Comparative efficacy of six anthelmintics for the control of gastrointestinal nematodes in sheep in Matanzas, Cuba

Isolation of pure Trichostrongylus colubriformis strains from naturally infected sheep using two methodologies

Two methodologies were tested to isolate pure Trichostrongylus colubriformis strains from naturally infected sheep. Also, the in vitro susceptibility status to commercial anthelmintic (AH) drugs was determined in these strains. These methods were performed in a tropical region of Mexico where naturally infected sheep and goats host Haemonchus contortus, T. colubriformis and Oesophagostomum columbianum. For the first strain, a group of 6 naturally infected lambs from the "Paraiso" farm were treated with closantel (subcutaneous (SC), 10 mg/kg). On day 10 post-treatment, the eggs per gram (EPG) of faeces were determined with the McMaster technique. The faeces from the two lambs with the highest EPG were used for coprocultures (4 days, 28 °C). The L₃ larvae were recovered and identified as T. colubriformis (69%) and O. columbianum (31%). The latter was removed by 10-day refrigeration (4-5 °C) followed by sieving (25 μm), resulting in 100% T. colubriformis (PARAISO strain). The second strain was isolated using repeated doses of levamisole (LEV, SC 7.5 mg/kg) in an 8-year-old sheep. The sheep had 1700 EPG before the LEV treatments and maintained 1300 EPG after both LEV treatments (day 10). The coproculture (4 days, 28 °C) after the second treatment contained 100% T. colubriformis (FMVZ-UADY strain). The in vitro AH susceptibility was determined using the egg hatch test for benzimidazole (BZ), and the larval migration inhibition test for ivermectin (IVM) and LEV. The PARAISO strain was BZ- and LEV-susceptible, and IVM-resistant. Meanwhile, the FMVZ-UADY strain was BZ- and IVM-susceptible, and LEV-resistant. The conditions where these two protocols could be used in other parts of the world were discussed.

Acacia farnesiana pods (plant: Fabaceae) possesses anti-parasitic compounds against Haemonchus contortus in female lambs

Acacia farnesiana pods are rich in secondary metabolites and their biological activities have been recorded as antibacterial, antioxidant and anthelmintic. Previously, an in vitro bioguided study showed the important ovicidal and larvicidal effects of an organic fraction (EtOAc-F) from a hydroalcoholic extract of A. farnesiana pods against Haemonchus contortus. The present study aimed to assess the in vivo anthelmintic effect of EtOAc-F from A. farnesiana pods on the H. contortus faecal egg elimination in female lambs and on the infective larvae (L₃) population reduction in coprocultures. The EtOAc-F was obtained from a hydroalcoholic extract from A. farnesiana pods through chromatographic procedures; additionally, some secondary compounds were identified using high-performance liquid chromatography (HPLC). Twenty-one 'Katahdin' crossbred female lambs ranging from three to four months of age, with body weights 21.9 ± 0.39 kg were used. Animals were orally infected with H. contortus (L₃) by a single dose of 350 L₃/kg BW. Three experimental groups (n = 7) were assigned as follows: 1) Control (untreated), 2) Albendazole, as a positive control (at 7.5 mg/kg BW, unique dose) and 3) EtOAc-F (at 100 mg/kg BW, once every third day, with three applications in total). Individual faecal samples were collected once a week for 5 weeks (at days 38, 45, 52, 59 and 66) post-treatment, to measure the faecal egg counts (FEC) and to obtain the H. contortus (L₃) population from faecal cultures. The highest FEC reduction caused by EtOAc-F was 67.7%; meanwhile, albendazole showed a total FEC reduction after the second week post-treatment (day 45). On the other hand, the fraction caused an important reduction in the larval population in coprocultures (54.3-68.5%). The phytochemical analysis revealed the presence of galloyl derivatives and flavonoids as major compounds. The A. farnesiana pods could serve as a natural anthelmintic for the control of H. contortus, and perhaps for controlling other parasites of veterinary importance.

