The factors associated with malaria in children refer to the need for proper care of this population group. The differences observed between indigenous people and other races indicate that the disease differentially affects this ethnic group.
The association between malaria in children and the female sex is an enigma, because one would not expect a sex difference, nor a different association of other races and that which is already known in adults, whose predominance is the male sex14. No other studies were identified that found an association between malaria and female sex in indigenous children.
The fact of finding a stronger association of malaria in the lower age group is an indicator of the severity of the problem in this population. It is known that children under one year of age have an immature immune system, which makes them more vulnerable to infectious agents15. Because malaria is affecting children so early, there is a risk that the sequelae of the disease will also affect this population more strongly, in addition to the risk of the multiple malarial diseases accumulated throughout life, since the first experiences occurs at an early age. From the clinical and child development point of view, malaria has a combination of biological determinants, such as immunity, as well cultural ones in the form of housing, coexistence in society, as well as the socio-political aspect, in relation to access to health services. These elements must contribute to malaria in indigenous areas presenting differentiated epidemiological behavior16.
Malaria is widely distributed in other races among children aged 10 to 14 years, and may be related to intra-and peridomicile transmission, if we take into account housing conditions and the proximity of forest areas, vector density and basic sanitation17. In addition, the responsibility of helping parents with household income often results in a situation where the child is exposed to proximity to the vector, and can thus contribute to infection.
Indigenous people have a specific health policy, so primary care in the National Health Service (SUS) should adapt its actions aimed at these peoples by considering their organizational models in order to favor health promotion and malaria prevention18. Some characteristics, such as the high mobility of indigenous people, the difficulty of access to their regions by health teams and the persistent incursion of gold miners hinder malaria control actions in these regions contributes to the change in the epidemiological profile of the disease19.
Passive case surveillance is prevalent for cases of infection in indigenous children under 5 years of age. This results from the care that mothers take in taking their children to health care facilities as soon as the first symptoms appear. Differently, in other races, the prevalence of active case surveillance demonstrates the efficiency of investments and efforts established to ensure the increase in the network of malaria laboratories throughout the Amazonas state, with an increase of 72% in 10 years20. However, even with the incentive for the development of rapid tests in Brazil, especially in regions away from large centers, in indigenous regions only passive case surveillance occurs in most cases21. Moreover, the indigenous areas of Brazil have a health care system marked by a lack of professionals and consequent difficulties in the access of their populations to these services.
One of the most used techniques for laboratory diagnosis of malaria is the thick blood smear that seeks the specific confirmation of the disease. This technique is important because it allows the visualization of parasites, species identification and stages of development and quantification, which is essential data for clinical evaluation22. The thick blood smear is a sensitive method capable of detecting 0.001% parasitemia. However, the method becomes less sensitive when the individual is infected with more than one species of plasmodium, 29% of infections diagnosed by thick blood smear as being that of Plasmodium vivax, when analyzed by PCR, were identified as mixed infections23. On the SIVEP-Malaria system, parasitemias were quantified by plus system scale, presented in crosses to facilitate presentation and explanation. In this format, indigenous people have greater parasitic load than other races, which demonstrates that, because they live in places more vulnerable to mosquito breeding sites, they can be more parasitized due to the abundance of bites, or their immune system is not as competent in containing the multiplication of parasites after infection24.
As for the Plasmodium species present, P. vivax was evidenced as an infectious agent prevalent in other races, similar to another study23. This trend can be explained by factors such as its wide geographical distribution, since P. vivax establishes itself under higher temperature conditions25, and is characterized by more comprehensive and sometimes insidious symptoms such as fever, headache and chills. It is worrying that the cases of P. falciparum and mixed malaria (P. f. and P. v.) are predominant in indigenous people, since it represents more severity in these cases. On the other hand, as the symptoms are more exacerbated, this may contribute to the rapid search for diagnosis, since passive case surveillance was significant among indigenous people. In addition, indigenous people under 15 years of age have diverse forms of infection, with the prevalence of P. falciparum plus P. vivax and P. vivax plus P. falciparum gametocytes, even if the greater occurrence of cases in the Amazonas state is caused by P. vivax, thus demonstrating an extremely worrying situation, for presenting resistance to usual drugs and barrier prophylaxis such as the mosquito net, in the case of P. vivax16.
The timeliness of treatment of malaria among indigenous people in less than 48 hours meets the recommendations of the Brazilian Ministry of Health, and is an important factor for the control of the disease, since the earlier the treatment, the lower the possibility of spread, by reducing the source of infection. It is also an indicator of the level of care provided, because in the context studied, indigenous children had both diagnosis and treatment earlier when compared to the other races. It may be that those responsible take care of the children promptly, as soon as the first symptoms appear, and seek the health service where the diagnosis and treatment are performed. It is also possible that it is related to organization of the health service in indigenous areas, in which access is facilitated and usually the person who does the thick blood smear examination is a professional living in the area or even an indigenous professional, which generates proximity and ease of access2.
The data presented by the SIVEP-Malaria system, like any secondary data, have potential biases, which are out of the researchers’ control, such as the lack of standardization in data collection, which affects the quality of the records, the coverage that can vary in time and space and the lack of information, as in the case of the variable race and parasitemia, both showing a high degree of lack of data. In the first case, it was demonstrated that the classification method used in this work, including the indigenous village as a place of probable infection contributed to the increase in race data completeness; though in the second case, the lack of information about parasitemia was used in the analysis, and the lack of quantitative parasitemia data limited the interpretation of the parasitic burden. For parasitic missing data, a possibility would be both high and low parasitic load, since both make counting difficult and require greater skill of the microscopist, which may be a fragility in indigenous areas. Although these limitations have not compromised the interpretations of this study, additional analyses are necessary in order to unravel both the epidemiological situation of malaria involving indigenous people and the functioning of the program as a working process in the control of the malaria endemic.