Abstract
BackgroundMalaria parasites and related haemosporidian parasites are widespread and may cause severe diseases in birds. These pathogens should be considered in projects aiming breeding of birds for purposes of sustained ex situ conservation. Cranes are the ‘flagship species’ for health assessment of wetland ecosystems, and the majority of species are endangered. Malaria parasites and other haemosporidians have been reported in cranes, but the host-parasite relationships remain insufficiently understood. Morbidity of cranes due to malaria has been reported in Beijing Zoo. This study report prevalence, diversity and distribution of malaria parasites and related haemosporidians in cranes in Beijing Zoo and suggest simple measures to protect vulnerable individuals.MethodsIn all, 123 cranes (62 adults and 61 juveniles) belonging to 10 species were examined using PCR-based testing and microscopic examination of blood samples collected in 2007–2014. All birds were maintained in open-air aviaries, except for 19 chicks that were raised in a greenhouse with the aim to protect them from bites of blood-sucking insects. Bayesian phylogenetic analysis was used to identify the closely related avian haemosporidian parasites.ResultsSpecies of Plasmodium (5 lineages), Haemoproteus (1) and Leucocytozoon (2) were reported. Malaria parasites predominated (83% of all reported infections). The overall prevalence of haemosporidians in juveniles was approximately seven-fold higher than in adults, indicating high susceptibility of chicks and local transmission. Juvenile and adult birds hosted different lineages of Plasmodium, indicating that chicks got infection from non-parent birds. Plasmodium relictum (pSGS1) was the most prevalent malaria parasite. Mortality was not reported in adults, but 53% of infected chicks died, with reports of co-infection with Plasmodium and Leucocytozoon species. All chicks maintained in the greenhouse were non-infected and survived. Species of Leucocytozoon were undetectable by commonly used PCR protocol, but readily visible in blood films.ConclusionCrane chicks often die due to malaria and Leucocytozoon infections, which they likely gain from wild free-living birds in Beijing Zoo. Molecular diagnostics of crane Leucocytozoon parasites needs improvement. Because the reported infections are mainly chick diseases, the authors recommend maintaining of juvenile birds in vector-free facilities until the age of approximately 6 months before they are placed in open-air aviaries.
Highlights
Malaria parasites and related haemosporidian parasites are widespread and may cause severe diseases in birds
Mortality was not reported in adults, but 53% of infected chicks died, with reports of co-infection with Plasmodium and Leucocytozoon species
It is probable that the lineage pGRUNIG01 belongs to Plasmodium elongatum, a cosmopolitan virulent malaria parasite, which causes disease and even mortality in many bird species belonging to different orders [41,42,43]
Summary
Malaria parasites and related haemosporidian parasites are widespread and may cause severe diseases in birds. Avian haemosporidian parasites (Haemosporida) of the genera Plasmodium, Haemoproteus and Leucocytozoon are widespread and can cause diseases in wild and domestic birds. They have been subjects of much research [1,2,3,4,5]. Parasitological studies in zoos and other centres usually are under professional veterinary control and provide valuable information about parasites This is valuable in case of large protected bird species, which are difficult to sample in the wild [15]. Scott was the first to publish information about severe diseases caused by haemosporidian parasites in captive zoo birds in London [16, 17], and severe haemosporidioses were reported subsequently in many zoos in Asia, Europe, South and North
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