parasites 1: trematodes and...

1

Emerging Infectious DiseasesHSC4933

Lecture 9: Emerging Parasitic Protozoa pt. 2 (Apicomplexans-2: Malaria, Babesia)

Presented by: Matt Tucker, M.S., [email protected]

1HSC4933. Emerging Infectious Diseases 2

• Ch.8 (p. 163 [table 8.2], pp. 167-172, special attention to tables)

• Ch. 11 (pp. 283-86)

• Ch. 14 (pp. 365, 375, 377)

Readings-Lecture 9

HSC4933. Emerging Infectious Diseases 3

• Malaria (Plasmodium spp., Apicomplexan):

Background: http://animal.discovery.com/invertebrates/monsters-inside-me/malaria-plasmodium/

Video: http://animal.discovery.com/videos/monsters-inside-me-malaria-parasite.html

Babesiosis (Babesia spp., Apicomplexan):

Background: http://animal.discovery.com/invertebrates/monsters-inside-me/babesiosis-babesia/

Video: http://animal.discovery.com/videos/monsters-inside-me-babesiosis.html

Monsters Inside Me


• Understand the enormous impact malaria has on global health• Know the various species of Plasmodium that can infect man, and differences

between them. • Identify populations that are especially at risk for malaria and babesiosis• Understand the various facets of malaria that make it difficult to eradicate• Know the general life cycles of malaria and Babesiosis-sources of infection,

infective/diagnostic stages, hosts. How are these cycles different from other parasitic protozoa? For malaria, know key diagnostic differences between P. falciparum and P. vivax

• Be familiar with antimalarial drug resistance and where it is a major problem. What drugs are failing in the world and what are viable alternatives?

• Know aspects of malaria and babesia that make them emerging diseases• Describe why vaccines for malaria are elusive

Learning Objectives


• Phylum Apicomplexa pt. 2

– Class Aconoidasida, Order Haemosporida

Plasmodium spp.

– Class Aconoidasida, Order Piroplasmida

Babesia spp.

Lecture 9: On the Menu


Malaria

http://animal.discovery.com/invertebrates/monsters-inside-me/malaria-plasmodium/







http://animal.discovery.com/videos/monsters-inside-me-malaria-parasite.html









http://animal.discovery.com/invertebrates/monsters-inside-me/babesiosis-babesia/







http://animal.discovery.com/videos/monsters-inside-me-babesiosis.html







2

7

• http://video.nationalgeographic.com/video/player/science/health-human-body-sci/health/malaria-sci.html

Malaria Intro Video

• Malaria is the most important parasitic disease affecting man

• Disease of antiquity– First described in Chinese writings in

2700 B.C.

• Approximately 156 species of Plasmodium which infect various species of vertebrates.– Four species are considered true

parasites of humans (int. host)

• Transmitted by Anopheles mosquitoes (def. host)

Malaria: Background

• World Health Organization estimates– About 3.3 billion people are at risk of malaria– 270 million new infections per year– 1-2 mil children die per yr – 90% of deaths occur in Africa (south of Sahara)

• Occurs in tropical and temperate regions worldwide• Most cases in Africa, followed by Asia and South

America• Dependent upon vector and host, other factors• Global “contraction” from 1900-1950 and

accelerated during 1950-1965

Public Health Impact

• P. vivax– Most common, except in Africa

– Temperate and tropical

– 48h cycle, relapse, hypnozoites,

drug resistance

• P. falciparum– Tropical

– Holoendemic in much of Africa

– 48h cycle, mortality, Tropical regions, drug resistance

– Most lethal

Plasmodium spp. Facts

• P. malariae– Global, but patchy 72h cycle

• P. ovale– Mainly in tropical Africa and

Oceania

– 48h cycle, relapse

• P. knowlesi– New emerging species in

humans

– Malaysia, 24 h. cycle


Malaria: Life cycle

See animated life cycle link in BB

Mosquito is

definitive host

Man is

intermediate

host

12

Worldwide distribution of malaria: 2009

Malaria is present in 109 countries and territories.

http://video.nationalgeographic.com/video/player/science/health-human-body-sci/health/malaria-sci.html










3


• Infants & young children (under 5 yrs. old)• Non-immune pregnant women

– High rates of miscarriage and cause over 10% of maternal deaths (soaring to a 50% death rate in cases of severe disease) annually.

