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 Taenia solium, is emerging as the leading cause of epilepsy among Hispanic populations in the US
Toxoplasmosis is an important cause of congenital birth defects
"Poverty and Neglected Diseases in the Other America", Professor Peter Hotez (George Washington University and the Sabin Vaccine Institute)

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

5. Why is this important to us?

6. Today Parasite overview Entameoba histolytica Giardia lamblia Malaria
Definitions
Life stages
Entameoba histolytica
Giardia lamblia
Malaria
Trichomonas vaginalis
Ascaris lumbricoides
Pinworms
Naeglaria fowleri

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. Entameoba histolytica
Anaerobic parasitic protozoan
Estimated to infect 50 million people worldwide
40,000 to 100,000 people worldwide die annually
90% asymptomatic
"Amebiasis". NEJM. United States NEJM: Massachusetts Medical Society Retrieved

10. Entameoba histolytica
Life cycle
Fecal/oral route
Anal/oral route

11. Entameoba histolytica
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. Entameoba histolytica
Diagnosis: stool sample
Treatment
Metronidazole highly effective against trophozoites
Paramoycin for cysts in lumen
Need both

13. Entameoba histolytica
What is most important about Entameoba histolytica?

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 Day- care centers
Untreated sewage
Cysts resistant to conventional water treatment methods including chlorination
Day- care centers
Giardia is 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
Plasmodium is 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: 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 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
Chloroquine Resistant 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
Destroys Plasmodium membranes

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

28. Trichomonas Vaginalis - 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. Trichomonas Vaginalis – 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. Trichomonas Vaginalis – Diagnosis and Treatment
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
Ascaris lumbricoides
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: Antihelminthic drugs
Both lead to worm passage in feces
Mebendazole (500mg): Kills worms
Levamisole (2.5mg/kg): Paralyzes worms

35. Pinworms
- Enterobius vermicularis 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
Ivermectin for urogenital migration
Broad Spectrum antiparasitic

40. Naegleria fowleri “The brain-eating amoeba” Region:
Incredibly rare, but found most commonly in the U.S
Between , 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. Naegleria fowleri - 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. Naegleria fowleri - 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. Naegleria fowleri – 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?