A New Species of Plasmodium of the Subgenus Novyella Infecting White-Shouldered Fire-Eyes (Pyriglena leucoptera) (Aves: Thamnophilidae) in Brazil.

Plasmodium (Novyella) unalis sp. nov. was found in the Great Thrush, Turdus fuscater (Passeriformes, Turdidae) in Bogotá, Colombia, at 2,560 m above sea level where the active transmission occurs. This parasite is described based on the morphology of its blood stages and a fragment of the mitochondrial cytochrome b gene (lineage UN227). Illustrations of blood stages of new species are given, and the phylogenetic analysis identifies closely related species and lineages of avian malaria parasites. The new species is most similar to Plasmodium (Novyella) vaughani (lineage SYAT05), a cosmopolitan avian malaria parasite; these parasites are also closely related genetically, with a genetic difference of 3.2% between them. P. unalis can be readily distinguished from the latter species morphologically, primarily due to the (1) presence of a single large, circular shaped pigment granule in the erythrocytic trophozoites and meronts; (2) presence of prominent vacuoles in trophozoites and growing meronts; and (3) presence of predominantly fan-like shaped erythrocytic meronts. Cytochrome b lineages with high similarity to the new species have been reported in Costa Rica, Brazil, Chile, and USA. It is probable that the new species of malaria parasite is widely distributed in the New World. This parasite has been reported only in the Great Thrush at the study site and might have a narrow range of avian hosts. Records of P. unalis are of particular theoretical interest due to its active transmission at highlands in Andes. Possible influence of urbanization on transmission of this malaria parasite in Bogotá is discussed.

Numerous lineages of avian malaria parasites of the genus Plasmodium have been deposited in GenBank. However, only seven morphospecies have been linked to these lineages. This study linked two molecular sequences with morphospecies of malaria parasites. Two species of Plasmodium (mitochondrial cytochrome b gene lineages P-GRW2 and P-GRW4) were isolated from naturally infected adult great reed warblers (Acrocephalus arundinaceus) and inoculated to naive juvenile individuals of the same host species. Heavy parasitemia developed in the subinoculated birds, which enable identification of the species and deposition of their voucher specimens. Parasites of the lineage P-GRW2 were described as a new species, Plasmodium (Novyella) ashfordi, which is characterized primarily by the fan-like mature erythrocytic meronts containing seven to eight merozoites and the terminal position of clumped pigment granules in the gametocytes. Illustrations of the blood stages of the new species and Plasmodium (Haemamoeba) relictum (lineage P-GRW4) are given. The parasites of both lineages are transmitted in Africa and probably not in northern Europe. Other lineages closely related to P. ashfordi and P. relictum are identified. This study establishes the value of PCR-based identification of avian malaria parasites.

Plasmodium (Novyella) nucleophilum from an Egyptian Goose in São Paulo Zoo, Brazil: microscopic confirmation and molecular characterization

