Bovine ulcerative mammillitis caused by a herpesvirus

Full genome sequence of bovine alphaherpesvirus 2 (BoHV-2)

We present the complete genome sequence of bovine alphaherpesvirus 2 (BoHV-2), a member of the family Herpesviridae, subfamily Alphaherpesvirinae, genus Simplexvirus. BoHV-2 is the causative agent of bovine ulcerative mammillitis (bovine herpes mammillitis) and pseudo-lumpy skin disease. The genomic architecture of BoHV-2 is typical of most simplexvirus genomes and congruent with that of human alphaherpesvirus 1 (HHV-1). The genome comprises a total of 131,245 base pairs and has an overall G+C content of 64.9 mol%. A total of 75 open reading frames are predicted. The gene repertoire of BoHV-2 is analogous to that of HHV-1, although the coding region of US12 is missing. A phylogenetic analysis supported BoHV-2 as a member of the genus Simplexvirus.

Diphenyl diselenide and cidofovir present anti-viral activity against Bovine Alphaherpesvirus 2 in vitro and in a sheep model

Bovine alphaherpesvirus 2 (BoHV-2) - the agent of bovine herpetic mamillitis (BHM) - is related to Human alphaherpesviruses 1 and 2 (HHV-1, HHV-2) and, as such, has been proposed as a model for vaccine and drug testing. We herein investigated the anti-viral activity in vitro against BoHV-2 of three anti-herpetic drugs: Cidofovir (CDV), Fanciclovir (FAM), Foscarnet (PFA), and diphenyl disselenide (Ph₂Se₂)_, a compound that has showed activity against HHV-2. Plaque reduction assays (PRA) revealed a significant reduction in viral plaques (p < 0.05) in cells treated with Ph₂Se₂ (79.7% reduction) or CDV (62.8%). FAM treatment resulted in a slight decrease in plaque number (22.9%, p < 0.05); PFA showed no activity. The effects of Ph₂Se₂ and CDV, alone or in combination, were investigated in ewes inoculated with BoHV-2 transdermally and submitted to daily topic treatment. Virus inoculated ewes developed lesions progressing through the stages of hyperemia, large papules or depressed dark areas, followed by scab formation. Treatment with Ph₂Se₂ resulted in reduction in clinical score from day 10 pi onwards (P < 0.05), shortening of clinical course and reduction in duration of virus shedding (P < 0.05) compared to untreated controls. Combined treatment (Ph₂Se₂ + CDV) and CDV alone, also led to clinical improvement (P < 0.05), yet less pronounced and delayed. These results are promising towards the use of Ph₂Se₂, alone or in combination with anti-herpetic drugs, in the treatment of udder and teat lesions produced by BoHV-2 in dairy cows.

Bovine Alphaherpesvirus 2 infections in Bavaria: an analysis of the current situation - several years after eradicating Bovine Alphaherpesvirus 1

Background

Bavaria, a large federal state in Germany, has been declared free from infections with Bovine Alphaherpesvirus 1 (BoHV-1) in 2011. To maintain this status the cattle population is monitored for antibodies against BoHV-1 regularly. Several years ago, infrequent but recurrent problems in this sero-surveillance were statistically put into correlation with the presence of antibodies against Bovine Alphaherpesvirus 2 (BoHV-2). In Europe, BoHV-2 is primarily known as the agent causing bovine herpes mammillitis. However, very little information about BoHV-2 infections in Bavaria is available so far. Therefore, the aims of this study were to determine BoHV-2 seroprevalences and to detect virus genomes in potential clinical samples.

Results

6801 blood sera of healthy cattle from all over Bavaria were tested for antibodies against BoHV-2, revealing an overall seroprevalence of 5.51%. Interestingly, seroprevalences markedly varied between the North and the South of Bavaria, namely from 0.42 to 11.17%. Concurrently, the previously reported relation between the epidemiologically inexplicable sero-reactivities in BoHV-1 ELISAs and the presence of BoHV-2 infections were statistically corroborated in this study. To detect BoHV-2 genomes a fast and sensitive real time PCR was established. Using a multiple PCR strategy, tissue samples from skin lesions at relevant localizations, corresponding lymph nodes, and trigeminal ganglia from 111 animals, as well as nasal swabs from 918 bovines with respiratory symptoms were tested. However, BoHV-2 genomes were not detected in any of these samples.

Conclusions

BoHV-2 antibodies were found in samples from bovines all over Bavaria, albeit with an explicit South-North-divide. BoHV-2 genomes, however, could not be detected in any of the analyzed samples, indicating that acute clinical cases as well as obvious virus reactivation are relatively rare. Consequently, the future spread of BoHV-2 infections throughout Bavaria, particularly, after eradicating BoHV-1, has to be further monitored.

