Recurrence rate of vivax malaria in the Republic of Korea

Association between CYP2D6 phenotype and recurrence of Plasmodium vivax infection in south Korean patients

Background

Primaquine is activated by CYP2D6 in the hepatocytes. In Korea, primaquine is the only hypnozoitocidal agent used for patients with vivax malaria. Thus, patients with poor CYP2D6 activity could have an increased risk of primaquine failure and subsequent relapse. The study sought to identify the association between CYP2D6 phenotype and recurrence of malaria in Korean patients.

Methods

A total of 102 patients with vivax malaria were prospectively enrolled from eight institutions in Korea. An additional 38 blood samples from patients with recurred vivax malaria were provided by the Korea Disease Control and Prevention Agency. Malaria recurrence was defined as more than one episode of vivax malaria in the same or consecutive years. CYP2D6 star alleles, phenotypes, and activity scores were examined.

Results

Genotyping for CYP2D6 was successful in 101 of the prospectively enrolled patients and 38 samples from the Korea Disease Control and Prevention Agency, of which 91 were included in the no-recurrence group and 48 were included in the recurrence group. Reduced CYP2D6 activity (intermediate metabolizer) phenotype was more common in the recurrence group than in the no-recurrence group (OR, 2.33 (95% CI, 1.14–4.77); p = 0.02). Patients with lower CYP2D6 activity had a higher probability of recurrence (p = 0.029).

Conclusion

This study suggests that CYP2D6 polymorphism may affect primaquine efficacy and thus Plasmodium vivax recurrence in Korea.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04311-6.

An Epidemiological Analysis of 28 Vivax Malaria Cases in Gimpo-si, Korea, 2020

Since 1993, vivax malaria has been recognized as a public health burden in Korea. Despite of pan-governmental malaria-control efforts and the dramatic reduction in the burden of this disease over the last 10 years, vivax malaria has not been well controlled and has remained continuously endemic. We focused interviewed and examined the charts of 28 confirmed vivax malaria patients given malarial therapy for whom daily records were kept from Gimpo-si, Gyeonggi-do of Korea. Various epidemiological characteristics of vivax malaria, including the incubation period, medication used, and recurrence, and an evaluation of the parasitic characteristics from the focused interviews of patients from this region are described here. Most of the participants indicated the 3 most common symptoms of malaria (headache, chills and fever). Of the 28 cases, 2 experienced a second attack and there were 17 and 11 cases with short- and long-term incubation periods, respectively, yielding a short-term to long-term ratio of 1.5. Based on the parasitemia stages, most of the participants were tested at 5 to 7 days (11 cases) and 7 to 15 days (11 cases) after initial wave of asexual parasites. In conclusion, public health authorities should consider developing management measures to decrease the time lag for diagnosis and drafting unified and robust guidelines for drug use for malaria and drawing up unified and robust guidelines on the use of medication for malaria. It also suggests that routine monitoring, surveillance, and precise medical surveys in high-risk vivax malaria endemic areas are pivotal to controlling this persistent public disease and finally eliminating it from Korea.

The unique distribution of the Plasmodium vivax merozoite surface protein 1 in parasite isolates with short and long latent periods from the Republic of Korea

Background

Vivax malaria occurring in the Republic of Korea is occasionally characterized by a long latent infection induced by hypnozoites in the liver. So far, the mechanisms responsible for short and long latent infections of vivax malaria are not known. Therefore, the present study classified the parasite isolates according to the long and short latent periods and then analysed the genetic diversity of the Plasmodium vivax merozoite surface protein 1 (PvMSP-1).

Methods

Blood samples containing P. vivax isolates were collected from 465 patients from 2011 to 2013 at health centers in the Republic of Korea. PvMSP-1 gene sequences were analysed in groups classified by the collection year, and short or long latent periods. The samples in short and long latent periods were selected by the timing of vivax malaria occurrence, July–August and January–May, respectively.

Results

Three PvMSP-1 types (Sal-1, Belem, and recombinant) were observed in P. vivax isolates collected from 2011 to 2013. Interestingly, the recombinant and Sal-1 types were dominant in vivax malaria of the long and short latent periods, respectively. In addition, the S-b like subtype of the PvMSP-1 Sal-1 type was first identified in 2013.

Conclusion

This study revealed that the genetic type of PvMSP-1 is likely related to the duration of its latent period. Moreover, trends of the genetic types of PvMSP-1 seem to be stable in recent years compared with those of previous years in which various new types were observed.

Evaluation of the efficacy of chloroquine chemoprophylaxis for vivax malaria among Republic of Korea military personnel

Chloroquine has been used massively for vivax malaria prophylaxis and treatment in the Republic of Korea (ROK) military personnel from 1997. Although prophylaxis is generally regarded as successful among ROK military, prophylaxis failure has been repeatedly reported. Before the prophylaxis program was started on July 4th 2011, which was completed on October 16th 2011, by the ROK military, more than 60% of malaria cases were attributed to new infection or long-latency relapse. During the prophylaxis program, the authors re-examined the efficiency of chloroquine chemoprophylaxis in ROK military during the last 6 months of 2011 by measuring compliance and whole blood chloroquine levels in 41 malaria patients immediately before instituting antimalarial therapy between July and December. Three patients (7.3%) showed good compliance, and had whole blood total chloroquine levels above the minimally inhibitory concentration (100 ng/mL). However, 28 (69.3%) of these 41 patients when admitted to hospital showed poor or no compliance with prophylaxis; 4 of the 28 (14.3%) were stationed outside the mass prophylaxis region, and 5 (17.9%) subjects were infected after the prophylaxis program had finished. These findings indicate that the current malaria control program should be carefully reconsidered, in terms of, individual instruction, current chemoprophylaxis program regimens, and schedules to improve the efficacy of prophylaxis in the ROK military.

