Approaches to increase recovery of bacterial and fungal abortion agents in domestic ruminants

Abstract

Abortions in domestic ruminants cause significant economic losses to farmers. Determining the cause of an abortion is important for control efforts, but it can be challenging. All available diagnostic methods in the bacteriology laboratory should be employed in every case due to the many limiting factors (autolysis, lack of history, range of samples) that complicate the investigation process. The purpose of this study was to determine whether the recovery of diagnostically significant isolates from domestic ruminant abortion cases could be increased through the use of a combination of the existing aerobic culture and Brucella selective method with methods that are commonly recommended in the literature reporting abortion investigations. These methods are examination of wet preparations and impression smears stained by the modified Ziehl–Neelsen method, anaerobic, microaerophilic, Leptospira, Mycoplasma and fungal culture. Samples of placenta and aborted foetuses from 135 routine clinical abortion cases of cattle (n = 88), sheep (n = 25) and goats (n = 22) were analysed by the new combination of methods. In 46 cases, bacteria were identified as aetiological agents and in one case a fungus. Isolation of Brucella species increased to 7.4% over two years compared with the previous 10 years (7.3%), as well as Campylobacter jejuni (n = 2) and Rhizopus species (n = 1). Salmonella species (5.9%) and Trueperella pyogenes (4.4%) were also isolated more often. In conclusion, the approach was effective in removing test selection bias in the bacteriology laboratory. The importance of performing an in-depth study on the products of abortion by means of an extensive, combination of conventional culture methods was emphasised by increased isolation of Brucella abortus and isolation of C. jejuni. The combination of methods that yielded the most clinically relevant isolates was aerobic, microaerophilic, Brucella and fungal cultures.

Optimization and Application of Real-Time qPCR Assays in Detection and Identification of Chlamydiales in Products of Domestic Ruminant Abortion

“…In two cases, Chlamydia had been detected previously by immunohistochemistry [ 36 ] and, in this study, Chlamydiales were again detected using qPCR. In eight cases, no Chlamydiales were detected in this study or the previous study by Jonker et al [ 41 ]. A cut-off point (10 6 DNA copies) experimentally determined by Gutierrez et al [ 37 ] was applied to C. abortus results to determine diagnostic significance of results.…”

“…Chlamydiales were detected in samples from two ovine cases, C. pecorum in one case and W. chondrophila in the other, where only pathological lesions pointing to an infectious cause were reported previously by Jonker et al [ 41 ]. Lack of any other possible agents of abortion increases their significance in these cases.…”

“…All 25 clinical bovine, ovine and caprine abortion cases where necrotic placentitis and/or pneumonia were reported were selected from the 135 clinical abortion cases in the same study [ 41 ]. Fifty samples (17 placentas, 19 stomach contents, 14 lungs) from these 25 cases were analysed in this study.…”

“…DNA from 49 samples (14 placenta, 17 stomach content, 18 lung) from clinical ruminant abortion cases (13 bovine, 9 ovine, 10 caprine), which were available from a previous study [ 41 ], were used in specificity and limit of detection analyses. Only samples that had pathological lesions other than placentitis or pneumonia, or no lesions were selected.…”

Ecology and Management of the African Buffalo

“…The infection in these species is generally subclinical due to the evolution of disease resistance over millennia and the development of an endemically stable host/pathogen relationship. Helmeted guineafowl, leopard tortoises and scrub hares, which are the preferred hosts of the larval and nymph stages of this vector, may also harbour this pathogen (Oberem and Bezuidenhout, 1987). All of these silent carriers may potentially serve as sources of infection for the vector ticks, which theoretically could infect livestock in an open interface situation where livestock and wildlife share range and resources.…”