Protozoa and Helminths
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- Created by: amazingemilyjones
- Created on: 14-04-19 17:10
Protozoa and Helminths
Protozoa and Helminths
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Protozoa Properties
- Eukaryotic Microorganisms
- Generally unicellular
- Heterotrophic - needs organic substances
- Often commensal
- live in or on other organisms
- Sometimes parasitic - life stages
- Often live in aqueous environments
- often motile
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Malaria
- World Health Organisation priority disease
- WHO figures released in February 2018
- Estimated 216 million cases of malaria in 2016
- Estimated 445,000 deaths
- Africa region accounts for 91% of these deaths
- Children are more at risk
- Malaria mortality rates have fallen by 21% between 2010-2015, and by 31% in the WHO African Region
- Malaria - Plasmodium
- Plasmodium - ameboid intracellular parasites - P.vivax, P.falciparum, P.malariae
- Transmitted through bite of Anopheles mosquito
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P. vivax Life Cycle
Malaria - Prevention
- Mosquito control (insecticides, net, breading control)
- Prophylaxis - choice based on many factors
- risk of exposure
- extent of drug resistance
- efficacy of the recommended drugs
- side effects of the drugs
- patient-related factors (age, pregnancy, renal/hepatic impairment)
- Prophylaxis 1-3 weeks before travel to endemic areas
- Prophylaxis continues for up to 4 weeks after leaving endemic area
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Malaria - Prevention
- Chloroquine
- Prophylaxis not where falciparum malaria endemic (risk of resistance)
- Mefloquine
- Prophylaxis where falciparum malaria endemic
- Doxycycline (tetracycline)
- Prophylaxis where resistance to mefloquine and chloroquine
- Malarone
- Prophylaxis where falciparum malaria endemic including resistance to other antimalarial drug
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Malaria - Treatments
- Quinine
- Inhibits hemozoin biocrystallisation, which facilitates the aggregation of cytotoxic heme
- Malarone
- Interferes with two different pathways involved in biosynthesis of pyrimidines required for nucleic acid replication
- Cytosine (C), Thymine (T), Uracil (U), are pyrimidine derivative
- Atovaquone - inhibit electron transport chain
- Riamet (artemether with lumefantrine)
- Interferes with ability of malaria parasites to convert haem into haemozoin. This causes levels of the toxic haem to rise, which kills the bloos stages of the malaria parasites
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Cryptosporidiosis
- Organism
- Cryptosporidium parvum, hominis
- Both aerobic and anaerobic metabolisms
- Opportunistic infections
- Faecal-oral
- Water
- Symptoms
- Diarrhoea
- Abdominal pain
- Nausea
- Severe crystosporidiosis in HIV patients
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Cryptosporidiosis
Cryptosporidiosis
- Diagnosis
- Organism in stool sample
- Treatment
- Fluid and electrolyte replacement
- No licensed drugs in the UK
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Amoebic Dysentry (Amoebiasis)
- Organism
- Entamoeba histolytica
- Disease
- 400 million people infected worldwide
- 70000 deaths per year world wide
- Faecal-oral
- Water
- Diagnosis
- Organism in stool sample
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Amoebic Dysentry (Amoebiasis)
- Gastrointestinal infection that may or may not be symptomatic and can remain latent
- Range from mild diarrhoea to dysentry with blood and mucus in the stool
- Severe amoebiasis infections occur in two major forms:
- Invasion of the intestinal lining causes amoebic dysentry or amoebic colitis
- If the parasite reaches the bloodstream it can spread through the body, most frequently ending up in the liver where it causes amoebic liver abscesses
- Life cycle: ingestion, cysts rupture, release amoeboid trophozoites, feeds on bacteria, reproduce asexually in colon, cause ulceration, can enter blood vessels
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Amoebic Dysentry (Amoebiasis)
Amoebic Dysentry (Amoebiasis): Treatments
- Metrodinazole
- Prodrug
- Non-enzymatically reduced by reacting with reduced ferredoxin
- Many of the reduced nitroso intermediates will form sulfinamides and thioether linkages with cysteine-bearing enzymes
- Metronidazole metabolites are taken up into bacterial DNA and form unstable molecules
- Tinidazole
- Diloxanide fluorate
- Unlicensed
- Chronic amoebiasis
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Other Amoebal Diseases
- Leishmaniasis
- Giardiasis
- Trypanosomiasis (sleeping sickness; Chagas' Disease)
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Helminths: Parasitic Worms
- Flukes
- Tapeworms
- Roundworms
- Threadworms
- Hookworms
- Whipworms
- One billion people develop intestinal worm diseases globally every year
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Diseases and Routes of Infections
- Causes a wide range of infections
- Schistosomiasis (bilharzia)
- Cysticercosis
- Lymphatic filariasis (elephantiasis)
- Onchocerciasis (river blindness)
- Transmission routes
- Schistosome or hookworm larvae directly penetrate the skin from infected water or soil
- Filarial worms, such as Onchocerca, are transmitted by insect vectors
- Inadequate sanitation is a major infection. Poverty and helminth infections are inextricably linked
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Symptoms
- Stomach upset (abdominal pain, nausea or vomiting)
- asymptomatic (a few roundworms)
- reduced nutritional uptake
- intestinal obstruction or bleeding
- rectal prolapse
- presence of a worm within vomit or stools
- Flu-like symptoms
- include fatigue or fever
- anaemia
- Skin rash
- Breathing difficulties
- if lungs infected
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Treatments - Anthelmintics
- Depends on the worm
- Mebendazole
- Threadworm, roundworm (ascaris), whipworm infections
- Inhibits the synthesis of microtubules, glucose uptake
- Praziquantel
- Tapeworm, whipworm, roundworm infections
- Increases the permeability of the membranes of schistosome cells towards calcium ions, paralysing the parasite
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Treatments - Anthelmintics
- Niclosamide
- Taenicides (tapeworm infections) - unlicensed
- Uncouples oxidative phosphorylation in the tapeworm
- Ivermectin
- Filaricide (named-patient basis) - unlicensed
- GABA receptor, glutamate-gated chloride channels
- Diethylcarbamazine
- Filaricide (named-patient basis) - unlicensed
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