Frequently Asked Questions
Consult the Network's list of frequently asked questions, with brief answers prepared by the clinical committee.
Go to FAQChagas in Costa Rica
Clinical care guide based on current protocols for the diagnosis, treatment and follow-up of Chagas disease.
Diagnosis
Summary
Who to test
- Fever of more than 7 days and headache, with chagoma, Romaña sign, hepatomegaly or acute heart disease (p. 23).
- Fever of more than 7 days and headache, with contact with the vector, transfusion, contaminated food or a laboratory accident (p. 23).
- Cardiomegaly, arrhythmias or right bundle branch block, and/or megaesophagus or megacolon, with vector contact or childhood in an endemic area (pp. 23-24).
Acute phase
- Confirmation: parasitaemia and/or two positive serological tests using antigens from different sources (p. 24).
- Detection: parasite at 5 to 7 days and Strout with close to 100 % sensitivity (p. 26).
- Duration: 4 to 12 weeks; up to 60 days, or 120 days if transfusion-borne (p. 20).
- More than 90 % of cases are asymptomatic (p. 20).
Chronic phase
- Confirmation: two positive IgG serological tests using antigens from different sources (p. 24).
- Sensitivity of parasitological tests: around 30 %; diagnosis is serological (p. 27).
- Outcome: 20 to 30 % develop sequelae (heart failure, arrhythmias or thromboembolism, and digestive megaformations) (p. 21).
Source: Norma de atención integral de la Enfermedad de Chagas, ICD-10: B57 (Ministry of Health of Costa Rica, 2010; Executive Decree No. 37269-S, La Gaceta No. 178 of 14-09-2012)
Sample collection and shipment
- Take 5 ml of whole blood without anticoagulant (1 ml in children under one year) by venepuncture (p. 27).
- Take at least one week after the bite; three weeks if indeterminate or chronic phase is suspected (p. 29).
- Process the clot at 45 minutes and separate the serum within 6 hours (p. 27).
- Keep the serum at 4 °C and send it to the CNRP-INCIENSA (p. 29).
Congenital Chagas disease
- Take 1 ml of blood without anticoagulant from the newborn of an infected mother for Microstrout (p. 27).
- Send the serum to the CNRP-INCIENSA and follow the flowchart in Annex 5 (p. 66).
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Treatment
Summary
Who to treat
- Acute phase of any origin, including exacerbations in immunocompromised patients (p. 30).
- Chronic indeterminate form in children and adolescents up to 14 years; PAHO/WHO extends the indication to under 18 years (p. 30).
- Indeterminate phase with confirmed recent infection, organ transplantation or a laboratory or surgical accident (p. 30).
- Do not treat if there is advanced heart disease or digestive disease (p. 30).
Regimens and doses
- Nifurtimox (120 mg tablets) and benznidazole (100 mg tablets); both schedules last 60 days (pp. 30-32).
- Nifurtimox: newborns (≤28 days) 12-15 mg/kg/day every 12 hours; infants and children 12-15 mg/kg/day in 3 doses (pp. 30-31).
- Nifurtimox: adolescents and adults 8-10 mg/kg/day in 3 doses; maximum 700 mg in 24 hours (pp. 30-31).
- Benznidazole: 5-10 mg/kg/day in children and 5-7 mg/kg/day in adults, in 2 daily doses (p. 31).
- Institutional use (CCSS) only; no adjustment above 60 kg (pp. 30-32).
Source: Norma de atención integral de la Enfermedad de Chagas, ICD-10: B57 (Ministry of Health of Costa Rica, 2010; Executive Decree No. 37269-S, La Gaceta No. 178 of 14-09-2012)
Before starting treatment
- A confirmed acute case is a medical emergency: coordinate treatment within 24 hours (pp. 29-30).
- Assess renal, haematological and hepatic function before starting (p. 30).
- In the chronic phase, refer to infectious diseases or internal medicine to assess treatment (p. 30).
National algorithm (Annex 10)
- For a suspected case: report to the surveillance system and take a blood sample (p. 72).
- If not confirmed: new sample at 6 months; if negative, discharge (p. 72).
- If confirmed: medical assessment and entomological survey with case classification (p. 72).
- Acute cases are managed at the local level and indeterminate cases at the second or third level (p. 72).
- Treatment candidate: benznidazole 5-7 mg/kg/day for 60 days; if not indicated, cardiology and annual follow-up (p. 72).
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Follow-up
Summary
Monitoring during treatment
- Weekly clinical assessment at the first level of care during treatment (pp. 32 and 34).
- In the indeterminate phase, annual electrocardiogram at minimum (p. 21).
Acute phase
- Parasitological monitoring (Strout or microstrout) at the end of treatment and at 6 months, 1, 3 and 5 years (p. 33).
Chronic phase
- Cure: antibody negativisation (p. 28).
- Paired monitoring (serum before and after treatment) every 6 months in the first year and then every 2 years (p. 28).
- In chronic and indeterminate cases, until 2 successive negative tests or 10 years of follow-up at the first level of care (p. 34).
- In chronic heart disease, refer to a cardiologist and maintain annual follow-up (Annex 10, p. 72).
Source: Norma de atención integral de la Enfermedad de Chagas, ICD-10: B57 (Ministry of Health of Costa Rica, 2010; Executive Decree No. 37269-S, La Gaceta No. 178 of 14-09-2012)
Immunosuppressed and transplanted patients
- If there is reactivation or infection of the donated organ with evidence of rejection: continue the antiparasitic and do not suspend the immunosuppressant (p. 34).
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Pregnancy and Congenital Chagas
Summary
Screening in pregnancy
- Request serology at the first prenatal visit if there is infection or epidemiological evidence of risk (p. 34).
