Identification of Nematodirus species (Nematoda: Molineidae) from wild ruminants in Italy using ribosomal DNA markers

The sequence of the second internal transcribed spacer of ribosomal DNA was determined for four species of Nematodirus (Nematodirus rupicaprae, Nematodirus oiratianus, Nematodirus davtiani alpinus and Nematodirus europaeus) from roe deer or alpine chamois. The second internal transcribed spacer of the four species varied in length from 228 to 236 bp, and the G + C contents ranged from 41 to 44%. While no intraspecific sequence variation was detected among multiple samples representing three of the taxa, sequence differences of 5.9-9.7% were detected among the four species, Nematodirus davtiani alpinus and N. rupicaprae were genetically most similar (94.1%), followed by N. oiratianus, N. europaeus and N. rupicaprae (91.1-91.5%), whereas N. oiratianus was genetically most different from N. davtiani alpinus. The interspecific sequence differences were exploited for the delineation of the four species by PCR-based restriction fragment length polymorphism (using two enzymes) and single-strand conformation polymorphism. The results have implications for diagnosis, epidemiology and for studying the systematics of the Nematodirinae.     

A survey of the gastrointestinal nematodes of Spanish ibex (Capra pyrenaica) in a high mountain habitat

We analyzed the content of the abomasum (n = 79) and small intestine (n = 83) of Spanish ibex from Sierra Nevada Natural Park, southern Spain. Fifteen species of trichostrongylid nematodes were identified, 4 of which were found for the first time in this host, i.e., Nematodirus fillicollis, N. oiratianus, Ostertagia lyrata, and O. ostertagi. Teladorsagia circumcincta and Marshallagia marshalli were the most abundant abomasal species, whereas N. abnormalis, N. davtiani, and N. oiratianus were dominant in the small intestine. Counts of both abomasal and intestinal nematodes were generally low (year-round-median = 292 and 94 worms, respectively), and significantly lower numbers of M. marshalli, N. davtiani, and N. oiratianus were found in summer. No sex-related differences in helminth abundance were found, but young ibex harbored significantly more N. davtiani and N. oiratianus than adults. The presence of scabies was not related to increased nematode counts.     

The Dynamics, Prevalence and Impact of Nematode Infections in Organically Raised Sheep in Sweden

A three-year survey (1997–99) was carried out on organically reared sheep flocks throughout Sweden. The aim was to determine the prevalence and intensity of nematode infections and to establish relationships between sheep management practices and parasite infections. Faecal samples from ewes and lambs were collected from 152 organic flocks around lambing-time and during the grazing-period for analysis. Results were compared with the different management practices that farmers use to prevent parasitism in their flocks. A high proportion of the flocks was infected with nematodes. The most prevalent species were Haemonchus contortus, Teladorsagia circumeincta, Trichostrongylus axei, T. colubriformis and Chabertia ovina and infections progressively increased during summer in lambs grazing on permanent pastures. Severity of parasitic infection in lambs was highly dependent on egg output from the ewes. H. contortus was found in 37% of the flocks, even at latitudes approximating the Polar Circle. Nematodirus battus was recorded for the first time in Sweden during the course of this study. Lambs turned out onto permanent pasture showed higher nematode faecal egg counts (epg) than lambs that had grazed on pastures, which had not carried sheep the previous year. This beneficial effect of lambs grazing non-infected pastures persisted if the ewes were treated with an anthelmintic before turn-out and if the lambs were kept on pastures of low infectivity after weaning. In lambs, the prevalence and the magnitude of their egg counts were higher during autumn in flocks where lambs were slaughtered after 8 months of age, compared with flocks where all lambs were slaughtered before this age. These results will be used in providing advice to farmers of ways to modify their flock management in order to minimise the use of anthelmintics, but at the same time efficiently produce prime lambs.     

