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.
200 million in 74 countries infected
120 million symptomatic
20 million have severe illness.
Endemic in Africa and West Asia
Dioecious
Definitive host –Human
Intermediate host- Snail
Live in venous plexus of the body
Size: males -10-15mm long 1mm thick
females -20mm long, 0.25mm thick
Gynaecophoric canal
What fluke is described above?
Schistosoma haematobium.
State the 3 important species of schistoma and the diseases they cause.
Three important species:
Schistosoma haematobium-Urinary bilharziasis
Schistosoma mansoni- Intestinal bilharziasis
Schistosoma japonicum- Katayama disease
Describe the characteristics of the schistoma haematobium.
*Vesical and pelvic plexus
Skin penetration-dermatitis, fever, headache, urticaria
Egg deposition and extrusion-Painless terminal hematuria with hyperplasia and inflammation of bladder
Tissue proliferation and repair-chronic stage.
Hyperplasia and fibrosis of the vesical mucosa with a granular sandy appearance. -Sandy patch
Calculi forms
Urinary carriage of typhoid bacilli
Bladder cancer
Venules of inferior mesenteric plexus.
Eggs penetrate gut wall and reach colonic lumen and shed in feces.
Pruritic rash
Colicky abdominal pain, bloody diarrhea.
Inflammatory reaction causes micro abscesses, granulomas, hyperplasia fibrosis, hepatosplenomegaly, and portal hypertension.
What parasite is described above?
Schistosoma mansoni- Intestinal bilharziasis
What is Katayama disease?
Ouline the signs and symptoms of the disease.
Katayama disease, also known as Katayama syndrome, is a term used to describe a type of acute schistosomiasis, which is an infection caused by parasitic flatworms called Schistosoma.
Venules of superior mesenteric plexus, intrahepatic portal venules and hemorrhoidal plexus of veins
Eggs penetrate the gut wall and passed in feces.
SYMPTOMS:
Fever, abdominal pain, diarrhea and allergic manifestation_
Anaphylaxis or toxic symptoms: headache, urticaria, enlarged liver and spleen, Leukocytosis, eosinophilia -Katayama fever.
Immune complex disease –antibodies to schistosomula, adult worm and eggs
Hepatomegaly, fibrosis, portal hypertension, esophageal varices, GI bleeding, splenomegaly and also involve brain and lungs.
Outline the diagnosis of intestinal Schistosoma.
Outline prevention methods.
*History of freshwater exposure
*Stool for O&P
*Serology
*Antigen capture
*Eosinophilia
*Liver biopsy
*Abdominal ultrasound / CT
Prevention:
Control of snails
Sewage treatment and disposal
Outline the Intestinal, Hepatic and Pulmonary flukes.
Fasciolopsis buski- small intestine
Gastrodiscoides hominis-large intestine
Clonorchis sinensis-liver
Opisthorchis felineus-liver
Fasciola hepatica-liver
Paragonimus westermani-Lung
What are the definitive host and 2 intermediate host for the Intestinal, Hepatic and Pulmonary flukes.
Definitive host: Man
Two intermediate host: snail and fresh water fish or water plants
Clonorchis sinensis, Opisthorchis spp, Fasciola spp. (liver flukes)
Describe the:
*Transmission
*Life-cycle
*Clinical manifestations of the above mentioned.
Transmission: consumption of infected freshwater fish
Life cycle: adult flukes live in biliary radicles
Clinical: ascending cholangitis, cholelithiasis, cholangiocarcinoma
Transmission: consumption of infected freshwater crabs
Life cycle: adult flukes live in lung.
Clinical: pulmonary nodules/masses, hemoptysis
Diagnosis: - stool, urine or sputum for ova; serology
Treatment: - praziquantel (triclabendazole for Fasciola)
What parasite is described above?
Paragonimus spp. (lung flukes)
State 2 ways of transmission of 2 soil-transmitted helminths two distinct groups:
*Infection occurs by swallowing the infective eggs- Ascaris lumbricoides (roundworm), Trichuris trichiura (whipworm)
*Infect by active skin penetration by infective larvae then migration through the lungs to the intestine. Ancylostoma duodenale, Necator americanus -(hookworms) and Strongyloides stercoralis
State the soil-transmitted nematodes-Clinical features.
Cause morbidity in humans by:
*Affecting nutritional equilibrium
*Inducing malabsorption of nutrients competing for absorption of micronutrients
*Reducing food intake
*Reducing growth
*Affecting cognitive development
*Inducing tissue reactions, such as granuloma
*Inducing intestinal bleeding
*Causing surgical complications such as obstruction, rectal prolapse and abscess
State the 2 examples of human hookworms.
What are the serious effects of hookworms.
The human hookworms include:
*Ancylostoma duodenale
*Necator americanus
Asymptomatic/ mild gastrointestinal symptoms
The most serious effects –
*Blood loss leading to anemia
*Protein loss.
Ancylostoma caninum
Ancylostoma braziliensis
Non-human (dog, cat etc) hookworms
Migrate and produce serpiginous itchy tracts in subcutaneous tissue
Treatment: Albendazole
Ivermectin
Name the parasite.
Cutaneous Larva Migrans
Threadworm or seat worm
Common in affluent nation cold and temperate region
Adults are short, white, fusiform worms with pin like pointed ends in female -appears as white threads.
Monoxenous-passes entire life cycle in human
Infection common in children
Itching in the perianal and perineal region
Autoinfection and retro infection occur
Treatment-Mebendazole
Name the parasite.
Enterobius vermicularis (pinworm)
Epidemiology - about 350 million infected, in some areas 90-100% of population
Life cycle: people infected by swallowing embryonated egg
Egg hatches in small intestine attaches to colonic epithelium (caecum/appendix) and matures to egg laying in 3 months.
Clinical features
Frequent small blood-streaked diarrheal stool.
Rectal prolapse.
Treatment: Mebendazole
Name the parasite.
Trichuris trichiura-Whip worm
Largest nematode-20-40cms
200,000 eggs per day
Migrating larvae cause pneumonia- like symptoms
Loeffler’s syndrome-Ascaris pneumonia
Heavy intestinal infection –
obstruction, interfere with digestion, obstructed bile/pancreatic ducts due to migration.
Protein energy malnutrition
Vit A deficiency
Luminal occlusion
Lab diagnosis: Eggs in fecal concentrates. Worms sometimes passed.
Charcot-Leyden crystals in sputum
Treatment: Mebendazole
Albendazole, Ivermectin.
Prevention:
Hygiene and sanitation
Name the parasite.
Ascaris Lumbricoides
State characteristics of Onchocerca volvulus –River blindness
Chronic infection of subcutaneous tissues, skin and eyes
Leopard skin/ Lizard skin
African eye worm.
The vector - flies genusChrysops
Calabar swellings-fugitive swelling- nodules
Subconjunctival migration of adult worm granulomas
Name the parasite.
Loa loa
Serpent worm
Viviparous-discharges larvae
Toxin secreted-blister formation, ulcer
Name the parasite.
Dracunculus Medinensis-Guinea worm
Outline medically important arthropods.
Pediculus humanus var. capitis-head louse
Pediculus humanus var. humanus-body louse
Phthirus pubis – crab louse.
Myiasis
Sarcoptes scabiei- Scabies
Fleas
Tunga penetrans
