Factors associated with the success of rabies vaccination of dogs in Sweden.

BACKGROUND: United Kingdom, Ireland, Malta and Sweden maintain their national provisions for a transitional period regarding rules concerning rabies vaccination and individual serological test for rabies neutralizing antibodies. The purpose of vaccinating dogs against rabies is to establish pre-exposure immunity and protect individual animals from contracting rabies.The aim of the study was to investigate factors associated with reaching the internationally accepted threshold antibody titre of 0.5 IU/mL after rabies vaccination of dogs. METHODS: The study was a prospective single cohort study including 6,789 samples from Swedish dogs vaccinated with commercially available vaccines in Sweden, and the dog's antibody responses were determined by the OIE approved FAVN test. Information on potential risk factors; breed, age, gender, date of vaccination, vaccine label and the number of vaccinations, was collected for each dog. Associations between the dependent variable, serological response ≥ 0.5 IU/mL or < 0.5 IU/mL and each of the potential risk factors were investigated using logistic regression analysis. RESULTS: Of 6,789 vaccinated dogs, 6,241 (91.9%) had an approved test result of ≥ 0.5 IU/mL. The results of the multivariable logistic regression analysis showed that vaccinating with vaccine B reduced the risk of having antibody titres of < 0.5 IU/mL by 0.2 times compared with vaccination using vaccine A. Breed size was found significant as an interaction with number of vaccinations and age at vaccination as an interaction with day of antibody testing after last vaccination. In summary, larger breeds were at higher risk of having antibody titres of < 0.5 IU/mL but if vaccinated twice this risk was reduced. Moreover, there were a increased risk for dogs < 6 months of age and > 5 years of age to have antibody titres of < 0.5 IU/mL, but this was affected by number of days from vaccination till testing. CONCLUSIONS: The probability of success of rabies vaccinations of dogs depends on type of vaccine used, number of rabies vaccinations, the breed size of the dog, age at vaccination, and number of days after vaccination when the antibody titres are tested. The need for a booster vaccination regimen is recommended for larger breeds of dog.

Improvement and development of rapid chromatographic strip-tests for the diagnosis of rinderpest and peste des petits ruminants viruses.

This paper describes the improvement of a rapid diagnostic test for the detection of rinderpest virus (RPV) at pen-side and the development of a similar test for the detection of another Morbillivirus, peste de petits ruminants virus (PPRV). Using the Svanova Biotech format, prototype chromatographic strip test devices were developed for RPV and PPRV detection. For the RP device, the incorporation of a monoclonal antibody (Mab), which recognises additional RPV strains of RPV lineage 2, enhanced the range of reactivity of the rapid diagnostic test. The device detected antigen in animals infected experimentally with different RPV strains. It also showed detection levels similar to the RP Clearview™ device reported previously. In addition, RPV was also detected under field conditions in Pakistan. A PPRV specific Mab (C77) was used for the development of the PPR test. This Mab recognised a wide range of PPRV isolates and did not show any cross-reactivity with any other virus tested. In animal experiments the device was able to detect viral antigen in eye swabs taken from the animals. The PPRV test should be invaluable for future PPR control eradication programs.

Bovine spongiform encephalopathy in Sweden: an H-type variant.

Bovine spongiform encephalopathy (BSE) had never been detected in Sweden until 2006, when the active surveillance identified a case in a 12-year-old cow. The case was an unusual form, because several molecular features of the protease-resistant prion protein (PrP(res)) were different from classical BSE. The differences included higher susceptibility for proteinase K, higher molecular weight of the PrP(res) bands, affinity to the N-terminus-specific antibodies 12B2 and P4, and peculiar banding pattern with antibody SAF84 showing an additional band at the 14 kDa position. The molecular characteristics were in accordance to previous descriptions of H-type BSE. This report shows that a range of Western blot techniques and antibodies can be applied to confirm H-type BSE and further describes that the ratio of the amounts of PrPres#1 and PrPres#2, after deglycosylation, depends on the antibody used during processing. Immunohistochemistry on sections of medulla at the level of the obex applying antibodies with epitopes covering a broad range of the PrP sequence showed accumulation of disease-specific PrP (PrP(d)) in the gray matter. Fine punctate deposition in the neuropil was the most predominant type and was more severe in BSE target nuclei. The types of PrP(d) deposition are described in comparison with classical BSE. PrP-gene sequencing showed 6 copy octarepeat alleles and no abnormalities. It is postulated that the disease had a spontaneous origin, rather than having had been acquired in the BSE epidemic.

