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Clinical Pathology - > CP5 - Introduction to Parasites > Flashcards

CP5 - Introduction to Parasites Flashcards

1
Q

what is a parasite?

A

an organism which lives in or on another organism and benefits by deriving nutrients at the other’s expense. it does not necessarily cause disease

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2
Q

what is a host?

A

an organism which harbours the parasite

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3
Q

what is symbiosis?

A

close, long-term interaction between 2 different species

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4
Q

what is mutualism?

A

an association in which both species benefit from the interaction

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5
Q

what is parasitism?

A

an association in which the parasite derived benefit and the host gets nothing in return but always suffers some injury

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6
Q

what is commensalism?

A

an association in which the parasite is only deriving benefit without causing injury to the host

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7
Q

what are the 3 classes of hosts?

A
  1. definitive host
  2. intermediate host
  3. paratenic host
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8
Q

what is a definitive host?

A

a host that harbours either

  1. the adult stage of the parasite
  2. the parasite in the duration of its sexual reproduction
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9
Q

what is an intermediate host?

A

a host that harbours larval or asexual stages of the parasite. some require 2 intermediate hosts

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10
Q

what is a paratenic host?

A

where the parasite remains alive without any further development

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11
Q

what are the 2 broad classes of parasites?

A

protozoa (micro parasites) and helminths (macro parasites)

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12
Q

what are the types of protozoa?

A
  1. flagellates - guardia lambía
  2. amoeboids - entamoeba ep
  3. sporozoans
  4. trypanosomes
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13
Q

what are the types of helminths?

A 
platyhelminths (flat worms)
1. cestodes (tape worms)
2. trematodes (flukes)
nematodes (roundworms)
1. intestinal nematodes
2. tissue nematodes
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14
Q

what are the 3 types of life cycles of parasites?

A
  1. direct - only 1 definitive host
  2. simple indirect - 2 different hosts, 1 intermediate and 1 definitive
  3. complex indirect
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15
Q

which parasite causes ascariasis?

A

ascaris lumbricoides, an intestinal nematode

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16
Q

what is the distribution of ascaris lumbricoides?

A

areas of poor hygiene
3-8 year olds
contaminated soil, water or food
Central Asia and Africa

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17
Q

what is the lifecycle of ascaris lumbricoides?

A

direct.
ingested by humans, causes infection and reproduces
eggs passed in faeces
eggs ingested by humans

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18
Q

what is the clinical manifestation of ascaris lumbricoides?

A 
intestinal phase
1. malnutrition
2. intestinal obstruction
3. worm burden
4. migration to hepato-biliary tree and pancreas
lung migration causes loeffler's syndrome
dry cough
dyspnoea
wheeze
haemoptysis
eosinic pneumonitis
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19
Q

how is ascariasis diagnosed?

A

stool sample sent for testing, can either see eggs or the worm itself in the stool

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20
Q

what is the treatment for ascariasis

A

albendazole, a type of benzimidazole, which prevents the worm from absorbing glucose. the worm starves, detaches and is passed PR

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21
Q

how can the spread of ascariasis be controlled?

A

improve sanitation, education and community targeted deworming

22
Q

what organism causes schistosomiasis?

A

the genus schistosoma, a macro parasite (fluke)

23
Q

where can schistosoma be found?

A

fresh water places

South America, Asia

24
Q

which parts of the body do schistosoma affect?

A

some affect the liver, some affect the bladder, some affect both

25
Q

what is the life cycle of schistosoma?

A

simple indirect cycle
snails are intermediate hosts
eggs hatch in water and larvae enter snails, mature and leave
enter humans, mature into adults in liver, paired worms migrate to bladder
eggs are passed out

26
Q

what is the clinical manifestation of schistosomiasis?

A

swimmer’s itch
katayama fever
chronic schistosomiasis - eggs can affect the spine and lung
when the bladder is affected: haematuria, fibrosis and dysfunction, cancer
when liver is affected: hypertension, cirrhosis
eggs cause more problems than worms do

27
Q

how is schistosomiasis diagnosed?

A

urine sample - terminal stream
microscopy and serology to look for eggs
hepatic/intestinal - stool microscopy, renal snip microscopy, serology

28
Q

how is schistosomiasis treated?

