Frequently Asked Questions
Consult the Network's list of frequently asked questions, with brief answers prepared by the clinical committee.
Go to FAQChagas in Ecuador
Clinical care guide based on current protocols for the diagnosis, treatment and follow-up of Chagas disease.
Diagnosis
Summary
Who to test
- Fever and residence or stay in an endemic area within the last 3 months (2017 Protocol, §11.6).
- Plus one of the following: inoculation chagoma, Romaña’s sign, lymphadenopathy, hepatosplenomegaly, irritability, drowsiness or anorexia (§11.6).
- Around 8 % of infected people have clinical manifestations; prolonged fever is the guiding symptom (§11.6).
- Two or more simultaneous acute cases: suspect oral transmission and manage as an emergency (§11.6).
Acute phase
- Confirm with positive direct parasitology or two serological tests of different principles; a third test if discordant (§11.6).
Chronic phase
- Confirm with IgG ELISA plus a second test of a different principle (ELISA, IHA or IFA); a third test if discordant (§11.8).
Source: Aetiological management of Chagas disease. Protocol (MSP, 2017, AM 0070-2017) and Manual for the surveillance and control of Chagas disease in Ecuador (MSP/INSPI, 2020)
Available diagnostic methods
Sensitivity of the INSPI methods (2017 Protocol, Table 2):
- Fresh blood drop: 85 % · thick smear: 60 %
- Strout: >95 % · microhaematocrit: >95 %
- Blood culture: 20-100 % · xenodiagnosis: 98-100 %
- PCR (EDTA blood): 56-96 %
- ELISA: 96 % · IHA: 99 % · IFA: 97-100 %
In the acute phase, if the first samples are negative and suspicion persists, direct tests must be repeated on three consecutive days (§11.9).
Interpretation by phase
- Acute phase: parasitaemia allows direct diagnosis; serology becomes positive from day 30 onwards (§11.8).
- Chronic phase: diagnosis is essentially serological, with one high-sensitivity test (ELISA or IFA) and one high-specificity test (§11.8-11.9).
- PCR: reserved for doubtful serology and as the confirmatory test in immunocompromised people and children under 9 months, with two consecutive positive results (§11.9).
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Treatment
Summary
Drugs
- Benznidazole and nifurtimox are the available drugs (Table 4; §11.10).
- Nifurtimox is not included in the National List of Essential Medicines: authorisation is required (Tables 4-9).
Who to treat
- Acute phase: treat at all ages (Table 4).
- Indeterminate chronic phase (15-50 years): benznidazole 5-7.5 or nifurtimox 8-10 mg/kg/day, 60 days (B II, Table 8).
- In people over 50 years the evidence is insufficient (E III, Table 8).
- Determinate chronic phase: treat for 60-90 days depending on tolerability (C II, Table 8).
Regimens and doses
- Benznidazole: 5-7.5 mg/kg/day under 12 years; 5-7 mg/kg/day from 12 years; 2 doses, 60 days (Table 4).
- Nifurtimox: 15-20 mg/kg/day up to 10 years; 12.5-15 mg/kg/day from 11 to 16; 8-10 mg/kg/day from 17 years; in 3-4 doses, 60-90 days (Table 4).
Source: Aetiological management of Chagas disease. Protocol (MSP, 2017, AM 0070-2017) and Manual for the surveillance and control of Chagas disease in Ecuador (MSP/INSPI, 2020)
Special situations
Newborn
- Benznidazole 5-10 mg/kg/day or nifurtimox 10-12 mg/kg/day, in 2-3 doses, 60 days (A II, Table 5).
- In low-birth-weight or premature infants, start with half the dose (Table 5).
- Complete the dose after 3 days if there is no leucopenia or thrombocytopenia (Table 5).
Immunocompromised people and HIV co-infection
- Benznidazole 5-7 or nifurtimox 8-10 mg/kg/day for 60-90 days (A II, Table 9).