Malaria is the parasitic disease with the greatest impact on humans. It is an infectious disease caused by protozoa of the genus Plasmodium spp. and transmitted to humans by the bite of the mosquito Anopheles spp. Its incidence has increased in the tropical regions of Africa and Southeast Asia, areas already defined by the World Health Organization (WHO) as malarial zones [1]. In these places, malaria generally disappears at altitudes above 2.000 meters above sea level. The most frequently circulating parasites are P. vivax and P. falciparum; P. malarie is also widely distributed, but less frequent. In West Africa, P. ovale replaces P. vivax. The most widespread species in the world is P. vivax, which has been found from sea level to 2.770 meters above sea level. The endemic areas, however, are generally in the tropics. By definition, the number of parasites found in the peripheral blood depends on the species: the highest number corresponds to P. falciparum which infects 10 to 40% of all red blood cells; it is worth mentioning that when parasitaemia of this species reaches more than 25%, it is usually fatal [2]. Multiple invasion of red blood cells is frequent with P. falciparum, rare with P. vivax (which has a predominance of reticulocytes) and very rare with P. malariae [1- 3]. Without treatment, maximum parasite multiplication is reached in 2 weeks in P. vivax, and in 10 days in the case of P. falciparum. The simultaneous presence of erythrocytic parasitic forms (asexual and/or sexual) of two or more species of Plasmodium spp. is called mixed plasmodial infection. If, in addition, there are symptoms such as fever, chills, headache, sweating, among others, it corresponds to the disease called mixed malaria. In the world, the prevalence of this last entity is uncertain, depending on the diagnostic method used: 2% by light microscopy (e.g., thick blood smear [TBS] or peripheral blood smear) and up to 65% by polymerase chain reaction (PCR) [4]. In Latin America, prevalence is estimated at 0.46% by TBS and 12.8% by PCR. In terms of performance, the thick smear is 20-30 times more sensitive than the thin smear (peripheral blood smear), although less specific for the identification of the erythrocytic asexual (young rings or trophozoites, mature trophozoites, schizonts) and sexual (gametocytes) forms of the five species of Plasmodium spp. that parasitize humans (P. falciparum, P. vivax, P. ovale, P. malariae and P. knowlesi), which explains an underdiagnosis of both clinical scenarios (both plasmodial infection and mixed malaria) by light microscopy, with serious implications for diagnostic and therapeutic guidance. Nevertheless, some methods have been developed to improve the diagnostic capability of TBS [2,3]: • Fluorescent stains (acridine orange): used to increase sensitivity of point-of-care diagnosis, without improving specificity of species identification; additionally, some stains may be toxic. • Fluorescence staining + microcentrifuge: increases diagnostic speed and sensitivity for P. falciparum; reduces sensitivity for other species. • Magnetic deposition: takes advantage of the magnetic characteristics of hemozoin to precipitate the parasites to the plate with a magnet. It is an inexpensive method. It increases sensitivity; however, it is not species specific, without good representation of ring stage parasites.

Immunisation of mice and humans with attenuated sporozoites has been shown to confer sterile immunity against infection. There are ongoing efforts to develop a vaccine based on this system. Attenuation of sporozoites may be achieved via irradiation, genetic modification, or through the use of drugs targeting the blood stage parasite. Recently, it has been shown that the administration of chloroquine, a drug that acts exclusively against the erythrocytic stages of malaria parasites, concurrently with live sporozoites can induce sterile immunity against homologous challenge with Plasmodium falciparum sporozoites in humans. However, it is not known whether the protection achieved against P. falciparum will also protect against other species of human malaria parasites, which are almost always endemic in the same region. Given the high amount of antigen diversity within malaria parasite species, coupled with the large evolutionary distances between the human species, it seems unlikely that immunity to heterologous species would be achieved. Of concern is whether the development of an acute blood stage infection of a heterologous species may abrogate the immunity achieved against the vaccine target species. This phenomenon would have serious consequences for the deployment of an attenuated sporozoite vaccine in a multispecies endemic area. Here, we describe the results of experiments aimed at determining whether immunity achieved against one species of malaria parasite by sporozoite immunisation is protective against a secondary species, and whether the development of acute blood stage infections of the heterologous species abrogates the immunity achieved against the vaccine target species. As such experiments are currently impossible using human malaria parasite species, we have used the rodent malaria parasite species Plasmodium vinckei and Plasmodium yoelii. These two species were selected as they offer the widest possible evolutionary distance between rodent malaria parasites, although they are still much more closely related than any two of the human species. We found that although there was some cross protection between the species following sporozoite immunisation in conjunction with mefloquine treatment, the major component of this immunity was species specific. Mice immunised with P. yoelii sporozoites were completely protected against the development of blood stage infection following P. yoelii sporozoite challenge, whereas they were completely susceptible to infection with P. vinckei. Crucially, we found that the development of a blood stage infection of either species completely removed the sterile protection achieved via sporozoite immunisation.

