Climate influences assemblages of abomasal nematodes of sheep on steppe pastures in the east of Algeria.

It is a common view that assemblages of parasitic nematodes are influenced by climatic conditions; however, there are only a few articles available regarding those that infect farm animals. We investigated the relationship between climate variables and infection with abomasal trichostrongyles in 335 1-year-old rams grazed on steppe pastures in Eastern Algeria. Abomasa were collected from 12 local slaughterhouses located in four climatic areas (from humid to arid) and the worms extracted, identified and counted. The abundance was low and the fauna composed primarily of Teladorsagia circumcincta, Marshallagia marshalli and Trichostrongylus sp. The high percentage of M. marshalli is typical of steppe areas. Ostertagia ostertagi and Haemonchus contortus were present in low numbers. Rainfall was the most important climatic variable related to the main species. This relationship was not linear for M. marshalli but an optimal rainfall was detected (350-400 mm/year). The more complex climatic indicators used in the study did not demonstrate a more significant correlation than rainfall. The predictive value of rainfall on the abundance or proportion of species in the assemblage was modest but highly significant. The seasonality of assemblages was different between the two main sub-climates (sub-humid and semi-arid).

Nonlinear Hysteretic Torsional Waves.

We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters.

Storage of gastrointestinal nematode infective larvae for species preservation and experimental infections.

Techniques to preserve the infective third-stage larvae (L3) of gastrointestinal nematodes are of considerable interest to preserve rare species and to maintain a stable source for routine experimental infections. This study compares the relative pros and cons of the two most common techniques, cryopreservation and refrigeration by comparing how they influence consequent infection outcome parameters in terms of life-history traits and fitness as a function of time using the gastrointestinal nematode of sheep Haemonchus contortus as a study species. Establishment capacity was found to be significantly reduced in cryopreserved stocks of L3 compared to refrigerated stocks, but this was followed by significant increases in their fecundity. Refrigeration did not affect L3 stocks consequent fitness by 16 months (the maximum examined) although they did incur a significant reduction in establishment, followed once again by an augmentation in fecundity. The study highlights potential areas for bias in comparing studies using L3 larvae maintained for different periods of time under different techniques.

Desiccation tolerance of gastrointestinal nematode third-stage larvae: exploring the effects on survival and fitness.

The free-living third-stage larvae (L3) of gastrointestinal nematodes are able to tolerate extreme weather conditions such as desiccation, but little is known about the consequent effects this has on their fitness. This study explored how the desiccation of Haemonchus contortus L3 larvae affected their absolute fitness by examining their success at consequent life cycle stages for a complete generation, and comparing them against a control. The stages examined include establishment, fecundity, larval development and pathogenicity. The results show that while desiccation greatly reduced the survival of the L3 prior to infection in sheep, their absolute fitness was not negatively impacted. Instead, it appears desiccation slightly augmented H. contortus fitness by triggering increases in fecundity. The study further explored what influence different gastrointestinal nematode (GIN) species (H. contortus, Trichostrongylus colubriformis, Teladorsagia circumcincta), isolates and age of L3 had on their capacity to revive following various periods of desiccation. The results showed desiccation tolerance varied as a function of each of these variables. The greatest L3 survival was found in Te. circumcincta followed by Tr. colubriformis and finally H. contortus. Significant variation was observed between individual species isolates and as a function of age. The results of this study carry important practical implications for the epidemiological understanding of gastrointestinal nematode species of economic importance.

The production of mammalian trematode infective stages by the snail Galba truncatula.

Several experiments on the breeding of trematode-infected Galba truncatula for obtaining and packaging Fasciola hepatica and Paramphistomum daubneyi metacercariae were carried out to determine the more convenient methods to use for commercial production of these infective stages. Compared to the breeding of infected snails in aquaterraria, the use of 14-cm Petri dishes allowed a greater prevalence of snail infection and a higher number of metacercariae. The production of these larvae was still 2.3-3.4 times greater if infected snails were dissected during the patent period. The aspiration of these metacercariae at the extremity of a Pasteur pipette significantly shortens the time necessary for their transfer from Petri dishes to Eppendorf tubes. Using 14-cm Petri dishes, snail dissection and metacercarial aspiration for their transfer strongly reduce the cost price for metacercarial production of the trematodes Fasciola hepatica and Paramphistomum daubneyi.

