Detection and genetic characterisation of Toxoplasma gondii circulating in free-range chickens, pigs and seropositive pregnant women in Benue state, Nigeria

Nzelu, Ifeoma; Kwaga, Jacob; Kabir, Junaidu; Lawal, Idris; Beazley, Christy; Evans, Laura; Blake, Damer

Abstract

Toxoplasma gondii parasites present strong but geographically varied signatures of population structure. Populations sampled from Europe and North America have commonly been defined by over-representation of a small number of clonal types, in contrast to greater diversity in South America. The occurrence and extent of genetic diversity in African T. gondii populations remains understudied, undermining assessments of risk and transmission. The present study was designed to establish the prevalence, genotype and phylogeny of T. gondii in meat samples collected from livestock produced for human consumption (free-range chickens, n=173; pigs, n=211), and in blood samples collected from pregnant women (n=91) in Benue state, Nigeria. The presence of T. gondii DNA was determined using a published nested polymerase chain reaction, targeting the 529 bp multicopy gene element. Samples with the highest parasite load (assessed using quantitative PCR) were selected for PCR-restriction fragment length polymorphism (PCR-RFLP) targeting the surface antigen 3 (SAG3), SAG2 (5’ and 3’), beta-tubulin (BTUB) and dense granule protein 6 (GRA6) loci, and the apicoplast genome (Apico). Toxoplasma gondii DNA was detected in all three of the populations sampled, presenting 30.6, 31.3 and 25.3% prevalence in free-range chickens, pigs and pregnant women, respectively. Quantitative-PCR indicated low parasitaemia in most positive samples, limiting some further molecular analyses. PCR-RFLP results suggested that T. gondii circulating in the sampled populations presented with a type II genetic background, although all included a hybrid type I/II or II/III haplotype. Concatenation of aligned RFLP amplicon sequences revealed limited diversity with nine haplotypes and little indication of host species-specific or spatially distributed sub-populations. Samples collected from humans shared haplotypes with free-range chickens and/or pigs. Africa remains under-explored for T. gondii genetic diversity and this study provides the first detailed definition of haplotypes circulating in human and animal populations in Nigeria.

Citation

Nzelu, I., Kwaga, J., Kabir, J., Lawal, I., Beazley, C., Evans, L., & Blake, D. (2021). Detection and genetic characterisation of Toxoplasma gondii circulating in free-range chickens, pigs and seropositive pregnant women in Benue state, Nigeria. PLoS Neglected Tropical Diseases, https://doi.org/10.1371/journal.pntd.0009458

• Journal Article Type: Article
• Acceptance Date: May 10, 2021
• Publication Date: Jun 2, 2021
• Deposit Date: Oct 24, 2022
• Publicly Available Date: Oct 24, 2022
• Print ISSN: 1935-2727
• Publisher: Public Library of Science
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.1371/journal.pntd.0009458