Gastrointestinal nematodes (GINs) of small ruminants have a world wide distribution (Martinez-Valladares
The most commonly used anthelmintics belong to three families:macrocyclic lactones (MLs), benzimidazoles (BZs), and imidazothiazoles (Cezar
Questionnaire surveys of worm-control practices are very useful for examining the methods of anthelmintic use and animal management (Cernanska
The aim of this study was to determined the prevalence of anthelmintic resistance and to identify the resistant species of parasitic nematodes on smallholder sheep farms in Lithuania. In addition, to evaluate management and treatment strategy on sheep farms the questionnaire survey was performed.
A questionnaire surveyed 71 sheep farmers. Twenty-nine farms were visited, and the farmers were interviewed personally. Forty-two sheep farmers from the list of the Lithuanian Sheep Breeders Association were interviewed by telephone. All farmers were asked about their practices of farm management: number of animals, sheep breeds, size of pastures, and worm-control practices: treatment times and frequency, products, and dosages of anthelmintic drugs. The surveyed farms were situated in western (12.7 %), central (40.8 %), and eastern (46.5 %) Lithuania. Because of the appropriate farm management and treatment strategy twenty five sheep farms from the questionnaire survey were selected for the further research.
A total of 25 sheep farms, mainly in central and southern Lithuania, were visited between April 2014 and November 2014. Eighteen of these farms were included in the study and seven were excluded due to faecal egg counts (FECs) <140 eggs per gram (EPG). Flocks were selected randomly and identified by GIN FECs. Faecal samples were collected from the rectums of 15 randomly selected animals in each flock and analysed using a modified McMaster technique, with a minimum sensitivity of 20 EPG (Roepstorff & Nansen, 1998). The selected flocks had been regularly treated with anthelmintics (Jackson
Sheep older than 18 months in each flock were divided into twogroups of 15 animals, marked with different coloured sprays, and treated with two different anthelmintics. The number of animals in each group was based on the recommendation that 10 animals per group were sufficient to detect differences in FECs between groups (Coles
where T2 is the arithmetic mean FEC post-treatment and T1 is the arithmetic mean FEC pre-treatment.
Post-treatment larval cultures were prepared from pooled faecal samples for the flocks with FECRT efficacies <100 %. The pooled samples were composed of the faeces collected from each animal of the group. Ten grammes of faeces were mixed with 4 g of vermiculite and incubated for 7 d at 27 °C (water was added to maintain an adequate moisture level). Third-stage larvae (L3) were then recovered from the coprocultures by a Baermann technique (Coles
differentiated and identified according to Maff (1986) and Van Wyk
The FECR and the lower limit for a 95 % confidence interval were calculated following the WAAVP recommendations (Coles
This study complied with Lithuanian animal welfare regulations (No. B1-866, 2012; No. XI-2271, 2012) and was approved by the Lithuanian Committee of Veterinary Medicine and Zootechnics Sciences (Protocol No.07/2010).
All farms were mainly specialized for meat production and practiced grazing, and 19.7 % of the farms had an ecological status. Rotational grazing was used on 78.3 % of the farms, and 21.7 % of respondents kept sheep on the same pasture with a shelter during the grazing period. Pastures had a mean area of 19.53 ha (1-120 ha). The average number of sheep per farm was 149.9 (1-1700). Lithuanian black-headed sheep was the dominant breed (46.5 %). Other breeds were Romanov (15.0 %), German black-headed (13.3 %), Suffolk (8.3 %), and Berichon du Cher (5.0 %). The remaining 11.9 % consisted of breeds such as Merinofleischschaf, Ile de France, Texel, and Lacaune and crossbreeds. Sheep were usually pastured from March/April to October/November, and all sheep were housed during the winter.