- Reactivation may occur with haematological malignancies, immunosuppressants or HIV (Table 9).
Transplantation
- Positive donor: treat 60 days before transplantation (A II, Table 9).
- Negative recipient from a positive donor: treat for 10 days after surgery; in case of seroconversion, treat as an acute case (Table 9).
Laboratory accidents
- Usual doses for 10 days, or 30 days if a high parasite load is suspected; 60 days if transmission is confirmed (Table 7).
- Do not give prophylaxis if contact was with blood from a chronic-phase patient (Table 7).
Contraindications
- Absolute: pregnancy, hypersensitivity to the drug or other nitroimidazoles, alcohol intake and blood dyscrasias (§11.11).
- Relative: severe hepatic or renal disease unrelated to T. cruzi and breastfeeding (§11.11).
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Follow-up
Summary
Monitoring during treatment
- Physical examination focused on skin, neurological and gastrointestinal reactions: daily during the first week, then weekly (§11.13).
- Baseline laboratory tests (blood count, AST, ALT and creatinine): repeat mid-treatment and 15 days after completion (§11.13).
- At each visit: weight, tolerability, laboratory results and cardiovascular, hepatic, renal and metabolic assessment (§11.13).
Parasitological and serological follow-up
- Parasitological: at baseline and at the 1st and 3rd month after completion (direct method, Strout, smear).
- Serological (IFA, ELISA): at the 1st, 2nd and 3rd year in acute Chagas disease; annually up to 2 years in indeterminate chronic disease (§11.13-11.14).
Source: Aetiological management of Chagas disease. Protocol (MSP, 2017, AM 0070-2017) and Manual for the surveillance and control of Chagas disease in Ecuador (MSP/INSPI, 2020)
Cure criteria
- Parasitological cure: negative direct and indirect tests after treatment; essential in acute cases.
- Serological cure: progressive and persistent seronegativity, or a drop of at least 3 titres by IFA.
- Confirm serological cure with 12 months between tests and follow-up of 10 years or more (§11.14).
Expected time to seronegativity
- About 1 year in vertical transmission
- 3-5 years in people treated in the acute phase
- 5-10 years in recent chronic cases
- More than 20 years in old infections (§11.14)
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Pregnancy and Congenital Chagas
Summary
Pregnancy
- Do not treat during pregnancy because of the risk of teratogenic effects (§11.10.1.1).
- Treating women of childbearing age prevents congenital transmission in future pregnancies (E III, §11.10.1.1).
Newborn
- Cord blood or venous blood within 10 days for direct parasitology (§11.3).
- Parasitological diagnosis from birth to 4 months, repeated at 3 months (2017 Protocol, Table 6).
- If negative and suspicion persists, serology at 9-12 months; if negative at 24 months, infection is ruled out (§11.3).
- Before 9-12 months there is passive transfer of IgG: the parasite must be demonstrated (§11.3).
- After 12 months, reactive serology confirms infection (§11.3).
- Process direct samples within 12 hours of collection (§11.3).
Source: Aetiological management of Chagas disease. Protocol (MSP, 2017, AM 0070-2017) and Manual for the surveillance and control of Chagas disease in Ecuador (MSP/INSPI, 2020)
Prenatal screening (2020 Manual, §1.18.3)
Serology for T. cruzi must be part of routine prenatal tests in high-risk areas, and in any region of the country for pregnant women meeting any of these criteria:
- Living in a rural area of municipalities below 2,000 m above sea level.
- Housing conditions favourable to triatomine infestation.
- Family history of Chagas disease.
The threefold purpose is early treatment of the infant, prevention of congenital cases in subsequent pregnancies and detection of an early chronic case.
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Pediatrics
Summary
Regimens and doses
- Benznidazole: 5-7.5 mg/kg/day under 12 years; 5-7 mg/kg/day from 12 years; 2 doses, 60 days (Table 4).
