Parasites Study Guides

Protozoa: Unicellular eukaryotes with lack of cell wall and live in moist habitats. They are mainly reproduced by asexual binary fission. 2 forms in their life cycle trophozite(actively feeding) or cyst(thick, protective membrane) The classification of this is based on: motility i.e. flagellates, ciliates (vibrates), sporozoates (non-motile), sacrdines/ pseudopodia (stretches) Route of infection i.e. visceral (amoebiasis etc), blood and tissue (malaria) Sarcodines: -acanthamoeba keratitis Ubiquitous in aquatic environment. Contact lenses provide ideal attachment surfaces and enable corneal adherence. Keratitis(non-bacterial) Acanthamoeba cells often infected by other pathogens i.e. bacteria and viruses but many are resistant against anti-protozoal drugs and disinfection, with the most effective drug being biguanides Entamooeba histolytica: Anaerobic, waterborne pathogen which invades intestinal epithelium causing ulcers leading to cramps and diarrhoea i.e. amoebiasis Associated with travellers diarrhoea, cells detectable in stool sample Further growth invading intestinal wall amoebic dysentery- intestinal inflammation passage of blood & mucus, fever, anaemia and if left untreated abscesses may form and be fatal Flagellates: Giardia intestinalis/ lamblia: Flagellates and microaerophilic which live in intestines of beavers & muskrats. This is transmitted to humans by faecal contamination of water sources, the ingested cysts germinate into trophozoites in the colon. Giardiasis-explosive diarrhoea, intestinal cramps, flatulence, nausea, weight loss Prevention can include clarification, chlorination and filtration of water and treatment can include quinacrine, furazolidone and metronidazole Trichomonas vaginalis: Flagellates & anaerobic sexually transmitted disease which have no cyst form. This resides in the urethra, vagina, prostate and seminal vesicles. In females, there is a yellowish discharge with itching and burning and it is the most common but curable STD using metronidazole Leishmania: Flagellated and aerobic with a sand fly vector I.e. cutaneous leishmaniasis, visceral leishmaniasis Symptoms include cutaneous parasites grown within macrophage small nodule, ulcerous skin lesions & pigment scars, visceral parasites infect liver, spleen & bone marrow causing fever-chill cycle, slow decline of red & white blood cells, enlargement of liver and spleen and can be fatal if left untreated Treatments include antimonial drugs intravenous or intramuscular as inhibition of proteins are involved in the virulence Trypanosoma: African(sleeping disease) and american(chagas disease) Sleeping disease: Infection of the CNS, tryptophan triggers sleep responses. T. Brusei gambiense uses the tsete fly as a vector or the glossina palpalis, prevalent in west and central Africa. T. Brusei rhodesiense uses a vector of tsetse fly or the glossina morsitans, prevalent in the savannah plains of east Africa. Chagas’ disease: Mild, acute phase, chronic illnesses which may lead to heart failure T. Cruzi uses a vector of reduviid bug or the triatoma infestans, prevalent in South America. Ciliates: Balantidium coli: A ciliates and human swine pathogen, in humans as the only known ciliates parasite in which only the cysts are infective. They resemble amoebiasis in terms of waterborne transmissions as well as symptoms. However, B. Coli infections are rare and mild Sporozoates: Plasmodium: Microaerophilic i.e. malaria caused by p. Vivax as the most common but p. Falciparum as the most serious. The malarial life cycles occurs half in humans and half in female anopheles Many factors such as optimal growth temp of anopheles & optimal temp for parasites to complete the growth cycle in mosquitos determine prevalence Malarial life cycle: Plasmodia lives in salivary gland of Anopheles in sporozoite form, 2. Sporozoites transferred to human during feeding; 3. Sporozoites travel to liver and infect liver cells; 4. Sporozoites become enlarged and enter schizont stage; 5. Schizonts splits into merozoites and enter erythrocytes; 6. Merozoites develop into gametocytes; 7. Gametocytes infect Anopheles during feeding