Genera Of Gastrointestinal Nematodes Research Articles

Epidemiology and field efficacy of anthelmintic drugs associated with gastrointestinal nematodes of sheep in Nejo district, Oromia, Ethiopia

Gastrointestinal nematodes (GINs) are major constraints to health and productivity of small ruminants. Methods of their control relies mainly on anthelmintic drugs; however, the indiscriminate use of these drugs could lead to the development of anthelmintic resistance (AR). This study aimed to investigate the epidemiology of GINs infection, and field evaluation of anthelmintic efficacy in sheep. The epidemiological data were collected using a cross-sectional study design while a farm-based field study design was employed for the evaluation of anthelminthic efficacy. Furthermore, standard parasitological techniques were employed for qualitative and quantitative worm identification. The overall prevalence indicated 50.3%. Six genera of GINs (Haemonchus, Trichostrongylus, Oesophagostomum/Chabertia, Trichuris, Teladosargia/Ostertagia and Nematodirus) were identified. Among the identified genera, Haemonchus (25.4%) and Trichostrongylus (24.8%) were the dominant genera followed by mixed infection (21.8%), Oesophagostomum/Chabertia (10.4%), Trichuris (7.8%), Teladosargia (Ostertagia) (5.7%) and Nematodirus (4.1%). Mixed infections consisted either of double infections with Haemonchus and Trichostrongylus, or triple infections with Haemonchus, Trichostrongylus and Trichuris. The McMaster egg counting results showed that the mean EPG of infected sheep was 845.6. The results also showed 66 (34.2%), 101 (52.3%) and 26 (13.5%) sheep had low, moderate and heavy worm burden, respectively. Albendazole and Ivermectin showed low efficacy (percentage reductions = 90% and 92%; 95% lower confidence limit = 82.1% and 83.6% respectively) whereas Tetramisole was effective (FECR% = 96.8%; 95% LCL = 93.4%). Factors such as age, body condition, management system and past deworming history of sheep were found to have a statistically significant (p < 0.05) influence on the occurrence and burden of the worms. This is further explained as the highest prevalence and worm burden was detected in sheep of young age (p = 0.008; OR = 0.58; 95% CI = 0.39–0.87), poor body condition (p = 0.001; OR = 0.08; 95% CI = 0.04–0.16) and sheep kept under semi-intensive (p = 0.04; OR = 1.53; 95% CI = 1.02–2.29) with no deworming history for the last two months (p = 0.001; OR = 2.97; 95% CI = 1.94–4.56). The study results revealed that nematode infections were among sheep health constraints that could hurt their productivity while low efficacy of Albendazole and Ivermectin were detected. Therefore, the appropriate management techniques of GIN infections should be designed and implemented. Moreover, a further study involving more sensitive techniques (e.g. Mini-FLOTAC, molecular, and serological techniques) should be conducted by considering different host and environmental risk factors such as production level and seasons.

Monepantel-based anthelmintic combinations to optimize parasite control in cattle

Improvement in the use of existing anthelmintics is a high priority need for the pharmaco-parasitology research field, considering the magnitude and severity of anthelmintic resistance as an important issue in livestock production. In the work described here, monepantel (MNP) was given alone or co-administered with either macrocyclic lactone (ML) or benzimidazole (BZ) anthelmintics to calves naturally infected with ML- and BZ-resistant gastrointestinal (GI) nematodes on two different commercial cattle farms. Both pharmacokinetic (PK) and efficacy assessments were performed. On Farm A, male calves (n = 15 per group) were treated with either MNP orally (2.5 mg/kg), IVM s.c. (0.2 mg/kg), ricobendazole (RBZ) s.c. (3.75 mg/kg) or remained untreated. On Farm B, eight groups (n = 15) of male calves received treatment with either: MNP, abamectin (ABM, oral, 0.2 mg/kg), RBZ (s.c., 3.75 mg/kg), albendazole (ABZ, oral, 5 mg/kg), MNP+ABM, MNP+RBZ, MNP+ABZ (all at the above-mentioned routes and doses) or remained untreated. Seven animals from each treated group (Farm B) were randomly selected to perform the PK study. MNP and its metabolite monepantel sulphone (MNPSO2) were the main analytes recovered in plasma after HPLC analysis. The combined treatments resulted in decreased systemic exposures to MNP parent drug compared with that observed after treatment with MNP alone (P < 0.05). However, the systemic availability of the main MNP metabolite (MNPSO2) was unaffected by co-administration with either ABM, RBZ or ABZ. Efficacies of 98% (Farm A) and 99% (Farm B) demonstrated the high efficacy of MNP given alone (P < 0.05) against GI nematodes resistant to ML and BZ in cattle. While the ML (IVM, ABM) failed to control Haemonchus spp., Cooperia spp. and Ostertagia spp., MNP achieved 99% to 100% efficacy against those nematode species on both commercial farms. However, MNP alone failed to control Oesophagostomum spp. (60% efficacy) on Farm A. The co-administered treatments MNP+ABZ and MNP+RBZ reached a 100% reduction against all GI nematode genera. In conclusion, the oral treatment with MNP should be considered to deal with resistant nematode parasites in cattle. The use of MNP in combination with BZ compounds could be a valid strategy to extend its lifespan for use in cattle as well as to reverse its poor activity against Oesophagostomum spp.