Quantifying effect of geographic location on epidemiology of Plasmodium vivax malaria

Recent autochthonous transmission of Plasmodium vivax malaria in previously malaria-free temperate regions has generated renewed interest in the epidemiology of this disease. Accurate estimates of the incubation period and time to relapse are required for effective malaria surveillance; however, this information is currently lacking. By using historical data from experimental human infections with diverse P. vivax strains, survival analysis models were used to obtain quantitative estimates of the incubation period and time to first relapse for P. vivax malaria in broad geographic regions. Results show that Eurasian strains from temperate regions have longer incubation periods, and Western Hemisphere strains from tropical and temperate regions have longer times to relapse compared with Eastern Hemisphere strains. The diversity in these estimates of key epidemiologic parameters for P. vivax supports the need for elucidating local epidemiology to inform clinical follow-up and to build an evidence base toward global elimination of malaria.

Recurrencias de malaria por Plasmodium vivax según el uso de primaquina: análisis de estudios descriptivos longitudinales

ANTECEDENTES: la primaquina (PQ) es el único medicamento disponible en el mercado para prevenir recurrencias del paludismo por Plasmodium vivax pero varios aspectos suyos se desconocen. OBJETIVO: comparar regímenes de PQ para prevenir recurrencias de malaria vivax. METODOLOGÍA: revisión sistemática de datos. RESULTADOS: 1. ¿Según los estudios descriptivos, la PQ es eficaz para prevenir las recurrencias del paludismo vivax? Sí. La comparación de estudios que no usaron PQ con otros que sí la aplicaron, en cualquier esquema, mostró que si no se usa PQ la recurrencia es altamente probable. 2. ¿Tienen la misma eficacia dosis diarias (mg/kg) iguales pero dosis totales diferentes? La dosis total de 75 mg es tanto o más eficaz que la de 210 mg. 3. ¿La eficacia anti-recurrencias depende del lugar donde sucede la infección? Si. Hay variación según país y región. 4. ¿La frecuencia de recurrencias depende del tiempo de seguimiento post tratamiento? La respuesta no es uniforme para todos los lugares. CONCLUSIONES: la PQ resultó eficaz para prevenir las recurrencias, pero no fue 100%. Las dosis totales de 210 y de 75 mg tuvieron igual eficacia, pero 75 mg sólo han sido evaluados en India, donde P. vivax parece ser más sensible a la PQ que en otros lugares. Parece indudable la influencia del lugar en la proporción de recurrencias, incluso con una misma dosis total. El papel del tiempo de seguimiento no resultó claro. Deben evaluarse esquemas alternativos al estándar, que tiene eficacia promedio de 90% o más.

Population structure and transmission dynamics of Plasmodium vivax in the Republic of Korea based on microsatellite DNA analysis

Background

In order to control malaria, it is important to understand the genetic structure of the parasites in each endemic area. Plasmodium vivax is widely distributed in the tropical to temperate regions of Asia and South America, but effective strategies for its elimination have yet to be designed. In South Korea, for example, indigenous vivax malaria was eliminated by the late 1970s, but re-emerged from 1993. We estimated the population structure and temporal dynamics of transmission of P. vivax in South Korea using microsatellite DNA markers.

Methodology/Principal Findings

We analyzed 255 South Korean P. vivax isolates collected from 1994 to 2008, based on 10 highly polymorphic microsatellite DNA loci of the P. vivax genome. Allelic data were obtained for the 87 isolates and their microsatellite haplotypes were determined based on a combination of allelic data of the loci. In total, 40 haplotypes were observed. There were two predominant haplotypes: H16 and H25. H16 was observed in 9 isolates (10%) from 1996 to 2005, and H25 in 27 (31%) from 1995 to 2003. These results suggested that the recombination rate of P. vivax in South Korea, a temperate country, was lower than in tropical areas where identical haplotypes were rarely seen in the following year. Next, we estimated the relationships among the 40 haplotypes by eBURST analysis. Two major groups were found: one composed of 36 isolates (41%) including H25; the other of 20 isolates (23%) including H16. Despite the low recombination rate, other new haplotypes that are genetically distinct from the 2 groups have also been observed since 1997 (H27).

Conclusions/Significance

These results suggested a continual introduction of P. vivax from other population sources, probably North Korea. Molecular epidemiology using microsatellite DNA of the P. vivax population is effective for assessing the population structure and transmission dynamics of the parasites - information that can assist in the elimination of vivax malaria in endemic areas.

Vivax malaria is widely prevalent, mainly in Asia and South America with 390 million reported cases in 2009. Worldwide, in the same year, 2.85 billion people were at risk. Plasmodium vivax is prevalent not only in tropical and subtropical areas but also in temperate areas where there are no mosquitoes in cold seasons. While most malaria researchers are focusing their studies on the parasite in tropical areas, we examined the characteristics of P. vivax in South Korea (temperate area) temporally, using 10 highly polymorphic microsatellite DNA (a short tandem repeat DNA sequence) in the parasite genome, and highlighted the differences between the tropical and temperate populations. We found that the South Korean P. vivax population had low genetic diversity and low recombination rates in comparison to tropical P. vivax populations that had been reported. We also found that some of the parasite clones in the population were changing from 1994 to 2008, evidence suggesting the continual introduction of the parasite from other populations, probably from North Korea. Polymorphic DNA markers of the P. vivax parasite are useful tools for estimating the situation of its transmission in endemic areas.