Core Microbiology - Introduction to Parasites (4) Flashcards
Parasite
- Organism that lives in/on another organism (its host) and benefits by deriving nutrients at other’s expense
- Habitually relies on/exploits others and gives nothing in return
- Doesn’t necessarily cause disease
- Host may be harmed/suffer consequences of this association
Host
An organism which harbours the parasite
Symbiosis
Living together, close, long term interaction between two different species
Mutualism
An associated in which both species benefit from the interaction
Parasitism
An association in which the parasite derives benefit and the host gets nothing in return but suffers injury
Commensalism
An association in which the parasite only is deriving benefit without causing injury to the host
Definitive host
Harbours adult stage of parasite, where parasite utilises the sexual method of reproduction, usually human
Intermediate host
Harbours the larval/asexual stages, some parasites have 2
Paratenic host
Host where parasite remains viable without further development
How to approach parasites
- Distribution (where find them?)
- Life Cycle (how survive+breed)
- Clinical Manifestations
- Diagnosis
- Treatment
- Control (prevent others)
Direct life cycle
1 host
Simple/complex indirect
2 hosts
Classification of parasites
Protozoa (micro-parasites) and Helminths (marco-parasites)
Cestode
Taenia/tape worm
Tretmatode
Schistosoma/fluke
Intestinal nematode
Ascaris lumbricoides - largest most common worm
Tissue nematode
Wuchereria bancrofti
Ascariasis
Macroparasite, intestinal nematode, Ascaris lumbricoides, round worm
Ascariasis epidemiology
1/7 world population, common China
Ascariasis prevalence
3-8 years old
Ascariasis transmission
Ingestion of eggs > lava pass into intestines > portal circulation > lungs (alveolar) > swallowed > intestines
Ascariasis Lung migration
Loefflers syndrome - dry cough, dyspnea, wheeze, haemoptysis, eosinophilic pneumonitis
Ascariasis intestinal phase
Malnutrition, migration, intestinal obstruction, worm burden
Raised ?? commin in helminth infection
Eosinophils
Ascariasis diagnosis
Stool/blood sample, X-ray, USS, CTI/MRI
Ascariasis treatment
Albendazole - Benzimidazole (prevents glucose absorption by worm)
Ascariasis control
Improve sanitation, education, deworming
Schistosmiasis
Macro-parasite, Trematode/fluke, Bilharzia disease
Schistosmiasis epidemiology
200 million, around freshwater lakes (Africa)
Schistosmiasis caused by
Schistosoma/snails: S.haematobium, S.mansoni, S.intercallatum, S.japonicum, S.mekongi
Schistosmiasis complications
Causes chronic renal disease > bladder cancer and liver cirrhosis
Schistosmiasis life cycle
Male and female mate in bowel > produce eggs > released in faeces/urine > develop/hatch > eaten by snail > reproduce > penetrates skin of humans
Schistosmiasis Swimmers itch
Lasts few weeks, pain and itching at site (allergic reaction)
Schistosmiasis Katayama fever
General malaise, fever
Chronic Schistosmiasis presentation
Persist for years, distended stomach effects of eggs in distant sites - spine and lung
Urinary complications of Schistosmiasis (S. haematobium)
Haematuria, bladder fibrosis and dysfunction, squamous cell bladder cancer (due to eggs)
Hepatic/intestinal Schistosmiasis
(S. mansoni, S. intercallatum, S. japonicum, S.mekongi) Portal hypertension, liver cirrhosis
Schistosmiasis urinary diagnosis
Terminal stream microscopy and serology
Schistosmiasis hepatic/intestinal diagnosis
Stool microscopy, rectal snip microscopy, serology
Schistosmiasis treatment
Praziquantel (increased ionic permability tetanic contraction, detachment and death)
Hydatid disease
Macro-parasite - Cestode/tapeworm
Hydatid disease host
Sheep and dogs, human accidental host
Hydatid disease caused by
Echinococcus (E. granulosus - cystic and E.multilocularis - alveolar)
Hydatid disease lifecycle
Liver > lungs > form hydatid cysts
Hydatid disease clinical
Cysts liver and lung, asymptomatic for years, mass effect, secondary bact infection, cyst rupture > shock and death
Hydatid disease diagnosis
Imagining and serology
Hydatid disease control
Regularly worm dogs (reduce eggs), hand hygiene, safe disposal of animal carcasses
Malaria
Micro-parasite, protoza, sporozoan
4 species of Malaria (Plasmodium)
- P. falciparum
- P. vivax
- P.ovale
- P.malariae
Which species of malaria is most clinically significant?
P. falciparum (most severe infections > death)
Malaria epidemiology
300-500 million people/year, 1-3 million deaths/year
Malaria life cycle
Anopheles as a vector, injects parasite into RBC, sporozites enter liver, replicates until cells so heavy they rupture, asexual phase
Malaria clinical
Parasites ruputure RBC > block capillaries and cause inflammation, fevers and rigors (alternate days), cerebral malaria (confusion, headache, coma), renal failure (black water fever), hypoglycaemia, pulmonary oedema, circulatory collapse, anaemia, bleeding and DIC
Malaria diagnosis
Thick and thin microscopy, serology (antigen), PCR (malarial DNA)
Malaria control
Insecticide spraying, larvicidal spraying, filling in of breeding pools
Crypotsporidiosis
Micro-parasite, Cryptosporidium parvum and hominis, sporozoan
Crypotsporidiosis transmission
human - human with animal resevoir (cattle, sheep, goats), faecal-oral
Crypotsporidiosis lifecycle
Direct, oocysts passed in stools contaminating water
Crypotsporidiosis incubation
2-10 days
Crypotsporidiosis clinical
Watery diarrhoea with mucus, bloating, cramps, fever, nausea, vomiting
Crypotsporidiosis severity
Self-limiting, severe - young, old and immunocompromised (HIV)
Crypotsporidiosis diagnosis
Faeces sample - acid fast staining, antigen detection by EIA
Crypotsporidiosis treatment
Rehydration, Nitazoxainde (Immunocompromised - paromomycin)
Common anti-protozoal treatment
Metronidazole, Pentamidine, Nitazoxanide, Pyrimethamine, Anti malarials
Common anti-helminthic treatment
Albendazole, Mebendazole, Ivermectin, Praziquantel
