Gastrointestinal helminthiases are considered among the dominant parasitic diseases encountered in ruminant farms; they do not only affect the production performance, but can also cause clinical signs: anaemia, reproductive disorders, decline in the quality and quantity of milk, growth retardation, delayed puberty and mortality (Sheferaw et al., 2013; Saidi et al., 2020; Maestrini et al., 2021). They are generally attributable to nematodes and cestodes (Nematodirus spp., Trichostrongylus spp., Teladorsagia circumcincta, Haemonchus contortus, Moniezia expansa, etc.) (Martínez-Valladares et al., 2015). Controlling these intestinal parasitic diseases is a crucial factor in optimizing animal production. Preventive anthelmintic chemotherapy remains the most widely used means of preventing these pathologies. The three classes of anthelmintics most commonly used in ruminants are benzimidazoles, macrocyclic lactones, and cholinergic agonists (in particular, levamisole) (Benguesmia et al., 2020; Potârniche et al., 2021). The excessive use of these anthelmintics can induce chemoresistance, especially since an increase in the resistance of gastrointestinal nematodes (to anthelmintics) has been reported in many countries in sheep and goats (Martínez-Valladares et al., 2015; Maestrini et al., 2021). In Algeria, few studies have been carried out on the resistance to anthelmintics in small ruminants; we can note, as an example, the study of Bentounsi et al. (2006), which demonstrated resistance of gastrointestinal nematodes in sheep to two benzimidazoles (albendazole, fenbendazole).
This study, conducted on ewes belonging to a farm located in the region of Guelma (north-eastern Algeria), aims to assess the resistance of gastrointestinal nematodes against two generics of albendazole and one of oxfendazole and this, by performing the Faecal Egg Count Reduction Test (FECRT): in-vivo test recommended by the World Association for Advance in Veterinary Parasitology (WAAVP) for the evaluation of the anthelmintic resistance in gastrointestinal strongyles in ruminants, horses and pigs (Coles et al.,1992).
The current study was conducted on a sheepfold in the neighborhood of Djeballa Khmissi, Wilaya of Guelma, northeastern Algeria, in late July and early August of 2018. The climate of this locality is semi-arid with a mean annual rainfall ranging between 450 and 600 mm. The sheepfold comprises 90 ewes of the Ouled-Djellal breed, aged between 2 and 5 years (mean age = 4.16 years), under semi-extensive breeding conditions. Animals were fed during late autumn, winter, and early spring with a concentrate consisting of corn, wheat bran, and barley. From summer until the beginning of autumn, the animals grazed on pastures. All animals are dewormed every 4 months with albendazole and ivermectin.
To assess the presence of nematode resistance to deworming, a total number of 45 ewes not dewormed for a little over 3 months were randomly divided into three batches (15 animals/group): animals of groups 1, 2 and 3 are dewormed respectively by albendazole (Al-Bendazol 2.5 % / Algérian Animal Health Product “AAHP”), albendazole (Valbazen®- Sheep and Goats / ZOETIS) and oxfendazole (OXFENIL® 2.265 % / VIRBAC).
On the first day, the animals in each of the three groups are given the appropriate anthelmintic (group 1 receives Al-Bendazol 2.5 % AAHP, group 2 receives Valbazen®, and group 3 receives OXFENIL® 2.265 %).
Faecal samples were collected in identified bags and sent to the laboratory on day 1 (just before treatment) and from day 10 to 14 after treatment. The modified McMaster method (Taylor et al., 1995) was performed to estimate the number of eggs per gram of faeces (EPG).
The percentage of egg reduction was estimated by the Faecal Egg Count Reduction Test (FECRT) as follows (Eysker et al., 2000):
The data were analyzed using the chi-square test in IBM SPSS Statistics (version 24) at a 5 % threshold.
The study was reviewed and approved by the local animal experimentation ethics committee at the University of Constantine-1.
Experimental and rearing conditions in this study comply with the animal welfare standards outlined by Oliver and Rossenrode (2017).
The EPG1 values in the three groups (before treatment) were very similar, ranging from 150 to 1,600 EPG. After treatment with anthelmintics, we observed a decrease in the number of gastrointestinal nematode eggs in the groups (Table 1). In group 1, the mean value of EPG1 was around 803; after treatment with “AL-Bendazol 2.5 %,” the number of nematode eggs per gram of feces decreased, reaching an average value of about 97 (EPG2). The average EPG1 value obtained in group 2 was around 450; deworming with Valbazen® reduced the excreted (in the faeces) number of digestive nematode eggs to an average value of around 50 (EPG2). The average OPG1 calculated in group 3 was approximately 353; the number of nematode eggs excreted in the feces after treatment with Oxfenil decreased to an average value of approximately 87 (EPG2) (Table 1). Resistance and sensitivity were observed in each of the three batches. In batch 1, resistance to “AL-Bendazol 2.5 %” was observed in 13 cases out of 15 ewes (86.67 %). In the second group, the number of cases demonstrating resistance to “Valbazen” was 10 out of 15 ewes (67 %). Group 3 reveals 13/15 (86.67 %) cases of resistance to “oxfendazole” (Table 2). The number of cases showing sensitivity to the used products was: 2/15 (13.33 %), 5/15 (33.33 %), and 2/15 (13.33 %), respectively, in groups 1, 2, and 3 (Table 2).
