Strategies to control internal parasites in cattle and swine

The complex relationship between livestock and their parasites is now much better understood. The pattern of infection and reinfection is a dynamic, but predictable, phenomenon that varies with geographic region, production system and grazing system used. Preventive programs that use anthelmintics offer the most efficient approach for grazing animals and confined species. Control strategies have been designed to prevent worm egg production and to limit parasite contamination and infection at critical periods in animal growth cycles.     

Use of praziquantel to control platyhelminth parasites of fish

Fish are common definitive and intermediate hosts for a variety of parasitic flatworms. In unstressed wild populations, parasitic infections often go unnoticed and are perceived to represent a lesser threat to fish health. In contrast, platyhelminth parasitism of captive fish often results in decreased weight gain and increased mortality which often necessitates chemotherapeutic treatment. The presence of platyhelminth parasites in fish tissues is not only unappealing but in some cases also represents a threat to human health. In veterinary medicine, one of the most commonly used agents with anti‐flatworm activity is praziquantel; yet, no praziquantel products are labeled for use in fish in the United States. Veterinarians may use praziquantel preparations approved for other vertebrate species under the Animal Medicinal Drug Use Clarification Act (AMDUCA). However, such extra‐label use should be informed by scientific evidence including efficacy and tissue residue studies. Herein, we review studies testing the efficacy of praziquantel for treatment of platyhelminthes along with an assessment of routes of administration, pharmacokinetics, and toxicity information.     

Novel approaches for the control of helminth parasites of livestock VI: summary of discussions and conclusions

Gastrointestinal helminth parasites impact on livestock production systems throughout the world, and the use of anthelmintics to control this problem has lead to the inevitable development of populations of helminths resistant to these treatments. This, coupled with consumer desires for minimal chemical inputs into food and fibre production, has prompted research into non-chemical approaches to helminth control. Scientists of the "Novel Approaches to the Control of Helminth Parasites of Livestock" group met for the 6th time in August 2010 and this paper summarises that meeting. Six scientific sessions addressed current approaches and topics of interest through formal presentations and discussion of issues raised by the contributing authors. Close interaction between researchers and extension specialists during the meeting has contributed to enhanced prospects for field application of research outcomes in the future.     

Epidemiology and control of parasites in warm climates

The kind of parasites a horse acquires depends upon its environment. Because patterns of transmission vary greatly with climate and management, no one worming program has universal applications. This article discusses epidemiology and control of equine parasites in the southern United States, where climates vary from warm temperate to subtropical and from humid in the southeast to arid in the southwest.     

Epidemiology and control of parasites in northern temperate regions

The serious and widespread problem of drug resistance has forced a re-thinking of basic philosophy regarding control of equine parasites. It has illustrated the dangers of total reliance on chemical control and stimulated the use of alternate strategies. Two new approaches are described. Prophylactic treatments in the spring and summer provide effective strongyle and colic control with less selection pressure for drug resistance. A nonchemical approach of pasture cleaning twice a week offers the same advantages with the added bonus of a 50 per cent increase in grazing area.     

鸡传染性支气管炎的控制方法

传染性支气管炎(Infectious Bronchitis,IB)是一个不可忽视的禽病。许多家禽都可感染本病,然而并不是所有的家禽养殖场主或生产者都知道本病的存在。由此可能会诱发其它疾病的爆发,造成一定的经济损失。     

Biological control of nematode parasites of small ruminants in Malaysia using the nematophagous fungus Duddingtonia flagrans

Control of nematode parasites of small ruminants in a wet, tropical environment using the nematophagous fungus, Duddingtonia flagrans, was assessed in this study. Two methods of fungal delivery were tested, namely as a daily feed supplement, or incorporated into feed blocks. Initially, pen trials were conducted with individually penned groups of sheep and goats at dose rates of 125,000 spores and 250,000 spores/kg live weight per day. At the lower dose rate this reduction was between 80 and 90% compared with the pre-treatment levels. At the higher dose rate, there was virtually complete suppression (>99% reduction) of larval recovery. Trials using the fungal feed blocks, showed that when animals were individually penned, they consumed only small amounts of the block (particularly goats), hence little effect on larval recovery in faecal cultures was observed. Grouping animals according to species and dose rate induced satisfactory block consumption and subsequent high levels of larval reduction in faecal cultures. These larval reductions were mirrored by the presence of fungus in faecal cultures. This work was followed by a small paddock trial, whereby three groups of sheep were fed either a feed supplement without fungal spores, supplement with spores, or offered fungal blocks. The dose rate of spores in the latter two groups was 500,000 spores/kg live weight per day. Egg counts were significantly reduced in the two fungal groups, compared with the control group and the latter required two salvage anthelmintic treatments to prevent mortality due to haemonchosis. Pasture larval numbers on the two fungal group plots were also much lower than on the control plot.     

