Helminths of saiga antelope in Kazakhstan: implications for conservation and livestock production

Saiga antelope (Saiga tatarica) graze extensively on livestock pasture, potentially enabling transmission of a wide range of parasitic helminths between saigas and domestic ruminants. Thirty-six of the 38 species of helminth that have been found in saigas in Kazakhstan in the past have been found also in domestic livestock. We examined 133 saigas culled for meat in autumn 1997, and found three species of cestode and 12 nematodes (nine in the abomasum), but no trematodes or lungworms. The most abundant species were Marshallagia marshalli, Marshallagia mongolica, and Nematodirus gazellae in the abomasum, Nematodirus gazellae in the small intestine, and Skrjabinema ovis in the large intestine. There was no clear relationship between intensities of abomasal nematodes and body condition. Age-intensity patterns differed between species: N. gazellae intensities were highest in saigas around 2-3 yr old, and declined in older animals, whereas the intensity of Marshallagia spp. rose asymptotically with age. Fecal egg density was directly proportional to adult worm intensity across ages for Marshallagia spp., but only in young animals for N. gazellae. There was no evidence that helminths, at the intensities observed, adversely affect saiga populations. The host range of many of the parasites found is broad, and transmission between saigas and livestock in both directions might become important to agriculture and conservation as livestock numbers recover. Simplified sampling techniques used in this study, and statistical analysis based on bootstrapping, could prove useful in other parasitologic surveys of wildlife in remote areas.     

The steppe species of gastrointestinal nematodes of small ruminants, with a focus on Marshallagia: climate as a key determinant

We intended to relate the geographic distribution of ruminant gastrointestinal nematodes in relation to steppe climate (and vegetation). Data are either from literature or from newly acquired/available results. Simple or more sophisticated meteorological indices were used to characterize the climate. Regression analyses were used to correlate climatic factors and presence of endoparasites from steppe areas. The distribution of one (Marshallagia) out of five endoparasite genera was concentrated mostly in steppic areas whereas other species were found also in other areas. In wild hosts the distribution of Marshallagia was much larger from Sptizberg to New World (northern territories in Canada or extreme south of America). In domestic small ruminants the presence of Marshallagia was identified more frequently and constantly in the area of original domestication and its early diffusion (from Northern Africa to Kashmir, Caucasia). The distribution of this parasite was correlated to low rainfalls which were not the case for all other endoparasites. After host switch (reindeer or south America camelids), it has expanded in other climatic areas, either colder or dryer.     

DNA evidence that Marshallagia marshalli Ransom, 1907 and M. occidentalis Ransom, 1907 (Nematoda: Ostertagiinae) from Svalbard reindeer are conspecific

The gastro-intestinal parasitic nematodes of ruminants Marshallagia marshalli and M. occidentalis are morphs of a single species according to indirect evidence. In this study, their taxonomic status and molecular identification were assessed more directly in isolates from the abomasal nematode community of Svalbard reindeer using genetic data. DNA sequences of the first and second internal transcribed spacers of nuclear ribosomal RNA genes were obtained from individual nematodes by the polymerase chain reaction (PCR). Both taxa contained virtually identical sequences of each ITS and shared most of the polymorphisms detected. A PCR assay based on ITS-2 sequences previously developed to identify M. marshalli and Ostertagia gruehneri, the second common species in this community, gave identical results for M. marshalli andM. occidentalis. Genetic data thus confirmed that M. marshalli andM. occidentalis are conspecific.     

Die Halsäste des Nervus vagus beim Alpaka,Lama guanicoe pacos (Linné 1758)

Demmel, U. 1980. Die Halsäste des Nervus vagus beim Alpaka, Lama guanicoe pacos (Linné 1758). [The branches of the vagus nerve in the neck of Alpaka, Lama guanicoe pacos (Linné 1758).] (Anatomisches Institut der Universität Köln, Bundesrepublik Deutschland.) — Acta zool. (Stockh.) 61(3): 141–146. Dissections of two newborn and two adult alpacas have shown: that the trapezius musculature of either side is supplied by branches of seven cervical spinal nerves and not by the external ramus of truncus nervi accessorii as in mammals in general; that the nerves which innervate the inner laryngic muscles as well as the mucous membrane of the lower part of the larynx are given off from the main trunk of the vagus nerve just outside the jugular foramen; that a nerve corresponding to the n. laryngeus recurrens of other mammals is absent. It is concluded that the lack of recurvation of the inferior laryngic nerve and the absence of the spinal part of the accessory nerve are character states of tylopod artiodactyls.     

