Parasites

1. Parasites

2. Why is this important to us? • Parasites in the U.S. • Toxocariasis now a common parasitic infection among inner city children • Cysticercosis, caused by the tapeworm Taeniasolium, is emerging as the leading cause of epilepsy among Hispanic populations in the US • Toxoplasmosis is an important cause of congenital birth defects

3. Why is this important to us? “The problem is that, due to a lack of education, most of the population doesn’t know that there’s a parasite wriggling within them,” says Patricia Wilkins, a scientist with the Center for Disease Control and Prevention (CDC)

4. Why is this important to us? Parasites outside the U.S.

5. Why is this important to us? • http://www.youtube.com/watch?v=TuU0uEY5ft0

6. Today • Parasite overview • Definitions • Life stages • Entameobahistolytica • Giardia lamblia • Malaria • Trichomonasvaginalis • Ascarislumbricoides • Pinworms • Naeglariafowleri

7. What are parasites? • Symbiosis: close and often long-term interaction between two or more different biological species • Mutualism - both individuals benefit • Commensalism - one benefits, the other is not significantly harmed or helped • Parasitism - one benefits, the other is harmed

8. Life cycles • Many parasites discussed today are protozoa • Some protozoa have life stages alternating between stages • Trophozoites– actively feeding • Cysts – can survive harsh conditions or long periods without access to nutrients, water or oxygen for extended period of time • Encystation • Excystation

9. Entameobahistolytica • Anaerobic parasitic protozoan • Estimated to infect 50 million people worldwide • 40,000 to 100,000 people worldwide die annually • 90% asymptomatic

10. Entameobahistolytica • Life cycle • Fecal/oral route • Anal/oral route

11. Entameobahistolytica • histo–lytic = tissue destroying • Ameobiasis • Symptoms take from a few days to a few weeks to develop and manifest themselves • Mild diarrhea to dysentery with blood and mucus (lining of intestine) • About 10% of invasive cases the amoebae enter the bloodstream • May travel to other organs in the body(liver)

12. Entameobahistolytica • Diagnosis: stool sample • Treatment • Metronidazole highly effective against trophozoites • Paramoycin for cysts in lumen • Need both

13. Entameobahistolytica • What is most important about Entameobahistolytica?

14. Giardia lamblia • Flagellated protozoan parasite • Anaeorobes • From the CDC: “Giardiasis is a global disease. It infects nearly 2% of adults and 6% to 8% of children in developed countries worldwide. Nearly 33% of people in developing countries have had giardiasis. In the United States, Giardia infection is the most common intestinal parasitic disease affecting humans”

15. Giardia lamblia • Fecal-oral route • Noninfective cyst excreted from feces of infectived individual • Once ingested by a host, trophozoite emerges to an active state of feeding and motility • After feeding, trophozoite undergoes binary fission

16. Giardia lamblia • Giardiasis • Colonization of gut results in inflammation and atrophy, reducing gut’s absorptive capability • Diarrhea, malaise, excessive gas, epigastric pain, bloating, nausea, diminished interest in food

17. Giardia lamblia • Accurate diagnosis requires an antigen test or, if that is unavailable, an ova and parasite examination of stool. • Multiple stool examinations are recommended, since the cysts and trophozoites are not shed consistently. • Given the difficult nature of testing to find the infection, including many false negatives, some patients should be treated based on symptoms. • Treatment: Metronidazole

18. Giardia lamblia • Waterborne sources • Untreated sewage • Cysts resistant to conventional water treatment methods including chlorination • Day- care centers • Giardiais also one of the most common parasites infecting cats, dogs and birds. Mammalian hosts also include cattle, beavers, deer, and sheep

19. Giardia lamblia • What is most important about Giardia lamblia?

20. Malaria • Region: Most Prevalent in Tropical Regions, but is present in the U.S. • Caused by the plasmodium species of protozoa • Of the 200 plasmodium varieties, 11 effect humans. • 4 of the plasmodium varieties induce Malaria • Plasmodiumis carried by the Anopheles species of mosquito. • Over 216 million NEW infections are estimated to occur every year • Over 600,000 malaria related deaths occur annually.

