The prevalence and spatial clustering of Neospora caninum in dairy herds in Norway.

The aims of this study were to estimate the national herd prevalence and the general spatial distribution of Neospora caninum infection in Norwegian dairy cattle. Bulk milk samples from 1657 randomly selected dairy herds were analysed by iscom ELISA for the presence of N. caninum specific antibodies. The national herd prevalence was estimated to be 0.7% (95% CI: 0.3-1.2%), which is the lowest national herd prevalence reported in Europe. In addition, we included a subpopulation study in which all 400 herds in the Oslo, Akershus and Østfold counties were sampled, and we found a herd prevalence of 1.8%. In the national herd study, a significant cluster of N. caninum infected herds was identified in Jaeren, on the south west coast of Norway. Jaeren has the highest density of farm animals in the country as well as climatic conditions that favour parasite survival. Dairy herds in this region had a 52 times higher relative risk of being N. caninum positive than dairy herds in other parts of Norway. This indicates that even though N. caninum infection is of minor importance in Norway, infection might cause abortion problems in high risk areas.

Description of the infection status in a Norwegian cattle herd naturally infected by Mycobacterium avium subsp. paratuberculosis.

The Norwegian surveillance and control programme for paratuberculosis revealed 8 seroreactors in a single dairy cattle herd that had no clinical signs of Mycobacterium avium subsp. paratuberculosis (M. a. paratuberculosis) infection. Paratuberculosis had been a clinical problem in goats several years previously in this herd. All 45 cattle were culled and a thorough investigation of the infection status was conducted by the use of interferon-gamma (IFN-gamma) immunoassay, measurement of antibodies, and pathological and bacteriological examination. In the IFN-gamma immunoassay, 9 animals gave positive results, and 13 were weakly positive, while 19 animals were negative. In the serological test, 10 animals showed positive reactions, and 5 were doubtful, while 30 animals gave negative reactions. There appeared to be a weak trend toward younger animals having raised IFN-gamma and older animals having raised serological tests. Histopathological lesions compatible with paratuberculosis were diagnosed in 4 animals aged between 4 and 9 years. Three of these animals had positive serological reaction and one animal gave also positive results in the IFN-gamma immunoassay. Infection was confirmed by isolation of M. a. paratuberculosis from 2 of these 4 animals. One single bacterial isolate examined by restriction fragment length polymorphism (RFLP) had the same profile, B-C1, as a strain that had been isolated from a goat at the same farm several years previously. Despite many animals being positive in one or both of the immunological tests, indicative of a heavily infected herd, none of the animals showed clinical signs and only one cow was shown to be shedding bacteria. A cross-reaction with other mycobacteria might have caused some of the immunoreactions in these animals. It is also possible that the Norwegian red cattle breed is resistant to clinical infection with M. a. paratuberculosis.

Screening of feral pigeon (Colomba livia), mallard (Anas platyrhynchos) and graylag goose (Anser anser) populations for Campylobacter spp., Salmonella spp., avian influenza virus and avian paramyxovirus.

A total of 119 fresh faecal samples were collected from graylag geese migrating northwards in April. Also, cloacal swabs were taken from 100 carcasses of graylag geese shot during the hunting season in August. In addition, samples were taken from 200 feral pigeons and five mallards. The cultivation of bacteria detected Campylobacter jejuni jejuni in six of the pigeons, and in one of the mallards. Salmonella diarizona 14: k: z53 was detected in one graylag goose, while all pigeons and mallards were negative for salmonellae. No avian paramyxovirus was found in any of the samples tested. One mallard, from an Oslo river, was influenza A virus positive, confirmed by RT-PCR and by inoculation of embryonated eggs. The isolate termed A/Duck/Norway/ 1/03 was found to be of H3N8 type based on sequence analyses of the hemagglutinin and neuraminidase segments, and serological tests. This is the first time an avian influenza virus has been isolated in Norway. The study demonstrates that the wild bird species examined may constitute a reservoir for important bird pathogens and zoonotic agents in Norway.

Factors affecting the herd level of antibodies against Mycobacterium avium subspecies paratuberculosis in dairy cattle.

A case-control study was made of Norwegian dairy herds with high and low herd levels of antibodies against Mycobacterium avium subspecies paratuberculosis. A high proportion of the herds had a considerable number of seropositive cows, and environmental and management factors were examined for possible associations with the high serological levels of antibodies. The most important appeared to be: geographical location, red deer (Cervus elaphus) gaining access to the pastures for cattle, the observation of wild birds in the feed storage, and herds sharing common pasture with other herds of cattle. However, diagnostic tests showed that none of the animals in the case herds was infected with M a paratuberculosis.

A retrospective analysis of the infectious bovine rhinotracheitis (bovine herpes virus-1) surveillance program in Norway using Monte Carlo simulation models.

Serological surveillance for antibodies against bovine herpes virus type I (BHV-1) which causes infectious bovine rhinotracheitis and infectious pustular vulvovaginitis has been carried out since 1992 in Norway. Since 1993 (when a single infected herd was detected) all bulk-milk and pooled-serum samples have been negative for BHV-1 antibodies. This paper describes the use of Monte Carlo simulation models for the analysis and interpretation of the results of the surveillance and provides support for the contention that the Norwegian cattle population is not infected by BHV-1.

