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The blood parasite diversity was studied in paddyfield warblers (Acrocephalus agricola) breeding in NE Bulgaria, SW Russia and S. Kazakhstan. Nine cytochrome b gene lineages were recorded, 4 belonging to Haemoproteus spp. and 5 to Plasmodium spp. The overall prevalence of haemosporidians was 33.3%. The composition of parasites varied geographically, with six lineages recorded in Russia, five lineages in Bulgaria and two lineages in Kazakhstan. Two lineages are described for the first time, i.e. ACAGR1 (belonging to Plasmodium sp. and recorded from a single bird in Russia) and ACAGR2 (belonging to Haemoproteus sp., recorded from Bulgaria and Russia). The latter lineage is the most widespread parasite in the Bulgarian population, scarce in Russia and absent in Kazakhstan. It is supposed that ACAGR2 has originated from the widespread lineage ACDUM1 differing from it by a single nucleotide. One lineage only (ACDUM2) occurs in all the three populations studied and is a nonspecific parasite known from various passerines. Six of the registered lineages have been found in a single population of A. agricola and also represent non-specific parasites occurring in a wide range of passerine birds. Their records in A. agricola may indicate the high transmission rate of these parasites in the habitats where this host co-occurs with other passerines. The variation of the composition of the haemosporidian parasite communities through the breeding range of A. agricola makes up heterogeneous selection pressures that may drive intraspecific variation in important life-history traits.
Species that are introduced to novel environments can lose their native pathogens and parasites during the process of introduction. The escape from the negative effects associated with these natural enemies is commonly employed as an explanation for the success and expansion of invasive species, which is termed the enemy release hypothesis (ERH). In this study, nested PCR techniques and microscopy were used to determine the prevalence and intensity (respectively) of Plasmodium spp. and Haemoproteus spp. in introduced house sparrows and native urban birds of central Brazil. Generalized linear mixed models were fitted by Laplace approximation considering a binomial error distribution and logit link function. Location and species were considered as random effects and species categorization (native or non-indigenous) as fixed effects. We found that native birds from Brazil presented significantly higher parasite prevalence in accordance with the ERH. We also compared our data with the literature, and found that house sparrows native to Europe exhibited significantly higher parasite prevalence than introduced house sparrows from Brazil, which also supports the ERH. Therefore, it is possible that house sparrows from Brazil might have experienced a parasitic release during the process of introduction, which might also be related to a demographic release (e.g. release from the negative effects of parasites on host population dynamics).
This study presents data from a molecular survey of the species of the genus Culicoides from the region of Kalimok Field Station (NE Bulgaria) and haemosporidian parasites occurring in them in order to investigate the host-parasite specificity of haemosporidians to their dipteran vectors. The identification of Culicoides spp. was carried out by morphological and molecular-genetic methods. We collected and analysed 230 individuals of the genus Culicoides. Nine species were found. Eight species were identified morphologically; Culicoides obsoletus, C. riethi, C. newsteadi, C. circumscriptus, C. festivipennis, C. punctatus, C. pictipennis and C. puncticollis. The ninth species might be classified as either of C. nubeculosus or C. riethi and its identification needs additional investigations. The total prevalence of Haemoproteus in the examined biting midges was 2.17%. Three individuals of C. pictipennis were infected with the Haemoproteus lineage TURDUS2 (prevalence 16.67%), a common parasite of thrushes (Turdidae). Two individuals of C. circumscriptus contained Haemoproteus lineages (prevalence 2.78%); these were the lineage HAWF2 (previously reported from Coccothraustes coccothraustes) and a new lineage CULCIR1 not previously reported in the literature.
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