An estimated 71.8 % of sheep farmers used anthelmintics against GINs (Table 1), but 9.5 % of farmers declared that they treated their sheep only with the appearance of clinical symptoms such as diarrhoea, apathy and/or weight loss. The most commonly used classes of anthelmintics were MLs (68.6 %), and BZs (27.5 %). From the BZs group 68.7 % albendazole and 31.3 % FBZ were used. Levamisole was used very sporadically (3.9 %) (Table 1). Spring before turn out and autumn before turn in were the most common times to treat ewes. Yearlings and adults were usually treated together, with a mean annual drenching rate of 1.39. Most of the respondents declared that they treated lambs at the same time as the yearlings and adults to save time, with a mean number of treatments of 1.24 (Table 1). Of the respondents that used anthelmintics, 62.7 % declared that they treated their animals twice every year. All respondents that used anthelmintics once per year treated their ewes in spring. A few farms added a treatment in summer (7.1 %). Anthelmintics were rotated on 4.8 % of the farms. Only one respondent reported four treatments per year. Annual treatments were usually performed without any parasitological analyses, and 11.9 % of the respondents reported only a single coprological analysis during the entire period when sheep were kept. Animal weights were visually appraised on 92.9 % of the farms, and only 7.1 % of farmers weighed their animals. Veterinarians treated the animals on 54.8 % of the farms, and owners or farm workers treated the animals on 45.2 % of the farms. Problems with sheep GINs were declared by 39.2 % of the respondents.
Worm-control practices on the sheep farms
Worm-control factor | Number(%) |
---|---|
Macrocyclic lactones | 29 (56.9) |
Benzimidazoles | 8 (15.7) |
Imidazothiazoles | 2 (3.9) |
Macrocyclic lactones and benzimidazoles | 12 (23.5) |
None | 20 (28.2) |
Once | 7 (9.8) |
One to two times | 9 (12.7) |
Twice | 32 (45.1) |
Two to three times | 1 (1.4) |
Three to four times | 2 (2.8) |
None | 20 (28.2) |
Once | 16 (22.5) |
One to two times | 3 (4.2) |
Twice | 30 (42.3) |
Two to three times | 2 (2.8) |
The arithmetic mean FECs, percentages of the FECRs and 95 % confidence intervals are presented in Table 2. The FECRs indicated the presence of FBZ resistance on three of the 15 farms where FBZ was used (FECRs ranged from 44.9 to 85 %), and FBZ resistance was suspected on one farm (94.3 %, CI 93-99). Resistance to IVM was present on two of the 16 farms that used IVM (FECRs of 74.9 and 77.2 %). On one farm (Farm No.7) resistance was detected to both classes of anthelmintics. Mean pre-treatment EPG counts varied from 216 to 3114. The main species of resistant GIN identified after treatment were Teladorsagia spp. On all 6positive farms, with distribution varying from 42 to 100 %. Trichostrongylus spp. was found on five farms, with distribution varying from 4 to 100 %, and 6-56 % of the GINs on seven farms were Cooperia spp. Chabertia ovina was found on two farms (4-18 %), and Haemonchus contortus was found on only one farm (10 %) (Table 3).
Mean eggs per gram of faeces (EPG), faecal egg count reduction percentages (FECR%) and 95% confidence intervals (CI) on 18 sheep farms in Lithuania treated with fenbendazole (7,5 mg/kg) and ivermectin (0,2 mg/kg)
Farm no. | Anthelmintic class (drug) | EPG (range) pre – treatment | EPG (range) post – treatment | FECR% CI |
---|---|---|---|---|
1 | FBZ | 596 (160 – 1340) | 34 (0 – 140) | 94.3 (93 – 99) |
IVM | 300 (140 – 600) | 10 (0 – 100) | 96.7 (94 – 100) | |
2 | FBZ | 1346 (160 – 3540) | 26 (0 – 100) | 98.1 (97 – 100) |
IVM | 446 (160 – 1040) | 0 | 100 | |
3 | FBZ | 378 (140 – 1240) | 0 | 100 |
IVM | 415 (140 – 1080) | 0 | 100 | |
4 | FBZ | 544 (140 – 2120) | 82 (0 – 220) | 85 (73 – 98) |
