F Frigeri

A study of a herpesvirus isolated from dairy cattle with a history of reproductive disorders

Three strains of herpesvirus were recovered from cows with vulvovaginitis. The three isolates (85/BH 16TV, 85/BH 17TV, 85/BH 18TV), when compared by cross serum neutralization (SN) tests, were found to be antigenically identical. They were serologically distinct from infectious bovine rhinotracheitis (IBR) virus and Bovid herpesvirus 2 (BHV2), while they cross reacted with bovine herpesvirus DN-599. Besides the serologic aspects, the three isolates appeared to share common biological, physical and morphological properties with the newly recognized bovine herpesviruses, of which DN-599 is a representative strain.

Vaccination of calves against bovine herpesvirus-1: assessment of the protective value of eight vaccines.

Eight separate, but related experiments, were carried out in which groups of six calves were vaccinated with one of eight commercial vaccines. In each experiment the vaccinated calves were subsequently exposed to three calves infected with virulent bovine herpesvirus-1 (BHV-1). In each experiment, all infected donor calves developed a typical severe infectious bovine rhinotracheitis (IBR) infection and excreted virus in their nasal secretions of up to 10(8.00) TCID50/0.1 ml. One live BHV-1 gE-negative vaccine (A) and three modified live vaccines (B, C, D), administered intranasally, all protected against clinical disease. The calves vaccinated with one vaccine (C) also did not excrete virus in the nasal secretions, whereas the calves protected by vaccines A, B and D excreted virus in their nasal secretions but at low titres (10(0.66)-10(1.24) TCID50/0.1 ml). A fourth modified live vaccine (E), given intramuscularly, failed to prevent mild clinical disease in the calves which also excreted virus in the nasal secretions at titre of 10(1.00) TCID50/0.1 ml. An analogous result was given by the calves vaccinated with either of the two inactivated vaccines (F and G) or with a BHV-1 subunit vaccine (H). All calves developed mild clinical signs and excreted virus at titres of 10(2.20)-10(3.12) TCID50/0.1 ml. Calves vaccinated with C vaccine were subsequently given dexamethasone, following which virus was recovered from their nasal secretions. The virus isolates did not cause disease when calves were infected and appeared to be closely related to the vaccine strain.

A study of cytopathic rotavirus strains isolated from calves with acute enteritis

Nine cytopathic bovine rotavirus strains were isolated in MA-104 cell cultures from fecal specimens of dairy calves suffering from diarrhea. Isolation of the virus was accomplished from three outbreaks which occurred on dairy farms located in Central and Southern Italy. Fecal suspensions were treated with a high concentration (1000 micrograms/ml) of trypsin, and inoculated into MA-104 cell cultures grown out in Eagles minimum essential medium (MEM) containing 5 micrograms/ml of the enzyme. Cytopathic effects (CPE), characterized by intracytoplasmic inclusion bodies of different sizes and shapes, were observed on the 1st passage with five of the strains and on the 2nd (2 strains) or the 3rd (2 strains) passage for the others. The presence of trypsin and the use of MA-104 cells appeared to be essential for the occurrence of CPE, inasmuch as no CPE was detected when trypsin was omitted in the MA-104 cell system. Replication failed to occur when primary bovine embryo kidney cell cultures with or without trypsin were used. Electron microscopy revealed the presence of particles with a typical rotavirus morphology. In MA-104 cells, the titre of virus reached its maximum 48 hr after inoculation. Small, clear-cut plaques were produced by the isolates in MA-104 cells under the overlay of MEM containing carboxymethyl cellulose, trypsin and DEAE-dextran. The nine rotavirus strains were antigenically related, whereas the relationship to either the Nebraska or the Compton rotaviruses was quite weak.

The efficacy of colostrum from cows vaccinated with rotavirus in protecting calves to experimentally induced rotavirus infection

Calves which were continuously fed colostrum from vaccinated cows for the first ten days of life, were fully refractory to experimental infection with strain 81/36 F of bovine rotavirus. By contrast, the response to virus exposure of calves which were treated with normal colostrum was identical to that of the control calves, in that they underwent severe diarrhea and a significant slowing of the growth rate. The antibody titer in the milk of vaccinated cows tends to decline rapidly so that it no longer provides any protective effect. Two alternatives were considered feasible in improving prophylaxis for rotavirus infections: (a) the continuous feeding of calves with 1st day colostrum as part of the ration throughout the period of greatest risk (first week of life), or (b) enhancing the efficacy of the vaccine in pregnant cows to the point where antibody concentration in the milk would remain at a protective level.

The use of immunomodulators in the control of infectious bovine rhinotracheitis

Three experiments have been carried out to verify the effectiveness of an immunomodulator, Baypamun (Bayer AG) in limiting the spread of Bovine herpesvirus-1 (BHV-1), the causal agent of infectious bovine rhinotracheitis (IBR). In the first experiment, four calves infected with BHV-1 developed severe disease whereas four calves given Baypamun simultaneously with the virus had less severe disease. Four other calves in contact with the infected calves became severely ill but another four given Baypamun were only mildly affected. In the second experiment three calves infected with BHV-1, which reacted with typical disease, were allowed to remain in contact with six calves. All six calves were given Baypamun at various times following the exposure to BHV-1 infection and all showed a much reduced reaction with two treated for 4 days developing no clinical disease. Finally, in the third experiment one calf vaccinated one month before the start of the experiment did not develop any signs of disease when housed together with a calf experimentally infected with BHV-1. Of four other calves, vaccinated when the infected calf showed the first signs of disease, only the two given Baypamun in addition to the vaccine, were protected from clinical disease whereas the two given vaccine only developed classical signs of IBR. In the three experiments the virus shedding by the Baypamun-treated calves resulted to be significantly reduced.

