Differential transmissibility to Anopheles arabiensis of Plasmodium vivax gametocytes in patients with diverse Duffy blood group genotypes.

BACKGROUND: Measuring risk of malaria transmission is complex, especially in case of Plasmodium vivax. This may be overcome using membrane feeding assays in the field where P. vivax is endemic. However, mosquito-feeding assays are affected by a number of human, parasite and mosquito factors. Here, this study identified the contributions of Duffy blood group status of P. vivax-infected patients as a risk of parasite transmission to mosquitoes. METHODS: A membrane feeding assay was conducted on a total of 44 conveniently recruited P. vivax infected patients in Adama city and its surroundings in East Shewa Zone, Oromia region, Ethiopia from October, 2019 to January, 2021. The assay was performed in Adama City administration. Mosquito infection rates were determined by midgut dissections at seven to 8 days post-infection. Duffy genotyping was defined for each of the 44 P. vivax infected patients. RESULTS: The infection rate of Anopheles mosquitoes was 32.6% (296/907) with 77.3% proportion of infectious participants (34/44). Infectiousness of participants to Anopheles mosquitoes appeared to be higher among individuals with homozygous Duffy positive blood group (TCT/TCT) than heterozygous (TCT/CCT), but the difference was not statistically significant. The mean oocyst density was significantly higher among mosquitoes fed on blood of participants with FY*B/FY*BES than other genotypes (P = 0.001). CONCLUSION: Duffy antigen polymorphisms appears to contribute to transmissibility difference of P. vivax gametocytes to Anopheles mosquitoes, but further studies are required.

High prevalence of Pfcrt 76T and Pfmdr1 N86 genotypes in malaria infected patients attending health facilities in East Shewa zone, Oromia Regional State, Ethiopia.

BACKGROUND: Plasmodium falciparum resistance to series of anti-malarial drugs is a major challenge in efforts to control and/or eliminate malaria globally. In 1998, following the widespread of chloroquine (CQ) resistant P. falciparum, Ethiopia switched from CQ to sulfadoxine-pyrimethamine (SP) and subsequently in 2004 from SP to artemether-lumefantrine (AL) for the treatment of uncomplicated falciparum malaria. Data on the prevalence of CQ resistance markers after more than two decades of its removal is important to map the selection pressure behind the targets codons of interest. The present study was conducted to determine the prevalence of mutations in Pfcrt K76T and Pfmdr1 N86Y codons among malaria-infected patients from Adama, Olenchiti and Metehara sites of East Shewa zone, Oromia Regional State, Ethiopia. METHODS: Finger-prick whole blood samples were collected on 3MM Whatman ® filter papers from a total of 121 microscopically confirmed P. falciparum infected patients. Extraction of parasite DNA was done by Chelex-100 method from dried blood spot (DBS). Genomic DNA template was used to amplify Pfcrt K76T and Pfmdr1 N86Y codons by nested PCR. Nested PCR products were subjected to Artherobacter protophormiae-I (APoI) restriction enzyme digestion to determine mutations at codons 76 and 86 of Pfcrt and Pfmdr1 genes, respectively. RESULTS: Of 83 P. falciparum isolates successfully genotyped for Pfcrt K76T, 91.6% carried the mutant genotypes (76T). The prevalence of Pfcrt 76T was 95.7%, 92.5% and 84.5% in Adama, Metehara and Olenchiti, respectively. The prevalence of Pfcrt 76T mutations in three of the study sites showed no statistical significance difference (χ2 = 1.895; P = 0.388). On the other hand, of the 80 P. falciparum samples successfully amplified for Pfmdr1, all carried the wild-type genotypes (Pfmdr1 N86). CONCLUSION: Although CQ officially has been ceased for the treatment of falciparum malaria for more than two decades in Ethiopia, greater proportions of P. falciparum clinical isolates circulating in the study areas carry the mutant 76T genotypes indicating the presence of indirect CQ pressure in the country. However, the return of Pfmdr1 N86 wild-type allele may be favoured by the use of AL for the treatment of uncomplicated falciparum malaria.

Infectivity of Symptomatic Patients and Their Contribution for Infectiousness of Mosquitoes following a Membrane Feeding Assay in Ethiopia.

