CP5 - Introduction to Parasites

Question 1

what is a parasite?

Answer 1

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

Question 2

what is a host?

Answer 2

an organism which harbours the parasite

Question 3

what is symbiosis?

Answer 3

close, long-term interaction between 2 different species

Question 4

what is mutualism?

Answer 4

an association in which both species benefit from the interaction

Question 5

what is parasitism?

Answer 5

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

Question 6

what is commensalism?

Answer 6

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

Question 7

what are the 3 classes of hosts?

Answer 7

1. definitive host
2. intermediate host
3. paratenic host

Question 8

what is a definitive host?

Answer 8

a host that harbours either

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

Question 9

what is an intermediate host?

Answer 9

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

Question 10

what is a paratenic host?

Answer 10

where the parasite remains alive without any further development

Question 11

what are the 2 broad classes of parasites?

Answer 11

protozoa (micro parasites) and helminths (macro parasites)

Question 12

what are the types of protozoa?

Answer 12

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

Question 13

what are the types of helminths?

Answer 13

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

Question 14

what are the 3 types of life cycles of parasites?

Answer 14

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

Question 15

which parasite causes ascariasis?

Answer 15

ascaris lumbricoides, an intestinal nematode

Question 16

what is the distribution of ascaris lumbricoides?

Answer 16

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

Question 17

what is the lifecycle of ascaris lumbricoides?

Answer 17

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

Question 18

what is the clinical manifestation of ascaris lumbricoides?

Answer 18

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

Question 19

how is ascariasis diagnosed?

Answer 19

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

Question 20

what is the treatment for ascariasis

Answer 20

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

Question 21

how can the spread of ascariasis be controlled?

Answer 21

improve sanitation, education and community targeted deworming

Question 22

what organism causes schistosomiasis?

Answer 22

the genus schistosoma, a macro parasite (fluke)

Question 23

where can schistosoma be found?

Answer 23

fresh water places

South America, Asia

Question 24

which parts of the body do schistosoma affect?

Answer 24

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

Question 25

what is the life cycle of schistosoma?

Answer 25

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

Question 26

what is the clinical manifestation of schistosomiasis?

Answer 26

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

Question 27

how is schistosomiasis diagnosed?

Answer 27

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

Question 28

how is schistosomiasis treated?

Answer 28

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

Question 29

how can schistosomiasis be controlled?

Answer 29

``` chemical treatment to kill intermediate host snails chemoprophylaxis avoid snail infected waters education improved sanitation ```

Question 30

what is the distribution of echinococcus (tapeworm)?

Answer 30

all over the world where sheep are present

Question 31

what is the life cycle of echinococcus?

Answer 31

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

Question 32

what are the clinical manifestations of echinococcus?

Answer 32

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

Question 33

how is echinococcus infection diagnosed?

Answer 33

imaging | serology

Question 34

how can the spread of echinococcus be controlled?

Answer 34

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

Question 35

which organism causes malaria?

Answer 35

plasmodium genus (sporozoan)

Question 36

what is the distribution of plasmodium?

Answer 36

south america africa asia

Question 37

what does echinococcus cause?

Answer 37

hydatid disease

Question 38

what type of a lifecycle does plasmodium have?

Answer 38

``` complex indirect (ref to slide) vector is anopheles mosquito ```

Question 39

what is the clinical manifestation of malaria?

Answer 39

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)

Question 40

how is malaria diagnosed?

Answer 40

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

Question 41

how can malaria be controlled?

Answer 41

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

Question 42

which organism causes cryptosporidiosis?

Answer 42

cryptosporidium parvum and hominis (sporozoan)

Question 43

what is the distribution of cryptosporidium parvum?

Answer 43

worldwide, especially in tropical and temperate zones

Question 44

what is the life cycle of cryptosporidium parvum?

Answer 44

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

Question 45

what is the clinical manifestation of cryptosporidiosis?

Answer 45

``` 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) ```

Question 46

how is cryptosporidiosis diagnosed?

Answer 46

faeces sample - acid fast staining | antigen detection by EIA

Question 47

how is cryptosporidiosis treated?

Answer 47

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

Question 48

how can the spread of cryptosporidiosis be controlled?

Answer 48

``` hand hygiene filter or boil drinking water isolate symptomatic patients pasteurise dairy products boil or filter drinking water ```

Question 49

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

Answer 49

malaria until proven otherwise

Question 50

what are the common anti-protozoal treatments?

Answer 50

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

Question 51

what are the common anti-helminthic treatments?

Answer 51

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