Frequently Asked Questions
Consult the Network's list of frequently asked questions, with brief answers prepared by the clinical committee.
Go to FAQChagas in Chile
Clinical care guide based on current protocols for the diagnosis, treatment and follow-up of Chagas disease.
Diagnosis
Summary
Who to test
A suspected case is defined by risk factors (Table No. 1, p. 12):
- Having lived in or visited endemic countries for more than one month.
- Having lived in the endemic area of Chile —from Arica y Parinacota to O’Higgins, including the Metropolitan Region— before 1999.
- Having a family member diagnosed with Chagas disease.
- Having seen or been in contact with the kissing bug (Triatoma infestans).
- Having received a blood transfusion before 1996 anywhere in the country, or before 2008 between Maule and Magallanes.
Confirmed case
- Positive serology confirmed by the ISP or a recognised laboratory (p. 11).
- Positive direct method (microstrout) (p. 11).
- Two detectable PCR results in newborns or immunocompromised people (p. 11).
Source: Procedures Manual for the Care of Patients with Chagas Disease (MINSAL, 2017) and General Technical Standard for National Control and Prevention (Res. Ex. No. 144, 2014)
Diagnostic algorithm in immunocompetent adults
The 2014 General Technical Standard sets out the diagnostic pathway for serum, plasma or CSF samples (Annex No. 1, p. 74):
- First serology negative: infection is ruled out.
- First serology reactive: the test is repeated in duplicate.
- Two negative results rule out infection.
- With two of three reactive results, the sample is sent to the ISP for confirmation (Standard, p. 36).
- Two positive results, or one positive and one negative, are sent to the ISP for confirmation (p. 74).
- An indeterminate or inconclusive result requires a new sample (p. 37).
Treatment
Summary
Drugs
- Benznidazole and nifurtimox are the drugs available in Chile (p. 17).
Who to treat
- Acute phase, by any transmission route.
- Immunocompromised people or candidates for immunosuppression.
- People under 18 years with positive serology.
- Newborns with congenital Chagas disease.
- Women of childbearing age up to 45 years, not pregnant or breastfeeding.
- Adults up to 60 years with positive serology in the indeterminate chronic phase.
- Laboratory or surgical accidents with sharps.
Regimens and doses
- Adults over 15 years: benznidazole 7.5 mg/kg/day (maximum 300 mg/day), every 12 or 8 hours for 60 days (Manual, p. 18).
- Alternative: nifurtimox 8-10 mg/kg/day (maximum 700 mg/day), every 12 or 8 hours for 60 days (Manual, p. 18).
- Start with ¼ or ½ of the dose and increase to the full dose over 3-10 days to detect adverse effects early (p. 18).
- Interruption of fewer than 7 days for a reason other than a serious reaction: restart from the day it was stopped (p. 18).
- From 7 discontinuous days it is considered abandonment (p. 18; Standard, p. 48).
Contraindications and precautions
- Absolute: pregnancy, breastfeeding, hypersensitivity to the drugs, haematological, renal, hepatic or pulmonary failure and G6PD deficiency (Manual, Annex No. 2, p. 54; Standard, pp. 44-45).
- Also absolute: terminal severe Chagas cardiomyopathy, inveterate alcoholism, severe mental illness and informed refusal of treatment.
- Relative: impossibility of systematic monitoring (seasonal workers, rural areas), pacemakers and suspected poor adherence (Standard, p. 45).
Source: Procedures Manual for the Care of Patients with Chagas Disease (MINSAL, 2017) and General Technical Standard for National Control and Prevention (Res. Ex. No. 144, 2014)
Cure criteria and treatment failure
- Acute phase: negative parasitaemia and negative IgG/IgM, without sequelae, at 6 months.
- Chronic phase: IgG negative for at least 3 months; seroreversion may take up to 10 years.
- Detection of parasites by PCR indicates treatment failure and requires annual follow-up with ECG, serology and targeted history (p. 19).
