Prevalence and Epidemiology of Toxoplasmosis in Pregnant Women
Department of Clinical Surgical Sciences, School of Medicine, Faculty of Medical Sciences,
The University of the West Indies, St. Augustine, Trinidad and Tobago.
Toxoplasmosis is the most widespread zoonosis and an important human disease, particularly in
children in whom it could cause visual and neurological impairment and mental retardation. This
study was conducted to determine the seroprevalence of toxoplasmosis in pregnant women and
cord blood of newborns.
The investigation comprised three phases, the first phase determined the seroprevalence of
Toxoplasma gondii agglutinins (IgG and IgM) in pregnant women in their first trimester at two
clinics in the country, Port of Spain General Hospital and Mount Hope Women’s hospital; during
the second phase, the seroprevalence of T. gondii in cord blood of children delivered at both
health institutions was determined between November 2002 and September 2003. In the third
phase, between October 2003 and February 2005, a longitudinal study was conducted on pregnant
women at five health centres (Barataria, St. Joseph, El Socorro, Success Laventille and Upper
Laventille) in which sera were collected during the first (0-12 weeks), second (13-28 weeks) and
third (29-40 weeks) trimesters and the seroprevalence of T. gondii agglutinins was determined.
For each pregnant woman sampled and in the case of cord blood, the mothers of the children, a
comprehensive questionnaire was administered to elicit demographic data and risk factors for
exposure to T. gondii. All serum samples were assigned random numbers and each divided into
aliquots and stored at -20oC until tested. The enzyme-immuno assay (EIA) was used to detect T.
gondii agglutinins, specifically, IgG and IgG from all sources. The demographic data and risk
factors were related to the seroprevalence of T. gondii agglutinins and the data subjected to
Clotted blood samples were collected by venipuncture from antenatal women in the first trimester
at clinics in Port of Spain Hospital and the Mount Hope Women’s Hospital. During the study
period, November 2002 to September 2003, cord blood was also collected from placentas at the
delivery rooms of both health institutions. Of 630 serum samples from 126 pregnant women
attending antenatal clinics and 504 cord blood samples collected, a majority of women was aged
21-30 years old (50.6%). Other demographic features included Africans (45.9%), single status
(31.6%), Christians (82.1%), educated up to secondary level (68.1%), house wives (21.9%) and
having only one child (43.3%). From a questionnaire survey, only 32 (5.1%) had any knowledge
of toxoplasmosis and 70 (11.1%) knew of having been screened for Toxoplasma gondii, rubella
virus, cytomegalovirus and herpes simplex virus, “TORCH”. A total of 90 (14.3%) and 19
(3.0%) women had cats in their households and handled cat’s litter respectively. Miscarriages,
stillbirths, and premature births had been experienced by 128 (20.3%), 12 (1.9%) and 37 (5.9%)
Overall, of 630 serum samples tested, 270 (42.9%) were positive for T. gondii IgG, IgM or both.
Five (0.8%) samples were seropositive for IgM suggesting primary infection during pregnancy.
Forty eight (38.1%) of 126 clinic samples were positive for T. gondii immunoglobulins compared
with 222 (44.1%) of 504 cord blood samples but the difference was not statistically significant
(P>0.05). Between hospitals, of 237 serum samples tested from the Port of Spain hospital, 90
(38.0%) were seropositive for T. gondii infection compared with 180 (45.8%) of 373 samples
from the Mount Hope Women’s Hospital. The difference was however not statistically
significant (p=0.093). Seroprevalence of toxoplasmosis was statistically significantly higher
amongst East Indian women (51.2%) compared with other races (p=0.012), women with 3
children (54.8%) compared with those with fewer number of children (p=0.021) and women who
carried 3 children to term (58.4%) versus those who carried 1 child to term (38.9%), p=0.032.
The prevalence of toxoplasmosis was higher in mothers who experienced miscarriages (43.8%)
compared with those who did not (41.2%); mothers who experienced stillbirth (58.3%) versus
those who did not (41.6%); in women whose children were mentally retarded (50.0%) than those
who were not (40.4%) but the differences were not statistically significant (P>0.05). Similarly,
the seroprevalence of toxoplasmosis was higher in women with cats in their households (46.7%)
compared with those without cats (41.0%), those who handled cat’s litter (57.1%) compared with
those who never did so (44.0%), practised outdoor gardening (49.7%) compared with those who
did not (39.3%); consumed rare meat (66.7%) as against those who did not (42.1%) but the
differences were not statistically significant (P>0.05).
