Frequently Asked Questions
Consult the Network's list of frequently asked questions, with brief answers prepared by the clinical committee.
Go to FAQChagas in Mexico
Clinical care guide based on current protocols for the diagnosis, treatment and follow-up of Chagas disease.
Diagnosis
Summary
Who to test
- Suspect in prolonged fever with oedema, exanthema, lymphadenopathy, hepatosplenomegaly or acute heart disease (2019, p. 37).
- Add Romaña sign, inoculation chagoma, haemorrhagic manifestations or jaundice (2019, p. 37).
- Epidemiological history: residence in or visit to an area with triatomines, suspected food or an infected mother (2019, p. 37).
- Transfusion or transplant in the previous 30 to 112 days (2019, p. 37).
- Confirmation is always laboratory based; the clinical-epidemiological criterion requires a link to a confirmed acute case (2019, p. 39).
Acute phase
- Confirm by demonstration of the parasite in peripheral blood (2019, pp. 46-47; 2015, p. 19).
- Fresh drop 80 to 90 %; thick film and stained smear, below 70 % (2019, pp. 46-47; 2015, p. 19).
- Concentration methods (microhaematocrit, microstrout and Strout) yield 90 to 100 % (2019, pp. 46-47; 2015, p. 19).
- Microhaematocrit is the first method of choice in vertical transmission (2019, pp. 46-47; 2015, p. 19).
- Qualitative PCR confirms in immunocompromised patients and children under 9 months, but is not the only method in surveillance (2019, pp. 41-42 and 48).
- Process the sample within 24 hours because of the risk of parasite lysis (2019, p. 47).
Chronic phase
- Confirm with two concordant positive serological tests of different principle or antigenic preparation (2019, p. 39; 2015, p. 15).
- A single reactive test does not diagnose (2019, p. 49; 2015, p. 22).
- With two tests certainty is 98 to 99.5 %; if discordant, a third test (IFA) and a new sample (2019, pp. 48-49; 2015, p. 22).
Source: Ministry of Health of Mexico, CENAPRECE — Manual of Procedures for Chagas Disease in Mexico (2019) and Manual for the Diagnosis and Treatment of Chagas Disease (2015); in Spanish
Serological interpretation and national network
- Antibodies are detected from the fourth week and IgG peaks at twelve weeks (2019, p. 48).
- A highly sensitive technique (total-antigen ELISA) and a highly specific one (recombinant ELISA) establish nearly 100 % of diagnoses (2019, p. 48).
- The national network (InDRE and local and state laboratories) applies basic parasitological tests and three serological tests (2019, pp. 43-44; 2015, p. 16).
Donor and transplant screening
- Screen all blood donors under NOM-253-SSA1-2012; since 2016, 100 % of blood banks are covered (2019, pp. 52 and 54; 2015, p. 25).
- With a reactive test: discard the blood, repeat in duplicate, take a second sample and perform supplementary tests (2019, p. 54; 2015, p. 25).
- With two reactive tests of different principle, the blood bank notifies epidemiology and reports the result to the donor (2019, p. 54; 2015, p. 25).
- Study every donor and potential transplant recipient by serology (2019, p. 55; 2015, p. 25).
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Treatment
Summary
Who to treat
- Treat 100 % of acute cases, regardless of the transmission mechanism (2019, p. 70).
- Treat every person with positive serology and no contraindications (2019, p. 70).
- Both drugs require caution and monitoring in hepatic, renal, haematological and neurological conditions (2019, p. 70).
Regimens and doses
- Benznidazole in adults: 5 to 10 mg/kg/day in 2 daily doses after meals, for 30 or 60 days, maximum 300 mg/day (2019, p. 68).
- If the daily dose exceeds 300 mg, extend treatment until the total dose calculated for 60 days is covered (2019, p. 68).
- Benznidazole in children and adolescents: 10 mg/kg/day orally in 2 or 3 doses for 60 days, maximum 300 mg/day (2019, p. 69).
- Nifurtimox: 10 mg/kg/day below 40 kg and 8 mg/kg/day above, for 60 days, maximum 700 mg/day (2019, p. 69).
- Give nifurtimox in 3 daily doses after meals (2019, p. 69).
Before starting treatment
- Medical examination and history beforehand, and information for the patient and family about benefits and risks (2019, p. 72; 2015, p. 33).
- Informed consent and a written commitment to adherence (2019, p. 72; 2015, p. 33).
- Pregnancy test in women of childbearing age and contraception during treatment (2019, p. 73; 2015, p. 33).
Contraindications and precautions
- Pregnancy and women of childbearing age without a contraceptive method (2019, p. 71).
- Renal or hepatic failure (2019, p. 71).
- Severe uncontrolled comorbidities: rheumatic diseases, skin diseases, neuropathies, neoplasms or gastroduodenal ulcer (2019, p. 71).