Comparative strategies and success of sympatric and allopatric Fasciola hepatica infecting Galba truncatula of different susceptibilities.

Allopatric infections of French Galba truncatula with an Argentinean isolate of Fasciola hepatica were carried out to determine the infectivity of foreign miracidia in three snail populations differing by their susceptibility to French miracidia (two highly and one poorly susceptible populations). Sympatric infections of G. truncatula with French miracidia were used as controls. Compared to sympatric infections of G. truncatula, snail survival at day 30 post-infection in allopatric groups was significantly lower in a highly susceptible population and significantly greater in the other two. Prevalence in snails infected with the allopatric isolate was significantly lower (16.4-34.5 % instead of 58.6-72.1 %), whereas their patent period was significantly longer (a mean of 69.9-85.9 days instead of 6.4-20.7 days). The mean number of metacercariae was also higher in allopatric groups (236.5-897.3 per cercariae-shedding snail instead of 70.7-222.1). Owing to longer patent periods, the Argentinean isolate of F. hepatica was less pathogenic for these snails. The lower prevalence of infection, the longer patent period and the higher number of metacercariae noted in allopatric groups might be the consequence of an adaptive mechanism used by this digenean introduced to the New World to infect new populations of unusual intermediate hosts.

Intermediate snail hosts of French Fasciola hepatica: Lymnaea neotropica and Lymnaea viatrix are better hosts than local Galba truncatula.

Allopatric and sympatric infections of Lymnaea neotropica and Lymnaea viatrix var. ventricosa with Argentinean and French isolates of Fasciola hepatica were carried out to determine the capacity of these snails to produce metacercariae and to verify if this capacity changed with snail generation. The same process was also made with a French population of Galba truncatula known to be highly susceptible to French isolates of the parasite. In each lymnaeid species separately considered, the survival rate at day 30 post-exposure and prevalence of F. hepatica infection in the group infected with Argentinean miracidia were significantly greater than those recorded in the corresponding French one. Compared to infected G. truncatula, both South American lymnaeids had longer patent periods and produced a higher number of metacercariae. The highest infections were noted with L. v. ventricosa. In the three snail species, metacercarial production was more important with the Argentinean isolate of miracidia than with the French one. If three successive generations of L. v. ventricosa are exposed to the same French isolate of miracidia, cercarial production significantly increased from parents to the F2 generation, while the other characteristics of infection only showed insignificant variations. L. neotropica and L. v. ventricosa are better intermediate hosts for French F. hepatica than local G. truncatula. The numerical increase of shed cercariae in the F1 and F2 generations of L. v. ventricosa demonstrates a rapid adaptation of this species to the French isolate of the parasite.

Contrasting views of animal healthcare providers on worm control practices for sheep and goats in an arid environment.

A questionnaire survey was conducted to determine the worm control practices and anthelmintic usage of 150 key respondents involved in sheep and goat production in the arid Thal area of Pakistan. The information was collected by visiting farms, and interviewing the key respondents which included veterinary officers (n = 15), veterinary assistants (n = 51), traditional practitioners (n = 24), and small and large scale sheep/goat farm herders and owners (n = 60). Among all interviewed animal healthcare providers, the veterinary officers had the highest level of awareness of parasitic infection and advocated the use of modern available anthelmintics according to the predefined schedule. The farmers on the other hand, had the lowest level of knowledge about parasitic infections. They used modern anthelmintics at low frequencies (every six months) following an unusual practice of diluting the medicine. Veterinary assistants had a medium level of awareness about the parasitic infections using anthelmintic treatments when they deemed necessary rather than following a predefined treatment schedule. Traditional practitioners were also aware of parasitic infections and used traditional anthelmintics or a combination of the traditional and modern anthelmintics. The animal health providers had a different awareness and knowledge of parasitic infections which resulted in contrasting proposals for its' control. The farmers used worm control measures in accordance with their own views and those of animal healthcare advisors, combining modern and traditional treatments. This study provides the first insight into the differing views of those animal healthcare providers who form the basis for effective parasitic control within the sheep and goat industry of an arid region.

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.

