Economic losses caused by the use of low-efficacy anthelmintic drugs in growing heifers.

The aim of this study was to compare the economic revenue related to the use of low- or high-efficacy anthelmintic drugs within suppressive or strategic schemes of treatment in growing heifers. Heifers raised in a semi-intensive grazing system in southern Brazil were used. Levamisole and ivermectin were selected as the high- and the low-efficacy drugs, respectively, based on a previous efficacy test. Subsequently, these drugs were used within strategic (Strat; four times per year) or suppressive (Supp; once a month) treatment regimens in the heifers, and their liveweight and eggs per gram of feces counts were monthly evaluated during a 13-month period. The total costs of the treatments and their cost-benefit ratio in regard to liveweight gain were calculated. Final mean liveweight gains (kg) observed were 126.7 (Strat-Low), 133.6 (Supp-Low), 141.3 (Strat-High), 142.9 (Supp-High), and 125.8 (Control). Treatments with a high-efficacy drug resulted in monetary gains of US$ 19.56 (Strat-High) and US$ 14.98 (Supp-High), but Supp-Low and Strat-Low treatments caused economic losses. Total cost of the efficacy test (US$ 374.79) could be paid by the additional liveweight gain of 20 heifers from the Strat-High group. These results showed that it would be preferable not to treat the heifers against GIN if compared with treating them with a low-efficacy drug. In addition, we showed that the use of four treatments per year with a high-efficacy drug-selected by efficacy test-resulted in a profitable management to control GIN in growing heifers raised in a semi-intensive gazing system in southern Brazil.

Prevalence, economic assessment, and risk factors of gastrointestinal nematodes infecting herds in tropical, dry and temperate climate regions in Mexico.

This study investigated exposure to gastrointestinal (GI) nematodes on dairy cattle farms by antibody level determination in bulk tank milk (BTM) samples and its influence on production to detect the risk factors for infection in different climate regions in three states of Mexico. From January to April 2017, BTM samples were collected from 1058 dairy cattle herds and used to establish three Köppen climate classes (tropical, dry and temperate) and states of Mexico. A questionnaire on farm management was applied. The overall herd prevalence of parasites was 67.20%. The highest percentage of positive herds was detected in Veracruz state (78.45%). In addition, the highest prevalence among the climate regions was found in the tropical climate (78.59%). In general, production losses were approximately 1.37-1.78 kg of milk/cow per day. The annual costs of milk production losses per farm were estimated for three different climate regions, ranging between $5541.49 and 6982.50 US$, and those in the three states varied between 5974.10 and 8660.06 US$. The costs for anthelmintic treatments for young stock and adult cows ranged between 57.51 and 192.75 US$, respectively, among the three climate regions and between 46.02 and 189.49 US$, respectively, among the three states. The overall annual costs of milk yield loss per cow were estimated to be 150.74 US$ for the climate regions and 190.54 US$ for the three states of Mexico, followed by the treatment costs for young stock (4.02 US$) and adult cows (3.99 US$). The results suggest that the economic losses due to GI nematodes in Mexican dairy herds are approximately 248 million US$ per annum. Four final models were built based on multivariate logistic regression for potential statistical association from the ELISA results using climatic/environmental and management factors so that each model used different risk factors that were significantly associated with helminth infections in dairy herds.

The economic effects of whole-herd versus selective anthelmintic treatment strategies in dairy cows.

Current control practices against gastrointestinal nematodes in dairy cows rely strongly on anthelmintic use. To reduce the development of anthelmintic resistance or disposition of drug residues in the environment, novel control approaches are currently proposed that target anthelmintic treatment to individual animals instead of the whole herd. However, such selective treatment strategies come with additional costs for labor and diagnostics and, so far, no studies have addressed whether they could be economically sustainable. The objectives of this study were to (1) investigate the economic effects at farm level of whole-herd versus more selective anthelmintic treatment strategies in adult dairy cows, and (2) determine how these economic effects depend on level of infection and herd size. A Monte Carlo simulation, fed by current epidemiological and economical knowledge, was used to estimate the expected economic effects and possible variation of different control strategies under Belgian conditions. Four treatment strategies were compared with a baseline situation in which no treatments were applied: whole herd at calving (S1), selective at calving with (S2) or without (S3) treatment of the first-calf cows, and whole-herd when animals are moved from grazing to the barn in the fall (housing treatment, S4). The benefit per lactation for an average dairy herd varied between -$2 and $131 (average $64) for S1, between -$2 and $127 (average $62) for S2, between -$17 and $104 (average $43) for S3, and between -$41 and $72 (average $15) for S4. The farmer's risk associated with any treatment strategy, as indicated by the width of the 95% credible intervals of economic benefit of anthelmintic treatment, decreased with increasing level of exposure, as assessed by bulk tank milk ELISA. The order of the different strategies when sorted by expected benefit was robust to changes in economic input parameters. We conclude that, on average, strategies applying anthelmintic treatment at calving outperform a strategy applying treatment at housing. Within the strategies that applied treatment at calving, more selective treatment strategies can be economically sustainable. However, given the large variation in possible benefits within each treatment strategy, decision support systems are needed to account for the multitude of cow, epidemiological, and economic factors that determine the economics of nematode control and select the optimal treatment strategy for a specific farm.

