Clustering of Toxoplasma gondii Infections Within Families of Congenitally Infected Infants

Clin Infect Dis. 2015 Dec 15;61(12):1815-24. doi: 10.1093/cid/civ721. Epub 2015 Sep 24.


Background: Family clusters and epidemics of toxoplasmosis in North, Central, and South America led us to determine whether fathers of congenitally infected infants in the National Collaborative Chicago-Based Congenital Toxoplasmosis Study (NCCCTS) have a high incidence of Toxoplasma gondii infection.

Methods: We analyzed serum samples collected from NCCCTS families between 1981 and 2013. Paternal serum samples were tested for T. gondii antibodies with immunoglobulin (Ig) G dye test and IgM enzyme-linked immunosorbent assay. Additional testing of paternal serum samples was performed with differential-agglutination and IgG avidity tests when T. gondii IgG and IgM results were positive and serum samples were collected by the 1-year visit of the congenitally infected child. Prevalence of paternal seropositivity and incidence of recent infection were calculated. We analyzed whether certain demographics, maternal parasite serotype, risk factors, or maternal/infant clinical manifestations were associated with paternal T. gondii infection status.

Results: Serologic testing revealed a high prevalence (29 of 81; 36%) of T. gondii infection in fathers, relative to the average seropositivity rate of 9.8% for boys and men aged 12-49 years in the United States between 1994 and 2004 (P < .001). Moreover, there was a higher-than-expected incidence of recent infections among fathers with serum samples collected by the 1-year visit of their child (6 of 45; 13%; P < .001). No demographic patterns or clinical manifestations in mothers or infants were associated with paternal infections, except for sandbox exposure.

Conclusions: The high prevalence of chronic and incidence of recent T. gondii infections in fathers of congenitally infected children indicates that T. gondii infections cluster within families in North America. When a recently infected person is identified, family clustering and community risk factors should be investigated for appropriate clinical management.

Keywords: Toxoplasma gondii; clusters; congenital infections; toxoplasmosis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Agglutination Tests
  • Antibodies, Protozoan / blood
  • Chicago / epidemiology
  • Child
  • Child, Preschool
  • Cluster Analysis*
  • Cohort Studies
  • Enzyme-Linked Immunosorbent Assay
  • Family Health*
  • Fathers*
  • Female
  • Humans
  • Immunoglobulin G / blood
  • Immunoglobulin M / blood
  • Incidence
  • Infant
  • Infant, Newborn
  • Male
  • Pregnancy
  • Prevalence
  • Toxoplasmosis / epidemiology*


  • Antibodies, Protozoan
  • Immunoglobulin G
  • Immunoglobulin M