A serological comparison of some animal herpesvirus

Bovine herpesvirus 1 (BHV-1) isolates (Cooper-type strain 4975 and Oxford) were compared in neutralization tests with the bovine herpesvirus 4 (BHV-4) isolate (85/16 TV) and the herpesviruses of red deer (D2839/1) and goats (E/CH). Hyperimmune antiserum was prepared in rabbits against the plaque-selected viruses and endpoint and kinetic neutralization test were made. BHV-4 was clearly different from the other four viruses. The closely-related BHV-1 strains were also related in these tests to the red deer herpesvirus. The Oxford strain seemed rather closer antigenically than the Cooper-type strain to the red deer herpesvirus. Antiserum to the caprine herpesvirus failed to neutralize either BHV-1 strain or red deer virus, but antiserum to the Cooper-type and red deer herpesviruses did neutralize caprine virus to a limited extent.Abstract Bovine herpesvirus 1 (BHV-1) isolates (Cooper-type strain 4975 and Oxford) were compared in neutralization tests with the bovine herpesvirus 4 (BHV-4) isolate (85/16 TV) and the herpesviruses of red deer (D2839/1) and goats (E/CH). Hyperimmune antiserum was prepared in rabbits against the plaque-selected viruses and endpoint and kinetic neutralization test were made. BHV-4 was clearly different from the other four viruses. The closely-related BHV-1 strains were also related in these tests to the red deer herpesvirus. The Oxford strain seemed rather closer antigenically than the Cooper-type strain to the red deer herpesvirus. Antiserum to the caprine herpesvirus failed to neutralize either BHV-1 strain or red deer virus, but antiserum to the Cooper-type and red deer herpesviruses did neutralize caprine virus to a limited extent.

Experimental infection of calves with strains of Bovid herpesvirus-4

Fourteen calves were inoculated intranasally (i.n.) with the viral isolates as follows: 5 with 85/BH 16TV, 1 with 85/BH 17TV, 1 with 85/BH 18TV, 2 with 85/BH 231TN and 5 with 85/BH 232TN. Strain 85/BH 16TV was the only one which caused overt respiratory-like disease in all inoculated calves. Onset of the disease was observed after 7-8 days of incubation and was characterized by fever, depression, nasal discharge and coughing. Virus was isolated from the nasal swabbings of calves obtained from post-infection day (PID) 2-10. The other viral strains did not cause any sign of disease although virus was isolated regularly from the nasal swabbings of the inoculated calves. Virus was recovered from central nervous system tissues of calves that were infected with 85/BH 16TV or 85/BH 232TN strains and were killed on PID 4 or 8. Virus was also isolated from other tissues, such as lymph node, nasal mucosa (PID 8), or lung (PID 4). It was speculated that the nervous system could be one of the target areas of the virus of the naturally occurring infection by BHV-4. This might indicate a possible role of the nervous system (site of latency?) in the pathogenesis of BHV-4 as is the case in certain herpesviral infections of man and the lower animals.

A study of some pathogenetic aspects of bovine viral diarrhea virus infection.

The cytopathic (CP) strain TVM-2 of bovine virus diarrhea virus (BVDV) induced in calves a severe disease, whereas the calves inoculated with the non-cytopathic (NCP) New York-1 strain, remained clinically normal. When calves were immunosuppressed with dexamethasone (DMS) they underwent an overt, generally fatal disease. This result was obtained with either the CP and the NCP strain of BVDV. It was speculated that the immunosuppressive activity of BVDV could be a property peculiar to certain isolates of the virus.

Isolation and characterization of cytopathic strains of rotavirus from rabbits

SummaryThree cytopathic rotavirus isolates were recovered from young rabbits affected by an enteric syndrome. The three isolates, when compared by cross serum-neutralization tests, were found to be of the same serotype. Cross neutralization occurred also between a representative of the rabbit isolates and one strain of bovine rotavirus.

A serological survey of bovine herpesvirus-1 infection in selected dairy herds in northern and central Italy

Serum samples from a total of 6979 dairy cattle from 55 herds in northern Italy (51 herds) and central Italy (4 herds), were examined by the serum neutralization test for the presence of antibody to bovine herpesvirus-1 (BHV-1). It was found that 84.31% of the farms selected in northern Italy and all the farms from central Italy had seropositive animals at titers of 1:4 or higher. The prevalence of infection was essentially the same among the cattle populations of the two selected areas of the country, being of 34.99% in the north and of 38.65% in central regions. A comparison of the data from the present study with those obtained in a serological survey conducted in Italy in 1966, shows that the rate of seropositive cattle to BHV-1 has increased by about 5.0% in the last 30 years.