A study found that vampire bats in northern Belize harbored 5 genetic lineages of Trypanosoma cruzi, including 2 not previously documented in the country, and that 42% of sampled bats were infected. The findings suggested potential connections between wildlife and domestic transmission cycles, although the study did not establish direct transmission to humans.
Researchers analyzed 207 blood samples from common vampire bats (Desmodusrotundus) collected during 2019, 2021, and 2022 at 2 sites in northern Belize: the Lamanai Archaeological Reserve and Ka’Kabish. The sites were approximately 8 km apart in a landscape comprising forest fragments, agricultural areas, and pastures. Researchers used 2 polymerase chain reaction assays to identify T. cruzi infection, followed by molecular genotyping and next-generation sequencing of selected positive samples.
The primary analyses assessed infection prevalence and genetic diversity, classified as discrete typing units (DTUs). Researchers also assessed differences in infection probability by sampling location, year, bat age, sex, and reproductive status, and compared parasite sequences with those previously identified in insect vectors and human infections in Belize to explore potential epidemiological connections.
Overall, 86 of 207 bats (42%) tested positive for T. cruzi. The kinetoplast DNA assay identified 84 positive samples (41%), whereas the satellite DNA assay identified 53 (26%). Both assays detected infection in 51 samples, with 33 positive only by the kinetoplast assay and 2 positive only by the satellite DNA assay.
Among 62 positive samples with sufficient remaining DNA for genotyping, the researchers selected 10 high-quality samples collected in 2022 for next-generation sequencing. These yielded 36 distinct haplotypes belonging to 5 DTUs: TcI, TcIV, TcV, TcVI, and TcBat. The detection of TcBat and TcVI represented the first documentation of these lineages in Belize.
TcBat accounted for 68% of sequencing reads recovered from the selected samples. Several TcBat haplotypes clustered closely with Colombian reference sequences, whereas others formed a distinct Belize-specific genetic group. Brazilian TcBat sequences were more distantly related, indicating geographic variation within this lineage.
The remaining sequencing reads were associated primarily with TcVI (23%), TcI (6%), and TcIV (3%), along with a single TcV haplotype. Individual bats carried between 1 and 9 haplotypes, but all haplotypes detected within a given bat belonged to the same DTU. Researchers therefore identified genetic diversity within parasite lineages rather than mixed-DTU infections in individual bats.
The detection of TcV and TcVI was notable because these lineages have established associations with human Chagas disease in South America. Additionally, a TcIV haplotype recovered from a vampire bat clustered with sequences previously identified in triatomine insect vectors and a 2020 human infection in Belize. Although this genetic overlap suggested potential connections between wildlife and human transmission networks, it did not establish direct transmission between hosts.
In adjusted analyses restricted to samples collected in 2019 and 2022, bats at the Lamanai Archaeological Reserve had approximately 2.9 times the odds of T. cruzi infection compared with those at Ka’Kabish. Infection odds in 2022 were also approximately 3.6 times those observed in 2019. A separate analysis restricted to Lamanai found that infection odds in 2022 were approximately 3.8 times those in 2019 and 6.5 times those in 2021. Bat age, sex, and reproductive status were not associated with infection probability.
Sampling was restricted to 2 sites across 3 field seasons, with unequal sampling effort and incomplete seasonal coverage. Only 10 positive samples underwent next-generation sequencing, limiting the ability to characterize parasite diversity across the broader bat population or estimate the frequency of individual DTUs. The study also did not assess insect vector abundance, blood meal sources, or host immune function. Consequently, the findings could not establish specific transmission pathways, and the observed temporal differences required cautious interpretation.
Vampire bats may contribute to maintaining genetically diverse T. cruzi populations in northern Belize, including lineages associated with human disease. Authors emphasized the need for integrated surveillance involving bats, insect vectors, domestic animals, and humans to better characterize transmission networks and assess potential Chagas disease risks.
“Given that D. rotundus feeds regularly on livestock and occasionally on humans, these bats may act as potential bridge hosts that could facilitate spillover between sylvatic, domestic, and human cycles,” wrote lead study author Annalise Dunsmore, of the Department of Tropical Medicine at Tulane University, and colleagues.
The authors declared no competing interests.
Source: PLOS Neglected Tropical Diseases