Parasitic Infections Flashcards
Define infection
invasion by and growth of pathogenic microorganisms within the body
Define disease
a disordered or incorrectly functioning organ, part, structure, system … etc..
Define parasite
organism living in or on the host and dependent on it for nutrition - causing damage
What are the two categories of endoparasites
Protozoa
Metazoa
Describe the protozoa
Eukaryotic and single-celled
Pathogenesis varied
Some have insect vectors e.g. malaria
No eosinophilia
Give examples of types of protozoa
Amoeba e.g. entamoeba histolytica
Coccidiae e.g. plasmodium species
Ciliae e.g. balantidium coli
Flagellates e.g. Giardia, leishmania
Describe the metazoa
Multicellular organisms (Helminths/worms) Free living, intermediate hosts and vectors Some may just inhabit the gut (geohelminths), while others invade tissues Eosinophilia if it invades blood
Give examples of types of metazoa
Roundworms e.g. ascaris, hookworm
Flatworms e.g. taenia (tape)
Flukes e.g. schistoma
Describe the epidemiology of amoeba infections
10% of the world is infected with E. histolytica
3rd most common cause of death of parasitic infection (after schistosomiasis and malaria)
90% asymptomatic
More common int eh tropics than in temperate climes
What does infection with amoebae cause
Amoebiasis which causes dystentery (bloody diarrhoea) and liver abscess
How does E. histolytica infection spread
Faecal-oral route (human only reservoir)
In the small intestine, E. histolytica cysts release active amoebic parasites (trophozoites) which invade the colon’s epithelial cells and cause flask-shaped ulcer
Infection can then spread via blood to other organs (liver, lungs, brain)
Give a reason to explain why E. histolytica infection is so widespread
asymptomatic carriers pass cysts in faeces
asymptomatic carriage state can persist indefinitely. Cysts
remain viable for up to 2 months.
What is the difference between E. dispar and E. hystolitica
E. dispar is a normal commensal in the GI tract
What do the different types of coccidia (plasmodium, toxoplasma and cryptosporidium) cause
Plasmodium - malaria
Toxoplasma - toxoplasmosis (a mild disease for immunocompetent people but very dangerous to a fetus)
Cryptosporidium - diarrhoea
Explain how plasmodium is spread
Hosts in humans and female anopheles mosquitos
2 stages: liver and blood
What are the symptoms of malaria
Can appear from 7days - 1 year
Fever, headache, chills, vomiting, muscle pain
Paroxysm (cycle in 4-8hrs)
What re the complications of malaria
Severe anemia Cerebral malaria (swelling of the brain,seizures, coma) liver failure Shock Pulmonary edema abnormally low blood sugar kidney failure swelling and rupturing of the spleen
Explain how toxoplasma spreads
pet faeces
undercooked meat (of animals harbouring cysts)
organ transplantation or blood transfusion.
What are the risks of toxoplasma to immunocompromised patients
may develop central nervous system disease, brain lesions, pneumonitis or retinochoroiditis
Where do toxoplasma cysts form
tissues, mainly muscle, the brain and eyes, which may remain for life
How does cryptosporidium spread
infected water, either drinking water or in swimming pools etc.
What are the symptoms of cryptosporidium infection
Diarrhea, fever, nausea, vomiting in humans
very common in HIV+ patients presenting with diarrhea.
What are the symptoms of Balantidium coli
No symptoms
Immunocompromised - persistent diarrhoea, sentry, abdominal pain, weight loss, nausea, vomiting, perforation of colon
Explain how balantidium coli is spread
globally carried by pigs, rodents, and primates.
The life cycle of B. coli is very similar to E. histolytica
What does giardia lambia cause and how
Giardiasis (traveller’s diarrhoea)
(most common water-borne protozoal infection)
flagellated trophozoites attach to duodenal or jejunal epithelium
What are the symptoms of giardiasis
Diarrhoea Greasy stools that tend to float Stomach or abdominal cramps Upset stomach or nausea/vomiting Dehydration (loss of fluids)
How is trichomonas transmitted
Sexually
Flagellate
The trophozooites attach inside the vagina or urethra, and cause abnormal discharge. It can be spread by secretions and urine.