Blood samples from 655 passerine birds were collected in rainforests of Ghana and Cameroon and examined both by microscopy and polymerase chain reaction (PCR)-based techniques. The overall prevalence of Plasmodium spp. was 46.6%, as determined by combining the results of both these diagnostic methods. In comparison to PCR-based diagnostics, microscopic examination of blood films was more sensitive in determining simultaneous infection of Plasmodium spp., but both detection methods showed similar trends of prevalence of malaria parasites in the same study sites. Plasmodium (Novyella) lucens n. sp., Plasmodium (Novyella) multivacuolaris n. sp. and Plasmodium (Novyella) parahexamerium n. sp. were found in the olive sunbird Cyanomitra olivacea (Nectariniidae), yellow-whiskered greenbul Andropadus latirostris (Picnonotidae), and white-tailed alethe Alethe diademata (Turdidae), respectively. These parasites are described based on the morphology of their blood stages and a segment of the mitochondrial cytochrome b (cyt b) gene, which can be used for molecular identification and diagnosis of these species. Illustrations of blood stages of new species are given, and phylogenetic analysis identifies DNA lineages closely related to these parasites. Malaria parasites of the subgenus Novyella with small erythrocytic meronts clearly predominate in African passerines. It is probable that the development of such meronts is a characteristic feature of evolution of Plasmodium spp. in African rainforest birds. Subgeneric taxonomy of avian Plasmodium spp. is discussed based on the recent molecular phylogenies of these parasites. It is concluded that a multi-genome phylogeny is needed before revising the current subgeneric classification of Plasmodium. We supported a hypothesis by Hellgren, Krizanauskiene, Valkiūnas, Bensch (J Parasitol 93:889-896, 2007), according to which, haemosporidian species with a genetic differentiation of over 5% in mitochondrial cyt b gene are expected to be morphologically differentiated. This study emphasises the importance of employing both PCR-based and microscopic methods in taxonomic, ecological and evolutionary investigations of avian haemosporidian parasites.

BackgroundNiger's National Malaria Control Programme and its partners use histidine-rich protein 2–based RDTs, which are specific to Plasmodium falciparum diagnosis. This study aimed to screen for the circulation of non-falciparum species in Zinder, a region of Niger, West Africa.MethodsA cross-sectional study was carried out from July to December 2022 at the district hospital of the Zinder region of Niger. P falciparum histidine-rich protein 2–based rapid diagnostic tests were performed, and dried blood spot samples were collected for further laboratory multiplexed photo-induced electron transfer–polymerase chain reaction (PET-PCR) analysis on positive light microscopy from all patients with fever who attended the Zinder district hospital during the study period.ResultsIn total, 340 dried blood spots were collected and analyzed by PET-PCR. Overall, 73.2% (95% CI, 68.2%–77.9%; 249/340) were positive for Plasmodium genus and species and represented the study population. Plasmodium species proportions were 89.5% (95% CI, 85.1%–93.1%; 223/249) for P falciparum, 38.5% (95% CI, 32.5%–44.9%; 96/249) for P malariae, 10.8% (95% CI, 7.3%–15.4%; 27/249) for P vivax, and 1.6% (95% CI, .4%–4.1%; 4/249) for P ovale. Single infection with Plasmodium species counted for 61.8% (95% CI, 55.5%–67.9%; 154/249), and the mixed infections rate, with at least 2 Plasmodium species, was 38.1% (95% CI, 32.1%–44.5%; 95/249). Single non-falciparum infections represented a rate of 10.0% (95% CI, 6.6%–14.5%; 25/249).ConclusionThis study confirms the first evidence of Plasmodium vivax by PET-PCR in Niger in addition to the other 3 Plasmodium species. These findings underline the need to adapt malaria diagnostic tools and therapeutic management, as well as the training of microscopists, for recognition of non-falciparum plasmodial species circulating in the country. This will better inform the strategies toward malaria control and elimination, as well as the decision making of the health authorities of Niger.