Anthelmintic Properties of Essential Oils to Control Gastrointestinal Nematodes in Sheep-In Vitro and In Vivo Studies.

Herbal products such as essential oils may play a promising role in the treatment of infections caused by gastrointestinal nematodes (GINs). The aim of this study was to evaluate the in vitro potential of 11 essential oils (EOs) and one binary combination of isolated EO compounds, as well as the in vivo anthelmintic efficacy of two EO formulations. Four GIN genera were identified in the coproculture examination: Haemonchus, Trichostrongylus, Teladorsagia and Chabertia. The in vitro egg hatch test (EHT) was performed at six different concentrations (50, 12.5, 3.125, 0.781, 0.195 and 0.049 mg/mL) for each EO, whereas in the in vivo faecal egg count reduction test (FECRT), each EO sample was diluted in sunflower oil and orally administrated at a dose of 100 mg/kg to the different group of animals. In the EHT, the EOs of Origanum vulgare, Foeniculum vulgare, Satureja montana, Satureja hortensis and two types of Thymus vulgaris were the most effective. The dominant compounds of these EOs were carvacrol, thymol, anethol, p-cymene and γ-terpinene, indicating their importance for the anthelmintic activity. In the FECRT, both T. vulgaris EO type 1 and linalool:estragole combination show an anthelmintic potential with a mean effect on FECR of approximately 25%. The results suggest the possible role of tested EOs as anthelmintic agents in sheep farms, although further in vivo tests are needed.

A simple molecular method to identify and quantify genera of gastrointestinal nematodes of cattle.

Classic approaches for antemortem identification of gastrointestinal nematodes (GIN) require coproculture of eggs and morphological examination. While adequate for diagnosis, many PCR techniques cannot easily quantify mixed infections without controls and/or standard curves. Herein, we developed a simple and rapid test for differentiating and quantifying mixed infections of GIN using PCR products separated by capillary electrophoresis. Among the cattle GIN, the ITS2 region is sufficiently distinct in length to delineate among the most common infecting genera, Ostertagia ostertagi = 373 bases (b), Haemonchus contortus (placei) = 366b, Cooperia punctata (oncophora) = 376b, Trichostrongylus axei = 372b, and Oesophagostomum radiatum = 357b. Conserved primers were synthesized that span the ITS2 where one primer was fluorescently labeled with 6-FAM. DNAs from infective L3 were PCR amplified then loaded onto an ABI 3130 sequencer adapted for size fragment analysis. Resulting peak amplitudes were both diagnostic and quantitative on a relative basis. As proof of principle, quantification was performed on PCR fragments from mixed species pairs of Ostertagia ostertagi, Cooperia punctata, and Haemonchus contortus and analyzed using Gene Marker V1.85 software. In all cases, linear responses were observed where R2 > 0.97 and line slopes ranged between 0.90 and 1.1. When tested on eggs from naturally infected animals, the assay showed superior results on two farms when compared to coproculture and morphological identification. Using wildlife-derived samples, results coincided well with deep amplicon sequencing. The assay is adaptable to large-scale studies, does not require comparative PCR controls, and should be compliant with GIN from small ruminant livestock.

