Evolution of coccidial infection in commercial and domestic rabbits between 1982 and 1986.

Caecal samples were collected from 751 domestic rabbits of various origin and from 1229 diarrhoeic rabbits issued from 61 commercial rabbitries. They were screened for coccidiosis. In 1982, the year of introduction of the anticoccidial robenidine in commercial rabbit feeds, a dramatic decrease of coccidial infection ratio was detected in commercial rabbitries: only 6% of samples contained greater than 100 oocysts per gram against 85% in 1979, when sulphaquinoxaline/pyrimethamine was used. Only Eimeria magna, E. media and E. perforans were detected, whereas the highly pathogenic species E. flavescens and E. intestinalis had disappeared from commercial units. After 4 years of continuous use of robenidine, infection ratio rose progressively, although still far below the 1979 levels. Most of the other species reappeared, but only in very low proportions (1-4% of samples). The percentage occurrence of E. magna, E. media and E. perforans on the contrary rose progressively to 25, 26 and 34%, respectively, suggesting drug resistance. In domestic rabbitries, the incidence of coccidial infection was markedly higher and all nine species of Eimeria were detected. Eimeria magna, E. media and E. perforans were very common, E. flavescens, E. intestinalis, E. piriformis and E. stiedai were less common, whereas E. irresidua and E. coecicola were relatively rare. Notwithstanding the lower activity of robenidine against E. stiedai, no rise of hepatic coccidiosis became evident.

Naturally-occurring Tyzzer's disease (Bacillus piliformis infection) in commercial rabbits: a clinical and pathological study.

Tyzzer's disease has been detected in nine unrelated, commercial rabbitries. During the acute stage of the disease, recently weaned rabbits showed profuse watery diarrhoea. Mortality was between 14.2 and 41.2% during the first three weeks of the outbreaks. In surviving animals, there was a chronic evolution with depression, anorexia, loss of weight and sometimes extreme cachexia. Reproduction animals were less badly affected. Multifocal hepatic necrosis, focal myocardial necrosis, patches of mucosal necrosis in ileum, caecum and colon and marked caecal oedema were most prominent at autopsy. In histological sections of the liver, bundles of slightly Gram-negative and Giemsa-, PAS- and silver-positive rod-shaped bacilli were established in apparently viable hepatocytes bordering foci of necrosis. They were also present in myocytes around necrotic foci in the heart and in enterocytes and smooth muscle cells of the muscularis mucosae of the intestinal mucosa. Transmission electron microscopy showed that these organisms had a similar ultrastructure as Bacillus piliformis. Most antibiotics used failed to combat the disease. Only oxytetracycline was active.

Pathogenicity of attaching effacing enteropathogenic Escherichia coli isolated from diarrheic suckling and weanling rabbits for newborn rabbits.

The pathogenicity of six strains of Escherichia coli originating from different commercial rabbitries was tested in neonatal rabbits. Two strains isolated from healthy weaned rabbits (O7:H6 and O9:H?) did not induce any clinical sign or lesion. Two strains (O109:H2) isolated from diarrheic suckling rabbits caused yellow diarrhea 36 to 60 h after inoculation and high mortality between 60 and 72 h after infection. At 12 h after infection, light and electron microscopy showed attachment to epithelial cells and effacement of microvilli from proximal small intestine to colon. Bacteria were often present in the apical cytoplasm of epithelial cells. The two strains isolated from diarrheic weanling rabbits (O109:H2 and O15:H-) did not induce any clinical sign. Attachment to epithelial cells and effacement of microvilli was observed 48 h after inoculation in distal small intestine, cecum, and colon. These data are further evidence for the existence of two groups of attaching effacing enteropathogenic E. coli in rabbits, showing different preferences for age group and intestinal compartment.

Immunity and effect of clopidol/methyl benzoquate and robenidine before and after weaning on rabbit coccidiosis in the field.

For 15 months the anticoccidial effect of 200 ppm clopidol/methyl benzoquate and of 50 ppm robenidine, and the development of immunity against five different species of Eimeria were followed in a closed rabbit population. In unmedicated rabbits, oocyst output decreased progressively with increasing age to a very low level in animals older than four months, but none of the species present disappeared completely in adult animals. No clinical symptoms nor mortality from coccidiosis was noted in reproduction stock. In field conditions E magna and E perforans seemed to induce the weakest resistance, whereas a more marked resistance has been found for E intestinalis and E irresidua. E media appeared to have an intermediate position. Robenidine reduced oocyst output of E magna, E intestinalis, E irresidua, E media and E perforans significantly, whereas clopidol/methyl benzoquate reduced oocyst output of the latter four species only and was least active against E magna. Both drugs also reduced coccidiosis-induced mortality significantly. Medication only before weaning had no distinct influence on coccidial infection, or on mortality by coccidiosis after weaning; nor did those parameters differ significantly between continuously medicated rabbits and rabbits medicated after weaning only. As reproductive stock is protected by immunity, this makes the necessity of medicating does and bucks with anticoccidials questionable in intensive or semi-intensive reproduction systems.

Isolation of orthoreoviruses from psittacine birds.

