Lena Renström

Prevalence of antibodies against feline coronavirus and Chlamydophila felis in Swedish cats

Serum samples from 214 Swedish cats with no signs of infectious disease were analysed for the presence of antibodies against Chlamydophila felis (Cp felis), while 209 of these were also analysed for feline coronavirus (FCoV) antibodies. The prevalence of antibodies against Cp felis was 11%, with no significant difference between purebred and mixed breed cats. The overall prevalence of antibodies against FCoV was 31%, significantly higher among pure breed cats (65%) than among mixed breed cats (17%). A high proportion of cats with antibodies against FCoV had relatively high antibody titres, and was therefore likely to be shedding FCoV in faeces. For Cp felis, the majority of seropositive animals had relatively low antibody titres, and the risk of these animals infecting others is not known.

Emergence of novel strains of avian infectious bronchitis virus in Sweden

Abstract Infectious bronchitis virus (IBV) causes avian infectious bronchitis, an important disease that produces severe economic losses in the poultry industry worldwide. Recent IBV infections in Sweden have been associated with poor growth in broilers, drop in egg production and thin egg shells in layers. The complete spike gene of selected isolates from IBV cases was amplified and sequenced using conventional RT-PCR. Nucleotide and amino acid sequence comparisons have shown that the recent isolates bear 98.97% genetic similarity with strains of the QX-like genotype. The phylogenetic analysis revealed that strains predominant in the nineties, which were of the Massachusetts type, have been replaced by D388/QX-like strains, however the evolutionary link could not be established. The homology between the two genotypes was 79 and 81%. Remarkably, a strong positive selection pressure was determined, mostly involving the S1 subunit of the S gene. This strong selective pressure resulted in recombination events, insertions and deletions in the S gene. Two new isolates generated from recombination were found with nucleotide sequence diverging 1.7–2.4% from the D388/QX-like branch, indicating the emergence of a new lineage. The study demonstrates a constant evolution of IBV that might be in relation to increased poultry farming, trade and vaccine pressure. The findings underscore the importance of continuous monitoring to control spread of infections, as well as to timely adjust diagnostic methods, molecular epidemiological studies, development and use of vaccines that are adapted to the changing disease scenario.

Complete genome characterisation of a Newcastle disease virus isolated during an outbreak in Sweden in 1997

The complete genome sequence of a Newcastle disease virus (NDV) isolated from a chicken in Sweden was determined and compared with other NDV sequences. The isolate was shown to belong to genotype VIIb, which arose in the Far East and spread around the world during the 1990s. It had a length of 15,192 bases and consisted of six genes in the order 3′-NP-P-M-F-HN-L-5′. The F protein cleavage site was 112-RRQRRF-117, corresponding to that of a virulent pathotype.

Evaluation of a commercial Erns-capture ELISA for detection of BVDV in routine diagnostic cattle serum samples.

BackgroundBovine viral diarrhoea virus (BVDV) is an important pathogen in cattle. The ability of the virus to cross the placenta during early pregnancy can result in the birth of persistently infected (PI) calves. These calves shed the virus during their entire lifespan and are the key transmitters of infection. Consequently, identification (and subsequent removal) of PI animals is necessary to rapidly clear infected herds from the virus. The objective of this study was to evaluate the suitability of a commercial Erns-capture ELISA, in comparison to the indirect immunoperoxidase test (IPX), for routine diagnostic detection of BVDV within a control programme. In addition, the effect of passive immunity and heat-inactivation of the samples on the performance of the ELISA was studied.MethodsIn the process of virus clearance within the Swedish BVDV control programme, all calves born in infected herds are tested for virus and antibodies. From such samples, sent in for routine diagnostics to SVA, we selected 220 sera collected from 32 beef herds and 29 dairy herds. All sera were tested for BVDV antigen using the Erns ELISA, and the results were compared to the results from the IPX used within the routine diagnostics.ResultsAll 130 samples categorized as virus negative by IPX were tested negative in the ELISA, and all 90 samples categorized as virus positive were tested positive, i.e. the relative sensitivity and specificity of the ELISA was 100% in relation to IPX, and the agreement between the tests was perfect.ConclusionWe can conclude that the Erns ELISA is a valid alternative that has several advantages compared to IPX. Our results clearly demonstrate that it performs well under Swedish conditions, and that its performance is comparable with the IPX test. It is highly sensitive and specific, can be used for testing of heat-inactivated samples, precolostral testing, and probably to detect PI animals at an earlier age than the IPX.

