Introduction

الله بسمالرحيم الرحمن

IntroductionParasites are organisms adapts them selves to live

in or on another organisms termed host. The relationship between the parasites and host occurs in 2 form:

Commensalisms: one of two organisms (commensal) benefits while the other host is unaffected (no benefit, no harm), commensal organism referred as non pathogenic.

Parasitism : one of two organisms (parasite) benefits, gain shelter and nutrition on the expanse of the other (host). The host may suffer from wide range of functional and organic disturbances due to such association (pathogenic)

Types of parasites:Ectoparasite : lives outside on the surface of

the body (infestation). Endoparasite: lives inside the body of host

(infection).Temporary or intermittent parasite: visits

the host from time to time for food.Permanent parasite : remains on or in the

body of the host for its entire life.

Facultative parasite : organism that can exist in a free living state or as a parasite.

Obligatory parasite : can not survive without a host i.e. completely adapted for parasitic existence.

Opportunistic parasite : produces disease only in immunodeficient or immunosuppressed patients e.g. AIDS. In immunocompetent individuals the organisms may exist in latent form producing no symptoms.

Coprozoic or spurious parasite : foreign organisms which have been swallowed merely pass along alimentary canal of man (without establishment )to be recovered in faeces.

Types of hosts: a-Definitive or final host : host with adult stage

or sexually reproducing forms of the parasite. b-intermediate host : host with the larval stage or

asexually reproducing forms of parasite. c-Reservoir host : animal that harbors the same

species of parasite as man . such animal help to maintain the cycle of parasite in nature and act as a potential source for human infection with this parasite.

Disease transmitted from animals to man are known as zoonotic diseases (zoonosis).

d- Vector: an arthropod which carries the parasite from one host to another.

Mode of parasitic infections: Congenital from mother to foetus. Direct contact through the skin or sexually. Ingestion of contaminated food and water or

undercooked meat in which the infective stage has developed.

Penetration of the skin due to contact with infected soil or water stream.

Inhalation of dust carrying the infective stage of parasite.

Vectors: through the bite or faeces of infected vector or by swallowing the vector.

Autoinfection: occurs when infective stages are carried from faeces to mouth of patient.

Important terminologyPrevalence = % of infection.

Intensity = number of parasite

in the host.Incidence = % of new infection .

Endemicity Endemic infection : when a steady rate of

parasitic infection is prevalent all year around in a particular area causing a low rate of morbidity in population of this area.

Hyper-endemic infection : when prevalence is high causing a high rate of morbidity.

Epidemic infection : when there is a sharp increase in the incidence ,prevalence and morbidity rates . Epidemic outbreaks are usually due to introduction of a new parasite or vector in a non immune population.

Sporadic infection : when a parasite appear occasionally in one or few members of a community.

Habitat :

Is the site where the parasite live and multiplies in host.

Small intestine (Ascaris, Ancylostoma,Giardia).Large intestine (Enterobius,Entamoeba histolytica)Blood vessels (Schistosoma species).Blood (Plasmodium species).Muscles (Trichinelle spiralis).Lymphatic (Wucheraria bancrofti)Reticulo-endothelial system

(Leishmania,Toxoplasma).

Source of parasitic infectionFood -meat (T.saginata, T. spiralis)

-vegetables (Ascaris, E. histolytica)Water -protozoal cysts

(E.histolytica, Cryptosporidium)

-cercaria (Schistosoms)

-cyclops(D.medinensis)Soil contaminated with faeces

(Ancylostoma,Ascaris,

Strongyloides, Giardia )

Association with domestic animals -dog :(hydatid disease ,toxocariasis, leishmania)

-cat : (Toxoplasma oocyst).Arthropods :

-Blood sucking (malaria, filarial, trypanosome, leishmania).

-Mechanical transmission (ova, protozoal cysts)

- Myiasis (invasion of tissue by larvae of flies).

Blood transfusion : (erythrocytic stages of Plasmodium).Congenital transplantation :

(toxoplasma, Plasmodium).Sexual intercourse : (Trichomonas vaginalis, Phthirus

pubis).Inhalation of dust : (Enterobius ova).

Protozoa helminths

Unicellular

Single cell for all function

Mulicellular

Specialized cells

Amoebae:

move by psudobodia.

Flagellates:

move by flagella.

Ciliates :

move by cilia

Apicomplexa

(sporozoa) Tissue

parasites

Round worms

(Nematodes) cylindrical,

unsegmented

Flat worms

1-Trematodes:

leaf-like, unsegmented.

