Frequently Asked Questions
Consult the Network's list of frequently asked questions, with brief answers prepared by the clinical committee.
Go to FAQChagas in Paraguay
Clinical care guide based on current protocols for the diagnosis, treatment and follow-up of Chagas disease.
Diagnosis
Summary
Who to test
- Active screening in pregnant women and women of childbearing age, transfused or transplanted people, household contacts of patients and symptomatic people (2021 Guide, p. 3).
Confirmation of chronic infection
- Two concordant serological tests of different principles (2021 Guide, pp. 4-5).
- One rapid test plus one serological test also confirms (2021 Guide, pp. 4-5).
- Discordant or doubtful result: a third test with a different target antigen and principle (2021 Guide, pp. 4-5).
By phase
- Acute phase: microscopy, microhaematocrit and PCR (2021 Guide, Tables 1 and 2).
- Chronic phase: conventional or recombinant ELISA, chemiluminescence, IHA, IFA and rapid tests (2021 Guide, Tables 1 and 2).
By resource level
- Rural or low-resource areas: rapid test then IHA/ELISA/IFA (2021 Guide, Table 2).
- Urban areas: ELISA and chemiluminescence as first and second tests, with IHA or IFA (2021 Guide, Table 2).
Notification
- Every confirmed case is notified to the Regional Epidemiological Unit (2021 Guide, p. 5).
Source: Management guide for adult patients with Chagas disease (MSPBS/SENEPA, 2021) and Practical guide for the management of congenital Chagas transmission and recent chronic Chagas disease in children (MSPBS/SENEPA, 2023)
Diagnostic algorithm in adults
Rapid test → sample collection for confirmation and referral to the reference hospital → serology: negative rules out, positive confirms → case notification, screening of household members and vector control → assessment of visceral involvement → start treatment if criteria are met (2021 Guide, flowchart, p. 6).
Rapid test: correct use
Capillary blood discarding the first drop; 6 drops (about 240 µl) of diluent; reading required within 15 minutes. A single CONTROL line = negative, two lines = positive and no CONTROL line = invalid, repeat (2021 Guide, Annex 1, pp. 23-24).
Treatment
Summary
Who to treat
- Everyone with positive T. cruzi serology and no contraindication is treated, after verifying the absence of the vector in the home (2021 Guide, p. 12).
- Always indicated: congenital infection (under 1 year), acute phase at any age and chronic phase in children under 14 years (2021 Guide, Table 6).
- Always indicated: reactivation, women of childbearing age and laboratory or surgical accidents (2021 Guide, Table 6).
- Between 14 and 60 years, in the indeterminate phase or mild/moderate stage and in immunocompromised patients (2021 Guide, Table 6).
- Over 60 years without advanced organ involvement: optional (2021 Guide, Table 6).
Contraindications and precautions
- Contraindicated: pregnancy and advanced renal or hepatic failure (2021 Guide, Table 6).
- Not recommended: advanced cardiac or digestive disease and breastfeeding (2021 Guide, Table 6).
- Women of childbearing age: rule out pregnancy before starting and use contraception during treatment (2021 Guide, pp. 12 and 21).
Regimens and doses (adults)
- Benznidazole (first choice of the National Chagas Programme): 5 mg/kg/day in two doses, 60 days, maximum 300 mg/day (2021 Guide, Table 7, p. 14).
- Above 80 kg the duration is extended until the calculated total dose is completed (2021 Guide, Table 7).
- Nifurtimox (alternative): 8-10 mg/kg/day in three doses, 60 days, maximum 600 mg/day (2021 Guide, Table 8, p. 15).
Source: Management guide for adult patients with Chagas disease (MSPBS/SENEPA, 2021) and Practical guide for the management of congenital Chagas transmission and recent chronic Chagas disease in children (MSPBS/SENEPA, 2023)
How it is administered (adults)
- The tablet may be split in halves or quarters, always with meals.
- Do not make up a missed dose together with the next one.
- Treatment may be started gradually over the first 4 days to improve tolerability.
- Avoid prolonged sun exposure and follow a diet without fatty foods, alcohol, soft drinks, preservatives or condiments (2021 Guide, p. 16).
Expected effectiveness
Close to 100 % in children under 1 year, around 80 % in children under 15 years and in adults in the chronic phase (2021 Guide, p. 13).