The fate of multiple doses of infective larvae of Nematodirus battus in 8-month-old lambs and their effect on intestinal enzyme activity

Mapes C.J. and Coop R.L. 1973. The fate of multiple doses of infective larvae of Nematodirus battus in 8-month-old lambs and their effect on intestinal enzyme activity. International Journal for Parasitology3: 363–370. The fate of five daily doses of 60,000 infective larvae of Nematodirus battus was studied in 8-month-old lambs. On 18, 26 and 34 days after the last larval dose 4.0, 3.3 and 1.0 per cent of the total infective dose was recovered. Approximately 50 per cent of the worms recovered on these days were fourth-stage larvae. It is suggested that L5 and adult stages were preferentially lost from the hosts and that male worms were developing at a faster rate than the females. The populations of N. battus were smaller, contained higher proportions of fourth-stage larvae and shorter L5 and adult worms than those developing from similar infective doses in 3-month-old lambs. A transient decrease in alkaline phosphatase and maltase levels was found in the mucosa of the small intestine and was compared with the marked and persistent changes in mucosal enzyme activities found with similar infective doses in 3-month-old hosts.     

The fate of large infective doses of Nematodirus battus in young lambs

Mapes C.J., Coop R.L. and Angus K.W. 1973. The fate of large infective doses of Nematodirus battus in young lambs. International Journal for Parasitology3: 339–347. The fate of 300,000 and 5 × 60,000 infective larvae of Nematodirus battus during the 2–3 weeks after patency was studied in 3-month-old lambs. The proportions of the infective doses recovered after 18, 26 and 34 days were 37, 6 and 3.5 per cent in the single dose and 29,12 and 4.7 in the multiple dose groups. Fifth-stage larvae and adults, especially females, were preferentially lost from the hosts. The numbers of worms present and the percentage of fourth-stage larvae present were similar in both the single and multiple dose groups.     

Effect of genetic type, lactation and management on helminth infection of ewes in an intensive grazing system on irrigated pasture.

A survey of helminth infection was conducted in a flock of 290 ewes distributed into Romanov (R), Merinos d'Arles (M) and Romanov x Merinos (R x M) genetic types, grazing irrigated pasture in the south of France. Faecal egg and larval counts were done seven times per year from 1981 to 1984 on homogeneous groups of ewes and then individually once to four times every autumn from 1985 to 1988. Helminth fauna was diverse and more abundant during autumn. High levels of strongyle infection occurred in the ewes that remained on the same irrigated pastures during summer. Moving to Alpian pastures during the summer lowered autumnal infection. Significant differences between genotypes in intensity of infection were observed in the order R > R x M > M for strongyles (Teladorsagia circumcincta and/or Trichostrongylus vitrinus, Chabertia ovina and/or Oesophagostomum venulosum, Nematodirus spp.), Moniezia spp. and Dictyocaulus filaria. The hierarchy was reversed for Fasciola hepatica infection and not consistent from one year to another for protostrongylid infections. The effect of lactation intensity on the postparturient rise was studied by equilibrating number of ewes according to reproductive status (zero, one or two lambs in lactation). Merino ewes with two lambs in lactation, as well as primiparous Romanov ewes, had significantly higher strongyle infections than the others. The repeatabilities of the larval and egg counts between the four trial years were 0.24, 0.23 and 0.16, respectively, for protostrongyles, Nematodirus and strongyles, with higher intra-annual values for protostrongyles and inconsistently significant results for strongyles due to the presence of several species.     

Nematodirus battus 50 years on--a realistic vaccine candidate?

It has been 50 years since the parasitic nematode of lambs, Nematodirus battus, was first described. This parasite has several interesting features; in particular, it induces a rapid, protective immune response in infected young lambs (< 3 months of age), which is not observed if lambs are infected with other trichostrongyle nematodes. Indeed, protection against most gastrointestinal nematodes only develops once lambs are over five to six months old. In this article I suggest that N. battus offers an opportunity to improve our understanding of protective immune responses in young lambs, and could therefore hold a key to rational anti-nematode vaccine developments, based on natural antigens.     

Distribution of nematode parasites of the digestive system in sheep (Ovis aries) and goats (Capra hircus) of the Piedmontese and Valdostano Alpine arc

A survey, carried out on gastro-intestinal nematodes of sheep and goats of Piemonte and of Valle d'Aosta (87 sheep and 12 goats) has shown the presence of the following species in sheep, Bunostomum trigonocephalum, Chabertia ovina, Cooperia curticei, Haemonchus contortus, Marshallagia marshalli, Nematodirus abnormalis, Nematodirus filicollis, Nematodirus helvetianus, Nematodirus spathiger, Oesophagostomum venulosum, Ostertagia circumcincta, Ostertagia lyrata, Ostertagia trifurcata, Skrjabinema ovis, Trichostrongylus axei, Trichostronglus colubriformis, Trichostronglus vitrinus, Trichuris ovis and Trichuris skrjabini; in goats, Bunostomum trigonocephalum, Chabertia ovina, Haemonchus contortus, Nematodirus filicollis, Nematodirus helvetianus, Oesophagostomum venulosum, Ostertagia circumcincta, Ostertagia ostertagi, Ostertagia trifurcata, Trichostrongylus axei, Trichostrongylus colubriformis and Trichostrongylus vitrinus. The percentage of each species in the two host is given in the text table.     

