No Evidence of O'nyong-nyong Viremia among Children with Febrile Illness in Kenya (2015-2018)

Chikungunya virus antepartum transmission and abnormal infant outcomes in a cohort of pregnant women in Nigeria

OBJECTIVES

Chikungunya virus (CHIKV), a reemerging global public health concern, which causes acute febrile illness, rash, and arthralgia and may affect both mothers and infants during pregnancy. Mother-to-child transmission (MTCT) of CHIKV in Africa remains understudied.

METHODS

Our cohort study screened 1006 pregnant women with a Zika/dengue/CHIKV rapid test at two clinics in Nigeria between 2019 and 2022. Women who tested positive for the rapid test were followed through their pregnancy and their infants were observed for 6 months, with a subset tested by reverse transcription-polymerase chain reaction (RT-PCR) and neutralization, to investigate seropositivity rates and MTCT of CHIKV.

RESULTS

Of the 1006, 119 tested positive for CHIKV immunoglobulin (Ig)M, of which 36 underwent detailed laboratory tests. While none of the IgM reactive samples were RT-PCR positive, 14 symptomatic pregnant women were confirmed by CHIKV neutralization test. Twelve babies were followed with eight normal and four abnormal outcomes, including stillbirth, cleft lip/palate with microcephaly, preterm delivery, polydactyly with sepsis, and jaundice. CHIKV IgM testing identified three possible antepartum transmissions.

CONCLUSION

In Nigeria, we found significant CHIKV infection in pregnancy and possible CHIKV antepartum transmission associated with birth abnormalities.

Chikungunya virus antepartum transmission and abnormal infant outcomes in Nigeria

Chikungunya virus (CHIKV) has become a global public health concern since the reemergence of the Indian Ocean lineage and expansion of the Asian genotype. CHIKV infection causes acute febrile illness, rash, and arthralgia and during pregnancy may affect both mothers and infants. The mother-to-child transmission (MTCT) of CHIKV in Africa remains understudied. We screened 1006 pregnant women at two clinics in Nigeria between 2019 and 2022 and investigated the prevalence and MTCT of CHIKV. Of the 1006, 119 tested positive for CHIKV IgM, of which 36 underwent detailed laboratory tests. While none of the IgM reactive samples were RT-PCR positive, 14 symptomatic pregnant women were confirmed by CHIKV neutralization test. Twelve babies were followed with 8 normal and 4 abnormal outcomes, including stillbirth, cleft lip/palate with microcephaly, preterm delivery, polydactyly with sepsis and jaundice. CHIKV IgM testing identified 3 antepartum transmissions, further studies will determine its impact in antepartum infection.

Determinants of Chikungunya and O'nyong-Nyong Virus Specificity for Infection of Aedes and Anopheles Mosquito Vectors

Mosquito-borne diseases caused by viruses and parasites are responsible for more than 700 million infections each year. Anopheles and Aedes are the two major vectors for, respectively, malaria and arboviruses. Anopheles mosquitoes are the primary vector of just one known arbovirus, the alphavirus o'nyong-nyong virus (ONNV), which is closely related to the chikungunya virus (CHIKV), vectored by Aedes mosquitoes. However, Anopheles harbor a complex natural virome of RNA viruses, and a number of pathogenic arboviruses have been isolated from Anopheles mosquitoes in nature. CHIKV and ONNV are in the same antigenic group, the Semliki Forest virus complex, are difficult to distinguish via immunodiagnostic assay, and symptomatically cause essentially the same human disease. The major difference between the arboviruses appears to be their differential use of mosquito vectors. The mechanisms governing this vector specificity are poorly understood. Here, we summarize intrinsic and extrinsic factors that could be associated with vector specificity by these viruses. We highlight the complexity and multifactorial aspect of vectorial specificity of the two alphaviruses, and evaluate the level of risk of vector shift by ONNV or CHIKV.