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Background <p><i>Plasmodium malariae</i> is capable of persisting asymptomatically for decades, yet its long-latency mechanisms and epidemiological characteristics remain poorly understood. Since 2014, there have been reports of several long - latency cases of <i>P. malariae</i> in Guangdong Province over the years. This article, for the first time, analyzes the characteristics of these cases using multidimensional epidemiological, clinical, and genetic data, aiming to provide a reference for improving malaria prevention and control measures.</p> Methods <p>A retrospective analysis of long-latency <i>P. malariae</i> cases in Guangdong Province (2014–2022) was conducted. Clinical data were obtained from medical records, and epidemiological and epidemic spot investigation data were collected. Genetic analysis of the <i>P. malariae</i> circumsporozoite protein gene was performed to trace infection origins.</p> Results <p>Seven cases of long - latency <i>P. malariae</i> infection were identified, with a notable female predominance (85.7%) and a mean age of 75.3 years. The cases were distributed across seven counties in six municipalities, showing a dispersed spatiotemporal distribution. Most cases (85.7%, 6/7) had a history of residing in Guangdong’s historical endemic regions (pre-1990s). Comprehensive case investigation suggests that the infection sources were either historical local transmission (6 cases) or Southeast Asian importation (1 case), with latency periods ranging from 7 to 50 years. Phylogenetic analysis indicated that the long-latency cases clustered within the Asian lineage, with nucleotide homology of 95% − 97%, which was distinct from the strains in Africa (homology: 92% − 95%). Clinical manifestations were non - specific, including fever, and some cases presented with an increase in the percentage of neutrophils and a decrease in albumin levels. Diagnostic delays (median: 4 days) highlighted challenges in identifying infections.</p> Conclusions <p>This study demonstrated that <i>P. malariae</i> can cause prolonged asymptomatic infections with latency periods extending up to 50 years and underscores the importance of enhanced malaria surveillance, particularly among older populations with unexplained fever in historically endemic areas. Future research should focus on understanding the mechanisms of long - term host - parasite interactions and improving diagnostic and preventive strategies.</p> Clinical trial number <p>not applicable.</p>

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Unraveling the origins and features of long-latency Plasmodium malariae infections: a comprehensive epidemiological, clinical, and genetic study of seven cases in Guangdong Province (2014–2022)

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月24日

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  • Jia-Yi Zhang,
  • Qiang Mao,
  • De Wu,
  • Zhuo-Hui Deng,
  • Jun Liu,
  • Yu-Huang Liao,
  • Wen-Cheng Lu,
  • Guan-Ting Zhang,
  • Xian-Chang Zhang,
  • Jing-Diao Chen

摘要

Background

Plasmodium malariae is capable of persisting asymptomatically for decades, yet its long-latency mechanisms and epidemiological characteristics remain poorly understood. Since 2014, there have been reports of several long - latency cases of P. malariae in Guangdong Province over the years. This article, for the first time, analyzes the characteristics of these cases using multidimensional epidemiological, clinical, and genetic data, aiming to provide a reference for improving malaria prevention and control measures.

Methods

A retrospective analysis of long-latency P. malariae cases in Guangdong Province (2014–2022) was conducted. Clinical data were obtained from medical records, and epidemiological and epidemic spot investigation data were collected. Genetic analysis of the P. malariae circumsporozoite protein gene was performed to trace infection origins.

Results

Seven cases of long - latency P. malariae infection were identified, with a notable female predominance (85.7%) and a mean age of 75.3 years. The cases were distributed across seven counties in six municipalities, showing a dispersed spatiotemporal distribution. Most cases (85.7%, 6/7) had a history of residing in Guangdong’s historical endemic regions (pre-1990s). Comprehensive case investigation suggests that the infection sources were either historical local transmission (6 cases) or Southeast Asian importation (1 case), with latency periods ranging from 7 to 50 years. Phylogenetic analysis indicated that the long-latency cases clustered within the Asian lineage, with nucleotide homology of 95% − 97%, which was distinct from the strains in Africa (homology: 92% − 95%). Clinical manifestations were non - specific, including fever, and some cases presented with an increase in the percentage of neutrophils and a decrease in albumin levels. Diagnostic delays (median: 4 days) highlighted challenges in identifying infections.

Conclusions

This study demonstrated that P. malariae can cause prolonged asymptomatic infections with latency periods extending up to 50 years and underscores the importance of enhanced malaria surveillance, particularly among older populations with unexplained fever in historically endemic areas. Future research should focus on understanding the mechanisms of long - term host - parasite interactions and improving diagnostic and preventive strategies.

Clinical trial number

not applicable.