IVM | 332 (140 – 1000) | 2 (0 – 20) | 99.4 (99 – 100) | |
5 | FBZ | 3114 (140 – 11720) | 120 (0 – 940) | 96.2 (95 – 100) |
IVM | 2843 (140 – 19760) | 0 | 100 | |
6 | FBZ | 264 (140 – 640) | 0 | 100 |
IVM | 267 (140 – 420) | 0 | 100 | |
7 | FBZ | 278 (140 – 620) | 68 (0 – 140) | 75.6 (66 – 85) |
IVM | 428 (160 – 1080) | 98 (0 – 520) | 77.2 (68 – 89) | |
8 | FBZ | n.d. | n.d. | n.d. |
IVM | 736 (140 – 3120) | 0 | 100 | |
9 | FBZ | 1366 (160 – 6680) | 0 | 100 |
IVM | 788 (140 – 2660) | 0 | 100 | |
10 | FBZ | 352 (140 – 1060) | 6 (0 – 40) | 98.3 (96 – 100) |
IVM | 216 (140 – 400) | 4 (0 – 40) | 98.2 (98 – 100) | |
11 | FBZ | 287 (140 – 620) | 0 | 100 |
IVM | n.d. | n.d. | n.d. | |
12 | FBZ | n.d. | n.d. | n.d. |
IVM | 388 (140 – 680) | 0 | 100 | |
13 | FBZ | 783 (140 – 2960) | 432 (60 – 1360) | 44.9 (31 – 56) |
IVM | n.d. | n.d. | n.d. | |
14 | FBZ | 414 (140 – 1100) | 0 | 100 |
IVM | 246 (140 – 560) | 0 | 100 | |
15 | FBZ | 2724 (140 – 15120) | 0 | 100 |
IVM | 1080 (160 – 3600) | 272 (0 – 2140) | 74.9 (65 – 84) | |
16 | FBZ | 223 (140 – 680) | 0 | 100 |
IVM | 1044 (140 – 6840) | 0 | 100 | |
17 | FBZ | n.d. | n.d. | n.d. |
IVM | 238 (140 – 760) | 0 | 100 | |
18 | FBZ | 725 (140 – 2680) | 0 | 100 |
IVM | 868 (140 – 3240) | 0 | 100 |
Telad.: Teladorsagia; Trich.: Trichostrongylus; Chab.: Chabertia; Haem.: Haemonchus; Coop.: Cooperia n.d.: not done
Third-stage larvae (L3) identified in post-treatment coprocultures on 6 sheep farms with AR in Lithuania treated with fenbendazole (7,5 mg/kg)and ivermectin (0,2 mg/kg)
Farm No | Anthelmintic class (drug) | Larval identification (% L3) post-treatment | |||||
---|---|---|---|---|---|---|---|
Trich. | Telad. | Chab | Haem. | Coop. | |||
1 | FBZ | 88 | - | - | - | 12 | |
IVM | - | 100 | - | - | - | ||
4 | BZ | 58 | 42 | - | - | - | |
IVM | 100 | - | - | - | - | ||
5 | FBZ | 40 | - | - | 10 | 50 | |
IVM | - | - | - | - | - | ||
7 | FBZ | 44 | - | - | - | 56 | |
IVM | 42 | 4 | 4 | - | 50 | ||
13 | FBZ | 52 | 28 | - | - | 20 | |
IVM | n.d | n.d | n.d | n.d | n.d. | ||
15 | FBZ | - | - | - | - | - | |
IVM | 54 | 22 | 18 | - | 6 |
Telad.: Teladorsagia; Trich.: Trichostrongylus; Chab.: Chabertia; Haem.: Haemonchus; Coop.: Cooperian.d.: not done
This study is the first to investigate the presence of AR in Lithuania. The number of sheep raised is increasing each year, and AR problems have begun to appear. This study demonstrated that AR to GINs in sheep occurs in Lithuania but to a lower extent than in Australia, New Zealand, South Africa, and other countries. AR in sheep varies widely in various countries of Europe. AR to BZs was found on 83 % of the sheep farms examined in western France (Chartier
The survey showed that a higher number of sheep farmers in Lithuania are using anthelmintics. Knowledge of AR, the prevalence of GINs, and proper usage of anthelmintics, however, is lacking. IVM is the most popular anthelmintic in Lithuania (68.6 %). FBZ is the only registered BZ in Lithuania, but farmers often choose albendazole from other countries because of its low cost and easy administration. Levamisole is used very rarely in Lithuania, as in other European countries (Cernanska
The most common feeding system with sheep is semi-intensive grazing on natural pastures, and housing and additional feeding are provided during winter. The pasture season in Lithuania lasts ca. 200 days. Our study indicated that the majority of farms keep Lithuanian black-headed sheep (46.5 %). The mean annual drenching rates were 1.24 and 1.39 for lambs and yearlings/ewes, respectively. Lambs and ewes were drenched 3.2 and 2.7 times per year in Scotland (Bartley
Visual appraisal of animal weight was based mostly on an average weight. Underestimation of real weights can lead to under-dosing, which can contribute to the development of AR (Chartier