Production of mammalian coccidia in cell culture and subsequent use of in vitro-produced organisms as a source of antigen has been mainly restricted to Toxoplasma gondii (Chernin and Weller, 1957, Journal of Parasitology 43: 33-39; Krahenbuhl et al., 1971, Journal of Parasitology 57: 386-390; Braveny et al., 1978, Tropenmedizin Parasitologie 29: 432-434). We describe here a procedure for the production in vitro of large numbers of first-generation merozoites of Eimeria bovis. Also presented are data concerned with the antigenic similarities of merozoites of E. bovis obtained in vivo or in vitro. Oocysts of E. bovis were collected from the feces of experimentally infected Holstein-Friesian bull calves, sporulated, purified and cleaned as described previously (Fayer and Hammond, 1967, Journal of Protozoology 14: 764-772). Oocysts were stored at 4 C in aqueous 2.5% (w/ v) K2Cr207 for no more than 6 mo prior to use. Sporozoites were excysted from oocysts and separated from oocyst and sporocyst debris immediately before inoculation of cultured cells for in vitro production of first-generation merozoites (Fayer and Hammond, loc. cit.; Speer, 1983, The coccidia in in vitro cultivation of protozoan parasites, J. B. Jensen (ed.). CRC Press, Inc., Boca Raton, Florida, 297 p.; Larsen et al., 1984, Journal of Parasitology 70: 597-601). In vivo-produced first-generation merozoites were obtained from an experimentally infected calf as described previously (Reduker and Speer, 1985, Canadian Journal of Zoology 63: 2478-2480). An established cell line of bovine monocytes (BM) was used as a source of host cells for cultivation of first-generation merozoites. The source and characteristics of this cell line, culture medium (CM), and the ability of BM to support penetration and development of E. bovis have been described previously (Speer et al., 1985, Infection and Immunity 50: 566-571). Each of four 150-cm2 polystyrene Corning tissue culture flasks was inoculated with enough BM to produce a 75% confluent monolayer within 24 to 48 hr. Each flask was then inoculated with 40 ml of CM containing 7.5 x 105 sporozoites, which resulted in an inoculum density of 104 sporozoites/ cm2 BM. Culture flasks were incubated at 38 C in 5% CO2-95% air in a Forma Scientific continuous flow CO2 incubator. When mature meronts and extracellular merozoites were detected with phase-contrast microscopy, the CM containing free merozoites was removed daily and replaced with fresh CM. Merozoites were harvested from each flask at 1021 days after sporozoite inoculation (DAI). After the culture flask was gently rapped 20 x with the palm of the hand, the medium was rocked back and forth 20 x, then decanted into a sterile 50ml centrifuge tube. Ten ml Hanks' balanced salts solution (calcium and magnesium free, pH 7.4; HBSS) were added to each flask and the process was repeated, after which fresh CM was added to each flask. The harvested suspension, which contained merozoites and some host cells, was pelleted by centrifugation at 200 g for 10 min, resuspended in 2-3 ml HBSS, and then agitated with 8-10 strokes on a motor-driven teflon-coated tissue grinder in order to disrupt any intact mature meronts. Numbers of merozoites harvested each day from each flask were estimated by counting on a hemacytometer, and mean number of merozoites harvested (?+ 1 SD) was calculated. At 21 DAI, the width of each flask was examined by phase-contrast microscopy (x 200) for number of intracellular sporozoites, meronts (immature and mature) and degenerate or ruptured meronts. The relative frequency of each stage was calculated as a percentage of total parasite stages observed. After examination, BM and parasites were removed from each flask (0.35% EDTA in RPMI 1640, 38 C, 15 min), and numbers of merozoites were determined as outlined above. Merozoites obtained from cultures were combined, centrifuged, and disrupted in 2% sodium dodecyl sulfate (SDS), 10% glycerol, 6.25 x 10-2 M Tris (hydroxymethyl) aminomethane, 4%