A

praziquantel 40-60mg/kg with food every 8 hours
increases ionic permeability, titanic contraction
detachment and death
well absorbed and excreted in urine

this can be more complicated therefore important to treat long term complications

29
Q

how can schistosomiasis be controlled?

A 
chemical treatment to kill intermediate host snails
chemoprophylaxis
avoid snail infected waters
education
improved sanitation
30
Q

what is the distribution of echinococcus (tapeworm)?

A

all over the world where sheep are present

31
Q

what is the life cycle of echinococcus?

A

humans are accidental hosts. sheep and dogs are real hosts
egg penetrates sheep via ingestion of faeces (intermediate) causes cysts in organs
dogs (definitive) ingest infected organs, maturation, adult in small intestine. eggs passed in faeces. eggs can be accidentally ingested by humans, effective at the sub larval stage only

32
Q

what are the clinical manifestations of echinococcus?

A

70% liver cysts, 20% lungs, may be asymptomatic for years.
can lead to a secondary bacterial infection
cyst rupture causes hypersensitivity

33
Q

how is echinococcus infection diagnosed?

A

imaging

serology

34
Q

how can the spread of echinococcus be controlled?

A

worm eggs to reduce egg production
hand hygiene
safe disposal of animal carcasses/conception products

35
Q

which organism causes malaria?

A

plasmodium genus (sporozoan)

36
Q

what is the distribution of plasmodium?

A

south america
africa
asia

37
Q

what does echinococcus cause?

A

hydatid disease

38
Q

what type of a lifecycle does plasmodium have?

A 
complex indirect (ref to slide)
vector is anopheles mosquito
39
Q

what is the clinical manifestation of malaria?

A

parasites rupture RBCs, block capillaries and cause inflammatory reactions
fevers and riggers
cerebral malaria - confusion, headache, coma
renal failure - black water fever
hypoglycaemia
pulmonary oedema
circulatory collapse
anaemia, bleeding, disseminated intravascular coagulation (DIC)

40
Q

how is malaria diagnosed?

A

thick and thin microscopy
serology to detect antigen in blood
PCR to detect malarial DNA

41
Q

how can malaria be controlled?

A 
spray insecticide in homes
larvicidal spraying on breeding pools
filling in of breeding pools
introduction of larvivorous species 
insecticide impregnated bed nets
chemoprophylaxis
42
Q

which organism causes cryptosporidiosis?

A

cryptosporidium parvum and hominis (sporozoan)

43
Q

what is the distribution of cryptosporidium parvum?

A

worldwide, especially in tropical and temperate zones

44
Q

what is the life cycle of cryptosporidium parvum?

A

faecal-oral spread, human to human spread with cattle reservoir, eggs in faeces (in water)
people bathe in/drink contaminated water and are infected

45
Q

what is the clinical manifestation of cryptosporidiosis?

A 
watery diarrhoea with mucous (no blood)
bloating
cramps
fever
nausea and vomiting
usually self-limiting but can be very severe in very young or old and immunocompromised patients (eg. HIV)
46
Q

how is cryptosporidiosis diagnosed?

A

faeces sample - acid fast staining

antigen detection by EIA

47
Q

how is cryptosporidiosis treated?

A

incubation 2-10 days
for symptomatic patients - rehydration (nitrazoxanide)
for immunocompromised, additionally give paromomycin to kill parasite and octreotide to reduce cramps and frequency; initiate HAART for HIV patients

48
Q

how can the spread of cryptosporidiosis be controlled?

A 
hand hygiene
filter or boil drinking water 
isolate symptomatic patients
pasteurise dairy products
boil or filter drinking water
49
Q

what should be suspected if a patient presents with a history of recent travel and fever?

A

malaria until proven otherwise

50
Q

what are the common anti-protozoal treatments?

A
  1. metronidazole
  2. pentamidine
  3. nitrazoxanide
  4. pyrimethamine
  5. antimalarials for treatment and prophylaxis
51
Q

what are the common anti-helminthic treatments?

A
  1. albendazole
  2. mebendazole
  3. Ivermectin
  4. Praziquantel

Clinical Pathology - (15 decks)

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