The study used molecular xenomonitoring, a surveillance approach in which mosquitoes themselves are tested for pathogen DNA rather than relying on detections in dogs or humans. Because mosquitoes acquire the parasite when they feed on infected hosts, detecting its genetic material in the insects can signal that transmission is occurring in the environment, even when clinical cases have not yet been documented.

Between June and September 2025, the team collected adult mosquitoes weekly at Laguna de Lagartos in Veracruz, using CDC ultraviolet light traps positioned at three sampling sites around the lagoon. The site is a recreational water body within an urban setting, an environment where people, pets, and mosquitoes intersect closely.

Each captured mosquito was identified morphologically and processed individually for DNA extraction using a Chelex-based protocol. Detection of D. immitis DNA was carried out by conventional polymerase chain reaction targeting the parasite’s 18S ribosomal RNA gene, a standard genetic marker for identifying filarial nematodes.

In total, 172 mosquitoes representing seven species across four genera were analyzed. The parasite’s DNA was found in 9 of the 172 specimens, an overall detection rate of 5.23 percent. Sequencing of the amplified fragments and phylogenetic reconstruction confirmed that the detected parasite corresponded to D. immitis rather than a related filarial species.

A striking pattern emerged when the positives were examined by species: every positive sample belonged exclusively to Culex (Melanoconion) panocossa. Within that species, 10.11 percent of tested individuals carried detectable parasite DNA, suggesting it may play a role in local transmission dynamics around the lagoon.

D. immitis is a zoonotic nematode of veterinary and public health importance. In its canonical canine host, the worm matures in the heart and pulmonary arteries, causing heartworm disease, while accidental human infections typically result in nonviable pulmonary nodules. Its dependence on mosquito vectors means that mapping which local species carry the parasite is a key step in assessing risk.

Veracruz’s warm, humid climate is favorable for the persistence of mosquito populations and the pathogens they transmit, yet molecular surveillance of D. immitis in local mosquitoes has remained sparse. The authors note that this gap motivated the present study, which they frame as a first step in documenting vector-parasite associations at this urban site.

The researchers conclude that the detection of D. immitis DNA in Cx. panocossa from the lagoon supports local parasite circulation and demonstrates the usefulness of mosquito-based xenomonitoring as a complementary epidemiological surveillance tool. Such monitoring could complement conventional veterinary testing by revealing where and when infected mosquitoes are active.

As a brief report based on one lagoon and a single collection season, the study’s scope is limited, and detection of parasite DNA in a mosquito does not by itself establish the insect’s competence as a vector or quantify risk to dogs or people in the area. Nonetheless, the species-specific pattern observed here offers a concrete starting point for broader surveillance efforts along Mexico’s Gulf coast.

Subject of Research: Molecular xenomonitoring of Dirofilaria immitis in mosquitoes from an urban lagoon in Veracruz, Mexico

Article Title: Molecular Xenomonitoring of Dirofilaria immitis in Mosquitoes From an Urban Recreational Lagoon in Veracruz, Mexico

Article References: Herrera-Rodriguez, K., Ortiz-Carbajal, L. A., Sánchez-Otero, M. G., Sánchez-Montes, S., Palmeros-Exsome, C., Bustos-Baena, A., Bravo-Ramos, J. L., & Ramos, J. L. B. (2026). Molecular Xenomonitoring of Dirofilaria immitis in Mosquitoes From an Urban Recreational Lagoon in Veracruz, Mexico. Acta Parasitologica, 71(6), Article 247. https://doi.org/10.1007/s11686-026-01433-8

Image Credits: AI Generated

DOI: 10.1007/s11686-026-01433-8

Keywords: Dirofilaria immitis, heartworm, mosquitoes, xenomonitoring, Culex panocossa, Veracruz, Mexico, zoonosis, PCR, vector-borne disease, public health surveillance, Molecular