WEEK 4: HELMINTHS AND ATHROPODS Flashcards
Define the following terms:
- Parasite
- Infection
- Infestation
- Definitive host
- Intermediate host
Parasite is an organism that spends a significant portion of its life in or on the living tissue of a host organism and which causes harm to the host without immediately killing it.
Infection : invasion of endoparasites
Infestation : external parasitism of ectoparasites such as arthropods.
Definitive host –harbors the adult or sexual stage.
Intermediate host- part or all of the larval or asexual stage takes place.
What are helminths?
The term “helminth” is used for all groups of parasitic worms.
Where does the highest prevalence occur?
The highest prevalence occurs in tropical countries with:
* Poor or inadequate food supplies
* Where insect, molluscs and other invertebrate vectors abound
* Sanitary conditions are poor.
State the three main groups of helminths important in humans.
*Tapeworms (Cestodes)
*Flukes (Trematodes)
*Roundworms (Nematodes)
Outline general characteristics of Helminths.
Body cavity?
Feeding?
Digestive system?
Nervous system?
Excretory system?
Reproductive system?
Locomotion?
Host?
No true coelomic or body cavity
Outer protective covering, the cuticle or integument
Mouth with teeth/cutting plates, suckers/hooks.
Digestive system absent/rudimentary
Primitive nervous system
Excretory system better developed.
Reproductive system most developed.
Locomotion by muscular contraction and relaxation.
Parthenogenic- produce fertile eggs or larvae without mating.
Unable to multiply in the body of the host.
Require more than one intermediate host.
What does the term parthenogenic mean?
Parthenogenic- produce fertile eggs or larvae without mating.
Define the following terms:
*Hermaphrodites
*Dioecious
- Hermaphrodites:
-Hermaphrodites are organisms that have both male and female reproductive organs within the same individual. - Dioecious:
-Dioecious organisms are the opposite of hermaphrodites. Dioecious species have individuals that are distinctly male or female, with separate reproductive organs.
State the four distinct ways in which the transmission of helminths occurs.
- Fecal-oral route
- Injection by blood sucking insects
- Active skin penetration
- Via intermediate host: Accidental ingestion of
larva in tissue of another host
Give examples of cestodes.
Taenia saginata
Taenia solium
Echinococcus granulosum- dog tapeworm
Diphyllobothrium latum -fish tapeworm
Most common tapeworm found worldwide.
Definitive hosts- Humans
* Acquired from eating uncooked beef
The worm ≈ 10 meters in length
Each segment (proglottids) contain nervous, muscular, excretory , male and female genital systems,
The uterus having 15–30 lateral branches
( T. solium has 7–12).
Symptoms: non-specific -intermittent pains or indigestion.
Tapeworm segments (proglottids) in stool
Diagnosis: Stool examination for eggs or segments.
Treatment: Praziquantel / Niclosamide
Prevention: Sewage treatment; cook or freeze beef
What is the name of the tapeworm described above?
Taenia saginata/solium
What is the difference between mature proglottid of taenia saginata and solium primary uterine branches?
What are proglottids?
Mature proglottid of T. saginata primary uterine branches >12.
Mature proglottid of T. solium primary uterine branches <13.
Are a distinct structural feature found in the tapeworms, which are a type of parasitic flatworm belonging to the class Cestoda.
Tapeworms are characterized by their long, flat bodies composed of multiple segments, and each of these segments is called a proglottid.
Taenia solium causes cysticercosis.
What is cysticercosis?
Describe the life cycle of taenia solium.
Cysticercosis is a parasitic infection caused by the larval stage of the tapeworm Taenia solium.
In this infection, the larvae, known as cysticerci, can develop in various tissues of the human body, including the muscles, eyes, brain, and other organs.
- T. solium eggs enter the body through ingestion of contaminated food or water.
- Larvae penetrate small intestine mucosa.
- Deposited and grow in muscle subcutaneous, brain, eye, heart.
- Form small (1-3 cm) fluid filled cysts- Cysticercosis, with an invaginated scolex.
How long can taenia solium live for?
How does oit affect the brain?
Live for ~7 years
Pathology -as space occupying lesions (especially brain)
Foci of host inflammatory response when the cyst eventually dies or is killed with anti- helminthics.
Seizures or hydrocephalus.
Hydrocephalus is the buildup of fluid in cavities called ventricles deep within the brain.
What is the other name for Echinococcus granulosis?
What are its definitive hosts?
What are its intermediate hosts?
What is the method of transmission?
Where is it most prevalent?
Describe their physical attributes.
Echinococcus granulosis (Dog tapeworm)
Definitive Host: dogs
Intermediate hosts: sheep, cattle, goats, and pigs, Human.
Eggs passed in dog feces.
Eating raw vegetables or food contaminated with dog feces.
Prevalent in cattle rearing areas.
Size 3-6mm, only 3 proglottids
Scolex with 4 suckers and rostellum with 2 rows of hooklet.
Hexacanth embryo
What are hydatid cysts?
What are the larvae of the Echinococcus granulosis called?
Where does it develop into cysts?
Outline the 3 diagnostic methods.
Outline the treatment options.
State the 2 chemotherapy drugs used.
Hydatid cysts, also known as echinococcal cysts, are fluid-filled cysts that form as a result of an infection with the larval stage of the Echinococcus tapeworm.
The larvae (protocolises) of Echinococcus granulosis develop into cysts in various organs, most commonly in the liver and lungs.
DIAGNOSIS:
*Imaging studies, such as ultrasound, CT scans, or MRI, to visualize the cysts.
*Blood tests
*Serological tests can also help confirm the presence of the infection.
TREATMENT:
*Surgical removal of the cysts.
*Anti-parasitic, cyst puncture, and PAIR percutaneous aspiration, injection of chemicals and re-aspiration)
ANTI-PARASITIC DRUGS
*Albendazole 10 to 15 mg/kg body weight per day (max 800 mg po in 2 doses) in several one-month courses with treatment-free intervals of 14 days
MOA: Albendazole disrupts the parasites’ ability to absorb glucose, which affects their energy metabolism and leads to their death.
*Mebendazole 40-50 mg/kg body weight per day
MOA: Mebendazole disrupts the parasites’ ability to absorb glucose, which impairs their energy metabolism and leads to their death.