Disease transmission in an extreme environment: nematode parasites infect reindeer during the Arctic winter

Parasitic nematodes are found in almost all wild vertebrate populations but few studies have investigated these host-parasite relationships in the wild. For parasites with free-living stages, the external environment has a major influence on life-history traits, and development and survival is generally low at sub-zero temperatures. For reindeer that inhabit the high Arctic archipelago of Svalbard, parasite transmission is expected to occur in the summer, due to the extreme environmental conditions and the reduced food intake by the host in winter. Here we show experimentally that, contrary to most parasitic nematodes, Marshallagia marshalli of Svalbard reindeer is transmitted during the Arctic winter. Winter transmission was demonstrated by removing parasites in the autumn, using a novel delayed-release anthelmintic bolus, and estimating re-infection rates in reindeer sampled in October, February and April. Larval stages of nematodes were identified using molecular tools, whereas adult stages were identified using microscopy. The abundance of M. marshalli adult worms and L4s increased significantly from October to April, indicating that reindeer were being infected with L3s from the pasture throughout the winter. To our knowledge, this study is the first to experimentally demonstrate over-winter transmission of a gastro-intestinal nematode parasite in a wild animal. Potential mechanisms associated with this unusual transmission strategy are discussed in light of our knowledge of the life-history traits of this parasite.     

Protein kinases as targets for antimalarial intervention: Kinomics, structure-based design, transmission-blockade, and targeting host cell enzymes

The surge of interest in protein kinases as targets for chemotherapeutic intervention in a number of diseases such as cancer and neurodegenerative disorders has stimulated research aimed at determining whether enzymes of this class might also be considered as targets in the context of diseases caused by parasitic protists. Here, we present an overview of recent developments in this field, concentrating (i) on the benefits gained from the availability of genomic databases for a number of parasitic protozoa, (ii) on the emerging field of structure-aided design of inhibitors targeting protein kinases of parasitic protists, (iii) on the concept known as transmission-blockade, whereby kinases implicated in the development of the parasite in their arthropod vector might be targeted to interfere with disease transmission, and (iv) on the possibility of controlling parasitic diseases through the inhibition of host cell protein kinases that are required for the establishment of infection by the parasites.     

Identification by polymerase chain reaction (PCR) of Marshallagia marshalli and Ostertagia gruehneri from Svalbard reindeer

A polymerase chain reaction (PCR) assay to identify two common abomasal nematodes Marshallagia marshalli and Ostertagia gruehneri of Svalbard reindeer was developed. Species-specific PCR primers were designed from internal transcribed spacer (ITS)-2 sequences of rDNA and validated using morphologically identified adult male and female nematodes. Using the species-specific primers, a 110 bp fragment was amplified from M. marshalli and its minor morph Marshallagia occidentalis and a 149 bp fragment was amplified from Ostertagia gruehneri and its minor morph Ostertagia arctica. No PCR products were amplified from the third rare species, Teladorsagia circumcincta, or DNA from the reindeer host. The assay provides a useful tool to estimate species composition for both sexes in this nematode community.     

Karyotypes of parasitic Hymenoptera: Diversity, evolution and taxonomic significance

Haploid chromosome numbers (n) of parasitic Hymenoptera (= traditional Parasitica + Chrysidoidea) vary from 2 to 23. However, this range can be subdivided into three intervals with n= 14–23 (less derived parasitic wasps, e.g., some Ichneumonidae and Braconidae as well as Gasteruptiidae), 8–13 (many other parasitic Hymenoptera) and 2–7 (Dryinidae, the majority of Chalcidoidea and some advanced Braconidae, e.g. Aphidiinae). The symmetric karyotype with a relatively high chromosome number (n= 14–17) and the prevalence of biarmed chromosomes must be considered as a groundplan feature of parasitic Hymenoptera. Independent reductions of chromosome numbers (n≤ 10–11) occurred in some groups of the superfamily Ichneumonoidea as well as in the common ancestor of the Proctotrupoidea sensu lato, Ceraphronoidea, Cynipoidea and Chalcidoidea. Further multiple decreases in chromosome numbers (n≤ 4–6) took place in some Braconidae, various lineages of the superfamily Chalcidoidea as well as in the family Dryinidae. Two main trends prevailed in the karyotype evolution of parasitic wasps: the reduction of chromosome numbers (mainly due to tandem fusions and less frequently due to centric ones) and karyotypic dissymmetrization (through an increase in size differentiation of chromosomes and/or in the share of acrocentrics in a chromosome set). Although karyotypic features of parasitic Hymenoptera can be used for solving taxonomic problems at various levels, this method is the most effective at the species level.     

