# Artemisinin-Resistant Plasmodium falciparum K13 Mutant Alleles, Thailand–Myanmar Border

Mikaël Boullé, Benoit Witkowski, Valentine Duru, Kanlaya Sriprawat, Shalini Nair, Marina Mcdew-White, Tim J.C. Anderson, Aung Pyae Phyo, Didier Ménard, François Nosten

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► To cite this version:

Mikaël Boullé, Benoit Witkowski, Valentine Duru, Kanlaya Sriprawat, Shalini Nair, et al.  
Artemisinin-Resistant Plasmodium falciparum K13 Mutant Alleles, Thailand–Myanmar Border.  
Emerging Infectious Diseases, 2016, 22 (8), pp.1503-1505. 10.3201/eid2208.160004 . hal-02560612

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latter being more aggressive. In the Greater Metropolitan Area and Costa Rica in general, free-ranging dogs are common, including at playgrounds and school yards, sites also vulnerable to nocturnal visits by raccoons. Dogs can have patent *B. procyonis* parasite infections and can play a role in transmission of the parasite from raccoons to humans.

In Costa Rica, cases of larva migrans have been reported. The Unidad de Investigación y Análisis, Registros y Estadísticas de Salud at the National Children's Hospital, San José, Costa Rica, reported 135 cases of larva migrans ocularis and 21 cases of visceral larva migrans caused by nonspecifically identified ascarids during 2005–2014 (unpub. data). However, these diagnoses were based on IgG serologic testing results (Martinez J., National Children's Hospital; pers. comm., 2015), which do not identify ascarid species. Western blot testing would improve accuracy (10).

The eco-epidemiology of *B. procyonis* parasites in tropical settings is relevant to public health because it might play a yet-unrecognized role in larva migrans pathology, which can be severe. Increased contact between raccoons and humans also warrants further investigation to improve understanding and minimize zoonotic risk.

This work was funded by a grant from the Fondo Institucional de Desarrollo Académico-2013-Universidad Nacional-Universidad de Costa Rica, Fondo del Sistema-Consejo Nacional de Rectores (ACUERDO-VI-167-2013).

The study was approved by Research Ethics Board permits (FCSA-EMV-CBA-007-2013); the Universidad Nacional de Costa Rica, Universidad de Costa Rica Institutional Committee for the Use and Care of Laboratory Animals (CICUA-130-13), and the Institutional Review Board of MINAE (ACCVC-OH-512).

## References

1. Kazacos KR. *Baylisascaris procyonis* and related species. In: Samuel WM, Pybus MJ, Kocan AA, editors. Parasitic diseases of wild mammals. 2nd ed. Ames (IA): Iowa State University Press; 2001. p.301-41.

2. Hernandez SM, Galbreath B, Riddle DF, Moore AP, Palamar MB, Levy MG, et al. *Baylisascaris procyonis* in raccoons (*Procyon lotor*) from North Carolina and current status of the parasite in the USA. Parasitol Res. 2013;112:693-8. http://dx.doi.org/10.1007/s00436-012-3186-1

3. Roussere GP, Murray WJ, Raudenbush CB, Kutilek MJ, Levee DJ, Kazacos KR. Raccoon roundworm eggs near homes and risk for larva migrans disease, California communities. Emerg Infect Dis. 2003;9:1516-22. http://dx.doi.org/10.3201/eid0912.030039

4. Soto M. Raccoons causing problems inside the Greater Metropolitan Area [in Spanish] [cited 2015 Jul 11]. http://wfnode01.nacion.com/2010-09-05/AldeaGlobal/NotasSecundarias/AldeaGlobal2507351.aspx

5. Tokiwa T, Nakamura S, Taira K, Une Y. *Baylisascaris potosis* n. sp., a new ascarid nematode isolated from captive kinkajou, *Potos flavus*, from the Cooperative Republic of Guyana. Parasitol Int. 2014;63:591-6. http://dx.doi.org/10.1016/j.parint.2014.03.003

6. Overstreet RM. *Baylisascaris procyonis* (Stefanski and Zarnowski, 1951) from the kinkajou, *Potos flavus*, in Colombia. J Parasitol. 1970;37:192-5.

7. Anderson RC, Chabaud AG, Willmott S. Keys to the nematode parasites of vertebrates: archival volume. Wallingford (UK): CAB International; 2009. p. 463.