Effects of long-term indiscriminate use of macrocyclic lactones in cattle: Parasite resistance, clinical helminthosis, and production losses.

Our aims were to describe a case of clinical helminthosis caused by parasite resistance to macrocyclic lactones (MLs) after the long-term frequent use of these drugs in a cattle herd, and to evaluate the production losses prevented by the use of an effective anthelmintic treatment to control these resistant gastrointestinal nematodes (GINs). A case of clinical helminthosis culminating in the death of steers was investigated, the history of the antiparasitic treatments used during an 11-year period in the herd was assessed, and an efficacy test involving seven different drugs was performed. Thereafter, two groups of heifers naturally infected by ML-resistant GINs were formed and strategically treated with either a highly effective (levamisole) or less effective drug (doramectin) over a 9-month period. The heifers were evaluated monthly based on eggs per gram of feces (EPG) counts and liveweights. An evaluation of the history of parasite control in the farm revealed that MLs were used in 96.5% of the treatments aimed at controlling GINs, ticks, and myiasis in the herd. The efficacy test showed the presence of GINs resistance to all the MLs tested. However, levamisole and albendazole sulphoxide were highly effective against these parasites. Heifers treated with levamisole gained 12.1 kg more liveweight on average, compared to those treated with doramectin. Thus, we conclude that indiscriminate and long-term use of MLs in the studied herd led to the failure of GINs control, a critical situation resulting in significant production losses, and a surge of clinical helminthosis in young cattle. In addition, we showed increase in liveweight gain due to using a highly effective drug, in comparison to an ML, during a 9-month period, in heifers naturally infected by ML-resistant GINs.

Anthelmintic Drugs: Their Efficacy and Cost-Effectiveness in Different Parity Cattle.

Gastrointestinal nematodes are responsible for economic losses in bovines and are characterized by reduced milk production, decreased working efficiency, and even death. In our study, the effect of different anthelmintic treatments on nematode control in different parity cattle (Friesian crossbreds) at calving and their effect on milk yield were evaluated. The economics of anthelmintics and farm benefits in terms of increased milk production after deworming was also calculated. We screened cattle of first and second parity for nematodes. Animals were randomly selected in each group. In first parity animals, there were 23 positive cattle found, which were divided into 3 different groups, while in second parity animals there were 20 positive cattle which were also divided into 3 groups. For treatment of gastrointestinal nematodes, we used albendazole (velbazine) at 10 mg/kg body weight and levamisole (Nilverm®) at 7.5 mg/kg. In this study, both drugs were found effective in controlling nematode infections in cattle. Percentage reduction of eggs per gram (EPG) by albendazole was 48.20, 85.34, and 93.90% and 51.54, 81.43, 91.74% on day 7, 14, and 21 in first and second parity animals, respectively. Percentage reduction of EPG by levamisole was 44.45, 76.92, and 88.03% and 46.60, 73.78, 85.43% on day 7, 14, and 21 in first and second parity animals, respectively. The average increase in milk production in albendazole-treated groups was 0.39 and 0.92 L per day while increases in levamisole treated groups were 0.27 and 0.55 L per day in first and second parity cattle, respectively. After treatment, albendazole increased the milk fat by 0.07 and 0.1% while levamisole decreased by 0.02 and 0.05% in first and second parity cattle, respectively. It is concluded that anthelmintic treatments of recently calved cattle have a significant effect on milk production due to the nematode control. Milk production increased significantly in second parity cattle following anthelmintic treatment as compared to first parity animals. Levamisole had a negative effect on fat concentration in cattle while albendazole-treated cattle showed a positive effect. Albendazole has been found more efficient in reducing EPG of helminths in both parity animals as compared to levamisole-treated animals while the cost-benefit ratio of levamisole was greater than albendazole.