Parascaris and cyathostome nematodes in foals: parasite in transit or real infection?

Faecal egg counts were performed in 187 foals of a large Polish stud farm between February and September 2007. Eggs of Parascaris equorum were present in faeces of 7% and those of cyathostomins in 13% of the foals aged less than 194 days. Information dealing with age of foals and/or efficiency of ivermectin treatment as well as the nematode parasite prepatent periods, it can be conducted that most of the infections recorded on the basis of faecal egg counts were false-infections in animals up to the age of six months, probably due to the ingestion of infected faeces of their dam or some other horses.

Contrasting genetic structures of two parasitic nematodes, determined on the basis of neutral microsatellite markers and selected anthelmintic resistance markers.

For the first time, the neutral genetic relatedness of natural populations of Trichostrongylid nematodes was investigated in relation to polymorphism of the beta-tubulin gene, which is selected for anthelminthic treatments. The aim of the study was to assess the contribution of several evolutionary processes: migration and genetic drift by neutral genetic markers and selection by anthelminthic treatments on the presence of resistance alleles at beta-tubulin. We studied two nematode species (Teladorsagia circumcincta and Haemonchus contortus) common in temperate climatic zones; these species are characterized by contrasting life history traits. We studied 10 isolated populations of goat nematode parasites: no infected adult goat had been exchanged after the herds were established. Beta-tubulin polymorphism was similar in these two species. One and two beta-tubulin alleles from T. circumcincta and H. contortus respectively were shared by several populations. Most of the beta-tubulin alleles were 'private' alleles. No recombination between alleles was detected in BZ-resistant alleles from T. circumcincta and H. contortus. The T. circumcincta populations have not diverged much since their isolation (F(ST) <0.08), whereas H. contortus displayed marked local genetic differentiation (F(ST) ranging from 0.08 to 0.18). These findings suggest that there are severe bottlenecks in the H. contortus populations, possibly because of their reduced abundance during unfavourable periods and their high reproductive rate, which allows the species to persist even after severe population reduction. Overall, the data reported contradict the hypothesis of the origin of beta-tubulin resistance alleles in these populations from a single mutational event, but two other hypotheses (recurrent mutation generating new alleles in isolated populations and the introduction of existing alleles) emerge as equally likely.

Monitoring the efficacy of ivermectin and albendazole against gastro intestinal nematodes of cattle in Northern Europe.

Faecal egg count reduction tests (FECRT) using ivermectin (IVM) and benzimidazole (BZ) were conducted to investigate the prevalence of anthelmintic resistance in gastro-intestinal nematodes on cattle farms in Germany, Belgium and Sweden in 2006 and 2007. Based on sufficient numbers of eggs prior to the study, between 3 and 10 farms per country were selected. 10-15 animals were randomly selected per farm and subcutaneously treated with 0.2 mg IVM/kg bodyweight (Ivomec, Merial). Faecal samples were collected individually from every animal on day 0 (treatment), day 7 (Belgium & Sweden) or 14 (Germany), and day 21 (Germany, Belgium and Sweden). Faecal egg counts (FEC) were performed at each sampling occasion to estimate the eggs per gram of faeces (EPG) and the reduction of eggs after treatment. The FECRT using IVM in 2006 revealed mean reduction of egg counts between 69-100% on day 7/14 (95% confidence interval (CI) 19-102) and 35-96% (95% CI 0-102) on day 21. Farms with a suggested problem of anthelmintic resistance have been re-visited in 2007 and except for one case all results obtained in 2006 were confirmed in 2007. Larvae obtained from faecal cultures were identified using microscopic identification keys or genus-specific real time PCR. Cooperia oncophora was the predominant species detected after treatment, but Ostertagia ostertagi was found in samples on 3 farms in Germany and 3 farms in Sweden post-treatment. In 2007 additionally a FECRT using benzimidazoles was conducted in Germany and Sweden. In Germany oral Valbazen (albendazole, 10%, Pfizer) was used at a concentration of 7.5 mg albendazole/kg bodyweight; in Sweden Valbazen Vet (albendazole, 10%, Orion Pharma) at a dose of 8 mg/kg was used. For benzimidazoles an efficacy of 100% was obtained on all tested farms in both countries. This is the first report of a multinational anthelmintic efficacy investigation in cattle in Europe. The results suggest that testing of anthelmintic efficacy should be performed more intensively due to possible insufficient efficacy of current drugs.

