article · Malaria Journal
Rodent malaria parasites are widely used as laboratory models for human malaria, yet their wild ecology remains poorly understood. An 18-month field study in southeastern Gabon investigated natural parasite interactions in the thicket rat, the primary wild host of murine Plasmodium species in Central Africa. Across twelve forest fragments, field sampling deployed 12,150 trap-nights and inspected 1,380 nests. Despite this intensive effort, only 20 adult thicket rats were captured, all via direct nest collection rather than standard traps. Diagnostic testing using two sensitive nested-PCR assays detected no Plasmodium infections among the captured animals. This finding contrasts with earlier reports of high infection rates in other Central African regions. The absence of detected parasites suggests local extinction, lack of suitable vectors, or host resistance. Natural transmission appears highly constrained, highlighting significant difficulties in obtaining fresh wild parasite isolates to update ageing laboratory strains.
Laboratory research into human malaria depends heavily on rodent parasite models, but the strains used today were isolated decades ago and passaged repeatedly. Securing fresh parasite strains from natural hosts is vital to reflect contemporary genetic diversity and improve drug and vaccine discovery. Discovering that wild reservoir transmission is locally absent or highly patchy reveals key obstacles to refreshing these critical research tools.
This early-stage ecological research does not present an immediate commercial product. However, pharmaceutical companies, academic drug discovery groups, and vaccine developers relying on rodent malaria models could ultimately benefit if updated wild isolates are successfully secured. Current laboratory lines are decades old, so accessing fresh strains could improve preclinical model fidelity. At present, because no parasites were isolated, practical biomedical application remains at a very early and exploratory stage.
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Abstract Rodent malaria parasites have long served as essential experimental models for understanding human malaria, yet little is known about their ecology and evolution in the wild. The thicket rat Grammomys poensis (formerly Thamnomys rutilans ) is considered the main natural host of murine Plasmodium species in Central Africa. This study aimed to establish a long-term field site to investigate Plasmodium-Grammomys interactions under natural conditions in southeastern Gabon. Over a period of 18 months, trapping was conducted across twelve forest fragments in the Batéké Plateau region using both Tomahauk traps and direct collection at nest. Despite an intensive effort (12,150 trap-nights and 1380 nests inspected), only 20 adult Grammomys were captured, all by collection directly at nest, and none were infected with Plasmodium as determined by two sensitive nested-PCR assays targeting the cytb gene, suggesting extremely low transmission or absence of parasite circulation in the study system. These results contrast with earlier studies reporting high infection prevalence in Grammomys from other Central African regions. The absence of infection may reflect local extinction of Plasmodium lineages, limited vector exposure due to the absence of species feeding on arboreal rodents, or host resistance. Because the rodent malaria lines currently used as experimental models in laboratories worldwide were isolated decades ago and have since been maintained through serial passage, access to recent field isolates would be highly valuable for capturing contemporary natural diversity and for enhancing the ecological, evolutionary, and biomedical relevance of these model systems. This study highlights both the challenges of studying this host-parasite system in the wild and the possibility that rodent Plasmodium transmission in this system may be more spatially and ecologically constrained than previously assumed.
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DOI: 10.1186/s12936-026-06087-5
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