Eukaryotic Parasites. An Illustrated Guide to Parsitic Life Cycles to Accompany Lecture. By Noel Ways

Transcription

1 Eukaryotic Parasites An Illustrated Guide to Parsitic Life Cycles to Accompany Lecture By Noel Ways

2 Giardia lamblia Life Cycle Reservoir: Beavers strongly implicated. Also, many other wild animals as well as domestic animals Stomach Fecal / Oral Route Cysts Large Intestine Excystment in Small Intestine Small Intestines Trophozoites Fomites Food Feces Water Page 2

3 BLOODAmoebiasis Life Cycle Entamoeba histolytica (invasive) Entamoeba dispar (non-invasive) Disseminated infection results in organ lesions /peritonitis and death Stomach Fecal / Oral Route Excystment in Small Intestine Encystment in Large intestine Note: blood invasion is rare Cysts Large Intestine Trophozoites (in Small Intestine) Ulcerations Fomites Food Feces Water Trophozoite Migration

4 Balantidium coli Life Cycle Swine Trophozoites INVADE mucosa and may cause ulceration ( ). Rarely, invasion occurs resulting in peritonitis. Reservoir consists mainly of swine, but also humans, rats and others. Transmission is fecal / oral route. Stomach Swine Cysts Large Intestine Fecal / Oral Route Fomites Food Feces Water Encystment in large intestine Excystment in Small Intestine Trophozoite Migration Small Intestines Trophozoites Both trophozoites and cysts found in stools Page 4

5 Paragonimus westermani Life Cycle Cercaria penetrate and encyst forming Metacercaria within tissue. Cercaria seek out crayfish or crabs. Redia asexually reporduce. Within rediae, cercaria are produced. Note tails. Cercaria will bore out and leave snail. Cercaria Redia Miracidia penetrate species specific snail. Forms Redia Page 5 Man eats undercooked crustaceans and metacecariae develop into flukes which migrate to lungs and other organs. In lungs, eggs produced are coughed up and swallowed, thereby leaving via feces. Embryonated Eggs hatch. Miracidia develop and seek out species specific snail. References: Parasitology by Noble and Noble Microbiology by Tortora

6 Taeniarhynchus saginatus Life Cycle Head Evaginates and hooks into small intestine of man Undercooked Beef Tapeworm develops Larvae encysts in skeletal muscle Cows, Buffalo, etc. Larvae travels via blood stream to skeletal muscle Embryo liberated Eggs freed from gravid proglotids Gravid proglotids pass in feces of man Page 6

7 Taenia solium Life Cycle Head Evaginates and hooks into small intestine of man Undercooked Pork Tapeworm develops Larvae encysts in skeletal muscle Swine Cysticerosis when embryos injested by man. Cysticerci develop in brain, liver, muscles, and heart of man. Larvae travels via blood stream to skeletal muscle Embryo liberated Eggs freed from gravid proglotids Gravid proglotids pass in feces of man Page 7

8 Domestic Life Cycles Undercooked BAdequately Cooked Bin a huge decrease Yand Sylvatic: of the forest. If something is referred to as sylvatic, then it In the case of Trichinella occurs in the wild. The opposite of sylvatic is domestic. In discussions spiralis, the parasite is alive regarding parasites, sylvatic cycles often refer to the maintenance and and well all around us in relationships between a parasite and it s host(s) in nature through time. raccoons, rats, lynx, opossums, However, there are many instances where a parasite that is maintained beavers, etc. etc. (the in nature slips into our domestic affairs / concerns. list is huge). And, 100 years ago, trichinosis was a major health issue with about 20% of the American population harboring Raw Scraps YSylvatic Sylvatic Cycle cysts by old age. Domestic Cycle Raw Scraps Carnivorous Wild Mammals Carnivorous Food Industry Migration from the of all types sylvatic community into the domestic community was straight forward. Federal Biosecurity Sterilized Scraps general public Domestic Cycle Sylvatic Cycle Sterilized Carnivorous Wild Mammals Carnivorous awareness of the Food Industry Scraps of all types existence of this and hygiene guidelines as well as disease, has resulted Biosecurity and Biohygiene practices regarding trichinosis: Cook meat thoroughly (follow directions) Clean cooking utensils thoroughly By law, potentially infected food scraps must be sterilized Prevent vermin contact with livestock Provide clean living conditions for livestock Page 8 in incident rate. Most cases in the US now come from hunters who improperly prepare their wild meats. BIOISOEHCYUGREINTEBIOISOEHCYUGREINTE

9 Trichinella spiralis Life Cycle Larvae encyst in skeletal muscle Larvae encyst in organs / muscles of man Undercooked Pork Undercooked Meat eaten by man Flesh eaten by animals Larvae burrow into body organs and skeletal muscle tissue Carnivorous Sylvatic Cycle Wild Mammals of all types Carnivorous Larvae excyst in small intestine Scraps Domestic Cycle Food Industry Scraps Blood Vessel Larvae migrate through blood venous system to body tissues, particularly skeletal muscle Adults mate. Female burrows into mucosa and deposits ~1,500 larvae. Page 9 Larvae develop into adults in Small Intestine Reference: Parasitology by Noble and Noble

10 Ascaris lumbricoides Life Cycle 5 8. Larvae ( ) hatch and bore through intestinal mucosa. 9. Enter hepatic portal system and migrate to liver, then right heart and then lungs. 1. Sexual Reproduction results in copious egg ( ) production (~200,000 / day) 2. Fertilized eggs passed in feces Larvae enter alveoli. Patient may experience severe ascaris pneumonitis at this time. 11. Tracheal Migration. Larvae migrate up respiratory tree to pharynx. 3. Embryo develops within egg case 10 4 Larvae in Egg 4 Development continues, larvae form. 5. Fecally contaminated food with embryonated eggs ( ) injested Fertilized Eggs Larvae are now reflexively swallowed. 6. Embryonated eggs swallowed 7. Pass through stomach and enter small intestine 3 Development Pass through stomach. 14. Enter small intestine and develop into adults. Cycle now repeats: (start back at 1). Embryonated Egg Fertilized Egg Page 10 References: CDC ( An Illustrated Laboratory Text in Zoology by Boolootian and Heyneman c 1991