parasitic infections Flashcards
parasitic infections: explain the classification of parasites and compare differences between them, recall examples of each and explain the main symptoms they cause
define infection
invasion by and growth of pathogenic microorganisms within the body
define disease
disordered or incorrectly functioning organ, part, structure, or system of
the body resulting from effect of genetic or developmental errors, infection, poisons, nutritional deficiency or imbalance, toxicity, or unfavourable environmental factors; illness; sickness; ailment
define parasite
organism living in/on host and dependent on it for nutrition, causing damage
2 types of parasite
endoparasite, ectoparasite
2 types of endoparasite
protozoa, metazoa
4 types of protozoa
amoeba, coccidiae, ciliate, flagellates
3 types of metazoa
roundworms, flatworms, flukes
features of protozoa
single celled organisms, eukaryotes, varied pathogenesis, some have insect vectors, no eosinophilia
features of metazoa
multicellular organisms, free living, intermediate hosts and vectors, some just inhabit gut while others invade tissues, eosinophilia if invade blood
2 examples of amoeba
E. histolyica (invasive), E. dispar (normal GI commensal)
how does infection by amoeba occur
ingestion of mature cysts in food or water, or on hands contaminated by faeces
describe time frame of amoeba infection
incubation period as short as 7 days, tissue invasion after first 4 months
describe spectrum of amoeba disease
asymptomatic -> dysentry -> amoebic liver abscess (3rs most common cause of death of parasitic infections)
describe how humans, E. histolyica’s only reservoir, are infected
cysts enter small intestine -> release active amoebic parasites (trophozoites) -> invade epithelial cells of large intestines -> cause flask-shaped ulcers -> spread ot other organs via venous system
describe laboratory diagnosis of amebiasis
wet mount of stools to look for mature cysts
treatment of amebiasis
nitroimidazole derivatives (act on trophozoite, not cyst)
in humans, what type of parasite are coccidial infections mostly
zoonoses, so via animals
3 types of coccidia infection
Plasmodium species (5 species), Toxoplasma, Crytosporidium
what disease is Plasmodium species responsible for
malaria
describe life cycle of malaria: types of host and stages in human
different types of plasmodium, 2 types of host (human and female Anopheles mosquito), 2 stages in human (liver and blood)
when do malaria symptoms appear
as early as 7 days, but can be as long as one year
symptoms of malaria
fever, headache, chills, vomiting, muscle pain, paroxysm, severe anaemia, cerebral malaria, liver and kidney failure, shock, pulmonary oedema, hypoglycaemia, rupture of spleen
treatments of uncomplicated malaria
chloroquine, tetracycline
treatments of severe malaria
ACT
diagnosis of malaria
blood film, Giema stained (rapid antigen detection tests are more expensive and less sensitive)
symptoms of toxoplasmosis in immunocompetent individuals (serious danger to foetus)
fever, swollen lymph nodes, headaches, sore throat
infection routes by Toxoplasma gondii
undercooked meat with tissue cysts, food/water contaminated by cat faeces, contaminated environmental samples, blood transfusion, organ transplantation, transplacentally
diagnosis of toxoplasmosis
serological test
what can toxoplasmosis in immunocompromised patients cause
CNS disease, brain lesions, pneumonitis, retinochoroiditis
disease caused by cryptosporidium, and major symptoms
cryptosporidiosis, causing diarrhoea (more severe in immunocompromised)
transmission of cryptosporidium
faecal-oral
diagnosis of cryptosporidiosis
stool examination
treatment of cryptosporidiosis
fluid rehydration
disease caused by ciliate protozoa Balantidum coli
balantidiasis
reservoir hosts of Balantidum coli
pigs, rodents, primates
symptoms of Balantidum coli
persistent diarrhea, dysentery, abdominal pain, weight loss, nausea, and vomiting (left untreated, perforation of colon)
diagnosis of Balantidum coli
stool examination
problem of asymptomatic carriers
don’t get treated as no symptoms, but still spread disease
disease caused by flagellate Giardia lamblia
giardiasis
2 stages of giardiasis
trophozoites, cysts
acute symptoms of giardiasis
diarrhoea, greasy floating stools, stomach cramps, dehydration
diagnosis of giardiasis
stool examination
treatment for giardiasis
metronidazole
example of flagellate transmitted sexually
trichomonas
symptoms of trichomoniasis
discharge, dysuria
complications of trichomoniasis during pregnancy and for HIV