Plasmodium (Novyella) megaglobularis n. sp. was recorded in the olive sunbird Cyanomitra olivacea, and Plasmodium (Novyella) globularis n. sp. and Haemoproteus (Parahaemoproteus) vacuolatus n. sp. were found in the yellow-whiskered greenbul Andropadus latirostris in rainforests of Ghana and Cameroon. These parasites are described based on the morphology of their blood stages and a segment of the mitochondrial cytochrome b gene, which can be used for molecular identification and diagnosis of these species. Illustrations of blood stages of new species are given, and phylogenetic analysis identifies deoxyribonucleic acid (DNA) lineages closely related to these parasites. Traditional taxonomy of avian pigment-forming haemosporidians of the families Plasmodiidae and Haemoproteidae is discussed based on the recent molecular phylogenies of these parasites. We conclude that further work to increase the number of precise linkages between haemosporidian DNA sequences and their corresponding morphospecies is needed before revising the current classification of haemosporidians. This study emphasises the value of both the polymerase chain reaction and microscopy in the identification of avian haemosporidian parasites.

Plasmodium jefferyi is described as a new species of malaria from the gibbon, Hylobates lar, in Malaysia. In blood-induced infections the parasite runs a mild to moderately severe course. There is a striking level of deep circulation schizogony. The evidence available suggests a tertian periodicity although the possibility of a quotidian cycle cannot be eliminated. P. jefferyi can readily be separated on morphological grounds from the other known species of malaria from this host. It is not infective to the rhesus monkey by the inoculation of parasitized blood. The common gibbon, Hylobates, is found in the jungles of southeast Asia from Indochina west to Assam and south through Malaysia and Indonesia. Three species of plasmodia have been described from gibbons: Plasmodium hylobati Rodhain (1941) from Java; Plasmodium youngi Eyles, Fong, Dunn, Warren, and Sandosham (1964) from Malaya; and Plasmodium eylesi Warren, Bennett, Sandosham, and Coatney (1966) from Malaya. This paper is concerned with the description of a fourth species from Hylobates lar in Malaya which we propose to name Plasmodium jefferyi in honor of our colleague, Dr. G. M. Jeffery, who has made notable contributions to our knowledge of malaria. MATERIALS AND METHODS A juvenile female gibbon, Hylobates lar Linnaeus, obtained in the southern part of the state of Kedah in Malaysia, was made available to us for study in Kuala Lumpur in July 1964. This animal was found infected with malaria. Blood films were stained with Giemsa at pH 7.2. Morphological examination of the parasites was made from thin blood films and parasite densities were determined by the Earle Perez technique. The parasite was studied in the original animal and in three other gibbons infected by the inoculation of parasitized blood. Periodicity was studied by counting growth stages of the parasite in smears of peripheral blood of gibbon No. 32, taken at 4-hr intervals over a period of 7 days. Plasmodium jefferyi sp. n. (Figs. 1-20) Vertebrate host: Hylobates lar. Invertebrate host: Not known. Locality: Southern part of the state of Kedah (Malay states) where cultivated tree crops, priReceived for publication 29 October 1965. * Cytology Section, Laboratory of Parasite Chemotherapy, NIAID, NIH, P.O. Box 190, Chamblee, Georgia. marily rubber, merge with primary and secondary forests. Date of collection of type host: July 1964. Type material: Giemsa-stained blood films will be deposited in the U. S. National Museum. Similar aterials will be added to the collection of the Institute for Medical Research in Kuala Lumpur, Malaysia, and to the collection in the laboratory of Parasite Chemotherapy, NIAID, NIH, Bethesda, Maryland. Description of the erythrocytic stages Young trophozoites (Figs. 2-4). Forms with a single large circular nucleus with a delicate circle of cytoplasm most common. Many parasites with two chromatin masses of equal or slightly unequal size (Fig. 3). Small accessory chromatin masses frequent. Ameboid forms rare. Multiple infections, marginal forms, stippling, and pigment not present. Host cell not enlarged. Older trophozoites (Figs. 5-9). Typically not ameboid. Nucleus usually at apex of a smooth, slightly flattened oval of cytoplasm enclosing a large v cuole. Pigment scarce and dustlike; color indefinite, contributing a grayish cast to the cytopla m (Figs. 8, 9). Host cell not enlarged. Stippling usually absent. Forms with accessory chromatin masses present (Fig. 9). Mature trophozoites (Figs. 10-12). Generally non-ameboid and with a prominent vacuole frequently open on one side (Fig. 12). Cytoplasm i creased in amount and density over younger forms. Pigment moderate in amount; mostly fine but with a few moderately coarse granules (Fig. 12); tending to concentrate at periphery of parasi (Fig . 10, 12). Host cell not distorted but may show slight enlargement. Mature parasites may almost fill the host cell. Stippling present but not prominent (Figs. 10-12). Young schizonts (Figs. 13-16). Cytoplasm more compact than in trophozoites; sometimes with a reddish tinge as the number of nuclear divisions increases. Twoto four-nuclei stages do not fill host cell (Figs. 13, 14). In older forms (six to eight nuclei) parasites fill host cell; stippling concentrated at periphery of cell but maintaining its granular nature. Pigment evenly distributed in moderately coarse granules. Older schizonts (Figs. 17, 18). Almost mature forms extremely scarce. Parasites with 14 to 17 This content downloaded from 207.46.13.128 on Tue, 06 Sep 2016 04:34:07 UTC All use subject to http://about.jstor.org/terms 10 THE JOURNAL OF PARASITOLOGY, VOL. 52, NO. 1, FEBRUARY 1966

