An aspartyl protease inhibitor orthologue expressed by Parelaphostrongylus tenuis is immunogenic in an atypical host. (1/28)

Parelaphostrongylus tenuis is a neurotropic nematode common in white-tailed deer (Odocoileus virginianus) of eastern North America. This parasite is the causative agent of a debilitating neurologic disease in atypical hosts, including domestic livestock. In order to identify proteins of potential significance in the host-parasite relationship, a cDNA library was produced from adult P. tenuis mRNA. Screening the library with antisera from infected red deer (Cervus elaphus elaphus) and immunized AO strain rats, we identified clones with sequence similarities to aspartyl protease inhibitors from several parasitic nematodes. Antibody that was generated against this recombinant protein of P. tenuis (Pt-API-1) detected the native protein in E/S products, in muscle and gonad, and on the surface of the cuticle of adult male and female P. tenuis. The native protein was detected in internal structures of first-stage (L1) and third-stage (L3) larvae. Reverse transcription-PCR confirmed expression of Pt-api-1 in L1, L3, and adult male and female worms. Expression of Pt-API-1 throughout the life cycle of P. tenuis suggests an essential function. Antibodies specific for recombinant Pt-API-1 were detected by enzyme-linked immunosorbent assay in sera from 12 red deer experimentally infected with P. tenuis. Antibodies were detected within 28 to 56 days postinfection. Responses were sustained or biphasic in animals with patent infections, consistent with expression of Pt-API-1 by L1. Our results are compatible with findings in other parasitic nematodes showing that aspartyl protease inhibitors are highly immunogenic.  (+info)

Risk factors for high endoparasitic burden and the efficiency of a single anthelmintic treatment of Danish horses. (2/28)

A questionnaire survey regarding endoparasite control practices in Danish horse herds was carried out in 1995. The participating veterinarians and herd owners were sampled using convenience and purposive sampling. In the analysis of risk factors for development of a high endoparasitic burden (> 200 eggs per gram faeces) 903 horses were sampled and the analysis of the efficiency of a single anthelmintic treatment was based on 605 horses. The following factors had a significant effect on the endoparasitic burden: herd type, age of the horses, use of pasture rotation, anthelmintic treatment of horses visiting the herd, use of an adviser in the planning of endoparasite control and advice regarding pasture rotation. An interaction between pasture rotation and advice regarding pasture rotation was found, but due to high colinearity this was not reported. The factors influencing significantly on the reduction of the faecal egg count after a single anthelmintic treatment were the type of herd, the age of the horse, the drug used, and the anthelmintic-resistance-status of the herd. A negative effect of permanent pastures was observed. If pasture hygiene was performed on the advice of the veterinarian, the effect of a single anthelmintic treatment was less compared to a single anthelmintic treatment without any advice. An interaction between the treatment group and the resistance-status of the herd was found. Additional factors, normally accounted for, when endoparasites and anthelmintic resistance is discussed, were investigated, but not found significant in this study.  (+info)

Anthelmintic resistance in nematodes of horses. (3/28)

Suppressive anthelmintic treatment strategies originally designed to control Strongylus vulgaris in horses were extremely successful in reducing morbidity and mortality from parasitic disease. Unfortunately, this strategy has inadvertently resulted in the selection of drug-resistant cyathostomes (Cyathostominea), which are now considered the principal parasitic pathogens of horses. Resistance in the cyathostomes to benzimidazole drugs is highly prevalent throughout the world, and resistance to pyrantel appears to be increasingly common. However, there are still no reports of ivermectin resistance in nematode parasites of horses despite 20 years of use. It is unknown why resistance to ivermectin has not yet emerged, but considering that ivermectin is the single most commonly used anthelmintic in horses most parasitologists agree that resistance is inevitable. The fecal egg count reduction test is considered the gold standard for clinical diagnosis of anthelmintic resistance in horses, but diagnosis is complicated by lack of an accepted standard for the performance of this test or for the analysis and interpretation of data. Presently there is very little data available on the molecular mechanisms of anthelmintic resistance in cyathostomes; beta-tubulin gene is the only anthelmintic-resistance associated gene that has been cloned. The increasingly high prevalence of anthelmintic-resistant cyathostomes must be taken into account when designing worm control programs for horses. Strategies to decelerate further selection for drug resistance thereby extending the lifetime of currently effective anthelmintics should be implemented whenever possible. Considering the nature of the equine industry in which horses often graze shared pastures with horses from diverse locations, transmission and widespread dispersal of resistant parasites is virtually assured. A proactive approach to this problem centered on understanding the molecular basis of anthelmintic resistance in cyathostomes is required if we are to expect chemical control of nematodes in horses to remain a viable element of parasite control in the future.  (+info)