• Semi-immune pregnant women risk severe anemia and impaired fetal growth even if they show no signs of acute disease. – 200,000 of their infants die annually as a result of malaria

infection during pregnancy.

• HIV-infected pregnant women are also at increased risk. • Non immune (tourist)

Who does malaria affect?


• Africa’s GDP today would be up to 32 percent greater if malaria had been eliminated 35 years ago.

• Malaria-endemic countries are among the world’s most impoverished.• In Thailand, malaria patients pay nine times their average daily wage for

care.• A malaria-stricken family spends an average of over one quarter of its

income on malaria treatment, as well as paying prevention costs and suffering loss of income.

• Malaria-afflicted families on average can only harvest 40% of the crops harvested by healthy families

• Children experiencing cerebral malaria and malaria accompanied by complex seizures– 24% of children in both malaria groups had significant cognitive impairment.– Crude estimates: 128,000 children a year develop epilepsy following malaria.– 250,000 develop significant cognitive impairment

Malaria – the cost


• Substandard, counterfeit drugs

• Drug resistance

• Insecticide resistance

• Deterioration of public health services

• Environmental changes

• No vaccine

Why is it getting worse?


Anopheline Mosquitoes• Approximately 430 known species, 30-50 transmit

malaria • Life cycle – 7 to 20 days (egg to adult)

– Females mate once and lay 200-1000 eggs in 3-12 batches over a lifetime

– Find their host by chemical and physical stimuli– Average life span of adult mosquito < 3 week

Malaria development• Development in mosquito (extrinsic incubation

period)=7 to 12 days• Each male & female gametocyte produce >10,000

sporozoites

• Important vector species begin entering houses in the early evening, often at sunset.

• Important vector species often begin leaving houses just before or during sunrise.

Mosquitoes and Malaria


• Determines presence of larval habitats and abundance of vectors

• Influences distribution and abundance of humans (mosquito-human-mosquito cycle of transmission)

• Factors that influence presence, abundance and longevity of mosquitoes. – Temperature– Rainfall– Relative Humidity– Topography

Altitude, elevation Soil Type Land cover (vegetation)

Ecology and malaria transmission


Distribution of malaria vectors

4


Malaria: 1900-2002


• Malaria was endemic in the US until the late 1940's.

• Most of the transmission occurred in the southeastern states.

• Control efforts conducted by the state and local health departments, supported by the federal government, resulted in the disease being eradicated by 1949.

• Such measures included drainage, removal of mosquito breeding sites, and spraying (occasionally from aircrafts) of insecticide

Malaria in the U.S.


• Constant risk of reintroduction to U.S.• Between 1957-2003, in the United States, 63

outbreaks of locally transmitted mosquito-borne malaria have occurred

• Local mosquitoes become infected by biting persons carrying malaria parasites (acquired in endemic areas) and then transmit malaria to local residents

• 11 outbreaks involving 20 cases of probable locally acquired mosquito-transmitted malaria have been reported to CDC since 1992– Palm Beach County, FL.

1996: 2 outbreaks July-August 2003: 7 cases of locally acquired P. vivax

Malaria in the United States


Recent Stats


• Prevention of malaria in travelers• Ensure prompt diagnosis and treatment of

all infected persons• Containment of local outbreaks of malaria• Conduct surveillance of malaria cases• Sensitize local communities to the risk of

malaria• Encourage personal protection measures

to prevent mosquito bites• Conduct vector control activities• During 1963-1999, 93 cases of

transfusion-transmitted malaria were reported in the United States

Minimizing Risk of Re-emerging malaria in U.S.