Occurrence of strongyles (Strongylidae) in horses from small farms on the basis of necropsy.

Three parts of the large intestine, i.e. the dorsal and ventral colon, and caecum in 41 working horses from small farms in southern Poland were examined. Five species of large strongyles (3 migratory species from genus Strongylus and 2 non-migratory from genus Triodontophorus) and as well as 17 species of cyathostomes were revealed. The prevalence of large strongyles was observed, accordingly: Strongylus vulgaris--80.5%, S. equinus--9.8%, S. edentatus--4.9%, Triodontophorus serratus--19.5% and T. brevicauda--7.3%. Among cyathostomes, 5 most prevalent species were Cyathostomum catinatum--31.7%, Coronocyclus coronatus--31.7%, Cylicostephanus calicatus--24.4%, Cylicocyclus nassatus--24.4% and C. ashworthi--19.5%. The highest prevalence of S. vulgaris among all Strongylidae isolated specimens suggests that the infection with this parasite should be taken into account in the diagnosis of colics in working horses kept in the small farming system.

The global diversity of Haemonchus contortus is shaped by human intervention and climate.

Haemonchus contortus is a haematophagous parasitic nematode of veterinary interest. We have performed a survey of its genome-wide diversity using single-worm whole genome sequencing of 223 individuals sampled from 19 isolates spanning five continents. We find an African origin for the species, together with evidence for parasites spreading during the transatlantic slave trade and colonisation of Australia. Strong selective sweeps surrounding the ß-tubulin locus, a target of benzimidazole anthelmintic drug, are identified in independent populations. These sweeps are further supported by signals of diversifying selection enriched in genes involved in response to drugs and other anthelmintic-associated biological functions. We also identify some candidate genes that may play a role in ivermectin resistance. Finally, genetic signatures of climate-driven adaptation are described, revealing a gene acting as an epigenetic regulator and components of the dauer pathway. These results begin to define genetic adaptation to climate in a parasitic nematode.

Pro and cons of targeted selective treatment against digestive-tract strongyles of ruminants.

The increasing prevalence of resistance to anthelmintics among gastrointestinal nematodes and the desire for lower input agriculture have promoted the idea that targeted selective treatment (treating the animals in need of such a treatment and only them) could be a sustainable solution for controlling internal parasites of ruminants. The pros are the slowing of resistance prevalence, lower residues of anthelmintics in meat and milk, and lower cost; the cons are the difficulty and time spent on selecting animals in need of treatment and the possibility of lower production. Using actual experiments and modelling we show that targeted selective treatment can be used to sustainably control gastrointestinal nematode infections in flock.

The scientific research programmes of Lakatos and applications in parasitology.

The methodology of scientific research programme (MSRP) proposed by Lakatos was in the line of the proposals made by Popper. MSRP were intended for constructing and evaluating research programme, which is unique among philosophers of science. Surprisingly, scientists dedicated to research in mathematics, physic or biology have not used much MRSP. This could be due to the fact that scientists are not aware of the existence of MSRP, or they find it difficult to apply to their own investigations. That is why we present firstly the main characteristics of this methodology (hard core--the group of hypothesis that are admitted by experts in the field, auxiliary hypotheses--which are intended to protect and refine the hypotheses of the hard-core, and heuristics for mending and evaluating the MSRP) and, secondly, propose an example in helminthology. We think that the methodology of Lakatos, is a useful tool, but it cannot encompass the large flexibility of investigations pathways.

Are sainfoin or protein supplements alternatives to control small strongyle infection in horses?