- Previous heart disease, refractory hypertension and neurological or psychiatric disease, especially with nifurtimox (2019, p. 71).
- Severe digestive signs: abdominal obstruction, faecaloma or constipation of more than 7 days (2019, p. 71).
- Indication for a permanent pacemaker after 24-hour Holter monitoring or severe colonic or oesophageal disease (2019, p. 71).
- Patients over 70 years with conditions that do not allow treatment to be started (2019, p. 71).
- Previous completed treatment, impossibility of follow-up and chronic Chagas cardiomyopathy: assess individually (2019, p. 71; 2015, p. 32).
Source: Ministry of Health of Mexico, CENAPRECE — Manual of Procedures for Chagas Disease in Mexico (2019) and Manual for the Diagnosis and Treatment of Chagas Disease (2015); in Spanish
Counselling and dispensing of medication
- Explain that the patient must not donate blood, tissues or organs (2019, p. 73).
- Dispense medication at intervals of 7, 15, 30 and 60 days, with a follow-up appointment (2019, p. 74; 2015, p. 33).
- If access is difficult, schedule the patient every 15 days (2019, p. 74; 2015, p. 33).
- Encourage the active search for triatomines and their reporting to vector control (2019, p. 72; 2015, p. 33).
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Follow-up
Summary
Monitoring during treatment
- Full course: 60 days; from 55 days onwards it is assumed complete (2019, pp. 70 and 75; 2015, p. 34).
- Interruption under 14 days: extend until 60 are completed; over 14 days: restart (2019, pp. 70 and 75; 2015, p. 34).
- Laboratory tests (urine, blood count and liver function) at the start, at 30 days and at the end (2019, p. 74).
- Pregnancy test in women of reproductive age at the first two assessments (2019, p. 74).
- Clinical supervision at least weekly throughout treatment, monitoring intolerance, digestive disorders and fever (2019, pp. 81-82; 2015, p. 37).
- Look for exanthema, insomnia, tremor, loss of balance, seizures, paraesthesia or persistent crying in infants (2019, pp. 81-82; 2015, p. 37).
Cure
- Cure: a conventional positive serological test that becomes negative (2019, p. 76; 2015, p. 35).
- First serological follow-up one year after treatment ends and then annually until negativisation (2019, p. 70).
- A persistent fall in titres of more than three dilutions is suggestive of negativisation (2019, p. 76).
Annual follow-up of chronic patients
- Annual visit with serology; electrocardiogram, echocardiogram, chest X-ray and oesophagogastric series or endoscopy according to suspicion (2019, p. 82; 2015, pp. 46-47).
- If compatible manifestations appear, refer to cardiology, gastroenterology or neurology (2019, p. 82; 2015, pp. 46-47).
Source: Ministry of Health of Mexico, CENAPRECE — Manual of Procedures for Chagas Disease in Mexico (2019) and Manual for the Diagnosis and Treatment of Chagas Disease (2015); in Spanish
Time to cure
- Child treated at one year of age: cure is verified about one year later (2015, p. 35).
- Child treated at 10 to 12 years: verification in 5 to 7 years (2015, p. 35).
- Young adult treated: verification in 10 to 15 years (2015, p. 35).
Treatment failure
- Treatment failure: detection of the parasite after completing treatment, with no evidence of reinfection (2015, p. 35).
- Parasitological tests are not mandatory as cure control; a positive result indicates failure (2019, p. 76).
- If treatment started with positive parasitology, repeat the study at 15 or 20 days (2019, p. 74).
- Identify abandonment and failure cases, investigate their causes and seek rescue contacts (2019, p. 75).
Cardiac and digestive forms
- For cardiac or digestive manifestations: chest teleradiography, 12-lead electrocardiogram and transthoracic echocardiogram (2019, p. 75).
- Digestive form: oesophagogastroduodenal series and endoscopy; megacolon, abdominal radiography or contrast enema (2019, p. 63; 2015, pp. 29-30).
Gap for PAHO: no national staging of cardiomyopathy; the 2015 manual declares it absent and the 2019 manual only cites Kuschnir and NYHA (2015, p. 29; 2019, p. 61).
Special situations: HIV, transplant and occupational accident
- HIV with CD4 below 200 cells/µL: prophylactic treatment 3 days per week (2019, p. 65; 2015, p. 31).
- Transplant with a reactive donor: treat the donor 60 days before; if it cannot wait, not before 14 days (2019, p. 65).
- Recipient of an infected donor: monitoring at 30 and 60 days and every 6 months, or treatment for 60 days (2019, pp. 65-66).
- Occupational accident: prophylaxis for 10 days and, with a high load (10⁷ trypomastigotes/ml), treat the acute phase for at least 60 days (2019, p. 56).
