Epidemiological assessment of lymphocytic choriomeningitis virus transmission dynamics in urban rodent populations

Introduction

What determines the emergence of rodent-borne viral zoonoses in expanding urban landscapes? This question has gained attention as environmental modifications reshape interfaces between human communities and synanthropic rodent populations [1] . Lymphocytic Choriomeningitis Virus (LCMV), a bisegmented ambisense RNA virus of the family Arenaviridae, represents an underrecognized yet clinically significant zoonotic pathogen with worldwide distribution [2] . First isolated by Armstrong and Lillie in 1933, LCMV has been identified across diverse geographical regions, with Mus musculus serving as its principal natural reservoir [3] . The epidemiological significance of LCMV has been increasingly acknowledged following documented outbreaks in organ transplant recipients and congenital infections with devastating neurological consequences [4] . Despite these clinical observations, the true burden remains substantially underestimated, particularly in resource-limited settings where diagnostic capabilities are constrained [5] . Serological surveys in European and American populations have reported seroprevalence rates from 2% to 13%, with elevated rates among individuals with rodent exposure [6] . The African continent presents a complex epidemiological landscape for LCMV investigation, given the diversity of indigenous rodent species, the rapid pace of unplanned urbanization, and intimate cohabitation patterns between humans and commensal rodents [7] . Several African murid species, including Mastomys natalensis and Rattus rattus, have demonstrated capacity To harbor arenaviruses [8] . However, systematic investigations targeting LCMV in African urban rodent communities remain scarce [9] . South Africa provides an ideal setting for investigating urban LCMV epidemiology, and Cape Town, with diverse socioeconomic strata and heterogeneous rodent habitats, offers a representative model [10] . This research comprehensively assessed the seroprevalence, molecular detection rates, and ecological risk factors associated with LCMV infection among urban rodents in Cape Town.

Material and Methods

Material

Rodent specimens were collected from 84 geo-referenced trapping stations across residential areas (n = 22), market districts (n = 18), peri-urban farmlands (n = 16), warehouse districts (n = 14), and open waste dump sites (n = 14). Sherman live traps baited with peanut butter and rolled oats and snap traps were deployed along rodent runways. Each station comprised a 10-trap transect at 5-meter intervals, set for three consecutive nights per session. Blood was collected via cardiac puncture under isoflurane anesthesia. Serum was separated by centrifugation at 3000 rpm for 10 minutes and stored at -20°C. Kidney and brain tissues were preserved in RNAlater solution for molecular analysis.

Methods

Serological screening for LCMV-specific IgG antibodies was performed using indirect ELISA (EUROIMMUN AG, Lübeck, Germany) with validated murine secondary antibodies. Samples with absorbance ratios exceeding 1.1 were classified seropositive. Molecular detection of LCMV RNA was accomplished through RT-PCR targeting a 350-bp conserved region of the viral nucleoprotein gene. RNA was extracted using the RNeasy Mini Kit (QIAGEN), cDNA synthesized using SuperScript IV reverse transcriptase, and amplicons sequenced bidirectionally. Phylogenetic analysis was conducted using MEGA 11 with maximum likelihood method and 1000 bootstrap replicates. Multivariate logistic regression was performed using SPSS 28.0 with significance set at p<0.05.

Results

A total of 420 rodents belonging to five species were captured: Rattus norvegicus (n = 126, 30.0%), Mus musculus (n = 108, 25.7%), Rattus rattus (n = 84, 20.0%), Mastomys natalensis (n = 63, 15.0%), and Aethomys namaquensis (n = 39, 9.3%). The overall LCMV seroprevalence was 28.6% (120/420; 95% CI: 24.3-33.2%). Mastomys natalensis demonstrated the highest positivity at 41.3% (26/63), followed by Mus musculus at 34.7% (37/108) (Table 1).

Discussion

The present research represents the first comprehensive LCMV epidemiological assessment among urban rodents in South Africa. The overall seroprevalence of 28.6% is substantially higher than the 5-10% typically reported from European and North American surveys [9] , suggesting elevated zoonotic risk in the African urban context. This aligns with the hypothesis that greater diversity of susceptible rodent species in African environments may facilitate more efficient viral maintenance [10] . The predominance of LCMV in Mastomys natalensis (41.3%) is particularly noteworthy, as this species has been implicated as a Lassa fever virus reservoir but not extensively investigated for LCMV in southern Africa [5] . The elevated seroprevalence compared to Mus musculus (34.7%) challenges the paradigm positioning the house mouse as the exclusive LCMV reservoir and suggests indigenous African species may play a complementary role [11] . The strong correlation (r² = 0.87) between density and prevalence supports density-dependent transmission dynamics. Higher densities facilitate increased contact frequency and vertical transmission, enhancing viral amplification [12] . This relationship has been reported for hantaviruses and Lassa virus, reinforcing that rodent population management is a primary intervention point [13] .

The finding that residential areas harbored the highest seroprevalence (32.5%) underscores the importance of targeting domestic habitats in pest management, particularly in informal settlements where structural barriers to rodent ingress are inadequate [14] . Phylogenetic clustering with Old World LCMV lineages raises questions regarding historical LCMV dispersal into Africa, potentially linked to transcontinental rodent movement through maritime trade [15] .

Public health implications

The documentation of substantial LCMV seroprevalence among urban rodents near human dwellings carries profound public health implications. Zoonotic transmission potential is amplified by intimate cohabitation patterns, particularly in informal settlements where food storage practices and waste management deficiencies create favorable conditions for sustained human-rodent contact [14] . Given that LCMV can cause severe neurological disease in immunocompromised individuals and congenital malformations, the absence of routine surveillance represents a critical gap in preparedness.

One health perspective

These findings advocate for a One Health approach integrating veterinary, medical, and environmental health perspectives. Effective LCMV risk mitigation requires concurrent rodent monitoring, environmental sanitation improvement, clinical awareness enhancement, and laboratory capacity strengthening for arenavirus diagnostics [12] . Veterinary professionals occupy a strategic position, possessing the expertise to implement surveillance programs generating early warning data for public health authorities.

Conclusion

The present research evaluated the seroprevalence and ecological determinants of LCMV infection among urban rodents in Cape Town, South Africa, documenting an overall seroprevalence of 28.6% across five species, with Mastomys natalensis (41.3%) and Mus musculus (34.7%) as predominant reservoirs. The density-dependent transmission dynamics (r² = 0.87) and the association between seropositivity and proximity to human dwellings establish that urban communities face meaningful zoonotic risk at prevalence levels exceeding temperate-region surveys.

Acknowledgement

AcknowledgementsThe authors acknowledge the South African National Research Foundation for financial support and the Cape Town Institute of Veterinary Sciences for laboratory facilities. Ms. Lerato Khumalo and Mr. David Engelbrecht are thanked for field trapping assistance.

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