Evaluation of targeted drenching using Famacha© method in Creole goat: Reduction of anthelmintic use, and effects on kid production and pasture contamination

Control of gastrointestinal helminths in small ruminants to prevent anthelmintic resistance: the Italian experience

Helminth infections are ubiquitous in grazing ruminants and cause significant costs due to production losses. Moreover, anthelmintic resistance (AR) in parasites is now widespread throughout Europe and poses a major threat to the sustainability of modern ruminant livestock farming. Epidemiological data on the prevalence and distribution of gastrointestinal nematodes, cestodes and liver- and rumen-flukes in Italian small ruminants are outdated and fragmentary. However, anthelmintics are commonly used to control these infections and often without prior diagnosis. Compared to other European countries, few reports of AR in small ruminants against levamisole, ivermectin and benzimidazoles have been published in Italy, but recent studies suggest that this phenomenon is spreading. Increased and integrated research efforts in developing innovative approaches to control helminth infections and AR are needed and must be tailored to the peculiarities of each context in order to be effectively implemented. This manuscript provides an overview on helminth prevalence and distribution, sustainable treatment strategies and integrated control approaches in small ruminants in Italy. The implementation of targeted treatments and targeted selective treatments is discussed based on different parameters, such as fecal egg count, degree of anaemia (FAMACHA© method), milk production and body condition score. In addition, several Italian studies have also investigated the implementation of alternative strategies such as the use of different natural bioactive compounds or genetic selection for resistance and resilience to helminth infections. These concrete solutions for helminth management in small ruminant farms in the country are reported and discussed, representing a valid example for other Mediterranean countries.

Low-cost molecular methods to characterise gastrointestinal nematode co-infections of goats in Africa

BACKGROUND

Veterinary diagnostics aid intervention strategies, track zoonoses, and direct selective breeding programs in livestock. In ruminants, gastrointestinal nematode (GIN) parasites are a major cause of production losses, but morphologically similar species limit our understanding of how specific GIN co-infections impact health in resource-limited settings. To estimate the presence and relative abundance of GINs and other helminths at the species level, we sought to develop a low-cost and low-resource molecular toolkit applied to goats from rural Malawi smallholdings.

METHODS

Goats were subjected to health scoring and faecal sampling on smallholdings in Lilongwe district, Malawi. Infection intensities were estimated by faecal nematode egg counts with a faecal subsample desiccated for DNA analysis. Two DNA extraction methods were tested (low-resource magbead kit vs high-resource spin-column kit), with resulting DNA screened by endpoint polymerase chain reaction (PCR), semi-quantitative PCR, quantitative PCR (qPCR), high-resolution melt curve analysis (HRMC), and 'nemabiome' internal transcribed spacer 2 (ITS-2) amplicon sequencing.

RESULTS

Both DNA isolation methods yielded comparable results despite poorer DNA purity and faecal contaminant carryover from the low-resource magbead method. GINs were detected in 100% of samples regardless of infection intensity. Co-infections with GINs and coccidia (Eimeria spp.) were present in most goats, with GIN populations dominated by Haemonchus contortus, Trichostrongylus colubriformis, Trichostrongylus axei, and Oesophagostomum columbianum. Both multiplex PCR and qPCR were highly predictive of GIN species proportions obtained using nemabiome amplicon sequencing; however, HRMC was less reliable than PCR in predicting the presence of particular species.

CONCLUSIONS

These data represent the first 'nemabiome' sequencing of GINs from naturally infected smallholder goats in Africa and show the variable nature of GIN co-infections between individual animals. A similar level of granularity was detected by semi-quantitative PCR methods, which provided an accurate summary of species composition. Assessing GIN co-infections is therefore possible using cost-efficient low-resource DNA extraction and PCR approaches that can increase the capacity of molecular resources in areas where sequencing platforms are not available; and also open the door to affordable molecular GIN diagnostics. Given the diverse nature of infections in livestock and wildlife, these approaches have potential for disease surveillance in other areas.

