Maternity Care Calendar and Guidelines: Preventing Congenital Toxoplasmosis

Literature Search:

Medline was searched using the MeSH toxoplasmosis/diagnosis, prevention & control and mass screening, limited to English and human from 1993-2003 and updated by searching with MeSH exp TOXOPLASMOSIS/ or toxoplasmosis.mp AND pregnancy.mp. or exp PREGNANCY/ from 1995-2005, limited to English and human. Clinical practice guidelines and review articles were selected. EBM reviews including the Cochrane Database of Systematic Reviews (CDSR), ACP Journal Club, Database of Abstracts and Reviews of Effectiveness (DARE) and Cochrane Central Register of Controlled Trials (CCTR) were searched using the keywords toxoplasmosis and pregnancy. The Canadian Task Force on Preventive Health Care, the US Preventive Services Task Force and the US National Guideline Clearinghouse were also reviewed for guidelines on toxoplasmosis and pregnancy.

Summary of Evidence:

Background
About one-third of adult women in the United States and Canada have antibodies to the parasite, Toxoplasma gondii, the remainder may be at risk for a primary maternal infection during pregnancy.[1, 2] In immunocompetent adults, the infection is usually asymptomatic. Vertical transmission rates range from 15% in the first trimester to 60% in the third trimester.[2, 3] Congenital infection can result in spontaneous abortions, stillbirths or severe neurological effects such as chorioretinitis, intracranial calcifications, hydrocephalus, mental retardation, and sensorineural hearing loss. Severe fetal effects are more likely if infection is acquired during the first or second trimester.[1-3]

Women infected with toxoplasmosis prior to conception rarely transmit the parasite to their fetus, but women with a reactivation due to immunosuppression or acute infection can transmit the infection to their fetus. [4]

Serologic studies in the US and the UK show that between 1 in 10, 000 and 10 in 10, 000 infants are infected at birth. [5-7] Between 400-4000 cases of congenital toxoplasmosis occur in the United States each year. [4]

Infection usually occurs from ingesting raw or undercooked meat (lamb, pork or beef). [4, 5]Infection can also result from ingesting oocytes on poorly washed raw vegetables, or in unpasteurized goat's milk and cheese. [2, 6, 8, 9] Exposure to cat feces in soil when gardening or through contact with cat litter can also result in infection. [4] It is worthwhile noting that it takes 2-3 days at room temperature for toxoplasmosis oocytes to form spores and become infectious. Therefore, if cat litter is changed daily, the risk of transmission is much lower.[2, 6] Owning a cat has not been consistently shown to be a risk factor for toxoplasmosis infection. In particular, indoor cats that do not hunt and are not fed raw meat are not likely to carry toxoplasmosis. [4] [4]Travel outside Europe and North America has been associated with toxoplasmosis infection. [5]An outbreak spread through the water supply occurred in Victoria, British Columbia in 1994/5.[2]

A Canadian, randomized controlled trial showed that pregnant women who received a 10-minute educational program about reducing the risk of toxoplasmosis infection had better pet and food hygiene behavior than controls.[10]

Screening for toxoplasmosis by serology is problematic. IgM antibody can remain positive for up to 2 years after infection, making it difficult to determine the implications of a positive test during pregnancy.[2, 3, 6, 11] Also, in areas where the prevalence rate is low (as in Canada and the US), the positive predictive value of the test is low (18-37%), resulting in a high rate of false-positive results. This could in turn lead to an unacceptably high rate of invasive follow-up tests such as amniocentesis or cordocentesis associated with significant morbidity. A significant rise in IgG titres taken 2-4 weeks apart or very high titres most often indicates a recent or current infection.[1, 3]

