Julio Padilla

High prevalence of sub-microscopic infections in Colombia

BackgroundMalaria transmission in Latin America is typically characterized as hypo-endemic and unstable with ~170 million inhabitants at risk of malaria infection. Although Colombia has witnessed an important decrease in malaria transmission, the disease remains a public health problem with an estimated ~10 million people currently living in areas with malaria risk and ~61,000 cases reported in 2012. This study aimed to establish the malaria prevalence in three endemic regions of Colombia to aid in designing new interventions for malaria elimination.MethodsA cross-sectional survey was conducted in three regions of Colombia with different malaria epidemiological profiles: Tierralta (Ta), Tumaco (Tu) and Buenaventura (Bv). The Annual Parasite Index (API) was 10.7, 6.9 and 3.1, respectively. Participants were asked to respond to a sociodemographic questionnaire and then were bled to determine the Duffy genotype and the prevalence of malaria infection by microscopy and quantitative real-time PCR (qPCR).ResultsThe study was conducted between October 2011 and January 2012. Eight sentinel sites with 1,169 subjects from 267 households were included. The overall prevalence of sub-microscopic infections measured by thick blood smear (TBS) was 0.3% (n = 4) whereas by qPCR it was 9.7% (n = 113), with a greater proportion (13%) in 40-50 years old individuals. Furthermore, different regions displayed different prevalence of sub-microscopic infections: Bv 12%, Ta 15%, and Tu 4%. From these 113 samples (qPCR), 74% were positive for P. vivax and 22% for P. falciparum, and 4% were mixed infections, which correlates to the overall parasite prevalence in Colombia. This study showed that in the southern Pacific coast of Colombia (Bv and Tu), around 56% of the population have a Duffy-negative genotype, compared to the northern region (Ta) where the percentage of Duffy-negative genotype is around 3%.ConclusionsSub-microscopic infections are prevalent across different regions in Colombia, particularly in areas with relatively low transmission intensity. The poor microscopy results suggest the need for more sensitive diagnostic tools for detection of sub-microscopic infections. This study underscores the importance of conducting active case surveillance to more accurately determine malaria incidence, and highlights the need for updating the malaria guidelines to track and treat sub-microscopic malaria infections.

Malaria in gold-mining areas in Colombia

Gold-mining may play an important role in the maintenance of malaria worldwide. Gold-mining, mostly illegal, has significantly expanded in Colombia during the last decade in areas with limited health care and disease prevention. We report a descriptive study that was carried out to determine the malaria prevalence in gold-mining areas of Colombia, using data from the public health surveillance system (National Health Institute) during the period 2010-2013. Gold-mining was more prevalent in the departments of Antioquia, Córdoba, Bolívar, Chocó, Nariño, Cauca, and Valle, which contributed 89.3% (270,753 cases) of the national malaria incidence from 2010-2013 and 31.6% of malaria cases were from mining areas. Mining regions, such as El Bagre, Zaragoza, and Segovia, in Antioquia, Puerto Libertador and Montelíbano, in Córdoba, and Buenaventura, in Valle del Cauca, were the most endemic areas. The annual parasite index (API) correlated with gold production (R2 0.82, p < 0.0001); for every 100 kg of gold produced, the API increased by 0.54 cases per 1,000 inhabitants. Lack of malaria control activities, together with high migration and proliferation of mosquito breeding sites, contribute to malaria in gold-mining regions. Specific control activities must be introduced to control this significant source of malaria in Colombia.

Guía de Atención Clínica de Malaria

A pesar de los esfuerzos realizados, la malaria–o paludismo– es todavia uno de los mas gravesproblemas de salud publica mundial (1). Enlas Americas, se estima que 14 % de la poblacionse encuentra en riesgo de enfermar y morir pormalaria, y existe transmision endemica de paludismoen 21 paises de la region. En promedio,en la region se registran anualmente cerca deun millon de casos. La contribucion de la cargaglobal de los casos de malaria es de 3 %; lacontribucion global de los casos de Plasmodiumfalciparum es de 1 % y se estima que la mortalidadproducida por esta enfermedad es de 1%. Los desplazamientos de poblacion asociadosa fenomenos de colonizacion y diversas formasde uso de la tierra en las areas endemicas, laexplotacion de minas de oro y bosques, los conflictosarmados y los cultivos ilicitos, han provocadoepidemias aisladas

Characterizing the malaria rural-to-urban transmission interface: The importance of reactive case detection