- If she reaches delivery without the test, perform it during hospitalisation (p. 34).
- If reactive, assess by a specialist and verify the result before discharge (p. 35).
- Do not treat with the available drugs during pregnancy (p. 35).
- The standard does not cover postpartum treatment or breastfeeding: these are inherited from PAHO 2026 (p. 35).
- Congenital transmission occurs in up to 25 % of children of infected mothers (p. 19).
- The incidence of congenital cases varies between 2 and 12 % by country (p. 19).
Source: Norma de atención integral de la Enfermedad de Chagas, ICD-10: B57 (Ministry of Health of Costa Rica, 2010; Executive Decree No. 37269-S, La Gaceta No. 178 of 14-09-2012)
Newborn of a reactive mother
- Study all children of a serologically reactive mother; most are asymptomatic (p. 35).
- Perform perinatal Microstrout with 1 ml of blood, preferably before discharge (pp. 27 and 35).
- Positive parasitological test: start specific treatment (p. 35).
- Negative parasitological test and positive serology: repeat at 3 and 7 months; if both negative, discharge (p. 35).
- Flowchart (Annex 5): Strout in the newborn, Strout at 3 months and serology at 7 (p. 66).
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Pediatrics
Summary
Who to treat
- Treatment is indicated for the chronic indeterminate form in children and adolescents up to 14 years (p. 30).
- The standard stops the indication at 14 years; PAHO/WHO extends it to under 18 years (p. 30).
Regimens and doses
- Nifurtimox: newborns (≤28 days) 12-15 mg/kg/day every 12 hours; infants and children 12-15 mg/kg/day in 3 doses (pp. 30-31).
- Benznidazole: children 5-10 mg/kg/day in 2 doses; both schedules last 60 days (p. 31).
- Adverse reactions depend on dose and age, with better tolerance in children (p. 33).
Source: Norma de atención integral de la Enfermedad de Chagas, ICD-10: B57 (Ministry of Health of Costa Rica, 2010; Executive Decree No. 37269-S, La Gaceta No. 178 of 14-09-2012)
Gaps in the national paediatric schedule
- The standard does not define a benznidazole dose for newborns or paediatric weight bands (pp. 30-31).
- It also does not set a growth and development calendar: this block is inherited from PAHO 2026.
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Adverse Reactions
Summary
Nifurtimox
- Gastrointestinal intolerance: anorexia, nausea, vomiting and abdominal pain (p. 31).
- Neurological picture: headache, agitation, vertigo, myalgia, insomnia, neuritis and psychosis (p. 31).
- It may suppress cell-mediated immune reactions (p. 31).
Benznidazole
- Benign skin reactions (rash or urticaria) that do not require interruption; purpuric with fever, temporary interruption (p. 32).
- Nausea and gastrointestinal disturbances that resolve spontaneously, without reducing the dose (p. 32).
- Paraesthesia or peripheral polyneuropathy, uncommon, require discontinuation (p. 32).
- Leucopenia and thrombocytopenia normalise on interruption; headache, vertigo and fatigue are very rare (p. 32).
Interruption and restart
- Interrupt if severe allergic reactions, fever with lymphadenopathy, marked neuropathy or bone marrow depression appear (p. 32).
- If interrupted due to intolerance, the other drug may be tried under strict control (p. 33).
- Interruption of more than 15 days: restart at lower doses, increased gradually (p. 33).
- Without negativisation on one drug, switching is not justified except in exceptional cases (p. 34).
Pharmacovigilance
- The standard does not set incidence percentages or an antihistamine or corticosteroid schedule (pp. 31-33).
- It also has no pharmacovigilance section: this block is inherited from PAHO 2026 (pp. 31-33).
Source: Norma de atención integral de la Enfermedad de Chagas, ICD-10: B57 (Ministry of Health of Costa Rica, 2010; Executive Decree No. 37269-S, La Gaceta No. 178 of 14-09-2012)
Management of intolerance
- Instruct the patient or their parents to attend the health service if reactions appear (p. 33).
- Refer to infectious diseases or internal medicine if treatment is interrupted due to reactions or poor tolerance (p. 33).
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Surveillance
Summary
Notification
- Mandatory notification of every suspected case (ICD-10: B57) within the first 48 hours, using the Annex 1 form (p. 24).
- Investigate within the following 48 hours: clinical record, interview, blood samples from household contacts, entomological inspection and a 500-metre sweep (pp. 25-26).
Vector surveillance
- Only species of epidemiological importance: Triatoma dimidiata, present in all provinces up to 1,700 m (pp. 18 and 22).
- Main domestic reservoir: the dog; peridomestic: the opossum (Didelphis marsupialis) (p. 18).
- A person who finds an insect takes it to the EBAIS, which sends it to INCIENSA with the form (Annex 8) (p. 36).
Screening of donated blood
- Screen 100 % of donations with recombinant ELISA (at least 4 antigens) (p. 28).
- Send 100 % of positive and 5 % of negative samples to the CNRP-INCIENSA (p. 28).
Source: Norma de atención integral de la Enfermedad de Chagas, ICD-10: B57 (Ministry of Health of Costa Rica, 2010; Executive Decree No. 37269-S, La Gaceta No. 178 of 14-09-2012)
Risk factors and household control
- Risk: firewood less than 25 metres away, chicken coop less than 10 metres away, dirt or wooden floors (p. 38).
- Homes on stilts are also at risk; colonised homes have nymphs (pp. 38-39).
- Colonised homes: indoor and peridomestic spraying (Annex 9) and an entomological survey at 3, 6 and 12 months (pp. 41 and 49).
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