Genetic typing of pestiviruses from New Zealand

AIM: To investigate the genetic type of 20 pestiviruses collected from New Zealand over the period 1967-97. METHODS: The pestiviruses were genetically typed by the sequencing of polymerase chain reaction (PCR) products. The primers selected were from the 5'-untranslated region (5'-UTR) of the pestivirus genome and consistently amplified a 288 bp fragment from all samples tested. RESULTS: Sequencing and phylogenetic analysis of PCR products revealed that all samples obtained from cattle represented bovine viral diarrhoea (BVDV) type I. Two sheep isolates were characterised as border disease virus (BDV). A pestivirus isolated from foetal calf serum of USA origin was typed as BVDV type II. CONCLUSIONS: The findings show that the evolution of pestiviruses in New Zealand has been similar to Europe and North America, indicating the occurrence of a conservative phylogenetic branch of BVDV type I in cattle and the presence of BDV in the sheep population.     

Genetic comparison of ovine and bovine pestiviruses

Viral RNA oligonucleotide fingerprinting was used to compare genetic relationship among pestiviruses originating from ovine or bovine host species. Ovine pestiviruses, including reference border disease virus and 2 border disease isolates originating from natural pestivirus infections of sheep, appeared to have a more distant genetic relationship among themselves than with certain bovine pestiviruses. A closer genetic relatedness was evident between border disease virus and 3 noncytopathic bovine pestiviruses, including Draper bovine viral diarrhea virus (BVDV), a BVDV isolate that originated from aborted bovine fetuses, and a virus that was isolated from the serum of a calf that had a chronic BVDV infection. Four noncytopathic bovine viruses, including Draper BVDV and 3 field isolates, were closely related. Reference Oregon C24V BVDV, a cytopathic virus, was closely related to only 1 of the 7 noncytopathic viruses in this study.     

Overview of helminth problems in domestic ruminants in Switzerland

Potent anthelmintics were introduced into the Swiss market several decades ago. Despite this, gastrointestinal nematodes (GIN), lungworms and the large liver fluke (Fasciola hepatica) can successfully inhabit Swiss ruminant farms. This is mainly due to a high reproductive capacity as well as very efficient survival strategies. In addition some species readily develop anthelmintic resistance. GIN-infections in young cattle are under comparatively good control. However, prophylactic measures are compromised where adult stock is also affected due to incomplete development of immune protection. Under these circumstances control measures must include all age groups. This results in fewer helminths in refugia thus may accelerate the development of anthelmintic resistance. This review aims to present a synopsis of the significance of the major helminth infections obtained on pasture by large and small ruminants in Switzerland. Currently available strategies for strategic helminth control are summarized and an outlook is given on new developments which might expand the spectrum of control measures relevant for veterinary practice in the future.     

Piroplasms of ruminants in Switzerland and zoonotic significance of Babesia

Piroplasms are tick-transmitted blood parasites belonging to the genera Babesia and Theileria. In western and southern Switzerland, B. divergens, a small Babesia species, has been known for a long time as a parasite of cattle. Recent investigations have revealed the autochthonous occurrence of this parasite also in central and eastern Switzerland. On the occasion of an outbreak of anaplasmosis in the canton of Grisons, however, B. bigemina, a large Babesia species, and Theileria of the buffeli/sergenti/orientalis species complex were for the first time identified; the epidemiology of these two piroplasms in Switzerland remains unknown until now. The recent identification by genetic analyses of B. divergens in wild ruminants contradicts the hitherto postulated strict host specificity of this Babesia species for cattle. B. divergens as well as the closely related Babesia spp. genotype EU1 have in single cases also been identified in splenectomized humans.The rodent babesia B. microti which causes a human infection that is considered an "emerging tick-borne disease" in the U.S.A., is widespread in rodent populations in Switzerland, but seems to be of minor relevance as zoonotic pathogen here. Reasons for this could be differences in virulence of the parasites or in the transmission by the respective tick-vectors on the two continents.     

Genetic typing of bovine pestiviruses from England and Wales.

Using RNA purified directly from stored clinical specimens, a collection of 62 pestiviruses were typed by RT-PCR and sequencing within the 5'-untranslated region of the genome. All the specimens had been obtained in 1966/1967 from diary cattle in England and Wales. Eight further pestiviruses, grown in cell culture, were characterised in the same way. Seven of these viruses were representatives of a panel of British isolates, obtained from cattle ten years before. The eighth was the virus used in a British bovine viral diarrhoea (BVD) vaccine. Most of the viruses were genetically unique and were of BVDV type Ia. One recent isolate was BVDV type Ib, two others were intermediate between Ia and Ib. No BVDV type II or border disease virus (BDV) isolates were found. There was no overall association between geographical and phylogenetic clustering, suggesting long-distance virus dispersal, presumably via trading of infected cattle. The sequences of the recently obtained cattle viruses were very similar or, in one case, identical to the older isolates in the region studied. Their close similarity to some previously characterised pestiviruses from British sheep suggests that a common pool of BVDV Ia is shared by these two livestock species, although another pestivirus--BVDV--is confined to sheep. The British cattle viruses were mostly distinct from continental European isolates, but more similar to type Ia isolates from North American cattle.     