Review of Feeding Systems Affecting Production, Carcass Attributes, and Meat Quality of Ovine and Caprine Species

Growth rate, carcass attributes, and meat quality traits of small ruminants (i.e., sheep and goats) depend on various factors, among which the feeding system is one of the most important factors. However, how feeding systems affect these parameters differ between sheep and goats. Therefore, this review aimed to evaluate the differences in how different feeding systems affect the growth performance, carcass characteristics, and meat quality of sheep and goats. It also explored the effects of a new finishing strategy-time-limited grazing with supplements on these traits. Compared with stalled feeding, finishing lambs/kids on pasture-only feed reduced the average daily gain (ADG) and carcass yield, while supplemented-grazing lambs/kids had near-equivalent or higher ADG and carcass attributes. Pasture-grazing increased the meat flavor intensity and healthy fatty acid content (HFAC) of lamb/kid meat. Supplemental grazing lambs had comparable or superior meat sensory attributes and increased meat protein and HFAC compared to stall-fed ones. In contrast, supplemental grazing only improved the meat color of kids but had little effect on other meat qualities. Moreover, time-limited grazing with supplemental concentrates increased the carcass yield and meat quality in lamb meat. Overall, the effects of different feeding systems on growth performance and carcass traits were comparable between sheep and goats but differed in terms of the meat quality.

Farmers' Views and Tools Compared with Laboratory Evaluations of Parasites of Meat Goats in French West Indies

Gastrointestinal nematodes (GINs) are a major health problem in tropical goat husbandry. The control of GIN has been nearly exclusively reliant on the use of anthelmintic treatments. Their wide use has provoked the appearance and diffusion of anthelmintic resistance. Therefore, there is a need to use anthelmintics only when they are really needed. This strategy of targeted selective treatment (TST) has been recommended. The selection of animals to be treated has been based either on the objective measures of GIN intensity (fecal nematode egg counts) performed in the laboratory or on indirect assessment such as anemia (FAMACHA©), diarrhea score or weight gains, particularly in sheep. The roughness of hair has also been proposed in goats. These indicators can be handled by the farmer. Their opinion on the importance of GINs, and the indicators that they are ready to accept and use have very rarely been studied. Goat for meat production is important in the French West Indies (especially in Guadeloupe) and GIN infection may significantly alter this production. Eighteen farmers participated in semi-directive interviews in order to appreciate their relation to goat GIN infection and the solutions they considered. Seventeen farms were investigated for fecal nematode egg counts, FAMACHA©, body score, and roughness of hair. The average infection by GINs was high (average fecal egg count 1562 and standard deviation 2028) with a wide range from one farm to another (from 0 to 25,000 eggs of GIN per gram of feces). The Haemonchus genera was predominant (54%), followed by Trichostrongylus (37%) and Oesophagostomum (9%). Young goats were less infected than adult goats since they were not yet grazing; males were more infected than females; and the Creole breed was more infected than the other breeds. Among the farming types, the professional ones were less infected compared with the traditional or mixed agriculture and husbandry farms. Those using targeted selective treatment did not have a significantly higher GIN infection than those treating the whole herd. Most of the characteristics were related and multivariate analysis could not match the intensity of GIN infection with any parameter. The frequency of anthelmintic treatments was negatively related to the use of body score, FAMACHA©, and hair roughness. The use of semi-directive interviews provided a wider understanding of the strategies and problems of farmers. The farmers valued their animals very much and diseases, in general, were a preoccupation, whereas parasites were not a major issue for traditional farmers. This is due to the important use of indicators and the belief in their value that gives comfort to the farmers that the parasites are being controlled. The extension services have well diffused the practice of indicators to the goat farmers of Guadeloupe, with some depending less on anthelmintics to control the gastrointestinal nematodes by using targeted selective treatments.

Mixed grazing of adult goats and cattle: Lessons from long-term monitoring

Mixed grazing of breeding goats and cattle (goats to cattle ratio: about 50 %, based on metabolic weight) was monitored for 2 years on a rotational pasture with the two species grazing together, then for 5 years with cattle grazing immediately after goats. For both modalities, the level of goat parasite infection was not significantly different from that of the control groups. Nevertheless, the association allowed a slight improvement in kid growth and goat productivity, probably in relation to a better food quality. The response of adult goats to mixed grazing is therefore very different from that previously obtained with kids post-weaning. The question of the relationship between heterogeneity of pastures, knowledge of their environment, grazing behaviour of adult goats and risk of infection with gastrointestinal nematodes requires further investigation.