Follow-up
Summary
Monitoring during treatment
- Baseline tests: blood count with ESR and platelets, biochemistry panel, liver panel, ECG and pregnancy test when applicable (p. 20).
- Visits in adults on days 0, 15, 30, 45 and 60 (p. 20).
After treatment
- Visits at 6 and 12 months and annually for 3 years (p. 19).
- At each visit: PCR (if an initial PCR was done), IgG serology, blood count/liver panel and ECG if they were abnormal (p. 19).
Source: Procedures Manual for the Care of Patients with Chagas Disease (MINSAL, 2017) and General Technical Standard for National Control and Prevention (Res. Ex. No. 144, 2014)
Discharge and follow-up in primary care
Discharge takes place after the last specialist visit, with a discharge summary and referral to primary care. Each annual visit includes ECG, screening for digestive and cardiac abnormalities by history and physical examination, referral to a specialist if findings appear, and IgG serology (p. 21).
People with no indication for treatment
Annual visits with targeted history, education, physical examination and ECG; if clinically warranted, barium enema, manometry or oesophagogastroduodenal X-ray (Standard, p. 51).
Relaxing the follow-up schedule
With two negative IgG results at least 6 months apart and no sequelae, visits may be spaced out (Standard, p. 51).
Pregnancy and Congenital Chagas
Summary
Screening in pregnancy
- Risk of transplacental transmission of 5-7 %, repeatable in successive pregnancies (pp. 14 and 25).
- Every pregnant woman since 2014: IgG anti-T. cruzi ELISA at the first prenatal visit, together with HIV and syphilis (p. 25; Standard, p. 33).
- Screening is not mandatory in non-endemic areas, but a targeted history must still be taken (Standard, p. 33).
- A pregnant woman with IFI ≥ 1/20 and/or a positive result under the ISP algorithm is considered confirmed (p. 15).
Treatment
- Antiparasitic treatment is contraindicated during pregnancy and breastfeeding: it is deferred until after breastfeeding (p. 18).
Newborn
- Test infants born to mothers with confirmed Chagas disease with microstrout and/or PCR (Manual, pp. 25 and 37).
- Take samples at birth, at 2 months and at 9 months (Standard, Annex No. 2, p. 75).
- A positive microstrout confirms the diagnosis at any age.
- Two consecutive detectable PCR results confirm the case.
- A positive IgG is only valid after 9 months of age and with no previous treatment.
Validity note: the ISP published a 2026 update to the congenital algorithm, pending incorporation into this page.
Source: Procedures Manual for the Care of Patients with Chagas Disease (MINSAL, 2017) and General Technical Standard for National Control and Prevention (Res. Ex. No. 144, 2014)
Clinical features of congenital Chagas disease
90 % of newborns are asymptomatic. When manifestations occur, the picture resembles a TORCH syndrome: prematurity, small for gestational age, hepatosplenomegaly, anaemia, predominantly indirect jaundice, meningoencephalitis with clear CSF, septicaemia, myocarditis or exanthema (p. 25).
HIV co-infection
Pregnant women with Chagas disease and HIV must be referred to the tertiary level, with confirmation of receipt at the high-risk obstetric clinic (Standard, p. 34).
Pediatrics
Summary
Who to treat
- Every person under 18 years with T. cruzi infection must have access to treatment, regardless of the transmission route (p. 26).
Regimens and doses
Regimen for children under 15 years (Manual, p. 26):
- Benznidazole 5-7 mg/kg/day (newborns: 5 mg/kg/day), every 12 hours for 60 days.
- Nifurtimox 12-15 mg/kg/day in infants up to 1 year and 8-10 mg/kg/day in children over 1 year, every 12 hours for 60 days.
- If weight-based fractioning gives unequal doses during the day, the first dose must be the largest (p. 26).
Monitoring during treatment
- Baseline tests: biochemistry panel, blood count, urinalysis, creatinine, ECG and echocardiography.
