Anthelmintic resistance in goat herds-In vivo versus in vitro detection methods.

Anthelmintic resistance (AR) is a serious threat to animal health and has a major economic impact worldwide due to production and financial losses. The aim of this study was to determine the occurrence of AR on 30 goat farms in Slovakia during the pasturing seasons and to compare three widely used in vitro and in vivo methods for detecting AR in field conditions. A three-year survey was conducted during the pasturing seasons of 2014-2016. Goats on each farm were split into treated and control groups and were treated by recommended (5 mg/kg body weight) and double doses (10 mg/kg b.w.) of albendazole. Comparisons between percent reduction in a faecal egg count reduction test (FECRT) and an egg hatch test (EHT) and the presence of L3 larvae in a larval development test (LDT) using resistant concentrations of benzimidazole (BZ) were monitored after treatment. The FECRT indicated percent reductions of 69.2-86.2% for the single dose and of 36.3-45.4% for the double dose. The EHT indicated that all farms had BZ-resistant nematodes. Low (<15% hatching) and high (>15% hatching) levels of resistance were detected on 13 and 17 farms, respectively. The LDT failed to detect resistant larvae on seven farms but detected low and high levels of resistance on seven and 14 farms, respectively. The data indicate a moderate correlation between in vitro and in vivo tests for detecting BZ resistance among the 30 goat farms. The hatching detected by the EHT and the presence of L3 larvae by the LDT at resistant BZ concentrations provided reasonable identification of low levels of resistance in the parasite populations, but the use of a double dose for a treatment may underestimate the real occurrence of low levels of resistant parasites on goat farms.

Hamulonema gen. nov. for Teladorsagia hamata and Ostertagia kenyensis in the ostertagiine fauna (Nematoda: Trichostrongyloidea) from African ungulates.

Hamulonema gen. nov. is proposed for Teladorsagia hamata and Ostertagia kenyensis in the ostertagiine nematode fauna found in artiodactyl hosts from Africa. Monomorphic species representing this genus are characterized by a bilaterally symmetrical and parallel synlophe in males and females, a 2-2-1 bursal formula, an accessory bursal membrane that is strongly cuticularized and reduced, a strongly reduced dorsal lobe and ray, and robust spicules with a simple, weakly pointed, ventral process, and curved, hooklike dorsal process. Species referred to Hamulonema nov. gen. are immediately distinguished from those of Camelostrongylus, Longistrongylus, Marshallagia, Orloffia, Ostertagia, and Pseudomarshallagia in which the bursal formula is 2-1-2 in males. Hamulonema nov. gen. is distinguished from those genera having a 2-2-1 bursa, including Africanastrongylus, Cervicaprastrongylus, Hyostrongylus, Mazamastrongylus, Sarwaria, Spiculopteragia, and Teladorsagia by the structure of the synlophe, bursa, genital cone, "0" and "7" papillae, dorsal lobe, and spicules in specific instances. In the global fauna, 4 of 14 ostertagiine genera are endemic to Africa. African genera may represent morphologically divergent and discrete or historically isolated lineages reflecting a pattern of geographic and host colonization as a driver for diversification since the Miocene.

Parasites of South African wildlife. XVII. Ostertagia triquetra n. sp. (Nematoda: Trichostrongylina) from the grey rhebuck, Pelea capreolus (Forster, 1790).

Re-examination of Teladorsagia hamata (Mönnig, 1932) Durette-Desset, 1989 reported from grey rhebuck, Pelea capreolus (Forster, 1790) proved it to be a new species of Ostertagi Ransom, 1907. The new species, for which the name Ostertagia triquetra n. sp. is proposed, differs from Teladorsagia hamata in the configuration of the bursal rays (2-1-2 in the former, 2-2-1 in the latter), and in that the interno-dorsal branch of the spicules bears a process that is triangular and convex in the new species, but concave and shaped like an ice-cream scoop in Teladorsagia hamata. Ostertagia triquetra has so far been found only in grey rhebuck in the Eastern Cape Province while Teladorsagia hamata was recorded from springbok, Antidorcas marsupialis (Zimmerman, 1780) and gemsbok, Oryx gazella (Unnaeus, 1758) in the western part of the country.

