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All 40 Lisbon Feral Pigeons Carried Haemoproteus columbae

Feral pigeon perched on a railing
Research: Disease, parasites & microbiology, Genetics & genomics

All 40 feral pigeons examined at two sites in Lisbon were infected with the blood parasite Haemoproteus columbae, according to a study published on 3 April 2026. Feral pigeons are the domestic-derived form of rock dove (Columba livia), and the researchers combined microscopy with DNA analysis to investigate parasite prevalence and diversity.

H. columbae is a haemosporidian blood parasite. Haemosporidians are widespread in birds and can affect health and fitness even when infection is not obviously lethal, which makes both prevalence and parasite diversity biologically relevant.

The birds came from Alameda Afonso Henriques and Jardim da Estrela and had been captured as part of Lisbon City Council’s existing pigeon-control programme. They were not collected specifically for the research.

Four genetic parasite lineages were detected

Microscopy and molecular analysis identified four lineages of H. columbae: HAECOL1, COLIV03, COQUI05 and CXNEA02. HAECOL1 dominated, occurring in about 85% of the successfully genotyped birds.

All four lineages were new geographic records for Portugal. COLIV03, COQUI05 and CXNEA02 were reported in Europe for the first time, and the combined morphological and genetic evidence allowed CXNEA02 to be assigned to H. columbae for the first time. No Plasmodium or Leucocytozoon infections were detected.

Double gametocyte infections were linked to poorer condition

The researchers also recorded double gametocyte infections in 19 of the 40 birds (47.5%), where two parasite gametocytes — the sexual blood stages that can continue the parasite’s life cycle in its insect vector — occupied the same red blood cell. Parasitaemia — the proportion of red blood cells carrying parasites — ranged from 0.05% to 8.11%. Birds with double gametocyte infections had higher parasitaemia and lower body-condition scores than birds without them. Male–female double infections were found only within the dominant HAECOL1 lineage, a pattern the authors suggest may be relevant to transmission dynamics.

Microscope images showing double and triple Haemoproteus columbae gametocyte infections in pigeon red blood cells
Double and triple gametocyte infections of Haemoproteus columbae in pigeon red blood cells. Figure 2 from Cruz et al. (2026), Journal of Ornithology, CC BY 4.0.

When the researchers analysed body condition using both parasitaemia and the presence of double gametocyte infections, the double infections remained associated with poorer body condition, whereas parasite density itself did not show a clear independent relationship. The authors therefore highlight infection complexity, rather than parasite density alone, as an important feature of this system.

Sources and image credit

  1. Cruz, J. T., de Carvalho, L. M., Quaresma, M. A. G., Pericão, A., Reisinho, A., & Marzal, A. (2026). Uncovering haemosporidian diversity in urban Feral Pigeons (Columba livia domestica) in Lisbon, Portugal: Integrated molecular and morphological insights. Journal of Ornithology, 167, 747–759.Primary open-access study, published 3 April 2026. All 40 sampled feral pigeons carried Haemoproteus columbae; four lineages were detected and double gametocyte infections were associated with poorer body condition.

Image: Chuck Homler / FocusOnWildlife.Me — feral pigeon (Columba livia) perched on a fishing-pier railing in Ocean City, New Jersey, USA, photographed 3 May 2025; Wikimedia Commons; representative species image. · CC BY-SA 4.0 · Source

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