8. Franssen F, Xie K, Sprong H, van der Giessen J. Molecular analysis of *Baylisascaris columnaris* revealed mitochondrial and nuclear polymorphisms. Parasit Vectors. 2013;6:124. http://dx.doi.org/10.1186/1756-3305-6-124

9. Paquet-Durand I, Hernández J, Dolz G, Zuñiga JJ, Schnieder T, Epe C. Prevalence of *Toxocara* spp., *Toxascaris leonina* and ancylostomidae in public parks and beaches in different climate zones of Costa Rica. Acta Trop. 2007;104:30-7. http://dx.doi.org/10.1016/j.actatropica.2007.06.011

10. Dangoudoubiyam S, Kazacos KR. Differentiation of larva migrans caused by *Baylisascaris procyonis* and *Toxocara* species by Western blotting. Clin Vaccine Immunol. 2009;16:1563-8. http://dx.doi.org/10.1128/CVI.00251-09

Address for correspondence: Mario Baldi, Institute of Wildlife Ecology, University of Veterinary Medicine; Savoyenstrasse 1, A-1160, Vienna, Austria; email: baldim@medvetuni.ac.at or mario.baldi.salas@una.cr

# Artemisinin-Resistant *Plasmodium falciparum* K13 Mutant Alleles, Thailand–Myanmar Border

Mikael Boullé,<fnref n="1" /> Benoit Witkowski,<fnref n="1" />
Valentine Duru, Kanlaya Sriprawat,
Shalini K. Nair, Marina McDew-White,
Tim J.C. Anderson, Aung Pyae Phyo,
Didier Menard, François Nosten

Author affiliations: Mahidol University Faculty of Tropical Medicine, Mae Sot, Thailand (M. BoulléSriprawat K, A.P. Phyo, F. Nosten); Institut Pasteur in Cambodia, Phnom Penh, Cambodia (B. Witkowski, V. Duru, D. Menard); Texas Biomedical Research Institute, San Antonio, Texas, USA (S.K. Nair, M. McDew-White; T.J.C. Anderson; F. Nosten); University of Oxford Nuffield Department of Medicine, Oxford, UK (F. Nosten)

DOI: http://dx.doi.org/10.3201/eid2208.160004

**To the Editor:** Artemisinin resistance (ART-R) in *Plasmodium falciparum* phenotypes may have evolved independently in various areas of the Greater Mekong Subregion (1,2), prompting the World Health Organization to change its regional policy from containment to elimination (3). Risks associated with ART-R include compromised use of artemisinin combined therapy, partner drug resistance selection, total ART-R resistance, and geographic extension

<footnote n="1">¹These authors contributed equally to this article.</footnote>
to other malaria-endemic regions (2,3). Characterization of ART-R in each setting and rapid update of listed phenotypes classified as in vitro resistant to this antimalarial drug are needed.

Detected in western Cambodia in 2008, ART-R has been observed in neighboring countries, notably at the Thailand–Myanmar border (4,5). Resistance is partial and manifests by an increased parasite clearance half-life (PCHL) of >5 hours in patients receiving artemisinin monotherapy or artemisinin combined therapy (6). In vitro, ART-R phenotype has been characterized by the ring-stage survival assay (RSA<sup>0–3h</sup>, cutoff 1%) (7) and mutations in the propeller domain of a *kelch* gene on chromosome 13 (K13) (8,9). However, tremendous K13 variability in different genetic backgrounds requires confirmation of specific alleles as ART-R markers (2,3); even statistically significant clinical associations are rarely unequivocal (5–9).

On the Thailand–Myanmar border where ART-R has been documented (4), we investigated K13 mutations in clinical and in vitro phenotypes. Patients with nonsevere *P. falciparum* hyperparasitemia infections treated during 2011–2013 at the Shoklo Malaria Research Unit (Mae Sot, Thailand) were treated with artesunate, then combined artesunate/mefloquine (5). We retrospectively selected 33 case-patients on the basis of PCHL outcome to analyze a broad parasite clearance distribution with available cryopreserved isolates. Full written consent from all patients was obtained. PCHL was calculated on the basis of initial and repeated parasitemia measurement every 6 hours until undetectable asexual parasitemia (6) was achieved. Venous blood samples were cryopreserved before drug administration (day 0).

Short-term, culture-adapted parasites (3% hemato-crit; RPMI-1640 supplemented with 10% human serum, 0.05 mg/mL hypoxanthine, 2 mg/mL sodium bicarbonate, 2 mg/mL glucose, 0.04 mg/mL gentamicin, 0.3 mg/mL L-glutamine in a 37°C candle-jar atmosphere) were split for blinded RSA<sup>0–3h</sup> and K13 genotyping. We performed RSA<sup>0–3h</sup> in duplicate by selecting early rings (0–3 h) in a combination of percoll gradient and sorbitol lysis, followed by a 6-h exposure to 700 nmol/L dihydroartemisinin (7). RSA survival rate was measured microscopically 66 hours after drug removal and calculated as the quotient of parasitemia upon DHA exposure over control parasitemia with dimethyl sulfoxide. Only 25 isolates that were successfully culture-adapted provided RSA survival rates.