• Infects long-tailed macaques• Previously diagnosed as P. malariae in

humans• 24 hour cycle, higher parasitemia than P.

malariae• Exists primarily in Malaysia• 2008 study: P. knowlesi DNA was detected in

27.7% samples from Sarawak hospitals, 83.7% from Sabah, 5 from Pahang

• Similar infections have been found in Thailand, the Philippines, and Singapore

• Economic exploitation of the forest is perhaps bringing monkeys, mosquitoes and humans into increased contact.

Plasmodium knowlesi

5


P. knowlesi: Emerging Disease


• The first symptoms of malaria after the pre-patent period (period between inoculation and detectable stages: when the sporozoites undergo schizogony in the liver) are called the primary attack. It is usually atypical and may resemble any febrile illness.

• Headache• Feeling of weakness and exhaustion• Aching in bones, limbs, or back• Loss of appetite• Desire to stretch or yawn• Nausea and vomiting

MALARIA: Prodromal symptoms


PREPATENT PERIOD INCUBATION PERIOD

P. falciparum 11 - 14 days 8 - 15 days

P. vivax 11 - 15 days 12 - 20 days

P. ovale 14 - 26 days 11 - 16 days

P. malariae 3 - 4 weeks 18 - 40 days

Prepatent & incubation periods of human malaria


• The asexual intra-erythrocytic stage causes all pathophysiological processes– Parasite and red cell material released with schizont rupture, resulting in chills

and high grade fever.

• Paroxysms– Episodes of chills and fever – Begins with cold stage of up to 1 hr duration-Profuse sweating as body

temperature falls – Fever stage follows rapidly for 6-12 hr

Nausea, Vomiting, Rapid pulse

• The pattern of intermittent chills/fever mirrors the synchronized parasite development in an infected person’s blood (48 or 72 hours)– Benign tertian: P. vivax– Malignant tertian : P. falciparum– Quartan : P. malariae

• Recrudescences= reinfection as result of parasites not being cleared• Relapses= result of P. vivax and P. ovale stages that hide in liver

Uncomplicated Malaria

Severe Malaria and other manifestations

• Cerebral malaria, with abnormal behavior, impairment of consciousness, convulsions, seizures, coma, or other neurologic abnormalities

• Severe anemia due to hemolysis(destruction of red blood cells)

• Hemoglobinuria (hemoglobin in the urine) due to hemolysis (Blackwater fever), renal failure

• Pulmonary edema or acute respiratory distress syndrome (ARDS)

• Abnormalities in blood coagulation and thrombocytopenia (decrease in blood platelets)-bleeding/clotting disorders

• Cardiovascular collapse and shock• Metabolic acidosis• Hyperparasitemia

Severe disease with life-threatening complications- P. falciparum

• Hypoglycemia• Septicemia• Gastrointestinal bleeding• Pneumonia


• The clinical presentation can vary substantially depending on the infecting species, the level of parasitemia, and the immune status of the patient.

Don’t memorize, but know spectrum of

severity and how different from

uncomplicated malaria


• Most common clinical presentation of severe malaria in man

• Definition– Parasitized red blood cells (PRBCs) adhere to the

cerebral microvasculature, causing blockage of the blood's pathway - stops blood flow, leading to a shortage of oxygen and nutrients those areas of the brain (hypoxia).

– Unrousable coma– Other causes of encephalopathy have been excluded

(viral infections, head injury, etc)– Mortality rate of ~22% despite treatment

P. falciparum- Cerebral malaria

6


• In sub-Saharan Africa, there are 400,000 cases of severe maternal anemia and 75,000-200,000 infant deaths annually.– 10,000 maternal deaths per year.

• Adverse effects on both mother and fetus, including maternal anemia, fetal loss, premature delivery, intrauterine growth retardation, and delivery of low birth-weight infants.

• It is a particular problem for women in their first and second pregnancies and for women who are HIV-positive.

