Parasites intro Flashcards

1
Q

What is a parasite?

A
  • An organism which lives in/on another organism (host) & benefits by deriving nutrients
  • Doesn’t necessarily cause disease
  • Parasite derives all benefits from the association & the host may either be harmed or suffer the consequences of this association
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2
Q

Define the term host

A

-An organism which harbours the parasite

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3
Q

Define the term symbiosis and mutualism

A

S=Living together, long term interaction between 2 different species
M= Association in which both species benefit from interaction

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4
Q

Define parasitism & commensalism

A

P=Association in which the parasite derives benefit & host gets nothing but suffers some injury
C=Association in which the parasite only is deriving benefit without causing injury to host

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5
Q

What are the different classes of hosts?

A
  • Definitive host: Harbours the adult stage of the parasite/ parasite utilises the sexual method of reproduction, majority of human parasitic infections
  • Intermediate host: Harbours larval/asexual stages of parasite, some parasites require 2 intermediate hosts
  • Paratenic host: Parasite remains viable without further development
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6
Q

What are the 2 categories parasites are classified into?

A
  • Protozoa (micro-parasites)

- Helminths (macro-parasites)

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7
Q

What are the different classes of Protozoa? Give examples of each

A
  • Flagellates (Giardia Lamblia)
  • Amoeboids (Entamoeba, Acanthamoeba)
  • Sporozoans (Plasmodium, Cryptosporidium, Cyclospora, Isospora, Toxoplasma)
  • Trypanosomes (Trypanosoma, Leishmania)
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8
Q

What are the different classes of Helminths? What can these be subdivided into?

A
  • Platyhelminths= Cestodes (tape worms), Trematodes (flukes)

- nematodes= Tissue nematodes, Intestinal nematodes

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9
Q

What types of life cycles are there for a parasite? Describe them

A
  • Direct (droppings containing eggs which become infected and eaten by an organism)
  • Simple indirect (droppings containing eggs, organism eats eggs in which eggs hatch another organism eats this organism and becomes infected)
  • Complex indirect (droppings containing eggs are then eaten by 2 intermediate hosts which is then eaten by end organism)
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10
Q

What is Ascariasis?

A
  • Macroparasite- intestinal nematode (Ascaris Lumbricoides)
  • Peak prevalence 2-8yrs
  • Areas of poor hygiene
  • Acquired by ingestion off eggs
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11
Q

What are the clinical implications of Ascariasis?

A
  • Lung migration= Loefflers syndrome: dry cough, dyspnea, wheeze, haemoptsis, eosinophilic pneumonitis
  • Intestinal phase= malnutrition, migration into hepatobiliary tree & pancreas, intestinal obstruction by worm
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12
Q

How is Ascariasis treated or controlled?

A
Treatment= Albendazole prevents glucose absorption by worm which starves and detaches passed PR
Control= improve sanitation, education, community targeted deworming, WHO action against worms
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13
Q

What is Schistosomiasis?

A
  • Macroparasite (fluke Schistosoma)
  • Bilharzia disease
  • Causes chronic disease-bladder cancer & liver cirrhosis
  • Intermediate host is snails
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14
Q

What are the clinical implications of Schistosomiasis?

A
  • Swimmers itch at site of parasite entry
  • Katayama fever
  • Chronic Schistosomiasis
  • Effects of eggs in spine & lungs
  • Urinary: haematuria, bladder fibrosis/dysfunction, squamous cell CA bladder
  • Hepatic/intestinal: portal hypertension, liver cirrhosis
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15
Q

How is Schistosomiasis treated and controlled?

A
  • Praziquantel leads to ionic permeability titanic contraction, detachment and death
  • Treatment of long term complications also required
  • Chemical treatment to kill snails/avoid snail infested waters
  • Chemoprophylaxis
  • Community targeted treatment, education, improved sanitation
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16
Q

What is Hydatid disease?

A
  • Macroparasite (Tapeworm)
  • Human accidental host
  • Usual host= dogs/sheep
  • Caused by Echinococcus
17
Q

What are the clinical implications of Hydatid disease?

A
  • Cysts 70%=liver 20%=lungs
  • May remain asymptomatic for years
  • Mass effect
  • Secondary bacterial infection
  • Cyst rupture=hypersensitivity
18
Q

How is Hydatid disease controlled?

A
  • Regular worming of dogs to reduce egg production
  • Hand hygiene
  • Safe disposal of animal carcasses
19
Q

What is Malaria?

A
  • Microparasite (Sporozoan)
  • 4 species of plasmodium
  • Anopheles acts as a vector
20
Q

What are the clinical implications of malaria?

A
  • Parasites rupture red blood cells, block capillaries & cause inflammatory reaction
  • Fever & rigors
  • Cerebral malaria (confusion, headache, coma)
  • Renal failure (black water fever)
  • Hypoglycaemia
  • Pulmonary oedema
  • Circulatory collapse
  • Anaemia, bleeding
21
Q

How is Malaria controlled?

A
  • Insecticide spraying in homes
  • Filling in breeding pools
  • Larvicidal spraying of breeding pools
  • Mosquito nets
22
Q

What is Cryptosporidiosis>

A
  • Caused by Cryptosporidium parvum
  • Causes diarrhoea disease
  • Human to human spread with animal reservoir
  • Faecal-oral spread
  • Sporadic cases/ lead to outbreaks
23
Q

What are the clinical implications of Cryptosporidiosis?

A
  • Incubation 2-10days
  • Watery diarrhoae w/mucus (no blood)
  • Bloating, cramps, fever, nausea, vomiting
  • Usually self-limiting
  • Severe in very young/old, immune-compromised/HIV patients
24
Q

Who are at risk of Cryptosporidiosis>

A
  • H to H: regular users of swimming pools, child care workers/parents, nursing home residents/carers, travellers, HCA
  • A-H: Backpackers/campers/hikers, farm workers, visitors to farms/petting zoos, consumers of infected dairy products
25
Q

What is the treatment & control for Cryptosporidiosis?

A

-Symptomatic: Rehydration, Nitazoxanide
-Immunocompromised: Paromomycin-kills parasite, , HAART- HIV patients, Octreotide (reduce cramps & frequency)
H to H: hand hygiene, filter/boil drinking water, isolate symptomatic patients
A to H: pasteurise milk/dairy products

26
Q

What are commonly used anti-protozoal treatments?

A
  • Metronidazole
  • Pentamidine
  • Anti-malarials
  • Nitazoxanide
  • Pyrimethamine
27
Q

What are commonly used anti-helminthic treatments?

A
  • Albendazole
  • Mebendazole
  • Ivermectin
  • Praziquantel