and mature into gametes; 8. Two gametes fuse into zygote and moves to outer wall of intestine; 9. Zygote enlarges into sporozoites; 10. Sporozoites released into salivary gland. Symptoms of malaria may happen in 48hr intervals. In the erythrocytes stage of cell division, release and growth of the merozoites: Chill fever, vomiting, severe headache, periodically asymptomatic, anaemia, spleen enlargement, fatigue Relapses may occur due to hypnozoite the dorrmant form of p. Ovale and p. Vivax in the liver Diagnosis: Clinical, using wright-giemsa stained smear as differential stain containing mix of azure, methylene blue and eosin, Differentiated nuclear & cytoplasm of blood cells, Gold standard for malaria plasmodium detection -antigen detection test, secondary to giemsa smear test Taxoplasma Gondii: May cause infection of all warm blooded animals but have a requirement of cats to complete the life cycle- obligate intracellular parasite Cysts germinate in the small intestine penetrating the wall and circulating, toxoplasmosis occurs i.e. headache, muscle ache and can also effect the brain and nerves Around1/3 world is affected but asymptomatic Birth defects may be caused with first time infection in mothers leading to congenital infection Toxoplasmosis encephalitis major cause of morbidity and mortality in HIV patients Cryptosporidium par I’m: A waterborne pathogen and animal faeces contaminated water A thick walled cyst or an oocyst that is highly chlorine resistant. A stool sample can be used as a diagnostic marker Cryptosporidiosis: mild gastroenteritis common in UK and USA and is the leading cause of paediatric diarrhoea with 20% cases linked to travellers diarrhoea Cyclospora cayetanensis: A food borne pathogen and through animal faeces contaminated food This is highly resistant thick walled oocyst Cyclosporiasis: severe gastroenteritis, has caused several outbreaks through prepackaged vegetables in the USA Helminths, parasitic worms: Helminths: Hermaphroditic and bisexual, classified as microbes due to microscopic eggs and larvae Major groups include: tapeworm(Cestode), roundworm (nematode), flatworm (Platyhelminthes) Schistosoma Mansoni: Trematode/ flatworm Life cycle requiring both snails and mammals and the second most common parasitic infection after malaria Transmission to humans miracidia in fresh water reservoirs infect snails, transforming into motile cercaria released and enter into human skin causing long term systemic infections such as snail fever or schistosomiasis Diagnosis can be established by swollen abdomen due to accumulation of organ fluids and eggs and also presence of eggs in urine and faeces This is treated by praziquantel Taenia solium and t. Saginata: Cestode or tapeworm Transmitted via poorly cooked meat, humans are the only hos. The cysticerci or larvae cannot survive temps below 10 or above 50 T. Solium- live in pork, grow up to 7m with pear shaped head T. Saginata- live in beef, grow up to 25m with globular head Transmission to humans upon the consumption larvae attach to small intestine causing epigastric pain, diarrhoea and vomiting or taeniasis T.solium cysts reach the lungs, liver, eye, brain and cause impairments such as in the vision or neurological symptoms or cysticercosis Treatment includes praziquantel/ niclosamide and expulsion to remove the head or scolex Wuchereria Bancrofti: Nematode or roundworm Transmission to humans via mosquitos carrying microfilariae, adult worms distrust hosts lymph flow, oedema of lower extremities or elephantiasis/ bancrofts filariasis. Carries endosymbiosis bacteria or wolbachia and treatment of antihelminthic containing antibacterial Plasmodium Vivax features of microorganisms Size Overall morphology Genome Tropism Family Parasite and human pathogen Round to oval and may almost fill the red blood cell so up to 5000 nm Infected large erythrocytes that appear like granules over them 3 genomes of nuclear, mitochondrial and apicoplast genome which is Apicoplast-organelle with circular genome carrying genes of functional importance may be used as drug targets Invading reticulocytes restricted the youngest red blood cells Plasmodiida