Synlophe in Ostertagia cf. kasakhstanica (Nematoda: Ostertagiinae), the minor morphotype of O. bisonis from western North America.

Ostertagia cf. kasakhstanica, the putative minor morphotype of the polymorphic ostertagiine O. bisonis, is reported in Bison bison from South Dakota. Descriptions of the synlophe and details of other diagnostic characters useful in identification and differentiation of this minor morphotype from other ostertagiines in wild and domestic ruminants from western North America are presented. Laterally, the cervical synlophe is consistent with Type Ib pattern among ostertagiines and is within the range of variation previously described for O. bisonis. Among recognized minor morphotypes of ostertagiines in wild and domestic ruminants from North America, O. kasakhstanica is distinct from O. kolchida, O. dikmansi, and O. arctica based on a tapering lateral synlophe. It is further distinguished from O. lyrata by the pattern of the cervical synlophe in the lateral field, structure of the genital cone and spicules, and dimensions of the esophageal valve. Although morphologically similar to T. davtiani/T. trifucata and T. boreoarcticus f. minor, it can be readily distinguished by the 2-1-2 bursal pattern, the structure of the spicules and genital cone, and the length of the esophageal valve. Ostertagia hisonis/O. cf. kasakhstanica circulates among pronghorn, mule deer, bison, and cattle in west-central North America.

The curvilinear relationship between worm length and fecundity of Teladorsagia circumcincta.

The variation among sheep in fecundity of Teladorsagia (Ostertagia) circumcincta was estimated by dividing the faecal egg count by the worm number following deliberate infection of mature Scottish Blackface lambs. Fecundity was skewed and ranged from 0 to 350 eggs per worm per day. Most animals had relatively low worm fecundities, but a small number of individuals had relatively high worm fecundities. However, as fecundity is a ratio of two imprecise estimates, extreme values may be statistical artefacts. Following both deliberate and natural infection, differences in worm fecundity were associated with differences in adult female worm length. In both infections, fecundity varied with worm length to the power 0.4. This relationship should assist the measurement of fecundity in studies of host immunity, in epidemiological modelling and in estimating the influence of density-dependent relationships.

Ostertagia nianqingtanggulaensis Kúng & Li, 1965 (Nematoda: Trichostrongyloidea) from sheep and goats at high altitudes in Nepal.

The trichostrongyloid nematode Ostertagia nianqingtanggulaensis Kúng & Li, 1965, previously recorded only from sheep in Tibet, is redescribed and is shown to be a common parasite of both sheep and goats at higher altitudes in the Himalayan foothills of western Nepal. Herbage examination indicated that infective larvae can overwinter on snow covered slopes. Use of tracer animals confirmed that migratory flocks are exposed to infection when grazing on alpine pastures during the summer months. In contrast, nearby non-migratory flocks kept at lower altitudes did not harbour O. nianqingtanggulaensis and tracer animals grazed with these flocks did not become infected with this species.

The length of strongylid nematode infective larvae as a reflection of developmental conditions in faeces and consequences on their viability.

Isolates from eight gastro-intestinal nematode species of sheep, cattle and deer parasites were maintained in sheep and faecal cultures were processed at different temperatures (for four species) and moistures (for the eight species). For all the tested species, the third-stage larvae (L3) were longer at temperatures optimal for development and their length increased linearly with faecal moisture contents (FMC). These variations in length mainly concerned the volume of intestinal cells. The length of L3 had no consequence on their survival in water at room temperature (five species tested), but the short L3 migrated more slowly on agar gel than did the longer ones (verified for three species) and exsheathed more slowly (verified for two species). The establishment rate observed for short L3 of Teladorsagia circumcincta in lambs was lower than that seen for long L3 in three other lambs, but the developed worms were similar in length and fecundity. These results are relevant to our understanding of how the different species could adapt to and/or compensate for adverse conditions of development.

Description of Ostertagia ostertagi and Ostertagia leptospicularis hybrids in experimentally infected sheep.

