MICR 420

Emerging and Re-EmergingInfectious Diseases

Lecture 8:Trypanosoma, PlasmodiumDr. Nancy McQueen & Dr. Edith Porter

Overview

Trypanosoma Plasmodium

Protozoa Morphology Growth Life cycles Vectors Pathogenesis Diseases Diagnosis Therapy Prevention Threats

Protozoa

Eukaryotic Always unicellular Chemoheterotrophs Digestion in

vacuoles Often life cycles

Some produce cysts Resistant survival

forms Vegetative form is a

trophozoite Reproduction

Asexual Sexual reproduction

?

Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc.

Classification of Protozoa

Amoebozoa: motile, pseudopodia Ciliophora: motile, cilia Archaezoa: motile, flagella, no mitochondria Euglenozoa: flagella, disk shaped mitochondria Apicomplexa: non-motile, complex life cycles

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Trypanosoma

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Characteristics of Trypanosoma

Flagella Undulating

membrane

Kinetoplast Elongated mitochondrion with K-

DNA Thousands of mini-circles and a

few macro circles Involved in RNA editing Adjacent to flagellar basal body

Trypanosomiasis: Diseases

African Trypanosomiasis

Sleeping sickness Transmitted by tsetse

fly Large and aggressive fly Painful bites

American Trypanosomiasis

Chagas disease Transmitted by kissing

bug Triatomine insect

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Life Cycle of American Trypanosomiasis

Chagas Disease Endemic in Mexico, Central America, and South America

~ 8 to 11 million people are infected Local lesion (chagoma, palpebral edema) at the site of

inoculation Acute phase (2 -3 months)

Usually asymptomatic Fever, anorexia Lymphadenopathy Mild hepatosplenomegaly Myocarditis

Asymptomatic chronic stage (years- decades) Symptomatic chronic stage

Cardiomyopathy (the most serious manifestation) Megaesophagus Megacolon Weight loss Can be fatal

Trypanosoma: Pathogenesis Antigenic variation Surface variant-specific glycoprotein (VSG) Each trypanosome has about 1000 genes

encoding different VSGs Only the gene in a specific expression site within

the telomere at one end of the chromosome is active

Gene conversion Mechanism for changing the VSG gene expressed An inactive gene is copied and transposed into the

telomeric expression site Spontaneous switch Survival advantage when antibodies are produced against

the original VSG type

Trypanosoma: Gene Conversion in the Variable Surface Glycoprotein and Antibody Response

Chagas Disease: Diagnosis Blood smear

Only during acute phase

Patient antibodies Two or more serological tests

Indirect fluorescence assay ELISA

Xenodiagnosis To detect low levels of parasitemia Laboratory-raised non-infected

vectors (triatomine or kissing bug) feed on patient

Triatomines are later dissected and examined for trypanosoma via microscopy or PCR

T. cruzi

Large kinetoplast

IFA

Chagas Disease: Therapy

Only acute, congenital, chronic in children and adults less than 50 years of age without cardiomyopathy

Not FDA approved and available only from CDC under investigational protocols Benznidazole Nifurtimox

Trypanosoma: Prevention

Vector reduction Spray Replacement of wood with metal In Uruguay from 80% infected households to 0.1

% in 16 years Safe work practice

Highly infectious Screening of blood products

Threats by Trypanosoma

Vector-borne infectious diseases are emerging or resurging Changes in public health policy Shift in emphasis from prevention to emergency

response Insecticide and drug resistance Demographic and societal changes Genetic changes in pathogens

Possibility of transmission by blood transfusion and organ transplants

Plasmodium

Plasmodium: the Parasite

Apicomplexa Four species of Plasmodium can infect

humans P. falciparum

P. vivax P. ovale

P. malariae

Fatal malaria

Hypnozoites in liver cellsRelapse

The Vector of Plasmodium

Plasmodium: Vector

Anopheles mosquitoes ~ 3,500 species of mosquitoes grouped into 41

genera 430 Anopheles species only 30-40 transmit malaria (i.e., are "vectors")

Human malaria is transmitted only by females of the genus Need blood for the development of eggs

Plasmodium: Life Cycle

Malaria: Symptoms Fever Chills Malaria quartana

3-day cycle P. malariae

Malaria tertiana 2-day cycle P. ovale/vivax (P. falciparum)

