Serological and Parasitological Screening of Trypanosoma cruzi Infection in Mothers and Newborns Living in Two Chagasic Areas of Mexico

Seroprevalence of Trypanosoma cruzi among children from Veracruz, Mexico: Epidemiological baseline for a control model based on Chagas disease active transmission

Introduction. In 2021, the Secretaría de Salud de México and the Pan American Health Organization launched an initiative to interrupt intra-domiciliary vector transmission of Trypanosoma cruzi based on the prevalence of Chagas disease in children. The Mexican State of Veracruz was leading this initiative. Objective. To estimate the seroprevalence of T. cruzi infection among children under 15 years of age from rural areas of Veracruz, México. Materials and methods. We identified eight localities of high priority from the Municipality of Tempoal, Veracruz, for baseline serology. Blood samples were collected on filter paper from 817 individuals between June and August 2017, for screening with a third-generation enzyme immunoassay. Reactive cases were confirmed by indirect hemagglutination, enzyme-linked immunosorbent assay, and indirect immunofluorescence tests on peripheral blood serum samples. We calculated seroprevalence and 95% confidence intervals (CI). Results. We confirmed Chagas disease cases in children under 15 years of age with a seroprevalence of 1,9% (95 % CI = 1,12-3,16) in the localities of Citlaltepetl, Cornizuelo, Cruz de Palma and Rancho Nuevo. Conclusions. These results indicate recent transmission of T. cruzi in these communities and allow to establish an epidemiological baseline for the design and implementation of a model focused on geographical areas with active transmission to advance toward the elimination of intra-domiciliary vector transmission of this parasite in Mexico.

Emerging and reemerging forms of Trypanosoma cruzi transmission

This review aims to update and discuss the main challenges in controlling emergent and reemergent forms of Trypanosoma cruzi transmission through organ transplantation, blood products and vertical transmission in endemic and non-endemic areas as well as emergent forms of transmission in endemic countries through contaminated food, currently representing the major cause of acute illness in several countries. As a neglected tropical disease potentially controllable with a major impact on morbimortality and socioeconomic aspects, Chagas disease (CD) was approved at the WHO global plan to interrupt four transmission routes by 2030 (vector/blood transfusion/organ transplant/congenital). Implementation of universal or target screening for CD are highly recommended in blood banks of non-endemic regions; in organ transplants donors in endemic/non-endemic areas as well as in women at risk from endemic areas (reproductive age women/pregnant women-respective babies). Moreover, main challenges for surveillance are the application of molecular methods for identification of infected babies, donor transmitted infection and of live parasites in the food. In addition, the systematic recording of acute/non-acute cases and transmission sources is crucial to establish databases for control and surveillance purposes. Remarkably, antiparasitic treatment of infected reproductive age women and infected babies is essential for the elimination of congenital CD by 2030.

Estimating the current burden of Chagas disease in Mexico: A systematic review and meta-analysis of epidemiological surveys from 2006 to 2017

Background

In Mexico, estimates of Chagas disease prevalence and burden vary widely. Updating surveillance data is therefore an important priority to ensure that Chagas disease does not remain a barrier to the development of Mexico's most vulnerable populations.

Methodology/Principal findings

The aim of this systematic review and meta-analysis was to analyze the literature on epidemiological surveys to estimate Chagas disease prevalence and burden in Mexico, during the period 2006 to 2017. A total of 2,764 articles were screened and 36 were retained for the final analysis. Epidemiological surveys have been performed in most of Mexico, but with variable study scale and geographic coverage. Based on studies reporting confirmed cases (i.e. using at least 2 serological tests), and taking into account the differences in sample sizes, the national estimated seroprevalence of Trypanosoma cruzi infection was 3.38% [95%CI 2.59–4.16], suggesting that there are 4.06 million cases in Mexico. Studies focused on pregnant women, which may transmit the parasite to their newborn during pregnancy, reported an estimated seroprevalence of 2.21% [95%CI 1.46–2.96], suggesting that there are 50,675 births from T. cruzi infected pregnant women per year, and 3,193 cases of congenitally infected newborns per year. Children under 18 years had an estimated seropositivity rate of 1.51% [95%CI 0.77–2.25], which indicate ongoing transmission. Cases of T. cruzi infection in blood donors have also been reported in most states, with a national estimated seroprevalence of 0.55% [95%CI 0.43–0.66].