Inteins, introns, and homing endonucleases: recent revelations about the life cycle of parasitic genetic elements

Self splicing introns and inteins that rely on a homing endonuclease for propagation are parasitic genetic elements. Their life-cycle and evolutionary fate has been described through the homing cycle. According to this model the homing endonuclease is selected for function only during the spreading phase of the parasite. This phase ends when the parasitic element is fixed in the population. Upon fixation the homing endonuclease is no longer under selection, and its activity is lost through random processes. Recent analyses of these parasitic elements with functional homing endonucleases suggest that this model in its most simple form is not always applicable. Apparently, functioning homing endonuclease can persist over long evolutionary times in populations and species that are thought to be asexual or nearly asexual. Here we review these recent findings and discuss their implications. Reasons for the long-term persistence of a functional homing endonuclease include: More recombination (sexual and as a result of gene transfer) than previously assumed for these organisms; complex population structures that prevent the element from being fixed; a balance between active spreading of the homing endonuclease and a decrease in fitness caused by the parasite in the host organism; or a function of the homing endonuclease that increases the fitness of the host organism and results in purifying selection for the homing endonuclease activity, even after fixation in a local population. In the future, more detailed studies of the population dynamics of the activity and regulation of homing endonucleases are needed to decide between these possibilities, and to determine their relative contributions to the long term survival of parasitic genes within a population. Two outstanding publications on the amoeba Naegleria group I intron (Wikmark et al. BMC Evol Biol 2006, 6: 39) and the PRP8 inteins in ascomycetes (Butler et al. BMC Evol Biol 2006, 6: 42) provide important stepping stones towards integrated studies on how these parasitic elements evolve through time together with, or despite, their hosts.     

Biomorphology of gastrointestinal nematodes of small ruminants

Under the term gastrointestinal nematodes are included numerous parasites species of livestock belonging to the families Strongyloididae (Strongyloides), Strongylidae (Chabertia, Oesophagostomum) Trichostrongylidae (Trichostrongylus, Ostertagia, Teladorsagia, Cooperia, Marshallagia), Molineidae (Nematodirus), Ancylostomatidae (Bunostomum) and Trichuridae (Trichuris). This paper reviews the biomorphology aspects of these parasites as well as the controversy by the taxonomists in the classifications.     

Seasonal dynamics of the tick Haemaphysalis tibetensis in the Tibetan Plateau,China

The tick Haemaphysalis tibetensis (Acari: Ixodidae) Hoogstraal is an important arthropod vector widespread in the Qinghai‐Tibet Plateau, and knowledge of its seasonal dynamics is still poor. The current study investigated the seasonal dynamics of the parasitic and non‐parasitic H. tibetensis over a 2‐year period from March 2014 to February 2016 in the Tibetan Plateau, China. During this timeframe, non‐parasitic ticks were collected weekly by flag‐dragging in grassland and shrubland areas, and parasitic ticks were removed weekly from selected sheep. Plateau pikas were captured using traps and examined for immature ticks between May to September 2014. Results suggest that non‐parasitic H. tibetensis were mainly distributed in the grassland, and the parasitic adults and nymphs were found mostly on sheep. Larvae were usually found on Plateau pikas and the prevalence of infestation and mean parasitic intensity were 72.1 and 1.81%, respectively. Adults were observed from March to July with the major peak occurring in mid‐April. Nymphs were found from March to August and reached a peak in late June. Larvae were collected from April to September, and their numbers peaked in late May. In the parasitic and non‐parasitic period, the overall sex ratio of males to females was 1.62 and 1.30, respectively. Results show that H. tibetensis can complete one generation per year, with a population overlap between stages over the spring‐summer months. These findings provide additional information on the biology and ecology of H. tibetensis as well as insights on its control in the environment and on sheep.     

