Mother-to-child transmission and gestational syphilis: Spatial-temporal epidemiology and demographics in a Brazilian region

Abstract

Syphilis is a Sexually Transmitted Infection (IST) with significant importance to public health, due to its impact during pregnancy (Gestational Syphilis-GS); especially because syphilis can affect fetus and neonates' development (mother-to-child transmission-MTCT of syphilis), by increasing susceptibility to abortion, premature birth, skeletal malformations, meningitis and pneumonia. Measures to control and eliminate MTCT of syphilis have failed on the last few years in Brazil and this research aimed to identify the seasonality of notified cases of syphilis in a region of São Paulo state. The studied region, Pontal do Paranapanema, comprises 32 cities located in the West of São Paulo state, in Brazil. Data collected from the National System of Aggravations and Notification (SINAN) website was used to calculate the incidence rate of GS and MTCT. The incidence rate of GS was acquired dividing number of cases by number of women in each municipality and MTCT using number of live births in each year (from 2007 to 2013) in each municipality. This result was then, standardized multiplying incidence rate by 10,000 and expressed as incidence/10,000 women or live births, for GS and MTCT, respectively. To identify possible endemic/epidemic periods, a control diagram was performed using the standard deviation (SD) of incidence rate. Thematic maps representing the spatial distribution of incidence rates were constructed using a Geographic Information System software (GIS, based on cartographic vector available on the Brazilian Institute of Geography and Statistics (IBGE) website. Eighty cases of GS and 61 cases of MTCT were notified in the studied region. An increase of GS notification was detected in the Pontal do Paranapanema in 2011 followed by an increase in number of MTCT cases in the subsequent year, suggesting inefficacy in the treatment during gestational period. Most of those cases were reported on February and November which suggested seasonality for this IST in the region. The control diagram, based on the inputs collected from SINAN, showed no endemic period; however, the most susceptible month to happen an endemic event of GS and MTCT was February. Our study provided a new methodology to understand the syphilis dynamics as a potential tool to improve the success of future measures to control and possibly eliminate MTCT of syphilis.

Fig 1. Pontal do Paranapanema location in São Paulo state and Brazil.

The region is in the west side of the state, which in its turn, is located in the Southeast of Brazil.

Fig 2. Dispersion graph showing the standardized average incidence of gestational syphilis (GS) per 10,000 habitants and mother-to-child transmission (MTCT) of syphilis per 10,000 living births reported by Pontal do Paranapanema cities from 2007 to 2013.

Notification of cases increased after 2009 with peak of GS in 2011 and MTCT of syphilis in the subsequent year (2012). Database: 1) population: Brazilian Institute of Geography and Statistics—IBGE (2010); 2) notified cases: National System of Aggravations and Notification–SINAN (2017).

Fig 3. Dispersion graph showing the seasonal incidence of gestational syphilis (GS) from 2008 to 2013 in the Pontal do Paranapanema cities and mother-to-child transmission (MTCT) of syphilis from 2007 to 2013.

Year of 2008 was excluded for GS because of the lack of monthly information. Highest number of cases were reported in February for both GS and MTCT of syphilis, followed by November for GS (late Spring and Summer). On the contrary, from March to October (Autumn and Winter) cases of GS and MTCT of syphilis did not reach half of February’s notifications. Database: 1) population: Brazilian Institute of Geography and Statistics—IBGE (2010); 2) notified cases: National System of Aggravations and Notification–SINAN (2017).

Fig 4. Control chart of monthly cases of gestational syphilis notified in the Pontal do Paranapanema from 2008 to 2013.

SI = Seasonal index; UAL = Upper Alert Limit; UCL = Upper Control Limit. Highest amplitude of cases was identified in February followed by November, without overlap of UAL and UCL. Lowest amplitude was noticed in September and October. Inferior alert and control limits are not present as that results were lower than zero. Databases: Brazilian Institute of Geography and Statistics—IBGE (2010) and National System of Aggravations and Notification–SINAN (2017).

Fig 5. Control chart of monthly cases of MTCT of syphilis notified in the Pontal do Paranapanema from 2008 to 2013.

SI = Seasonal index; UAL = Upper Alert Limit; UCL = Upper Control Limit. Highest amplitude of cases was identified in February followed by November, without overlap of UAL and UCL. Lowest amplitude was noticed in September. Inferior alert and control limits are not present as that results were lower than zero. Databases: Brazilian Institute of Geography and Statistics—IBGE (2010) and National System of Aggravations and Notification–SINAN (2017).

Fig 6. Pontal do Paranapanema cities and the spatial distribution of gestational syphilis reported cases from 2007 to 2013.

The highest incidence of cases among the cities is represented by Rancharia (red), followed by Ribeirão dos Índios and Teodoro Sampaio (orange). The lowest index average incidences were identified in Martinópolis, Presidente Prudente, Presidente Bernardes e Mirante do Paranapanema (beige). Cities that reported cases of GS are located in the state border with Mato Grosso do Sul (West) and Parana (South). Databases: Brazilian Institute of Geography and Statistics—IBGE (2010) and National System of Aggravations and Notification–SINAN (2017).

Fig 7. Pontal do Paranapanema cities and the spatial distribution of mother-to-child transmission (MTCT) of syphilis reported cases from 2007 to 2013.

The highest incidences of cases were represented by Sandovalina, Narandiba e Santo Expedito (black) followed by Tarabai and Teodoro Sampaio (burgundy). Presidente Prudente, Regente Feijó and Martinópolis reported an index of 7.54 to 15.25 (salmon) and, the lowest index average incidences were identified in Santo Anastácio, Álvares Machado, Rancharia e Mirante do Paranapanema (salmon). Cities that reported cases of MTCT of syphilis are located mainly in the border with Parana state (South). Databases: Brazilian Institute of Geography and Statistics—IBGE (2010) and National System of Aggravations and Notification–SINAN (2017).