A multivariate approach to the diagnosis of gastrointestinal infection in ewes

Diagnosing the effects of helminth infections is an efficient way to manage the problem in ruminant production systems. Selection of animals in a flock that are infected with Haemonchus has traditionally involved differential packed cell volume measurements (PCV), and in recent years, the FAMACHA^© system has been used. However, few small analytical changes have been made. The objective of this study was to examine the influence of different diagnoses linked to packed cell volume (PCV) and FAMACHA^© system scores in native ewes, using a multivariate approach. Ewes were classified into three categories according to their score in the FAMACHA^© system (FS) and their packed cell volumes (PCV) as follows: Group AG (FS between 1 and 2 and PCV ≥ 30%); Group BG (FS score of 3 and PCV between 21 and 29%); Group CG (FS between 4 and 5 and PCV ≤ 20%). The animals were evaluated using performance characteristics, parasitological examinations, blood values and serum biochemistry. The data show that the use of a multivariate approach for different diagnoses using the FAMACHA^© system and PCV measurements gives similar results, although they have particular pathophysiological indicator patterns.

Sensitivity and specificity of the FAMACHA© system in growing lambs

The FAMACHA© system is used for targeted selective treatment (TST) of small ruminants for the control of haemonchosis. The aim of this study was to evaluate the sensitivity and specificity of this system in growing lambs. Between 2015 and 2016, lambs aged 60-210 days on two sheep farms were evaluated at 15-day intervals using the FAMACHA© system (F1-F5), with analysis of hematocrit (Ht), counting of eggs per gram of feces, and larval culture. The sensitivity and specificity of the system were calculated according to two criteria: criterion 1, lambs classified as F4 or F5 were considered anemic (positive test) and those classified as F1, F2, or F3 were considered not anemic (negative test); and criterion 2, lambs classified as F3, F4, or F5 were considered anemic (positive test) and those classified as F1 and F2 were considered not anemic (negative test). Three gold standard Ht cutoff values were used to diagnose anemia, i.e., ≤22%, ≤18%, and ≤15%. In total, 1591 assessments were analyzed. The highest percentage of larvae in the fecal cultures was for Haemonchus spp., with an average of 78.5%. The sensitivity values found when F3 lambs were considered anemic were 13.9%, 30.8%, and 66.7%, respectively, for Ht cutoff values of ≤22%, ≤18%, and ≤15%. When F3 lambs were excluded, the maximum sensitivity was 14.9% and the specificity was 100% for all degrees of anemia using criterion 1. The FAMACHA© system had low sensitivity in growing lambs and should not be used alone for control of haemonchosis in young animals.

An elaborated SIR model for haemonchosis in sheep in South Africa under a targeted selective anthelmintic treatment regime

Infection with the abomasal nematode Haemonchus contortus is responsible for considerable production loss in small ruminants globally, and especially in warm, summer-rainfall regions. Previous attempts to predict infection levels have followed the traditional framework for macroparasite models, i.e. tracking parasite population sizes as a function of host and climatic factors. Targeted treatment strategies, in which patho-physiological indices are used to identify the individuals most affected by parasites, could provide a foundation for alternative, incidence-based epidemiological models. In this paper, an elaboration of the classic susceptible-infected-recovered (SIR) model framework for microparasites was adapted to haemonchosis and used to predict disease in Merino sheep on a commercial farm in South Africa. Incidence was monitored over a single grazing season using the FAMACHA scoring system for conjunctival mucosal coloration, which indicates high burdens of H. contortus, and used to fit the model by estimating transmission parameters. The model predicted force of infection (FOI) between sequential FAMACHA monitoring events in groups of dry, pregnant and lactating ewes, and related FOI to factors including climate (temperature, rainfall and rainfall entropy), using a random effects model with reproductive status group as the cluster variable. Temperature and rainfall in the seven days prior to monitoring significantly predicted the interval FOI (p≤0.002), while rainfall entropy did not (p=0.289). Differences across the three groups accounted for approximately 90% of the variability in the interval FOI over the period of investigation. Maintained FOI during targeted treatment of cases of haemonchosis suggests strong underlying transmission from sub-clinically infected animals, and/or limited impact on pre-existing pasture contamination by removal of clinical worm burdens later in the grazing season. The model has the potential to contribute to the sustainable management of H. contortus by predicting periods of heightened risk, and hence to focus and optimise limited resources for monitoring and treatment. SIR-type model frameworks are an alternative to classic abundance-based compartmental models of macroparasite epidemiology, and could be useful where incidence data are available. Significant challenges remain, however, in the ability to calibrate such models to field data at spatial and temporal scales that are useful for decision support at farm level.

