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Characterization of the microbial community colonizing the anal and vulvar pores of helminths from the hindgut of zebras.

Scanning and transmission electron microscopy were used to examine the adherence and in situ morphology of the microbial community colonizing the anal and vulvar pores of the subfamily Cyathostominae (Nematoda: Strongylidae) from the colon of Burchell's zebra (Equus burchelli antiquorum). Two different morphological types of asporogenous rod were prominent in the microbial community. One was a thin, septate, filamentous organism (0.4 to 0.5 micron by 2 to 3 microns) with blunt ends, which was more prominent at the site of attachment. The other was a larger (1.8 to 2.4 microns by 5 to 10 microns) multicellular rod with round ends in the form of a trichome. Spiral- and vibrio-shaped bacteria were also present in the thin sections. The septate filaments were shown to contain a cell spacer similar to those described in Methanospirillum hungatei. Attachment to the cuticle was by means of an amorphous electron-dense material with fibrillar appearance and not by specialized holdfast segments. Ten isolates were obtained from a habitat-simulating medium on which a homogenate from the posterior region was plated. Antibodies were raised to whole cells of five rod-shaped isolates in rabbits and fluorescein isothiocyanate labeled. Positive bright-yellow fluorescence was obtained with one of the clostridial isolates. The results are discussed with reference to other bacteria with similar morphology, the nature of this unique interrelationship between the microbial community and its parasitic host inside the equine hindgut, and the possibility of biological control of parasitic helminths.

Animals↗

An aspartyl protease inhibitor orthologue expressed by Parelaphostrongylus tenuis is immunogenic in an atypical host.

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.

Amino Acid Sequence↗

Angiostrongylus cantonensis: phospholipase in nonsensitized and sensitized rats after challenge.

Rats given an initial infection with Angiostrongylus cantonensis had moderately elevated phospholipase B activity in the lungs at 8 and 15 days after challenge, and greatly elevated levels were evident at 35, 43, and 49 days. In the brain, the values were elevated at 15 through 35 days. These periods of increased activity in the lungs and brain coincided with the migration patterns of the third stage larvae and the adult worms in this host. The elevated enzyme levels also were were correlated with increased numbers of eosinophils in the bone marrow at 8 and 15 days and again at 36, 43, and 49 days after infection. Similarly infected rats exhibited leukocytosis at 1 through 10 weeks of observation after challenge, and striking eosinophilia at 1, 7, 8, and 9 weeks. Rats reinfected after removal of the worms of the initial infection by thiabendazole treatment showed an anamnestic response characterized by (i) elevated enzyme values in both the lungs and brain at 1 day after reinfection and (ii) eosinophilia in the bone marrow by day 4. These accelerated responses were accompanied by a significant reduction in the worm burden of the rats. The results, which support our hypothesis that inflammation, elevated phospholipase B activity, and reduction in worm burden are causally related, are discussed in light of similar findings reported earlier from our studies with Trichinella spiralis and Nippostrongylus brasiliensis.

Animals↗

Parasite detection efficiencies of five stool concentration systems.

Fresh fecal material that was free of ova and parasites was pooled with 10% Formalin in a 1:4 ratio to prepare a standard specimen. Portions of 100 ml of this specimen were individually seeded with Cryptosporidium oocysts, Entamoeba coli, Entamoeba histolytica, and Giardia lamblia cysts; ova of Necator americanus; and Strongyloides larvae. Appropriate volumes of each parasite suspension were used to evaluate the Fecal Concentrator Kit (Remel, Lenexa, Kans.), Fecal Parasite Concentrator (Evergreen Scientific, Los Angeles, Calif.), Para-Pak Macro-Con (Meridian Diagnostics, Inc., Cincinnati, Ohio), and Trend FeKal CON-Trate (Trend Scientific, Inc., St. Paul, Minn.). A standardized gauze filtration method was used as the reference procedure. Tests were performed in triplicate with each individual parasite-concentrator combination, with three slides examined from each sediment. All of the systems effectively concentrated parasites compared with direct examination of unconcentrated fecal material. The Fecal Concentrator Kit provided the best overall performance. Clarity of sediment, lack of debris, and uniformity of background material were found to be important considerations for microscopic detection of parasites in concentrated specimens.

Animals↗

Case report of and description of parasite in Mammomonogamus laryngeus (human syngamosis) infection.

About 100 cases of human infections with Mammomonogamus laryngeus (Syngamidae, Syngaminae) have been reported, with virtually all cases originating in the Caribbean Islands and Brazil. This report describes the fifth patient in North America infected with M. laryngeus and the first case documented to originate in Jamaica. The patient complained of a characteristic persistent nonproductive cough and a lump in her throat. M. laryngeus is a nematode in which the male and female are permanently joined in copula, producing a distinctive Y shape. Since there is scant clinical information about this parasite, this report includes a description of the adult worms and eggs, a summary of the epidemiology, and the clinical manifestations in humans. Illustrations are presented to facilitate future identification of this parasite and to expedite treatment.

Adult↗

Haematological and biochemical values in horses naturally infected with Strongylus vulgaris.