[An insight into the epidemiology and economic impact of gastro-intestinal nematodes in small ruminants]. / Nematodi gastrointestinali dei piccoli ruminanti: note di epidemiologia ed impatto economico.

Milk production has been a distinguishing characteristic of sheep breeding since antiquity in the Mediterranean area, including Italy, where prehistoric findings confirm this particular husbandry activity. In Homer's Odyssey, the description of Polifemo's sheep flock organization is remarkably similar to current production systems. The ancient roots of this tradition have grown into an important economic reality, with excellent levels of milk production and apporoximately 65 typical cheeses. It is interesting to note that the Italian word "pecora" (sheep) is believed to have originated from the Latin "pecunia" (money). Although heavy production losses are due to parasitic infections, only 250 papers have been published in the last 50 years in Italy on sheep parasites. Differences in climate, environmental factors and production tecniques may influence infection prevalence, load and pathogenesis. For this reason, prevention must be aimed at the particular epidemiological situation and not simply adapted from current schemes used abroad. The aim of this paper is to illustrate the epidemiology of ovine gastrointestinal nematodes in Italy and to evaluate the economic importance of their control.

Gastrointestinal nematode control programs with an emphasis on cattle.

Control strategies for nematode parasites rely on knowledge of the relationships between the parasites and their hosts. Specifically, these programs are based on identifying crucial points of interaction in the environment provided by the host, including genetics and the immune response, and critical periods in the physical environment in which the eggs and larval stages must develop. When these targets are identified and the interactions understood, cost-effective sustainable programs can be developed using currently available antiparasitic compounds. Resistance to the major classes of anthelmintic compounds requires consideration of new approaches, such as immunity or genetics of the host. Additionally, the efficacy of these compounds can be expanded with combined or concomitant use. Increased study of the use of novel approaches, including fungi, elements such as copper, and plant products, has also occurred. This article explores each of these areas to allow readers to appreciate how various approaches may be developed and incorporated into an effective parasite control program.

The relation between input-output transformation and gastrointestinal nematode infections on dairy farms.

Efficiency analysis is used for assessing links between technical efficiency (TE) of livestock farms and animal diseases. However, previous studies often do not make the link with the allocation of inputs and mainly present average effects that ignore the often huge differences among farms. In this paper, we studied the relationship between exposure to gastrointestinal (GI) nematode infections, the TE and the input allocation on dairy farms. Although the traditional cost allocative efficiency (CAE) indicator adequately measures how a given input allocation differs from the cost-minimising input allocation, they do not represent the unique input allocation of farms. Similar CAE scores may be obtained for farms with different input allocations. Therefore, we propose an adjusted allocative efficiency index (AAEI) to measure the unique input allocation of farms. Combining this AAEI with the TE score allows determining the unique input-output position of each farm. The method is illustrated by estimating efficiency scores using data envelopment analysis (DEA) on a sample of 152 dairy farms in Flanders for which both accountancy and parasitic monitoring data were available. Three groups of farms with a different input-output position can be distinguished based on cluster analysis: (1) technically inefficient farms, with a relatively low use of concentrates per 100 l milk and a high exposure to infection, (2) farms with an intermediate TE, relatively high use of concentrates per 100 l milk and a low exposure to infection, (3) farms with the highest TE, relatively low roughage use per 100 l milk and a relatively high exposure to infection. Correlation analysis indicates for each group how the level of exposure to GI nematodes is associated or not with improved economic performance. The results suggest that improving both the economic performance and exposure to infection seems only of interest for highly TE farms. The findings indicate that current farm recommendations regarding GI nematode infections could be improved by also accounting for the allocation of inputs on the farm.

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.

Control strategies for human intestinal nematode infections.