• High transmission area vs. low transmission area: anemia and birth outcomes differ

Pregnancy and Malaria


• Elicit a good travel history• Ethnic origin of patient or family

members• History of previous episodes of malaria• Blood transfusions or i.v. drug use• Occupation• Giemsa stained blood smears• PCR• Dipstick antibody tests to differentiate

species• DNA staining

Diagnosis: Important facts

Thick and thin blood smears


P. falciparum• Mostly rings or gametocytes present

– Trophozoites and schizontscytoadherence

• Crescent shaped gametocytes• 24 to 36 merozoites (if schizont present)• No Schuffner’s stippling• Infected erythrocyte not enlargedPlasmodium vivax• All stages present• Infected erythrocyte enlarged• Schuffner’s stippling (dots) • 12 to 24 merozoites• Oval gametocyte almost fills erythrocyte

Diagnostic criteriaRing stages Gametocyte


P. falciparum vs. P. vivax

Notice the differences?

35

• P. falciparum -only immature, ring forms circulate in the peripheral blood

• Mature erythrocytic forms (trophozoites and schizonts) bind to vascular endothelium through ’knobs’ that enable them to be sequestered in the venules and avoid elimination by the spleen.

• Cerebral malaria• Rosetting

– Erythrocytes infected with mature asexual parasites adhere to uninfected erythrocytes

– Possible involvement in pathophyiology of severe disease

• Placenta and parasite adhesion– Large numbers of infected erythrocytes sequestered

on the maternal side of the placenta.

• Pfemp1, antigenic variation- mech for avoiding Immune Reponse

P. falciparum Adhesion and Disease


• Treatment varies according to the infecting species, the geographic area where the infection was acquired, and the severity of the disease

• Treatment for malaria should not be initiated until the diagnosis has been confirmed by laboratory investigations.

• Treatment of infection– Acute, uncomplicated malaria– Severe or cerebral malaria

• Radical cure• Prophylaxis

– Causal, Suppressive – Post-exposure

• Intermittent Presumptive Treatment (IPT)– Infants (IPTi)– Pregnancy (IPTp)

Antimalarial Treatment

7


• Choose appropriate antimalarial drug and route of administration

• Follow blood glucose carefully

• Administer I.V. fluids for shock and hypovolemia

• Administer oxygen by nasal catheter

• Consider replacing erythrocytes for hematocrit of 30 or parasitemia > 10%

Treatment: Severe Malaria


• Quinine, intravenous– Slow infusion avoids cardiovascular toxicity and

hypoglycemia

• Quinidine gluconate, intravenous– Very effective, but adverse cardiac events

• Artemisinin derivatives– Rapidly acting– Several derivatives and formulations

Artesunate drug of choice for severe disease– Compassionate use IND in US (via CDC)– >30% more effective than quinine in preventing death in cerebral

malaria

Treatment- Cerebral Malaria


DRUG PROBLEMS

Artemisinin Recrudescence, Neurotoxicity

Atovaquone Resistance

Azithromycin Limited efficacy

Chloroquine Resistance

Doxycycline Phototoxicity, GI intolerance

Fansidar Resistance, Allergic Rxns

Halofantrine Cardiotoxicity

Mefloquine Resistance, Psychiatric effects

Primaquine Therapeutic Index, Resistance?

Proguanil Resistance, Mouth ulcers

Quinidine gluconate Going off the market?

Quinine Resistance, Tinnitus

Problems with antimalarial drugs Time to Development of Resistance to Antimalarial Drugs

1940

Chloroquine

16 years

Fansidar

6 years

Mefloquine

4 years

Atovaquone

6 months

1950 1960 1970 1980 1990


• Discovered during WW II• Effective against all Plasmodium spp.• CQ is trapped in the parasite food

vacuoles where it is toxic– Inhibits polymerization of hemazoin

and free heme kills the parasite

• ‘Magic bullet’ that was basis of 1960s malaria eradication campaign

• Resistance first emerged in early ’60s in S. America and SE Asia– Resistance conferred by complex

mutations in a Plasmodium falciparum chloroquine resistance transporter gene (pfcrt)

– Big problem in Africa, Asia

Chloroquine (CQ)


Spread of chloroquine resistant Plasmodium falciparum

8


• Prophylaxis - in CQ & multi-drug resistant regions

• Treatment - in CQ & multi-drug resistant regions

– Combined with artesunate to treat mefloquineresistant malaria in SE Asia

– For P. vivax or P. falciparum

Mefloquine (Lariam)