Gastrointestinal nematodes of wild sheep (Ovis orientalis) from Iran.

A total of 250 wild sheep (Ovis orientalis) from different national parks and protected regions of Iran were examined for gastrointestinal nematodes at necropsy. Twenty five species of nematodes were found. Marshallagia marshalli, Ostertagia spp; Nematodirus spp; and Skrjabinema ovis were the most prevalent. Although all the species found are recorded from wild sheep for the first time in Iran, 88% were reported previously from domestic sheep. New host and distribution records for Nematodirus davtiani, N. gazellae and Nematodirella longissimespiculata were established during the present study.     

东方胎球蚧的生物学特性及防治

东方胎球蚧在长春年生1代,以2龄若虫固着在二年生枝条的芽腋、分枝和不光滑处群集越冬。3月末至4月初开始活动为害。越冬若虫为害盛期为4月下旬至6月初。此时虫体明显膨大。5月下旬至6月上旬为成虫期和卵盛期。7月初起当年若虫自介壳下爬出分散转移到叶片、叶炳和嫩枝上为害,老虫共2龄。调查未见雄虫,均行孤雌生殖。主要天敌有黑缘红飘虫和一种寄生性小峰。当前生产上可在若虫越冬后为害盛期前和当年若虫出壳分散期。因地制宜地用有机磷或合成菊酯类杀虫剂进行常规喷雾。防治效果均较好。     

A Newly Revised Classification of the Protozoa*

SYNOPSIS The subkingdom Protozoa now includes over 65,000 named species, of which over half are fossil and ～ 10,000 are parasitic. Among living species, this includes ～ 250 parasitic and 11,300 free-living sarcodines (of which ～ 4,600 are foraminiferids); 1.800 parasitic and 5,100 free-living flagellates: ～ 5,600 parasitic “Sporozoa” (including Apicomplexa, Microspora, Myxospora, and Aseetospora); and ～ 2,500 parasitic and 4,700 free-living ciliates. There are undoubtedly thousands more still unmamed. Seven phyla of PROTOZOA are accepted in this classification—SARCOMASTIGOPHORA. LABYRINTHOMORPHA, APICOMPLEXA, MICROSPORA, ASCETOSPORA, MYXOSPORA, and CILIOPHORA. Diagnoses are given for these and for all higher taxa through suborders, and representative genera of each are named. the present scheme is a considerable revision of the Society's 1964 classification, which was prepared at a time when perhaps 48,000 species had been named. It has been necessitated by the acquisition of a great deal of new taxonomic information, much of it through electron microscopy. It is hoped that the present classification incorporates most of the major changes that will be made for some time. and that it will be used for many years by both protozoologists and non-protozoologists.     

Social parasites among African allodapine bees (Hymenoptera,Anthophoridae, Ceratinini)*

Among the numerous nonparasitic allodapine bees there are 11 known species with parasitic or probably parasitic habits. These species live in nests of their close relatives, the female parasite replacing an egg-layer of the host. Seven of the parasitic species are distributed among four otherwise nonparasitic genera, while four species of parasites are placed in three exclusively parasitic genera. The parasites have mostly arisen independently from different nonparasitic forms. There is much convergence among the parasitic forms involving such characters as the flattened or concave face, reduced eyes, reduced mouthparts, reduced wing venation, and reduced pollen-carrying scopa. In the most specialized parasitic genera the mouthparts are so small as to be almost surely useless for obtaining food from flowers. Such bees must feed in the host nest, and are not found on flowers. Their wings must be adequate to take them to a new host nest but the reduced venation and eyes must reflect the reduced locomotary and sensory needs of a bee that does not visit flowers. In this paper a new, presumably parasitic Allodapula is described as is a parasitic Braunsapis, a parasitic Allodape, and a Eucondylops. A previously described Macrogalea is recognized as a parasite for the first time. A new genus and species of parasites Nasutapsis straussorum, allied to Braunsapis, is also described. All these forms are from Africa.     

