Tuesday, June 22, 2010

Congenital syphilis, upward trend (again) in the United States

Syphilis can be deadly if passed from an infected mother to her unborn child. The most recent CDC data show that 6.5% of U.S. infants with congenital syphilis (CS) in 2008 were stillborn or died within 30 days of birth.1

Newborns with CS who are destined to live begin to show signs of disease within the first few weeks of life.  The main features of CS in early infancy include fever, skin lesions, enlarged liver and spleen, and a chronic runny nose ("snuffles"), which may be tinged with blood.  Bone lesions may lead to Parrot's pseudoparalysis, a condition so painful that the infant will refuse to move the affected extremities.  Ongoing damage to bony tissue may later lead to childhood deformities including saddle nose, sabre shins, and Hutchinson incisors (notched central incisors).  Other late signs of CS include inflammation of the cornea and sudden hearing loss.

The lesions and deformities associated with congenital syphilis are sparked by Treponema pallidum, a spirochete that can cross the placenta from the mother's bloodstream.  The probability of transmission to the fetus depends on how long the mother has been infected with T. pallidum.  The risk of transmission is lower in mothers at later stages of syphilis.  After crossing the placenta, the spirochete invades the fetal organs.  The continuing immune response to persistent T. pallidum infection causes the damage seen in CS.  Early treatment of the mother with penicillin, at least 30 days before delivery, is essential to stop the disease.

The rate of congenital syphilis in the United States has started to creep back up after plummeting over two decades.1  The incidence of congenital syphilis has gone up from 8.2 cases per 100,000 live births in 2005 to 10.1 in 2008 with most of the increase having occurred in the South.  CS rates in infants born to black mothers have gone up from 26.6 in 2005 to 34.6 per 100,000 live births in 2008 and now account for half of all CS cases.  Since CS is transmitted from mothers with syphilis, CS rates have historically tracked the combined primary and secondary syphilis rate seen in women, which has also started to climb (see figure below).  What factors account for the increased incidence of syphilis?  In one Alabama county, increased syphilis rates in black women were linked to crack cocaine use and the exchange of sex for money or drugs.2  Although more studies are needed to determine whether the same factors are linked to syphilis throughout the South, it should be pointed out that the same factors were associated with the previous syphilis epidemic that peaked in the early 1990s, when there were several thousand yearly cases of CS as opposed to the several hundred seen today.3

Figure from CDC1

Now that the upward trend in the CS rate has been recognized, public health authorities in partnership with community-based groups must allocate some of their scarce resources to reverse the trend.  With prenatal care and prompt treatment, congenital syphilis can be prevented.

1. Centers for Disease Control and Prevention (CDC) (April 16, 2010). Congenital syphilis - United States, 2003-2008. MMWR Morbidity and Mortality Weekly Report 59(14):413-417.  link

2. Centers for Disease Control and Prevention (CDC) (May 8, 2009).  Primary and secondary syphilis - Jefferson County, Alabama, 2002-2007.  MMWR Morbidity and Mortality Weekly Report 58(17):463-467.  link

3. Nakashima, A.K., Rolfs, R.T., Flock, M.L., Kilmarx, P., and Greenspan, J.R. (Jan-Feb 1996). Epidemiology of syphilis in the United States, 1941-1993.  Sexually Transmitted Diseases 23(1):16-23.  PMID: 8801638