What are the recommendations for preventing and managing in utero transmission of vectorborne diseases, such as malaria and Zika virus, in pregnant women?

Prevention and Management of In Utero Transmission of Vector-Borne Diseases

Pregnant women in areas with vector-borne disease transmission should use insect repellent on skin and clothing, wear protective clothing, and avoid outdoor activities during peak mosquito-feeding times to prevent in utero transmission of diseases like malaria, Zika, and West Nile virus. 1, 2

Prevention Strategies for Pregnant Women

• Apply EPA-approved insect repellent to exposed skin and clothing when in areas with vector-borne disease transmission 1
• Wear long-sleeved shirts, long pants, and closed shoes to minimize skin exposure to mosquito bites 1, 2
• Avoid outdoor activities during peak mosquito-feeding times, particularly dawn and dusk 1
• Use bed nets (preferably insecticide-treated) in endemic areas, especially for malaria prevention 3
• Screening of asymptomatic pregnant women for vector-borne diseases is not recommended due to lack of specific treatments and unclear consequences of infection 1, 2

Diagnostic Approach for Suspected Cases

• Test pregnant women with meningitis, encephalitis, acute flaccid paralysis, or unexplained fever in areas with ongoing vector-borne disease transmission for specific antibodies in serum and CSF 1, 2
• Report confirmed infections to local or state health departments for surveillance and follow-up of pregnancy outcomes 1
• For West Nile virus, serologic testing for virus-specific IgM and IgG antibodies in serum and/or CSF is the primary diagnostic method 2

Management of Confirmed Vector-Borne Disease During Pregnancy

Fetal Evaluation

• Perform detailed ultrasound examination of the fetus to evaluate for structural abnormalities 2-4 weeks after onset of vector-borne illness (e.g., WNV) 1
• Consider testing amniotic fluid, chorionic villi, or fetal serum for evidence of infection, though sensitivity and specificity of these tests may be limited 1
• In case of miscarriage or induced abortion, test all products of conception (placenta, umbilical cord) for evidence of infection to document effects on pregnancy outcome 1

Medication Considerations

• For malaria treatment during pregnancy, medication choice must be carefully considered:
  • Mefloquine has shown no increase in teratogenic effects or adverse pregnancy outcomes in multiple studies 4
  • Chloroquine requires individual benefit-risk assessment before prescribing to pregnant women 5
  • Antimalarial intermittent preventive therapy with sulfadoxine-pyrimethamine has been associated with decreased risk of neonatal mortality and lower birth weight 3

Evaluation of Infants Born to Infected Mothers

• Perform comprehensive clinical evaluation of infants born to mothers with confirmed vector-borne disease during pregnancy 1
• Test infant serum for antibodies to the specific pathogen 1, 2
• Consider further evaluation if clinical abnormalities are identified or laboratory testing indicates congenital infection 1
• For Zika virus specifically, evaluate for congenital abnormalities, microcephaly, and neurological complications 6

Special Considerations for Specific Vector-Borne Diseases

West Nile Virus

• One case has demonstrated intrauterine WNV transmission resulting in chorioretinitis and cerebral tissue damage, though causal relationship is not definitively proven 1
• No specific treatment exists for WNV infection; management is primarily supportive care 2

Zika Virus

• Maternal Zika infection has been strongly linked to neonatal malformations, microcephaly, and other congenital abnormalities 6
• Pregnant women should avoid travel to Zika-endemic areas when possible 7, 6

Malaria

• Malaria during pregnancy is associated with maternal anemia, low birth weight, preterm birth, and increased perinatal mortality 7, 3
• Insecticide-treated mosquito nets and appropriate antimalarial prophylaxis are critical preventive measures 3

Emerging Challenges

• Climate change is affecting the incidence and geographic spread of many vector-borne diseases, requiring clinicians to be vigilant even in previously non-endemic areas 7, 8
• Insecticide resistance poses a growing challenge to vector control programs, potentially limiting prevention options 9
• Development of new insecticides and vaccines for vector-borne diseases remains a critical need 8, 9