Presentation on theme: "Parasites. Why is this important to us? Parasites in the U.S. – Toxocariasis now a common parasitic infection among inner city children – Cysticercosis,"— Presentation transcript:
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
“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) Why is this important to us?
Parasites outside the U.S. Why is this important to us?
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
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
Entameoba histolytica Anaerobic parasitic protozoan Estimated to infect 50 million people worldwide 40,000 to 100,000 people worldwide die annually 90% asymptomatic
Entameoba histolytica Life cycle Fecal/oral route Anal/oral route
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)
Entameoba histolytica Diagnosis: stool sample Treatment – Metronidazole highly effective against trophozoites – Paramoycin for cysts in lumen – Need both
Entameoba histolytica What is most important about Entameoba histolytica?
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”
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
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
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
Giardia lamblia Waterborne sources – 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
Giardia lamblia What is most important about Giardia lamblia?
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.
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
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
Malaria – Infection of Humans (cont.)
Malaria - Symptoms Develop 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
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
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 O 2 Binding Capacity Reduces flexibility of erythrocyte Clotting Blood Vessel Occlusion Prevents Plasmodium from entering and/or proliferating Mechanism is not certain Reduced O 2 availability Prevents Plasmodium from entering Destroys Plasmodium membranes
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
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
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%)
Trichomonas Vaginalis – 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%
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, cm (7-15 inches) long
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
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
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
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
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
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
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
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.
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
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
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