Artemisinin (Qinghaosu)

• Harvested from the Chinese herb Artemesia annua (sweet wormwood)

• Many derivatives

• 200 BC-China: recognized as herbal remedy of hemorrhoids and fever

• 1972 identified as active constituent of Artemesia annua

• 1999 Artemisinin combination therapy (ACT) O

O

O O

O

C15H22O5

• Rapid relief from symptoms and fast clearance times• Broad stage specificity with gametocidal activity• Cheap alternative to other drugs • Not recommended for prophylaxis because of short

elimination time• Animal studies: neurotoxicity at high doses and also death of

embryos, and morphological abnormalities in early pregnancy• Can be combined with other drugs for effective treatment

(ACT)• Only treatment for severe malaria besides quinine• Resistance not reported

Artemisinin Treatment of Malaria

• WHO issued new guidelines on malaria treatment and requested pharmaceutical companies to end the marketing and sale of "single-drug" artemisinin malaria medicines, in order to prevent malaria parasites from developing resistance to this drug (1-20-06 Press release).

• The artemisinin component– Reliably efficacious, rapidly effective

• Partner drug(s)– Ensures high cure rate– Protects artemisinin– Very well tolerated– No resistance– Reduces gametocyte carriage– Reduces de-novo resistance to partner– Prophylactic activity

Artemisinin Combination Therapy (ACT)


• Treatment of depends on many factors including disease severity, the species of malaria parasite causing the infection, and the part of the world in which the infection was acquired. – Planning, Case history very important

• Think about the probability that the organism is resistant to certain antimalarial drugs.

• Additional factors such as age, weight, and pregnancy status may limit the available options for malaria treatment.

• Guidelines for U.S. Travelers– http://www.cdc.gov/malaria/diagnosis_treatment/treatment.html

So, how do you correctly treat a patient?

Interactive world map for malaria prevalence/risk:

http://apps.who.int/tools/geoserver/www/ith/index.html

CDC list of malaria countries and risk:

http://wwwnc.cdc.gov/travel/yellowbook/2010/chapter-

2/malaria-risk-information-and-prophylaxis.aspx

http://www.cdc.gov/malaria/diagnosis_treatment/treatment.html

http://www.cdc.gov/malaria/diagnosis_treatment/treatment.html

http://apps.who.int/tools/geoserver/www/ith/index.html

http://wwwnc.cdc.gov/travel/yellowbook/2010/chapter-2/malaria-risk-information-and-prophylaxis.aspx













9


• Reduce the transmission of the disease by mosquito control

• Mosquito nets treated with long-lasting insecticide, a very cost-effective method

• Indoor residual spraying of insecticides.

• Repellents• Drugs- all groups- kill

parasites• Vaccines -block infection, kill

parasite• Pregnant women

Prevention


• Intermittent preventive treatment (IPT)-antimalarial treatment given at regular intervals during pregnancy,

– Two to three doses of sulfadoxine-pyrimethamine (SP) administered to a pregnant woman through antenatal care services. This protects pregnant women from possible death and anemia and also prevents malaria-related low birthweight in infants

• Insecticide-treated bed nets (ITN), indoor residual spraying

• Febrile malaria case management.

• Malaria prevention is particularly challenging in HIV-infected women, who might constitute up to 40% of the antenatal population in southern Africa.

– HIV-infected pregnant women are more likely to fail antimalarial treatment and require three or more doses of IPTp

Prevention and Control of Malaria During Pregnancy


• Pre-erythrocytic stages- directed against sporozoites and/or liver stages (prevent blood-stage infection)

• Against asexual blood stages are designed to reduce clinical severity

• Against mosquito stages are designed to halt development in the mosquito (transmission-blocking vaccines)-

• Best vaccine candidate: RTS,S vaccine (pre-erythrocytic)- up to 50% protection in clinical trials (in stage three clinical trials, now)

• Major problem: antigens are constantly changing and developing a vaccine against these varying antigens is very difficult

Vaccines


• Requires an integrated approach– Vectors– Proper antimalarial drugs– Access to prompt, medical treatment

• Factors contributing to disease– Reservoir-prevalence in humans– Vector-suitability of local anopheline as hosts-breeding

preferences, flight/resting behavior, abundance, temp., rainfall, humidity,

– New hosts-nonimmune hosts– Local climattic conditions

• Local geographical and hydrogeographical conditions, human activities that can determine availability of and accessibility to mosquito breeding areas

Control: Mechanisms and Challenges


• Transgenic mosquitoes– Mosquitoes refractory to mouse

malaria in lab experiments- transgenic malaria-resistant mosquitoes have a selective advantage over nontransgenic mosquitoes?