After the phenotypical assays, the genotypes were obtained and K13 regions were amplified by using 3 primer sets: fragment 1 (1725380–1725680 bp, pos 211–302), F-tgaaaatatggtaggtgatt and R-atcgtttcctatgttcttct; fragment 2 (1725980–1726520 bp, pos 419–570), F-atc-tagggtattcaaaagg, R-ccaaaagattttaagtgaaag; and fragment 3 (1726400–1726940 bp, pos 545–707), F-ctgccattcatttgtatct,

R-ggatatgatggctcttcta) before sequencing (8). The 33 monoclonal isolates yielded clear K13 gene sequences. All except 4 isolates from patients who had PCHL >5 h had a single K13 mutant allele (19/23), and all isolates except 1 (G538V) from case-patients who had PCHL <5 h carried the K13 3D7 wild-type allele (9/10). PCHL was significantly different between K13 wild-type (n = 13, median 4.3 h) and mutant (n = 20, median = 7.2 h) alleles (p<0.01 by Mann-Whitney U test). Among the 25 isolates successfully tested, RSA survival rates differed significantly between K13 wild-type (n = 10, median 0.5%) and mutant (n = 15, median 3.5%) alleles (p<0.001 by Mann-Whitney U test). When PCHL was present <5 h, RSA survival rates (n = 7, median 0.5%) were significantly lower than when PCHL was >5 hours (n = 18, median 3.1%) (p = 0.001 by Mann-Whitney U test).

In detail (Figure), C580Y and N458Y mutants were consistently associated with PHCL >5h and RSA values >1%. The C580Y allele has been repeatedly confirmed as a molecular marker of ART-R (5,7–9). Previous reports have inconsistently associated the N458Y mutation with ART-R; 7 case-patients with PCHL >5 h were reported by Ashley et al. (5), and 1 artemisinin sensitive case was reported at the China–Myanmar border (10). Nevertheless, this mutation has not been confirmed in vitro (3). We confirmed the mutation in vitro, and in vivo, according to the World Health Organization definition (3), this K13 allele as a molecular marker of ART-R.

Conflicting data observed between PCHL and RSA values for 4 mutant alleles (E252Q, P441L, G538V, and

<figure><img src="image_3.png" /></figure>

**Figure.** Distribution of parasite clearance half-lives (n = 33, squares) and Ring-stage survival assay survival rates (n = 25, circles) of *Plasmodium falciparum* isolates from patients on the Thailand–Myanmar border, determined on the basis of each K13 genotype. Mean survival rate of duplicate measures are showed for each isolate. Dashed line represents the cutoff value for parasite clearance half-life (artemisinin resistance >5 h) and RSA survival (artemisinin resistance >1%). K13 alleles N458Y and C580Y were consistently associated with parasite clearance half-life and survival rates above threshold. Bold text indicates K13 alleles with variable parasite clearance half-life and RSA associations. Horizontal bars represent median values for each K13 genotype. Survival rate for laboratory reference 3D7 strain was 0.2%.
A675V) require further targeted approaches to relate them to previous reports. In a study in which only PCHL were reported (5), the proportion of slowly clearing infections were 69%, 0%, 30%, and 61% for the P441L, E252Q, G538V, and A675V alleles, respectively. Discrepancies can result from confounding pharmacologic (drug level, partner drug), immunologic, and parasitologic (genetic background, parasitic stage at treatment initiation) factors.

RSA results and K13 genotypes were associated with delayed parasite clearance, emphasizing the pertinence of each method to define ART-R. In this area, N458Y is a marker of ART-R. To solve conflicts about specific mutations, more detailed characterization in vitro and in vivo is needed.

### Acknowledgments

We thank all the patients and their parents or guardians.

The Shoklo Malaria Research Unit is part of the Mahidol-Oxford University Research Unit, funded by the Wellcome Trust of Great Britain. Laboratory work at Texas Biomedical Research Institute was conducted in facilities constructed with support from Research Facilities Improvement Program grant C06 RR013556 and R017515 from the National Center for Research Resources of the National Institutes of Health and was funded by National Institute of Allergy and Infectious Diseases Grant R37A1048071. This work was supported by grants from the Réseau International des Insituts Pasteur ACIP grant #A14-2012.