Diagnosis, Treatment and Management of Haemonchus contortus in Small Ruminants

Haemonchus contortus is a highly pathogenic, blood-feeding nematode of small ruminants, and a significant cause of mortalities worldwide. Haemonchosis is a particularly significant threat in tropical, subtropical and warm temperate regions, where warm and moist conditions favour the free-living stages, but periodic outbreaks occur more widely during periods of transient environmental favourability. The clinical diagnosis of haemonchosis is based mostly on the detection of anaemia in association with a characteristic epidemiological picture, and confirmed at postmortem by the finding of large numbers of H. contortus in the abomasum. The detection of impending haemonchosis relies chiefly on periodic monitoring for anaemia, including through the 'FAMACHA' conjunctival-colour index, or through faecal worm egg counts and other laboratory procedures. A range of anthelmintics for use against H. contortus is available, but in most endemic situations anthelmintic resistance significantly limits the available treatment options. Effective preventative programmes vary depending on environments and enterprise types, and according to the scale of the haemonchosis risk and the local epidemiology of infections, but should aim to prevent disease outbreaks while maintaining anthelmintic efficacy. Appropriate strategies include animal management programmes to avoid excessive H. contortus challenge, genetic and nutritional approaches to enhance resistance and resilience to infection, and the monitoring of H. contortus infection on an individual animal or flock basis. Specific strategies to manage anthelmintic resistance centre on the appropriate use of effective anthelmintics, and refugia-based treatment schedules. Alternative approaches, such as biological control, may also prove useful, and vaccination against H. contortus appears to have significant potential in control programmes.

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.

Mixed methods evaluation of targeted selective anthelmintic treatment by resource-poor smallholder goat farmers in Botswana

Due to the threat of anthelmintic resistance, livestock farmers worldwide are encouraged to selectively apply treatments against gastrointestinal nematodes (GINs). Targeted selective treatment (TST) of individual animals would be especially useful for smallholder farmers in low-income economies, where cost-effective and sustainable intervention strategies will improve livestock productivity and food security. Supporting research has focused mainly on refining technical indicators for treatment, and much less on factors influencing uptake and effectiveness. We used a mixed method approach, whereby qualitative and quantitative approaches are combined, to develop, implement and validate a TST system for GINs in small ruminants, most commonly goats, among smallholder farmers in the Makgadikgadi Pans region of Botswana, and to seek better understanding of system performance within a cultural context. After the first six months of the study, 42 out of 47 enrolled farmers were followed up; 52% had monitored their animals using the taught inspection criteria and 26% applied TST during this phase. Uptake level showed little correlation with farmer characteristics, such as literacy and size of farm. Herd health significantly improved in those herds where anthelmintic treatment was applied: anaemia, as assessed using the five-point FAMACHA(©) scale, was 0.44-0.69 points better (95% confidence interval) and body condition score was 0.18-0.36 points better (95% C.I., five-point scale) in treated compared with untreated herds. Only targeting individuals in greatest need led to similar health improvements compared to treating the entire herd, leading to dose savings ranging from 36% to 97%. This study demonstrates that TST against nematodes can be implemented effectively by resource-poor farmers using a community-led approach. The use of mixed methods provides a promising system to integrate technical and social aspects of TST programmes for maximum uptake and effect.