The frequency and geographic distribution of Giardia infections in ruminants in Switzerland

In various districts (Cantons) of Switzerland 815 calves (a few days up to 6 months old), 382 lambs and 20 young goats (both groups 1-6 months old) were selected randomly for a single coprological examination (flotation method) for Giardia infection. In average 26.6% of the calves, 29.8% of the lambs and 4 of 20 young goats excreted Giardia cysts. In 9 Cantons the percentages of cyst excretors among the calves varied between 15 and 32, but these differences were not significant. Further there were no significant differences in the frequency of cyst excretion between calves of 3 different breeds and 2 age groups (up to 3 months old and 3 to 6 months). The intensity of cyst excretion was high and varied in random samples between 4.1 x 10(3) and 3.0 x 10(5) cysts per g of faeces in calves and between 2.2 x 10(3) and 1.6 x 10(5) in lambs. In 5 of 7 farms where calves and lambs were maintained simultaneously both animal species were Giardia infected. As expected, trophozoites of Giardia isolates from calves and lambs belonged to the Giardia duodenalis type and could not be differentiated on a morphological basis. Giardia cysts from calves (average measurements: 13.7 x 9.1 microns) and lambs (13.8 x 9.2 microns) were indistinguishable both morphologically and morphometrically. The results indicate that Giardia infections are frequent and geographically widely distributed in calves and lambs in Switzerland.     

Viral infections shared between water buffaloes and small ruminants in Switzerland

Importation of exotic animals that may harbor infectious agents poses risks for native species with potentially severe impacts on animal health and animal production. Although the Asian water buffalo (Bubalus bubalis) population in Europe is steadily increasing, its susceptibility to viral infections and its role for interspecies transmission is largely unknown. To identify viral infections that are shared between exotic water buffaloes and native small ruminants, we collected blood samples from 3 Swiss farms on which water buffaloes were kept either without, or together with, sheep or goats. These samples were analyzed by next-generation sequencing (NGS) as well as by selected conventional tests, including PCR, ELISA, and in some cases a virus neutralization test. By NGS, a novel virus of the genus Gemykrogvirus (GyKV; Genomoviridae) was first detected in the buffaloes on one farm, and subsequently confirmed by PCR, and was also detected in the co-housed sheep. In contrast, this virus was not detected in buffaloes on the farms without sheep. Moreover, conventional methods identified a number of viral infections that were not shared between the exotic and the native animals, and provided evidence for potential roles of water buffaloes in the epidemiology of ruminant pestiviruses, especially bovine viral diarrhea virus, bluetongue virus, and possibly bovine alphaherpesvirus 2. Our results clearly indicate that water buffaloes are susceptible to interspecies viral transmission and may act as intermediate hosts, or even as reservoirs, for these viruses.     

Molecular genetics of pestiviruses.

Recent developments in understanding the molecular genetics of pestiviruses are reviewed. The genomic RNA of several pestiviruses has been molecularly cloned and sequenced. The genetic organization of the viral protein coding region has been refined, and the complete complement of virus-encoded proteins has been elucidated. Viral gene expression involves both co-translational and post-translational precursor polyprotein processing. Biogenesis of the virion structural proteins requires the proteolytic activity of the first protein of the open reading frame (p20), as well as host cell enzymes. A second virus-encoded proteinase (p80) is required for processing viral nonstructural proteins. Molecular and biochemical data indicate pestiviruses share many features with both the flaviviruses and human hepatitis C viruses, while at the same time, also reveal their distinct nature.     

Prevalence of antibodies to pestiviruses in goats in Austria

Serological investigations were carried out to determine the prevalence of pestiviral infections in goats in Austria, and to investigate the possible relations to herd management practices. The prevalence of antibodies to pestiviruses was investigated in 549 goats in 80 flocks from four regions of Austria. The examination for antibodies was performed using an indirect enzyme-linked immunosorbent assay detecting antibodies to the border disease virus (BDV) and bovine viral diarrhoea virus (BVDV). The observed individual prevalence was 11.5% and the flock prevalence was 31.3%. Comparative neutralization studies on the 63 seropositive samples with BVDV-1, BVDV-2 and the BDV yielded in 32 samples higher titres (> or =4-fold) to BVDV-1 and in two samples to BDV. The remaining samples did not show distinct differences in antibody titres against the pestivirus strains tested because of the cross-reactions. There was a significant (P < 0.05) association between the prevalence of antibodies to pestiviruses and the presence of cattle on the farm. Significant (P < 0.05) geographical variations in individual prevalence were obtained, ranging from 3.5% in lower Austria to 20.2% in Vorarlberg.     