Orthoreoviridae were regularly isolated from imported psittacine birds in the absence of other pathogens or in combination with salmonella. These viruses grew in embryonated eggs, in chicken embryo fibroblasts and in hepatic cell cultures. The viral isolates were classified as orthoreoviridae on the basis of their morphological and physico-chemical properties.

Enzyme-linked immunosorbent assay (ELISA) for detecting infectious laryngotracheitis viral antibodies in chicken serum.

The conditions of an indirect-enzyme linked immunosorbent assay for infectious laryngotracheitis virus (ILT) antibodies have been established. The specificity of the reaction was demonstrated. The method offers a simple and specific antibody assay for the detection of antibodies to ILT virus arising from vaccination or challenge infection.

Efficacy of narasin against hepatic and intestinal coccidiosis in rabbits.

The anticoccidial effect of narasin against Eimeria flavescens, E. intestinalis, E. magna, E. perforans and E. stiedai was tested in experimentally infected rabbits. The drug was highly effective in reducing oocyst output and in preventing clinical signs. Maximum activity as measured by oocyst discharge was achieved with feed levels from 12 to 24 p.p.m.; there was no influence on oocyst sporulation. Optimal weight gain and food consumption were obtained with levels between 8 and 12 p.p.m.; at higher levels there was an adverse effect on growth, food intake, relative liver and heart weights and on serum potassium and glucose.

Coccidiosis in rabbits: a field study.

During a survey 1052 faecal samples were examined in commercial and domestic rabbitries in Belgium. Nine different species of Eimeria were recognised. E magna, E media and E perforans were very common in both production methods. E flavescens, E intestinalis and E stiedai occurred more commonly in traditionally reared rabbits. E stiedai was not recorded in commercial rabbitries. E coecicola, E irresidua and E piriformis were less common. Oocyst output was suppressed in increasing efficacy by clopidol, sulphaquinoxaline/pyrimethamine (10:1), sulphadimidine and robenidine (P less than 0.01). The use of a droppings pit reduced the level of coccidial infection significantly compared with a sledge type of cleaning mechanism (P less than 0.001).

[Microscopic and ultramicroscopic lesions from experimental mycoplasma infection in respiratory tract of chickens. Possible difference between pathogenic and non pathogenic strains (author's transl)]. / Lésions microscopiques et ultramicrosopiques lors d'infection mycoplasmique expérimentale des voies respiratoires du poulet. Possibilité de différencier une souche pathogène d'une souche non pathogène.

For three weeks after experimental infection of trachea and scroll bone with Mycoplasma gallisepticum no lesions were detected in scroll bone, but only an abundant mucous secretion. Mycoplasmas were present and adhered to cilia of epithelial cells. In trachea an almost complete destruction of cilia was observed allowing swollen epithelial cells to appear with mycoplasmas adhering to villi. Strain W31 serotype C caused no lesions but cells and cilia were covered with a thick layer of mucous.

Field trial with the coccidiostatics metichlorpindol and robenidine in a rabbit farm.

The effect of metichlorpindol and robenidine in broiler rabbits was examined. Administration of 125 ppm metichlorpindol did not reduce mortality and oocyst output significantly. In comparison with unmedicated rabbits, weight gain of metichlorpindol medicated rabbits was 4.76% lower after seven seeks of treatment, whereas feed conversion was improved by 1.87%. There was no effect on the production index. Medication with 33 and 66 ppm robenidine resulted in a significant reduction of mortality and oocyst output (0.05 > P > 0.01). The effect on oocyst reduction became already significant after two weeks of treatment. After four weeks both robenidine medicated groups gained significantly (0.05 > P > 0.01) more weight than metichlorpindol medicated and non medicated rabbits. After seven weeks of medication only the 66 ppm medicated group gained significantly (0.05 > P > 0.01) more weight than the 125 ppm metichlorpindol medicated group. In comparison with non medicated rabbits weight gain was 3.46% better. Feed conversion was improved by 6.76 and 6.55% at 33 and 66 ppm levels respectively, while the production index was improved by 19% and 22% respectively in comparison with non medicated and metichlorpindol medicated rabbits.

Robenidine treatment of rabbits naturally infected with coccidia.

New Zealand White rabbits naturally infected with Eimeria intestinalis, E. magna, E. media and E. perforans and fed 100 parts/10(6) robenidine in their diet for 70 days ceased to excrete oocysts in their faeces after 19 days of treatment.

Haemagglutination-inhibition antibodies against EDS 76 virus in broilers.

Antibodies against EDS 76 virus were detected in 7-week-old broilers. No correlation could be found between their presence and a specific disease. Contaminated broiler flocks could however be a source of infection for laying chickens.

A comparison of three methods of diagnosis of infectious laryngotracheitis.

Three methods of isolation of ILT virus are compared. Examination of tracheas from sick birds by means of direct immunofluorescence detects about 60% of the cases detected by viral isolation in chick kidney cells or in embryonating eggs. The coupling of direct immunofluorescence on tracheal sections with viral isolation and immunofluorescence in CK cells is a good practical method to detect an ILT infection in sick birds.