Background Reported urban malaria cases are increasing in Latin America, however, evidence of such trend remains insufficient. Here, we propose an integrated approach that allows characterizing malaria transmission at the rural-to-urban interface by combining epidemiological, entomological, and parasite genotyping methods. Methods/Principal findings A descriptive study that combines active (ACD), passive (PCD), and reactive (RCD) case detection was performed in urban and peri-urban neighborhoods of Quibdó, Colombia. Heads of households were interviewed and epidemiological surveys were conducted to assess malaria prevalence and identify potential risk factors. Sixteen primary cases, eight by ACD and eight by PCD were recruited for RCD. Using the RCD strategy, prevalence of 1% by microscopy (6/604) and 9% by quantitative polymerase chain reaction (qPCR) (52/604) were found. A total of 73 houses and 289 volunteers were screened leading to 41 secondary cases, all of them in peri-urban settings (14% prevalence). Most secondary cases were genetically distinct from primary cases indicating that there were independent occurrences. Plasmodium vivax was the predominant species (76.3%, 71/93), most of them being asymptomatic (46/71). Urban and peri-urban neighborhoods had significant sociodemographic differences. Twenty-four potential breeding sites were identified, all in peri-urban areas. The predominant vectors for 1,305 adults were Anopheles nuneztovari (56,2%) and An. Darlingi (42,5%). One An. nuneztovari specimen was confirmed naturally infected with P. falciparum by ELISA. Conclusions This study found no evidence supporting the existence of urban malaria transmission in Quibdó. RCD strategy was more efficient for identifying malaria cases than ACD alone in areas where malaria transmission is variable and unstable. Incorporating parasite genotyping allows discovering hidden patterns of malaria transmission that cannot be detected otherwise. We propose to use the term “focal case” for those primary cases that lead to discovery of secondary but genetically unrelated malaria cases indicating undetected malaria transmission.

Estimation of the underreporting of malaria measurement in ten municipalities of the Pacific coast of Nariño during 2009

INTRODUCTION The complete and effective collection of data of malaria cases is essential to formulate operative plans, as well as to develop and apply policies for its prevention and control. However, in Colombia, not all of the identified cases are notified nor incorporated into the surveillance system. This underreport represents a serious problem for decision makers. OBJECTIVE To estimate the type and quantity of errors made during the completion of the malaria individual case reporting form and its digitization level, through the use and monitoring of the reporting form in ten municipalities of Nariño in 2009. MATERIALS AND METHODS A descriptive cross-sectional study with a non-probabilistic and convenience sample of diagnosis and treatment sites was carried out. Copies of the reporting forms from these sites and of the Public Health Surveillance System database were taken to compare them case-by-case. Proportions were calculated. RESULTS In more than 60% of the 2,816 reporting forms of positive cases the information about municipality of residence, municipality of origin and occupation was not reported. The case-by-case comparison revealed that 845 (30.0%) notification forms were not digitized at all. Information of variables such as residence, name of the municipality, and date of onset of symptoms were neither complete nor exact in more than 50% of the cases. CONCLUSIONS The use of copies of the reporting forms allows knowing the underreporting due to lack of digitization. One third of the cases can be recovered.

Malaria mortality in Colombia, 1979-2008

INTRODUCTION In Colombia, malaria represents a serious public health problem. It is estimated that approximately 60% of the population is at risk of the disease. OBJECTIVE To describe the mortality trends for malaria in Colombia, from 1979 to 2008. MATERIALS AND METHODS A descriptive study to determine the trends of the malaria mortality was carried out. The information sources used were databases of registered deaths and population projections from 1979 to 2008 of the National Statistics Department. The indicator used was the mortality rate. The trend was analyzed by join point regression. RESULTS Six thousands nine hundred and sixty five deaths caused by malaria were certified for an age-adjusted rate of 0.74 deaths/100.000 inhabitants for the study period. In 74.3% of the deaths, the parasite species was not mentioned. The trend in the mortality rate showed a statistically significant decreasing behavior, which was lower from the second half of the nineties as compared with that presented in the eighties. CONCLUSIONS The magnitude of mortality by malaria in Colombia is not high, in spite of the evident underreporting. A marked downward trend was observed between 1979 and 2008. The information obtained from death certificates, along with that of the public health surveillance system will allow to modify the recommendations and improve the implementation of preventive and control measures to further reduce the mortality caused by malaria.

Urban malaria transmission in a non-endemic area in the Andean region of Colombia

BACKGROUND Rapid urbanisation in difficult socio-economic conditions such as inadequate housing infrastructure, lack of public services, improper sanitation, and poor water drainage systems in vegetation-rich areas lead to ecological conditions that are conducive to the breeding of mosquitoes and transmission of malaria, in semi-urban and urban settings. OBJECTIVES This study aimed to describe the cases of malaria that were reported in the peri-urban areas of Pereira (Colombia), between 2008 and 2015. METHODS A retrospective study was conducted using data from the Malaria Surveillance System 2009-2015 and an outbreak study (between December 2008 and March 2009). Frequency distributions and summary measures, as well as univariate analysis were performed for all the variables in consideration. The annual parasite index (API) was calculated. FINDINGS Data on 214 cases were obtained from the surveillance system. A majority of the cases were reported in men (63.1%), followed by in children < 15 years (23.8%), and were caused predominantly by Plasmodium vivax (86.0%), with most of the infection occurring in the urban areas (52.8%) of Pereira. The API, by sex and age group, was higher among men ≥ 80 years. The outbreak study reported 14 cases of malaria in rural/peri-urban neighborhoods, and it was observed that the anopheline breeding sites were in close proximity to the houses in these areas. This population did not use protective measures against mosquitoes and chemical control was conducted through residual and spatial insecticide spraying. MAIN CONCLUSIONS This study suggested the presence of autochthonous malaria transmission, in Pereira, between 2008 and 2015, most of which were cases of P. vivax. A greater intensity was observed between 2008 and 2009 when malaria was possibly reintroduced to the region. During the years of the study, a gradual decrease in the number of reported cases of malaria was observed in Pereira, except for the time period between 2008 and 2009 when a spike was noted (estimated using the API); this was most likely caused by an outbreak. Interventions that are more aggressive in nature are required to prevent further malarial transmission and dissemination.