Welcome to our presentation on toxoplasmosis. This is prepared by Mramba Nyindo, that's me, and my colleague is John [INAUDIBLE] at the Kilimanjaro Christian Medical University College in Moshi, Tanzania. Let's make a one general remark that if you keep a cat In the house, beware of toxoplasmosis. This is a disease of the domestic cat. This cat is the definitive host of toxoplasma that all warm-blooded animals, which includes humans, also birds can be infected and act as intermediate hosts. We are actually intermediate hosts. Toxoplasmosis has a world-wide distribution. Let's look at an organism which is Toxoplasma gondii, similar to malaria parasites, therefore it belongs to phylum apicomplexa. Toxoplasma gondii can complete its life cycle in the intestines of the domestic cat. Therefore, the domestic cat is a definitive host of Toxoplasma gondii. About 200 mammalian species act as intermediate hosts of Toxoplasma gondii. Therefore, this makes the prevalence of toxoplasmosis in humans high. Human infection with the Toxoplasma gondii is usually asymptomatic, no disease manifestation. Acute toxoplasmosis, congenital toxoplasmosis, which means transfer of parasites to the fetus, and this may lead to abortion. Ocular toxoplasmosis, it will affect the eye. Retinochoroiditis is an important thing that people in the eye department must be aware of. Symptomatic disease can be triggered. [COUGH] Excuse me. By a state of immunodeficiency, immunocompromisation, and at the top of this list is HIV infection. When this happens, toxoplasmosis manifests as a serious generalized granulomatous disease [INAUDIBLE]. This is the life cycle here, briefly shown here, this is your cat, the definitive host. It will release in it's feces the oocysts and this is really how we get to the infection from the host. But we can get the infection from eating a pig, where there are organisms we call bradyzoites emit. If you eat undercooked pork, you'll probably get an infection. These are reservoir hosts, carnivorous things in the bushes, birds we have also shown that. But here is congenital, this fetus here is in very bad shape, it has been infected from the mother. There is also reactivation encephalitis. This is a very serious disease when it manifests itself, causing acute infection in the human. In the cat's intestinal epithelia cells, and that is where things will start, there will double up sexually and finally, the life stage of this parasite to produce oocysts. These, as shown in the picture before, are released into the environment through the feces. Those of you who keep cats and have got areas where these cats actual defecate, beware of the fecal material from these cats. The oocysts are eaten by wild rodents where they form sporozoites in the gut. Sporozoites in rodents will develop to cysts, where? In the brain, muscles, etc. Cysts can contain bradyzoites and this is the word to watch, bradyzoites and these are dormant stage of the parasite. Bradyzoites don't give you disease, they are actually cysts. They are waiting for you to be immunocompromised, and give you the infection through tachyzoites, which I'll talk about this later. Cats become infected by eating infected rodent meat or birds or by eating the oocysts which they have released. In the rodent meat are found the bradyzoites, and this is the word to watch. These are the types that give you the acute disease. In the intestines of cats, bradyzoites are released and invade intestinal cells to induce a sexual reproductive cycle and therefore, this is a definitive host. How do humans become infected with the toxoplasmosis? By swallowing oocysts, from where? The cat, or more commonly by eating pseudocysts containing tachyzoites. How does it happen? When we eat undercooked meat from a cow, sheep, or pig which contain these organisms. You can also get it from drinking the milk from these animals, cow and sheep. Tachyzoites cause acute infection, toxoplasmosis. Immune response against the virulent tachyzoites makes them become bradyzoites. Bradyzoites are dormant, no disease causing forms of the parasites. Bradyzoites enter human monocular cells, rapidly multiply, they undergo asexual schizogony, like what we see in malaria. They form pseudocysts, and these pseudocysts contain the tachyzoites. Pseudocysts containing the tachyzoites are commonly present where? The muscles, the brain, the eye, and other parts of the body. Pseudocysts may also be present in the pregnant uterus where they cause serious disease, abortion, fetal loss, for that matter. What follows after you have eaten contaminated meat, contaminated with a Toxoplasma gondii? Usually, nothing much happens in form of disease manifestations. You are a happy guy walking around. A person may develop a flu-like fever, however, due tachyzoite growth and multiplication. Note that host's immune response to tachyzoites will make tachyzoites convert or become bradyzoites, the dormant hiding form. Be sure, you can be carrying with you bradyzoites throughout your life but when you become immunocompromised, as I said earlier, you're in trouble. Sources of human infection would be consumption of undercooked meat containing bradyzoites, through the placenta, also the organ transplants. I think in the western world, America, situations of toxoplasmosis after a transplant have been recorded. You can also get it through blood transfusion. You can get it through ingestion of the oocyst. Therefore, toxoplasmosis is a disease of cats, which when it occurs in humans, it will cause serious illnesses, which can affect the eye, the brain, the fetus, etc. I hope you have enjoyed this presentation on toxoplasmosis. We come to the end of our presentation, thank you very much for participating.