Conclusions/Significance

Our analysis suggests a disease burden for T. cruzi infection higher than previously recognized, highlighting the urgency of establishing Chagas disease surveillance and control as a key national public health priority in Mexico, to ensure that it does not remain a major barrier to the economic and social development of the country's most vulnerable populations.

In Mexico, estimates of Chagas disease prevalence and burden vary widely due to the ecology and epidemiology of this disease resulting of many geographical, ecological, biological, and social interactions. Better data are thus urgently needed to help develop appropriate public health programs for disease control and patient care. In this study we performed a meta-analysis from published data on T. cruzi infection seroprevalence in Mexico between 2006 and 2017. This systematic review shows a national estimated seroprevalence of T. cruzi infection of 3.38% [95%CI 2.59–4.16], with over 4.06 million cases in Mexico, which is higher than previously recognized. The presence of T. cruzi infection in specific subpopulations such as pregnant women, children and blood donors also informs on specific risks of infection and calls for the implementation of well-established control interventions. This work confirms the place of Mexico as the country with the largest number of cases, highlighting the urgency of establishing Chagas disease control as a key national public health priority.

Congenital Transmission of Trypanosoma cruzi in Argentina, Honduras, and Mexico: An Observational Prospective Study

Compared with South America, there is a lack of epidemiologic studies about the risk of congenital transmission of Trypanosoma cruzi in Central America and Mexico. It has been suggested that T. cruzi genotypes might differ by region and that congenital transmission might vary according to the parasite's genotype. Our objective was to compare T. cruzi congenital transmission rates in three countries. We performed an observational prospective study in 2011-2014 enrolling women at delivery in one hospital in Argentina, two hospitals in Honduras, and two hospitals in Mexico. Congenital T. cruzi infection was defined as the presence of one or more of the following criteria: presence of parasites in cord blood (direct parasitological microscopic examination) with positive polymerase chain reaction (PCR) in cord blood, presence of parasites in infant's blood at 4-8 weeks (direct parasitological microscopic examination), and persistence of T. cruzi-specific antibodies at 10 months, as measured by at least two tests. Among 28,145 enrolled women, 347 had at least one antibody rapid test positive in cord blood and a positive enzyme-linked immunosorbent assay in maternal blood. PCR in maternal blood was positive in 73.2% of the cases, and genotyping identified a majority of non-TcI in the three countries. We found no (0.0%; 95% confidence interval [CI]: 0.0, 2.0) confirmed congenital case in Honduras. Congenital transmission was 6.6% (95% CI: 3.1, 12.2) in Argentina and 6.3% (95% CI: 0.8, 20.8) in Mexico. Trypanosoma cruzi non-TcI predominated and risks of congenital transmission were similar in Argentina and Mexico.

Diagnosis of Congenital Chagas Disease Using an Iron Superoxide Dismutase Excreted as Antigen, in Mothers and Their Children During the First Year of Life

BACKGROUND

Chagas disease caused by Trypanosoma cruzi is endemic in Latin America. Human infection is mainly spread by Triatominae insects. Other forms of transmission are congenital, blood transfusion and organ transplantation.

METHODS

Anti-T. cruzi antibodies were determined by enzyme-linked immunosorbent assay (ELISA) and Western blot (WB) in 155 serum samples from mothers and their babies. Indirect immunofluorescence (IFA) and a commercial test were used to validate efficacy of a specific ELISA-iron-excreted superoxide dismutase assay. Sera from babies were collected at 6 and 12 months, whereas maternal samples were obtained after delivery. Calostrum and umbilical cord samples were simultaneously obtained.