Acute and latent infection by bovine herpesvirus type 2 in a guinea pig model

Bovine herpetic mammillits is a self-limiting cutaneous disease of the udder and teats of cows associated with bovine herpesvirus 2 (BoHV-2) whose pathogenesis is poorly understood. This article describes the use of guinea pigs (Cavia porcellus) to study the pathogenesis of BoHV-2 infection. Twelve weanling female guinea pigs inoculated subcutaneously with BoHV-2 in the genitalia and teats developed local hyperemia, edema, vesicles, ulcers and scabs. Infectious virus was recovered between days 3 and 7 post-infection (pi) from the genital area (9/12) and teats (1/12); and all inoculated animals seroconverted (virus-neutralizing titers of 16-128). Histological examination of lesions revealed lymphoplasmacytic perivascular infiltrates and intranuclear inclusion bodies in keratinocytes. PCR examination of tissues collected at day 35 pi detected latent viral DNA predominantly in lumbosacral spinal segments. In another experiment, eight females inoculated with BoHV-2 in the genitalia and treated with dexamethasone (Dx) at day 35 pi developed mild to moderate local signs, yet no virus could be recovered from lesions. PCR examination of spinal segments from these animals confirmed the presence of latent viral DNA. These results demonstrate that guinea pigs are susceptible to BoHV-2 infection and therefore may be used to study selected aspects of BoHV-2 biology.

Distribution of latent bovine herpesvirus 2 DNA in tissues of experimentally infected sheep

The biology of latent infection by bovine herpesvirus 2 (BoHV-2), the agent of mammillitis in cows, remains largely unknown. We herein report attempts to reactivate the latent infection and investigated the sites of BoHV-2 latency in experimentally infected sheep. Ewes inoculated with BoHV-2 in the udder's skin shed virus for up to five days, developed mammillitis and seroconverted. However, attempts to reactivate latent infection by dexamethasone administration at day 40 pi failed. Nevertheless, viral DNA--and not infectious virus--was detected by PCR in several nerve ganglia and/or regional lymph nodes (LNs) of all animals at day 40 post-reactivation. Likewise, lambs previously inoculated with BoHV-2 in the nose harbored latent viral DNA in trigeminal ganglia, tonsils and regional LNs. These results demonstrate that BoHV-2 establishes latent infection in nerve ganglia and in regional lymphoid tissues, yet virus reactivation is not easily achieved by standard protocols used.

Caracterização clinicopatológica da mamilite aguda em ovelhas lactantes infectadas experimentalmente com o herpesvírus bovino 2

A mamilite causada pelo herpesvírus bovino tipo 2 (BoHV-2) possui importante repercussão sanitária em gado leiteiro de alguns países, mas a sua patogenia permanece pouco conhecida. Este trabalho descreve a reprodução e caracterização da mamilite aguda em ovelhas lactantes inoculadas com o BoHV-2 na pele do úbere e dos tetos. Cinco de oito ovelhas inoculadas desenvolveram extensas placas com necrose focal, pequenas vesículas e formação de crostas nos locais de inoculação. As lesões foram inicialmente observadas no 4º dia pós-inoculação (pi), progrediram em extensão e gravidade até os dias 7-8pi e posteriormente regrediram. O vírus foi isolado das lesões entre os dias 7 e 8 pi. Antígenos virais e partículas típicas de herpesvírus foram demonstrados por microscopia eletrônica em biópsias de lesões coletadas nos dias 5, 6 e 10pi. Os achados histológicos foram caracterizados por necrose epitelial, erosões e úlceras, com formação de células sinciciais e infiltrado inflamatório linfoplasmocitário na derme. Associadas a essas lesões observaram-se inclusões eosinofílicas intranucleares em células epiteliais, sinciciais e inflamatórias. Em um segundo experimento, 7 de 10 cordeiros inoculados na mucosa nasal desenvolveram hiperemia e descarga nasal, bem como vesículas e erosões no focinho. O vírus foi isolado das secreções nasais por até três dias e todos os cordeiros soroconverteram ao BoHV-2. Tentativas de reativar a infecção latente pela administração de dexametasona no 40º dia pi foram infrutíferas, pois não foram observados re-excreção viral, recrudescência clínica ou soroconversão. Esses resultados demonstram que ovelhas são susceptíveis à infecção experimental pelo BoHV-2 e desenvolvem lesões semelhantes às observadas em casos naturais de mamilite herpética. Além disso, esses resultados sugerem o uso dessa espécie animal como modelo para o estudo de vários aspectos da biologia da infecção pelo BoHV-2.