For phase II, a total of 504 cord blood samples of newborn babies was collected, 174 from a
women’s hospital and 330 from a general hospital. Of all cord blood samples tested, 220 (43.7%)
were seropositive for IgG while the prevalence of congenital toxoplasmosis as reflected by IgM
was 0.4%. The prevalence of IgG and IgM by health institutions was not significantly different
(P>0.05). The prevalence of toxoplasmosis using IgG was highest in neonates of mothers who
were of East Indian descent (54.1%), had four children (52.9%), kept cats in households (47.7%),
practised outdoor gardening (50.8%), consumed partially-cooked meat (66.7%), had experienced
miscarriage(s) (47.3%), stillbirths (66.7%), or had eye problem(s) (52.9%) and mental retardation
(50.0%). The differences from comparison groups were however not statistically significant
Of a total of 218 women studied in phase III, a majority was aged 21-30 years old (58.3%),
Africans (43.6%), single (33.5%), Christians (80.7%), educated up to secondary level (76.1%),
customer service employees (20.1%) and were pregnant with their first child (50.2%). Only 21
(9.6%) had any knowledge of toxoplasmosis and 22 (9.6%) had been screened for “TORCH”. A
total of 33 (15.1%) and 5 (2.3%) women had cats in their households and sometimes handled
cat’s litter respectively. Only 2 (0.9%) women were vegetarians, 36 (16.5%) practised outdoor
gardening and 4 (1.8%) worked on farms. Miscarriages, stillbirth, and premature births had been
experienced by 38 (17.4%), 4 (1.8%) and 10 (4.6%) women respectively. Of the samples tested so
far, 76 (34.9%) of 218, 36 (32.1%) of 112 and 19 (30.6%) of 62 pregnant women were positive
for T. gondii IgG immunoglobulin in the first, second and third trimesters respectively. The
prevalence of infection was highest in Success Laventille (43.9%) during the first trimester, in
Success Laventille (40.0%) during the second trimester and in Barataria (40.0%) during the third
semester. The difference was statistically significant (P<0.05; X2). Primary infection as detected
by T. gondii IgM immunoglobulin, was evident in 12 (5.5%) of 218, 12 (10.7%) of 112 and 2
(3.2%) of 62 women in the first, second and third trimesters respectively. During the first
trimester, the frequency of detection of T. gondii IgM immunoglobulin was highest in Upper
Laventille (14.3%), in St. Joseph and Upper Laventille (16.7%) in the second trimester and in St.
Joseph (22.2%) during the third trimester. The difference was not statistically significant (P>0.05;
Seroprevalence of toxoplasmosis during the first trimester was not statistically significantly
different amongst East Indian women (36.2%) and African women (35.8%) (P>0.05).
For the three trimesters, the seroprevalence of toxoplasmosis was not significantly different
(P>0.05) for women who had experienced miscarriages compared to those who had not; mothers
who experienced stillbirth versus those who did not and in women who had experience of
premature babies compared to those who did not. Similarly, there was no statistically significant
(P>0.05) difference in the seroprevalence of toxoplasmosis in women who have had children with
eye problems compared with those who had not and in women who had had children with
neurological problems compared to those who did not.
Athough the seroprevalence of T. gondii (IgG) was higher in women with cats in households
(48.5%) during the first trimester compared to those without (31.9%); in women who sometimes
handle cat’s litter (60.0%) compared to those without; that practice outdoor gardening (44.1%),
the difference was however not statistically significant (P>0.05). Similarly, working on the farm,
consumption of rare meat and being a vegetarian did not have a significant effect on the
prevalence of toxoplasmosis (P>0.05).
This study established for the first time in Trinidad, the occurrence of congenital toxoplasmosis.
It was concluded that the risk of primary infections in pregnant women by T. gondii in Trinidad
ranges from 3.8% (first trimester) to 10.1% (second trimester) and that pre-natal screening and
prophylactic treatment of women at risk are options that need to be considered. The study also
revealed a high seroprevalence of toxoplasmosis in neonates, coupled with serological evidence
of congenital disease, this being the first such report from the English-speaking Caribbean. It
indicates a need for sensitization of the population and health carcare workers and for follow-up
of infected children for clinical evidence of the disease. These actions would be necessary to fully
appreciate the impact of toxoplasmosis in Trinidad and Tobago.