The Faecal egg count reduction and the number of eggs per gram of faeces (before and after treatment).
| Group* | Group 1 | Group 2 | Group3 | |
|---|---|---|---|---|
| EPG1 | Average ± SD | 803.3 ± 329.8 | 450 ± 275.2 | 353.3 ± 246.7 |
| Range (Mini – Max) | 150 – 1600 | 150 – 1050 | 150 – 1150 | |
| EPG2 | Average ± SD | 96.7 ± 66.7 | 50.0 ± 50.0 | 86.7 ± 71.2 |
| Range (Mini – Max) | 0 – 250 | 0 – 150 | 0 – 250 | |
| FECR1(%) S | Average ± SD | 100 ± 0 | 100 ± 0 | 100 ± 0 |
| Range (Mini – Max) | 100 – 100 | 100 – 100 | 100 – 100 | |
| Number of cases | 2 | 5 | 2 | |
| FECR2 (%) R | Average ± SD | 85.7 ± 7.1 | 81.9 ± 9.1 | 69.5 ± 19.0 |
| Range (Mini – Max) | 70.6 – 94.1 | 66.7 – 94.1 | 16.7 – 91.3 | |
| Number of cases | 13 | 10 | 13 | |
15 ewes in each group, EPG1: Number of Egg Per Gram of Faeces before anthelminthic treatment, EPG2: Number of Egg Per Gram of faeces after anthelmintic treatment, FECR1: Faecal Egg Count Reduction ⩾95%, FECR2: Average Faecal Egg Count Reduction < 95%, R: Resistant, S: Sensible, SD: Standard deviation
Resistance and sensitivity observed in the three tested groups.
| Group* | Sensitivity Number of cases (%) | Resistance Number of cases (%) | |
|---|---|---|---|
| Group 1 (AL-Bendazol 2.5%) | 2 (13.33%) | 13 (86.67%) | |
| Group 2 (Valbazen) | 5 (33.33%) | 10 (66,67%) | |
| Group 3 (Oxfenil 2.265%) | 2 (13.33%) | 13 (86.67%) | |
| p-value | |||
| (1 vs 2) | 0.344 | 0.874 | 0.591 |
| (1 vs 3) | 0.454 | 0.439 | 0.551 |
| (2 vs 3) | 0.069 | 0.507 | 0.283 |
The statistical comparison of the three products used did not reveal any significant difference in terms of deworming efficacy (Table 2).
Resistance of gastrointestinal nematodes to anthelmintics, particularly benzimidazoles, has been widely observed worldwide (Höglund et al., 2015). In our study, the resistance to albendazole (through the two specialties used) and to oxfendazole is observed, thus indicating a reduction in the effectiveness of these treatments in Egypt, Aboelhadid et al. (2021) found resistance to albendazole with an FECR of around 86.68 %. Bentounsi et al. (2007) also observed resistance of digestive strongyles to benzimidazoles in five pilot sheep farms located in eastern Algeria. The continuous and repeated use of albendazole in the farm has been studied for about 26 years (since the establishment of this farm). The relatively high frequency of treatment (three treatments per year), may have allowed the development of resistance to benzimidazole molecules including those used in this study (albendazole and oxfendazole), knowing that many authors attest that the intensive use of the same anthelmintic leads to the emergence of populations of nematodes resistant to the used molecule (Besier, 2007; Falzon et al., 2014). The problems in dosage errors, namely overdose and underdose, also represent an essential factor in the development of resistance, especially since in Algerian farms (cattle, sheep and goats) the evaluation of the dose of an anthelmintic is generally made by approximate visual weight estimate of the animal, which can induce an underdose or an overdose, allowing the selection of resistant helminths populations (Smith et al., 1999; Besier, 2007; Falzon et al., 2014).
The semi-intensive system of the studied farm ensures a continuous parasitic infestation of animals, favouring the development of eggs and the contamination of pastures for weeks, which increases the pressure of parasitic infestation on sheep. This can, in turn, increase the risks of selecting resistant populations (Nascimento et al., 2021).
For some authors, populations of resistant nematodes may be introduced into the land of a given country by herds of animals imported from another country. In Sweden, Höglund et al. (2015) observed the emergence of Haemonchus contortus populations resistant to ivermectin in certain sheep farms. The authors partly attributed this resistance to the introduction of resistant parasites via imported animals from Europe, where resistance to avermectins has been reported.
This study enabled us to observe the presence of resistance in digestive strongyles to anthelmintics, thereby corroborating previous observations by some authors, notably Bentounsi et al. (2006) and Boulkaboul et al. (2010), who had already reported the existence of resistance to anthelmintics in Algeria.
Albendazole is considered the most widely used anthelmintic in the Algerian field; this requires farmers to carry out correct management of their herds, based on respecting doses, alternating between families of anthelmintics, and not introducing resistant parasites into the herd (e.g., quarantine and association of anthelmintics).
This survey demonstrated the presence of resistance to benzimidazoles in gastrointestinal strongyles of sheep. Further studies on the effectiveness of other molecules from different families of anthelmintics should be pursued in the Algerian context. Specific analyses are necessary to determine nematode species who might exhibit chemoresistance.