Introduction to parasites Flashcards
define parasite
organism which lives on another and benefits by deriving nutrients at the others expense.
define host
organism which harbours the parasite
define symbiosis
Living together close, long term interaction between 2 different species.
define mutalism
association were both species benefit.
define parasitism
an association where the parasite derives benefit and the host gets nothing in return
define commensalism
an association in which the parasite only defining benefit without causing injury to the host.
what are 3 classes of host
definitive- sexual method of reproduction used
intermediate- asexual stages of parasite
paratenic-parasite remains without further development.
2 types of parasites
protazoa-micro
Helminths- macro, worms.
Types of protozoa
- Giardia lamblia- GI
- Cryptosporidum- GI
- Entamboea- GI
- Trypanosoma
Types of helminth
Cestode- taenia sp
Trematode- schistosoma
Intestinal nematode- Ascaris lumbricoides
Tissue nematode- Wuchereria bancrofti- lymphtic system disorder.
3 types of life cycle
- Direct
- Simple indirect
- Complex indirect
what type of parasite is ascariasis
macroparasite- intestinal nematode.
Where is ascariasis spread
poor hygiene areas
what age group does ascariasis affect
3-8 year olds
life cycle of ascariasis
- Worm in intestine lays eggs
- Lost in faeces
- Ingest eggs from contaminated food goes to intestines
- Migrate via portal circulation into lungs.
- Swallowed and passed back into the intestines- hatch and become worms.
2 phases of Ascariasis
Lung migration
Intestinal phase.
what is loefflers syndrome
part of the lung migration phase of ascariasis cycle.
dry cough, dyspnea, wheeze, haemoptysis. eosiniophillic pnemonititis.
how do you diagnose ascariasis
worm or eggs in stool, eggs at top and worms at bottom.
treatment for ascariasis
Albendazole, Benzimidazole
prevent glucose absorption by the worm.
what type of parasite is schistosomiasis
macroparasite- trematode.
what type of cancer can schistosomiasis cause
bladder cancer
What is the intermediate host of schistosomiasis.
snail
Life cycle of schistosomiasis
- In faeces and urine- relase egges as male and femal mate on bowel or bladder.
- Eggs hatch releasing miracidia
- Miracidia penetrate snail tissue
- Sporocysts in snail (successive generations)
- Cercariae released by snail into water and free swimming
- Penetrate human skin
- Cercariae lose tails in penetrtuation and become schistosomulae
- Circulayte in portal blood where they mature.
- Migrate to liver and mature in adults.
clinical problems related to schitosomiasis
swimmers itch- allergic reaction
Katayama fever- spreads into blood causing weight loss
chronic schistomosisasis
which 2 systems does schistosomiasis affect
urinary- haematauria, bladder fibrosis and bladder cancer
Hepatic- portal hypertension and liver cirrhosis.
How do you diagnose schistosomiasis
stool microscopy, rectal snip microscopy, serology
treatment for schistomoiasis
praziquantel.- 3 times a day with food.
What type of parasite is the hydatid parasite
macroparasite- cestode.
what are the typical hosts of hydatid parasite
sheep, dog
what is the accidental host of hydatid parasite
humans
Life cycle of the hydatid parasite
- Dog infected worm in intestines- release it in faeces
- Ingest eggs in contaminated food by humans- go into intestines + liver forming cysts.
- No worms/cysts are present in dogs as they need to eat the humans for this to occur.
- Only way they can ingest the cysts is if they are present in sheep and they eat the sheep.
clinical presentation of hydatid parasite
cysts- lungs and liver
secondary bacterial infection
cyst rupture- hypersensitivity, anaphylactic shock and death,
How do you diagnose Hyatid disease- diagnosis
CT
serology
What type of parasite is malaria.
• Micro-parasite (protozoa- sporozoan)
what are the different types of schistosoma
S. haematobium S. mansoni S. intercallatum S. japonicum S. mekongi
What are 4 types of plasmodium species
P. falciparum- causes cerebral malaria most clinically significant and causes life threatening symptoms.
P. vivax- can remain dormant in livre cells unlike falciparum.
P. ovale- can remain dormant in livre cells unlike falciparum
P. malariae
what is the vector in malaria
Anopheles mosquito.
life cycle of malaria
- Mosquito infected with parasite
- Infects parasite into RBC
- Sporazoa enter the liver.
- Sporazoa mitosis occurs
- Liver cells erupt
- Asexual phase-self replicate
- Sexual phase- transmission occurs, infected mosquito due to having a blood meal of infected human and then it passes it on to other human when it had another blood meal.
what condition does retiring traveller + fever indicate
malaria
clinical features of malaria.
fever and rigors,cerebral malaria- confusion, headache coma, renal failure, hypoglycaemia, pulmonary odema, circulatory collapse, anaemia, blleding DIC
how do we diagnose malaria.
- Thick and Thin Microscopy
- Serology- detection of antigen in blood
- PCR- detection of malarial DNA
treatment for malaria
antimalrial
Doxycycline
Mefloquine
Atovaquone plus proguanil
what type of parasite is cryptosporidiosis
microparasite
Cryptosporidium parvum and hominis
How is cyptosporisiodis spread
faecal oral route.
human to human
animal to human
Life cycle of cryptosporidiosis
- Direct life cycle
- Humans pass oocytes in stools
- Contaminate the water which we drink
- Ingest oocytes.
clinical features of cryptosporidiosis
- Incubation 2-10 days (usually 7 days)
- Watery diarrhoea with mucus (no blood)
- Bloating, cramps, fever, nausea, vomiting
- Usually self-limiting
how do we diagnose syprosporidiosis
• Faeces sample:
1. Acid fast staining
Antigen detection by EIA
Cyptosporidiosis treatment
symptomatic- rehydration and nitazoxanide
Immunocompromised- • Paromomycin (to kill parasite)
Nitazoxanide (effectiveness is unclear)
Octreotide (reduce cramps and frequency)
HIV patients, HAART should be quickly initiated
how many eggs can an adult worm produce
20,000
how to control levels of ascariasis
imporve sanitation, education, deworming.
how to control levels of schitosomiasis
- Chemical treatment to kill snail intermediate hosts
- Chemoprophylaxis- not very effective.
- Avoidance of snail infested waters
- Community targeted treatment, education and improved sanitation
How to control levels of hydratid
- Regularly worm dogs to reduce egg production
- Hand hygiene- not touching the dog and then eating.
- Safe disposal of animal carcasses/products of conception- stops dog eating the cysts in the first place.
How do we control levels of malaria
- Larvivorous species e.g. fungi, frogs or bacteria introduced in to mosquito breeding areas.
- Use of insecticide impregnated bed nets
- Chemoprophylaxis
- ??Vaccine??-
how to control levels of cryptosporidiosis
Human-Human:
• Hand hygiene
• Filter or boil drinking water (cf. chlorination)
• Isolate symptomatic patients in healthcare setting
• Ensure symptomatic children are kept away from school
Animal-Human:
• Pasteurise milk and dairy products
• Boil or filter drinking water if camping