RESULTS

Anti-T. cruzi antibodies were detected in 8 (5.16%) mothers by ELISA-WB, in 7 (4.51%) using IFA and in 1 (0.64%) by a commercial kit. Nine (5.80%) 6-month-old children were positive by ELISA-WB and 7 (4.51%) by IFA; negative results were obtained when the commercial kit was used. At 12 month of age, 15 (9.67%) children were positive by ELISA-WB, 13 (8.38%) by IFA and 1 (0.64%) by the commercial test. Antibodies were detected in 4 mothers whose children were serologically negative. Four other mothers and their children were positive, but only one of them had detected antibodies in umbilical cord up to 12 months, thus assuming vertical transmission.

CONCLUSIONS

The use of iron-excreted superoxide dismutase as antigen in serologic tests for detection of T. cruzi yielded promising results as diagnostic procedure.

Mother-to-Child Transmission of Chagas Disease in El Salvador

To estimate the incidence (any mother to child) and rate (from seropositive mother to child) of mother-to-child transmission of Trypanosoma cruzi, a serological census was conducted, targeting pregnant women and infants born to seropositive mothers, in four municipalities of El Salvador. Of 943 pregnant women, 36 (3.8%) were seropositive for T. cruzi. Of 36, 32 proceeded to serological tests of their infants when they became 6-8 months of age. Six infants seropositive at the age of 6-8 months further proceeded to second-stage serological test at the age of 9-16 months. As the result, one infant was congenitally infected. Thus, serological tests at the age of 6-8 months produced five false positives. To ensure earlier effective medication only for true positives, identification of seropositive infants at the age of 9-16 months is crucial. Incidence and rate of mother-to-child transmission were 0.14 (per 100 person-years) and 4.0%, respectively. Estimated number of children infected through mother-to-child transmission in El Salvador (170 per year) was much higher than that of human immunodeficiency virus (HIV; seven per year). It is recommended that serological testing for T. cruzi be integrated into those for HIV and syphilis as part of antenatal care package.

Trypanosoma cruzi-infected pregnant women without vector exposure have higher parasitemia levels: implications for congenital transmission risk

BACKGROUND

Congenital transmission is a major source of new Trypanosoma cruzi infections, and as vector and blood bank control continue to improve, the proportion due to congenital infection will grow. A major unanswered question is why reported transmission rates from T. cruzi-infected mothers vary so widely among study populations. Women with high parasite loads during pregnancy are more likely to transmit to their infants, but the factors that govern maternal parasite load are largely unknown. Better understanding of these factors could enable prioritization of screening programs to target women most at risk of transmission to their infants.

METHODOLOGY/PRINCIPAL FINDINGS

We screened pregnant women presenting for delivery in a large urban hospital in Bolivia and followed infants of infected women for congenital Chagas disease. Of 596 women screened, 128 (21.5%) had confirmed T. cruzi infection; transmission occurred from 15 (11.7%) infected women to their infants. Parasite loads were significantly higher among women who transmitted compared to those who did not. Congenital transmission occurred from 31.3% (9/29), 15.4% (4/26) and 0% (0/62) of women with high, moderate and low parasite load, respectively (χx2 for trend 18.2; p<0.0001). Twin births were associated with higher transmission risk and higher maternal parasite loads. Infected women without reported vector exposure had significantly higher parasite loads than those who had lived in an infested house (median 26.4 vs 0 parasites/mL; p<0.001) with an inverse relationship between years of living in an infested house and parasite load.

CONCLUSIONS/SIGNIFICANCE

We hypothesize that sustained vector-borne parasite exposure and repeated superinfection by T. cruzi may act as an immune booster, allowing women to maintain effective control of the parasite despite the down-regulation of late pregnancy.

