This is especially true for heart transplant, which transmits T. cruzi 75–100% of the time, and less so for transplantation of the liver (0–29%) or a kidney (0–19%). An infected mother can pass T. cruzi to her child through the placenta; this occurs in up to 15% of births by infected mothers. As of 2019, 22.5% of new infections occurred through congenital transmission. Pathophysiology
In the acute phase of the disease, signs and symptoms are caused directly by the replication of T. cruzi and the immune systems response to it. During this phase, T. cruzi can be found in various tissues throughout the body and circulating in the blood. During the initial weeks of infection, parasite replication is brought under control by production of antibodies and activation of the hosts inflammatory response, particularly cells that target intracellular pathogens such as NK cells and macrophages, driven by inflammation-signaling molecules like TNF-α and IFN-γ.During chronic Chagas disease, long-term organ damage develops over years due to continued replication of the parasite and damage from the immune system. Early in the course of the disease, T. cruzi is found frequently in the striated muscle fibers of the heart. As disease progresses, the heart becomes generally enlarged, with substantial regions of cardiac muscle fiber replaced by scar tissue and fat. Areas of active inflammation are scattered throughout the heart, with each housing inflammatory immune cells, typically macrophages and T cells.
These side effects can sometimes be treated with antihistamines or corticosteroids, and are generally reversed when treatment is stopped. However, benzidazole is discontinued in up to 29% of cases. Nifurtimox has more frequent side effects, affecting up to 97.5% of individuals taking the drug. The most common side effects are loss of appetite, weight loss, nausea and vomiting, and various neurological disorders including mood changes, insomnia, paresthesia and peripheral neuropathy. Treatment is discontinued in up to 75% of cases. Both drugs are contraindicated for use in pregnant women and people with liver or kidney failure. As of 2019, resistance to these drugs has been reported. Complications
In the chronic stage, treatment involves managing the clinical manifestations of the disease. The treatment of Chagas cardiomyopathy is similar to that of other forms of heart disease. Beta blockers and ACE inhibitors may be prescribed, but some people with Chagas disease may not be able to take the standard dose of these drugs because they have low blood pressure or a low heart rate. To manage irregular heartbeats, people may be prescribed anti-arrhythmic drugs such as amiodarone, or have a pacemaker implanted. Blood thinners may be used to prevent thromboembolism and stroke. Chronic heart disease caused by Chagas is a common reason for heart transplantation surgery. Because transplant recipients take immunosuppressive drugs to prevent organ rejection, they are monitored using PCR to detect reactivation of the disease.