Severe congenital toxoplasmosis can be detected on ultrasound (IUGR, intracranial calcifications, ventriculomegaly, microcephaly, ascites, hepatosplenomegaly). [3] After 20 weeks, fetal blood samples for toxoplasmosis IgM is the most sensitive test, although both false positives and negatives can occur. [3] Detection of the toxoplasma parasite in fetal blood or amniotic fluid can be used to diagnose congenital toxoplasmosis.[1]

Treating infected mothers with agents such as Spiramycin appears to decrease the rate of vertical transmission by approximately 50-60%, but will not prevent neurological sequelae if congenital infection occurs. [1-3, 6, 7, 12] Treatment of known fetal or congenital infection requires a combination of agents. [1, 3]

Recommendations of Others:

Canadian Task Force on Preventive Health Care (CTFPHC):

The most recent review on toxoplasmosis by the CTFPHE was completed more than 20 years ago, in 1979. The report stated that there was good evidence for exposure history and serologic testing for non-immune pregnant women who keep a cat at home or eat raw meat. Counselling on hygiene for high risk groups is recommended. The intervention was recommended for the first prenatal visit and every 3 months thereafter as well as at the time of delivery. (Grade A Recommendation)[13]

U.S. Preventive Services Task Force (USPSTF):

The USPSTF has not completed a review on preventing congenital toxoplasmosis.

Recommendations from the Centers for Disease Control and Prevention: were outlined in a 2000 report.[6] They recommend that health care providers educate pregnant women at the first prenatal visit about food hygiene and exposure to cat feces. In particular, caregivers should counsel patients about the following measures:

While they recommend that health care providers be educated about the limitations of serologic testing for toxoplasmosis, they do not make specific recommendations about when serologic testing should be considered.

A patient information booklet can be found at
http://www.cdc.gov/ncidod/dbmd/gbs/pregnancyinfections.pdf

American College of Obstetricians and Gynecologists (ACOG) reviews the issue of toxoplasmosis in pregnancy in the publication "Guidelines for Perinatal Care".[1] The report states that routine screening of pregnant women is not indicated, except in the presence of HIV infection. The appropriate time to test for immunity is before conception. Confirmation of fetal infection is available in some centres by culture of fetal blood or amniotic fluid. Routine newborn screening and treatment of infected neonates may decrease the frequency of long-term sequelae. However, routine neonatal screening for toxoplasmosis is not currently recommended in the United States. [1]

In the ACOG Practice Bulletin on "Perinatal Viral and Parasitic Infections", the authors note that toxoplasmosis serology would be most effective at preventing congenital infections in regions where the prevalence is high. Routine prenatal screening is done in some European countries including France and Austria.[3] Serology is not currently recommended in the US and Canada except in women who are HIV positive and possibly for cat owners.

Society of Obstetricians and Gynaecologists of Canada (SOGC)
The SOGC has not produced a clinical practice guideline on preventing congenital toxoplasmosis but addresses the issue briefly in the Healthy Beginnings document.[14] They recommend education about avoiding exposure at the preconception or first prenatal visit. Screening may be appropriate for women at risk (having a new or outside cat or eating raw meat), with repeat testing at 16-20 weeks. Converters can be referred for culturing of fetal blood sample and treatment or termination as appropriate. They note that a potential health benefit to routine preconception screening exists due to the high prevalence and seriousness of congenital infection. If antibodies are present the woman can be reassured about immunity and if absent reminded about the importance of taking measures to avoid exposure. No references on toxoplasmosis are provided in the report.

In a 1998 Motherisk bulletin the following recommendations are given:[2]

Routine prenatal screening is not recommended in most Canadian Centres. If a pregnant women is screened, the first test should be done as early in the first trimester as possible. Negative tests does not preclude infection later in pregnancy and a positive test could represent infection that occurred before conception or be a false-positive.

Newborn screening for toxoplasmosis is also currently not routine in Canada, but could prove to be cost effective. The incidence of congenital toxoplasmosis (1:1000 -1:10,000) is similar to other diseases routinely screen for in newborns such as PKU (1:5000) and hypothyroidism (1:12,000) and treatment of newborns to prevent neurological sequelae looks promising.

