Diagnosis Challenges and Control Strategies of Transboundary Diseases Presenting with Respiratory Signs in Small Ruminants in Developing Countries: Emphasis on Contagious Caprine Pleuropneumonia and Peste Des Petits Ruminants

Abstract

Aims: To review the diagnosis challenges and control strategies of the diseases presenting with respiratory signs. The emphasis being more on two transboundary animal diseases of small ruminants; contagious caprine pleuropneumonia (CCPP) and peste des petits ruminants (PPR). Clinical signs and postmortem lesions associated with the two diseases were also explicated.
 Study Design: Review.
 Place and Duration of Study: Department of Global Health, School of Life Science and Bio-Engineering (LiSBE), Nelson Mandela African Institution of Science and Technology (NM-AIST) from December 2017 to June 2020.
 Methodology: A comprehensive review was carried out following Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. A total of 506 articles, handbooks, Master’s and PhD thesis and conference proceedings were collected and after removal of the duplicates 80.6% (424/526) passed the first stage. Of the remaining search materials, (n=291) were removed including handbooks, master’s and PhD thesis which did not originate from the developing countries, 31.4% (133/424) passed the second. Of the articles that passed the second stage, (n=85) were removed from the study, these included all articles that did not involve field diagnosis such as review papers and those not originating from the developing countries, 36.1% (48/133) passed the third stage. In the fourth stage, (n=5) articles which reported on retrospective cases and archived samples were removed and 43 articles were reviewed.
 Results: Out of the 526 documents retrieved, 43 were eligible for review as they met all criteria for inclusion. Control strategies were recommended in 44.2% (19/43) of the articles of which most of them 63.2%, 12/19) recommended vaccination as a control strategy. Most of the articles reported definitive diagnosis reached following laboratory involvement as majority of them involved outbreak investigation or research works which is not the case in routine diagnosis. The major clinical signs mentioned in the review articles including fever 60.9% (14/23), oculonasal discharge 87.0% (20/23), respiratory distress 82.6% (19/23), erosive stomatitis 43.5% (10/23), diarrhea 56.5% (13/23) and coughing 30.4% (7/23) have been discussed relating to the definitive diagnosis reached in reporting articles. On the other hand, postmortem lesions including lung consolidation 38.1% (8/21), intestinal hemorrhage 38.1% (8/21), lung congestion 28.6% (6/21), serofibrinous pleurisy 28.6% (6/21), pneumonic lungs 23.8% (5/21) and unilateral lung inflammation 14.3% (3/21), have been discussed in relation to the definitive diagnosis reached. 
 Conclusion: Despite the similarities in clinical signs and postmortem lesions associated with diseases presenting with respiratory signs, definitive diagnosis of CCPP was reached in cases that involved clinical signs and postmortem lesions confined in the respiratory system whereas, PPR was more diagnosed in cases that presented with clinical signs and postmortem lesions associating the digestive system. However, presence of respiratory signs in the cases the diagnosed PPR may implicate presence of unidentified secondary bacterial infections. Vaccinations being the most advocated approach of control, require a broader look to make sure that polyvalent vaccines are available against the four common diseases. Also, use of treatment to reduce the effect of secondary infecting bacteria may be of help. Furthermore, for effective outcomes of the control strategies, collaborative efforts among countries at risk should be advocated.