21. Malaria - Infection of the Mosquito • Many Anopheles mosquitos in afflicted regions are born infected. • Can become exposed by eating the blood of an infected organism • Plasmodium travels through the blood stream to the stomach • Host Organism • Gametes • Travels to the salivary glands until the mosquito’s next meal

22. Malaria – Infection of Humans • Starts with the Mosquito Bite • Enters the blood through salivary secretions • Sporozoite phase travels to the liver • Maturation  Merozoites • Proliferation • Rupture the Infected Hepatocyte, • reentering the blood stream • Enter Erythrocytes (red blood cells) • Feed on hemoglobin, releasing toxic • heme byproduct • Proliferation: 48-72 hour cycles • Rupture of the Erythrocyte

23. Malaria – Infection of Humans (cont.)

24. Malaria - Symptoms • Develop 10-28 Days After Infection • Most Common Symptoms Include • Fever • Chills • Jaundice • Enlarged Liver and Spleen • *Symptoms occur in 48-72 hour cycles. Why? • If left untreated… • Renal, Liver, Respiratory Failure • Liver and Spleen Rupture • Meningitis • Cerebritis

25. Malaria – Diagnosis and Treatment • Physical Exam – Enlarged Liver and Spleen • Blood Test (CBC) – Anemia • Blood Smear – Look for the parasite • Treatment: Chloroquine(antimalarial drug) • Prevents plasmodium metabolism • Must begin while liver is functional • ChloroquineResistant Strains Exist, • Quinidine (antiarrhythmic) • Doxycycline (antibiotic) • Prognosis: Good

26. Malaria – Sickle Cell Anemia • Heterozygous-recessive trait • Homozygous: Shortened life expectancy • Offers the “heterozygous advantage” • Leads to “sickling” of erythrocytes • Due to inability to crystallize hemoglobin • Reduces O2 Binding Capacity • Reduces flexibility of erythrocyte • Clotting • Blood Vessel Occlusion • Prevents Plasmodium from entering • and/or proliferating • Mechanism is not certain • Reduced O2 availability • Prevents Plasmodiumfrom entering • Destroys Plasmodiummembranes

27. TrichomonasVaginalis • Region: • Present Worldwide • Most common parasitic infection in U.S. • Estimated 3.7 million new cases annually • Species: • Trichomonasvaginalis • Humans are the only known vectors • Do not have a cystic form • Must be transmitted by direct contact

28. TrichomonasVaginalis - Infection • Generally Sexually Acquired • Toilets • Other Items that Contact Genitals • “Stuck” in the trophozoite phase • Grow flagella during development • Proliferate via binary fission • Inhabit genitalia • Live in urogenital epithelium • Feeds on: • Bacteria  Phagocytosis • Vaginal Secretions

29. TrichomonasVaginalis – Symptoms • Only 30% of Infected persons show any symptoms • More common in females • 5-28 Days • Men: • Itching/Irritation of Penis • Burning Sensation • Discharge • Women: • “Strawberry Cervix” (2%) • Itching, Burning, Redness, Soreness of Genitals • Discomfort during Urination • Odorous yellow-green discharge (12%)

30. TrichomonasVaginalis – Diagnosis and Treatment • Diagnosis (12%): • Physical Exam: Nearly Impossible • Laboratory: Microscopic Observation of Discharge • Very Low Sensitivity • Treatment: • Metronidazole (antibiotic) • One large (2 gram) dose • Passes through mucous membrane into protozoa • Resistant Strains Exist • Treatment is a Challenge • Prognosis: • Most commonly cured STI • 95%

31. Ascariasis Ascariasis = Infection by parasitic nematode Ascarislumbricoides Region: Present Worldwide, most common in sub-tropical, developing nations  Human Feces used as Fertilizer Estimated: 1 billion infections worldwide, 4 million infected Americans Ascariasis: “Long Intestinal Roundworm” Cylindrical 2-6 mm in diameter, 15-35 cm (7-15 inches) long

32. Ascariasis - Infection • In the soil – 18 days to become infectious, can survive for 10 years. • Eggs pass to humans by direct contact • Eggs travel to the small intestine, hatch after 2 weeks. • Enter blood circulation  Lungs • Mature in Lungs for ~1 week, then reenter the intestines. • Fully develop in the intestines, differentiating into adult males and females • Sexually reproduce, up to 200,000 eggs/day • 2-3 Months Total

