Haemosporidia are common blood parasites of wild European passerines and raptors (prevalence in European blackbirds for example at near 100%). The most important genera of these parasites include Plasmodium and Haemoproteus, both of which form malaria pigment and can therefore be classified as malarial parasites, as well as Leucocytozoon. With our new PCR test, we can differentiate between three genera and the result will identify the parasite, if present, to genus level.
These parasites are widespread worldwide and diverse, currently, more than 200 species are described. The host range varies between parasite species and there are specific ones that only infect one bird species as well as generalists which can infect bird species of many different avian orders. Co-infections with more than one parasite species are common in wild birds.
The course of the disease ranges from peracute in susceptible bird species (e.g. penguins) to asymptomatic (e.g. blackbirds). The severity of symptoms depends on the parasite species, bird host species as well as age and immune status of the host. Symptoms vary from reduced condition, depression and anorexia to dyspnoea, anaemia, hepato- and splenomegaly and pulmonary oedema. In penguins, sudden death is possible. Birds which survive the acute phase of the infection often stay chronically infected for years. In these cases, the symptomatic stage of the infection can be reactivated any time if the animal is stressed or infected by another pathogen.