- Accident follow-up: weekly during the first month, fortnightly during the second and monthly until the fourth; discharge at 4 months without seroconversion (2019, p. 56).
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Pregnancy and Congenital Chagas
Summary
Screening
- Serology for every pregnant woman with risk factors from the first antenatal visit until the immediate puerperium (2019, p. 49; 2015, p. 23).
- Risk factors: born or living in an endemic area, vector in the home, previous transfusion or transplant (2019, p. 49; 2015, p. 23).
- Confirm a positive result with two tests of different principle (2019, p. 50).
Vertical transmission
- It can occur at any time during pregnancy, more likely in the third trimester and in successive pregnancies (2019, p. 49).
- Transplacental transmission is possible from week 22 (2015, p. 23).
- It can cause fetal growth restriction, preterm birth, low birth weight, stillbirth or foetal death (2019, p. 49).
Newborn
- Look for the parasite in cord or peripheral blood before 7 days of life, with the micromethod of choice (2019, p. 50; 2015, p. 23).
- Positive micromethod: connatal Chagas disease in the acute phase, start aetiological treatment (2019, p. 50).
- Negative micromethod: repeat at one month and, if it remains negative, serology from 6 to 10 months (2019, pp. 50-51).
Treatment
- Pregnancy contraindicates aetiological treatment; give it in the intergestational period, preferably at the end of breastfeeding (2019, p. 50).
- Refer the positive pregnant woman to the Modules of Care for High-Risk Pregnant Women (MATER) (2019, pp. 50 and 64).
- Pregnancy during treatment is a criterion for definitive suspension (2019, p. 81; 2015, p. 37).
Source: Ministry of Health of Mexico, CENAPRECE — Manual of Procedures for Chagas Disease in Mexico (2019) and Manual for the Diagnosis and Treatment of Chagas Disease (2015); in Spanish
Confirmation and ruling out of connatal Chagas disease
- Two positive tests of different principle confirm the infection (2019, p. 51).
- Ruling out requires showing absence of anti-T. cruzi antibodies during the first 10 months of life (2019, p. 39).
- Encourage the mother to return with the child at vaccination or family planning visits (2019, p. 51; 2015, p. 24).
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Pediatrics
Summary
Regimens and doses
- Full-term newborn: benznidazole 5 to 10 mg/kg/day for 60 days (2015, p. 31).
- In preterm or low-birth-weight newborns, start with half the dose (2015, p. 31).
- Start with 5 mg/kg and move to the definitive dose if after 72 hours there is no leucopenia or thrombocytopenia (2015, p. 31).
- Children and adolescents: benznidazole 10 mg/kg/day in 2 or 3 doses for 60 days, maximum 300 mg/day (2019, p. 69).
- Paediatric 12.5 mg presentation for children under 2 years or under 20 kg (2015, p. 31).
- Children tolerate higher doses and have fewer adverse effects than adults (2019, p. 69).
Diagnosis in infants
- Qualitative PCR is the confirmatory test in children under 9 months (2019, p. 41).
Follow-up
- Blood count and liver panel at every visit and at 7, 30 and 60 days (2015, p. 31).
- Visits ideally weekly or at most every 15 days (2019, p. 69).
- Serological follow-up at 6 and 12 months and then annually until negativisation is confirmed (2019, p. 51; 2015, p. 24).
- If the initial diagnosis was parasitological, repeat the study between the second and third week of treatment (2015, p. 24).
- Monitor access to the laboratory so that treatment is not delayed more than 30 days after diagnosis (2019, p. 69).
- Include anthropometry, full physical examination and questions about administration and adverse reactions (2015, p. 31).
Source: Ministry of Health of Mexico, CENAPRECE — Manual of Procedures for Chagas Disease in Mexico (2019) and Manual for the Diagnosis and Treatment of Chagas Disease (2015); in Spanish
Clinical manifestations of congenital Chagas disease
- Between 50 and 90 % of infected newborns are asymptomatic (2019, p. 64; 2015, p. 30).
- Severe cases can be fatal, with mortality of 2 to 12 % (2019, p. 64; 2015, p. 30).
- Frequent: hepatosplenomegaly 18 %, sepsis 7 %, myocarditis 4 %, hepatitis 4 %, meningoencephalitis 3 %, oedema 1.4 % (2019, p. 64; 2015, p. 30).
- Rarer: pneumonitis, chorioretinitis or vitreous body opacification (2019, p. 64; 2015, p. 30).
- In endemic areas, hepatosplenomegaly should raise suspicion of the disease (2019, p. 64).
Cardiomyopathy in children
- Consider Chagas cardiomyopathy from paediatric ages in the presence of arrhythmia, thromboembolic event, heart failure, cardiomegaly or conduction disorders (2019, p. 59).