Viral infections and bovine mastitis: a review

This review deals with the role of viruses in the aetiology of bovine mastitis. Bovine herpesvirus 1, bovine herpesvirus 4, foot-and-mouth disease virus, and parainfluenza 3 virus have been isolated from milk from cows with clinical mastitis. Intramammary inoculations of bovine herpesvirus 1 or parainfluenza 3 virus-induced clinical mastitis, while an intramammary inoculation of foot-and-mouth disease virus resulted in necrosis of the mammary gland. Subclinical mastitis has been induced after a simultaneous intramammary and intranasal inoculation of lactating cows with bovine herpesvirus 4. Bovine leukaemia virus has been detected in mammary tissue of cows with subclinical mastitis, but whether this virus was able to induce bovine mastitis has not been reported. Bovine herpesvirus 2, vaccinia, cowpox, pseudocowpox, vesicular stomatitis, foot-and-mouth disease viruses, and bovine papillomaviruses can play an indirect role in the aetiology of bovine mastitis. These viruses can induce teat lesions, for instance in the ductus papillaris, which result in a reduction of the natural defence mechanisms of the udder and indirectly in bovine mastitis due to bacterial pathogens. Bovine herpesvirus 1, bovine viral diarrhoea virus, bovine immunodeficiency virus, and bovine leukaemia virus infections may play an indirect role in bovine mastitis, due to their immunosuppressive properties. But, more research is warranted to underline their indirect role in bovine mastitis. We conclude that viral infections can play a direct or indirect role in the aetiology of bovine mastitis; therefore, their importance in the aetiology of bovine mastitis and their economical impact needs further attention.

Animal cytomegaloviruses

Cytomegaloviruses are agents that infect a variety of animals. Human cytomegalovirus is associated with infections that may be inapparent or may result in severe body malformation. More recently, human cytomegalovirus infections have been recognized as causing severe complications in immunosuppressed individuals. In other animals, cytomegaloviruses are often associated with infections having relatively mild sequelae. Many of these sequelae parallel symptoms associated with human cytomegalovirus infections. Recent advances in biotechnology have permitted the study of many of the animal cytomegaloviruses in vitro. Consequently, animal cytomegaloviruses can be used as model systems for studying the pathogenesis, immunobiology, and molecular biology of cytomegalovirus-host and cytomegalovirus-cell interactions.

The development and standardization of an enzyme-linked immunosorbent assay for the detection of antibodies to bovine herpesvirus 2

A single dilution enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to bovine herpesvirus 2 has been developed, standardized and compared with the virus neutralization test. The results of the two tests correlated well. A positive/negative threshold was established for the ELISA. The ELISA was reproducible, sensitive, rapid and specific.

Sensitivity of bovid herpesvirus 2 replication to temperatures found in the natural host

Two isolates of bovid herpesvirus 2 replicated poorly in bovine testicular cells and fetal kidney cells at 39--40 degrees C, temperatures commonly observed in virus-infected cattle. High viral titers occurred in replicate cultures at 30--37 degrees C. Persistent viral infections were noted in cultures maintained at 40 degrees C. Interferon-like activity was not responsible for the high-temperature restriction since the level was not significantly different between virus-infected cultures incubated at 35 degrees or 40 degrees C. Spontaneous viral inactivation was only three times as rapid at 41 degrees as at 35 degrees C. Analysis of temperature shift experiments with respect to results of growth studies and electron microscopy indicated a temperature sensitive event late in replication. The sensitivity of bovid herpesvirus 2 replication to elevated temperature provides a possible explanation for the extensive viral growth and occasionally severe lesions which are limited exclusively to the skin of infected cattle.

Twenty-five years of progress in understanding major infectious diseases of dairy cattle

Disease, whether it occurs in cats, cattle, caribou, or other species, is the manifestation of insult to the structural or functional integrity of the living being. Infection may occur with or without evidence of disease. Disease may represent only the “tip of the iceberg” of infection.

Prevalence of disease is the proportion of a defined population that meets specific criteria at a point in time, and incidence refers to the proportion of a defined population in which the onset occurs during a specifiable interval. Risk is an instantaneous rate of incidence.

Prevalence, incidence, and risk in infectious diseases are quantitative inferences derived from assessment of implications — caveats derived from variables that often are elusive, such as antibiotic resistance to plasmid mediated determinants transferable between species of enteric bacteria, or such as increases in population density among insect vectors influenced by climatic conditions favorable to the insects. Carefully orchestrated manipulation of the etiologic agent or the host response is made possible by ever-expanding understanding of the molecular biology of pathogenicity on the one hand and cellular and humoral immunity on the other. Such understanding often leads to new caveats or destroys old ones based on incomplete information.

