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Malaria - the formidable enemy of humanity

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Malaria, a disease caused by protozoan parasite of the genus Plasmodium, is an ancient enemy of the human race. Despite enormous efforts to control, it is still a main cause of morbidity and mortality in many endemic countries of the world, particularly Africa, South of Sahara. Malaria seems to be unstoppable due to lack of an effective vaccine, acquisition of drug-resistance by malaria parasite, and insecticide resistance by Anopheles mosquitoes. In this scenario, along with search for novel preventive approaches, adequate health facilities, health literacy and awareness among people are required to control and eliminate this formidable disease from society.
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).
As a result of a survey of 362 birds, data were accumulated concerning the influence of migration and seasonal distribution of the Protozoa of the genus Plasmodium, Haemoproteus, Leucocytozoon and Lankesterella and Microfilariae. Material for study consisted of blood films which had been collected over two years. The smears were stained with Giemsa stain and each was examined approximately twenty minutes. The monthly incidence of infections is shown in Table 1. Plasmodium was found in 8.3 per cent of all atudied birds, from March to December with the highest intensity during the summer period. The non-migratory birds were infected in 81 per cent (of all infected with Plasmodium birds). Haemoproteus was established in 6.4 per cent from April to October. In majority this protozoan was found in migratory birds (70 per cent of all infected with Haemoproteus birds). The most popular in Poland are the protozoans of the genus Lankesterella and Leucocytozoon. These two genus were found in Poland through the all years. Leucocytozoon was found in 12.4 per cent. In majority this parasite was established in birds of the family Corvidae (78.5 per cent of all infected with Leucocytozoon birds). Corvus frugilegus was caught in majority in the winter period and it was infected in 57.7 per cent. It is interesting because the birds, which are in winter in Poland were coming from north and east. Microfilariae were found through the all year and 50 per cent of Corvidae were infected with this parasite.
We describe and discuss species of Plasmodium with four nuclei arranged in doublets or forming a maltese cross and loose, residual cytoplasm, described from Passer hispaniolensis in Algeria. The following species are described: Plasmodium rouxi from Alauda arvensis, from France Plasmodium mohammedi sp. nov. from Passer domesticus biblicus and Plasmodium pachysomum sp. nov. from Anthus campestris, from Israel, Plasmodium pfefferi sp. nov. from Pica pica and Plasmodium sergentorum sp. nov. from Alauda arvensis and Pica pica from France and Plasmodium stellatum sp. nov. from Muscicapa striata from Israel. All species vary in the spatial position of their four nuclei and the presence or absence of refractile, blue-staining globules. All of the described species differ from P. vaughani Novy et Mac Neal, 1904 and its siblings (example: P. vaughani merulae Corradetti et Scanga, 1973) in their number of merozoites (always four versus four to eight in the latter) and their spatial arrangement in the schizont.
A reticulocytosis induced by injections of phenylhydrazine to white mice enhanced the gametocyte production of Plasmodium berghei. Gametocytogenesis of P. yoelii and P. vinckei petteri were not affected by phenylhydrazine treatment.
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