In recent years significant progress has been made in understanding the ecology, epidemiology and related morbidity and development of new tools for the control of soil-transmitted helminths. Such knowledge has recognized the impact of helminth infections on the health of infected groups and has created a rational basis for their control. Schoolchildren harbour some of the most intense helminthic infections, which produce adverse effects on health, growth and scholastic performance. However, although great effort has been put into targeting school-age children, women of child-bearing age and pre-school children are two other groups at high risk of morbidity due to intestinal nematode infections. Highly effective and safety-tested, single-dose anthelminthic drugs are now available, permitting periodical deworming of schoolchildren and other high-risk groups at affordable prices. Four anthelminthics against all intestinal nematodes are included in the WHO Essential Drug List (albendazole, levamisole, mebendazole and pyrantel). Recently ivermectin has also been registered for use against Strongyloides stercoralis in humans. Several well-monitored country experiences have shown that chemotherapy-based control of morbidity due to soil-transmitted helminths is possible and highly cost-effective.

Current research and future prospects in the development of vaccines against gastrointestinal nematodes in cattle.

Vaccination is being considered as the most feasible alternative for anthelmintic drugs to control gastrointestinal nematode infections in cattle. However, despite the identification of several candidate protective antigens, no vaccines against gastrointestinal nematode parasites are currently available. The main problems that hamper the development of nematode vaccines in ruminants are that vaccination with recombinant nematode proteins produced in bacterial or eukaryotic expression systems did not induce a protective immune response and no suitable antigen delivery system is available for presentation of protective worm antigens to the bovine mucosal immune system. The present review will focus on recent advances and remaining obstacles in vaccine development against gastrointestinal nematodes in cattle, in particular against the abomasal parasite Ostertagia ostertagi.

The cost of large-scale school health programmes which deliver anthelmintics to children in Ghana and Tanzania. The Partnership for Child Development.

It has been argued that the delivery of anthelmintics to school-children through existing education infrastructure can be one of the most cost-effective approaches to controlling parasitic worm infection. This paper examines the actual costs of a combination of mass and selective treatment for schistosomiasis using praziquantel and mass treatment for intestinal nematodes using albendazole, as an integral part of school health programmes reaching 80442 pupils in 577 schools in Volta Region, Ghana, and reaching 109099 pupils in 350 schools in Tanga Region, Tanzania. The analysis shows that financial delivery costs per child treated using praziquantel, which involved a dose related to body mass and a prior screening at the school level, were US$ 0.67 in Ghana and US$ 0.21 in Tanzania, while the delivery costs for albendazole, which was given as a fixed dose to all children, were US$ 0.04 in Ghana and US$ 0.03 in Tanzania. The higher unit costs in Ghana reflect the epidemiology of infection; overall, fixed costs were similar in both countries, but fewer children required treatment in Ghana. Analysis of economic costs-which includes the cost of unpaid days of labour--indicates that the financial costs are increased in Ghana by 78% and in Tanzania by 44%. It is these additional costs which are avoided by integration into an existing infrastructure. It is concluded that: the base cost of delivering a universal, standard, school-based health intervention can be as low as US$ 0.03 per child treated; that even a slight increase in the complexity of delivery can have a significant impact on the cost of intervention; and that the use of the education infrastructure does indeed offer significant savings in delivery costs.

Economics of gastrointestinal parasitism of cattle.

Understandably, cattle are raised for profit, as beef and/or dairy. Anything that negates that equation results in a loss to the producer and to the livestock economy. Thus, parasites negatively affect the economy of the industry. Worldwide, gastrointestinal nematode parasites, especially Ostertagia ostertagi, and those of the respiratory tract (Dictyocaulus viviparus) have a potentially major impact on herd health. In the past 10-15 years, anthelmintic (AH) drug development and the strategic use of AH have positively balanced the economic equation, so that overall, parasitism in cattle is often observed or determined to be subclinical or economical. Other control measures, such as better pasture management, are also being developed to enhance herd health and the cattle economy. The determination of the economic impact of parasitism has thus become less apparent, to the extent that measures, such as performance parameters, must be used to measure differences between treated and untreated animals or herds. These include weight gain, reproduction, lactation and forage use. To determine the effectiveness of control measures, field trials are designed to measure these parameters by the demonstration of improved performance. Because these trials are conducted in a competitive mode, results are often debated by competitors and by the scientific community because of study design. Variables must then be taken into consideration in the interpretation of results. It is now well known that, with the generation of new AH and appropriately-timed administration, parasitism of well-managed herds has been reduced to subclinical levels. Thus, we are now in the process of fine-tuning the positive effect of these control measures for enhanced production. Understandably, beef and dairy producers have 'production of high quality commodities' at a cost-effective level as a common goal. Successful cattlemen calculate expenditures and income by line item including veterinary expenses and cost and labor in administration of AH. Return is based on performance. Again, nematode parasites can disturb the equation enough to make production less profitable or even unprofitable. Most USA beef cattle producers believe that worm parasites do have an effect on cattle health and production so that 77% use AH and the market impact is that AH have become integrated into cattle herd health programs. However, to be most cost-effective, programs must be strategic but flexible with scheduling tailored for the region and the cattle operation. Other technologies should eventually provide rapid identification of worm populations by species and numbers and recognition of individual animal response to parasites and inheritance of that trait by their progeny. Computerized programs for analysis of seasonality of the epidemiology of gastrointestinal parasites and of herd performance could predict appropriate timing and cost benefit for control measures. Modes of AH administration are being developed which are more reliable and convenient in terms of delivery and labor. Control measures must also include better pasture management with less impact on the environment and to justify investment in land. In addition, successful producers are better educated, more cost-conscious, consumer-oriented, sensitive to the environment and attuned to the economics of parasitism.