A simulated surveillance program for bovine paratuberculosis in dairy herds in Norway.

Monte Carlo simulation models were used to evaluate the feasibility and potential results of a proposed national survey of the prevalence of bovine paratuberculosis (PTB) in dairy herds in Norway. The expected herd prevalence was assumed to be 0.2% in the simulations. The low sensitivity of the ELISA test, the assumed low herd prevalence, the typical low within-herd prevalence of PTB and the small herd sizes all present problems in detection of the disease. Simulations with 500, 1000, 2500 and 6000 herds tested were done. Our results suggest that a national survey would not be feasible at present, due to the low probability of detecting infected herds and because of the high number of false-positive reactions that would be expected to occur.

Isolates of Encephalitozoon cuniculi from farmed blue foxes (Alopex lagopus) from Norway differ from isolates from Swiss domestic rabbits (Oryctolagus cuniculus).

Encephalitozoon cuniculi has a wide host range among mammals, but whether it represents a homogeneous species is a subject of controversy. We have isolated, cultivated (in human MRC-5 cells) and, for the first time, characterized by immunological and molecular biological methods four isolates of E. cuniculi from Norwegian blue foxes with a history of encephalitozoonosis. The isolates were compared with nine isolates from domestic rabbits from Switzerland. Two E. cuniculi subtypes were identified according to their host species. A 5'-GTTT-3' tetranucleotide repeat was present twice in the rDNA intergenic spacer in all isolates from foxes as opposed to three times in all isolates from rabbits. Furthermore, random amplified polymorphic DNA analysis showed one polymorphic band among the subtypes, and Western-blot analysis using serum from an infected fox discriminated between the two subtypes on the basis of their banding patterns in the ranges of 31-33 and 38-40 kDa. The 5'-GTTT-3' tetranucleotide repeat is a valuable genetic marker for these two subtypes of E. cuniculi and will be of use in continued studies on the molecular epidemiology of this parasite.

Effect of ovine urine and some of its components on viability of nematode eggs and larvae in sheep faeces.

Sheep faeces incubated for 7 days at 27 degrees C for cultivation of third-stage nematode larvae were sprinkled daily with urine from sheep or with solutions of components normally occurring in sheep urine. Larval development was completely blocked in cultures sprinkled either with sheep urine, with solutions of 2 or 4% urea, or with urine from which urea or the phenol components had been extracted. Only a few third-stage larvae developed in cultures sprinkled with 1% urea. Normal larval development occurred in cultures sprinkled with either the phenol component from urine, or with solutions of 0.035% phenol, 0.035% p-cresol, 0.3% allantoin, 0.3% hippuric acid or 2.8% NaCl. Normal larval development also occurred in all control cultures sprinkled with water, including one culture where there was urine in the space between the outer and inner beaker used for cultivation. It is suggested that the inhibitory effect of urine on larval development is mainly caused by ammonia produced when urinary urea is brought into contact with urease of faecal origin. It is, however, an unsolved question why urine, from which urea had been removed, also inhibited larval development.

The effect of periparturient treatment with fenbendazole on the milk production of cows.

Cows and heifers from 22 herds were used in a trial to determine the effect on milk yield of anthelmintic treatment given at calving. Alternate animals were treated with either fenbendazole suspension or a placebo. Cows given fenbendazole showed a mean reduction in milk yield of 221 kg in the subsequent lactation compared with the placebo-treated cows, a difference which was statistically significant. In heifers no significant effect of the treatment was found on milk yield. When looking at the pooled data from both cows and heifers, the reduction in milk yield of the fenbendazole-treated animals was 151 kg, which also was statistically significant. The results indicate that anthelmintic treatment of dairy cows cannot be generally recommended in Norway.

Trials with the morantel sustained release bolus in young cattle on nematode contaminated pasture, with treated and control animals grazed together.

The effect of the morantel sustained release bolus was studied in a group of first-season grazing calves kept together with an untreated control group. The groups were kept together to eliminate the uncontrollable influence of uneven nutritional conditions on weight gain when groups are kept on separate pastures. The calves were given one bolus just before turnout and a second three months later. In the treated calves, the number of nematode eggs in the faeces was kept on a low level during most of the grazing season, except for a slight rise in the egg counts after two months of pasture, before the second bolus was given. At the end of the 5 months' grazing period the live weight gain of the treated calves was 29.1 kg greater than that of the control calves (p less than 0.01), and the treated animals were in a far better condition than the untreated. The experiment showed that the MSRB prevented a significant weight loss due to gastrointestinal nematodes.

A field trial with albendazole against Dicrocoelium lanceolatum in sheep.

In a field trial a flock of 115 winterfed sheep were treated twice with a week's interval with albendazole at a dose of 10--12 mg per kg body-weight to test its efficacy against Dicrocoelium lanceolatum. The treatment was completed one week prior to mating in November, and the investigation was based upon monthly faecal egg counts throughout the housing period. The treatments showed about 90% reduction in the egg production of Dicrocoelium, and the gastrointestinal nematodes and Moniezia were eliminated. Side effects were not seen. The results indicate that albendazole could be recommended in cases of dicrocoeoliasis requiring treatment, as well as an efficient broadspectrum anthelmintic.