A rapid malaria appraisal in the Venezuelan Amazon

Abstract

Background: While the federal state of Amazonas bears the highest risk for malaria in Venezuela (2007: 68.4 cases/1000 inhabitants), little comprehensive information about the malaria situation is available from this area. The purpose of this rapid malaria appraisal (RMA) was to provide baseline data about malaria and malaria control in Amazonas.

Methods: The RMA methodology corresponds to a rapid health impact assessment (HIA) as described in the 1999 Gothenburg consensus. In conjunction with the actors of the malaria surveillance system, all useful data and information, which were accessible within a limited time-frame of five visits to Amazonas, were collected, analysed and interpreted.

Results: Mortality from malaria is low (< 1 in 105) and slide positivity rates have stayed at the same level for the last two decades (15% +/- 6% (SD)). Active case detection accounts for ca. 40% of slides taken. The coverage of the censured population with malaria notification points (NPs) has been achieved in recent years. The main parasite is Plasmodium vivax (84% of cases). The proportion of Plasmodium falciparum is on the decline, possibly driven by the introduction of cost-free artemisinin-based combination therapy (ACT) (1988: 33.4%; 2007: 15.4%). Monitoring and documentation is complete, systematic and consistent, but poorly digitalized. Malaria transmission displayed a visible lag behind rainfall in the capital municipality of Atures, but not in the other municipalities. In comparison to reference microscopy, quality of field microscopy and rapid diagnostic tests (RDTs) is suboptimal (kappa < 0.75). Hot spots of malaria risk were seen in some indigenous ethnic groups. Conflicting strategies in respect of training of community health workers (CHW) and the introduction of new diagnostic tools (RDTs) were observed.

Conclusion: Malaria control is possible, even in tropical rain forest areas, if the health system is working adequately. Interventions have to be carefully designed and the features of the particular local Latin American context considered.

Figure 1

Malaria Mortality in Venezuela and Amazonas (1988-2007). Fatal malaria cases in Venezuela (bright red), fatal malaria cases in Amazonas (dark red).

Figure 2

Malaria Cases, Slides taken, Population in Amazonas (1988-2007). Malaria cases (red, right vertical axis), slides taken (blue, left vertical axist), population (grey, left vertical axis).

Figure 3

Annual Parasite Index and Slide Positivity Rate in Amazonas (1988 - 2007). Annual parasite index (grey, API), slide positivity rate (blue, SPR).

Figure 4

Slide Positivity Rate of P. falciparum and P. vivax in Amazonas (1988 - 2007). Slide positivity rate (SPR) of P. vivax (bright blue), slide positivity rate (SPR) of P. falciparum (dark blue).

Figure 5

P. vivax Slide Positivity Rate and Rainfall in Atures/Amazonas (1998 - 2007). Slide positivity rate P. vivax (blue, SPR), rainfall (green).

Figure 6

P. falc. Slide Positivity Rate and Rainfall in Atures/Amazonas (1998 - 2007). Slide positivity rate P. falciparum (blue, SPR), rainfall (green).

Figure 7

Malaria Infections by Age Groups in Amazonas (2007). Malaria cases of P. falciparum (dark red), P. vivax (bright red), P. malariae (purple), mixed infections (brown).

Figure 8

Annual Parasite Index (API) by Municipalities and by Ethnic Groups in Amazonas (2007). Left: Annual Parasite Index (API) by municipalities. Right: Annual Parasite Index (API) by ethnic groups. Schematic illustration of the settlement area of the ethnic groups of Guahibo (1), Puinave (2), Yanomami (3).

Figure 9

Active Case Detection in Amazonas (1988 - 2007). Slides taken by active case detection (blue, left vertical axis), cases detected by active case detection (red, right vertical axis).

Figure 10

Passive Case Detection in Amazonas (1988 - 2007). Slides taken by passive case detection (blue, left vertical axis), cases detected by passive case detection (red, right vertical axis).