Characterization of equid herpesvirus 1 (EHV-1) related viruses from captive Grevy's zebra and blackbuck.

Equid herpes virus 1 (EHV-1) related isolates from a captive blackbuck (strain Ro-1) and Grevy's zebra (strain T965) behaved similarly to EHV-1 and EHV-9 in respect to their host cell range. Restriction enzyme analysis and a phylogenetic tree confirmed that Ro-1 and T965 were identical and more closely related to EHV-1 than to EHV-9. Differences from EHV-1 became obvious firstly, by amino acid alignments revealing two unique substitutions in the gB protein of Ro-1 and T965. Secondly, an EHV-1 type-specific monoclonal antibody did not detect its antigen on Ro-1, T965 or EHV-9 infected cells by immunohistochemistry. The results support the view that Ro-1 and T965 isolates represent a distinct, previously unrecognized species of equid herpesviruses.

Recovery of Swedish Equine arteritis viruses from semen by cell culture isolation and RNA transfection.

Recovery of infectious Equine arteritis virus (EAV) from the semen of persistently infected Swedish stallions was attempted by classical cell culture isolation and by transfection of extracted total RNA. Whereas virus from semen samples stored for several months at -20 degrees C or from extended semen could only be recovered by transfection of extracted RNA, isolation in cell culture was achieved readily with fresh, unextended semen stored at -70 degrees C or directly used after sampling. In parallel, the viruses were examined in the variable region of the large glycoprotein GP5 by nested RT-PCR and direct nucleotide sequencing. The resulting sequences were placed into a large phylogenetic tree from this region, demonstrating that Swedish strains belonged to very diverse phylogenetic groups. This represents the first report of recovery of infectious EAV from archived semen samples by RNA transfection.

Investigations into shaking mink syndrome: an encephalomyelitis of unknown cause in farmed mink (Mustela vison) kits in Scandinavia.

An apparently novel neurological disease clinically characterized by shaking, tremors, seizures, staggering gait, and ataxia was first observed in farmed mink kits in Denmark in 2000 and subsequently in Sweden, Denmark, and Finland in 2001, and again in Denmark in 2002. Lymphoplasmacytic encephalomyelitis was found in the affected kits. The lesions were most severe in the brainstem and cerebellum and consisted of neuronal degeneration and necrosis, neuronophagia, focal and diffuse gliosis, perivascular cuffs formed by lymphocytes, plasma cells and macrophages, and segmental loss of Purkinje cells. Testing was conducted to determine the cause of the disease, including general virological investigations (virus culture, negative-staining electron microscopy, immunoelectron microscopy, polymerase chain reaction for herpesviruses, adenoviruses, pestiviruses, and coronaviruses), tests for specific viral diseases (canine distemper, Borna disease, Louping ill, West Nile virus infection, tick-borne encephalitis, Aleutian disease), tests for protozoa (Toxoplasma gondii, Neospora caninum, Encephalitozoon cuniculi), bacteria (general culture, listeria, Clamydophila psittaci), and intracerebral inoculation of neonatal mice. The results of all these investigations were negative. One group of 3 mink kits inoculated intracerebrally with brain homogenate of affected mink developed clinical signs and histological lesions similar to those observed in naturally infected mink. Based on the histopathological features, it is postulated that the disease is caused by a yet unidentified virus.