Genetic heterogeneity of variance in production traits of laying hens

Genetic parameters for mean and for environmental variation in egg weight, body weight, age at first egg, and egg production were estimated in eight layer lines. The data were recorded from years 1999-2007, with on average of 6500 birds per line. An iterative mean-variance REML method was applied with a sire-plus-dam model for mean, a sire model for variance, and a fixed effect of hatch within generation for both mean and variance. The estimated heritability of environmental variation averaged about 5% for body weight, 3% for egg weight, and 11% for age at first egg, but was inconsistent among the lines for egg production (0-15%). Correlations between means and variances were slightly positive for body weight, egg weight, and age at first egg; and strongly negative for egg production. Age at first egg had the highest heritability of environmental variation; and favourable correlations with egg production and with variation in other production traits indicate that reducing variation in this trait may have potential benefits for the breeding industry.     

The genetic basis for cytopathogenicity of pestiviruses

Two biotypes of pestiviruses, cytopathogenic (cp) and noncp viruses, can be distinguished by their effects on tissue culture cells. Identification of cp bovine viral diarrhea virus (BVDV) has been frequently reported since antigenically closely related noncp and cp BVDV can be isolated from cattle with fatal mucosal disease (MD) and are called a virus pair. In contrast to the BVDV system, only few cp border disease virus (BDV) and cp classical swine fever virus (CSFV) strains have been described. Serological analyses and sequence comparison studies showed that cp pestiviruses arise from noncp viruses by mutation. Elaborate studies during the last 10 years revealed that in most cases RNA recombination is responsible for the generation of the cp viruses. Recent results showed a second way for the development of a cp pestivirus which is based on the introduction of a set of point mutations within the NS2 gene.     

Peste des petits ruminants infection in domestic ruminants in Sudan

The existence of peste des petits ruminants (PPR) in domestic ruminants and camels in Sudan during 2008–2012 was investigated. Lung tissues and serum samples were randomly collected from sheep, goats, cattle, and camels at different areas of Sudan. A total of 12,384 serum samples were collected from clinically healthy 7413 sheep, 1988 camels, 1501 cattle, 1459 goats, and 23 gazelles at different areas in the Sudan. They were examined for PPR antibodies using competitive ELISA (cELISA). The overall detected seroprevalence of PPR in tested sera was 49.4%; seroprevalence values within species were 67.1, 48.2, 25.8, 2.1, and 21.7% in sheep, goat, cattle, camels, and gazelles, respectively. The highest seroprevalence (68.1%) was observed in sera collected from Darfur states, then the central states (54.3%). A total of 1276 lung tissue samples (623 sheep, 324 cattle, 220 camels, and 109 goats) were collected. The majority of lung samples were collected from clinically healthy animals that showed lesions on PM in slaughterhouses (95%) and during PPR outbreaks; samples were tested for PPR antigen using immunocapture ELISA (IcELISA). PPR antigen was detected in 233 out of the 1276 tested samples (18.3%). Positive results were observed in samples collected from clinically healthy and diseased animals. The observed prevalence values in each species were 33.6, 21.1, 15.4, and 12.3% in camel, goat, sheep, and cattle, respectively. PPR antigen was detected in samples from different areas; however, the highest prevalence (63.9%) was found in samples collected from the eastern states, then Khartoum state (28%). Trials for virus isolation were done in different cell cultures. Out of 30 IcELISA-positive samples inoculated in primary bovine and ovine kidney cells, Vero cells, the PPR virus was successfully isolated from 15 (eight sheep, five camels, and two goats) samples in the three cell culture types. Using RT-PCR, PPRV nucleic acid was detected in all 25 IcELISA-positive tested samples.     

Characterization of porcine and some ruminant pestiviruses by cross-neutralization

Serologic relationships between 11 pestivirus strains that originated from pigs and five that originated from cattle or sheep were studied by cross-neutralization. Experiments were performed with pig and sheep sera raised against the strains. The results were analysed by a computerized taxonomic procedure. The 16 viruses were classified into four distinct serologic groups. All hog cholera virus (HCV) strains were classified in one group; the other three groups consisted of strains that can infect pigs, but that are identified as bovine viral diarrhoea virus (BVDV) or border disease virus (BDV), or showed a closer relationship to BVDV and BDV than to HCV.     

Serological survey for antibodies against pestiviruses in sheep in Austria

The prevalence of antibodies to pestiviruses was investigated in 4931 sheep, in 377 flocks, in four federal states of Austria, by means of an indirect elisa that detected antibodies to Border disease virus (BDV) and bovine viral diarrhoea virus (BVDV). The mean flock prevalence was 62.9 per cent and the mean individual prevalence was 29.4 per cent. Comparative neutralisation studies on the elisa-positive samples with BVDV type 1 (BVDV-1), BVDV type 2 (BVDV-2) and BDV recorded 336 samples with higher titres (more than four times average) to BVDV-1, three samples with higher titres to BVDV-2 and 55 samples with higher titres to BDV. The other samples did not show clear differences in antibody titres against the strains of pestivirus tested because of cross-reactions. The seroprevalence of pestiviruses in sheep was significantly higher on farms with cattle. There were significant regional differences between the prevalences in flocks and individual sheep, the highest prevalences being in the region of Austria where communal alpine pasturing of sheep, goats and cattle is an important part of farming.