Follow-up
Summary
Annual follow-up
- All patients: annual clinical and electrocardiographic assessment (2021 Guide, p. 17).
- Follow-up is delivered by the Family Health Units and Family Health Teams (2021 Guide, p. 17).
- If none is nearby, by the health institution most accessible to the patient (2021 Guide, p. 17).
Source: Management guide for adult patients with Chagas disease (MSPBS/SENEPA, 2021) and Practical guide for the management of congenital Chagas transmission and recent chronic Chagas disease in children (MSPBS/SENEPA, 2023)
Post-treatment serological follow-up
- Treated patients: serological follow-up every two years (2021 Guide, p. 17).
- The notification form records post-treatment serology at 12 and 24 months (notification form, March 2022).
Pregnancy and Congenital Chagas
Summary
Screening in pregnancy
- Every pregnant woman is screened at the prenatal visit, at delivery or postpartum (2023 Guide, pp. 5-6).
- Along with ETMI-PLUS tests: serology in centres with a laboratory and a rapid test where none is available (2023 Guide, pp. 5-6).
Confirmation
- Positive screening: confirm with a test using a different antigen (2023 Guide, p. 6).
- If discordant: a third tie-breaker test (IFA) at the reference laboratory (2023 Guide, p. 6).
Treatment
- Chagas disease is not treated during pregnancy because of the teratogenic risk (2023 Guide, pp. 7-8).
- The woman is treated after delivery and after finishing breastfeeding, which is not contraindicated (2023 Guide, pp. 7-8).
Source: Management guide for adult patients with Chagas disease (MSPBS/SENEPA, 2021) and Practical guide for the management of congenital Chagas transmission and recent chronic Chagas disease in children (MSPBS/SENEPA, 2023)
Care of the pregnant woman
- Explain the diagnosis, the risk of vertical transmission and the need to test her other children (2023 Guide, pp. 7-8).
- Consult Internal Medicine or Infectious Diseases (2023 Guide, pp. 7-8).
- ECG during pregnancy and echocardiography after birth (2023 Guide, pp. 7-8).
- Chagas disease does not change obstetric management; with a symptomatic form, follow-up moves to a high-risk obstetric centre (2023 Guide, pp. 7-8).
Assessment of the newborn
- First weeks: direct parasitology (microhaematocrit or microstrout) or PCR before one month of age, with reading within 8 hours (2023 Guide, pp. 9-10).
- If negative: repeat at 1-2 months; if still negative, serology with two different techniques between 1 and 12 months (2023 Guide, pp. 9-10).
- Both positive confirms and treatment starts; both negative means definitive discharge; if discordant, repeat serology at 12 months (2023 Guide, pp. 9-10).
- PCR is not currently available in the public system (2023 Guide, p. 10).
Pediatrics
Summary
Who to treat
- Children under 14 years (or 40 kg) (2023 Guide, p. 3).
- From 14 years or 40 kg, the adult guide applies (2023 Guide, p. 12).
Regimens and doses
- Benznidazole: under 1 year 10 mg/kg/day (2023 Guide, p. 12).
- Benznidazole: over 1 year and under 40 kg 7.5 mg/kg/day, in two to three daily doses, 60 days (2023 Guide, p. 12).
- Nifurtimox: under 1 year 10-15 mg/kg/day (2023 Guide, p. 12).
- Nifurtimox: over 1 year and under 40 kg 10 mg/kg/day (2023 Guide, p. 12).
Place of treatment
- Preferably at the first level of care, supervised by the Family Health Team (2023 Guide, p. 13).
Cure criterion
- Serological negativisation, with checks at 6 and 12 months after completing treatment (2023 Guide, p. 15).
Source: Management guide for adult patients with Chagas disease (MSPBS/SENEPA, 2021) and Practical guide for the management of congenital Chagas transmission and recent chronic Chagas disease in children (MSPBS/SENEPA, 2023)
Monitoring during treatment
- Weekly or fortnightly visits with targeted history for digestive, skin, neuromuscular and haematological symptoms, anthropometric follow-up and full physical examination (2023 Guide, p. 13).
- Request blood count, liver panel, blood chemistry and urinalysis if adverse reactions occur (2023 Guide, p. 13).
- Keep a written record of administration (2023 Guide, p. 13).
