Diagnosis of tuberculosis in wildlife
Animal tuberculosis is a multi-host disease caused by members of the Mycobacterium tuberculosis complex. Due to its impact on the economy, sanitary standards of the milk and meat industry, public health and conservation, TB control is an immensely important ongoing research subject. Several wildlife species are involved in the maintenance and transmission of TB, so that new approaches to wildlife TB diagnosis have gained relevance in recent years. Diagnosis is a paramount step for screening, epidemiological investigation, as well as for ensuring the success of control strategies such as vaccination trials. This open access paper by Thomas et al (2021) (Veterinary Research https://doi.org/10.1186/s13567-020-00881-y) is the first review that systematically addresses data available for the diagnosis of TB in wildlife following the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The article also gives an overview of the factors related to host, environment, sampling, and diagnostic techniques which can affect test performance. After three screenings, 124 articles were considered for systematic review. Literature indicates that post-mortem examination and culture are useful methods for disease surveillance, but immunological diagnostic tests based on cellular and humoral immune response detection are gaining importance in wildlife TB diagnosis. Among them, serological tests are especially useful in wildlife because they are relatively inexpensive and easy to perform, facilitate large-scale surveillance and can be used both ante- and post-mortem. Currently available studies assessed test performance mostly in cervids, European badgers, wild suids and wild bovids. The authors conclude that further research to improve diagnostic tests for wildlife TB diagnosis is still needed in order to reach accurate, rapid and cost-effective diagnostic techniques adequate to a broad range of target species and consistent over space and time to allow proper disease monitoring.
Psoroptic mange in cattle
Psoroptic mange is a common disease of live-stock, caused by Psoroptes ovis. Compared to Holstein–Friesian (HF) cattle, the Belgian Blue (BB) cattle breed is highly susceptible to the infestation. However, the mechanism for this difference is still unclear. To determine the factors responsible for this breed susceptibility, the immune response to P. ovis was studied in experimentally infested BB and HF cattle, using clinical signs, histology, immunohistochemical profiling and gene expression analysis of skin biopsies by Chen et al (2021) (Veterinary Research https://doi.org/10.1186/s13567-020-00874-x) in their open access paper. The mite numbers and lesion area of BB cattle were greater than in HF during the whole study period. Significant influxes of eosinophils in the epidermis and dermis were detected in comparison with the pre-infestation samples in both breeds, with significantly higher eosinophils in BB at 6 weeks post infestation (wpi). Mast cell numbers were unaffected at all stages of infestation in HF, but were significantly elevated relative to pre-in-festation in BB cattle at 2 and 6 wpi. The more pronounced cutaneous eosinophilia and higher IL-4 levels at 6 wpi in BB cattle suggest that a Th2-type immune response is underlying the higher susceptibility of the BB breed. In naturally infested BB cattle, development of the psoroptic mange lesions and eosinophils and CD3+ T cell areas were severely depressed after anti-inflammatory treatment with dexamethasone. Together, these results suggest that a stronger Th2-type immune response to P. ovis causes the skin lesions in psoroptic mange in BB cattle and that local anti-inflammatory treatment could potentially be beneficial to control the pathology caused by this parasite.
Udder cleft dermatitis
Udder cleft dermatitis (UCD) or udder sores is a skin lesion, characteristically located around the anterior junction between the udder and abdomen of dairy cows. It is a worldwide problem in dairy herds with a large effect on animal welfare. The aetiology and possible infectious origins of UCD are largely unknown; however, specific bacterial or parasitic causes are suggested in the literature. Therefore, the aim of this study by van Engelen et al (2021) (Journal of Dairy Science https://doi.org/10.3168/jds.2020-18414) was to investigate the possible bacteriological, mycological, or parasitic involvement in clinically scored UCD lesions. Bacteriological culture was performed on subcutaneous tissue samples taken post-mortem at a depth of 5 to 10 mm of 87 mild or severe UCD lesions or from the same place in healthy cows. Fungal culture was performed on a subset of 22 subcutaneous tissue samples of severe UCD post-mortem. To investigate the superficial flora, swabs were taken from normal skin or skin lesions of 15 live animals equally divided over three groups: healthy skin or mild and severe UCD lesions. Histopathology, to describe and classify the lesions and to assess the presence of mites, fungi, or bacteria, was performed on 128 tissue samples, taken separately. In severe UCD lesions, Trueperella pyogenes and Bacteroides pyogenes were more frequently present in deep tissue layers and in superficial layers, compared with the same layers in mild UCD lesions or healthy skin. Culturing and histopathology indicated no sign of involvement of treponemes, Staphylococcus aureus, Escherichia coli, fungi, or mites in the UCD lesions. Histopathological examination showed that most of the lesions were characterised by chronic aspecific in-flammation. Severe UCD lesions more frequently showed chronic active inflammation on histopathology, compared with mild UCD lesions. Due to the cross-sectional character of this study, it is difficult to differentiate cause and effect; however, the authors advise that future preventive and curative measures against UCD should consider the chronic and anaerobic nature of this condition.