Investigation of persistent infection of bovine viral diarrhea virus (BVDV) in Holstein dairy cows.

The aim of this study was to investigate the persistent infection (PI) of bovine viral diarrhea virus (BVDV) along with its coexistence between BVDV antibody titer and BVD virus in blood of Holstein dairy cows. Only large commercial farms (each contained < 1000-3000 unvaccinated cows) were included. There were 11 dairy cattle herds. They included nearly 20,000 dairy cows. Totally, 140 cows, > 3 months to almost 10 years old, were randomly sampled. Indirect enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) were used to detect BVDV antibody and virus, respectively. The percent positivity (PP) < 14 and ≥ 14 values are interpreted negative and positive, respectively. Simultaneously, whole blood samples pooled in groups of 10 animals were used for molecular detection of BVDV. The results revealed that 138 (98.56%) out of 140 cows were positive for BVDV antibody, while the BVDV antigen was detected only in 2 (1.42%) cows, which were negative for BVDV antibody and so were considered as persistent infection (PI) cows. They were also retested 3 weeks apart. Since the results showed the strong coexistence between seropositivity and BVD virus, in the infected dairy cattle herds, the combination of simple ELISA and pooled whole blood RT-PCR strategy could be an achievable approach to detect PI animals.

Hypomyelination associated with bovine viral diarrhea virus type 2 infection in a longhorn calf.

A newborn Longhorn heifer calf presented with generalized tremors, muscle fasciculations, ataxia, and nystagmus. At necropsy, no gross central nervous system lesions were observed. Histologically, the brain and spinal cord had mild to moderate diffuse microgliosis and astrocytosis, minimal nonsuppurative encephalitis, and decreased myelin staining. Ultrastructural examination revealed thinning and absence of myelin sheaths. Various cell types were immunohistochemically positive for bovine viral diarrhea virus (BVDV). Noncytopathogenic BVDV was isolated from the brain and identified as BVDV type 2 by phylogenetic analysis. BVDV-induced hypomyelination is rare and analogous to lesions in neonates infected with border disease and classical swine fever viruses. This is the first documented case of hypomyelination in a calf specifically attributed to BVDV type 2 and the first description of the ultrastructural appearance of BVDV-induced hypomyelination.

Congenital tremor and hypomyelination associated with bovine viral diarrhoea virus in 23 British cattle herds.

This paper presents data from 23 British herds investigated between 1991 and 2007 where neurological disease in calves was caused by bovine viral diarrhoea virus (BVDV) infection. A variety of clinical signs, most commonly tremor or trembling, were apparent in the calves from birth, and most were recumbent or unable to stand unsupported. Severe diffuse neuraxial hypomyelination was present in all of the calves, and immunohistochemistry revealed cerebral neuronal labelling consistent with congenital persistent pestivirus infection in each brain. BVDV was detected in peripheral blood samples from eight of 15 calves tested using an antigen ELISA, and was isolated in culture from samples of viscera, brain or blood collected from 17 of 24 affected calves. TaqMan RT-PCR for pestivirus RNA was positive for BVDV-1 in all six calves tested. Six of the virus isolates on which molecular classification was carried out, obtained from calves in four of the herds, were identified as BVDV-1a, while three isolates from one affected and two unaffected calves on a fifth farm were confirmed as BVDV-1b.

A congenital persistent infection of bovine virus diarrhoea virus in pigs: clinical, virological and immunological observations.

We report on a lifelong 'carrier' state of non-cytopathic bovine virus diarrhoea virus (BVDV) in an otherwise healthy pig. Three out of 13 pigs of a litter congenitally infected with BVDV survived for more than 3 months. One pig was BVDV seropositive at 1 month, the second seroconverted between 6 and 8 months, and the third remained viraemic and BVDV-immunotolerant until slaughter at 26 months. The latter pig, a boar, excreted virus in oropharyngeal fluid, urine and semen. Ejaculates, however, did not contain spermatozoa. The persistently infected pig had leucopenia from 3 months onwards, though differential white cell counts and thrombocyte counts remained normal. The antibody response of this pig after vaccination against foot-and-mouth disease and after infection with porcine parvovirus was not affected. The antibody response after vaccination against hog cholera, however, was delayed. In contrast, superinfection with antigenically related cytopathic BVDV strains did not alter the status of BVDV immunotolerance, nor did it induce clinical signs resembling mucosal disease as observed in cattle persistently infected with BVDV. Although the role of pigs in the epizootiology of bovine virus diarrhoea infections may be limited, the existence of healthy BVDV carrier pigs should be noted wherever control or eradication measures are applied.