Recent developments in research into the Cyathostominae and Anoplocephala perfoliata. (4/28)

Intestinal helminths are an important cause of equine disease. Of these parasites, the Cyathostominae are the commonest group that infect horses. These nematodes consist of a complex tribe of 51 species, although individual horses tend to harbour 10 or so common species, in addition to a few rarer species. The Cyathostominae can be extremely pathogenic, and high levels of infection result in clinical symptoms ranging from chronic weight loss to colic, diarrhoea and death. As part of their life cycle, immature cyathostomins penetrate the large intestinal wall, where they can enter a state of inhibited larval development. These larvae can exist in this state for months to years, after which they subsequently re-emerge. If larvae re-emerge in large numbers (i.e. several million), severe pathological consequences ensue. The inhibited larvae are also relatively refractory to several of the currently available anthelmintics, so that horses treated previously with anthelmintics can still carry life-threatening burdens of these parasitic stages. Little is known about the cyathostomin larvae during their mucosal phase, and current research efforts are focused on investigating the biology of these stages. Much of the research described here highlights this area of research and details studies aimed at investigating the host immune responses that the mucosal larvae invoke. As part of this research effort, molecular tools have been developed to facilitate the identification of larval and egg stages of cyathostomins. These molecular tools are now proving very useful in the investigation of the relative contributions that individual, common cyathostomin species make to the pathology and epidemiology of mixed helminth infections. At the more applied level, research is also in progress to develop an immunodiagnostic test that will allow numbers of mucosal larvae to be estimated. This test utilises antigen-specific IgG(T) serum antibody responses as markers of infection. As anthelmintic resistance will be the major constraint on the future control of the Cyathostominae, researchers are now actively investigating this area and studies aimed at elucidating the molecular mechanisms of drug resistance are described. Another parasite which has assumed a clinically important role in horses is the tapeworm, Anoplocephala perfoliata. This parasite is prevalent world-wide and has been shown to be a significant cause of equine colic. Because previous methods of estimating the infection intensity of tapeworm were inaccurate, recent research has been directed at developing an immunodiagnostic ELISA for these cestodes. Specific IgG(T) responses to antigens secreted by adult tapeworms have been shown to provide a reasonable indication of infection intensity. An ELISA based on these responses is now commercially available. The steps involved in the development of this ELISA are described here. In addition to these recent advances in research, this review also outlines the principle areas for future research into these important equine parasites.  (+info)

Larval cyathostominosis in horses in Ontario: an emerging disease? (5/28)

From 1991 to 2003, 24 cases of larval cyathostominosis were diagnosed at postmortem in equids, 15 (63%) from 2001 to 2003. Cases occurred from September to May, the majority from October to December. Median age was 12 mo. Diarrhea, colic, and weight loss were common clinical signs. Hypoalbuminemia and microcytosis were consistent findings.  (+info)

Evidence of Parelaphostrongylus tenuis infections in free-ranging elk (Cervus elaphus) in southern Ontario. (6/28)

The antemortem detection of a Parelaphostrongylus tenuis infection in a free-ranging wild elk (Cervus elaphus) in southern Ontario is documented. Postmortems on other free-ranging elk that died during 2000-2005 indicated that 59% (17/29) were infected with P. tenuis, based on presence of lesions in the brain.  (+info)

The persistence of benzimidazole-resistant cyathostomes on horse farms in Ontario over 10 years and the effectiveness of ivermectin and moxidectin against these resistant strains. (7/28)

Three clinical trials with fecal egg count reduction tests and coproculture were conducted on 2 standardbred farms in Ontario. On Farm A, the treatment groups were mebendazole and ivermectin in trial 1, and fenbendazole and moxidectin in another. On Farm B, treatment groups were mebendazole and ivermectin. All horses treated with mebendazole or fenbendazole were subsequently treated with ivermectin or moxidectin. Strongyle eggs/g feces were estimated pre- and post-treatment using the Cornell-McMaster dilution and Cornell-Wisconsin centrifugal flotation techniques. After treatment, there was no change in the arithmetic mean eggs/g feces for horses given mebendazole, and a reduction of only 49.1% for those given fenbendazole. All horses receiving ivermectin or moxidectin had their egg counts reduced to 0. Only cyathostomes were found on culture. On both farms the benzimidazole resistant strains appeared to have persisted for at least 10 years. Development of and monitoring for anthelmintic resistance are briefly discussed.  (+info)

Check list of the helminths of equines in Turkey. (8/28)

Helminths of equines are one of the most important agents of parasitic diseases. Therefore, many studies have been conducted on helminths of equines in Turkey. In this article, a check list and prevalence rates of helminths of equines in Turkey have been given.  (+info)

• 1
• 2
• 3
• 4