FAMACHA© system assessment by previously trained sheep and goat farmers in Brazil

The aim of this study was to evaluate the degree of adoption and the correct use of the FAMACHA© system amongst sheep and goat farmers trained in a previous hands-on course. A survey was carried out with 1375 people who received FAMACHA© training from July 2009 to May 2011 in Paraná State, Brazil. The survey was conducted from March 2012 to May 2013. Firstly, a questionnaire was applied with specific questions for farmers about their anthelmintic (AH) treatment practices before and after the FAMACHA© training. In a second step, eight of the questionnaire respondents classified as sheep or goat farmers were contacted for an in loco visit during which the application of the FAMACHA© system was evaluated in the respective farms and blood samples were collected from 20 animals to calculate sensitivity and specificity. A total of 124 farmers responded the questionnaire (9% of project participants). Farmers accounted for 48.4% of total responses. Half of these farmers (51.6%) reported losses related to parasites in their property before the training. Antiparasitic treatments, at fixed intervals, were responsible for 93.1% of deworming practices before the training project. FAMACHA© was unknown for 51.7% of the respondents, and 31% knew the chart, but did not use it. After the project, 69% had adopted the system and 83% assessed the animals at regular intervals. However, 18.9% did not evaluate all animals. During the in loco visits, problems reported included the incorrect exposure of the ocular mucosa (50% of farmers) and not using the chart (87.5%). Also, 62.5% did not keep records of the FAMACHA© assessment history of the flock. However, sensitivity was 100%, with 0% false negatives. We conclude that, amongst farmers who adopted the system, despite some methodological errors regarding its use, the objectives were met in terms of reducing the number of anthelmintic treatments and providing anemic animals with AH treatment. Trained farmers seemed to require technical guidance post-training to promote effective use of the FAMACHA© system.

Feasibility of a "leader-follower" grazing system instead of specialised paddocks with regard to integrated gastrointestinal control in small ruminant farming

In the humid tropics, small ruminant farmers have to deal with gastrointestinal parasitic nematodes (GIN), among which anthelmintic resistant (AR) populations are rapidly spreading. Although targeted selective treatments (TSTs) are being increasingly used in breeding stock, suppressive drenchings remain the rule in younger animals, for safety and ease of implementation. Until now, the weaned animals are grazed on dedicated plots, making the selection and spread of AR parasites inevitable. Given that GINs disseminate through pastures, we compared the usual grazing system (control) to a "leader-follower" grazing system (LF) for managing the entire GIN population at the farm scale. There were no significant differences between treatments for the dam reproductive parameters and level of GIN infection nor for the pre-weaning death rate of the kids. The 70-day weight of the litter was significantly lower for LF than for control goats (9.71 vs. 11.64 kg, P < 0.05). Although they were more infested with GIN (1860 vs. 966 epg, P < 0.05), the LF weaned animals grew faster (53.4 vs. 40.8 g day(-1), P < 0.05) and their death rate was lower (4.0 vs. 7.7 %, P < 0.05). The overall animal output was estimated to 1010 [911; 1086] vs. 966 [885; 1046] kg LW ha(-1) year(-1), for LF and control grazing systems, respectively. Additionally, the LF grazing system would make the stocking rate easier to manage. Therefore, it is to be recommended as a complement of TSTs in sustainable small ruminant farming.

Serum copper and haematological values of sheep of different physiological stages in the dry and wet seasons of central trinidad

A study was conducted to determine serum copper (Cu) concentrations and hematological values of 174 sheep from four medium sized farms, pertaining to physiological stage, in the late dry and late wet seasons of Central Trinidad. Serum Cu was significantly lower in the dry than in the wet season (P < 0.001) with a corresponding high percentage of samples with low Cu levels in the former. 31% of dry nonpregnant sheep exhibited a nonregenerative anaemia. Also, hemoglobin and packed cell volume values varied (P < 0.001) including lymphocyte (P < 0.01) counts, among growing animals compared with other physiological stages. Significant variations also occurred among neutrophil (P < 0.05) and eosinophil (P < 0.05) values in sheep. Highest haemoglobin and packed cell volume, white blood cell counts, and lymphocyte values in growing sheep compared with other stages were probably age related.