The pathologies of bovine viral diarrhea virus infection. A window on the pathogenesis.

Pathologic lesions caused by bovine viral diarrhea virus (BVDV) infections comprise a wide spectrum of type, degree, and, by implication, pathogenesis, including congenital defects, necroticerosive lesions in mucosal epithelia and skin, and reactive as well as degenerative changes in lymphoid tissues. At least some of the pathology may not be solely due to BVDV replication per se, but rather caused by a host response to the virus, particularly the production of pro-inflammatory cytokines.

Femoral and tibial fractures in a newborn calf after transplacental infection with bovine viral diarrhoea virus.

A one-week-old Brown Swiss calf had fractures of the metaphyseal regions of the left femur and right tibia, and a generalised, severe derangement of osteogenesis. Alternating zones of sclerosis and radiolucency in the metaphysis of all the long bones was visible radiographically. A histopathological examination revealed a segmental disruption of trabecular modelling, with subsequent fracture. Immunohistochemistry using a monoclonal antibody for bovine viral diarrhoea (BVD) virus revealed abundant viral antigen in the pituitary gland, hypothalamus and thyroid gland. Intestinal tissue was positive on fluorescent antibody testing for the virus. The lesions indicate that transplacental infection with BVD virus can result in severe skeletal abnormalities and fractures.

The pathways for bovine virus diarrhoea virus biotypes in the pathogenesis of disease.

BVDV infections of cattle ranges from the transient acute infections, which may be inapparent or mild, to mucosal disease which is inevitably fatal. On occasions the acute infections can lead to clinical episodes of diarrhoea an agalactia but as these syndromes cannot be reproduced experimentally, the pathogenesis remains unclear. The immunosuppressive effect of acute BVDV infections can enhance the clinical disease of other pathogens and this may be an important part of the calf respiratory disease complex. Although BVDV antigen has been demonstrated within the lymphoid tissues, for prolonged periods, the evidence for viral latency remains to be proven. Venereal infection is shown to be important in the transfer of virus to the foetus and congenital infections can cause abortions, malformations and the development of persistently viraemic calves. The two biotypes of BVDV, non-cytopathogenic and cytopathogenic, are described. Their sequential role in the pathogenesis of mucosal disease arises from the initial foetal infection with the non-cytopathogenic virus and the subsequent production of persistently viraemic calves. These calves may later develop mucosal disease as a result of superinfection with a "homologous" cytopathogenic virus and the possible origin of this biotype by mutation is discussed. Chronic disease is defined as a progressive wasting and usually diarrhoeic condition; it is suggested that this may develop following superinfection of persistently viraemic cattle with a "heterologous" cytopathogenic biotype.

Congenital curly haircoat as a symptom of persistent infection with bovine virus diarrhoea virus in calves.

Ten calves were born small and with a curly haircoat in a dairy herd which comprised approximately 185 milking animals. These calves commonly developed diarrhoea and/or signs of respiratory disease at the age of 2 to 4 weeks. Two of the calves died and 5 were chronically ill and poor doers and were therefore euthanized. This susceptibility to disease of the curly haired calves was quite different from what was observed among other calves in the herd. Sera from seven of the curly haired calves were examined and were all found to be free from detectable antibodies to bovine virus diarrhoea virus (BVDV) and to harbour a non-cytopathic strain of BVDV. One of the calves was retested after 7 weeks and was still seronegative and viraemic. Of 49 non-curly haired calves examined in the herd 44 were BVDV seropositive. The other 5 were seronegative to BVDV but attempts to isolate BVDV from their sera failed.

Clinical aspects of bovine virus diarrhoea virus infection.

Bovine virus diarrhoea virus (BVDV) infection of cattle results in a wide range of clinical manifestations. This article reviews the clinical responses associated with BVDV and discusses these diseases in terms of acute infection in immunocompetent cattle, fetal infection, infection in cattle immunotolerant to and persistently infected with BVDV and finally mucosal disease.