The spread of anthelmintic resistance in equine strongyle nematodes has become a major problem, advocating for the development of alternative control for strongyles. Our study consisted of both in vivo and in vitro experiments. We investigate for the first time the efficacy of a short-term consumption of tannin-rich sainfoin (Onobrychis viciifolia) or extra proteins in naturally infected horses. We used 30 horses allocated into three groups of 10 individuals that received for 18 days either (i) a tannin-rich diet with 70% DM sainfoin pellets (Sd), (ii) a protein-rich diet with 52% DM Italian rye-grass pellets and 18% DM grinded linseed expeller (Pd), or (iii) a control diet with 45% DM barley and 25% DM cereal-based pellets (Cd). The three diets were isoenergetic, covering 94% of animal energy requirements on average, and the Sd and Pd diets were isoproteic and provided extra proteins (227% of protein requirements v. 93% for the Cd diet). Pd and Cd were compared to test for benefits of receiving extra proteins, while Sd and Pd were compared to account for the effect of sainfoin secondary metabolites. There were no between-diet differences in faecal egg counts (FEC) or in worm burden evaluated from worm counts in faeces of drenched horses at the end of the experiment. However, coprocultures from the faeces collected in each group at the beginning and at the end of the experiment suggested a lower rate of strongyle larval development in the Sd group at the end of the experiment (Sd=8.1%, Pd=30.5%, Cd=22.6%). In vitro tests using sainfoin solutions evidenced the influence of sainfoin on strongyle larval development: adding 29% of sainfoin pellets to faeces reduced the strongyle egg development into infective larvae by 82% (P<0.001) and using solutions with sainfoin concentrations higher than 7.5 mg/ml reduced egg hatching by 37% (P<0.05). The short-term use of tannin-rich plants in horse diet could thus constitute a promising strategy to reduce the risk of infection by strongyles at pasture.

Repeated treatment faecal egg counts to identify gastrointestinal nematode resistance in a context of low-level infection of sheep on farms in eastern Algeria.

The efficacy of benzimidazoles and ivermectin was tested in 14 pilot farms in eastern Algeria. Resistance was detected in strongyle nematodes against benzimidazoles (five farms) and ivermectin (one farm). The main genera in the region were resistant: Teladorsagia, Trichostrongylus, Marshallagia and Nematodirus. The evaluations based on FECRT (faecal egg count reduction tests) were not always consistent due to the low-level of infection, and we developed a simplified, repeated treatment strategy to investigate resistance. The results obtained with repeated treatment faecal egg counts match globally those obtained with conventional faecal egg count reduction tests. This simplified, repeated treatment method should be investigated further since it is quicker, and this could make it possible to test larger farm samplings.

The establishment rate of a sheep nematode: revisiting classics using a meta-analysis of 87 experiments.

Strongyle nematode establishment rate in their host is a highly variable life history trait, which makes it difficult to estimate. A meta-analysis was applied to the nematode Teladorsagia circumcincta of sheep in order to acquire a general framework of the factors modulating this life trait. A linear model was built with individual data on 540 infected lambs extracted from 13 articles. Lambs breed and age, time lag between last infection and the interaction between infection mode, infective dose and the number of repeated infective doses were significantly related with the establishment rate. The influence of infection mode on nematode establishment rate was also evaluated by comparing nematode establishment rate distributions within lamb populations infected under different conditions. Natural and repeated experimental infections lead to similar distribution of establishment rate. Conversely, these infection conditions resulted in different parasite establishment rates in average (12.7 and 23.4%, respectively). Three hypotheses are discussed to explain this result: immune protective response, host avoidance behaviour and parasite virulence.

Estimation of abomasum strongyle nematode infections in sheep at necropsy: tentative proposals for a simplified technique.

Several necropsy techniques are available for estimating the abundance of gastro-intestinal nematodes in abomasum of ruminants. Standardization of techniques is needed to allow accurate comparisons between laboratories. Here we propose a standardized technique for estimating the abundance of worms. We intend to compare the worms' number estimations in lambs and ewes based on contents and washings, to determine the uniformity of worm counts in aliquots, and to estimate the total worm number from washings. The digesta (or "contents") and the washings of the abomasum are treated separately. The worms of each subsample are diluted with water and the total number of worms is estimated on a small volume (aliquots) of these subsamples. The use of aliquots assumes that the worms are uniformly distributed in the whole volume of each subsample. We first confirmed that the use of aliquots is appropriate in most cases. We then show that the use of the washings alone allows a faster and a suitable estimation of the total worm burden for all strongyle species of the abomasum in both ewes and lambs. The evaluation of our necropsy procedure is a first step to a standardized technique which should be improved by validation in other laboratories.