Protozoa

• Protozoa


  Single celled organisms
• Protozoa


  • 50,000 known species
  • 10,000 are parasitic
• Protozoa


  • Obtain energy through Pinocytosis (fluid intake)
  • Phagocytosis (particle intake)
• Classes of Protozoa


  • Coccidia
  • Eimeridae
  • Sarcocystidae
  • Gimenidae
• Coccidiosis


  Eimeria infection
• Hosts of Gimenidae


  • Dogs
  • Cats
  • Horses
  • Pigs
  • Poultry
  • Cows
  • Sheep
• Gimenidae


  • Occur mainly in epithelial cells of gut
  • Presence of oocysts (eggs) in faeces
• Lifecycle of Eimeridae


  1. Unsporulated oocyst

  2. Sporulated oocyst

  3. Sporocyst

  4. Sporozoite

  5. Merogony

  6. Gametogony

  7. Sporogony
• Cocysts can survive for many years (strong outer shell)
• Disinfectants won't remove them
• Deep litter bedding systems are susceptible - moisture, temp, ventilation, overcrowding
• Pathogenesis of Coccidiosis


  • Changes in intestinal mucosa
  • Severity of damage depends on numbers and location
  • Reduces water and nutrient absorption
  • Weight loss, diarrhoea
• Isospara


  Mature Isospara live in intestines, oocysts pass in faeces where they sporulate
• Coccidiosis in Dogs


  • Dogs/cats ingest oocysts - liberate sporozoites, merozoites
  • Clinical signs due to large number of oocysts digested
  • Each merozoite invades another intestinal cell to reproduce - happens 2-4 times
  • Bloody, watery diarrhoea
  • Dehydration, lethargy
• Common in young animals, can differentiate ratio of merozoites becoming male or female
• Coccidiosis in Poultry


  • Can vaccinate - drugs in food and water
  • Keep poultry houses clear, well ventilated
• Coccidiosis in Sheep


  • Lambs most at risk
  • Gut damage/lesions
  • Malabsorption
  • Severe diarrhoea
  • Peri-parturient rise
• Sarcocystidae


  • Toxoplasma gondii
• Toxoplasma gondii


  Cats are definitive host, range of intermediate hosts (sheep, birds, rodents, humans)
• Lifecycle of Toxoplasma gondii

  1. Oocysts shed by cat

  2. Intermediate host ingests oocysts - invades tissue, forms cysts

  3. Cysts passed to definitive host when tissue eaten

  4. Oocysts reproduced within cat
• Effects of Toxoplasma gondii

  • Cysts can affect vital organs
  • In pregnant intermediate host - early pregnancy abortion, mid-late pregnancy mummified fetus, congenital defects
  • In humans - low grade fever, lethargy, serious for pregnant women (abortion, stillbirth, CNS damage)
• Rats attracted to cat urine, continues lifecycle
• Toxoplasmosis in Dogs


  • Fever, anorexia, diarrhoea, pneumonia, neurological damage
• No cats, no Toxoplasmosis
• Cats act as carriers, peri-parturient rise in oocysts around pregnancy
• Control of Toxoplasmosis


  1. Tokovax (sheep)

  2. Reduce number of cats

  3. Humans not exposed to cat faeces

  4. No contamination of feed and water with cat faeces
• Diagnosis early on via post mortem in still borns