- Nifurtimox: 15-20 mg/kg/day up to 10 years; 12.5-15 mg/kg/day from 11 to 16; 8-10 mg/kg/day from 17 years; in 3-4 doses, 60-90 days (Table 4).
Newborn
- Benznidazole 5-10 mg/kg/day or nifurtimox 10-12 mg/kg/day, in 2-3 doses, 60 days (A II, Table 5).
- In low-birth-weight or premature infants, start with half the dose (Table 5).
- Complete the dose after 3 days if the blood count is normal (Table 5).
Diagnosis and treatment
- All at-risk children who have not been diagnosed must receive conventional serology by their first birthday (2017 Protocol, §11.10).
- Every confirmed child is treated according to the national standards for the care of people with Chagas disease (§11.10).
Source: Aetiological management of Chagas disease. Protocol (MSP, 2017, AM 0070-2017) and Manual for the surveillance and control of Chagas disease in Ecuador (MSP/INSPI, 2020)
Active detection in childhood (2020 Manual, §1.18.2)
In endemic areas, active detection of seropositive children in the early years of the chronic phase is a priority, with serology campaigns in children under 15 years in cantons with recent vector-borne transmission risk (2020 Manual, §1.18.2).
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Adverse Reactions
Summary
Benznidazole
- Mild dermatopathy 29-50 % in the 2nd week: continue with antihistamines (Table 10).
- Moderate dermatopathy (<5 %): temporary interruption and reintroduction according to tolerability, with antihistamines or corticosteroids.
- Marked dermatopathy (<1 %): interrupt and hospitalise.
- Peripheral neuropathy 0-30 % after the 6th week: interrupt until improvement and refer to Neurology.
- Bone marrow hypoplasia (<1 % in the 3rd week): interruption without reintroduction and transfer to tertiary/quaternary care.
- Ageusia <0.5 %; gastrointestinal disturbances 0-5 % in the 1st week: continue with symptomatic treatment.
Nifurtimox
- CNS neurotoxicity 50-75 % in the 3rd week: interrupt if weight loss exceeds 20 % (Table 11).
- Gastrointestinal disturbances 15-50 % in the 1st week; peripheral neuropathy 2-5 % after the 6th week; leucopenia <1 %.
Source: Aetiological management of Chagas disease. Protocol (MSP, 2017, AM 0070-2017) and Manual for the surveillance and control of Chagas disease in Ecuador (MSP/INSPI, 2020)
Management and notification
Adverse reactions are managed by continuing treatment with symptomatic measures or interrupting it temporarily or definitively, according to Tables 10 and 11. Every suspected reaction is notified on the Annex VI form, under Resolution ARCSA-DE-020-2016-YMIH (Official Gazette 856, 6 October 2016), which is binding on all healthcare professionals; the report is sent to farmaco.vigilancia@controlsanitario.gob.ec (2017 Protocol, §11.12 and Annex VI).
- Gastrointestinal disturbances: aluminium hydroxide, metoclopramide and hyoscine butylbromide.
- Peripheral neuropathy: oral analgesics.
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Surveillance
Summary
Notification
- Every case of T. cruzi infection, regardless of the transmission route, is notifiable (2017 Protocol, §11.7).
- SIVE 2025 Standard: acute (B57.0 <> B57.1) and chronic (B57.2 <> B57.5): universal surveillance, immediate notification within 24 hours.
- Individual EPI 1 notification, by laboratory and with an investigation form.
Source: Aetiological management of Chagas disease. Protocol (MSP, 2017, AM 0070-2017) and Manual for the surveillance and control of Chagas disease in Ecuador (MSP/INSPI, 2020)
Early detection (2020 Manual, §1.15-1.19)
- Suspect acute Chagas disease with prolonged fever in emergency or outpatient care, and test for T. cruzi in the thick smear (2020 Manual, §1.15-1.19).
- Detect in children under 15 years, look for incipient heart disease and screen at-risk pregnant women.
- Screen 100 % of blood donors with reagents of at least 99.8 % sensitivity and 99.5 % specificity.
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