RESUMO
BACKGROUND: The indigenous population is considered a highly susceptible group to malaria because individuals usually live in areas with high exposure to Anopheles and poverty, and have limited access to health services. There is a great diversity of indigenous communities in Colombia living in malaria-endemic areas; however, the burden of infection in these populations has not been studied extensively. This study aimed to determine the prevalence of Plasmodium infections in indigenous and non-indigenous communities in two malaria-endemic areas in Colombia. METHODS: A community-based cross-sectional survey was conducted in seven villages of Turbo and El Bagre municipalities; three of these villages were indigenous communities. Inhabitants of all ages willing to participate were included. Sociodemographic and clinical data were recorded as well as household information. The parasitological diagnosis was performed by microscopy and nested PCR. The prevalence of microscopy and submicroscopic infection was estimated. An adjusted GEE model was used to explore risk factors associated with the infection. RESULTS: Among 713 participants, 60.7% were from indigenous communities. Plasmodium spp. was detected in 30 subjects (4.2%, CI 95% 2.9-5.9); from those, 29 were in the indigenous population, 47% of infections were afebrile, and most of them submicroscopic (10/14). Microscopic and submicroscopic prevalence was 2.5% (CI 95% 1.6-3.9) and 1.7% (CI 95% 0.9-2.9), respectively. In El Bagre, all infections occurred in indigenous participants (3.9%, CI 95% 2.2-7.1), and 81% were submicroscopic. By contrast, in Turbo, the highest prevalence occurred in indigenous people (11.5%; CI 95%: 7.3-17.5), but 88.8% were microscopic. Living in an indigenous population increased the prevalence of infection compared with a non-indigenous population (PR 19.4; CI 95% 2.3-166.7). CONCLUSION: There is a high proportion of Plasmodium infection in indigenous communities. A substantial proportion of asymptomatic and submicroscopic carriers were detected. The identification of these infections, not only in indigenous but also in the non-indigenous population, as well as their associated factors, could help to implement specific malaria strategies for each context.
Assuntos
Indígenas Sul-Americanos/estatística & dados numéricos , Malária/epidemiologia , Colômbia/epidemiologia , Estudos Transversais , Humanos , Malária/parasitologia , Microscopia , Reação em Cadeia da Polimerase , Prevalência , Fatores de RiscoRESUMO
Submicroscopic Plasmodium infections in pregnancy are common in endemic areas, and it is important to understand the impact of these low-level infections. Asymptomatic, chronic infections are advantageous for parasite persistence, particularly in areas where the optimal eco-epidemiological conditions for parasite transmission fluctuate. In chronic infections, the persistence of the antigenic stimulus changes the expression of immune mediators and promotes constant immune regulation, including increases in regulatory T cell populations. These alterations of the immune system could compromise the response to routine vaccination. This study aimed to evaluate the effect of submicroscopic plasmodial infection with P. falciparum and P. vivax during pregnancy on the immune response to the tetanus toxoid vaccine in Colombian women. Expression of different cytokines and mediators of immune regulation and levels of anti-tetanus toxoid (TT) immunoglobulin (Ig)G were quantified in pregnant women with and without submicroscopic plasmodial infection. The anti-TT IgG levels were significantly lower in the infected group compared with the uninfected group. The expression of interferon (IFN)-γ, tumour necrosis factor (TNF) and forkhead box protein 3 (FoxP3) was significantly higher in the infected group, while the expression of cytotoxic T lymphocyte antigen 4 (CTLA-4) and transforming growth factor (TGF)-ß was lower in the group of infected. In conclusion, submicroscopic Plasmodium infection altered the development of the immune response to the TT vaccine in Colombian pregnant women. The impact of Plasmodium infections on the immune regulatory pathways warrants further exploration.