Detection of Bartonella spp. in Seabirds: A Public Health Concern

The emergence and re-emergence of zoonotic diseases are closely associated with anthropogenic factors that alter existing ecological dynamics and, consequently, previously established pathogen–host relationships. The increasing proximity among wildlife species, domestic animals, and humans favors different pathways for the circulation of pathogenic agents, resulting in the exposure of new susceptible hosts and potential reservoirs for diseases (Souza, 2021).

In recent decades, the incidence of zoonotic bacterial diseases in humans has increased (Bernal et al., 2023), including bartonellosis, an infection caused by the gram-negative bacillus Bartonella spp. Among the 45 described Bartonella species, 13 are potentially zoonotic (Bernal et al., 2022) and have been detected in wild mammals, their primary reservoirs (Souza, 2021).

Recently, several bird species have also been identified as hosts of bacteria belonging to the genus Bartonella. This bacterium was detected in seabirds along the Brazilian coast, specifically in the black-browed albatross (Thalassarche melanophris), Atlantic yellow-nosed albatross (Thalassarche chlororhynchos), and Magellanic penguin (Spheniscus magellanicus). Molecular characterization of the collected samples revealed a high correspondence between the gene regions identified in penguin samples and previously described Bartonella henselae sequences (Lee et al., 2025).

Infection by Bartonella henselae is very common in domestic cats and humans and is responsible for “cat scratch disease,” characterized by a self-limiting local lymphadenopathy. The flea Ctenocephalides felis felis plays an essential role in transmitting the infectious agent among felines (Pennisi et al., 2025), since the bacterium exhibits tropism for erythrocytes and endothelial cells (Bernal et al., 2022), which are ingested by the flea during blood feeding, allowing bacterial multiplication within the vector’s intestine and subsequent excretion through feces (Pennisi et al., 2025).

Figure 1. Immunohistochemical identification of Bartonella henselae in a case of cat scratch disease. Source: Pennisi et al., 2013.

The vectors involved in the transmission of Bartonella spp. in birds are still unknown; however, it is believed that transmission is associated with hematophagous ectoparasites (Lee et al., 2025). Arthropod vectors of bartonellosis mainly include mosquitoes, fleas, and ticks, which, when carried by wild birds, may be widely disseminated (Sacchi, 2015). There is even the possibility of cross-transmission between mammals and birds (Lee et al., 2025), representing an important challenge for public health.

Migratory birds play a fundamental role in the maintenance and dissemination of pathogens on a global scale. The crossing of national and international borders enables these animals to act as long-distance vectors for several microorganisms, creating new endemic hotspots for various diseases (Reed et al., 2003).

Furthermore, increasing human occupation of coastal areas and the closer interaction between domestic and wild animals, such as through abandonment and unrestricted access of cats to natural environments, allow greater contact among animals with urine and feces from other species, as well as increased predation of wildlife, especially seabirds during the nesting period (Ferreira et al., 2012). Improved investigation of interactions among birds, mammalian reservoirs, and hematophagous arthropods during migratory periods is crucial for understanding the epidemiological cycle of bartonellosis (Lee et al., 2025).

Therefore, it can be concluded that seabirds may act as potential reservoirs in the transmission of emerging zoonotic diseases, highlighting the importance of further studies on their participation in the epidemiological cycle of these diseases in order to guide the development of effective zoonotic surveillance and control strategies.

Author: Laís Gabriele Starke – Secretary Vice-Director of GEAS Brasil

Review: Iago Junqueira – Partner of GEAS Brazil through The Wild Place

Wildlife Panel – May/2026

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