Imported malaria in Trinidad, West Indies: Detection of multiple non-endemic Plasmodium species

Human malaria, which is caused by five Plasmodium species, remains a significant global health concern, particularly in tropical regions. Though Trinidad was declared malaria-free in 1965, imported cases, primarily from Venezuela, continue to pose a threat due to the presence of competent Anopheles vectors and the introduction of clinical cases to a susceptible population. This study identified the Plasmodium spp. present in human cases in Trinidad from December 2018 to December 2023 using both microscopy and PCR targeting the cytochrome oxidase 1 gene of Plasmodium spp., followed by sequencing and phylogenetic analysis. Fifty-six (36.60%) of the 153 blood samples collected from suspected malaria cases were positive on both microscopic examination of blood smears and PCR. There was 100% concordance between the two methods used to detect malaria, but 98.21% agreement between the species identification by sequencing and microscopic evaluation of the blood smear. The study confirmed the continued importation of P. vivax, P. falciparum, and P. ovale into Trinidad. Plasmodium malariae was identified in three samples, two of which had no travel history outside Trinidad, indicating that it is likely linked to local transmission in Trinidad. The best fitting model in logistic regression indicated that the statistically significant risk factors associated with PCR positivity were symptoms of headache and nausea. These findings underscore the ongoing public health risk posed by malaria reintroduction in Trinidad due to cross-border population movement, reinforcing the need for sustained surveillance and rapid diagnostic capabilities.