The pathogenesis of bovine virus diarrhoea virus infections.

Bovine virus diarrhoea virus (BVDV) disease in cattle ranges from the transient acute infections, which may be inapparent or mild, to mucosal disease which is inevitably fatal. On occasions the acute infections can lead to clinical episodes of diarrhoea and agalactia but as these syndromes cannot be reproduced experimentally, the pathogenesis remains unclear. The immunosuppressive effect of acute BVDV infections can enhance the clinical disease of other pathogens and this may be an important part of the calf respiratory disease complex. Although BVDV antigen has been demonstrated within the lymphoid tissues, for prolonged periods, the evidence for viral latency remains to be proven. Venereal infection is shown to be important in the transfer of virus to the foetus and congenital infections can cause abortions, malformations and the development of persistently viraemic calves. The two biotypes of the virus, non-cytopathogenic and cytopathogenic, are described. Their sequential role in the pathogenesis of mucosal disease arises from the initial foetal infection with the non-cytopathogenic virus and the subsequent production of persistently viraemic calves. These calves may later develop mucosal disease as a result of superinfection with a "homologous" cytopathogenic virus. The possible origin of this biotype by mutation is discussed. Chronic disease is defined as a progressive wasting and usually diarrhoeic condition; it is suggested that this may develop following superinfection of persistently viraemic cattle with a "heterologous" cytopathogenic biotype.

Current situation of bovine virus diarrhoea-mucosal disease (BVD-MD) virus infections and their antigenic diversity in Hokkaido, Japan.

The current situation of bovine virus diarrhoea-mucosal disease (BVD-MD) virus infections is briefly reviewed, with special reference to problems arising from fetal infection in the Hokkaido district, a northern island of Japan. The results of some investigations on BVD-MD virus carried out in Japan are also described. Although bovine congenital anomalies caused by BVD-MD virus and mucosal disease may be late sequelae to fetal infection and occur sporadically, it appears that their incidence and importance in the Hokkaido district have increased in recent years. The results of antigenic characterisation of the recent isolates and serologic survey on bovine sera suggested that BVD-MD viruses with various antigenic properties are widespread among cattle in the district. There is also a possibility that clinical manifestations in infected cattle may differ with the antigenicity of the viruses. In addition, the virological investigations on experimental and naturally occurring mucosal disease suggested that persistently infected cattle are populations at high risk of developing mucosal disease. The antigenic homology of non-cytopathogenic persistent virus and cytopathogenic virus is probably an important factor in the pathogenesis of mucosal disease.

Demonstration of bovine viral diarrhoea virus in peripheral blood mononuclear cells of persistently infected, clinically normal cattle.

Peripheral blood mononuclear cells (PBL) from cattle known to be persistently viraemic with bovine viral diarrhoea virus (BVDV) following a foetal infection, were examined for the presence of viral antigens and cell-associated infectious virus. Using immunocytochemical techniques, physical separations of PBL subsets and virus isolation techniques (directly and by cocultivation) it was found that infection occurred in B and T lymphocytes, monocytes, and a group of cells designated null cells for lack of more specific classification. The latter three groups also supported viral replication, as infectious virus could be isolated from enriched cell populations. BVDV-like particles in cytoplasmic vesicles of PBL subsets were detected by electron microscopy.

Production of cattle immunotolerant to bovine viral diarrhea virus.

Inoculation of bovine virus diarrhea virus into 58 to 125 day old fetuses of bovine virus diarrhea virus seropositive pregnant cows, or inoculation of bovine virus diarrhea virus into seronegative cows 42 to 114 days pregnant, may produce clinically normal calves which are persistently infected with the specific isolate of bovine virus diarrhea virus yet seronegative to the homologous and heterologous isolates. Reinoculation of these persistently infected cattle with their homologous isolate produced no neutralizing antibody response to bovine virus diarrhea virus. These persistently infected cattle were immunocompetent as they developed neutralizing serotiters to infectious bovine rhinotracheitis, parainfluenza-3 viruses and agglutinating serotiters to Pasteurella hemolytica .

