Intro to Parasites Flashcards
Define a parasite
An organisms that lives in another organism (host) and gets its food at expense of the host
Parasitic infection
Cause burden of disease in both the tropics and subtropics as well in the temperature climate
What are the three mains types of parasites?
- protozoa
- helminths (worms)
- arthropods
Describe protozoa parasites and give three examples
One-celled organisms able to amplify in humans.
- Malaria
- Amoebae
- Flagellates
How are protozoa transmitted?
- Fecal-oral route: if they live human’s intestine
- Arthropod vector: if they lie in the blood or tissue in human’s
What parasite causes malaria?
Plasmodium falciparum
Characteristics of malaria
-fever, chills, flu-like symptoms
Life cycle of malaria
- sporozoites injected under skin by mosquito
- Travel through blood to liver
- Mature in liver and enter blood as merozoites
- Invades red cells, multiply and lyse leading to more invasion
- Sexual forms taken up by mosquito and others infected
Methods of malaria control
- Insecticide treated mosquito nets (ITNs)
- prophylaxis
What parasite causes Amoebic Dysentery?
Entamoaeba histolytica
Life cycle of amoebic dysentery
Trophozite ingests red cells by throwing out pseudopodia
Clinical features in Amoebic Dysentery
cysts in stool and liver abscesses
What parasite causes Leishmaniasis (flagellate)?
Bite from sand flies which carry Leishmania spp.
Clinical features in Leishmaniasis (flagellate)
Cutaneous or muco-cutaneous leishmaniasis - mucosal ulceration
Visceral leishmaniasis - fever, weight loss, hepatic-splenomegaly
Three main types of Helminths (worms)
- Nematodes (round worms)
- Cestodes (tapeworms)
- Trematodes (flatworms)
Diagnosing Leishmaniasis
Histology of biopsy
Diagnosing Nematodes
‘Sellotape test’ - press selo tape to perianal region and looking at it through microscope and matching it to town parasite
Life cycle of Acaris Lumbricoides (nematode)
- ingested eggs hatch in intestine
- larvae carried by circulation to lungs
- swallowed again
Adult worms develop and inhabit small intestine- ova seen in faeces by microscopy
Two types of Cestodes
- Taenia Saginata (beef)
- Taenia Solium (pork)
Life cycle of T-solium (Cestode)
- Larval cysts ingested in meat (intermediate host)
- Adult tapeworm (definitive host)
- Tissue cysts in humans infected T. solium - ‘cysticercosis’
Life cycle of Echinococcus spp. (Cestode)
- human ingest eggs (dog faeces)
- eggs hatch and enter circulation
- Hydatid cyst forms in liver
- Surgical resection must be of whole cyst
What are trematodes schistosoma?
Type of trematode referred to as flukes
Three species of Schistosomes
- S. haematobium (bladder) - bladder cancer
- S. mansoni (intestinal)
- S. japonicum (intestinal)
Life cycle of schistosomes
- eggs excreted in urine/faeces
- Miracidia - fluke travels from first host (faeces) to body of snail through water (intermediate host)
- Cercaria emerge from snail 4-6 wks
- Penetrate human skin and travels to liver
- Mature into worms (schistosomes) that migrate to bladder venue
- Lay eggs that cause inflammation in bladder or intestinal wall
Clinical feature of schistosomiasis
- Mature in liver into worms (schistosomes) that migrate to bladder venue
- Lay eggs that cause inflammation in bladder or intestinal wall
- leads to Katayama fever
Define definitive diagnosis
Indentification of parasites in host tissue or excreta - microscopy of different stages - parasites, cyst and ova
Diagnosis of malaria
Blood films - Giemsa stained blood film shows infected red cells (parasitaemia)
Thick and thin films
Explain serology
Detection of antibodies which is useful to detect when parasite is located in deep tissue sites
What is helminth infection accompanied by?
Eosinophilia and elevated IgE
What are three types of arthropods?
Lice, ticks and mites