Malaria is a parasitic disease caused by protozoan species of the genus Plasmodium and transmitted by female mosquitos of the genus Anopheles and other Culicidae. Most of the parasites of the genus Plasmodium are highly species specific with more than 200 species described affecting different species of mammals, birds, and reptiles. Plasmodium species strictly affecting humans are P. falciparum, P. vivax, P. ovale, and P. malariae. More recently, P. knowlesi and other nonhuman primate plasmodia were found to naturally infect humans. Currently, malaria occurs mostly in poor tropical and subtropical areas of the world, and in many of these countries it is the leading cause of illness and death. For more than 100 y, animal models, have played a major role in our understanding of malaria biology. Avian Plasmodium species were the first to be used as models to study human malaria. Malaria parasite biology and immunity were first studied using mainly P. gallinaceum and P. relictum. Rodent malarias, particularly P. berghei and P. yoelii, have been used extensively as models to study malaria in mammals. Several species of Plasmodium from nonhuman primates have been used as surrogate models to study human malaria immunology, pathogenesis, candidate vaccines, and treatments. Plasmodium cynomolgi, P. simiovale, and P. fieldi are important models for studying malaria produced by P. vivax and P. ovale, while P. coatneyi is used as a model for study- ing severe malaria. Other nonhuman primate malarias used in research are P. fragile, P. inui, P. knowlesi, P. simium, and P. brasilianum. Very few nonhuman primate species can develop an infection with human malarias. Macaques in general are resistant to infection with P. falciparum, P. vivax, P. malariae, and P. ovale. Only apes and a few species of New World monkeys can support infection with human malarias. Herein we review the most common, and some less common, avian, reptile, and mammal plasmodia species used as models to study human malaria.

The origin and diversification of the merozoite surface protein 3 (msp3) multi-gene family in Plasmodium vivax and related parasites

Malaria is an important public health problem, with about 219 million cases, which account for 435 thousand deaths of children in Africa in 2017. The infection is transmitted by female anopheles mosquito, including Plasmodium species pathogen for human. In Turkey, no domestic cases have been reported; however, according to Annual Health Statistics, 214 imported cases were reported in 2017. Although P. vivax exactly was reported in previous years, imported Plasmodium falciparum (P. falciparum) cases have increased in the last few years. Herein, we report a case of a 41-year-old male patient who returned two weeks ago from a one-week African journey. A limited number of different blood stages of the parasite (mature trophozoite, young and mature schizont) have been seen in the examination of the peripheral smear; however, the gametocyte stage was not seen. In the present case, detecting mature stages beside the early forms at the peripheral smear could not eliminate the probability of P. falciparum. To confirm the diagnosis and regulate the treatment protocol, molecular methods were employed to differentiate the potential mixture of infection. In this case study, we propose how to approach an uncertain case of severe falciparum malaria or mixture of malaria infection combined with another Plasmodium species, as a result of limited number of different blood stages of the infection at the peripheral smear.