Neurological disorders, virus persistence and hypomyelination in calves due to intra-uterine infections with bovine virus diarrhoea virus. II. Virology and epizootiology.

The results are described of virological and serological research carried out in a Dutch dairy herd during a number of years. The motive was the birth of a number of calves with neurological disorders pointing at an intra-uterine infection with BVD-virus in 1980. Also in the previous and in both the following years a calf was born with similar symptoms. The clinical signs and the course of the affection in these eight calves were described in a previous paper (2). The diagnosis was confirmed through virus isolation from pre-colostral blood of one calf and from autopsy material from four aberrant calves. During the investigation three clinically normal animals with a persistent virus infection were found. The clinically recovered animal of 1979 also provided to be a virus carrier. In addition, in two animals a transient viremia in the presence of specific antibodies was found. The four virus carriers conceived normally. The second pregnancy of the oldest animal also passed normally. Their five calves proved to be BVD-virus carriers as well. One calf, born in 1982, showed nervous disturbances to a serious extent. Of the four other clinically normal animals, one calf was euthanasized because of a serious necrotizing enteritis. The remaining calves stayed healthy and grew up normally. One of the two animals with a transient viremia was five months pregnant at that moment. At birth in 1981 her calf showed nervous disorders, but both the virological and the serological examinations of the pre-colostral blood were negative.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurological disorders, virus persistence and hypomyelination in calves due to intra-uterine infections with bovine virus diarrhoea virus. I. Clinical symptoms and morphological lesions.

The clinical and pathological findings after a natural intra-uterine infection with BVD-virus in a Friesian dairy herd are described. The virological and serological aspects will be discussed in a separate paper (30). In a period of 4 years, 11 calves were born with the following nervous symptoms: more or less serious incoordination, tremor, oscillating nystagmus, and a negative blinking reflex. The pupillary and sucking reflexes were normal. No ocular defects, such as lenticular opacity or retinal atrophy were observed. The first calf was born in 1979. Within 6 months the symptoms disappeared. After a normal conception and pregnancy this animal gave birth to 2 clinically normal calves in 1981 and 1982. The second calf died at the age of 2 months, due to an ulcerating enteritis. In 1980, again 8 calves with the same nervous symptoms were born within a period of 3 months. Two calves died at the age of 3 days and 5 weeks respectively; 2 calves were sold when 10 days and 3 weeks old; one calf did not improve and was necropsied at the age of 17 days. The remaining 3 calves showed only a slight hypermetria when examined after 6 months. At that time nystagmus was only visible with ophthalmoscopy. Two calves were slaughtered when 10 months old. The last one, a bull, proved to be sterile and was necropsied at the age of 1 1/2 year. A calf, born in 1981, recovered within a week and was necropsied at the age of 15 days. The last calf, born in 1982, did not improve at all and was necropsied at the age of 14 days. During these 4 years none of the other animals in the herd showed any symptoms due to an acute or chronic BVD-virus infection. At post mortem examination of 6 animals no macroscopically visible malformations were found. Hypomyelination and abnormal glial cells were evident in 5 cases, especially in the two youngest calves which did not show any improvement. One of them had had an obvious thymic hypoplasia. The calf which recovered within a week showed only very slight changes. In one of the calves slaughtered at 10 months, inflammatory lesions were found in the brain. The diagnosis was confirmed by virological investigations. Clinically as well as pathologically there was a close resemblance to Border disease in lambs and congenital tremor in piglets after prenatal exposure to Hog cholera virus.

Total protein and immunoglobulins G1, G2, and M in serum of calves persistently infected with bovine viral diarrhea virus.

Total serum protein and immunoglobulins (Ig) G1, G2, and M concentrations were investigated in 11 calves persistently infected with bovine viral diarrhea virus. These calves were allowed to suckle from their dams until weaned. A gradual increase in total protein was observed from birth to 12 months of age. There was a wide variation in Ig concentrations in pre- and postcolostrum sera. The IgG1 increased from the time of delivery of the calves to the 5th month, decreased by the 10th month, and then stabilized through the 12th month. The IgG2 increased from birth to 10 months and remained stable through 12 months. The IgM increased from birth to the 11th month, and then decreased sharply by the 12th month.