The epidemiology and control of swine parasites. Immunity and vaccines

This article discusses the status of two experimental swine helminthic vaccines and how further knowledge of parasite biochemistry and swine immunology and the application of techniques of modern biotechnology may affect their future development.     

Responses in milk production to the control of gastrointestinal nematode and paramphistome parasites in dairy cattle

Objective To determine the effect of treating naturally acquired gastrointestinal nematode and paramphistome infections on milk production in dairy cattle.
Design A field trial.
Animals One thousand two hundred and thirty nine dairy cows.
Procedure Cows were either not treated or treated with 4.5 mg/kg oxfendazole, 16.6 mg/kg oxyclozanide or 4.5 mg/kg oxfendazole and 16.6 mg/kg oxyclozanide in March, May and August.
Results A significant increase in milk production, averaging 0.4 L (SE 0.2) per day, was seen when dairy cows infected with gastrointestinal nematodes and paramphistomes were treated with oxfendazole or oxfendazole and oxyclozanide in March, May and August. Cows treated with oxyclozanide alone at these times produced no more milk than untreated cows.
Faecal egg counts confirmed that oxyclozanide treatment reduced paramphistome populations and oxfendazole treatment reduced nematode populations in cows over the 7-month monitoring period.
Conclusion When dairy cows infested with gastrointestinal nematodes and paramphistomes were treated with oxfendazole alone or oxfendazole and oxyclozanide in March, May and August milk production increased.     

Management practices to control gastrointestinal parasites in dairy and beef goats in Minas Gerais; Brazil

Parasitic infection is recognized worldwide as a limiting factor in the production of goats, and various control methods are used to reduce economic losses, often without considering the epidemiology of the parasites. This has led to the development of highly tolerant parasite populations and the presence of chemical residues in the beef and milk. The objective of this study was to determine the level of knowledge of goat farmers about parasitic diseases and to correlate this with the epidemiology of endoparasites and parasite control practices in goat farms in the state of Minas Gerais, Brazil. The analysis was based on a questionnaire applied by trained veterinarians. The sample was homogeneous throughout the state, covering 18.4% (157/853) of municipalities. Eighty-four dairy goat farms in 81 municipalities and 200 properties with beef goats in 76 municipalities were evaluated. The herd size per goat farm ranged from 4 to 57 (average 24) for beef herds and from 2 to 308 (average 63) for dairy farms. The majority of the beef herd production was extensive and semi-extensive (98.5%), while the dairy herds were maintained under intensive farming (98.8%). The mixed production of goats and sheep was reported by 36.5% of beef goat farmers and by 20.2% of dairy goat farmers. Among the beef goats farms on which the technological level was determined, 2.0% were categorized as having high technological level, 34.5% as medium, and 63.5% as low. Of the 84 dairy farms, 30% operated at a high, 47% at a medium, and 23% at a low technological level. The adoption of practices to reduce parasitism, such as the quarantine of animals, treatment of newly arrived animals, regular cleaning of the floor, and technical assistance, was significantly higher on dairy farms than on beef farms. Although 85.7% of dairy farmers and 83% of beef farmers medicate their animals, the treatments were performed without technical criteria, and deworming intervals ranged from 30 to 120 days or more. The average interval between treatments was significantly longer in dairy goat herds (4.8 months) than in the beef herds (3.6 months). The most commonly used drugs were macrocyclic lactones (37.7% in dairy and 39.5% in beef herds) and benzimidazoles (48.9% in dairy and 31.5% in beef herds). Goat production in Minas Gerais is still in its infancy, and even though using a control program associated with other health practices, producers still rely heavily on chemicals to get satisfactory results.     

Epidemiologic approach to the control of sheep nematodes

Epidemiologic approaches to parasite control, with reduced reliance on the use of anthelmintics, were studied in 6 groups of weaned lambs and 4 groups of suckling lambs grazing fertilized pastures. Strategies tested included prophylactic treatments in the spring, provision of safe pastures, treat-and-move strategies, and winter (prelambing) treatment of ewes. Suppressive treatment with a non-benzimidazole drug was used as a production yardstick against which the epidemiologic approaches were judged. Suppressive treatment with a benzimidazole drug was used to determine the drug resistance status of the flock. The success of each strategy was evaluated by measurements of body weight, wool growth, fecal egg counts, pasture larval counts, and total worm burdens. Prophylactic treatments in the spring were just as effective as suppressive treatments throughout the entire grazing season and resulted in significant (P less than 0.001) increases in weight gain. Effective parasite control also was obtained by moving ewes and lambs to safe pastures (low infectivity) in May, and resulted in significant (P less than 0.001) increases in weight gain. A treat-and-move strategy led to significant (P less than 0.001) increases in weight gain until September, but then a loss of weight in October, suggesting the need for a double treat-and-move strategy in the case of late-marketed lambs. The value of winter (prelambing) treatments for ewes also was demonstrated. Suppressive treatments with a benzimidazole drug confirmed the presence of benzimidazole-resistant nematodes.