The effect of large doses of Nematodirus battus on the histology and biochemistry of the small intestine of lambs

Coop R.L., Angus K.W. and Mapes C.J. 1973. The effect of large doses of Nematodirus battus on the histology and biochemistry of the small intestine of lambs. International Journal for Parasitology3: 349–361. Large single and multiple doses of Nematodirus battus alter the structure of the small intestine, producing a low flattened, convoluted type of mucosa with extensive cellular infiltration of the lamina propria. The brush borders of the epithelial cells on the surface of the villi are narrow and the microvilli sparse and distorted.There is a reduction in alkaline phosphatase and disaccharidase activity in the mucosa of infected lambs, whereas dipeptidase activity is unaffected. The changes in enzyme activity are thought to arise from damage to mature epithelial cells on the villi.Alkaline phosphatase and disaccharidase activity in the mueosa of lambs killed 18 days after infection is correlated with the dry matter content of the faeces.     

Nippostrongylus brasiliensis and Nematodirus battus: Changes in numbers and weight during the course of infection

Nematodirus battus has been shown to be subject to a “self-cure” mechanism when lambs 6 weeks of age are infected with 60,000 larvae. It is proposed that this self-cure phenomenon is an immune response similar to that which occurs in rats infected with Nippostrongylus brasiliensis. Changes in the weight of adult Nematodirus sp. and Nippostrongylus sp. occur over the period of an infection in their hosts. Females of both species from high-dose infections increased in weight up to that time postinfection where most adult worms were present, then decreased in weight with the onset of rejection from the host. Male Nematodirus sp. showed a similar pattern of weight change to that of females but male Nippostrongylus sp. maintained a steady weight throughout the infection. The consequences of these changes in weight are discussed with relevance to expression of enzyme activities of the nematodes on a weight of individual nematode basis.     

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.     

Vaccination of young lambs against infection with Nematodirus battus using gamma irradiated larvae

Helminthologically naIve 6-week-old Suffolk lambs were given 1-3 doses of 20000 gamma-irradiated infective larvae (L3) of the nematode Nematodirus battus at weekly intervals. Following an anthelmintic drench they were challenged with 50000 viable L3 at 10 weeks of age. Nematode worm burdens 14 days post-challenge showed a significant (P<0.01) 66% reduction in the single vaccine dose group. The two and three dose groups had mean worm burdens which were 30 and 42% lower than controls, respectively, although these were not statistically significant. There was little measurable stimulation of the immune system in the vaccinated lambs, suggesting that the repeatedly dosed animals may have developed immunological unresponsiveness to the parasite.     

Efficacy of p-Toluoyl chloride phenylhydrazone against gastrointestinal helminths in ovines.

A new anthelmintic candidate, p-toluoyl chloride phenlylhydrazone, was administered to lambs in a paste formulation. The efficacy of this drug was determined at dose rates of 20, 30, 40, and 50 mg of active ingredient per kilogram of body weight. Helminths expelled by these dosages included Haemonchus contortus, Ostertagia circumcicta, Trichostrongylus colubriformis, T. axei, Nematodirus filicollis, Cooperia curticei, Strongyloides papillosus, Oesophagostomum columbianum, Bunostomum trigoncephalum, Chabertia ovina, Moniezia expansa, and M. benedeni.     

Observations on crystals found in the intestine of Nematodirus battus during the development of immunity to this nematode in lambs.

Lambs which were given 60000 infective larvae of Nematodirus battus progressively threw off adult nematodes from day 20 onwards. Large, hexagonal crystals appeared in the intestine of the adult nematode at about this time and caused blockage of the intestinal-rectal or -cloacal junction. Lambs which were given 1000-2000 infective larvae did not throw off the infection, and adult nematodes from lambs which had been infected for up to 74 days did not contain these crystals. Chemical, histochemical and x-ray microanalysis tests on the crystals indicated that they are lipoprotein in composition. The crystals arise within the lumen of the nematode and appear to be associated with the development of immunity to this nematode in lambs.     

