Trypanosomiasis/African trypanosomiasis

A zoonotic, systemic, parasitic infection. It is a major cause of morbidity and mortality in low-wealth areas of Latin America.
What is trypanosomiasis?
American trypanosomiasis, Chagas’ disease.
What are other names for trypanosomiasis?
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Trypanosoma cruzi (protozoan hemoflagellate).
What is the agent of trypanosomiasis?
What is the characteristic appearance of the agent of trypanosomiasis?
A “C” or “U”-shaped appearance.
What is the characteristic appearance of the agent of trypanosomiasis?
What is the vector for trypanosomiasis? Where within the vector does the parasite reside?
The reduvid bug; the hindgut.
What is the vector for trypanosomiasis? Where within the vector does the parasite reside?
The reduvid bug resides in thatched roof huts and takes blood meals from sleeping humans. While taking a blood meal, the bug defecates on the skin. Many humans are hypersensitive to reduvid bug saliva, and scratch the bite site with the parasite-contaminated feces, inoculating the wound.
Describe the process by which the vector for trypanosomiasis infects humans.
The trypanosome deposited on the skin from the reduvid bug invades local cells and transforms into __________, which multiply, lyse the host cell, and finally differentiate into ____________.
amastigotes; trypomastigotes
The trypanosome deposited on the skin from the reduvid bug invades local cells and transforms into __________, which multiply, lyse the host cell, and finally differentiate into ____________.
No; dogs are common hosts and contribute a significant challenge to the parasite’s eradication.
Are humans the only reservoir for trypanosomiasis parasites?
False; acute Chagas’ disease is usually mild with a case fatality rate < 5%.
T/F: Acute Chagas’ disease is a severe and commonly fatal infection.
1) Localized infection creates an inflammatory reaction of varying intensity (may be asymptomatic).
2) Parasitemia follows, with fever, malaise, facial/extremity edema, and possibly generalized lymphadenopathy, hepatosplenomegaly, and/or CNS involvement.
3) Resolution finishes with the indeterminate phase, with vague gastrointestinal or cardiac symptoms, if not altogether asymptomatic. Notably, a lifelong low-grade parasitemia may persist.
Describe the presenting course of acute trypanosomiasis.
An erythematous, subcutaneous nodule characteristic of acute Chagas’ disease occurring at the site of T. cruzi infection.
What is a chagoma?
What is Romaña's sign?
Edema of the eyelids and conjunctivitis following oral, nasal or ocular inoculation of T. cruzi, characteristic of acute Chagas’ disease.
What is Romaña’s sign?
False; the heart is the most commonly and most severely affected organ.
T/F: Chronic trypanosomiasis most severely affects the liver.
Symptoms are thought to be due to a chronic Th1-mediated inflammatory response with fibrosis of the affected tissues.
What is the suspected pathogenesis of chronic Chagas’ disease?
years, even decades
Chronic trypanosomiasis occurs ______________ after the acute disease.
1) Dilated cardiomyopathy (biventricular enlargement and thinning of walls)
2) “Megadisease” (megacolon and/or megaesophagus)
What complications may arise from chronic Chagas’ disease?
Heart involvement may result in dysrhythmias and thromboembolism. Colonic/esophageal involvement may result in “megadisease” (megacolon, megaesophagus), causing dysphagia, chronic regurgitation, aspiration and severe constipation.
What are the possible symptoms of chronic Chagas’ disease?
CMI
Immunity to T. cruzi is primarily ___-mediated.
infecting non-immune cells, leading to a lifelong sporadic, low-grade parasitemia.
T. cruzi causes a lifelong parasitemia by:
1) Clinical presentation
2) Direct examination of blood smear (revealing motile parasites)
3) Serologic testing (for chronic disease)
4) Xenodiagnosis (detects parasite)
How is Chagas’ disease diagnosed?
Nifurtimox and benzidiazole (effective in 50% of cases).
