lecture 15- Protozoa, toxoplasma and cryptosporidium Flashcards
(57 cards)
where was toxoplasma first isolated from?
an African desert rodent Ctenofactylus gundi
what are some characteristics of Toxoplasma gondii?
- one of the most common human infections found throughout the world
- obligate intracellular parasites
- has a very low intermediate host specificity and will probably infect almost any mammal
- has also been reported in birds, and most recently in fish
- infects almost all tissues
- causes the disease, toxoplasmosis
- in most healthy humans, the disease is asymptomatic
where is toxoplasma gondii found the most?
higher prevalence in central america
what animal is toxoplasma gondii most frequently found in?
stray cats
how is one infected by toxoplasma gondii?
consumption of raw or undercooked meat that has been contaminated by the parasite
what is the economic impact of toxoplasma gondii?
devastating economic impact on the countries who export livestock.
leading cause of abortion in sheep and goats.
cattle are less affected.
what are the 2 hosts involved in the cycle of T. gondii?
- the definitive host= domestic and wild cats
- the intermediate host= most species of warm-blooded animals including birds, mice, squirrels, rabbits, cattle, pigs, sheep, and humans
what are the two phases of T. gondii life cycle?
- the intestinal phase
- the extra-intestinal phase
the intestinal phase occurs in cats only
the extra-intestinal phase occurs in all infected animals
how are cats infected by T. gondii?
- eating oocyst in cat feces or:
2. eating intermediate host (bird or mouse) containing bradyzoites
oocysts, sporozoites, and bradyzoites penetrate the…
small intestinal cell and develop into trophozoites that then undergo schizogony and develop into merozoites which re-invade the small intestinal cell and turn into gametocytes
toxoplasmosis is commonly transmitted from … to …
cats to humans
what type of reproduction does the parasite undergo in the intermediate/reservoir host?
asexual reproduction
what are the three infective forms of toxoplasma gondii?
- oocysts
- tachyzoites
- bradyzoites (tissue cysts)
where are oocysts shed?
in the feces of the cat
how long do infected cats shed oocysts for?
1-2 weeks
how long is it until oocysts are infective after being shed from the cat?
oocysts sporulate and only become infective after 1-5 days
the oocyst contains…
two sporocysts, each of which contain four sporozoites
what is the potential of oocyst survival?
have the potential to remain viable for many years
what is the significance of tachyzoites?
- mark the acute phase of infection
- invade all nucleated cells and occur in groups
- rapid multiplication and cell lyses
- rapidly growing stage observed in the early stage of infection
what are bradyzoites?
slowly growing trophozoites that are in tissue cysts.
They occur as a circular mass in body cells
what is the significance of bradyzoites?
they mark the chronic phase of infection, are resistant to low pH and digestive enzymes during stomach passage, and released into the intestine and are highly infective if ingested
what are ways humans can become infected with T. gondii?
- eating raw or undercooked meat of animals harboring tissue cysts
- consuming food or water contaminated with oocysts from cat feces or by contaminated environmental samples
- blood transfusion or organ transplantation (both rare)
- transplacentally from mother to fetus
prevention of T. gondii:
- wash hands and countertop thoroughly after preparing raw meat and fish
- thoroughly cook meat
- wash and/or peel fruits and vegetables
- clean litter box daily
- feed cat commercial dry food, never raw meat
- cover outdoor sandboxes
toxoplasmosis in cats
asymptomatic in adult cats. acute infections result in numerous intestinal lesions that can kill kittens (rare)