Characterization and analysis of the full-length genome of a strain of the European QX-like genotype of infectious bronchitis virus

In recent years, strains of infectious bronchitis virus belonging to the QX-like genotype have been causing huge economic losses in commercial chicken flocks in different countries in Europe. In order to expand the knowledge of the molecular features of these viruses, we have sequenced and characterized the complete genome of European QX-like IBV strain CK/SWE/0658946/10, which was isolated in 2010 in Sweden. The genome is 27664 nucleotides in length, comprising six genes and 5′ and 3′ untranslated regions. The ORF1a, spike and nucleocapsid genes were under strong positive selective pressure that resulted in genetic diversity in relation to classical IBV isolates. The full-length genome of the CK/SWE/0658946/10 strain has the highest nucleotide sequence identity (93.18%) to ITA/90254/2005 and the lowest nucleotide identity (89.10%) to strain CQ04-1. Phylogenetic analysis of partial S1 gene sequences of IBV strains showed that the European QX-like genotype comprises strains that have been predominantly circulating in this continent for the past decade.

Characterization of divergent and atypical canine coronaviruses from Sweden

SummaryField canine coronaviruses (CCVs) identified during a series of outbreaks of gastroenteritis in Swedish dogs were subjected to genetic analysis involving the open reading frame 1b (ORF1b) and the membrane (M) and spike (S) protein genes. Four field viruses originating from the Stockholm region presented identical sequences and segregated separately from other CCVs characterized so far and from GOT/05, the variant recovered in Western Sweden. A recombinant origin of the fifth virus identified in the Stockholm region is suggested. In addition, the five viruses originating from the same geographical area displayed atypical 5′ S gene sequences.

Whole genome sequencing and characterization of a virulent Newcastle disease virus isolated from an outbreak in Sweden.

In this study, the complete genome sequence of a Newcastle disease virus (NDV) isolate collected from an outbreak in 1995 in chickens was fully characterized and compared with other NDV sequences. The genome was found to be 15,192 nucleotides long and to consist of six genes in the order 3′-NP-P-M-F-HN-L-5′, similar to other avian paramyxoviruses type-I. However, a six-nucleotide insertion was observed in the 5′ non-coding regions of the nucleoprotein (NP) gene, a feature that is unique to some NDV isolates. The isolate shows the amino acid sequence 112RRQKRF117 at the cleavage site of the F protein, which is identical to a known motif for virulent pathotypes of NDV. The phylogenetic analysis of the coding region of the F gene indicated that this isolate belongs to genotype VI, more specifically to genotype VId, along with isolates from the other European countries (Denmark, Switzerland and Austria). The same genotype caused outbreaks in the Middle East and Greece in the late 1960s, and in Hungary, in the early 1980s, suggesting a common source for these outbreaks.

A serologic study of canine herpes virus-1 infection in the Norwegian adult dog population

