The Trichuris trichiura whipworm is a soil-transmitted helminth that infects ≈500 million persons worldwide (1). Despite environmental transmission through infective eggs, T. trichiura is generally considered to be maintained exclusively by humans and nonhuman primates (2). Although whipworms infect a wide range of mammalian hosts, including rodents (3,4) and marsupials (5), Trichuris species whipworms generally are considered host-specific, and experimental studies show that T. trichiura does not readily establish patent infections in rodents or other nonprimate hosts (1; K.A. Stark et al., unpub. data, https://doi.org/10.1101/2025.05.09.653168). All major soil-transmitted helminths, including T. trichiura, are endemic in Papua New Guinea (7; J.L. Scott, master’s thesis, James Cook University, 2023). We investigated Trichuris whipworm infections in wild mammals in Papua New Guinea and unexpectedly identified T. trichiura in multiple endemic rodents.

We sampled mammals during 2019–2023 at 19 localities across 2 mountain systems and 3 lowland sites (Appendix 1 Figure 1). We examined the cecum and colon of 874 animals for whipworms (Appendix 1; Appendix 2 Table). The Ethical Committee of the Faculty of Science, University of South Bohemia approved the animal research protocol (approval no. 2019-1).

Rodents in Papua New Guinea come from 2 major murine lineages: Rattini, which includes endemic and introduced Rattus species, and Hydromyini, an endemic Australo–Papuan adaptive radiation occupying diverse ecologic niches. Of the 874 tested animals, 43 marsupials tested negative for whipworms, although the small sample distributed across multiple taxa precludes inference regarding their susceptibility. Sixteen rodents harbored Trichuris spp. whipworms: 7 Rattus niobe rats and 9 Hydromyini rodents representing 7 species (Table). The 7 infections in R. niobe rats occurred at a single location, whereas infections in Hydromyini rodents were distributed among several locations and host lineages.

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Figure. Maximum-likelihood phylogeny of the genus Trichuris whipworms from study of natural Trichuris trichiurainfections in endemic Hydromyini rodents, Papua New Guinea, 2019–2023. Phylogeny is based on mitochondrial...

Because morphologic species delimitation within Trichuris is difficult, we genetically characterized worms from 11 infected rodents (Appendix 1). The mitochondrial genomes of 8 specimens shared 97.5%–97.7% nucleotide identity with a human-derived T. trichiura reference sequence from Ecuador (GenBank accession no. AP017704) (Appendix 1 Table 2). Each genome represented a distinct mitochondrial haplotype. Maximum-likelihood phylogenetic analysis placed all 8 genomes within the T. trichiura clade (100% bootstrap support) (Figure), together with isolates from humans and nonhuman primates. Those isolates clustered within a subclade containing isolates from Asia and South America, and the closest relatives were derived from human infections in Ecuador and Honduras. Independent analysis of the nuclear internal transcribed spacer 2 marker corroborated their identification, placing the same 8 specimens within T. trichiura (100% bootstrap support) (Appendix 1 Figure 2). The remaining 3 characterized specimens, from 2 R. niobe rats and 1 Hydromys chrysogaster rakali, clustered within divergent rodent-associated Trichuris lineages.

The 8 T. trichiura infections occurred in 6 Hydromyini species (Hyomys goliath rats, Mallomys hercules rats, Pogonomys macrourus mice, P. loriae mice, Uromys caudimaculatus rats, and Uromys spp. rats) at 4 locations on both mountain systems and across the 2019, 2020, and 2023 sampling periods. Those hosts represent distinct Hydromyini phylogenetic lineages and include terrestrial and scansorial species, suggesting that infection is not restricted to a single host lineage or ecology.

Worm burdens varied among infected rodents; of note, 122 worms were recovered from 1 M. hercules rat. Adult female worms containing developed eggs were observed (Appendix 1 Figure 3), providing evidence of reproductive maturation in naturally infected Hydromyini rodents. However, we did not assess egg viability or subsequent transmission; our findings therefore do not establish transmission competence or reservoir status.

The occurrence of T. trichiura worms in several Hydromyini species expands the recognized natural host range of a parasite generally associated with humans and nonhuman primates. Repeated spillover from humans remains possible because environmentally resistant T. trichiura eggs provide opportunities for cross-species exposure. However, detection in several rodent species at multiple locations in different years and with distinct mitochondrial haplotypes raises the possibility of circulation among wild rodents. Hydromyini are broadly distributed across New Guinea and neighboring regions (7), suggesting that this host association might not be restricted to the sampled populations in Papua New Guinea. If rodents produce viable and infectious eggs, they could also be a source of infection for humans. That possibility is particularly relevant because 5 of the 8 T. trichiura–infected rodents were obtained through hunter-assisted sampling. Wild rodents are commonly hunted for food in Papua New Guinea, providing an interface between humans and native forest rodents (8). That practice increases human–rodent contact and could enable parasite transmission between the two. Distinguishing those transmission pathways will require assessing the infectivity of rodent-derived eggs and comparing T. trichiura populations from sympatric humans and wildlife.

Our findings identify an unexpected nonprimate component of T. trichiura ecology. From a One Health perspective, if infected rodents contribute to environmental contamination with viable eggs, transmission could persist outside treated human populations, potentially complicating prevention and control efforts. Our study highlights the need to consider wildlife when investigating T. trichiura transmission in endemic settings.

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Suggested citation for this article: Moradpour N, Vejmělka F, Okena DS, Novotný V, Bryjová A, Čížková D, et al. Natural Trichuris trichiura infections in endemic Hydromyini rodents, Papua New Guinea, 2019–2023. Emerg Infect Dis. 2026 Dec [date cited]. https://doi.org/10.3201/eid3212.261101