Vaccines for Mycoplasma Diseases of Small Ruminants: A Neglected Area of Research

Mycoplasmas cause some of the most economically important diseases of sheep and goats, including diseases listed by the World Organisation for Animal Health (OIE) such as contagious caprine pleuropneumonia (CCPP) and contagious agalactia (CA). Other important mycoplasma diseases include chronic respiratory and arthritic syndrome (CRAS) and atypical pneumonia, both present on all continents where small ruminants are farmed. Unfortunately, owing to a lack of investment, most commercial vaccines for these diseases are of poor quality, being mostly composed of killed bacteriocins of dubious or unknown efficacy. Several Mediterranean laboratories produce autogenous vaccines, but these can only be used on farms where outbreaks have been officially declared, and consequently have limited impact on disease nationally. Effective live vaccines are available, but their use is often restricted because of safety concerns. With the necessary safeguards in place, we argue for their greater use. This review examines reported vaccines for mycoplasma diseases of small ruminants and attempts to identify new candidate antigens that may enable the development of improved products. Vaccines for CCPP are covered elsewhere.

​Caprine Respiratory Mycoplasmosis (Contagious Caprine Pleuropneumonia CCPP)- A Global Perspective of the Disease, Epidemiology, Diagnosis, Chemotherapy and Immunization: A Review

Mycoplasma infection of the respiratory tract of goats is prevalent worldwide including the South Asian sub-continent. Owing to intensive and large scale goat farming, the incidence of the disease is on an increase. Among various species of mycoplasma, Mycoplasma capricolum subspecies Capri pneumoniae is increasingly incriminated in Contagious Caprine Pleurapneumonia (CCPP) in goat populations with considerable economic fallout in the form of high morbidity and mortality. The disease manifestations in caprines are recorded as anorexia, high febrile reaction and respiratory embarrassment in the shape of clinical dyspnoea, polypnea, paroxysmal cough and sero-purulent nasal discharges. The disease is thus contracted by the healthy animals through aerosol, contaminated feed and water sources in the herd premises, without a protective immunity and that the conferred immunity in recovered cases being short-lived. The true lesions of CCPP are confined to the lung alveolar tissues of infected goats, which distinguish it from other respiratory diseases of small ruminants caused by the members of the Mycoplasma mycoides cluster. Atypical pneumonia caused by the mycoplasma infection of goats, also known as Contagious Caprine Pleuropneumonia (CCPP) has been more often reported from Africa and Asia than Europe. Classical, acute CCPP attributed to Mycoplasma capricolum subsp. Capri pneumoniae, originally known asthe F38 biotype (World Organisation for Animal Health, 2008) causes heavy kid mortality. Two other organisms in this group, M. mycoides subsp. capri and M. mycoides subsp. mycoides large-colony type, can cause disease in small ruminants that clinico-pathologically mimics CCPP but may have extra pulmonary signs and lesions, sometimes. Mycoplasma Capri pneumoniae and other members of the M. mycoides cluster cross-react in serological tests and share biochemical and genetic similarities. The most favourable epidemiological scenario in the Sub-continent is the hot humid climate during monsoons. The diversity and multi-etiological subspecies involved in the disease is detrimental in the development of an effective vaccine even though in some places a liquid vaccine is presently in use. At other places, anti-mycoplasmal antibiotics of aminoglycoside and fluoroquinolone and perhaps the macrolide groups remain to be the main option in preventing flock mortalities.

Alterations in acid-base balance, blood gases, and hematobiochemical profiles of whole-blood and thoracic fluid in goats with contagious caprine pleuropneumonia

