MICRO: Parasitic Infections

Question 1

2 types of parasites

Answer 1

• protozoa: unicellular eukaryotes
• helminths (worms): multicellular eukaryotes

Question 2

examples of protozoa

Answer 2

• malaria
• trichomonas
• toxoplasmosis
• giardia

Question 3

malaria: pathogen, transmission, Sx, complications

Answer 3

• caused by 5 diff plasmodium species (protozoa) e.g. P. falciparum (main) and vivax which obstructs capillaries
• transmitted by mosquitoes
• Sx: fever, coldness, sweating
• latent infection has no Sx but then turns into a massive blood borne infection
• doesn’t cross placenta and not contagious
• complications: anaemia, hypoglycaemia, jaundice, kidney injury, pregnancy issues etc

Question 4

how to Dx malaria

Answer 4

• check if they have returned from an endemic region
• if suspect malaria: PCR to detect parasite DNA or RAT test for antigens - but need to confirm w/ Giemsa
• blood microscopy > smear (Giemsa)

Question 5

malaria Tx and prevention

Answer 5

• Tx: combination therapies due to resistance
• prevention: residual spraying, prophylaxis, cover up w/ clothes, mosquito repellent, stay inside @ night
• “fever in a returned traveller is MALARIA until proven otherwise”

Question 6

trichomonas vaginalis: what is it, Sx, complications

Answer 6

• parasitic STD in prostate, urethra, vagina
• men largely asymptomatic
• women (if symptomatic): smelly discharge, dysuria, dyspareunia
• complications: can predispose to other STDs

Question 7

Dx for trichomonas vaginalis

Answer 7

• Dx: microscopy - direct wet mount of urine (men) or vaginal fluid (women), RAT or PCR if no parasites can be seen by microscopy

Question 8

what is Toxoplasma gondii and how is it transmitted

Answer 8

• zoonosis from cats: replicate in GIT and oocysts (egg cysts) spread from faeces
• transmission: transplacental, ingestion of undercooked meat, ingestion of cat faeces e.g. contaminated food, sandpits, gardening

Question 9

Toxoplasma gondii Sx in healthy ppl

Answer 9

• acute, systemic inflammatory response, flu-like
• swollen lymph nodes, myalgia
• danger: may spread to CNS and GIT

Question 10

Toxoplasma gondii Sx in immunocompromised ppl

Answer 10

• much more severe: systemic organ damage
• pregnant women: may lead to foetal abnormalities

Question 11

Dx of toxoplasma gondii

Answer 11

• serology, histology, radiology
• PCR of CSF and amniotic fluid

Question 12

what is Giardia and how is it transmitted

Answer 12

• GIT parasite (flagellated protozoa)
• only infects humans
• has sucker discs/feeding groove
• transmitted thru ingesting cysts from contaminated water, spread thru faeces

Question 13

Sx and Dx of Giardia

Answer 13

• Sx: abdominal pain, bloating, flatulence, nausea, watery + greasy stools (steatorrhoea)
• Dx: microscopy, stool examination, PCR

Question 14

how to prevent Giardia

Answer 14

• avoid water that may be contaminated
• good hygiene
• boil water or use a filter

Question 15

2 types of worms

Answer 15

• nematodes (round worms): hookworms, filariasis, pin/threadworms
• platyhelminths (flatworms): cestodes/tapeworms, trematodes (flukes)

Question 16

cestodes/tapeworms

Answer 16

• flatworm (platyhelminth)
• often found in meat: binds to GIT via scolex (head)
• generally mild symptoms
• usually found when Pt notices segments in faeces

Question 17

trematodes (flukes): complications, transmission + Dx

Answer 17

• flatworm (platyhelminth) which causes schistosomiasis
• can block liver, lungs, blood, intestines
• snail host releases larvae which can penetrate intact skin
• Dx: eggs in stool/urine, serology

Question 18

hookworms: transmission, Sx and Dx

Answer 18

• soil transmitted roundworm (nematode)
• larvae penetrate skin thru feet > hook onto GIT for blood feeding
• Sx: commonest cause of iron deficiency anaemia, N&V
• Dx: wet mount - eggs in stool

Question 19

filariasis: transmission + Sx

Answer 19

• transmitted by mosquito bite which causes skin wound > larvae enter skin and live in lymphatics and enter bloodstream at NIGHT
• gradual onset of Sx: lymphadenitis, oedema (elephantiasis), gradual impairment of lymphatics > can cause permanent disability

Question 20

Dx and prevention of filariasis

Answer 20

• Dx: Giemsa, serology, PCR
• prevention: avoid mosquito bites, mass community Tx

Question 21

pinworms: transmission, Sx, Dx

Answer 21

• most common worm infection in developed countries (children > families)
• worms live in caecum and migrate out of anus @ night to lay eggs
• Sx: persistent anal itching
• Dx: put tape over in morning and peel off to see eggs, can sometimes see worms in faeces