Epidemiology and effects of nematode infections on beef cow-calf systems of Argentina's western pampas.

The epidemiology and the effects of nematode infections on cow-calf systems were followed from 3 weeks before calving to 7 months afterwards. Two groups, each of 15 cow-calf pairs grazed on separate lucerne pastures. Group I (GI) were treated monthly with oxfendazole (4.5 mg kg-1), cows being dosed from calving and calves starting 45 days later. Animals in Group II (GII) were not treated. The egg output of the cows was very low. An increase was recorded 2 months after parturition, consisting mainly of Ostertagia spp. The egg output and worm burdens of calves remained low until late summer and reached a peak in autumn. Ostertagia, Cooperia and Haemonchus were the main genera recovered from slaughtered calves. The pasture contamination and tracer calf worm counts remained consistently low until autumn when they began to increase. Inhibited early fourth stage larvae of Ostertagia were recovered during spring. After calving, the live-weight gains (LWG) of treated GI cows were significantly higher (P less than 0.004) than those of GII cows, whereas the LWG of GI calves were significantly higher during December (P less than 0.037) and March (P less than 0.029) than those of GII calves. There were significant (P less than 0.04) cumulative LWG responses between GI and GII calves with no differences in cow cumulative LWG at the end of the trial. For spring-born calves, these results suggest that strategic deworming programs in cow-calf systems may produce benefits.

Gastrointestinal nematodes of cattle in the northeastern US: results of a producer survey.

A questionnaire covering management practices and producer perception of the effects of gastrointestinal nematode infections was sent to dairy and beef producers in the northeastern US. The mailing list was derived from membership in grazing groups and attendance at grazing events. A final total of 474 responses were suitable for analyses. These responses covered 14 states, but for the purpose of analysis were broken into five groups: New England (NE), Vermont (VT), New York (NY), Pennsylvania (PA), and south and west (S and W) of Pennsylvania. Two-thirds of the responses were from dairy producers. The average number of animals for the farms was 50 cows, 27 heifers, and 20 calves. The average acreage used for grazing was 70 acres, and about two-thirds of the responses used rotational grazing for at least the cows. About one-half of the rotational grazers had been practicing rotational grazing for more than 5 years. Most rotational programs for cows involved a daily rotation, but the rotational interval for other age groups was longer. There was a difference of about 2 months (5.25-7.27) in the length of the grazing season as one moved from New England to south and west of Pennsylvania. Parasite control practices varied greatly by location and animal class. Most producers used anthelmintics one to two times per year, but 10-30% of responses said they did not deworm their cattle. The most common time to deworm was in the spring, and the second most common time was the fall. Between 10 and 20% of respondents reported deworming as a response to decreased productivity or body condition. The use of anthelmintics increased as the location moved from New England to south and west of Pennsylvania. Producer perception of parasite effects was closely related to their anthelmintic use, and also increased as the location moved to the south, and is most likely the result of the increased length of the grazing season. Of producers who ascribed estimated a cost of the parasite, the majority estimated this cost to be between US$ 5 and 20 per animal per year.

Influence of ivermectin and clorsulon treatment on productivity of a cow-calf herd on the southern Oregon coast.