What is the vector for leishmania
Sand fly
Leishmania have flagella which are retracted after being injected into humans via sandfly bites, becoming immobile
Where are sand flies found and describe the appearance (+gender difference)
Warmer parts of the world (everywhere but N. America, N. Europe and Asia and poles)
3mm long and hairy, smaller than mosquitoes and silent
Only females feed on blood
What are the 4 major types of leishmaniasis
visceral leishmaniasis
localised cutaneous leishmaniasis
diffuse cutaneous leishmaniasis
mucocutaneous / mucosal leishmaniasis
Describe visceral leishmaniases (Common name, fatality, risk factors, PKDL)
Black fever / kala Azar
Fatal if untreated, 30-100 subclinical infections
Risk factors include malnutrition and immuno- suppression (either by drugs or HIV)
post-kala azar dermal leishmaniasis (PKDL) is common during or after treatment
What are the symptoms of visceral leishmaniases
irregular fever weight loss hepatomegaly splenomegaly anaemia
What is the treatment for visceral leishmaniases
IM or IV sodium stibogluconate or meglumin antimoniate
Describe localised cutaneous leishmaniasis
Causes skin lesions on exposed body parts, which can be ulcerating
Are often self-healing and lead to immunity against re-infection, but can create serious disability and scars
Species include L. major and L. tropica.
Describe diffuse cutaneous leishmanias
causes multiple, nodular, non-ulcerating skin lesions often on the face and hands.
L. aethopica.
Describe mucocutaneous leishmanias
caused by L. braziliensis, affects the skin around the mouth, causing disfigurement.
Describe mucosal leishmanias
Mucosal leishmaniasis just destroys the mouth and lips themselves (mucous membranes)
L. infantum as well as L. major, L. tropica, and L. aethopica.
Which of the leishmania types is most common
LCL is by far the most common > MCL > DCL
What is the treatment for Leishmanias
SSG either systemically or intra-lesion, and/or cryotherapy.
Give 2 important cell surface molecules on leishmania
lipophosphoglycan (LPG) and gp63, a protease They can inhibit the fusion of the phagosome and lysosome in macrophages and neutrophils, and also inhibit activation, suppressing MHC class I and II expression and other signalling
What are the most common worm infections
Ascariasis
Trichuriasis
Hookworm
Schistosomiasis
What does ascaris lumbricoides cause
ascariasis
Adult worms are ~20-30cm in length. One female can produce hundreds of thousands of eggs per day, which get passed in the faeces.
What is the timescale at which female Ascaris lumbricoides can produce eggs and live
It takes 2-3 months from egg ingestion to having an adult female able to produce her own eggs.
Adult worms can live for 1-2 years.
What are the symptoms of ascariasis
Often asymptomatic
May cause abdominal pain, intestinal obstruction, exacerbation of existing malnutrition
Migration of larvae - Loeffler’s pneumonia
What occurs in loeffler’s pneumonia
larvae penetrating from capillaries into the lungs causes pools of blood and dead epithelial cells to clog air spaces.
This increases the patient’s susceptibility to potentially fatal bacterial infections.
Describe hookworms
about 1cm long, and attach by their ‘mouth’ to the villi of the small intestine.
What are the symptoms of hookworm infection
A few worms may cause no symptoms, but having hundreds can cause bloody diarrhoea and anaemia because the worms leave open wounds in the intestinal mucosa.
This also leads to inflammation of the bowel.
Describe the trichuris trichuria
whipworm, is used as therapy for allergy and autoimmune disease
What does filaria cause and how
Lymphatic filiariasis
Obstruction of lymphatic vessels, usually in a leg, leading to elephantiasis
(may also obstruct the arm, breast or scrotum)
Describe infection by tapeworms/cestodes
Taenia solium from pork and Taenia saginata from beef
Tapeworms attach to the small intestine and can be ~3m long in adulthood.
What are the symptoms of tapeworm infection
Most have no symptoms
Those with taenia saginata have more symptoms
Abdominal discomfort
Diarrhoea
Weight loss
Visible active passing of tapeworm segments in the stool
Give examples of ectoparasites
Scabies (Sarcoptes scabiei), mites whose females burrow into the epidermis to lay their eggs
Lice, including head lice (Pediculus capitis, ‘nits’ are their eggs) and pubic lice (Pthirus pubis)
What does loa loa cause
Loaiasis - eye worm