M.B., B.W., F.N., and D.M. contributed to the study design. M.B., B.W., and V.D. performed the in vitro assays. T.A., S.N., M.M.-W., and K.S. performed the genetic polymorphism analyses. A.P.P. and F.N. coordinated and supervised the clinical studies. M.B., B.W., F.N. and D.M. analyzed the data and wrote the first draft of the manuscript. All authors contributed to the writing of the manuscript.

### References

1. Takala-Harrison S, Jacob CG, Arze C, Cummings MP, Silva JC, Dondorp AM, et al. Independent emergence of artemisinin resistance mutations among *Plasmodium falciparum* in Southeast Asia. J Infect Dis. 2015;211:670–9. http://dx.doi.org/10.1093/infdis/jiu491

2. Fairhurst RM. Understanding artemisinin-resistant malaria: what a difference a year makes. Curr Opin Infect Dis. 2015;28:417–25. http://dx.doi.org/10.1097/QCO.0000000000000199

3. World Health Organization. Status report on artemisinin and ACT resistance—September 2015 [cited 2015 Dec 12]. http://www.who.int/malaria/publications/atoz/status-rep-artemisinin-resistance-sept2015.pdf

4. Phyo AP, Nkhoma S, Stepniewska K, Ashley EA, Nair S, McGready R, et al. Emergence of artemisinin-resistant malaria on the western border of Thailand: a longitudinal study. Lancet. 2012; 379:1960–6. http://dx.doi.org/10.1016/S0140-6736(12)60484-X

5. Ashley EA, Dhorda M, Fairhurst RM, Amaratunga C, Lim P, Suon S, et al. Spread of artemisinin resistance in *Plasmodium falciparum* malaria. N Engl J Med. 2014;371:411–23. http://dx.doi.org/10.1056/NEJMoa1314981

6. White LJ, Flegg JA, Phyo AP, Wiladpai-ngern JH, Bethell D, Plowe C, et al. Defining the *in vivo* phenotype of artemisinin-resistant falciparum malaria: a modelling approach. PLoS Med. 2015;12. http://dx.doi.org/10.1371/journal.pmed.1001823

7. Witkowski B, Amaratunga C, Khim N, Sreng S, Chim P, Kim S, et al. Novel phenotypic assays for the detection of artemisinin-resistant *Plasmodium falciparum* malaria in Cambodia: in-vitro and ex-vivo drug-response studies. Lancet Infect Dis. 2013;13:1043–9. http://dx.doi.org/10.1016/S1473-3099(13)70252-4

8. Aricie F, Witkowski B, Amaratunga C, Beghain J, Langlois AC, Khim N, et al. A molecular marker of artemisinin-resistant *Plasmodium falciparum* malaria. Nature. 2013;505:50–5. http://dx.doi.org/10.1038/nature12876

9. Straimer J, Gnadig NF, Witkowski B, Amaratunga C, Duru V, Ramadani AP, et al. Drug resistance. K13-propeller mutations confer artemisinin resistance in *Plasmodium falciparum* clinical isolates. Science. 2015;347:428–31. http://dx.doi.org/10.1126/science.1260867

10. Wang Z, Wang Y, Cabrera M, Zhang Y, Gupta B, Wu Y, et al. Artemisinin resistance at the China-Myanmar border and association with mutations in the K13 propeller gene. Antimicrob Agents Chemother. 2015;6952–9. http://dx.doi.org/10.1128/AAC.01255-15

Address for correspondence: Didier Ménard, Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, 5 Boulevard Monivong, PO Box 983, Phnom Penh, Cambodia; email: dmenard@pasteur-kh.org

# Meningococcal Group W Disease in Infants and Potential Prevention by Vaccination

Sydel R. Parikh, Helen Campbell, Kazim Beebeejaun, Sonia Ribeiro, Steve J. Gray, Ray Borrow, Mary E. Ramsay, Shamez N. Ladhani

Author affiliations: Public Health England, London, UK (S.R. Parikh, H. Campbell, K. Beebeejaun, S. Ribeiro, S.J. Gray, R. Borrow, M.E. Ramsay, S.N. Ladhani); St. George's University of London, London (S.N. Ladhani)

DOI: http://dx.doi.org/10.3201/eid2208.160128

**To the Editor:** We recently reported that postvaccination serum samples from infants immunized with a novel, protein-based multicomponent meningococcal serogroup B (MenB) vaccine (Bexsero; GlaxoSmithKline Vaccines, Veringa, Italy) have bactericidal activity against the hypervirulent meningococcal group W (MenW) strain belonging to the sequence type (ST) 11 clonal complex (I). Historically, MenW has been a rare cause of invasive meningococcal disease (IMD), accounting for <5% of confirmed cases in England and Wales (2). Since 2009, MenW cases caused by