The membrane feeding assay is widely used to evaluate the efficacy of transmission-blocking interventions (TBIs) and identify the reservoir of malaria. This study aimed to determine the infectivity of blood meals from symptomatic Plasmodium-infected patients to an Anopheles arabiensis colony in Ethiopia. A membrane feeding assay was conducted on a total of 63 Plasmodium falciparum- and/or Plasmodium vivax-infected clinical patients in East Shoa Zone, Ethiopia. Detection of P. falciparum and P. vivax in blood samples was done using microscopy. Mosquito infection rates were determined by dissection of mosquitoes' midguts, while mosquito infectiousness was observed by dissection of their salivary glands. The proportion of infectious symptomatic patients was 68.3% (43/63). Using the chi-square or Fisher's exact test, the oocyst infection levels were higher among patients infected with P. vivax, females, and rural residents. Nearly 57% (56.7%, 17/30) of assays produced sporozoites in the salivary glands of mosquitoes. Both oocyst and sporozoite infection rates had positive correlations with parasitemia and gametocytemia. High infectiousness of symptomatic patients was observed, with a greater proportion of infectious mosquitoes per assay. Demonstrating oocyst infection in the mosquitoes might confirm estimates of the infectiousness of mosquitoes, although some of the oocyst-infected mosquitoes failed to produce sporozoites. IMPORTANCE Malaria remains one of the most devastating infectious diseases globally, and transmission-blocking activities are needed. Plasmodium transmission from human to mosquitoes is poorly studied, particularly in endemic countries, and the membrane feeding assay allows it to be determined. In this study, we demonstrated human infectious reservoirs of malaria. Moreover, the effect of Plasmodium-infected patients on the infectiousness of mosquitoes was also observed. These findings are therefore important for designing future evaluation of transmission-blocking interventions that will support the malaria elimination program.

Magnitude of urban malaria and its associated risk factors: the case of Batu town, Oromia Regional State, Ethiopia.

OBJECTIVE: This study aimed to assess the magnitude of malaria and its associated risk factors in urban, Batu town, Oromia Regional State, Ethiopia. METHODS: This health-facility based prospective cross-sectional study enrolled 356 febrile malaria patients to assess risk factors associated with malaria infection. RESULTS: An overall positivity rate of 17.13% (61/356) for malaria infection was observed. Among the malaria-positive patients, 50.8% (31/61) of them were positive for Plasmodium vivax, 45.90% (28/61) were positive for Plasmodium falciparum, and 3.3% (2/61) had mixed infections of P. falciparum and P. vivax. Logistic regression analysis revealed that individuals who possessed insecticide-treated net (Odds ratio [OR] = 0.38, 95% confidence interval [CI] [0.194, 0.743]) and whose houses were sprayed with insecticides (OR = 0.18, 95% CI [0.097, 0.34]) were significantly less likely to have a malaria infection. Individuals living closer to stagnant water had a significantly greater chance of malaria infection than those who lived a distance from stagnant water (OR = 0.34, 95% CI [0.19, 0.59]). CONCLUSION: The present study revealed that malaria remains a public health problem in the urban area of Batu town, which suggests that the same might be true for other urban areas in the country.

Retrospective analysis of urban malaria cases due to Plasmodium falciparum and Plasmodium vivax: the case of Batu town, Oromia, Ethiopia.

Malaria is a major health problem in the world particularly in sub-Saharan Africa where 90% of malaria deaths occur. Likewise malaria is one of the leading causes of morbidity and mortality in Ethiopia. It has been reported that about 75% of the country is malarious where 60% of its population is at risk of this infection. Like many African countries, Ethiopian urban settings are characterized by poor housing, lack of sanitation and drainage of surface water which provide conducive environment for the breeding of vector mosquitoes for the transmission of malaria. There are few researches on urban malaria under the urban settings of Ethiopia. The purpose of this study was to assess the magnitude of malaria cases due to Plasmodium falciparum and Plasmodium vivax in Batu town, Oromia, Ethiopia. Retrospective laboratory confirmed malaria case record data of six years (2012-2017) were used to analyze the magnitude of malaria cases due to P. falciparum and P. vivax, in Batu town, Oromia, Ethiopia. The retrospective data analysis revealed an overall 21,797 malaria confirmed cases; of which 49.5% were due to P. falciparum and 50.5% were due to P. vivax, with a slight decline in malaria between 2012 and 2017. Malaria cases were recorded in both sexes and all age groups in the study area. From the result of the present analysis it can be concluded that both P. falciparum and P. vivax were the cause for malaria cases indicating malaria is still public health problem in Batu town. Therefore, appropriate strategic control measures must be designed to protect the public and eventually eliminate malaria from the area and the country as a whole.