Frequency of the congenital transmission of Trypanosoma cruzi: a systematic review and meta-analysis

BACKGROUND

Chagas disease is caused by the parasite Trypanosoma cruzi and is endemic in much of Latin America. With increased globalisation and immigration, it is a risk in any country, partly through congenital transmission. The frequency of congenital transmission is unclear.

OBJECTIVE

To assess the frequency of congenital transmission of T. cruzi.

SEARCH STRATEGY

PubMed, Journals@Ovid Full Text, EMBASE, CINAHL, Fuente Academica and BIREME databases were searched using seven search terms related to Chagas disease or T. cruzi and congenital transmission.

SELECTION CRITERIA

The inclusion criteria were the following: Dutch, English, French, Portuguese or Spanish language; case report, case series or observational study; original data on congenital T. cruzi infection in humans; congenital infection rate reported or it could be derived. This systematic review included 13 case reports/series and 51 observational studies.

DATA COLLECTION AND ANALYSIS

Two investigators independently collected data on study characteristics, diagnosis and congenital infection rate. The principal summary measure--the congenital transmission rate--is defined as the number of congenitally infected infants divided by the number of infants born to infected mothers. A random effects model was used.

MAIN RESULTS

The pooled congenital transmission rate was 4.7% (95% confidence interval: 3.9-5.6%). Countries where T. cruzi is endemic had a higher rate of congenital transmission compared with countries where it is not endemic (5.0% versus 2.7%).

CONCLUSIONS

Congenital transmission of Chagas disease is a global problem. Overall risk of congenital infection in infants born to infected mothers is about 5%. The congenital mode of transmission requires targeted screening to prevent future cases of Chagas disease.

Trypanosoma cruzi connatal transmission in dogs with Chagas disease: experimental case report

Trypanosoma cruzi connatal transmission was studied in male and female mongrel dogs. Both dogs were experimentally infected, after which on the 20(th) day, lymphoadenomegaly and fever were found. Four months postinfection, they mated. At this time, Chagas disease was confirmed by two different diagnostic tests. The electrocardiogram and echocardiogram taken at the eight postinoculation month showed data consistent with ischemia, local conduction abnormalities and hypertrophy, as well as a diminished ejection fraction and left ventricular dilation, respectively. Four puppies were born and after weaning had weakness, progressive weight loss, and chronic diarrhea. Necropsy of all four showed digestive alterations and cardiac dilation. Serology in the offspring was positive for Chagas disease. The histopathological study demonstrated a cardiac chronic inflammatory process, although no parasites were found. Clinical data and serological determinations are consistent with death from advanced Chagas disease.

Maternal fetal transmission of Trypanosoma cruzi: a problem of public health little studied in Mexico

The first case of neonatal Chagas was reported in Mexico in 1998, but there have been no studies since then. Therefore, we investigated the rates of congenital infection of Trypanosoma cruzi by examining the seroprevalence among 1448 pregnant women in Oaxaca, Jalisco and Mexico City. We performed ELISAs to screen for recombinant and total antigens in mothers, and examined the frequency of congenital T. cruzi transmission by PCR with cord blood and antibody testing in children when they reached two years old. Our results showed that the prevalence of infection in pregnant women was 7.32% (106/1448) overall, and 4.4% (35/794) in Oaxaca, 12.02% (67/557) in Jalisco and 4.12% (4/97) in the Mexico City. In Oaxaca, T. cruzi infection was detected by PCR in 20% (7/35) of infants born to seroreactive mothers and 11.9% (8/67) in Jalisco. No infections were identified in infants from the Mexico City. From these only eleven serological follow up their children are agree to take blood. Therefore, the maternal-fetal overall transmission rate was 4.08% (4/98) in Oaxaca and 9.1% (3/33) in Jalisco 1.5% (1/65) children with positive serology were given specific treatment Chagas. In conclusion, these are the first reports of the rates of congenital Chagas disease in Mexico. The seroprevalence was higher in mothers from Jalisco, and could be related to that there is not the periodic fumigation of the transmitting vector performed in that state. The high rates of maternal-fetal transmission found in Oaxaca could be related to the differences of pathogenicity of trypanosome. No association between both the rate of congenital transmission and the gynecologic anthropometric data was observed.

