The relationship between antibody status to bovine corona virus and bovine respiratory syncytial virus and disease incidence, reproduction and herd characteristics in dairy herds

Abstract

BackgroundBovine respiratory syncytial virus (BRSV) and bovine corona virus (BCV) affects cattle worldwide. Our objective was to evaluate the effects of these infections on general health and reproduction parameters measurable on herd level and to explore the association between antibody status and some herd characteristics.MethodsWe collected a pooled milk sample from five primiparous cows from 79 Swedish dairy herds in September 2006. The samples were analysed for immunoglobulin G antibodies to BCV and BRSV with indirect enzyme-linked immunosorbent assays. Herd level data from 1 September 2005 to 30 August 2006 were accessed retrospectively. The location of the herds was mapped using a geographical information system.ResultsTen herds were antibody negative to both viruses and were compared with 69 herds positive to BCV or BRSV or both. Positive herds had a higher (P = 0.001) bulk tank milk somatic cell count (BMSCC) compared with negative herds. The medians for all other analyzed health and reproductive parameters were consistently in favour of the herds negative to both viruses although the differences were not statistically significant. A higher proportion (P = 0.01) of herds used professional technicians for artificial insemination, rather than farm personnel, amongst the 33 herds negative to BCV compared with the 46 positive herds.ConclusionsOur result shows that herds that were antibody positive to BCV and/or BRSV had a higher BMSCC compared with herds negative to BCV and BRSV. There was also tendency that negative herds had a better general herd health compared with positive. A higher proportion amongst the BCV negative herds used external technicians for AI instead of farm personnel, indicating that it is possible to avoid infection although having regular visits. Negative herds were located in close proximity to positive herds, indicating that local spread and airborne transmission between herds might not be of great importance and that herds can stay free from these infection transmission although virus is circulating in the area.

Herd level estimation of probability of disease freedom applied on the Norwegian control program for bovine respiratory syncytial virus and bovine coronavirus

“…As mentioned, PostPFree relates to presence of antibodies and not necessarily presence of virus. Ideally, one would prefer to use a test detecting the antigen itself in order to achieve a herd's true infection status; however, this is demanding to do on a large scale, and antibody testing is commonly used (Hägglund et al, 2006;Beaudeau et al, 2010;Ohlson et al, 2010a). Animal purchase might mean introducing an antibody positive animal and not necessarily introducing virus.…”

Phylogenetic analysis of bovine respiratory syncytial viruses from recent outbreaks in feedlot and dairy cattle herds

“…This indicates that BRSV is circulating between herds throughout the year, which is important knowledge for outlining strategies to prevent the inter-herd spread of BRSV. Control of BRSV can be achieved by improved biosecurity measures [28] or vaccination. Live and inactivated vaccines against BRSV are used around the world, but their efficiency has been questioned [12,27,37].…”

“…A high herd prevalence of BRSV was also reported in Danish dairy herds [26], and the infection is regarded as one of the most important welfare and economic problems in the Danish beef industry, associated with a high mortality among calves and a high rate of antibiotic treatment [27]. Studies have shown that there are negative effects associated with BRSV infections on herd health and animal performance [22,28] and an association between a high biosecurity level and lower herd prevalence [23]. There is, however, limited information about similarity and evolutionary relationship among the BRSV strains in the Swedish cattle population.…”

Epidemiology, Molecular Epidemiology and Evolution of Bovine Respiratory Syncytial Virus

“…Intra-herd transmission usually occurs by aerosols, allowing the virus to enter susceptible cattle via the respiratory tract. However, local spread and airborne transmission between herds are not of great importance for inter-herd transmission despite the circulation of BRSV in a given geographical region [8]. On the other hand, direct transmission between herds is frequently a consequence of the introduction of new infected animals, while indirect transmission occurs by individuals visiting farms.…”

“…Some of the main risk factors for BRSV transmission include large herd size and common farm practices such as not providing boots to visitors and dual-purpose farms [9,10]. Additionally, it has also been proposed that good management and better hygienic routines have a direct impact on overall health status [8]. …”