preterm delivery, low birth weight; enhances HIV transmission
diagnosis of trichomoniasis
microscopy, rapid test
treatment of trichomoniasis
metronidazole
another type of flagellate
Leishmania
features of Helminths (metazoa)
complex multicellular parasites, cycles may involve insect vectors and intermediate hosts, humans are definitive host for most, adult worms can’t multiple in humans, number of adults related to infection, lay eggs, microfilaria, larvae
4 examples of roundworms (nematodes)
Ascaris, hookworm, Filaria, Strongyloides
Ascaris transmission
eggs transmitted by faeces (faecal-oral transmission and carried to lung by portal system)
symptoms of ascariasis
usually asymptomatic but if many worms will cause abdominal pain and intestinal obstruction; feeding on contents can cause malnourishment, and penetration of larvae from capillaries into lungs can lead to Loeffler’s pneumonia
diagnosis of ascariasis
stool examination
treatment of ascariasis
mebendazole
transmission of hookworm
larvae go through skin and into blood vessels, lungs then GI
symptoms of hookworm
iron deficiency anaemia (blood loss due to GI attachment), GI and nutritional/metabolic symptoms, respiratory symptoms
diagnosis of hookworm and whipworm
stool examination
treatment of hookworm and whipworm
mebendazole
transmission of whipworm (Trichuris)
faecal-oral
symptoms of whipworm
asymptomatic, but if many worms cause blood diarrhoea, anaemia and inflammation of intestinal wall (-> rectal prolapse)
what can roundworms (filaria) cause
elephantiasis due to obstruction of lymphatics
2 types of roundworms
B. malayi, W. bancroft
diagnosis of lymphatic filariasis
blood smear or antigen detection for peripheral blood microfilariae (during night as in day present in deep veins)
treatment of lymphatic filariasis
albendazole
what causes eye worm (loaiasis)
Lao Lao
transmission of Loa Loa
fly vector and migrate through subcutaneous tissue, including under conjunctiva
flatworms (cestode) species
Taenia spp.
transmission of Taenia spp.
pig or cow
symptoms of Taenia
asymptomatic, but can cause digestive problems if large worm
diagnosis of Taenia
segment or eggs in stool
treatment of Taenia
paziquantel
what does Taenia solium cause
cysticercosis (causes acquired epilepsy)
example of fluke (trematode)
Schistosoma
Schistosomiasis transmission
requires water snail
symptoms of Schistosomiasis
rash, itchy skin, fever, chills, cough, muscle aches, inflammation, scarring, anaemia, malnutrition, organ damage
diagnosis of Schistosomiasis
stool/urine samples
treatment of Schistosomiasis
praziquantel
what are ectoparasites
parasites living on skin
examples of ectoparasites
scabies, headlice, body lice, pubic lice
transmission of scabies
direct contact
diagnosis of scabies
rash, burrows
treatment of scabies
sabicides
3 stages of louse life cycle
eggs, nymphs, adults
transmission of lice
direct contact
4 stages of life cycle of Leishmania protozoa endoparasites
inoculation, vertebrate host, ingestion, sandfly
2 forms of Lieshmania
promastigote, amastigote
Leishmania promastigotes
within sandfly vector, and can move in direction of flagellum
Leishmania amastigotes
within human and have reabsorbed flagellum, so no longer motile
distribution of sand flies
warm climates but due to global warming going further north
appearance and behaviour of sand flies
small, hairy, hop around, silent attack
why do only females feed on blood
for egg nutrition
4 major forms of leishmaniases
visceral (Kala-azar), cutaneous, diffuse, mucocutaneous/mucosal
symptoms of visceral leishmaniases (fatal if untreated)
irregular fever, weight loss, hepatosplenomegaly, anaemia
3 risk factors for visceral leishmaniases
malnutrition, immunosuppressives, HIV co-infections
diagnosis of visceral leishmaniases
case definition, laboratory investigations (parasite and antibody detection)
lesions in post Kala-azar dermal leishmaniases (PKDL)
lesions on face around mouth -> become nodular -> spread to trunk and limbs
symptoms of cutaneous leishmaniases
self-healing skin lesions on exposed body parts, creating serious disability and scars (immune to reinfection)
symptoms of diffuse cutaneous leishmaniases
disseminated lesions (resembles leprosy), difficult to treat, no spontaneous healing, frequent relapses
what happens in mucocutaneous/mucosal leishmaniases
destroys mucous membranes, causing disfigurement
healing and relapse in mucosal leishmaniases
no spontaneous healing, relapses
diagnosis of cutaneous leishmaniasis
microscopy/culture, skin test, serology, PCR
