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A study carried out in Extremadura reveals the potential role of invasive exotic birds (coral beak, red bengal, yellow weaver) in the dynamics of local pathogen transmission in the areas they invade, even acting as reservoirs and amplifiers of newly acquired hemosporidial parasites.
Our invasive alien species (IAS) they are exotic species capable of colonizing new areas and establishing viable populations beyond their natural range. IAS can carry zoonotic pathogens, such as avian influenza or West Nile virus, affecting not only native species, but also human health, and imposing economic costs. Therefore, the study of IAS, its pathogens and its possible harmful effects on native populations would have important implications for both human and animal health and for the conservation of biodiversity.
Malaria would be another disease caused by blood parasites (haemosporidia) transmitted by mosquitoes. Among the hemosporidia that infect birds are the genera plasmodium, Haemoproteus y leukocytozoon, which include the causative agent of avian malaria (plasmodium spp.). Although the lineages that infect birds cannot be transmitted to humans, they are capable of infecting a large number of bird species worldwide, causing severe effects on the survival, body condition, and reproductive success of their hosts. For example, the accidental introduction of mosquitoes Culex quinquefasciatus and avian malaria Plasmodium relictum in the Hawaiian Islands is often cited as a typical example of the devastating impact of invasive diseases on native bird communities, since by not presenting immune defenses against these parasites many bird species became extinct.
Host-specific characteristics, such as their morphology, behavior, or physiological traits, could determine the susceptibility of individuals or species to malaria infection and thus influence their role as a potential reservoir and amplifier of infection. Thus, the study of the prevalence and diversity of avian malaria parasites in populations of exotic birds is crucial for the conservation of biodiversity.
The common coral bill (astrild)? It is a species of passerine bird of the Estrildidae family native to Sub-Saharan Africa, but it has been introduced to the Iberian Peninsula by accidental escapes after being acquired as a pet (Photo: Jaime Muriel).
Within the regional project “Factors that promote biological invasions in birds and reptiles of Extremadura“ (IB16121, led by Alfonso Marzal), researchers from the University of Extremadura (UEx), the Doñana Biological Station (EBD-CSIC), and the Research Group in Game Resources and Wildlife Management of the Instituto de Investigación en Recursos Cinegéticos (IREC – CSIC, UCLM, JCCM) have analyzed the prevalence and diversity of malaria and other hemosporidia in three exotic passerine species (coral beak, red bengal, yellow weaver) common in wetlands in southwestern Spain.
They have also explored possible relationship between body condition, hematocrit, and uropygial gland volume with infection by these parasites, since infected individuals would be expected to show lower values than non-infected individuals.
The study area is located near Casas Aisladas de Gévora, about 7 km north of the city of Badajoz. The area is made up of a group of rice fields, which alternate with fallow plots or abandoned stubble, constituting the characteristic agrarian mosaic of the Las Vegas Bajas del Guadiana region.
The results show a lower prevalence of hemosporidial infection in invasive passerines in the study area (2,17% leukocytozoon, and 1,57% plasmodium) than those found in these same species within their natural distribution area (around 30%). The lineages detected in this study are often found in native birds of the Iberian Peninsula, however, No lineage of those that these species usually present in their natural distribution area was detected..
This agrees with the Enemy Release Hypothesis, which states that colonizers that settle successfully tend to harbor a reduced community of parasites from their native area compared with their native conspecifics, either because they were absent on the colonizers or because the parasites were lost during transit or after settlement. arrival. These results alert us to a potential increased risk of acquiring local diseases as parasites that infect IAS could amplify and spread to native species..
Although hemosporidial infection apparently had no effect on the physiological variables considered (condition, hematocrit, uropygial gland volume), the differences between species could be explained by the differential susceptibility to hemosporidial parasites, where the reproductive phenology of each species could have a main role..
Taken together, the results of this scientific work could help to better understand the ability of exotic bird species to colonize new territories beyond their natural distribution area, providing information on their role in the dynamics of local pathogen transmission in the areas they invade. Specifically, the authors claim a increased attention to the possible impact of IAS on the transmission dynamics of local pathogens in invaded areas, underlining the importance of studies that integrate ecologists, parasitologists and the health sector to design coordinated policies on control and eradication programs. On the other hand, they highlight the need to encourage initiatives focused on inform citizens about the ecological impact and health threats of Invasive Alien Species in order to promote responsible behavior.
The scientific publication of this research is available at:
- Muriel, J., García-Longoria, L., Magallanes, S., Ortiz, JA, Marzal A. 2023. Avian malaria, haematocrit, and body condition in invasive wetland passerines settled in southwestern Spain. Avian Research 14, 100081.