Headache Flu-like symptoms Muscle aches Fatigue Anemia Jaundice Enlarged spleen Enlarged liver

http://www.ratsteachmicro.com/Assets/Malaria/jaundice_splen.JPG

Severe Malaria

Cerebral malaria Severe anemia due to hemolysis Hemoglobinuria (hemoglobin in the urine) due to

hemolysis Pulmonary edema (fluid buildup in the lungs) or

acute respiratory distress syndrome (ARDS) Abnormalities in blood coagulation and

thrombocytopenia (decrease in blood platelets) Cardiovascular collapse and shock

Cerebral Malaria Erythrocyte aggregation in

small blood vessels and binding of infected erythrocytes to endothelium

Rosetting of uninfected erythrocytes around infected erythrocytes

Coagulation disorder Activation of endothelial

cells (EC) Increase in inflammatory

cytokines

Abnormal behavior Impairment of

consciousness Seizures Coma

Chen et al., 2000

Malaria: Diagnosis

Microscopy Ring Trophozoite Schizont Gametocyte

Molecular PCR

Patient antibodies

Malaria: Treatment

Is considered medical emergency Must know species and area from where contracted P. falciparum

Oral chloroquine if from non-resistant area Quinine sulfate plus doxycycline, tetracycline, or

clindamycin if from resistant area P. malaria

Chloroquine P. ovale/vivax

Chloroquine Primaquine (hypnozoites)

Malaria: Epidemiology

350-500 million cases of malaria occur worldwide/year

> 1 million people die, most of them young children in sub-Saharan Africa/year

Pregnant women also more vulnerable

Malaria: Distribution of the Disease

Malaria: Distribution of the Vector

Malaria Transmission in the US

Mosquito-Borne Malaria Southern States

"Airport" Malaria Congenital Malaria Transfusion-Transmitted Malaria

Malaria: Prevention

Insecticide-treated bed nets Repeat every 6 - 12 months

Window screens Indoor residual spraying

Acts on mosquitoes resting after blood meal DTT

Source reduction Larval control Destruction of breeding grounds

Threats by Plasmodium

Drug resistance in P. falciparum 11 cases of severe Plasmodium vivax

malaria in Bikaner (western India)

Take Home Message Plasmodium and Trypanosoma have life cycles with major

changes in their life form. Plasmodium and Trypanosoma are transmitted through

biological vectors. Plasmodium infects erythrocytes and causes malaria with fever,

anemia, jaundice, and for P. falciparum possibly cerebral malaria.

American trypanosomiasis is cause by T. cruzi leading to intracellular replication and subsequent inflammation of organs in particular the heart, esophagus and colon (chagas disease).

Resources The Microbial Challenge, by Krasner, ASM Press, Washington DC, 2002. Brock Biology of Microorganisms, by Madigan and Martinko, Pearson Prentice Hall,

Upper Saddle River, NJ, 11th ed, 2006. Microbiology: An Introduction, by Tortora, Funke and Case; Pearson Prentice Hall;

9th ed, 2007. http://www.cdc.gov/malaria/ Francischetti IM et al (2006) Plasmodium falciparum-infected erythrocytes induce

tissue factor expression in endothelial cells and support the assembly of multimolecular coagulation complexes. J Thromb Haemost. 2007 Jan;5(1):155-65.

http://www.cdc.gov/ncidod/dpd/parasites/cryptosporidiosis/default.htm Raether W, Hanel H. (2003) Nitroheterocyclic drugs with broad spectrum activity.

Parasitol Res. 2003 Jun;90 Supp 1:S19-39. Dann SM, Wang HC, et al. (2005) Interleukin-15 activates human natural killer cells to

clear the intestinal protozoan cryptosporidium. J Infect Dis. Oct 1;192(7):1294-302. Elliott DA, Clark DP (2000) Cryptosporidium parvum induces host cell actin

accumulation at the host-parasite interface. Infect Immun. Apr;68(4):2315-22. http://www.dpd.cdc.gov/dpdx/HTML/TrypanosomiasisAmerican.htm Chen Q, Schlichtherle M, Wahlgren M. Molecular aspects of severe malaria. Clin

Microbiol Rev. 2000 Jul;13(3):439-50.