Simulated selection responses for breeding programs including resistance and resilience to parasites in Creole goats

The Creole goat is a local breed used for meat production in Guadeloupe (French West Indies). As in other tropical countries, improvement of parasite resistance is needed. In this study, we compared predicted selection responses for alternative breeding programs with or without parasite resistance and resilience traits. The overall breeding goal included traits for production, reproduction, and parasite resilience and resistance to ensure a balanced selection outcome. The production traits were BW and dressing percentage (DP). The reproduction trait was fertility (FER), which was the number of doe kiddings per mating. The resistance trait was worm fecal egg count (FEC), which is a measurement of the number of gastro-intestinal parasite eggs found in the feces. The resilience trait was the packed cell volume (PCV), which is a measurement of the volume of red blood cells in the blood. Dressing percentage, BW, and FEC were measured at 11 mo of age, which is the mating or selling age. Fertility and PCV were measured on females at each kidding period. The breeding program accounting for the overall breeding goal and a selection index including all traits gave annual selection responses of 800 g for BW, 3.75% for FER, 0.08% for DP, -0.005 ln(eggs/g) for FEC, and 0.28% for PCV. The expected selection responses for BW and DP in this breeding program were reduced by 2% and 6%, respectively, compared with a breeding program not accounting for FEC and PCV. The overall breeding program, proposed for the Creole breed, offers the best breeding strategy in terms of expected selection responses, making it possible to improve all traits together. It offers a good balance between production and adaptation traits and may present some interest for the selection of other goat breeds in the tropics.

Production systems of Creole goat and their implications for a breeding programme

The Creole goat is a local meat breed well adapted to the tropical environment of Guadeloupe, a French island in the Caribbean. A survey of 47 goat farmers was conducted in May 2008 to describe the Guadeloupean goat farming systems. It was the preliminary step for the implementation of a breeding programme for Creole goats. Farmers had 31 does on average. A small number (4%) kept only Creole goats. Most of them (62%) had a mixed herd of Creole and crossbreds. One-third of them (34%) reared only crossbred goats. Farmers appreciate the rusticity and resistance of the Creole goat but consider its growth as too slow. The most desired traits for goat selection were conformation and growth for males (77% of the answers). These traits were also important for females (30% of the answers). Maternal qualities were also frequently cited (maternal behaviour 23%, reproduction 20% and milk production 17%). Disease resistance was not seen as an important trait (10% and 7% of the answers for bucks and does, respectively). A typology constituted of five groups of farmers was also created. Farmers of three groups were retained to participate at a selection programme. They kept Creole goats and have expressed a strong willingness to join a selection programme. The results of the survey suggest that a breeding programme should mostly focus on the Creole goat as a maternal breed. Real consideration should be given to disease resistance. The Creole goat has indeed a key role to play in the sustainability of local farming systems.

Economic values of body weight, reproduction and parasite resistance traits for a Creole goat breeding goal

A specific breeding goal definition was developed for Creole goats in Guadeloupe. This local breed is used for meat production. To ensure a balanced selection outcome, the breeding objective included two production traits, live weight (BW11) and dressing percentage (DP) at 11 months (the mating or selling age), one reproduction trait, fertility (FER), and two traits to assess animal response to parasite infection: packed cell volume (PCV), a resilience trait, and faecal worm eggs count (FEC), a resistance trait. A deterministic bio-economic model was developed to calculate the economic values based on the description of the profit of a Guadeloupean goat farm. The farm income came from the sale of animals for meat or as reproducers. The main costs were feeding and treatments against gastro-intestinal parasites. The economic values were 7.69€ per kg for BW11, 1.38€ per % for FER, 3.53€ per % for DP and 3 × 10(-4)€ per % for PCV. The economic value for FEC was derived by comparing the expected profit and average FEC in a normal situation and in an extreme situation where parasites had developed resistance to anthelmintics. This method yielded a maximum weighting for FEC, which was -18.85€ per log(eggs per gram). Alternative scenarios were tested to assess the robustness of the economic values to variations in the economic and environmental context. The economic values of PCV and DP were the most stable. Issues involved in paving the way for selective breeding on resistance or resilience to parasites are discussed.