Mites of the family Cheyletidae (Acari: Prostigmata): phylogeny, distribution, evolution and analysis of parasite-host relationship

A modern system, phylogeny, distribution and host parasite relationships of cheyletid mites (Acari: Prostigmatal Cheyletidae) is shortly discussed. According to the phylogenetic hypothesis proposed by Bochkov and Fain (2001), the family Cheyletidae includes now 15 tribes: Acaropsellini, Bakini, Cheletogenini, Cheletosomatini, Chelonotini, Cheyletiini, Cheyletiellini, Cheyletini, Cheletomorphini, Criokerontini, Metacheyletiini, Niheliini, Ornithocheyletiini, Teinocheylini and one unnamed tribe including the genera Caudacheles and Alliea. The parasitic Cheyletidae were primarily free-living predators, frequently associated with nests of vertebrates. These mites, being predators, have numerous preadaptations to the parasitic mode of life and they possess high ecological plasticity. Therefore it was quite easy for these mites to adapt to parasitism on the vertebrates. According to our phylogenetical hypothesis, the parasitism on vertebrates has arisen independently in several phylogenetic lines of the cheyletids associated with nests of vertebrates. Such transition from nest predation to true parasitism probably occurred repeatedly and at different times. The cheyletid mites are more widely represented on birds than on mammals. Possibly, it is in relation with a more early origin of parasitism in the cheyletids associated with bird nests than in the cheyletids associated with mammal nests. An independent origin of the parasitism in many different cheyletid phyletic lines, arisen significantly later than the origin of such a parasitic group as myobiid mites, is probably the main reason, which could explain the recent mosaic distribution of the Cheyletidae among the mammalian taxa. Parasitic associations between cheyletids and vertebrates are more common than the associations between these mites and the invertebrates. In the invertebrates, these associations are generally restricted to a phoresy. The zoogeographical analysis showed that this family as whole is characterised by the extremely low endemisms. The most part of the free-living cheyletid mites are associated with Holarctic region (87%) and, therefore, this family, probably, originated there.     

Reproduction of the trematode Echinostoma caproni parthenites (Digenea: Echinostomatidae)

Dynamics of the reproduction in the trematode Echinostoma caproni parthenites (Echinostomatidae) was observed. Early laying and maturation of the generative cells are for the first time shown to be characteristic for all parthenogenetic generations. Really the process of reproduction had been finishing to the beginning of the generating of new age by parthenites. Mother sporocysts, as well as redia of different generations, in fact stop producing new generative cells with the beginning of the generating of new age, and assume the function of a brood pouch. This feature was considered previously as peculiar mainly to mother sporocysts. Data on the autotomy of the anterior body end in mother sporocysts are verified. In our opinion, these data are an evidence of an early manifestation of the evolutionary trend to the morpho-functional regress and disintegration of the parasitic stage of mother sporocyst.     

Dynamic organization of microtubules and microtubule-organizing centers during the sexual phase of a parasitic protozoan, Lecudina tuzetae (Gregarine, Apicomplexa)

Lecudina tuzetae is a parasitic protozoan (Gregarine, Apicomplexa) living in the intestine of a marine polychaete annelid, Nereis diversicolor. Using electron and fluorescence microscopy, we have characterized the dynamic changes in microtubule organization during the sexual phase of the life cycle. The gametocyst excreted from the host worm into seawater consists of two (one male and one female) gamonts in which cortical microtubule arrays are discernible. Each gamont undergoes multiple nuclear divisions without cytokinesis, resulting in the formation of large multinucleate haploid cells. After cellularization, approximately 1000 individual gametes are produced from each gamont within 24 h. Female gametes are spherical and contain interphase cytoplasmic microtubule arrays emanating from a gamma-tubulin-containing site. In male gametes, both interphase microtubules and a flagellum with "6 + 0" axonemal microtubules extend from the same microtubule-organizing site. At the beginning of spore formation, each zygote secretes a wall to form a sporocyst. Following meiotic and mitotic divisions, each sporocyst gives rise to eight haploid cells that ultimately differentiate into sporozoites. The ovoid shaped sporocyst is asymmetric and forms at least two distinctive microtubule arrays: spindle microtubules and microtubule bundles originating from the protruding apical end corresponding to the dehiscence pole of the sporocyst. Because antibodies raised against mammalian centrosome components, such as gamma-tubulin, pericentrin, Cep135, and mitosis-specific phosphoproteins, react strongly with the microtubule-nucleating sites of Lecudina, this protozoan is likely to share common centrosomal antigens with higher eukaryotes.