Canine herpes virus-1 (CHV1) causes a fatal hemorrhagic disease in neonatal puppies and is associated with reproductive problems in female dogs. This serologic study was conducted to assess the seroprevalence of CHV1 infection in Norway. Blood samples were collected from clinically healthy dogs (n = 436) one yr of age and older of both genders, supplied by four small animal clinics (A, B, C and D) in different parts of the country. The immunoperoxidase monolayer assay was used for testing of CHV1 antibodies. Serum titers were recorded as the reciprocal value of the highest dilution producing specific cell staining. Titers equal to or above 80 were considered positive for exposure to CHV1. In total, 80.0% of the dogs had titers ≥80 and were classified as positive. Mean age for seronegative dogs was 4.7 yrs (95% CI 4.1-5.4) and for seropositive dogs 5.0 yrs (95% CI 4.7-5.4). Of the dogs, 32.8% displayed a weakly positive titer of 80, whereas 41.5 and 5.7% fell into the moderately (titer 160 and 320) and strongly (titer ≥640) positive categories, respectively. No association was demonstrated when comparing CHV1 antibody titers to gender or reproductive parameters like previous matings, pregnancies, births or number of puppies born. Age, visit in foreign countries and clinic explained together 78% of the variation in antibody titer categories. The percentage of positive samples differed significantly between the four clinics (A 98%, B 58.5%, C 74.6%, D 89.5%). A reasonable explanation for this finding has not been established. No information about an ongoing outbreak of CHV1 infection was available. In conclusion, this study strongly indicates that CHV1 infection is endemic in the dog population of Norway. There are significant differences in seroprevalence between geographic regions in the country.

A serological study of canine herpesvirus-1 infection in a population of breeding bitches in Norway

BackgroundCanine herpesvirus-1 (CHV1) causes a fatal hemorrhagic disease in neonatal puppies and is associated with infertility in female dogs. This study was conducted to assess the status of CHV1 infection in bitches in proestrus or estrus and to investigate possible risk factors by a detailed questionnaire. Blood samples were collected from healthy bitches (n = 193) not vaccinated against CHV1, aged one year or older and admitted for estrus control to the Canine Reproductive Clinical Unit, Norwegian School of Veterinary Science. The serum samples were analysed by immunoperoxidase monolayer assay and serum titers were recorded as the reciprocal value of the highest dilution producing specific cell staining.ResultsAltogether, 85.5% of the dogs had CHV1 titers ≥ 80 and were classified as positive. Mean age for dogs included in the study was 4.2 years (95% CI 4.0-4.5), and there was no difference in age between seronegative dogs vs seropositive dogs. When grouping the seropositive dogs into three categories according to the magnitude of the titer, a total of 38.8% of the bitches displayed a weakly positive titer of 80, 44.8% had moderately positive titers of 160 or 320 and 16.4% of the dogs fell into the strongly positive category with titer of ≥640. No association was demonstrated when comparing CHV1 antibody titers to fertility parameters such as previous matings, pregnancies, whelpings, puppies born or condition of puppies. Further, there was no difference in seroprevalence between bitches that had been abroad for a period of time and dogs only living within a Norwegian environment. Samples from dogs collected in summer and fall displayed moderate to high antibody titers indicating recent infection with CHV1. Season, previous birth, and participation in competitions/shows explained 67-78% of the variation in antibody titer.ConclusionsThis study demonstrates that CHV1 infection is common in breeding bitches in the eastern part of Norway. Associations with putative risk factors were not identified. However, season, previous whelping, and participation in competitions/shows explained 67-78% of the variation in antibody titer.

An unusual presentation of pseudocowpox associated with an outbreak of pustular ulcerative vulvovaginitis in a Swedish dairy herd

Species Pseudocowpox virus (PCPV; family Poxviridae) is known to cause pustular cutaneous disease in cattle. We describe an outbreak of pseudocowpox with an unusual clinical picture in a free-stall dairy herd of ~80 cows. Approximately 90% of the cows had vesicles, erosions, papules, and scabs on the vulva and vaginal mucosa. Histologic analysis of biopsy tissues indicated a primary, although not specified, viral infection. Transmission electron microscopy revealed parapoxvirus particles in both tissue and vesicular materials. Deep sequencing analysis of extracted DNA from swabbed vesicle areas gave a contig of nearly 120,000 nucleotides, matching the PCPV strain VR 634 with 100% identity. Analyses confirmed the absence of other potential causes of pustular vulvovaginitis such as bovine herpesvirus 1 and Ureaplasma diversum. A rolling cow brush was suspected to be the fomite.