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.

Refugia-based strategies for sustainable worm control: factors affecting the acceptability to sheep and goat owners

Sustainable nematode management programs aim to minimise animal production loss and prevent parasitic disease, without increasing the level of anthelmintic resistance. Resistance management strategies are now largely based on the "refugia" concept, by which populations of nematodes not recently exposed to treatment are deliberately allowed to survive. Progeny from the unselected parasites provide a source of less-resistant worms which can dilute resistant worms surviving anthelmintics, and hence reduce the rate of resistance development. This can be achieved by either modifying strategic treatment regimens to ensure the survival of infective worm larvae on pasture, or by avoiding treatments to individual animals identified as best able to cope with parasites. These strategies include "targeted treatment" (based on estimates of worm-burdens) and "targeted selective treatment" (based on indications of parasitic effects). However, the departure from conventional anthelmintic approaches represents a major conceptual challenge to many livestock owners. Factors that may affect the wide adoption of refugia strategies include the increased risk of parasitism and production loss, the effectiveness of reducing the development of resistance, the practicality of implementation, and the direct effects on costs and labour efficiency. The acceptance of particular strategies is likely to vary considerably according to environmental effects, nematode species, animal production aims and resource availability. However, recent indications that comparatively small changes to present practices can provide substantial refugia benefits suggest that appropriate resistance management approaches can be developed for different situations.

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.

Control of endoparasitic nematode infections in goats

In 2007, the world goat population was estimated at 831 million, compared with 1.09 billion sheep, but the goat population is expanding more rapidly. More than 90% of goats are found in developing countries, with the primary commodity being its meat. The commonly used description of the goat as the "cow of the poorest" underlines its importance for small farmers. However, in the developed world (eg, the European Union and much of North America), the value of goats relates to its select ability to produce high yields of milk and the increased returns associated with the dairy products, particularly artisanal cheeses. Therefore, the current success of goats seems to be related to 2 characteristics: (1) its ability to efficiently convert low-quality forages into high-quality protein sources, that is, milk and meat, in developing countries and (2) its ability to produce commodities for valuable niche markets in developed countries. In both systems, parasitism with helminths, and particularly nematodes of the gastrointestinal tract is a major threat for health and production.

Application of ROC curve analysis to FAMACHA© evaluation of haemonchosis on two sheep farms in South Africa

Test sensitivity and specificity for the FAMACHA(©) clinical test for anaemia due to haemonchosis have previously been shown to be adequate in differentiating between heavily/less heavily infected sheep, but these properties give no objective guidance for setting the optimum threshold at which anthelmintic treatment should occur. The aim of this work was to use Receiver Operating Characteristic (ROC) curves to evaluate the diagnostic accuracy of FAMACHA(©) testing by estimating the area under the ROC curve, and to use two-graph ROC curves to decrease subjectivity in selecting treatment thresholds on two farms with contrasting management. Test diagnostic accuracy, and thus discriminating power as determined by the area under the ROC curves, ranged from "moderate to good" on the first farm, and from "moderate to high" on the second farm for haematocrit (the Gold Standard for the test) cut-offs of ≤ 22% and ≤ 19% on both farms respectively. Accuracy of classification between haematocrit cut-offs was not significantly different within farms, but did differ significantly between farms, with test accuracy being highest on the second farm at both haematocrit cut-offs (p<0.05). The results also showed the suitability of the two-graph ROC curve approach for discriminating not only between different levels of accuracy of evaluators, but also to give an indication of the so-called ROC cut point (i.e. the desired threshold level) at which animals should be treated for a given level of risk of loss. The approach appears to have the potential not only to validate the diagnostic accuracy of the test across the complete testing range (i.e. all FAMACHA(©) categories from 1 to 5), but also to compensate for such inaccuracy by allowing objective adjustment of the threshold treatment level according to the output of the two-graph ROC method.