Preliminary Assessment of Body Condition Score as a Possible Marker for the Targeted Selective Treatment of Dairy Sheep Against Gastrointestinal Nematodes

PurposeIn the fight against anthelmintic resistance, targeted selective treatments (TSTs), where only a small percentage of a flock receives treatment, have become increasingly popular. Overall, implementation of such treatments can be based on various parameters including Body condition score (BCS). As infection with non-bloodsucking nematodes, frequently encountered on sheep farms in the central Mediterranean basin, commonly causes bodyweight reduction, the aim of this research is to evaluate the effectiveness of BCS as a parameter for the implementation of TSTs in lactating dairy sheep with subclinical gastrointestinal nematode (GIN) infections from the island of Sardinia, Italy.MethodsFaecal samples from 1012 ewes divided into 2 groups (third and fifth month of lactation) were collected and their BCS recorded. Faecal egg counts and coprocultures were performed for the assessment of the GIN burden and identification of present species.ResultsAn overall GIN prevalence of 85.4% with a mean eggs per gram (EPG) of faeces of 210.1 ± 347.3 was found. Teladorsagia spp. and Trichostrongylus spp. were the GIN genera most identified. Overall, animals with the lowest BCS had the highest EPG values and a negative correlation (r = − 0.163) between the EPG values and BCS of the studied animals was found, which was most significant for older sheep.ConclusionThis research confirmed BCSs and EPG values for GIN in sheep to be negatively correlated, particularly in older ewes. Application of TSTs for lactating sheep with a BCS < 2.25, especially to older ewes, could be beneficial in case of subclinical GIN infections, although further studies are needed to work out precise recommendation.

Anthelmintic Activity of Extracts and Active Compounds From Diospyros anisandra on Ancylostoma caninum, Haemonchus placei and Cyathostomins.

The present study aimed to evaluate the anthelmintic activity of leaf and bark extracts of Diospyros anisandra collected during different seasons and their major constituents on eggs of Ancylostoma caninum, Haemonchus placei, and cyathostomins. Specifically, the eclosion inhibition of the methanolic extracts of the leaves and bark of D. anisandra collected during the dry and rainy seasons (600–37.5 μg/ml) were evaluated in addition to the fractions, sub-fractions (300–37.5 μg/ml) and active major constituents (150–2.3 μg/ml). The rainy season bark extract had the highest percentage of eclosion inhibition (PEI) against the evaluated nematodes (≥ 90% at 75 μg/ml) along with high ovicidal activity (90.0 to 93.4% at 75 μg/ml). The purification of the rainy season bark extract showed that its biological activity came from the non-polar n-hexane fraction (≥ 93% at 75 μg/ml). The bioguided fractionation pointed to sub-fraction 5 as having the highest anthelmintic activity against the three evaluated genera of nematodes (PEI ≥ 93% at 37.5 μg/ml). Gas chromatography and mass spectrometry revealed that the major constituent in sub-fraction 5 was plumbagin. Upon evaluation, plumbagin was confirmed to be responsible for the anthelmintic activity of D. anisandra, with a PEI ≥ 90% at 2.3 μg/ml on the three evaluated nematodes. Additionally, the compounds betulin and lupeol in the bark of D. anisandra were evaluated but presented low anthelmintic activity (PEI ≤ 5.3% at 2.3 μg/ml). In conclusion, the rainy season bark extract of D. anisandra exerts a high ovicidal activity against the eggs of the three studied nematodes. Plumbagin is the active compound responsible for this activity and represents a potential alternative for the control of different genera of gastrointestinal nematodes given the current scenario of anthelmintic resistance.

The first report of multidrug resistance in gastrointestinal nematodes in goat population in Poland

BackgroundProphylactic anthelmintic treatment with one of three basic classes of anthelmintics (benzimidazoles, macrocyclic lactones and imidazothiazoles) is still the mainstay of control of gastrointestinal nematode infections in small ruminants worldwide. As a consequence, anthelmintic resistance is a serious threat to small ruminant health and production. While the resistance to one class of anthelmintics has already been reported in most of countries, the newly-emerging problem is the resistance to two or even all of classes referred to as multidrug resistance. This study aimed to evidence the presence of multidrug resistance of gastrointestinal nematodes in goats in Poland.ResultsThe combination of one in vivo method (fecal egg count reduction test) and two in vitro methods (egg hatch test and larval development test) performed in two goat herds in the southern Poland showed the presence of gastrointestinal nematodes resistant to fenbendazole and ivermectin in both herds. Moreover, in one herd it revealed the development of resistance to the last effective anthelmintic, levamisole, in response to one-year intensive use. Haemonchus contortus was the most prevalent gastrointestinal nematode in samples in which resistance to benzimidazoles and ivermectin was found, whereas Trichostrongylus colubriformis predominated when resistance to levamisole was observed.ConclusionThis study shows for the first time that multidrug resistance of gastrointestinal nematodes to three basic classes of anthelmintics is already present in goat population in Poland. Moreover, it may indicate that different species or genera of gastrointestinal nematodes are responsible for the resistance to specific anthelmintics.