The concentrations of serum proteins (beta 1, beta 2, gamma, alpha 1, alpha 2 globulins and albumin) and absolute numbers of eosinophils, neutrophils and lymphocytes were examined in 64 naturally infected horses and ponies in which the number of larvae of Strongylus vulgaris in the cranial mesenteric artery and the severity of the lesion of verminous arteritis could be determined. The horses were grouped according to the number of larvae found and the severity of the arteritis. The results demonstrated that, although some significant deviation from a random distribution occurred in certain of the values (chi 2 test), there was considerable individual variation in the values obtained for individual animals within groups and overlap of the range of values between groups. Also the number of larvae present in the artery did not necessarily accurately reflect the severity of the arterial lesion. Thus, the parameters examined could not be used reliably to estimate the intensity of infection with S vulgaris in an individual animal.

Animals↗

Efficacy of four anthelmintics against benzimidazole-resistant cyathostomes of horses.

In order to confirm benzimidazole resistance as recommended at a workshop of the Commission of the European Communities the isolate 'E' of cyathostome strongyles originating from a stud where benzimidazole resistance had been demonstrated by egg hatch tests and by egg count reduction tests was investigated in two series of critical tests. Each of 11 foals reared strongyle-free was infected with 130,000 third stage cyathostome larvae. One animal remained untreated, two pairs of foals were treated with paste formulations of the (pro)benzimidazoles cambendazole (20 mg/kg bodyweight) or febantel (6 mg/kg bodyweight) and two groups of three foals were given pastes containing the non-benzimidazole drugs pyrantel pamoate (19 mg/kg bodyweight) or ivermectin (0.2 mg/kg bodyweight) either at 101 days (trial 1) or at 59 to 62 days (trial 2) after infection. Strongyles were counted in faecal samples collected daily between treatment and post mortem examination five or seven days later and worm burdens were counted in the intestinal contents and mucosal digests. Nine species of the cyathostome subfamily were found in the infected foals. The numbers of luminal stages were reduced by only 3.1 and 20.2 (mean 7.9) per cent by cambendazole and by 13.6 and 32.8 (mean 21.3) per cent by febantel in the individual animals. However, pyrantel pamoate (93.6 to 98.2, mean 96.3 per cent reduction) and ivermectin (100 per cent reduction) were highly effective. These trials provide the first report of benzimidazole resistant Cylicostephanus poculatus anywhere in the world and demonstrate (pro)benzimidazole resistance in seven other species for the first time in Europe.

Animals↗

Prevalence of benzimidazole-resistance in equine cyathostome populations in south east England.

In order to study the prevalence of benzimidazole-resistance in equine cyathostomes, 30 stables in south east England were selected according to strict criteria but with minimum bias to provide three matched groups of 100 horses. One group was treated with fenbendazole, one with pyrantel embonate and the third was left untreated. The overall efficacies of fenbendazole and pyrantel embonate, as judged by the faecal egg-count reduction test, were 56.3 and 95.8 per cent, respectively. The numbers of horses at individual stables were too small to draw conclusions at each stable, but whereas efficacies greater than 85 per cent were recorded for pyrantel at 26 of 27 stables, the corresponding figure for fenbendazole was five of 27. Cyathostomes accounted for more than 90 per cent of the larvae cultured from faeces before and after treatment. Trichostrongylus axei was detected on 20 sites, but Strongylus species were present on only five. In the area of the survey, benzimidazole-resistance was very widespread in stables which used benzimidazole anthelmintics regularly and had more than nine horses per stable, but the benzimidazole-resistant cyathostome strains were adequately controlled with the non-benzimidazole anthelmintic pyrantel embonate.

Animals↗

Comparative studies of ivermectin and moxidectin in the control of naturally acquired cyathostome infections in horses.

The control of naturally acquired cyathostome infections in horses by treatments with ivermectin and moxidectin was evaluated in three field studies. In a first study the efficacy of both drugs was assessed in a faecal egg count reduction test. Both ivermectin and moxidectin demonstrated efficacies greater than 99 per cent for up to 60 days after treatment. In a second study, the period required for strongyle eggs to reappear was estimated in horses treated either with ivermectin or moxidectin. For the horses treated with ivermectin the period varied between 10 and approximately 13 weeks, and for moxidectin between 22 and approximately 24 weeks. With both drugs strongyle eggs started to reappear in the faeces significantly earlier in foals and young horses than in adults. In a third study, two prophylactic dosing schemes involving three ivermectin treatments at intervals of eight weeks, and two moxidectin treatments 12 weeks apart, were found to be highly effective in controlling strongyle infections of horses on pasture.

Animals↗

Efficacy of moxidectin 2 per cent gel against naturally acquired strongyle infections in horses, with particular reference to larval cyathostomes.

The efficacy of moxidectin 2 per cent equine gel against naturally acquired strongyle infections was assessed in 18 ponies which had grazed on contaminated pasture before being housed for eight weeks. Twenty-four hours before the treatment, two randomly selected ponies were euthanased and their worm burdens were determined. Eight of the remaining 16 ponies were treated with moxidectin 2 per cent gel while the other eight were given a placebo gel. Eight weeks later the 16 animals were necropsied and their worm burdens established. A 100 per cent efficacy was recorded against adult and lumenal L4 cyathostomes and adult Strongylus and Triodontophorus species. Digest recoveries of larval cyathostomes indicated a 90.8 per cent (P<0.002) reduction in early L3 and a 99.9 per cent (P<0.001) reduction in developing stages. There was a reduction in faecal egg output of between 96 and 100 per cent in the treated animals compared with the controls.

Animals↗