Metazoan-protozoan parasite co-infections and host body weight in St Kilda Soay sheep

For hundreds of years, the unmanaged Soay sheep population on St Kilda has survived despite enduring presumably deleterious co-infections of helminth, protozoan and arthropod parasites and intermittent periods of starvation. Important parasite taxa in young Soay sheep are strongyles (Trichostrongylus axei, Trichostrongylus vitrinus and Teladorsagia circumcincta), coccidia (11 Eimeria species) and keds (Melophagus ovinus) and in older animals, Teladorsagia circumcincta. In this research, associations between the intensity of different parasite taxa were investigated. Secondly, the intensities of different parasite taxa were tested for associations with variation in host weight, which is itself a determinant of over-winter survival in the host population. In lambs, the intensity of strongyle eggs was positively correlated with that of Nematodirus spp. eggs, while in yearlings and adults strongyle eggs and coccidia oocysts were positively correlated. In lambs and yearlings, of the parasite taxa tested, only strongyle eggs were significantly and negatively associated with host weight. However, in adult hosts, strongyles and coccidia were independently and negatively associated with host weight. These results are consistent with the idea that strongyles and coccidia are exerting independent selection on Soay sheep.     

Relationships of Nematodirus species and Nematodirus battus isolates (Nematoda: Trichostrongyloidea) based on nuclear ribosomal DNA sequences

Nuclear ribosomal sequence data from the internal transcribed spacers (ITS-1 and ITS-2), 5.8S subunit, and regions of the 18S and 28S genes were used to investigate sequence diversity among geographic samples of Nematodirus battus, and to infer phylogenetic relationships among Nematodirus species. Phylogenetic analysis of these data yielded strong support for relationships among species, depicting Nematodirus helvetianus and Nematodirus spathiger as sister-taxa and a clade of these 2 species and Nematodirus filicollis. This tree is consistent with caprine bovids as ancestral hosts, with a subsequent host shift to Bovinae in N. helvetianus. Eleven of 14 N. battus sequences were unique, with 19 variable sites among sequences representing 5 geographic samples. The lowest number of variable nucleotide sites was observed in samples representing apparently recent introductions to the United States and Canada, which is consistent with a population bottleneck concomitant with translocation. Comparison of directly sequenced polymerase chain reaction products and clones revealed evidence for intraindividual variation at some of the sequence sites, and this pattern of variation and that within geographic samples indicates incomplete rDNA repeat homogenization within species. This pattern of variation is not conducive for inferring phylogenetic relationships among sequences representing N. battus or addressing the putative history of introduction.     

Internal transcribed spacer rDNA can be used to infer the phylogenetic relationships of species within the genus Nematodirus (Nematoda: molineoidea)

Sequences of the first internal transcribed spacer rDNA were characterised for four veterinary important species of gastrointestinal nematodes from the genus Nematodirus. The sequence data were combined with previously published data of the second internal transcribed spacer to determine whether these rDNA regions provided a suitable number of informative characters to determine the phylogenetic relationships of species within the genus. A total of 32 alignment positions of the first internal transcribed spacer data set and 33 characters from the second internal transcribed spacer data set were informative in phylogenetic analyses. Irrespective of whether the data from each spacer were analysed separately or combined, only one most parsimonious tree was produced, with the relationships of the four species fully resolved. In addition, several regions of conservatism in the first internal transcribed spacer sequence among the four Nematodirus species suggests that this rDNA region may also provide phylogenetic information for higher taxonomic levels within the Molineoidea.     

