or poorly washed.  So when men feed on such contaminated foods they get infected.  Another source is the soil, that is the soil borne infections stage.  Here the eggs of these wormshatch in the soil and the third stage larva (Lz) find its way into the host by actively boring into the skin.  Examples are the hookworms (Necator, strongy bodies, Ancylostoma etc.).  Some soil-borne infective larval stage exploits human behavioural pattern for its entry.  The soil transmitted intestinal nematodes – round worms Ascaris Lumbricoides, ancylostoms duodenele and Nectator americanus rank highest among all the helminthes and their prevalence in different communities serves as an index of socio-economic status.  Ascaris and Trichuris affect the health of children especially, the former being a frequent cause of complications and death in many parts of the world, the later causing severe and stubborn – dysentery.  The hookworms are recognized as important causes of anaemia particularly in older children and young adults.  The obvious high rank of hookworm infection as a cause of debilating disease placed it first among helminthiasis to be attacked on a wide scale.

1.2     LIFE CYCLE OF WORMS HELMINTHES

These enteric parasitic worms all pass through a series of development stage before the adult stage is reached where the – organism becomes sexually mature and a new life cycle develop.  These are several live cycles depending on the organisms involved.  Within the life cycle, one on several phases of parasitic multiplication may occur depending one species it may be sexual or asexual.

DIRECT AND INDIRECT LIFE CYCLES

There are two types of life cycle viz.:

i.        Direct life cycle

ii.       Indirect life cycle

DIRECT LIFE CYCLE

Here a single host species is required for the parasite to complete it development example Trichuris trichiura and ancylostoma duodenale.

INDIRECT LIFE CYCLE

Here two or more species of host are required for the parasite to complete its life cycle example – Taenis Saginata – requires two hoots for it to complete its life cycle.  In the life cycle of ascaris, Trichuris, ancylostoma, Necator and other helminthes that commonly infect human being, the soil received the faecal contamination stages which are not infective i.e. free living then the soil provides conditions under which development to the infective stage can take place.  It provides protection for the infective stage for a period during which it fortuitously may be brought into contact with a susceptible individual whom it may enter by mouth (Ascaris, Trichuria and Ancylostoma) or by skin (Necator).  This the soil serves the parasite essentially the same manner as an intermediate host.  In the life cycle of Ascaris or in Ascariasis infection – ingesting worm eggs contamining infective larvae inside infects A patient.  The eggs hatch in the small intestine, then the larvae are liberated and then penetrated the intestinal wall, gain entrance into muscular system. 

From here they enter the liver, heart and finally the lungs.  It is in the latter organ that they reside for a week or more and induce preumonitis reactions.  Following this they ascend the respiratory tract to the pharynx where the larvae are swallowed and then mature into adult worms in small intestine after several – weeks.  The eggs are released in the faeces in a non-embryonated condition and they are incubated in the soil for a few weeks in order that the infective larva may develop.  In children ascariosis seems to be more of a hand-to-mouth kind of transmission, whereas in adult the contamination of food with infective eggs is probably the chief source of infection Muller (1989).   In the case of Hookworms i.e. Ancylostoma and especially Necator, a patient becomes infected by the contact of his/her skin to infective larvae. 

Penetration of the skin by infective hookworm larva produces a dermatitis known as dewitch or ground itch.  After skin penetration, the larvae are eventually carried to the heart, then enter the arterial circulation, and within a day or two, filter out in the lung capillaries.  After growth and development in the lungs for about a week, the larvae break into the alveolar sacs, ascend the respiratory tract and are swallowed and then develop into mature hookworms in the small intestine in a mouth or two.  Here the worms mate and the female lays eggs, which pass out in the faeces.  Necator lays about 10,000 eggs daily while Ancylostoma lays 10,000 eggs daily.  (Havard Dictionary 35th Edition). 

Under suitable conditions of the soil, the eggs develop and hatch into rhabdit form larva, which then grows and develop and then hatch into filariform larva of the worm.

1.3           PATHOGENICITY OF HOOK WORM

Pathogenicity describes the origin of damage caused by parasites and how these damage originated through the activities of parasites.  The pathogenicity of different enteric worms.  Cestodes and intestinal parasitic nematodes are briefly described here:

The first sign of hookworm infection is frequently a skin reaction at the site of larval penetration.  This is known as “ground itch” and is usually more severe in those individuals previously infected.  On the entering the host the larvae migrate through the heart and lungs and mild respiratory symptoms may devel9op.  After migrating up to the traches the larvae are swallowed.  They reach the small intestine and develop into mature worms.  The adult hookworm causes chronic blood loss.  It has been estimated that a single Ancylostoma – duodenals worm ingests about 150 ML (0.15ml) of blood per day and a Necator americanus worm about 30 ML (0.03ml).  the Chronic loss of blood cause anaemia and Oedema, resulting in severe cases in retardation of growth and mental.

The fertile egg is avoid, non-embyonated and the egg shell has an outside rugose – layer of material while the infertile egg is ellipsoid, being longer and narrower than fertile eggs.  Eggs will obviously not be present if the infection is only with male worm and in such cases radiographic detection is order.

AIMS AND OBJECTIVE OF THE STUDY

(i)            To examines the prevalence level of parasitic worm infection in Enugu State, using Asata Zone as a case study.

(ii)           To know the most frequently occurring worms in our pupils in primary schools.

STATEMENT OF PROBLEM

The human environment and human – behaviour are highly synchronized with the life cycle of worms and other parasites such that there are very high chance of infection.  The primary school pupils are more exposed because of their careless habit and ignorance.

HYPOTHESIS

Ho           -               Very wormy environment signifies high infections rate

detectable from school samples.

Hi            -               Although habit is synchronized with transmission, worm

infestation if any, can n0t be detected from stool samples.

SIGNIFICATION OF STUDY

A parasitological stool analysis can be used to diagnose intestinal infections with endoparasites such as helminthes worms, by identification of their segments, ova, or whole worm in the stool.