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Cardiovascular System Infection - Myocarditis
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Definition
Myocarditis is inflammation of the heart muscle(myocardium)
It resembles a heart attack but coronary arteries are notblocked
Myocarditis is most often due to the infection by
1- Common viruses, such as Parvovirus B19 2- Non-viral pathogens (less commonly)
Borrelia burgdorferi (Lyme disease)
Trypanosoma cruzi (Chagas disease)
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Myocarditis could be caused by hypersensitivityresponse to drugs
The definition of myocarditis varies, but the central
feature is an infection of the heart, with aninflammatory infiltrate, and damage to the heartmuscle, without the blockage of coronary arteries thatdefine a heart attack (myocardial infarction) or other
common non-infectious causes.
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Myocarditis may or may not include death (necrosis)of heart tissue
It may include Dilated cardiomyopathy
Dilated cardiomyopathy or DCM is a condition in whichthe heart becomes weakened and enlarged, and cannotpump blood efficiently
The decreased heart function can affect the lungs, liver,and other body systems
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Dilated cardiomyopathy or DCM Gross pathology of idiopathic cardiomyopathy
Opened left ventricle of heart shows a thickened, dilated left ventricle withsubendocardial fibrosis manifested as increased whiteness of endocardiumautopsy
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Cellular infiltration and cardiac necrosis
Histopathological image of myocarditis at autopsy in a patient withacute onset of congestive heart failure due to viral infection.
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Myocarditis is associated with an autoimmune reaction
Streptococcal M protein and Coxsackie B virus have regions(epitopes) that are similar to cardiac protein myosin
M protein is a virulence factor that can be produced bycertain species of Streptococcus
M protein is strongly anti-phagocytic protein and is amajor virulence factor
Cross-reactivity of anti-M protein antibodies with heartmuscle is the basis for Rheumatic fever
After the virus is gone, the immune system may attack
cardiac myosin
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Causes of Myocarditis In Europe and North America, viruses are common cause
of myocarditis
Worldwide, however, the most common cause is Chagasdisease, an illness endemic to Central and South Americathat is due to infection by the protozoan Trypanosomacruzi
Transmission of trypanosomiasis occurs when the Wingedbug of the genus Triatoma deposits feces on the skinsurface and subsequently bites; the human host thencontaminating the bite area, with infected feces
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Photomicrograph of Giemsa-stainedTrypanosoma cruzi (CDC)
Triatoma infestans
Trypansoma cruziparasite in a thin blood
smear (CDC Photo)
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Rhodnius prolixus nymphs and adult
Rhodnius prolixus
Triatoma infestans Panstrongylus geniculatus
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Pathogenesis of Trypanosoma cruzi
Human American trypanosomiasis, or Chagas disease, is a fataldisease of humans
The disease has two forms, a trypomastigote found in humanblood, and an amastigote found in tissues
The acute form usually goes unnoticed and may present as alocalized swelling at the site of entry
In the chronic stage, 10 to 20 years after infection, the parasiteinvades the myofibrils of the heart causing myocarditis
The gradual autoimmune destruction of heart myocardium leadto cardiac enlargement and arrhythmias, and heart failure
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Signs and symptoms
The acute phase lasts for the first few weeks or months ofinfection. Mild symptoms can include fever, fatigue , headache,rash, loss of appetite, diarrhea, and vomiting
The signs on physical examination can include mild enlargementof the liver or spleen, swollen glands, and local swelling (achagoma) where the parasite entered the body
The symptomatic chronic stage affects the nervous
system, digestive system, and heart
About two thirds of people with chronic symptoms have cardiacdamage, including dilated cardiomyopathy, which causes heartrhythm abnormalities and may result in sudden death
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Cardiac muscle pathology; Chagas disease
Heart radiology Chagas diseaseHeart pathology Chagas disease
Romaa's sign, the swelling of thechild's eyelid, is a marker of acuteChagas disease. The swelling is dueto bug feces being accidentally
rubbed into the eye, or because thebite wound was on the same side ofthe child's face as the swelling.Photo courtesy of WHO/TDR.
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Toxoplasma gondii infection Toxoplasma gondiiis a species of parasitic protozoa in
the genus Toxoplasma
The definitive host of T. gondiiis the cat, but the parasitecan be carried by many warm-blooded animals (birdsor mammals, including humans)
Toxoplasmosis, the disease of which T. gondiiis thecausative agent, is usually minor and self-limiting but canhave serious or fatal effects on a fetus whose mother firstcontracts the disease during pregnancy or onan immunocompromised human
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ToxoplasmagondiiLife cycle
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Life cycle of T.gondii