parasitologyparasitology

• Medical Parasites:

• - Protozoa 1- Platyhelminthes

• - Helminthes: 2- Nemathelminthes

• - Arthropoda 3- Nematomorpha

4- Acanthocephala

5- Annelida

WHO Classified of Helminthes WHO Classified of Helminthes According to transmission methods According to transmission methods

• 1- Soil transmitted Helminthes : Ascaris, Hook worms

• 2- Snail t. H. : Trematoda( Schistosoma,….)

• 3- Arthropods t. H. : Filaria, Dracanculus medinensis

• 4- Food and Meat t. H. : Taenia saginata, Taenia solium

• 5- Direct t. H. ( contagious H.): Enterobius vermicularis,…

Nematoda

General Discription

Morphology

Reproductive systemReproductive system

Digestive systemDigestive system

Bucal cavity

Classification of nematodaClassification of nematoda

• 1- Intestinal Nematodes

• 2- Blood & Tissue Nematodes

• 3- Animal Nematodes: which larve stage of them is infective for human

Ascaris lumbricoidesAscaris lumbricoides

• Causal Agent:Is the largest nematode (roundworm) parasitizing the human intestine.

•   (Adult females: 20 to 35 cm; adult male: 15 to 30 cm.)

Ascaris lumbricoidesAscaris lumbricoides

• Aetiology:• Size• color

Anterior & Posterior endAnterior & Posterior end

Geographic DistributionGeographic Distribution

Life cycleLife cycle

Microscopy diagnosis

Clinical Features

Lung phase ( larval migration): - Loeffler’s syndrome).

Adult worms : usually cause no acute symptoms. 

High worm burdens may cause abdominal pain and intestinal obstruction.

 

Heavy InfectionHeavy Infection

Migrating adult worms 

PathogenesisPathogenesis

Laboratory DiagnosisLaboratory Diagnosis

• Microscopic identification of eggs in the stool is the most common method for diagnosing intestinal ascariasis

TreatmentTreatment

• The drugs of choice for treatment of ascariasis are albendazole*, mebendazole, and pyrantel pamoate

Enterobius vermicularisEnterobius vermicularis

• Causal Agent:Oxyuris vermicularis, also called human pinworm or seatworm. 

• (Adult females: 8 to 13 mm, adult male: 2 to 5 mm.) 

• Humans are considered to be the only hosts of E. vermicularis. 

Adult MaleAdult Male

Life cycleLife cycleLife Cycle:

                                                                 

Geographic DistributionGeographic Distribution

Worldwide, with infections more frequent in school- or preschool- children and in crowded conditions. 

Enterobiasis appears to be more common in temperate than tropical countries. 

Clinical FeaturesClinical Features

• Enterobiasis is frequently asymptomatic. 

• The most typical symptom is perianal pruritus, especially at night, which may lead to excoriations and bacterial superinfection. 

• Occasionally, invasion of the female genital tract with vulvovaginitis and pelvic or peritoneal granulomas can occur. 

• Other symptoms include anorexia, irritability, and abdominal pain.

PathogenesisPathogenesis

Cross-section of human appendix Cross-section of human appendix containing containing Enterobius vermicularisEnterobius vermicularis

                                                       

     

                                                       

     

                                                       

     E F G

• ("Scotch test", cellulose-tape slide test

• Alternatively, anal swabs or "Swube tubes" (a paddle coated with adhesive material) can also be used.

•   • Adult worms are also diagnostic, when found in the

perianal area, or during ano-rectal or vaginal examinations

Laboratory DiagnosisLaboratory Diagnosis

Microscopy diagnosisMicroscopy diagnosis

TreatmentTreatment

The drug of choice is pyrantel pamoate. 

• Measures to prevent reinfection, such as personal hygiene and laundering of bedding, should be discussed and implemented in cases where infection affects other household members.

Trichuris trichiuraTrichuris trichiura( also called the human whipworm)( also called the human whipworm)

Life CycleLife Cycle

Geographic DistributionGeographic Distribution

• The third most common round worm of humans. 

• Worldwide, with infections more frequent in areas with tropical weather and poor sanitation practices, and among children. 

• It is estimated that 800 million people are infected worldwide.

Clinical FeaturesClinical Features

Most frequently asymptomatic.  Heavy infections, especially in small children, can cause

gastrointestinal problems (abdominal pain, diarrhea, rectal prolapse) and possibly growth retardation

Whipworm in the gutWhipworm in the gut  

Prolapsed Rectum Prolapsed Rectum

Laboratory diagnosisLaboratory diagnosis

• Microscopic identification of whipworm eggs in feces is evidence of infection. 

TreatmentTreatment

Mebendazole is the drug of choice, with albendazole as an alternative

HookwomsHookwoms

• Human Hookworms:Human Hookworms:• 1) Ancylostoma duodenale1) Ancylostoma duodenale• 2) Necator americanus2) Necator americanus

• Animal hookworms:Animal hookworms:• 1) A. caninum1) A. caninum• 2) A. braziliense2) A. braziliense• 3) A. ceylanicum3) A. ceylanicum• ……………………………………..

Ancylostoma duodenaleAncylostoma duodenale

Necator americanusNecator americanus

Geographic DistributionGeographic Distribution

• The second most common human helminthic The second most common human helminthic infection (after ascariasis). infection (after ascariasis). 

• Worldwide distribution, mostly in areas with Worldwide distribution, mostly in areas with moist, warm climate. moist, warm climate. 