- Perform electrocardiography and echocardiography in seropositive paediatric cases for early detection (2019, p. 62).
Gap for PAHO: no national long-term paediatric follow-up schedule; cardiomyopathy usually appears 10 to 20 years after the acute phase (2019, p. 61).
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Adverse Reactions
Summary
Pharmacovigilance
- Four groups: digestive, cutaneous, neuromuscular and haematological (2019, pp. 78-81; 2015, pp. 36-37).
- Most adverse effects appear in the first 15 to 20 days (2019, p. 71).
- Cutaneous between the fifth and tenth day; haematological from the second week (2019, p. 78; 2015, p. 36; 2019, p. 81).
- Dose-dependent polyneuritis from the fourth week, with 15 g accumulated; it is not prevented by vitamin B complex (2019, p. 80; 2015, p. 37).
- Exceptional SJS-TEN: 1 in every 1500 treatments, with centripetal desquamation, denuded skin and visceral lesions (2019, p. 79; 2015, p. 36).
- Mortality with correct treatment: 1.9 % in SJS and 6.2 % in TEN (2015, pp. 44-45).
- Suspend for uncontrollable vomiting, drug-induced hepatitis, weight loss greater than 5 % or bone marrow depression (2019, p. 81; 2015, p. 37).
- Severe skin lesions, severe neuropathic signs, SJS-TEN, pregnancy, alcoholism or drug addiction and repeatedly poor adherence also require suspension (2019, p. 81; 2015, p. 37).
- Report every adverse reaction on the Individual Case Safety Report Form (FRCIS-CH); the manual does not develop the pathway or the deadlines (2019, p. 72).
Source: Ministry of Health of Mexico, CENAPRECE — Manual of Procedures for Chagas Disease in Mexico (2019) and Manual for the Diagnosis and Treatment of Chagas Disease (2015); in Spanish
Management by group
- Digestive: take the medicine after meals, avoid alcohol; aluminium hydroxide or metoclopramide if necessary (2019, p. 78; 2015, p. 38).
- Mild cutaneous: general measures, moisturising creams and avoid sun and heat, without reducing the dose (2019, p. 79; 2015, p. 39).
- Moderate cutaneous: suspend temporarily and add chlorphenamine or loratadine; restart when resolved (2019, p. 80; 2015, p. 39).
- Severe cutaneous: systemic corticosteroids (prednisone, dexamethasone) (2019, p. 80; 2015, p. 40).
- Neuromuscular: rest and paracetamol or ibuprofen; they rarely require hospital admission (2019, p. 81; 2015, p. 37).
SJS and TEN: hospital management
- Admit to a Burns Unit and assess Intensive Care (2015, pp. 44-45).
- Stop benznidazole and assess any other suspected treatment (2015, pp. 44-45).
- Infuse fluids according to basal needs with electrolyte monitoring; antibiotics if there is fever or an infectious focus (2015, pp. 44-45).
- Analgesia, antihistamines, ophthalmological assessment, mouthwashes with bicarbonate water and dressings with saline solution (2015, pp. 44-45).
- Systemic corticosteroid therapy is of controversial benefit (2015, p. 45).
Anaphylaxis
No cases have been reported with trypanocidal drugs, but the manual describes adrenaline 0.01 mg/kg subcutaneously, maximum 0.3 mg, repeatable every 15 minutes; do not exceed the dose because of the risk of arrhythmias and always dilute the intravenous route (2015, p. 46).
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Surveillance
Summary
Notification
- Notify acute and chronic cases to SUIVE (2019, p. 83; 2015, p. 47).
- Notification has a 7-day deadline (2019, p. 73).
- The jurisdictional epidemiologist issues the Immediate Case Notification under NOM-017-SSA2-2012 (2019, p. 84; 2015, p. 48).
- The confirmed case is reported urgently to the jurisdictional and state level (2019, p. 84; 2015, p. 48).
Case study
- Comprehensive clinical study, socioeconomic and cultural analysis, and study of household contacts (2019, pp. 83-84; 2015, pp. 47-48).
- Investigate the vector and reservoirs in the home and its surroundings, and housing conditions (2019, pp. 83-84; 2015, pp. 47-48).
- When several acute cases occur simultaneously, suspect an outbreak through oral transmission (2019, p. 83; 2015, p. 47).
Source: Ministry of Health of Mexico, CENAPRECE — Manual of Procedures for Chagas Disease in Mexico (2019) and Manual for the Diagnosis and Treatment of Chagas Disease (2015); in Spanish
During outbreaks
- Carry out an epidemiological survey with random seroepidemiological samples and a search for vectors and reservoirs (2019, p. 85; 2015, p. 48).
- In settlements with 500 inhabitants, cover the whole locality (2019, p. 85; 2015, p. 48).
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