The recommendations from Motherisk for primary prevention are very similar to those of the CDC and other authors.[5, 12] Motherisk adds the recommendation to avoid unpasteurized milk products.[2]

Institute for Clinical Systems Improvement: recently released a set of guidelines for prenatal care.[15] They state that "universal screening is not recommended because of the low prevalence of the disease during pregnancy, the uncertain and costly screening and the possible teratogenicity of treatment. It is recommended that efforts be directed at education of patients in prevention of this disease, which is now more commonly acquired in pregnancy through the handling of contaminated meat than from cat litter boxes."

The American Academy of Family Physicians has a patient handout on toxoplasmosis in pregnancy at http://familydoctor.org/handouts/180.html. (It is also available in Spanish)

The government of British Columbia has also produced an information sheet: http://www.bchealthguide.org/healthfiles/hfile43.pdf

Conclusions:

Routine serologic testing for toxoplasmosis in the preconception period is not currently recommended. Women should be counselled before pregnancy about avoiding raw meat and unpasteurized dairy products, washing fruits and vegetables well and avoiding contact with cat litter or soil that may contain feces.

The new guideline on the MCC will be as follows:
Reviewer:
Colleen Kirkham, MD, CCFP, FCFP January 2003
Updated March 2005

3/30/2005 10:34:00 PM

1. Guidelines for Perinatal Care. fifth ed. 2002: American Academy of Pediatrics, The American College of Obstetricians and Gynecologists.
2. Phillips, E., Motherisk Update: Toxoplasmosis. Can Fam Physician, 1998. 44: p. 1823-5.
3. ACOG Practice Bulletin: Perinatal viral and parasitic infections. 2000.
4. Jones, J., A. Lopez, and M. Wilson, Congenital toxoplasmosis. American Family Physician., 2003. 67(10): p. 2131-8.
5. Cook, A.J., et al., Sources of toxoplasma infection in pregnant women: European multicentre case-control study. European Research Network on Congenital Toxoplasmosis. BMJ, 2000. 321(7254): p. 142-7.
6. Centers for Disease Control. CDC recommendations regarding selected conditions affecting women's health. MMWR, 2000. 49(No. RR-2): p. 57-76.
7. Montoya, J.G. and O. Liesenfeld, Toxoplasmosis.[see comment]. Lancet, 2004. 363(9425): p. 1965-76.
8. Skinner, L.J., et al., Simultaneous diagnosis of toxoplasmosis in goats and goatowner's family. Scand J Infect Dis, 1990. 22(3): p. 359-61.
9. Hill, D. and J.P. Dubey, Toxoplasma gondii: transmission, diagnosis and prevention. Clin Microbiol Infect, 2002. 8(10): p. 634-40.
10. Carter, A.O., et al., The effectiveness of a prenatal education programme for the prevention of congenital toxoplasmosis. Epidemiol Infect, 1989. 103(3): p. 539-45.
11. Gras, L., et al., Duration of the IgM response in women acquiring Toxoplasma gondii during pregnancy: implications for clinical practice and cross-sectional incidence studies. Epidemiology & Infection, 2004. 132(3): p. 541-8.
12. Smith, J.L., Foodborne infections during pregnancy. Journal of Food Protection., 1999. 62(7): p. 818-29.
13. Canadian Task Force on the Periodic Health Examination. Canadian Guide to Clinical Preventive Health Care. 1994, Health Canada: Ottawa. p. 982.
14. SOGC Clinical Practice Guidelines. No 71. Healthy Beginnings: guidelines for care during pregnancy and childbirth. 1998.
15. Institute for Clinical Systems Improvement. Knowledge Resources. Routine prenatal care.Eighth ed July 2004. Accessed on line March 25, 2005 at http://www.icsi.org/knowledge/detail.asp?catID=29&itemID=191.