Protozoa Diseases and Coccidian Lifecycles

Question 1

What problems/diseases do Neospora, Sarcocystis, Giardia and Babesia cause?

Answer 1

Neospora - Abortion in cattle, genital defects in dogs
Sarcocystis - Equine protozoal Myeloencephalitis
Giardia - Giardiasis
Babesia - Bovine Babesiosis

Question 2

What are the common characteristics of coccidia?

Answer 2

Subclass of protists that belong to the ampicolmplexa

• sexual cycle occurs in the epithelial cells (gut in most species)
• Oocysts (infective stages) secretion after sexual cycle
• Usually infection acquired through gastrointestinal tract

Question 3

Name the organelles found in an ampicomplexan (15)

Answer 3

Conoid
Apical
Microneme
Microtubular network
Inner membrane complex
Rhoptry
Dense granule
Golgi apparatus
Mitochondrian
Apicoplast
Centrosome
Centrocone
Nucleus
Endoplasmic reticulum

Question 4

What is the reproductive process undertaken by ampicomplexans?

Answer 4

Schizogony - asexual reproduction in which the nucleus divides prior to cell division

Question 5

Describe the sexual life cycle of a coccidia

Answer 5

Ingestion of oocysyt (Highly resistant)
Stomach acid breaks open oocysts without killing parasite
Parasite invades epithelial cells
Undergoes schizogony
Eventually become merozoites
Merozoites undergo schizogony
They then divide and become either microgametes (male equivalent) or macrogametes (female gamete)
Both male and female come together and form a zygote
Sporulation occurs and oocysts are expelled in faeces

Question 6

Describe cryptosporidia

Answer 6

• Once thought to have many species but now thought to contain only a few species with broad specificity
• Direct (fecal-oral) life cycle with no intermediate host
• During excretion of oocysts immunocompromised hosts can produce up to 50L of diarrhoea a day and can ultimately cause death
• Parasite develops just under the host epithelial membrane in an intracellular but extracytoplasmic posiiton
• Oocyst stages are fully formed when expelled from the host
• No need for sporulation and therefore oocysts are immediatley infective (auto-infection) - can re-infect ourselves
• Important pathogen in cattle
• Came to light in the 1980s due to large number of AIDS patient
• No effective treatment

Question 7

Describe Eimeria

Answer 7

Generally host specific
Cannot be transmitted from animal to man
Many species infect domestic animals - veterinary importance
Some hosts are susceptible to more than one species
Direct (fecal-oral) life cycle with no intermediate hosts
Particular problem in chickens in high intensity battery farming
Infected animals have severe diarrhoea
Treatment - Monensin

Question 8

Describe T.gondii

Answer 8

Sexual cycle takes place in the epithelium of cats
Similar sexual cycle to Eimeria
Direct (fecal-oral) life cycle can occur in cats
Intermediate hosts - any warm blooded animal that ingestts oocysts can become infected
- Does not undergo sexual multiplication in the gut of intermediate hosts, instead it undergoes asexual (extra-intestinal) multiplication in any cell of the host as the tachyzoite stage for around 14 days

Question 9

Describe the asexual life cycle within an intermediate host of T.gondii

Answer 9

Ingestion of oocyst
Multiple rounds of fast asexual division (tachyzoites)
Tachyzoites transform into bradyzoites
Bradyzoites - divide slowly and form cysts (infective)

Question 10

What diseases do Plasmodium, Leishmania, Eimeria and Toxoplasma cause?

Answer 10

Plasmodium - malaria
Leishmania - Kala-Azar, Oriental-sore, Espundia
Eimeria - Coccidiosis
Toxoplasma - Toxoplasmosis