Methods to determine resistance to anthelmintics when continuing larval development occurs

The in vivo faecal egg count reduction test (FECRT) is the most commonly used test to detect anthelmintic resistance (AR) in gastrointestinal nematodes (GIN) of ruminants in pasture based systems. However, there are several variations on the method, some more appropriate than others in specific circumstances. While in some cases labour and time can be saved by just collecting post-drench faecal worm egg counts (FEC) of treatment groups with controls, or pre- and post-drench FEC of a treatment group with no controls, there are circumstances when pre- and post-drench FEC of an untreated control group as well as from the treatment groups are necessary. Computer simulation techniques were used to determine the most appropriate of several methods for calculating AR when there is continuing larval development during the testing period, as often occurs when anthelmintic treatments against genera of GIN with high biotic potential or high re-infection rates, such as Haemonchus contortus of sheep and Cooperia punctata of cattle, are less than 100% efficacious. Three field FECRT experimental designs were investigated: (I) post-drench FEC of treatment and controls groups, (II) pre- and post-drench FEC of a treatment group only and (III) pre- and post-drench FEC of treatment and control groups.To investigate the performance of methods of indicating AR for each of these designs, simulated animal FEC were generated from negative binominal distributions with subsequent sampling from the binomial distributions to account for drench effect, with varying parameters for worm burden, larval development and drench resistance. Calculations of percent reductions and confidence limits were based on those of the Standing Committee for Agriculture (SCA) guidelines. For the two field methods with pre-drench FEC, confidence limits were also determined from cumulative inverse Beta distributions of FEC, for eggs per gram (epg) and the number of eggs counted at detection levels of 50 and 25. Two rules for determining AR: (1) %reduction (%R)<95% and lower confidence limit <90%; and (2) upper confidence limit <95%, were also assessed. For each combination of worm burden, larval development and drench resistance parameters, 1000 simulations were run to determine the number of times the theoretical percent reduction fell within the estimated confidence limits and the number of times resistance would have been declared.When continuing larval development occurs during the testing period of the FECRT, the simulations showed AR should be calculated from pre- and post-drench worm egg counts of an untreated control group as well as from the treatment group. If the widely used resistance rule 1 is used to assess resistance, rule 2 should also be applied, especially when %R is in the range 90 to 95% and resistance is suspected.

Benzimidazole resistance of sheep nematodes in Norway confirmed through controlled efficacy test

BackgroundResistance against benzimidazoles (BZ) has recently been detected in Norwegian sheep flocks through a large scale prevalence survey based on the faecal egg count reduction test (FECRT). The use of this test in combination with bulk larval culture only gives an indication of which gastrointestinal nematodes genera that are involved and these results have to be confirmed by a controlled efficacy test (CET) to get accurate information about resistant nematodes populations at species level. A CET was therefore performed with larvae from two flocks where BZ resistance was previously detected through FECRT.ResultsThe latter test confirmed the previous results in both flocks. In flock A, the BZ resistant nematode population consisted solely of Haemonchus contortus, whereas H. contortus and Teladorsagia circumcincta comprised the resistant worm population in flock B.ConclusionsSome discrepancies that have been recorded between FECRT and CET results regarding time for post-treatment coproscopical examination and a temporary suppression of faecal egg excretion are discussed.

Occurrences of Eimeria spp. and gastrointestinal nematodes in dairy calves in southern Minas Gerais, Brazil

The aim of this cross-sectional observational study was to determine the frequency and factors associated with infection by Eimeria spp. and gastrointestinal nematodes in 356 calves on 20 dairy farms located in southern Minas Gerais, Brazil. Ten species of Eimeria spp. were identified, of which E. bovis (37.6%) and E. zuernii (17.9%) were the most frequent. From fecal cultures, four genera of gastrointestinal nematodes were recovered, of which Cooperia spp. (74.6%) and Haemonchus (19.4%) were the most frequent. Variables relating to higher levels of technology used on dairy farms showed a significant association (p < 0.05) with higher OPG and EPG counts, and are discussed in this study.