How is Chagas’ disease treated?
1) Avoid contact with reduvid bugs.
2) Avoid infected blood/tissue.
How can Chagas’ disease be prevented?
African sleeping sickness.
What is another name for African trypanosomiasis?
Trypanosoma brucei.
What is the agent of African trypanosomiasis?
What is the characteristic appearance of the agent of African trypanosomiasis?
An “S”-shaped protozoan, ranging from “long and slender” to “short and stumpy.”
What is the characteristic appearance of the agent of African trypanosomiasis?
T. brucei gambiense and T. brucei rhodesiense.
What are the two relevant subspecies of T. brucei?
T. brucei gambiense: West African distribution, chronic (years-long) course.
T. brucei rhodesiense: East African distribution, acute (weeks to months) course.
Both are fatal if untreated.
What are the primary differences between T. brucei subspecies?
What is the vector of African trypanosomiasis?
The tsetse fly.
What is the vector of African trypanosomiasis?
1) Parasites injected into blood after bite of tsetse fly.
2) Systemic spread.
3) Long slender form of parasite multiplies, short stumpy form (adapted to insect) does not.
4) Another tsetse fly takes a blood meal filled with parasites.
Describe the life cycle of T. brucei.
1) The primary lesion stage.
2) The hemolymphatic stage.
3) The meningoencephalitic stage.
What are the three phases of African trypanosomiasis?
No; after the primary lesion and initial parasitemia, the infection may be cleared or aborted by the immune system before progression to the hemolymphatic stage.
Do all primary lesions progress to African trypanosomiasis?
An asymptomatic period, or an indurated chancre at the bite site which slowly resolves. An asymptomatic low-grade parasitemia follows for weeks to months.
What are the symptoms of the primary lesion of African trypanosomiasis?
Parasites invade the lymphatics, then release into the bloodstream, causing symptoms. While febrile, trypanosomes are abundant in the blood. After defervescence, parasites are rarely found in blood.
Describe the pathogenesis of the hemolymphatic stage of African trypanosomiasis.
1) 3-7 Day febrile periods (trypanosomes abundant in blood)
2) Asymptomatic intervals (trypanosomes rarely present)
3) possibly, an immune-mediated rash
4) possibly, Winterbottom’s sign
What are the symptoms of the hemolymphatic stage of African trypanosomiasis?
What is Winterbottom's sign?
Prominent posterior cervical lymph nodes, characteristic of African trypanosomiasis, indicating cerebral infection.
What is Winterbottom’s sign?
1) Kerandel’s sign
2) Increasing lethargy and apathy (usually 6-12 months post-infection)
3) Progressive meningoencephalitis, deterioration into unresponsiveness (“sleeping sickness”)
4) Coma
5) Death
What are the symptoms of meningoencephalitic African trypanosomiasis?
Delayed and prolonged sensation to pain, characteristic of meningoencephalitic African trypanosomiasis.
What is Kerandel’s sign?
Variant surface glycoprotein (VSG).
What is the “virulence factor” of T. brucei trypanosomes?
antibody
Immunity to African trypanosomiasis is ___-mediated.
As IgM-antibodies are created by the host against T. brucei’s variant surface glycoprotein (VSG), the parasite retreats intracellularly to mutate its VSG, for which it has over 1000 genes. Upon release, a new parasitemia occurs, necessitating a renewed IgM-mediated response.
Explain how T. brucei is capable of causing a long-lasting parasitemia.
1) Clinical presentation
2) Direct examination of blood, lymph node biopsy, bone marrow, or CSF
3) Serological tests
How is African trypanosomiasis diagnosed?
Prior to CNS involvement: suramin or pentamidine
After CNS involvement: malarsoprol or eflornithine
Treatments are toxic and not always effective.
How is African trypanosomiasis treated?
Avoid the tsetse fly.
How can African trypanosomiasis be prevented?
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