Infection exposure, detection and causes of death in perinatal mortalities in Polish dairy herds

Abstract

The objective of this study was to determine the prevalence and types of infections in perinatal mortality (PM) cases from Polish dairy farms and the relevance of the presence of infection to the cause of death. This prospective longitudinal study was carried out on 121 PM and 21 control calves with a gestation of ≥260 days. Six control calves were euthanized and examined using the same protocol as for PM calves. Material was collected over a 20-month period between November 2013 and June 2015. The PM and control calves were collected from 29 to 5 herds, respectively. Blood samples from calves were tested for antibodies to Neospora caninum, glycoprotein B of BoHV-1, BVDV and SBV using ELISAs and Leptospira hardjo and Leptospira pomona with the microscopic agglutination test. Brain and kidney samples from all PM and six euthanized control calves were tested using real time PCR to detect Neospora caninum, pathogenic Leptospira spp., BoHV-1 and SBV; brain was examined histopathologically for detection of N. caninum cysts. Samples from eight inner organs from all PM and six control calves were cultured aerobically, anaerobically and microaerobically. Ear samples from all PM and control calves were tested for BVDV using an antigen ELISA. In total, 21.5% of PM calves were infected (antigen and/or antibody-positive) in utero; none of the control calves were infected. Direct evidence of infection (culture, Ag-ELISA, PCR, histopathology) was detected in 9.1% of PM calves. Gestation length in infected singletons was shorter than in uninfected singletons (274 ± 8 vs. 279 ± 7 days; P < 0.01). The odds ratio for diagnosis of infection in single pregnancies ≤275 days was 3.75 (95% CI:1.2-12.1), (P < 0.05). Infection was the cause of death in 10% of calves. The most common infections detected in these Polish PM calves were parasitic (11.6% of PM cases), viral (7.4%) and bacterial (5%). This study demonstrated that indirect evidence of infection is detected more frequently than direct, coinfection is rare, infection is rarely accompanied by gross lesions and is rarely a cause of death in cases of PM.

Perinatal immuno/inflammatory responses in the presence or absence of bovine fetal infection

“…In calf plasma, pathogen-specific antibodies were measured: Neospora caninum , glycoprotein B of BoHV-1 and BVDv using the IDEXX Neospora Ab Test, IDEXX IBR gB X3 Ab Test and IDEXX BVDV Total Ab Test (Hoofddorp, The Netherlands), SBV using the Serological ID Screen Schmallenberg Virus Competition Multi-Species ELISA (ID-vet, Grabels, France), Leptospira hardjo and Leptospira pomona using live strains of L. hardjo and L. pomona in the microscopic agglutination test at the veterinary diagnostic laboratory as described in Jawor et al [ 7 ] and Coxiella burnetii in the IDEXX Q Fever Ab Test (Hoofddorp, The Netherlands) (Krol et al, unpublished).…”

“…The first PM group (PM INF+; n = 22) included only calves in which pathogen-specific antibodies (BVDv, n = 3; Coxiella burnetii, n = 6; Leptospira hardjo , n = 3 , Leptospira hardjo and L. pomona , n = 1; Neospora caninum , n = 5 or SBV, n = 4), but not antigens, were detected. Calves with infection in utero diagnosed by the detection of antigen/s [ 7 ] were excluded from the study as multiple infections and co-infections were detected and their number was too small for statistical analyses ( n = 10). Diagnosis of infection was made only in the calves, not their dams.…”

“…While much of this loss has been attributed to dystocia [ 6 ], an increasing proportion of calf loss occurs at eutocia (‘the unexplained stillbirth’). Some of this loss is caused by infections [ 7 ]. But, given the limitations in detecting infectious agents in calf carcasses, current estimates of the proportion of loss attributable to infections may underestimate the extent of their contribution.…”

Investigation of bovine abortion and stillbirth/perinatal mortality - similar diagnostic challenges, different approaches

“…In aborted foetuses the COD are often attributed to events which occurred days or weeks before foetal death so few COD lesions will be grossly visible; microbiological sampling is more important. However, in stillborn calves the COD is more likely to be periparturient [40] rather than infection-related [41] though preexisting congenital defects [42] and precalving nutrition [43] can also contribute to perinatal mortality. Hence gross examination can often reveal more than laboratory testing.…”

Cell-mediated transfer of immune protection factors to newborn calves

“…It is considered recognized that animals in the first days of life are characterized by immunological immaturity associated with poor development of lymphoid tissue and the absence of immunocompetent cells. The maternal organism compensates for this immaturity of the newborn by transferring ready-made antibodies to it, for a short time protecting the offspring from a number of pathogens [4,5].…”