A large-scale clinical field study to evaluate the efficacy and safety of an oral formulation of the amino-acetonitrile derivative (AAD), monepantel, in sheep in New Zealand

AIM: To evaluate the efficacy and safety of an oral formulation of the novel anthelmintic, monepantel (AAD 1566), in sheep, in comparison with some other anthelmintics currently registered in New Zealand. METHODS: A study was conducted on 18 farms located throughout the North and South Islands of New Zealand. On each farm, sheep naturally infected with the target nematodes were randomly assigned to groups, which were then treated with either monepantel, at a minimum dose rate of 2.5 mg/kg, or one of five other anthelmintics encompassing the range of single-entity and combination formulations that are commercially available in New Zealand, or left untreated as controls. Faecal samples were collected from all sheep pre-treatment (1–3 weeks before treatment), at the time of treatment, and approximately 1, 2 and 3 weeks after treatment (Days 7, 14 and 21). Faecal nematode egg counts (FEC) were measured in all samples, and the efficacy of treatments, as indicated by reductions in FEC, calculated. All sheep were inspected at least daily, to check for any adverse effects of treatment. RESULTS: On all 18 farms, on Days 7, 14 and 21 (54 test points), the efficacy of the monepantel solution was >95%. At Days 7 and 14 post-treatment, efficacies >99% were recorded in 15 flocks. At Day 21 post-treatment, efficacies >98% were recorded in 13 flocks. Monepantel was as effective, or more effective, than the registered anthelmintics with which it was compared. Moreover, it was effective against strains of nematodes resistant to one or more of the currently available broadspectrum anthelmintics. The monepantel solution used in this study was well tolerated by the sheep, and no adverse events could be attributed to its use. CONCLUSIONS AND CLINICAL RELEVANCE: When administered as an oral formulation under field conditions, at a minimum dose rate of 2.5 mg/kg, monepantel appeared to be highly effective against all the major genera of gastrointestinal nematodes of sheep, including Haemonchus, Teladorsagia (=Ostertagia), Trichostrongylus, Cooperia, Nematodirus, Chabertia and Oesophagostomum. This included strains resistant to the currently available broad-spectrum anthelmintics. Monepantel is the first compound from the recently discovered amino-acetonitrile derivative (AAD) class of anthelmintics to be developed for use in sheep.

Prevalence and seasonal incidence of nematode parasites and fluke infections of sheep and goats in eastern Ethiopia

A 2-year abattoir survey was carried out to determine the prevalence, abundance and seasonal incidence of gastro-intestinal (GI) nematodes and trematodes (flukes) of sheep and goats in the semi-arid zone of eastern Ethiopia. During May 2003 to April 2005, viscera including liver, lungs and GI tracts were collected from 655 sheep and 632 goats slaughtered at 4 abattoirs located in the towns of Haramaya, Harar, Dire Dawa and Jijiga in eastern Ethiopia. All animals were raised in the farming areas located within the community boundaries for each town. Collected materials were transported within 24 h to the parasitology laboratory of Haramaya University for immediate processing. Thirteen species belonging to 9 genera of GI nematodes (Haemonchus contortus, Trichostrongylus axei, T. colubriformis, T. vitrinus, Nematodirus filicollis, N. spathiger Oesopha-gostomum columbianum, O. venulosum, Strongyloides papillosus, Bunostomum trigonocephalum, Trichuris ovis, Cooperia curticei and Chabertia ovina), and 4 species belonging to 3 genera of trematodes (Fasciola hepatica, F. gigantica, Paramphistomum {Calicohoron} microbothrium and Dicrocoelium dendriticum) were recorded in both sheep and goats. All animals in this investigation were infected with multiple species to varying degrees. The mean burdens of adult nematodes were generally moderate in both sheep and goats and showed patterns of seasonal abundance that corresponded with the bi-modal annual rainfall pattern, with highest burdens around the middle of the rainy season. In both sheep and goats there were significant differences in the mean worm burdens and abundance of the different nematode species between the four geographic locations, with worm burdens in the Haramaya and Harar areas greater than those observed in the Dire Dawa and Jijiga locations. Similar seasonal variations were also observed in the prevalence of flukes. But there were no significant differences in the prevalence of each fluke species between the four locations. Overall, the results showed that Haemonchus, Trichostrongylus, Nematodirus, Oesophagostomum, Fasciola and Paramphistomum species were the most abundant helminth parasites of sheep and goats in eastern Ethiopia.

Multigeneric Resistance to Benzimidazole Anthelmintics in Sheep

Benzimidazole resistance involving several gastrointestinal nematode genera on a single sheep farm in New Zealand is reported for the first time. A controlled slaughter trial showed that at the recommended dose rate of 12.5 mg/kg, mebendazole had efficacies of 0, 60, 66, 90, 54 and 38% against Haemonchus contortus, Ostertagia spp., Nematodirus spp., intestinal Trichostrongylus spp., Strongyloides spp. and Oesophagostomum venulosum, respectively. The relevance of such multigeneric resistance to possible future options for controlling anthelmintic resistant sheep trichostrongylids is briefly discussed.