Exam #7: Parasitic Infections of the Circulatory, RES, & Lymphatic System Flashcards
What is Africacn Trypanosomiasis?
African Sleeping Sickness
What organism causes African Sleeping Sickness?
Trypanosoma brucei
What is the insect vector for African Sleeping Sickness?
Tsetse fly
What is the animal reservoir of Trypanosoma brucei?
Cattle
What are the 2 subspecies of Trypanosoma brucei?
T. brucei gambiense= human-to-human spread ONLY
T. brucei rhodesiense= human-to-human & animal-to-human spread
What are the symptoms of early African Sleeping Sickness?
In early stage infection, organisms are in the blood & peripheral lymph nodes leading to:
- Fever
- Myalgia
- Chills
- Lymphadenopathy
What are the late symptoms of African Sleeping Sickness? Which form of Trypanosomiasis leads to late stage faster?
Late stage infection is characterized by invasion of the CNS
- Headache
- Seizures
- Tremors
- Encephalitis
- Periods of sleeplessness & lethargy
- Coma
- Death
Eastern African form leads to CNS involvement in 3-4 weeks vs. weeks to years for the West African form
How is Trypanosoma brucei infection diagnosed?
Detection of parasites in blood smear, lymph nodes aspirates, or CSF
Describe the antigenic variation seen in African Sleeping Sickness.
- Trypanosoma brucei is coated with a surface glycoprotein
- 150 genes encode different glycoproteins
- We produce antibodies to these glyocproteins, but the organisms rapidly switch their surface antigenicitiy (glycoprotein), preventing absolute clearance
How is African Sleeping Sickness treated?
Melarsoprol–“If the parasite doesn’t kill you, the treatment will.”
DFMO (difluoromethylornithine)–much greater efficacy than melarsoprol that is now made by Doctor’s Without Borders
What is Chagas disease?
American Trypanosomiasis that is endemic to South and Central America
What organism causes Chagas disease?
Trypaosoma cruzi
Describe the lifecycle of Trypanosoma cruzi.
Fecal pellet
Blood
What is the zoonic host of Trypaosoma cruzi?
Reduviid Bug
What are the symptoms of Chagas Disease?
- Chagoma- a hardened red nodule
What is Romana’s sign?
Chagoma of the eye
Describe the acute phase of Chagas Disease. What symptoms are seen in this stage?
Fever
Malaise
Myalgia
Hepatosplenomegaly
Describe the intermediate phase of Chagas Disease.
- This is the asymptomatic phase of the disease; there are few parasites in blood & high levels of Ab
- This is where most infected individuals remain
What are the characteristics of chronic phase Chagas Disease?
- Infection of cardiac muscle & myeneteric plexus
- Develops years to decades after infection
- Cardiac & GI involvement is seen including: Myocarditis, Megacolon, and Megaesophagus
How is Chagas Disease diagnosed? How does detection in the acute phase differ from the chronic phase?
Acute phase= paraistes in peripheral blood
Chronic= serology
*****Note that as with many tropical/ exotic disease, a travel history that is consistent with exposure aids in diagnosis
What are the three major forms of Leishmaniasis? What species are responsible for these different infections?
1) Cutaneous
2) Mucocutaneous
3) Visceral= L. donovani, L. infantum, & L. chagasi
What is the vector for Leishmaniasis?
Infected female sand flies
What cells are infected by Leishmaniasis?
Phagocytes
What patient populations are most susceptible?
Leishmaniasis has increasingly been recognized as an “opportunistic” pathogen in HIV+ individuals, primarily in the Mediterranean
What are the symptoms of visceral Leishmaniasis?
Leishmaniasis involves dissemination of parasites throughout the RES; they can be found in macrophages of the liver, spleen, & bone marrow. Symptoms include:
- Irregular low grade fever
- Weight loss
- hepato-splenomegaly
- “wasting”
*Note that systemic immunosuppression is common with full blown disease, and death is typically caused by secondary bacterial or viral infection
Describe the mechanism of visceral Leishmaniasis.