Acute and congenital Chagas disease

The acute phase of Chagas disease lasts 4-8 weeks and is characterized by microscopically detectable parasitaemia. Symptoms are usually mild with severe acute disease occurring in less than 1% of patients. Orally transmitted Trypanosoma cruzi outbreaks can have more severe acute morbidity and higher mortality than vector-borne infection. Congenital T. cruzi infection occurs in 1-10% of infants of infected mothers. Most congenital infections are asymptomatic or cause non-specific signs, requiring laboratory screening for detection. A small proportion of congenital infections cause severe morbidity with hepatosplenomegaly, anaemia, meningoencephalitis and/or respiratory insufficiency, with an associated high mortality. Infected infants are presumed to carry the same 20-30% lifetime risk of cardiac or gastrointestinal disease as other infected individuals. Most control programs in Latin America employ prenatal serological screening followed by microscopic examination of cord blood from infants of seropositive mothers. Recent data confirm that polymerase chain reaction (PCR) is more sensitive and detects congenital infections earlier than conventional techniques. For infants not diagnosed at birth, conventional serology is recommended at at 6 to 9 months of age. In programs that have been evaluated, less than 20% of at risk infants completed all steps of the screening algorithm. A sensitive, specific and practical screening test for newborns is needed to enable Chagas disease to be added to newborn screening programs.

Identification of a hyperendemic area for Trypanosoma cruzi infection in central Veracruz, Mexico

The state of Veracruz, Mexico, is a well-recognized endemic region for Chagas disease, but the geographic distribution of the disease and its magnitude are still poorly documented. We evaluated the seroprevalence of Trypanosoma cruzi infection in the sanitary jurisdictions of Cordoba and Cosamaloapan in central Veracruz. A total of 654 serum samples from 19 rural localities were tested by using four tests: two enzyme-linked immunosorbent assays, an indirect immunofluorescent, and Western blotting. Overall, 110 (16.8%) of 654 samples were positive for T. cruzi by >/= 2 tests (95% confidence interval = 14.2-19.9%). The municipality of Tezonapa in the jurisdiction of Cordoba was identified as a potential hyperendemic region with seroprevalence rates </= 45% in young children. No cases were detected in the jurisdiction of Cosamaloapan. Further studies should help clarify T. cruzi transmission dynamics in Tezonapa. The magnitude of T. cruzi infection rate in this region calls for the urgent implementation of extensive epidemiologic surveillance and control programs.

Mother-to-Child Transmission of Chagas’ Disease in North America: Why Don’t We Do More?

OBJECTIVES

Mothers with Chagas' disease can transmit Trypanosoma cruzi to their fetuses, who often become carriers of the infection and are then at risk of developing severe cardiac disease later in the course of their lives. If identified early enough after birth, the infected newborns can be treated and cured. Our objective was to review the data available in Canada, Mexico, and the United States and to discuss the need for prevention programs.

METHODS

We reviewed the literature and estimated the number of seropositive mothers and newborns infected by T. cruzi.

RESULTS

We estimate that about 40,000 pregnant women and 2,000 newborns are likely to be infected by T. cruzi in North America. We have not identified any ongoing prevention programs.

CONCLUSIONS

Mother-to-child transmission of T. cruzi has all the characteristics required to be a public health priority, as it is relatively frequent, severe, identifiable, and treatable. In reality, it is a neglected disease and a missed opportunity. It is urgent to better understand the epidemiology of mother-to-child transmission of T. cruzi in North America and to develop effective prevention programs.