Hybrids of Ostertagia ostertagi and Ostertagia leptospicularis, derived from experimental infections in sheep, are described. Morphometrics of the hybrids were intermediate between those of parental lines for a large range of parameters (distance from apex to cervical papillae and length of esophagus for males and females, length of spicules for males, and length of vestibule, distance from vulva to the end of tail, width of tail at anus). The morphological relationship between hybrids and their parent species was assessed by discriminant analysis based on the relative values of these parameters (actual value/length of the worm). Each parental line, either bred in sheep or in the natural host, was morphologically similar and differed from hybrids.

Age resistance in calves to Ostertagia ostertagi and Cooperia oncophora.

Calves were infected repeatedly during a period of 6 weeks with Ostertagia ostertagi and Cooperia oncophora, at an age of 3, 6 or 9 months. The inoculations were performed during three periods, February-March, May-June and August-September, to account for possible seasonal effects or effects of larval batches. Observations were done on faecal egg output, antibody titres and weight gains. Calves were slaughtered for post mortem examinations 9 weeks after the start of infections. The influence of age on worm populations and egg output was significant for C. oncophora but not for O. ostertagi. The effect of season or larval batch on worm populations was significant for O. ostertagi but not for C. oncophora. The correlations between worm numbers and several other parameters found for Cooperia were strongly indicative of a process of worm expulsion taking place at the stage of infection (9 weeks after the start of infections) when post mortem examinations were done. Such correlations were absent for Ostertagia. It is concluded that within the range of ages examined here (the range to which first season grazing calves belong), there is no influence of age on Ostertagia populations but a clear effect of age on Cooperia. This difference strongly influences the total faecal egg output of grazing calves and its interpretation.

The identification of females within the subfamily Ostertagiinae Lopez-Neyra 1947.

As a result of the examination of many thousands of female nematodes classified as belonging to the sub-family Ostertagiinae Lopez-Neyra 1947, it became possible to compile descriptions of different female types, each of which corresponds to a polymorphic species as determined by male morphology. The female types have been designated as follows: Ostertagia ostertagi (males O. ostertagi and O. lyrata), Ostertagia circumcincta (males O. circumcincta, O. trifurcata and Teladorsagia davtiani), Ostertagia leptospicularis (males O. leptospicularis and O. kolchida) and Spiculopteragia asymmetrica (males S. asymmetrica and Apteragia quadrispiculata).

Systematics of the nematodes that cause ostertagiasis in cattle, sheep and goats in North America.

The systematics of the Ostertagiinae is unsettled with no agreement on how many genera and species are present in cattle and sheep. Ten species of Ostertagiinae are commonly parasitic in cattle and sheep. The males can be identified on the basis of differences in morphology of spicules and genital cones but the females of most species cannot be identified. The species-level systematics have been complicated by the proposal that the ten species are polymorphs of only five species. The systematics at genus level has been complicated by the use of numerous genera for the ten species, at present most commonly Ostertagia, Teladorsagia and Marshallagia. This report (1) describes the current knowledge of the systematics and (2) provides diagnoses of the genera recommended for the ten species. The morphology of the ten species was studied to determine whether characteristics could be found to identify females or to further differentiate the males. Characters studied included the system of longitudinal and surface cuticular ridges (synlophe), the internal morphology of the esophagus and the orientation of rays of the copulatory bursa. The study of species morphology resulted in additional support for the polymorphism proposal. All minor species were found to be identical to their major species in characteristics of the synlophe, esophagus and rays of the copulatory bursa. Two recent classifications of the Ostertagiinae both recommended the use of the genus Teladorsagia for the species T. circumcincta and the two minor species that occur with it, T. trifurcata and T. davtiani. Teladorsagia is characterized by a copulatory bursa in which the five lateral rays are arranged 2-2-1 and a ventral swelling of the genital cone (proconus) is absent. One pair of species, Marshallagia marshalli (major species) and Ostertagia occidentalis (minor species) should be included in the genus Marshallagia. This genus has been characterized by an elongated bursa in which the posterior pair of lateral rays are much longer than the ventral pair. The remaining two pairs of species (O. ostertagi and its minor species O. lyrata, and O. leptospicularis and its minor species O. kolchida) and O. bisonis belong in the genus Ostertagia which is characterized by a 2-1-2 arrangement of the five lateral rays of the copulatory bursa and the presence of a proconus.