2-Cestodes:

tape-like, segmented

NEMATODES

Common intestinal nematode infection:

Enterobius (Oxyuris) vermicularis

(Pinworm,seatworm,threadworm)Trichuris trichiura (whipworm)Ascaris lumbricoides (roundworm)Ancylostoma duodenale & Necator

americanus (hookworm)

Strongyloides stercoralis

Nematodes General features:

1. Elongated worm, cylindrical, unsegmented and tapering at both ends.

2. Variable in size, measure less than 5mm~as long as 100cm.

3. Sex separate and male is smaller than female

Location of Nematodes:

Intestinal: Small intestine:

Ascaris,

Ancylostoma,

Strongyloides Large intestine:

Enterobius

Trichuris

In TissueW.bancrofti : lymphatic systemO.volvulus ,Loa loa, D.medinesis:

subcutaneous tissueTrichinella (larva): muscle, brain,

lungToxocara canisnon human species

larva carried in blood to liver, lung ,brain, eye….

ENTEROBIUS VERMECULARIS

Enterobius vermicularis (Oxyuris)

(Pin worm, seat worm, thread worm(Found all over the world.adult in lumen of cecum and appendix

from which adult female migrate to rectum.

It can be seen by naked eye as white thread ± 1cm.

Male is smaller than female ± 0.5cm, with coiled end.

LIFE CYCLE

Pathology Majority of infection is asymptomatic. Main clinical presentation pruritus ani

perianal excoriation Many cases presented with appendicitis. Ectopic enterobiasis occurs in female when

invade valva and vagina result in valvovagintis

Usually accompanied by insomnia, anorexia, loss of weight and concentration (Side effect)

Treatment Albandazole for whole family

Trichuris trichiura (Whipworm)

Trichuris trichiura (Whipworm)

World wide ,common in poor sanitation. It coexists with Ascaris because of similar

requirement. Adult live in large intestine especially caecum

and appendix –in heavy infection the whole length of large intestine affected.

Male and female worm have narrow anterior portion penetrate the intestinal mucosa

LIFE CYCLE

Embryonated egg Unembryonated egg

Infective stage Diagnostic stage

male female

Pathology light infection : asymptomaticheavy infection :abdominal pain ,bloody

diarrhea. Rectal prolapse in children is a common complication.

-Diagnosis: egg in stool characterized by its barrel shape with mucoid plugs at each pole .

Treatment :Albendazole.

Ascaris lumbricoides

Ascaris lumbricoides (roundworm)

The commonest human helminthes infection.

Found in jejunum and upper part of ileum.

Female ± 20 cm longer than male ± 10 cm

Feed on semi digested food.

LIFE CYCLE

Infective stage diagnostic stage

Embryonated egg Unembryonated

Pathology: 1-Adult worm:

Light infection : asymptomatic. Heavy infection : intestinal obstruction Migrating adult : to bile duct -jaundice 2-Larvae: Loeffler`s syndrome (imp)

Pneumonia, cough with bloody sputum

Eosinophilia, urticaria Diagnosis: -eggs in stool. -larvae in sputum. -adult may pass with stool. Treatment: albendazol

Loeffler`s syndrome: Larvae in lung

pnumonia,cough ,bloody sputum

Hook warms

Ancylostoma dudenale &Necator americanus

The commonest cause of anemia.Found in small intestine mainly jejunum.Its buccal capsule (mouth) lined with hard

hooks, triangular cutting plates and anticoagulant glands.

1 -Buccal cavity with intestinal mucosa 2- B.cavity with teeth &cutting plates anemia

LIFE CYCLE

pathology& clinical picture: - larvae: i-At the site of entry of larvae (ground itch). ii- Migration phase: cough with bloody sputum pneumonia, eosinophilia,urticaria. - Adult worm: •low worm burden: no symptoms. •Moderate to heavy burden: epigastric pain, vomiting ,simulating duodenal ulcer, hemorrhagic enteritis.

• Protein loss: hypoproteinaemia edema.

• Anemia: due to withdrawal of blood by

parasites and hemorrhage from punctured

sites lead to sever anemia = microcytic

hypochromic .Diagnosis: -Eggs in stools.;

-occult blood (+)Treatment: Albendazol

Strongyloides stercoralis

Widely distributed in tropical region worldwide .

fetal opportunistic in immuno-compromised host.

It is smallest pathogenic nematodes ± 2.5mm. adult live in mucous membrane of

duodenum jejunum rarely m.m.of bronchus.

LIFE CYCLE

Pathology and clinical picture:1-Cuteneous little reaction on penetration.

sever dermatitis at perianal region in

case of external autoinfection.2- Migration :same as hook worms .3- Intestinal: inflammation of upper

intestinal mucosa, diarrhea, upper abdominal pain clocky in nature.

Disseminated strongyloidiasis : in patient with immunodeficiency ,uncontrolled diarrhea –granulomatus changes –necrosis--perforation--peritonitis--death.

Diagnosis: (rhabditiform larvae diagnostic stage in)

-Stool examination

-Duodenal aspirate& tissue --for larvae

Treatment : albandazole

Treatment for all intestinal nematodes

Albendazole