Premature and low-birth-weight infants
- Start with half the dose once daily and increase every 48-72 hours with blood count monitoring (2023 Guide, pp. 12 and 14).
- If the blood count is normal at 7 days, switch to the full dose, to complete 60 days (2023 Guide, pp. 12 and 14).
If serology remains positive after treatment
Check drug administration (dose or adherence) and possible parasite resistance, and consider repeating the cycle or switching the active substance (2023 Guide, p. 15).
Adverse Reactions
Summary
Most frequent adverse reactions
- Skin and digestive reactions, with headache, asthenia and fever (2021 Guide, Table 9).
- Haematological, neurological and joint reactions are less common; Stevens-Johnson syndrome or toxic epidermal necrolysis in fewer than 5 % (2021 Guide, Table 9).
Grading (CTCAE v5)
- Graded with the CTCAE v5 scale: fever 38-39 °C (mild), >39-40 °C (moderate) and >40 °C (severe) (2021 Guide, Table 9).
- Weight loss 5-10 % / 10-20 % / ≥20 % (2021 Guide, Table 9).
- Urticaria or erythema over <10 % / 10-30 % / >30 % of body surface area (2021 Guide, Table 9).
General rules
- Any haematological effect is managed as moderate or severe, although it does not always require stopping the drug (2021 Guide, p. 20).
- In children, reactions are uncommon: the younger the child, the lower the likelihood (2023 Guide, p. 14).
Source: Management guide for adult patients with Chagas disease (MSPBS/SENEPA, 2021) and Practical guide for the management of congenital Chagas transmission and recent chronic Chagas disease in children (MSPBS/SENEPA, 2023)
Management by grade
- Mild: continue treatment at the established doses (2021 Guide, p. 21).
- Mild: check the dose against current weight, with maxima of 300 mg/day BZD and 600 mg/day NFX (2021 Guide, p. 21).
- Mild: rule out other conditions, give symptomatic treatment and review clinically every 48 hours (2021 Guide, p. 21).
- Mild: if it does not improve or worsens within 3 days, reclassify as moderate (2021 Guide, p. 21).
- Moderate: stop for 3 to 5 days or until symptoms subside, with daily clinical review (2021 Guide, p. 22).
- Moderate: if it improves, continue with the minimum therapeutic dose to complete the regimen (2021 Guide, p. 22).
- Moderate: if BZD was stopped permanently, consider NFX after two months (2021 Guide, p. 22).
- Moderate: if it does not improve, refer to a tertiary hospital (2021 Guide, p. 22).
- Severe: stop immediately, give symptomatic treatment and refer immediately to a tertiary hospital (2021 Guide, p. 22).
In children
- Mild effect: reduce the dose and add an antihistamine (2023 Guide, p. 14).
- Petechiae, leucopenia, thrombocytopenia or skin vesicles: stop immediately and take the child to a health facility (2023 Guide, p. 14).
Surveillance
Summary
Notifiable disease
- A transmissible event with universal and individual surveillance: suspicion is captured through the clinical strategy and confirmation through the laboratory strategy (2021 Guide, p. 29).
- Weekly notification, except for transfusion- or food-borne acute Chagas disease (2021 Guide, p. 29).
- Legal basis: Resolution S.G. No. 190/2013 (list of notifiable events) and Decree No. 21376/98 (DGVS mandate) (2021 Guide, p. 29).
- Resolution S.G. No. 1066 of 2006 (creation of the UERs in the 18 Health Regions).
Special surveillance
- Special studies in pregnant women, blood banks, young children and newborns (2021 Guide, p. 29).
- Pregnant women, newborns and other children of a positive mother are notified to the UER (2021 Guide, p. 29; 2023 Guide, p. 10).
Source: Management guide for adult patients with Chagas disease (MSPBS/SENEPA, 2021) and Practical guide for the management of congenital Chagas transmission and recent chronic Chagas disease in children (MSPBS/SENEPA, 2023)
Notification pathway
- Notifying unit (local): detects the event on suspicion, notifies, and assesses, follows up and controls the case (2021 Guide, p. 29).
- Regional Epidemiological Unit: receives the notification and forwards it to the DGVS, assesses event trends and investigates (2021 Guide, p. 29).
- DGVS (national): receives the notification, forwards it to SENEPA, analyses and investigates, and consolidates and disseminates the information (2021 Guide, p. 29).
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