Simple SummaryHaemoproteus parasites are cosmopolitan bird pathogens belonging to the order Haemosporida (Apicomplexa). A majority of the described species are transmitted by Culicoides biting midges, which inject infective stages (sporozoites) in birds during blood meals. The sporozoites initiate tissue merogony, resulting in numerous merozoites, part of which penetrate red blood cells and produce blood stages (gametocytes), which are infective for vectors. The blood stages of Haemoproteus parasites have been relatively well-investigated, although tissue stages and patterns of their development remain unidentified in the majority of Haemoproteus species. Nevertheless, they often damage various organs which makes them important for bird health. This study contributes new knowledge about tissue merogony of Haemoproteus attenuatus, which parasitize birds of the Muscicapidae. Naturally infected European robins Erithacus rubecula were caught in Lithuania during autumnal migration. Parasites were identified using morphological features of gametocytes and DNA sequence analysis. Organs of infected birds were examined using histological methods. Tissue stages (meronts) were present only in the lungs, where they were numerous and markedly varied in shape, size and maturation stage. Description of meronts was provided and molecular phylogenetic analysis identified closely related lineages that could present similar exo-erythrocytic development in lungs. Lung damage caused by meronts of H. attenuatus and closely related lineages is worth attention due to their possible implications on a bird’s health.Haemoproteus species are widespread avian blood parasites belonging to Haemoproteidae (Haemosporida). Blood stages of these pathogens have been relatively well-investigated, though exo-erythrocytic (tissue) stages remain unidentified for the majority of species. However, recent histopathological studies show that haemoproteins markedly affect bird organs during tissue merogony. This study investigated the exo-erythrocytic development of Haemoproteus (Parahaemoproteus) attenuatus (lineage hROBIN1), the common parasite of flycatchers (Muscicapidae). Naturally infected European robins Erithacus rubecula were examined. Parasite species and lineage were identified using microscopic examination of blood stages and DNA sequence analysis. Parasitaemia intensity varied between 0.8 and 26.5% in seven host individuals. Organs of infected birds were collected and processed for histological examination. Tissues stages (meronts) were seen in six birds and were present only in the lungs. The parasites were usually located in groups and were at different stages of maturation, indicating asynchronous exo-erythrocytic development. In most parasitized individuals, 100 meronts were observed in 1 cm2 section of lungs. The largest meronts reached 108 µm in length. Mature meronts contained numerous roundish merozoites of approximately 0.8 µm in diameter. Megalomeronts were not observed. Massive merogony and resulting damage of lungs is a characteristic feature during H. attenuatus infections and might occur in related parasite lineages, causing haemoproteosis.

The erythrocytic cycle of Plasmodium falciparum presents a particularity in relation to other Plasmodium species that infect man. Mature trophozoites and schizonts are sequestered from the peripheral circulation due to adhesion of infected erythrocytes to host endothelial cells. Modifications in the surface of infected erythrocytes, termed knobs, seem to facilitate adhesion to endothelium and other erythrocytes. Adhesion provides better maturation in the microaerophilic venous atmosphere and allows the parasite to escape clearance by the spleen which recognizes the erythrocytes loss of deformability. Adhesion to the endothelium, or cytoadherence, has an important role in the pathogenicity of the disease, causing occlusion of small vessels and contributing to failure of many organs. Cytoadherence can also describe adhesion of infected erythrocytes to uninfected erythrocytes, a phenomenon widely known as rosetting. Clinical aspects of severe malaria, as well as the host receptors and parasite ligands involved in cytoadherence and rosetting, are reviewed here. The erythrocyte membrane protein 1 of P. falciparum (PfEMP1) appears to be the principal adhesive ligand of infected erythrocytes and will be discussed in more detail. Understanding the role of host receptors and parasite ligands in the development of different clinical syndromes is urgently needed to identify vaccination targets in order to decrease the mortality rates of this disease.