7: Parasitic Infections Flashcards
Difference between infection and disease
Infection = invasion and growth of pathogenic microorganisms within body
Disease = non-functioning organ/structure/system of body resulting from many factors
Definition of parasite
Organism living in host - dependent on it for nutrition
Causes damage
Classification of parasite
Endoparasites - 2 subtypes: protozoa + metazoa
Ectoparasites
What are protozoa parasites
Single celled organisms
EUKARYOTES (genome in nucleus + complex organelles)
NO eosinophilia
What are metazoa
Multicellular organisms (aka Helminths/worms)
FREE living
Mostly humans are the only host (few zoonoses)
Some inhabit gut, others invade tissues
Eosinophilia if blood is invaded
What are the types of protozoa parasites?
Amoeba
Coccidia
Ciliates
Flagellates
Give an example of amoeba and how they infect
Entamoeba histolyca
Entamoeba dispar
Faecal-oral transmission
Infection occurs by ingesting mature cysts in food/water
10% of world population infected with E.histolyca
Only 10% infections cause disease
Invasive amoebiasis -> amoebic liver abcess but can also affect lung, heart, brain, urinary tract, skin
Name 3 coccidia, how they infect and give clinical features of each.
Most coccidiae are zoonoses
- Plasmodium - causes MALARIA
Mosquito-born
Symptoms: Fever, headache, chills, vomiting, muscle pain
Paroxysm
Complications: severe anaemia, cerebral malaria, kidney/liver failure, rupture of spleen, etc.. - Toxoplasma gondii
Infection by:
- eating undercooked meat harboring cysts
- Food/water contaminated by cat faeces
- Blood transfusion/organ transplantation
- Transplacentally (DANGEROUS FOR FETUS)
Immunocompromised patients may develop CNS diseases, brain lesions, etc.. - CryptosporidCium
Faecal-oral transmission
Causes diarrhoea/fever
Very common in HIV positive patients
Name an example of ciliate, route of infection and clinical symptoms.
Balantidium coli - balantidiasis Faecal-oral Hosts: pigs, rodents, primates Most infected people -> NO SYMPTOMS Immunocompromised -> diarrhoea, dysentry, abdominal pain, weight loss, nausea, vomiting
If left untreated, perforation of colon may occur
Name 3 flagellates, route of infection and clinical symptoms.
- Giarda lamblia
Faecal-oral transmission
Causes diarrhoea - Trichomonas
Sexually transmitted
Around 10-50% are asymptomatic
Females: vaginal discharge, vulval ulceration, dysuria
Males: discharge, dysuria
Complications: preterm delivery/low birth weight
May enhance HIV - Leishmania
2 forms:
Promastigote = form of leishmania inside sand fly vector, moves with flagella
Amastigote = form of leishmania inside host cell, flagella is absorbed, NOT motile
What age group do helminths affect the most?
Children under 10
Name the 3 types of Helminths
Roundworms (Nematodes)
Flatworms (Cestodes)
Flukes (Trematodes)
Name 4 nematodes. Give their route of infection and clinical features.
- Ascariasis
Adult worms live in lumen of intestine
Female produces eggs, passed into faeces
Fertile eggs embryonate, infective eggs swallowed
Larvae hatch and invade intestinal mucosa -> go to lungs
Mature further in lungs, ascend to throat, then swallowed
When they reach small intestine, they develop into adult worms
Symptoms:
- Often asymptomatic
- Large no. of worms -> abdominal pain, intestinal obstruction
- Can lead to Loeffler’s pneumonia - Hookworm
Penetrates through skin
Causes Iron deficiency anaemia (Ancylostoma duodenale) due to blood loss in intestine
GI/metabolic/resp symptoms
3. Trichuris Trichiura (aka Whipworm) TYPE OF HOOKWORM Faecal-oral transmission Small no. of whipworms = asymptomatic Large no. = anaemia, bloody diarrhoea due to blood loss
4. Filaria E.g. Brugia malayi, Wucheria bancrofti Transmitted via mosquito Causes lymphatic filariasis Loa loa (eye worm) - transmitted by flies, causes loaiasis (only in Africa)
Name an example of cestode (flatworm), route of infection and clinical features.
Taenia species (tapeworms)
Eggs eaten by pig/cow
Eggs transmitted by eating raw/undercooked meat
Most people asymptomatic, can cause abdominal pain/weight loss
Taenia solium (pigs) = COMMONEST CAUSE of ACQUIRED EPILEPSY
Name an example of trematodes (Flukes), route of infection and clinical symptoms.
Schistosoma - causes schistosomiasis
Eggs eliminated in faeces/urine in water
Snail -> cercaria -> penetrates skin
Symptoms:
Rash/itchy skin (within days)
1-2 months - mostly asymptomatic
Eggs produced from adult worms -> travel to intestine/liver/bladder causing inflammation/scarring
Children who are repeatedly infected -> anaemia/malnutrition