The reproductive performance of beef cows and the weight gain of their calves was evaluated after oral administration of clorsulon or clorsulon in combination with the subcutaneous administration of ivermectin. One hundred and fifty pregnant cows harboring infections of Fasciola hepatica were assigned to one of three treatment groups: Group 1 comprising 50 unmedicated controls; Group 2, 50 cows treated with clorsulon orally at 7 mg kg-1; Group 3, 50 cows treated with clorsulon orally at 7 mg kg-1 and ivermectin subcutaneously at 200 micrograms kg-1. Weights and body condition scores of the cows were measured and fecal and blood samples were taken at trial initiation and days 158 and 270. Pregnancy status was also determined at day 270. Weights and body condition scores were measured for the calves at days 158 and 270. Adjusted 205 day weaning weight of the calves was calculated and analyzed for differences between treatment groups. Four sets of tracer calves were used periodically throughout the trial to monitor the helminth challenge to the herd. Both gastro-intestinal nematodes and liver flukes were transmitted to the tracer calves during the entire trial. Even in the face of continual helminth challenge, beef cows treated with combined clorsulon/ivermectin conceived approximately 2 weeks earlier than their untreated counterparts and their calves had better body condition scores and weights than untreated calves.

Losses to internal parasites in swine production.

Experimental infections of pigs with Strongyloides ransomi, Stephanurus dentatus, Ascaris suum, Oesophagostomum spp. or Trichuris suis at increasing levels generally decrease daily gain and increase feed to gain ratio linearly. At lower, subclinical levels of infection, the feed to gain ratio typically is increased 3% to 6% by an infection. Based on low-level experimental infections with A. suum, the economic loss to producers in the U.S. from increased feed to gain ratio is estimated at $155 million annually.

Economic evaluation of three anthelmintic strategies for lamb flocks affected by benzimidazole-resistant nematodes.

OBJECTIVE: To compare the profitability of three anthelmintic strategies in growing lambs in flocks with nematodes resistant to benzimidazole anthelmintics. METHOD: A partial-budgeting analysis was carried out by means of a stochastic simulation model, which allows inputs to be described as distributions rather than as fixed values, and hence permits variation between farms to be considered in the analysis. RESULTS: The results show that control of nematode parasites by use of an effective anthelmintic provides the highest net returns, yielding a margin over ineffectively treated lambs of A$114 per 100 lambs on average. Suppressive treatment based on the administration of two controlled-release capsules and monthly with moxidectin resulted in an average loss of A$131 per 100 lambs in comparison with animals treated with an ineffective anthelmintic. Analysis of the results from capsule-treated lambs did not take into account the unmeasured benefits associated with less contamination of pastures. Sensitivity analysis using a stochastic model indicates that apart from the effect of treatment on weight gain variation in carcase price greatly influences the profitability of all the parasite control programs examined. CONCLUSION: The results suggest that it is economically important for farmers to adjust their strategy in the presence of anthelmintic resistance. But as a result of uncertainty in the factors influencing economic return, the expected economic benefit is likely to vary substantially.

[Economic losses in pheasant breeding evoked with endoparasites]. / Ekonomiczne straty w hodowli bazantów wywolane pasozytami wewnetrznymi.

Parasitical invasions constitute a serious veterinary-economic problem in pheasant breeding. The studies were carried out between 1995-1997 in a big breeding centre situated in the Middle Pomerania region, where the basic flock amounted to 1000-1200 bird individuals. The aim of the study was to determine a condition of the pheasants' affliction with nematodes, reasons for the invasion and possibilities of a decrease in the losses thus brought about. In the subsequent years, the flock affliction reached the following proportions: 40% in 1995, 42% in 1996, and 68% in 1997. Between 1995 and 1996, the findings revealed eggs of the nematode Capillaria sp (C. anatis and C. phasianina) in their faeces, with less frequent cases of Trichostrongylus tenuis, Heterakis isolonche and Syngamus trachea. Between 1995-1996 40% deaths in the afflicted flock were brought about by Syngamus trachea whilst in 1997 syngamosis resulted in 80% deaths among the afflicted birds. To determine reasons for the confirmed nematode invasion in the studied period during which all the requirements were fulfilled in the pheasant breeding, conclusions were drawn on the basis of the study. Also, preventive measures were suggested to stop any further appearance of syngamosis or losses due to other endoparasites, as those in 1997.