- Visits every 7 days for the first 30 days, then every two weeks.
- In the event of an adverse reaction: stop, notify and retry after one month with the other drug (pp. 26-27).
Acute Chagas disease
- Requires immediate hospitalisation and antiparasitic treatment (p. 26).
Source: Procedures Manual for the Care of Patients with Chagas Disease (MINSAL, 2017) and General Technical Standard for National Control and Prevention (Res. Ex. No. 144, 2014)
Follow-up and cure criteria
- Visits at 6 and 12 months and annually for 5 years, with PCR, IgG, blood count/liver panel and ECG if they were abnormal.
- Cure: up to two years after treatment with undetectable PCR and negative IgG and no sequelae (p. 27).
- PCR becomes negative before serology, which may take 1-3 years (p. 27).
Adverse Reactions
Summary
Frequency and presentation
- Among adults, 25-30 % of treated people have adverse reactions, usually mild and not requiring discontinuation (p. 21).
- Among children only 6 % have early adverse effects, which usually resolve when the dose is reduced (p. 30).
- They appear from the 1st-2nd week of treatment, hence the scheduled monitoring (p. 21).
Mild or moderate reactions
- Persistent vomiting, weight loss greater than 5 %, digestive disorders, headache, irritability, insomnia and arthralgia (pp. 21-22).
Serious reactions
- Stevens-Johnson-type rash, pancytopenia, anaemia or thrombocytopenia, eosinophilia and leucopenia below 2,500/mm³ (p. 22).
- Transaminases ≥3 times normal, weight loss greater than 15 % and central nervous system disturbances (Manual, p. 22).
Pharmacovigilance
- The prescribing physician is responsible for notification (pp. 23-24).
- Notify serious reactions within 72 hours and mild or moderate ones within 30 days (pp. 23-24 and 31).
- Send the notification to cenimef@ispch.cl, through the official mailroom or the red-RAM system (p. 23).
- Follow up at 15 and 30 days after discontinuation (p. 23).
Source: Procedures Manual for the Care of Patients with Chagas Disease (MINSAL, 2017) and General Technical Standard for National Control and Prevention (Res. Ex. No. 144, 2014)
Management of mild or moderate reactions
Reduce the dose for 2-3 days and restart according to medical assessment, with symptomatic treatment (antihistamines, omeprazole, analgesia) and direct observation (p. 22). Anorexia and weight loss do not justify discontinuation unless there is severe nutritional compromise (Standard, p. 53).
Management of serious reactions
Definitive discontinuation of the drug, hospitalisation if needed and restart with the other drug once the patient is stabilised, with referral to a specialist (p. 23).
Surveillance
Summary
Notification
- Chagas disease is universally notifiable (p. 10).
- ICD-10 codes by stage: B57.0/B57.1 acute, P00.2 congenital, B57.2-B57.5 chronic and Z22.8 indeterminate chronic (p. 10 and Annex 1, p. 54; Standard, p. 39).
- D.S. 7/2019 (24-01-2020): repeals D.S. 158/2004 and requires immediate notification of acute Chagas disease and within 24 hours for chronic cases.
- Every Z22.8 case must be reassessed and, if organ damage is confirmed, re-notified with the corresponding code in the current statistical year (Standard, p. 39).
- Public and private laboratories must report every confirmed case to the health authority (p. 9).
Source: Procedures Manual for the Care of Patients with Chagas Disease (MINSAL, 2017) and General Technical Standard for National Control and Prevention (Res. Ex. No. 144, 2014)
Contact tracing and investigation
Contacts include direct maternal-line relatives (children, mother, siblings and grandmother), people living with a confirmed child, and residents of households positive for or colonised by Triatoma infestans (Standard, p. 39). The investigation is coordinated with the vector-control home visit, with a census, education, sample collection at home or by appointment, and delivery of the result with counselling (Standard, p. 40; Manual, p. 49).
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