Protozoa including Giardia Flashcards
Name some examples of protozoan infections
- Toxoplasma gondii (cats)
- Neospora caninum (dogs)
- Sarcocystis (cats and dogs)
- Cystoisospora (cats and dogs)
- Giardia
- Leishmania infantum
- Babesia canis
Describe the main features of phylum apicomplexa
- Large group of protozoa
- Mostly intracellular
- Locomotion by gliding
- Undergo sexual and asexual reproduction
- Involved in host cell invasion
How is Toxoplasma gondii linked to sheep?
Second most important cause of abortion in sheep in Britain
What spp is the definitive host of Toxoplasma gondii?
Cats
What are the 3 life cycle stages of the Toxoplasma gondii parasite?
- Tachyzoite
- Bradyzoite
- Oocyst
Describe a tachyzoite
- Intracellular
- Rapidly dividing
- Crescent shaped - 2x6um
Describe a bradyzoite
- Within a bradyzoite cyst
- Neural or muscle tissue
- Slow growing
- Persistent
Describe an oocyst
- Unsporulated oocyst passed in faeces
- Sporulated oocyst contains two sporocysts and four sporozoites
- 12um
Describe the life cycle of Toxoplasma gondii within the definitive host
- Sexual reproduction part of the life cycle
- Ingestion of prey containing bradyzoite cysts
- Cyst wall is digested in the GIT, liberating bradyzoites
- Bradyzoites invade the intestinal epithelial cells
- Bradyzoites divide by schizogony giving rise to merozoites
- Differentiate into male and female gametocytes - microgametes and macrogametes.
- Fertilization gives rise to an unsporulated oocyst shed with cat faeces
- Sporulation occurs and generates two sporocysts with four sporozoites each.
What is schizogony?
Asexual reproduction
Describe the life cycle of Toxoplasma gondii inside the intermediate host
- Following ingestion sporozoites are released and they cross the gut wall
- Develop into tachyzoites which replicate rapidly
- They then differentiate into bradyzoites which form cysts
Describe toxoplasma gondii disease in cats
- No disease
- No clinical signs
- Restricted to the sexual cycle in the gut
- Produce oocysts
Can Toxoplasma gondii be controlled in cats?
- Drugs are not a realistic, practical option
- No vaccines
How is Toxoplasmosis transmitted to humans?
- Tissue cysts in undercooked meat
- Ingesting oocysts contaminating food
Describe vertical transmission of Toxoplasma in humans
- Infected mother prior to pregnancy, foetus is protected by mothers immunity
- Primary infection during pregnancy can have severe effects on the foetus
What are the effects of Toxoplasma on a foetus?
- Miscarriage, still born
- Hydrocephalus
- Convulsions
- Intracerebral calcification
- Retinochoroiditis
Which people are most at risk of Toxoplasma?
Immunocompromised
How can toxoplasma be controlled in humans?
- Chemotherapy: pyrimethamine and sulphonamides used to treat acute infections in humans
- Reduce risk of infection, especially pregnant women: oocysts in soil (gardening, unwashed vegetables), cook meat to kill bradyzoite cysts
Which spp are the definitive and intermediate hosts of Neospora caninum
Definitive = dog Intermediate = dog and cattle
How does the seroprevalence of Toxoplasma compare to Neospora
Lower number of Neospora oocysts produced by an infected dog compared to Toxoplasma oocysts produced by an infected cat
Describe the life cycle of Neospora caninum in the definitive host
- Ingestion of bradyzoites from bovine tissues, released into the dogs duodenum where they undergo merogony
- Transient appearance of oocysts in faeces – sexual phase
- No disease
- Antibody response may or may not be present
Describe the life cycle of Neospora caninum in the intermediate host
- Transplacental transmission following ingestion
- Cysts in the muscle of intermediate host
- No oocysts in faeces as this is the asexual phase
- Positive antibody response
Describe the disease of Neospora caninum in dogs vs cattle
- Disease in dogs – neonatal paresis
* Disease in cattle – abortion
What are the clinical signs of Neospora caninum in young dogs?
- Ataxia, hindlimb paresis, loss of reflexes
- Ascending paralysis, dysphagia
- Hyperextension of hindlimb(s)