Detection of polymorphisms in the prion protein gene in the Belgian sheep population: some preliminary data.

The development of clinical signs of TSE/scrapie in sheep has been linked to polymorphisms in the prion protein (PRNP) gene. The most important polymorphisms appear to be at codons 136, 154, and 171. The objective of this study was to investigate the polymorphisms at these codons in the Belgian sheep population, including clinical healthy animals, healthy animals at the slaughterhouse and animals in TSE/scrapie positive farms (including a Nor98 farm).

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.

Biotype, serotype, and pathogenicity of attaching and effacing enteropathogenic Escherichia coli strains isolated from diarrheic commercial rabbits.

A total of 568 strains of Escherichia coli isolated from healthy and diarrheic rabbits were separated into 11 different biotypes according to the fermentation patterns of four carbohydrates. Strains belonging to biotypes 1 to 3, 6, and 8 induced lesions characteristic for attaching and effacing E. coli (AEEC). They attached to the intestinal epithelium of the terminal small intestine and the large intestine of 5-week-old rabbits after experimental infection and caused effacement of the microvillous brush border. However, pathogenicity for weaned rabbits, as judged by diarrhea score, anorexia, and reduced weight gain, varied according to the biotypes of the strains. Strains belonging to biotypes 1 and 6 produced only discrete clinical signs, strains belonging to biotypes 2 and 3+ (motile) induced diarrhea and growth depression, whereas strains belonging to biotypes 3- (immotile) and 8 caused severe clinical signs and high mortality. This confirms evidence from the field. Biotypes 3- and 8, accounting for 35.5 and 7.1% of AEEC strains in weaned diarrheic rabbits, respectively, were not detected in weaned healthy rabbits, while biotype 2 was the predominant strain in weaned healthy rabbits (62.3%). Finally, serotyping showed a close relationship between biotype and serotype of the AEEC examined. Most strains of biotypes 1+ and 2+ tested were O109:K-:H2 and O132:K-:H2, respectively, whereas all strains tested of biotype 3- were O15:K-:H- and those of biotype 8 were O103:K-:H2. These data indicate that specific clones of AEEC might be involved in juvenile rabbit enteritis. It was concluded that determination of biotypes allows the screening of highly pathogenic AEEC in weaned rabbits (biotypes 3- and 8).

Efficacy of toltrazuril against intestinal and hepatic coccidiosis in rabbits.

The anticoccidial effect of toltrazuril (Bay Vi 9142) against Eimeria flavescens, E. intestinalis, E. magna, E. perforans and E. stiedai was tested in experimentally-infected rabbits. Continuous administration of 10-15 p.p.m. of the drug in the drinking water was highly effective in reducing oocyst output of all five species and in preventing clinical signs and macroscopic lesions. Sporulation of excreted oocysts was not affected. After 5 weeks of medication, no negative influence was noted on zootechnic performance of growing healthy rabbits. Medication of rabbits with 25 p.p.m. only during schizogony or gamogony (2 days of treatment, repeated after 5 days) quickly reduced clinical signs and oocyst output. When administered during late schizogony or gamogony, toltrazuril allowed development of immunity against reinfection with homologous species.

Significance of Clostridium spiroforme in the enteritis-complex of commercial rabbits.

Commercial rabbits showing clinical signs of enteritis-complex were examined for the presence of Clostridium spiroforme and its iota-like toxin. The bacterium was detected by Gram stain in 52.4% of 149 cecal samples and iota-like toxin in 7.4%. From 29 strains of C. spiroforme tested, 26 were toxigenic, originating from 24 of 29 rabbitries. In 13.4% of the samples, C. spiroforme was present as the only known disease agent. Gross and microscopic lesions were similar to those described in the literature. In the other samples, C. spiroforme was associated with attaching effacing Escherichia coli (29.5%), Bacillus piliformis (10.3%), rotaviruses (25.6%), coronavirus (2.6%), Eimeria spp. (44.9%) and cryptosporidia (6.4%). In 33.3% of C. spiroforme-containing samples, more than one of these agents was present. There was no significant difference between the presence of these organisms in C. spiroforme-positive and negative samples. On the basis of these results as well as that of previous data, we suggest that C. spiroforme-mediated diarrhea is favoured by maldigestion, initiated by infectious agents and/or nutritional factors.

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.

Experimental Escherichia coli enteropathy in weanling rabbits: clinical manifestations and pathological findings.

Diarrhoea was reproduced by inoculating 5-week-old New Zealand White rabbits orally with 2 X 10(6) CFU of E. coli 0.15:H-. The strain produced diarrhoea in all the dosed rabbits 6.25 +/- 2.71 (mean +/- S.D.) days after infection (p.i.). Mortality was high. Sequential examination of the intestines by light microscopy showed the strain to attach first to the tips of the lymphoid follicle epithelium of Peyer's patches 24 h p.i., but not to other sites until 3 days p.i. From 3 to 14 days p.i. the strain caused an acute intestinal inflammatory response and large numbers of E. coli adhered to the enterocytes of ileum, caecum and colon. Colonized cells became rounded and were desquamated. Severe oedema of the caecal lamina propria was often present. Colonization of the intestine, as shown by rectal swab cultures, reached a maximum 4 to 7 days p.i. and did not decrease until 14 days p.i.

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.

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).