33. Ascariasis - Symptoms Many People Show No Symptoms! Lung Phase: Ascaris Pneumonitis • Coughing • Wheezing • Shortness of Breath • Cannot be diagnosed Intestinal Phase • Vague to Severe Abdominal Pain • Nausea and Vomiting • Weight loss/malnutrition • Diarrhea and Bloody Stool Complications • Gall bladder obstruction  Gall stones • Intestinal Blockage and Perforation • Pancreatitis

34. Ascariasis – Diagnosis and Treatment Diagnostic Tools • Microscopic Study of the Stool • 40 days • CBC – Eosinophilia increase • Not specific • Abdominal CT or X-Ray • Endoscopy Treatment Options • Untreated Infections will often resolve • Two classes of medical treatment options: Antihelminthicdrugs • Both lead to worm passage in feces • Mebendazole (500mg): Kills worms • Levamisole (2.5mg/kg): Paralyzes worms

35. Pinworms - Enterobiusvermicularis in America Region : • Worldwide, most common helminth infection in the U.S. and Western Europe. • 11.4% (~40 million) in the U.S. are infected • Most common in children • 50% in England Species: • 1 of 3 types of parasitic pinworms, the only one that affects humans • Humans are the only known host • Small (13x0.5 mm), white, and delicate • Females have a sharp rear end • Eggs are microscopic

36. Pinworms - Infection • Eggs spread by touch • Mouth (inhalation or ingestion) • Anus • Infected persons often carry eggs beneath fingernails • Eggs are extremely hardy • Can survive on inanimate surfaces for up to 3 weeks • Towels • Curtains • Toys • Furniture

37. Pinworms – Life Cycle Takes place in a single host • After ingestion, eggs hatch in the duodenum • Larvae grow and move towards colon • Develop into adult • Mating occurs in the cecum • Males die after mating • Females attach to the ascending colon, feeding on colic contents • Produce eggs • Travel through large intestine • Emerges from anus to lay eggs • Spread by contact • Retroinfection

38. Pinworms – Symptoms • Causes enterobiasis -Often asymptomatic • Itching in the anal region • Especially at night • Insomnia • Anorexia • Weight Loss • Irritability Secondary Issues: • Vulvovaginitis • Urinary Tract Infection • Bacterial Infections

39. Pinworms – Diagnosis and Treatment Diagnostic Tools • “Scotch Tape Test” • 90% Sensitivity • Visual Observation • Anal Swabs Treatment • Benzimidazole or Mebendazole (antiparasitic) • Target adult worms • Prevents glycogen storage, leads to starvation • Hygiene!! • Prevents reinfection • Ivermectinfor urogenital migration • Broad Spectrum antiparasitic

40. Naegleriafowleri “The brain-eating amoeba” Region: • Incredibly rare, but found most commonly in the U.S • Between 2000-2010, 32 cases • Found in warm, fresh bodies of water, soil near such locations, and unchlorinated swimming pools • 2 Deaths from Neti Pot Use Species: • Sensitive single-celled amoeba • Thermophile • Cannot survive in salty environments • Has 3 stages to its life cycle: • Cyst Stage: Present in unfavorable conditions, inactive • Trophozoite: The “active” phase, it proliferates by binary fission. They feed on bacteria. • Flagellate: Can change rapidly back and forth to trophozoite phase, motile.

41. Naegleriafowleri - Infection • The trophozoite is the infectious form • Gets introduced through the nose • Embeds in the nasal epithelium • Attracted to the neurotransmitters of Olfactory nerve • “Eat” the olfactory nerve and bulb, back to the cerebrum. • Spread to the rest of the brain

42. Naegleriafowleri - Symptoms • Causes by Primary Amoebic Meningoencephalitis (PAM) • Symptoms take ~5 days to present, at which time it is often too late for treatment. • Death occurs 3-7 days after first symptoms Symptoms: Common with other encephalitic conditions • Nausea • Vomiting • Headache • Stiff Neck • Delirium • Seizures Complications: • Coma • Respiratory Arrest

43. Naegleriafowleri – Diagnosis and Treatment Diagnostic Tools • Lumbar Puncture • Analysis of CSF • Indicated for by Symptoms “Treatment” • “Heroic” dose of Amphotericin B (systematic antifungal) • Miltefosine and Fluconazole • Not FDA Approved • Testing on Phenothiazine Antipsychotic Chlorpromazine Prognosis: 2-3% survival rate

44. Questions?