– Sterile male mosquitoes released into a given environment

– Male mosquitoes carrying lethal genes causing death of newborns very young

– Disadvantages: Could resistant mosquitoes be useful in

the wild? They must survive better than non-resistant mosquitoes even when not exposed to malaria.

Not shown to work in Plasmodium falciparum

Genetic engineering and Malaria

Blocking transmission of sporozoites through the gut wall and into the salivary glands.


• Zoonotic disease maintained by the interaction of tick vectors, transport hosts, and animal reservoirs.

• More than 100 species have been reported, only a few have been identified as causing human infections.

• Babesia microti and Babesia divergens have been identified in most human cases

• Ticks of the family Ixodidae transmit B. microti(and Lyme disease).

• Transplacentally or perinatally acquired (congenital) babesiosis have been reported.

• Blood transfusions-emerging problem

Babesia spp.

10


Life Cycle: Babesia


• Worldwide, but little is known about the prevalence of Babesia in malaria-endemic countries, where misidentification as Plasmodiumprobably occurs.

• Endemic areas are regions of tick habitat, including the forest regions of the Northeastern U.S. and temperate regions of Europe.

• In Europe, most reported cases are due to B. divergens and occur in splenectomized patients.

• In the U.S., B. microti is the agent most frequently identified (Northeast mostly, less common in Midwest), and can occur in nonsplenectomizedindividuals.

• High number of asymptomatic infections• The first U.S. case of babesiosis was reported on Nantucket Island in

1966. Between 1968 and 1993, more than 450 cases of Babesia infections were confirmed in the United States. – An increasing trend over the past 30 years may be the result of restocking of

the deer population, curtailment of hunting, and an increase in outdoor recreational activities.

Geographic Distribution


• Fever, chills, sweating, myalgias, fatigue, hepatosplenomegaly, and hemolytic anemia.

• Symptoms typically occur after an incubation period of 1 to 4 weeks, and can last several weeks. The disease is more severe in patients who are immunosuppressed, splenectomized, and/or elderly.

• Infections caused by B. divergens tend to be more severe (frequently fatal if not appropriately treated) than those due to B. microti, where clinical recovery usually occurs.

Laboratory Diagnosis:• Microscopic examination of thick and thin blood smears

stained with Giemsa.• Isolation of the organisms by inoculation of patient

blood into hamsters or gerbils• Treatment: Clindamycin plus quinine or atovaquone

plus azithromycin

Disease, dx, tx


• Since 1979,over 80 cases of transfusion-associated babesiosis have been reported in the US (FDA)

• Currently, the blood supply is not screened for Babesia• Donors are deferred if they have a fever at the time of donation or report a

history of Babesia infection, but this practice alone is unable to prevent asymptomatic individuals with low levels of parasitemia from serving as donors.

Babesia and blood transfusion: U.S.

• Seven cases of transfusion-associated babesiosis have been identified among New York City (NYC) residents since September 2008; this is a notable increase over baseline as previously an average of one to two transfusion-associated cases were reported annually;


• Avoid tick exposures– Tick infested areas (high tick season

between May and September)– Cover skin with light clothing, searching

for ticks after being outdoors and removing discovered ticks from the skin.

– Applying bug repellent with DEET

• Eradication?– Preventative measures seem to be more

recommended over vector control.– Due to the relatively low prevalence of

the disease and the presence of several reservoirs, Babesiosis is currently not a candidate for vaccine prevention.

Prevention

parasites 1: trematodes and...

Documents