- Dissemination of parasites throughout the reticuloendothelial system
- Parasites can be found in the marcophages of liver, spleen, bone marrow
*****Note that within an infected individual, only intracellular forms are found; therefore, antibodies afford little or no protection
What part of the immune system resolves Leishmaniasis?
Resolution of infection is dependent on cell-mediated immunity
How is Leishmaniasis controlled? How is it treated?
Control= eliminating the vector i.e. sand fly
Treatment= high toxic heavy metal compounds
What is the most important of all the tropical & parasitic diseases?
Malaria
What causes malaria?
Plasmodium
What species of Plasmodium cause most cases of Malaria?
P. falciparum
P. vivax
Describe the lifecycle of Plasmodium.
- Transmission occurs by the bite of an infected mosquito
What two species of Plasmodia can lay dormant in the liver?
P. vivax
P. ovale
What is the major clinical presentation of Malaria? What is the major complication of malaria?
Malaraia paroxysm, which is associated with the synchronous release of merozoites & the lysis of RBCs, leading to cycles of flu-like symptoms including:
- Fever
- Chills
- Headache
- Muscle ache
Complication= anemia
Describe the duration and pattern of paroxysm for the different species of Plasmodia.
P. vivax & ovale= Q48 hours
P. malariae= Q72 hours
P. falciparum= Q48 hours
Thus, the most common types of malaria recur every 48 hours
What are the three mechanisms involved in the pathogenesis of anemia?
-
**Anemia is the most common complication of malaria. The asexual stage of the parasite destroys RBCs each time it completes a cycle of replication. Three mechanisms in the pathogenesis of anemia include:
1) RBC lysis
2) Suppression of erythropoiesis by cytokines
3) Destruction of RBC’s by spleen
What species causes the most severe and frequent anemia?
P. falciparum
- Infects both young and old RBCs
- Highest parasitemia
What cell type do P. vivax & P. ovale infect?
Reticulocytes; thus, these species of plasmodium cause a less severe anemia compared to P. falciparum
Aside from anemia, what are other complications of malaria?
- Splenomegaly
- Hypoglycemia/ lactic acidosis*
- Microvascular sequestration*
- Cerebral malaria
*Note that these are specific to P. falciparum
How is malaria diagnosed?
1) Recognize syndrome
2) Travel history
3) Blood smear positive for parasites
What are the features of a positive blood smear for malaria?
“Purple banana”
Plasmodium falciparum
How is Malaria prevented?
- Eradicate the insect vector/ breeding ground
- Prophylaxis for travelers
*Note that vaccine trials have been disappointing and that drug resistance is a major concern
What is Babesiosis?
A form of malaria seen in the US, which is most common in New England, the Upper Midwest, & California
How is Babesiosis transmitted?
Tics
What are the symptoms of Babesiosis?
Symptoms developed 1-8 weeks after tic bite and include:
- Fever, chills, myalgia
- Hemolytic anemia
What patient population is highly susceptible to Babesiosis?
- Elderly
- Asplenic
- Immunosuppressed
What cytological feature is diagnostic of Babesiosis?
Maltese Cross
What is Filariasis?
- Filariasis is also known as “elephantiasis,” and is caused by filarial nematodes
- This is a mosquito transmitted helminth infection
What helminths cause Filariasis?
Wuchereria bancrofti
Brugia malayi
*Note that the adult form of both of these worms reside within the lumen of lymphatic vessels
How is Filariasis transmitted?
- Bite of infected mosquitoes
- Larvae from bite wound enter lymphatics & mature into adults
*Note that this typically occurs in the lymphatics of the upper & lower extremities, and male genitalia
What are the symptoms of acute Filariasis?
Fever
Chills
Lymphadenitis
- Painful swelling may last for weeks & frequently recurs
What proportion of the patients with Filariasis develop “elephantiasis?”
A small percentage
How is Filariasis diagnosed?
Observing microfilariae in blood smears that are collected at night.
What is Schistosomiasis?
Schistosomiasis is also known as bilharzia or “snail fever”, and is a parasitic disease carried by fresh water snails.