Confirmation of two quantitative trait loci regions for nematode resistance in commercial British terminal sire breeds

Sheep internal parasites (nematodes) remain a major health challenge and are costly for pasture-based production systems. Most current breeding programmes for nematode resistance are based on indicator traits such as faecal egg counts (FEC), which are costly and laborious to collect. Hence, genetic markers for resistance would be advantageous. However, although some quantitative trait loci (QTL) have been identified, these QTL are often not consistent across breeds and few breeding strategies for nematode resistance in sheep are currently using molecular information. In this study, QTL for nematode resistance on ovine chromosomes (OAR) 3 and 14, previously identified in the Blackface breed, were explored using commercial Suffolk (n = 336) and Texel lambs (n = 879) sampled from terminal sire breeder flocks in the United Kingdom. FEC were used as the indicator trait for nematode resistance, and these were counted separately for Nematodirus and Strongyles genera. Microsatellite markers were used to map the QTL and the data were analysed using interval mapping regression techniques and variance component analysis. QTL for Nematodirus and Strongyles FEC were found to be segregating on OAR3 at 5% chromosome region-wide significance threshold in both Suffolk and Texel sheep, and Nematodirus FEC QTL were segregating on OAR14 in both breeds. In addition, QTL for growth traits were also found to be segregating at 5% chromosome region-wide on OAR3 and OAR14. The confirmation that FEC QTL segregate in the same position in three widely used breeds widens their potential applicability to purebred Blackface, Suffolk and Texel sheep, with benefits likely to be observed in their commercial crossbred progeny.     

Coevolution and biogeography among Nematodirinae (Nematoda: Trichostrongylina) Lagomorpha and Artiodactyla (Mammalia): exploring determinants of history and structure for the northern fauna across the holarctic

Nematodes of the subfamily Nematodirinae are characteristic components of a Holarctic fauna. The topology of a generic-level phylogenetic hypothesis, patterns of diversity, and geographic distributions for respective nematode taxa in conjunction with data for host occurrence are consistent with primary distributions determined across Beringia for species of Murielus, Rauschia, Nematodirus, and Nematodirella. Ancestral hosts are represented by Lagomorpha, with evidence for a minimum of 1 host-switching-event and subsequent radiation in the Artiodactyla. Diversification may reflect vicariance of respective faunas along with episodic or cyclical range expansion and isolation across Beringia during the late Tertiary and Quaternary. Secondarily, species of Nematodirus attained a distribution in the Neotropical region with minimal diversification of an endemic fauna represented by Nematodirus molini among tayassuids, Nematodirus lamae among camelids and Nematodirus urichi in cervids during the Pleistocene. Nematodirines are a core component of an Arctic-Boreal fauna of zooparasitic nematodes (defined by latitude and altitude) adapted to transmission in extreme environments characterized by seasonally low temperatures and varying degrees of desiccation. The history and distribution of this fauna is examined in the context of biotic and abiotic determinants for geographic colonization and host switching with an exploration of predicted responses of complex host-parasite systems to ecological perturbation under a regime of global climate change.     

Use of consensus sequences and genetic networks to identify members of the Bemisia tabaci cryptic species complex in Egypt and Syria

The sweet potato whitefly, Bemisia tabaci (Gennadius), is a cryptic species complex composed of at least 24 different morphologically indistinguishable species. The considerable differences in the pest status across the complex, and the ability of some to develop resistance to, insecticides make awareness of their identity critical in terms of developing effective control measures. Previously, phylogenetic reconstructions have been used to identify different B. tabaci, but this approach is no longer necessary because of the existence of mitochondrial cytochrome oxidase one consensus sequences for each of the known species. We therefore use these consensus sequences to determine the identities of the members of the complex in Syria and Egypt and then used genetic networks to reveal the pattern of their genetic relatedness to other haplotypes in the species to which they were assigned. The results showed the presence of three species in Syria, AsiaII 1, Middle East–Asia Minor 1 (this equates to the global invader known commonly as the B biotype) and Mediterranean (this equates to the global invader known commonly as the Q biotype). Egypt was shown to have two cryptic species, Middle East–Asia Minor 1 and Mediterranean. In Syria, Middle East–Asia Minor 1 was found around Damascus only (south‐west Syria), while Mediterranean was found throughout Aleppo (northern Syria) and Hama (north central Syria). AsiaII 1 was found around Hims (south central Syria) and Damascus (south‐western Syria). In Egypt, Mediterranean was found in Cairo and Ismailia (central Upper Egypt), while Middle East–Asia Minor 1 was found in the remaining all parts of Upper Egypt, Suez, North Sinai, Port Said, Dakahila, Behera and Alexandria which cover the main agricultural zone of Egypt. Genetic relatedness of Syrian and Egyptian populations with each other and with rest of world is also discussed.