This paper deals with a selected limited number of infectious diseases of dairy cattle. Knowledge developed around the cited parameters in 13 infectious diseases during the past quarter century is brought into focus. Ten geographically dispersed specialists in infectious diseases of cattle were asked to identify priorities among the array of transmissible diseases important to North America. Except for the mastitis syndrome, which will be given special attention elsewhere in these anniversary papers, the diseases discussed are those wherein major advances in knowledge or major needs for advanced knowledge were of special importance.

Latent infection of cattle with bovid herpesvirus 2

In a series of experiments, 10 calves were infected by different routes with bovine mammillitis strain of bovid herpesvirus 2 (BHV2). Nine of the calves developed lesions and BHV2 was isolated from 8 calves. At intervals, after clinical recovery, the calves were given a course of corticosteroid by intravenous injection. Subsequently 7 calves developed lesions and from 3 calves BHV2 was reisolated. The shortest interval between initial infection and reisolation of virus was 10 weeks. In one calf virus was recovered on 3 occasions, at intervals of 20, 44 and 74 weeks post-infection. It is probable that BHV2 can occur as a latent infection in calves and that BHV2 should be included among the herpesviruses known to remain latent.

Bovine herpes mammillitis of dairy cattle in Victoria

The occurrences of bovine herpes mammillitis in the Cohuna and Numurkah districts of northcentral Victoria is described. The disease was characterised by painful swollen teats, necrosis of variable areas of the teat skin, formation of blue-black scabs which sloughed leaving ulcers which were slow to heal. The outbreaks occurred during tspring months of October to mid-December when as many as 90% of milking cows in herds became infected. Epidemiologically the infection behaved as though it was transmitted by insects but proof of insect transmission was not attempted.

Experimental studies concerning the possibility of a latent carrier state in bovine herpes mammillitis (BHM)

Adult bovines, young calves and young rats were infected with bovine herpes mammillitis (BHM) virus providing a group of BHM-recovered animals in which to investigate a possible latent carrier state. The progression of the acute infection and serological response was essentially similar to that previously reported. The effect of natural (calving, littering) and artificial (corticosteroid treatment) stress on these animals following recovery from infection was investigated, but reactivation of BHM was never detected. Long term observation of cocultures of BHM virus infected-and-recovered bovine teat dermis with bovine embryo cells failed to reveal any evidence for the induction of BHM virus replication even in those cocultures treated with mitomycin C or bromodeoxyuridine. Similarly, cocultures utilizing lumbar dorsal root ganglia from the same animals were also negative with respect to the induction of virus replication. Experiments using cytosine arabinoside indicated that an artificial in vitro latent carrier state of BHM virus could be maintained for 6 days with subsequent sporadic virus reactivation, but an attempt to maintain such a state for 12 days was unsuccessful, with no subsequent virus reactivation.

Investigations of Allerton-type herpes virus infection in East African game animals and cattle

Neutralization tests with a strain (BA) of Allerton-type herpes virus, derived from a buffalo (Syncerus caffer) were carried out on 924 sera from 17 species of E. African game animals and on cattle sera from Tanzania (2001), Kenya (792) and Uganda (410).Buffalo populations throughout E. Africa showed a very high rate of infection, with all animals over 2 years of age serologically positive. Antibody was present in some giraffe, waterbuck and hippopotamus sera and, less frequently, in impala, eland, bushbuck and oryx. Data are provided on the titres of positive samples; the mean titre of buffalo sera increased with age.Cattle in many localities of N. Tanzania and S. Kenya showed a very high rate of infection, 85-95% of sera from animals more than 2-years old containing antibody; the titres recorded were lower than those in buffaloes. Very high infection rates were also found in Karamoja and Teso (Uganda) and also in some other areas of Kenya, whilst a considerably lower incidence of infection was detected in W. Nile Province of Uganda and in central Tanzania. Differences in infection rates may have been related to herd size and husbandry practices.It was shown that a wave of infection was probably spreading through cattle in N. Tanzania at about the same time as an outbreak of disease occurred in buffaloes and it is suggested that virus transmission may have been by biting flies.No clinical signs attributable to the virus were reported in cattle but mouth lesions similar to those recorded in buffaloes, or nasal lesions, could have passed undetected. Allerton-type virus probably produces a range of clinical syndromes in cattle, closely resembling those associated with some herpes viruses in primates but infection is seldom related in the field to either pseudo-lumpy skin disease, mammillitis or stomatitis.