Blueprint for an automated specific decision support system for countering anthelmintic resistance in Haemonchus spp. at farm level

This article is the first of a series aimed at developing specific decision support software for on-farm optimisation of sustainable integrated management of haemonchosis. It contains a concept framework for such a system for use by farmers and/or their advisors but, as reported in the series, only the first steps have been taken on the road to achieve this goal. Anthelmintic resistance has reached such levels of prevalence and intensity that recently it evoked the comment that for small ruminants the final phase of resistance was being entered, without effective chemotherapeutic agents on some farms with which to control worms at a level commensurate with profitable animal production. In addition, in the case of cattle, a recent survey in New Zealand showed 92% of worm populations to be resistant to at least one anthelmintic group. Ironically, new technology, such as the FAMACHA(©) system which was devised for sustainable management of haemonchosis, is at present being adopted relatively slowly by the majority of farmers and it is suggested that an important reason for this is the complexity of integration of new methods with epidemiological factors. The alternatives to the simple drenching programmes of the past are not only more difficult to manage, but are also more labour-intensive. The problem is further complicated by a progressive global shortage of persons with the necessary experience to train farmers in the new methods. The opinion is advanced that only computerised, automated decision support software can optimise the integration of the range of factors (such as rainfall, temperature, host age and reproductive status, pasture type, history of host and pasture infection, and anthelmintic formulation) for more sustainable worm management than is obtainable with present methods. Other than the conventional method (in which prospective analysis of laboratory and other data is mainly used to suggest when strategic prophylactic drenching of all animals for preventing excessive helminthosis should be conducted during the relevant worm season), the computer model being proposed is to be based on targeted selective treatment, supported by progressive periodic retrospective analysis of clinical data of a given worm season. It is emphasised that, in order not to repeat the mistakes of the past, such an automated support system should ideally be developed urgently in a attempt to engineer greater sustainability of any unrelated new anthelmintics which may reach the market.

The role of targeted selective treatments in the development of refugia-based approaches to the control of gastrointestinal nematodes of small ruminants

Anthelmintic resistance is recognised as a major problem affecting small ruminant production worldwide and now threatens the sustainability of many of these systems. One method that has been proposed to prolong the efficacy of our current anthelmintics is the maintenance of a parasite population in refugia (unexposed to a drug) which will maintain the genes for susceptibility within the parasite population. Management strategies that employ refugia-based methods include targeted or strategically timed whole flock treatments, targeted selective treatments (TST), whereby only a proportion of the flock is treated at any one time, and the dilution of resistant with susceptible parasites. The ability to effectively target anthelmintic use relies on the identification of those animals that will most benefit from treatment. This review explains the concept of refugia, describes the role of refugia-based approaches to the management of anthelmintic resistance and reviews the markers that have been studied as indicators for TSTs as well as the implementation of refugia-based strategies. Recent results suggest that targeting anthelmintic treatment on the basis of anaemia, milk production and liveweight gain may offer a means of reducing anthelmintic usage whilst still maintaining animal performance.

The use of targeted selective treatments against gastrointestinal nematodes in milking sheep and goats in Greece based on parasitological and performance criteria

This study compared the use of targeted selective treatment (TST) with systematic whole-flock treatments in 38 dairy sheep and goat farms in Greece. Criteria for individual treatments were either parasitological (nematode faecal egg count) or performance-based (body condition score or milk yield). The possible effect of treatment on resistance to benzimidazole anthelmintics was assessed using the Egg Hatch Test. Mean faecal egg counts decreased during the 12-month experimental period in all groups, and were lowest in the TST group treated according to faecal egg count (P<0.05). The number of sheep and goats treated by TST was reduced compared with systematic treatments. Mean thiabendazole-egg death dose(50) (TBZ-ED(50)) values from all groups were similar at the beginning and end of the study (P>0.05), but significant variation in TBZ-ED(50) was noted over the study period in systematically treated goats (P=0.045). Third stage larvae belonging to the genera Teladorsagia, Trichostrongylus and Haemonchus were dominant throughout the experimental period in all flocks. It was concluded that the use of targeted selective treatment reduced the number of anthelmintic treatments to achieve a similar level of parasite control or animal production and may offer a viable option to combine animal production with effective parasite control in Greece.