• BothBoth N. americanusN. americanus andand A. duodenaleA. duodenale are are found in Africa, Asia and the Americasfound in Africa, Asia and the Americas.  . 

• Necator americanusNecator americanus predominates in the predominates in the Americas and Australia, while onlyAmericas and Australia, while only A. A. duodenaleduodenale is found in the Middle East, North is found in the Middle East, North Africa and southern EuropeAfrica and southern Europe..

Life cycle

Clinical FeaturesClinical Features

* Iron deficiency anemia (caused by blood loss at the * Iron deficiency anemia (caused by blood loss at the site of intestinal attachment of the adult worms) is the site of intestinal attachment of the adult worms) is the most common symptom of hookworm infection, and most common symptom of hookworm infection, and can be accompanied by cardiac complications. can be accompanied by cardiac complications. 

* Gastrointestinal and nutritional/metabolic symptoms * Gastrointestinal and nutritional/metabolic symptoms can also occur.  can also occur. 

* In addition, local skin manifestations ("ground itch") * In addition, local skin manifestations ("ground itch") can occur during penetration by the filariform (L3) can occur during penetration by the filariform (L3) larvae, and respiratory symptoms can be observed larvae, and respiratory symptoms can be observed during pulmonary migration of the larvaeduring pulmonary migration of the larvae

skin manifestationsskin manifestations

Section of adult hookworm in small Section of adult hookworm in small intestineintestine

Laboratory DiagnosisLaboratory Diagnosis

Microscopic identification of eggs in the stool is Microscopic identification of eggs in the stool is the most common method for diagnosing the most common method for diagnosing hookworm infectionhookworm infection

                          

    

                          

    A B

C: Hookworm egg, advanced cleavage D: Embryonated hookworm egg.

C D

•

Hookworm rhabditiform larva

Hookworm filariform larvaHookworm filariform larva

                                                  

     

                                           

    G H

TreatmentTreatment

In countries where hookworm is common and In countries where hookworm is common and reinfection is likely, light infections are often not reinfection is likely, light infections are often not treated. treated. 

In the United States, hookworm infections are generally In the United States, hookworm infections are generally treated with albendazole*.treated with albendazole*.

   Mebendazole* or pyrantel pamoate* can also be usedMebendazole* or pyrantel pamoate* can also be used. .

• Causal Agent:Causal Agent:The nematode (roundworm) The nematode (roundworm) Strongyloides Strongyloides stercoralisstercoralis..

•     Other Other StrongyloidesStrongyloides include include S. fülleborniS. fülleborni, , which infects chimpanzees and baboons and which infects chimpanzees and baboons and may produce limited infections in humans may produce limited infections in humans

Geographic DistributionGeographic Distribution

Tropical and subtropical areas, but cases also Tropical and subtropical areas, but cases also occur in temperate areas (including the South occur in temperate areas (including the South of the United States).  More frequently found of the United States).  More frequently found in rural areas, institutional settings, and lower in rural areas, institutional settings, and lower socioeconomic groupssocioeconomic groups..

Life cycleLife cycle

Life cycle ofLife cycle of Strongyloides stercoralisStrongyloides stercoralis

Rhabditoid larveRhabditoid larve

S. stercoralis larvaS. stercoralis larva

Clinical FeaturesClinical FeaturesFrequently asymptomatic. Frequently asymptomatic. 

Gastrointestinal symptoms include abdominal pain and diarrhea.Gastrointestinal symptoms include abdominal pain and diarrhea.   Pulmonary symptoms (including Loeffler’s syndrome) can occur during Pulmonary symptoms (including Loeffler’s syndrome) can occur during

pulmonary migration of the filariform larvae. pulmonary migration of the filariform larvae. 

Dermatologic manifestations include urticarial rashes in the buttocks and Dermatologic manifestations include urticarial rashes in the buttocks and waist areas.waist areas.

    Disseminated strongyloidiasis occurs in immunosuppressed patients, can Disseminated strongyloidiasis occurs in immunosuppressed patients, can present with abdominal pain, distension, shock, pulmonary and neurologic present with abdominal pain, distension, shock, pulmonary and neurologic complications and septicemia, and is potentially fatal. complications and septicemia, and is potentially fatal. 

Blood eosinophilia is generally present during the acute and chronic stages, Blood eosinophilia is generally present during the acute and chronic stages, but may be absent with disseminationbut may be absent with dissemination..

Laboratory DiagnosisLaboratory Diagnosis

Diagnosis rests on the microscopic identification of Diagnosis rests on the microscopic identification of larvae (rhabditiform and occasionally filariform) in larvae (rhabditiform and occasionally filariform) in the stool or duodenal fluid.  the stool or duodenal fluid. 

Examination of serial samples may be necessary, and Examination of serial samples may be necessary, and not always sufficient, because stool examination is not always sufficient, because stool examination is relatively insensitiverelatively insensitive..

MicroscopyMicroscopy

• AA

Rhabditiform larvae of Strongyloides stercoralis

• BB

                                                                                          

         B

The rhabditoid esophagus is clearly visible in this larva; it consists of a club-shaped anterior portion, a postmedian constriction, and a posterior bulb.

TreatmentTreatment

•The drug of choice for the treatment of The drug of choice for the treatment of uncomplicated strongyloidiasis is ivermectin uncomplicated strongyloidiasis is ivermectin with albendazole* as the alternative.with albendazole* as the alternative.

•     All patients who are at risk of disseminated All patients who are at risk of disseminated strongyloidiasis should be treatedstrongyloidiasis should be treated