Effect of selective anthelmintic treatments on health and production parameters in Pelibuey ewes during lactation

A study was conducted from December to April 2013, with the aim of evaluating a system of selective antiparasitic treatments using the FAMACHA© color chart compared with a conventional suppressive deworming system every 30 days in Pelibuey ewes during lactation. For the study, 54 ewes were used. They were randomly divided into two groups: FAMACHA and chemical treatments. The ewes in the first group received selective treatment depending on the ocular mucosa coloration (FAMACHA) and body condition score (BCS), while in the second group (chemical) all the animals remained under routine deworming every 30 days. Fecal nematode egg counts, proportion of third-stage trichostrongylid larvae, body condition, coloration of the ocular mucosa, and packed cell volume in the ewes were determined, while in lambs only body weight (BW) was recorded. No significant differences (p > 0.05) were observed in any of the studied variables between groups; however, the use of antiparasitic drugs was reduced during the experimental period in the FAMACHA group and no deaths of lambs or ewes were recorded. The results indicate that during the lactation of ewes, a strategy of selective treatments can be implemented without showing deterioration in major health and productive parameters of these animals.

Anthelmintic resistance in sheep farms: update of the situation in the American continent

The present paper reviews the frequency of anthelmintic resistance in sheep farms in different countries of the American continent and describes some aspects that might influence the trend in sheep farms. The situation of anthelmintic resistance in sheep farms has been explored mainly in south of the continent (Argentina, Brazil and Uruguay) where sheep farming is an important industry. In those three countries, as well as in Paraguay, the first comprehensive surveys of anthelmintic resistance were performed among countries in the continent, which showed evidence of high frequency of sheep farms with anthelmintic resistance. Today, it is common to find sheep flocks with multiple-resistant worms. In North and Central America, a similar situation has been reported in sheep farms in the south of the United States of America, parts of Mexico and Costa Rica. On the other hand, other areas of the continent show low frequency of farms with anthelmintic resistance. From many areas no results have been published regarding situation on anthelmintic resistance or, alternatively, published results have received limited dissemination. Although the diagnosis of anthelmintic resistance is important for decision making of helminth management/control at the farm level, this is still an aspiration rather than a reality. For decades, researchers working on anthelmintic resistance in the American continent have expressed the need to change farmers' attitudes towards anthelmintic drugs. A common advice has been to check the anthelmintic drug efficacy regularly and reduce the dependence on these with alternative control measures. In spite of such advice, the challenge to stop/delay the advancement of anthelmintic resistance against the available anthelmintic drugs is still present. The evidence suggests that anthelmintic resistance is a growing phenomenon in the American continent. The situation described might be the tip of the iceberg, as anthelmintic resistance is still largely under-diagnosed. Hence, a different approach to tackle the advancement of anthelmintic resistance in sheep farms must be found. Awareness of farmers on the importance of diagnosis of anthelmintic resistance is not enough. Technical support schemes that provide the diagnostic service cheaply and timely must be implemented together with the research aiming at the adoption of control methods to reduce the dependence on conventional anthelmintic drugs. Unless these elements are readily available for producers, the negative consequences of anthelmintic resistance on sheep farming in America will continue to worsen with time.

Research and implementation of novel approaches for the control of nematode parasites in Latin America and the Caribbean: is there sufficient incentive for a greater extension effort?

The widespread presence of anthelmintic resistant gastrointestinal parasitic nematodes in outdoor ruminant production systems has driven the need to identify and develop novel approaches for the control of helminths with the intention to reduce the dependence on commercial anthelmintic drugs. This paper identifies what has been done in Latin America (LA) in terms of estimating the prevalence of anthelmintic resistance (AR) in ruminant production systems and the application of different novel approaches for the control of helminths in those systems, including research and extension activities. Firstly, the paucity of knowledge of AR is discussed in the context of different countries, as well as, the available economic resources for research, the technical infrastructure available and the practical difficulties of the production systems. It is then proposed that the search for novel approaches is not only driven by AR but also by the need for techniques that are feasible for application by resource-poor farmers in non-commercial subsistence farming systems. However, the commercial benefits of these approaches are often limited and so are funding inputs in most countries. The workers participating in the research into different novel approaches are identified as well as the different methods being studied in the different areas of LA according to their published results. In addition, the difficulties experienced during extension efforts to reach farmers and help them to adopt novel approaches for the control of parasitic nematodes in LA are discussed. The role of regulatory authorities in these countries is discussed as some methods of control might need an official confirmation of their efficacy as well as authorization prior to application as they may affect animal products (i.e. residues) and/or impose a hazard for animal welfare. The role of the pharmaceutical companies is also discussed.