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Congenital infection

Treatment must begin as soon as the diagnosis is performed, when the clinical suspicion is confirmed by observation of the parasite in fresh samples of blood smears, microstrout, etc. Sometimes the diagnosis is confirmed when the child is in the chronic period (8 or more months) by persistent positive serology after this period. Better therapeutic results are obtained when the diagnosis is more precocious. It is important to perform a clinical, serological, and parasitological follow-up of the treated newborn. Recently the utility of PCR in the precocious diagnosis of congenital Chagas disease in neonates has been confirmed. Its effectiveness is greater than that of xenodiagnosis.62,63 This technique has great utility as has been demonstrated by Paraguayan investigators and others in the follow-up of treated cases. In an investigation performed in the maternity ward of the Clinical Hospital of Asuncion and in the Regional Hospital of San Pedro, Paraguay, the newborn of chagasic mothers were studied. Three percent were positive by microscopy, which increased to 10 percent when they added the cases with persistent positive serology at 6 months. Of 58 newborn, in two cases T. cruzi was observed at birth and four presented positive PCR with negative microscopic investigation. All the positive cases

Table 31.3 Adverse reactions to nifurtimox and benznidazole

Digestive alterations

Gastric upset



Hematologic alterations (by hypersensitivity)




Dermatological alterations

Erythematus, light-sensitive rash

Atopic dermatitis (mild or severe)

Occasionally Stevens-Johnson syndrome, which requires the suspension of therapy

Neurological alterations

Polyneuropathy, dose dependent

In general it appears in schedules of high dosages

In the usual dose of 5 mg/kg/day of benznidazole, 10—30% of the patients present neuropathies, especially at the end of treatment

were treated with BNZ and followed for 4 years by conventional serology and PCR.

In another study performed in an endemic area of Paraguay, of 1865 neonates with chagasic mothers, there were 104 cases where congenital infection was demonstrated by direct microscopic observation, PCR, and serology: ELISA, ELISA AIDS, and IF. PCR was the most sensitive test.64

All congenital cases must be treated, since up to 98% of such treatments may produce negative serology and parasitemia; the earlier the treatment is begun, the better the response obtained. NF must be administered in doses of 8—10 mg/kg/day for 60 days, taken every 8 or 12 h, or BNZ 5—10 mg/kg/day for 60 days. In a survey performed in Cochabamba, Bolivia, in 2013, success was obtained in congenital cases treated with 7.5 mg/kg/day during 30 days. If this result is confirmed by other investigations, we could have a shorter treatment with low cost.65 To avoid secondary effects (convulsions) it is recommended to associate phenobarbital in therapeutic doses during the first 15 days of treatment. In case of secondary dermatological reactions, it is suggested to add antihistamines. Adverse reactions in neonates are fewer than in adults.

It is important to perform a precocious diagnosis of congenital cases to treat them as quickly as possible.66 In pregnant women, conduct a serological test jointly with other tests such as VDRL during the first trimester of pregnancy and conduct follow-up of the positive cases until the diagnosis of congenital infection is confirmed or discarded. This activity must be performed in all women of fertile age, in pregnant women from endemic areas, and in women with a history of having lived in these zones.

In a newborn, run a serological study for T. cruzi infection, together with VDRL and other tests. In the positive cases a follow-up must be realized until confirmation or refutation of the diagnosis.

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