Molecular evidence of high rates of asymptomatic P. vivax infection and very low P. falciparum malaria in Botswana.
Botswana is one of eight SADC countries targeting malaria elimination by 2018. Through spirited upscaling of control activities and passive surveillance, significant reductions in case incidence of Plasmodium falciparum (0.96 - 0.01) was achieved between 2008 and 2012. As part of the elimination campaign, active detection of asymptomatic Plasmodium species by a highly sensitive method was deemed necessary. This study was carried out to determine asymptomatic Plasmodium species carriage by nested PCR in the country, in 2012.



A cross-sectional study involving 3924 apparently healthy participants were screened for Plasmodium species in 14 districts (5 endemic: Okavango, Ngami, Tutume, Boteti and Bobirwa; and 9 epidemic: North East, Francistown, Serowe-Palapye, Ghanzi, Kweneng West, Kweneng East, Kgatleng, South East, and Good Hope). Venous blood was taken from each participant for a nested PCR detection of Plasmodium species.



The parasite rates of asymptomatic Plasmodium species detected were as follows: Plasmodium falciparum, 0.16 %; Plasmodium vivax, 4.66 %; Plasmodium malariae, (Pm) 0.16 %; Plasmodium ovale, 0 %, mixed infections (P. falciparum and P. vivax), 0.055 %; and (P. vivax and P. malariae), 0.027 %, (total: 5.062 %). The high proportion of asymptomatic reservoir of P. vivax was clustered in the East, South Eastern and Central districts of the country. There appeared to be a correlation between the occurrence of P. malariae infection with P. vivax infection, with the former only occurring in districts that had substantial P. vivax circulation. The median age among 2-12 year olds for P. vivax infection was 5 years (Mean 5.13 years, interquartile range 3-7 years). The odds of being infected with P. vivax decreased by 7 % for each year increase in age (OR 0.93, 95 % CI 0.87-1.00, p = 0.056).



We have confirmed low parasite rate of asymptomatic Plasmodium species in Botswana, with the exception of P.vivax which was unexpectedly high. This has implication for the elimination campaign so a follow up study is warranted to inform decisions on new strategies that take this evidence into account in the elimination campaign.
Ministry of Health, Gaborone, Botswana.|Biological Sciences Department, University of Botswana, Gaborone, Botswana.
Thato
T
Motshoge
University of Ghana School of Allied Health and Biomedical Sciences, Accra, Ghana.
Grace K
GK
Ababio
Department of Pathology, University of Namibia School of Medicine, Windhoek, Namibia.
Larysa
L
Aleksenko
School of Medicine, University of Botswana, Gaborone, Botswana.
John
J
Read
Biological Sciences Department, University of Botswana, Gaborone, Botswana.
Elias
E
Peloewetse
School of Medicine, University of Botswana, Gaborone, Botswana.
Mazhani
M
Loeto
Ministry of Health, National Malaria Control Program, Gaborone, Botswana.
Tjantilili
T
Mosweunyane
World Health Organization, Botswana Country Office, Gaborone, Botswana.
Kentse
K
Moakofhi
Ministry of Health, National Malaria Control Program, Gaborone, Botswana.
Davies S
DS
Ntebele
Ministry of Health, National Malaria Control Program, Gaborone, Botswana.
Simon
S
Chihanga
Ministry of Health, National Malaria Control Program, Gaborone, Botswana.
Mpho
M
Motlaleng
Ministry of Health, National Malaria Control Program, Gaborone, Botswana.
Anderson
A
Chinorumba
Ministry of Health, National Malaria Control Program, Gaborone, Botswana.
Moses
M
Vurayai
Division of Infectious Disease, Department of Pediatrics, McMaster University, Hamilton, ON, Canada.
Jeffrey M
JM
Pernica
University of Botswana-University of Pennsylvania Partnership, Gaborone, Botswana.|Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
Giacomo M
GM
Paganotti
University of Namibia School of Medicine, Windhoek, PBAG13301, Namibia. dr.quaye@gmail.com.
Isaac K
IK
Quaye
D058345:Asymptomatic Infections / Q000453:epidemiology; D001902:Botswana / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D016054:DNA, Protozoan / Q000302:isolation & purification / Q000378:metabolism; D004912:Erythrocytes / Q000469:parasitology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008288:Malaria / Q000453:epidemiology* / Q000469:parasitology; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000469:parasitology; D016780:Malaria, Vivax / Q000453:epidemiology / Q000469:parasitology; D008297:Male; D016017:Odds Ratio; D010963:Plasmodium falciparum / Q000235:genetics* / Q000302:isolation & purification; D010965:Plasmodium malariae / Q000235:genetics / Q000302:isolation & purification; D041122:Plasmodium ovale / Q000235:genetics / Q000302:isolation & purification; D010966:Plasmodium vivax / Q000235:genetics* / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D015995:Prevalence; D012337:RNA, Ribosomal, 18S / Q000302:isolation & purification / Q000378:metabolism
D016054:DNA, Protozoan; D012337:RNA, Ribosomal, 18S
Asymptomatic Plasmodium vivax; Botswana
PLoS Negl Trop Dis. 2012;6(9):e1814
22970336
Malar J. 2013 Dec 20;12:458
24359262
Nat Commun. 2014;5:3346
24557500
Proc Natl Acad Sci U S A. 2013 May 14;110(20):8123-8
23637341
PLoS One. 2014 Aug 01;9(8):e103262
25084090
Malar J. 2015 Sep 22;14:360
26390924
Am J Trop Med Hyg. 2001 Jan-Feb;64(1-2 Suppl):97-106
11425182
Malar J. 2015 Feb 19;14:84
25884875
Proc Natl Acad Sci U S A. 2010 Mar 30;107(13):5967-71
20231434
Malar J. 2010 Sep 07;9:254
20822506
N Engl J Med. 1976 Aug 5;295(6):302-4
778616
Lancet. 2013 Sep 7;382(9895):900-11
23594387
Malar J. 2015 Aug 05;14:295
26242747
Malar J. 2011 Oct 11;10:297
21989376
Clin Microbiol Rev. 1992 Jan;5(1):26-35
1735093
Nat Commun. 2011;2:266
21468018
Malar J. 2012 Aug 22;11:294
22913727
PLoS One. 2009 Dec 22;4(12):e8410
20027314
Malar J. 2010 Jul 22;9:213
20649972
PLoS One. 2013;8(2):e57294
23437363
Am J Trop Med Hyg. 1982 Nov;31(6):1291-3
6816080
Am J Trop Med Hyg. 2005 Jul;73(1):214-21
16014862
J Natl Malar Soc. 1949 Dec;8(4):247-66, illust
15396796
Malar J. 2012 Jan 31;11:29
22289302
Nat Commun. 2012;3:1237
23212366
PLoS Negl Trop Dis. 2015 Nov 20;9(11):e0004222
26587988
Nature. 2015 Oct 8;526(7572):207-11
26375008
BMC Infect Dis. 2015 Aug 05;15:310
26242405
Parasit Vectors. 2016 Feb 24;9:99
26911433
Am J Trop Med Hyg. 2006 Oct;75(4):575-81
17038676
PLoS Med. 2011 Jan 25;8(1):e1000396
21311583
PLoS Negl Trop Dis. 2011 Jun;5(6):e1192
21713024
Mol Biochem Parasitol. 1993 Oct;61(2):315-20
8264734
PLoS Negl Trop Dis. 2015 Mar 17;9(3):e0003595
25780913
Malar J. 2014 Jan 06;13:8
24393454