Abstract

Avian malaria is a vector-borne disease, globally distributed, caused by protozoal parasites belonging to the Plasmodium genus.¹ Fifty-five Plasmodium species have been described based on morphological criteria, but genetic sequences are only available for a limited number of these species.² Clinical presentations in birds vary from subclinical to lethal infections, the latter previously described in Spheniscidae, where acute mortality is reported due to intravascular coagulopathy secondary to severe endothelial damage.³ After one suspicious lethal case in a common guillemot (Uria aalge) housed at the Oceanogràfic Northern Seas multi-specific indoor exhibit, 25 birds were screened, including complete hematology (including blood smear evaluation), human malaria rapid test and PCR for the most common bird hemoparasites (Plasmodium spp., Haemoproteus spp., and Leucocytozoon spp.). Twenty common guillemots, one tufted puffin (Reticula cirrhata), two smews (Mergellus albellus), and two European oystercatchers (Haematopus ostralegus) were examined. Two sick feral pigeons (Columba livia) found outside in the surrounding gardens were euthanized and also sampled in the same manner to evaluate the presence of the parasite. Tissue samples from all dead animals (n=3) were collected for routine histopathological diagnosis and PCR. None of the human malaria rapid tests were positive, even in dead animals with high levels of parasitemia found in blood smears (>50%). Two of the animals tested through PCR (one guillemot and one oystercatcher) (2/25; 8%) were Plasmodium spp. positive, whereas the two feral pigeons were Haemoproteus spp. positive. After sequencing, Plasmodium relictum (pSGS1) and Haemoproteus columbae (hAECOL1 and hCOLIV3) were identified, respectively. Haemosporidian parasites were observed in different tissues (exoerythrocytic meronts) as well as in blood smears (merozoites and gametocytes) from the guillemot, the oystercatcher, and both pigeons. The low prevalence of Plasmodium spp. infection might indicate that the parasite was not circulating inside the exhibit despite the presence of vectors (mosquitoes), in which the occurrence of malaria parasites needs to be further evaluated. Local bird species evaluated did not show the same haemosporidian parasites; hence, the origin of P. relictum infection in the sea bird's indoor exhibit remains uncertain. The addition of subclinically infected animals in the collection could be a possible source. Also, additional studies focused on a higher number and other bird species (Passeriformes) that could act as reservoirs need to be conducted.

*Presenting author

Literature Cited

1.  Atkinson CT, Thomas NJ, Hunter DB, eds. Parasitic Diseases of Wild Birds. Ames, IA: Wiley-Blackwell; 2008.

2.  Grilo ML, Vanstreels RET, Wallace R, et al. Malaria in penguins—current perceptions. Avian Pathol. 2016;45(4);393–407. doi: 10.1080/03079457.2016.1149145.

3.  Valkiūnas G, Iezhova TA. Keys to the avian malaria parasites. Malaria Journal. 2018;17(1):212. doi: 10.1186/s12936-018-2359-5.