Background and Aim: Contagious caprine pleuropneumonia (CCPP) is a highly contagious and fatal disease affecting goats and some wild ruminants. It is a cause of major economic losses in the goat industry in Africa, Asia, and the Middle East. This study aimed to investigate the acid-base balance, blood gases, and hematobiochemical profiles of whole-blood and fluid collected from the thoracic cavity in goats with CCPP. Materials and Methods: Fifty-five goats suffering from weight loss, anorexia, dyspnea, polypnea, cough, and nasal discharges due to CCPP were studied. Twenty-five healthy goats were used as controls. Diseased animals were enrolled in this study based on a positive serological latex agglutination test (LAT) that confirmed the detection of Mycoplasma capricolum subsp. capripneumoniae. The control goats were enrolled based on a negative result of the LAT. Results: Compared with a mean value of 7.38±0.04 in controls, the pH in the diseased group was 7.41±0.05. The blood pressure of carbon dioxide (PCO2), pressure of oxygen (PO2), base excess (BE), bicarbonate (HCO3), total carbon dioxide (TCO2), and saturation of oxygen (SO2) were lower in goats with CCPP than in controls. However, the anion gap (AnGap) was higher in the diseased goats than in the healthy ones. Compared with the levels in blood samples, the thoracic fluid PCO2, PO2, BE, and SO2 were higher while pH, HCO3, TCO2, and AnGap were lower. Compared with the findings in healthy goats, hematological alterations included significant increases in white blood cells and neutrophils, and a significant decrease in the red blood cell count. In the thoracic fluid, neutrophilic leukocytosis was a remarkable finding. The serum concentrations of globulin, blood urea nitrogen, and glucose, and the activities of aspartate aminotransferase (AST) and γ-glutamyl transpeptidase (GGT) increased significantly compared with those in controls. In contrast, serum concentrations of albumin, calcium, and magnesium, and the activity of alkaline phosphatase (ALP) decreased significantly compared with those of healthy animals. The activities of ALP, AST, GGT, and creatine kinase and the concentration of phosphorus were higher in thoracic fluid than the serum values in the diseased group. Conclusion: When compared with the healthy controls, goats with CCPP have metabolic acidosis. Compared with the levels in healthy goats, the blood PCO2, PO2, BE, HCO3, TCO2, and SO2 are low in goats with CCPP; however, the AnGap is higher in diseased goats.

Determination of Seroprevalence of Contagious Caprine Pleuropneumonia and Associated Risk Factors in Goats and Sheep Using Classification and Regression Tree

Classification and Regression Tree (CART) analysis is a potentially powerful tool for identifying risk factors associated with contagious caprine pleuropneumonia (CCPP) and the important interactions between them. Our objective was therefore to determine the seroprevalence and identify the risk factors associated with CCPP using CART data mining modeling in the most densely sheep- and goat-populated governorates. A cross-sectional study was conducted on 620 animals (390 sheep, 230 goats) distributed over four governorates in the Nile Delta of Egypt in 2019. The randomly selected sheep and goats from different geographical study areas were serologically tested for CCPP, and the animals’ information was obtained from flock men and farm owners. Six variables (geographic location, species, flock size, age, gender, and communal feeding and watering) were used for risk analysis. Multiple stepwise logistic regression and CART modeling were used for data analysis. A total of 124 (20%) serum samples were serologically positive for CCPP. The highest prevalence of CCPP was between aged animals (>4 y; 48.7%) raised in a flock size ≥200 (100%) having communal feeding and watering (28.2%). Based on logistic regression modeling (area under the curve, AUC = 0.89; 95% CI 0.86 to 0.91), communal feeding and watering showed the highest prevalence odds ratios (POR) of CCPP (POR = 3.7, 95% CI 1.9 to 7.3), followed by age (POR = 2.1, 95% CI 1.6 to 2.8) and flock size (POR = 1.1, 95% CI 1.0 to 1.2). However, higher-accuracy CART modeling (AUC = 0.92, 95% CI 0.90 to 0.95) showed that a flock size >100 animals is the most important risk factor (importance score = 8.9), followed by age >4 y (5.3) followed by communal feeding and watering (3.1). Our results strongly suggest that the CCPP is most likely to be found in animals raised in a flock size >100 animals and with age >4 y having communal feeding and watering. Additionally, sheep seem to have an important role in the CCPP epidemiology. The CART data mining modeling showed better accuracy than the traditional logistic regression.

Seroprevalence and Associated Risk Factors of Contagious Caprine Pleuropneumonia in the Small Ruminants of Oman

Contagious caprine pleuropneumonia (CCPP) is an economically important and potentially fatal disease of small ruminants caused by Mycoplasma capricolum subsp. capripneumoniae (Mccp). We designed this cross-sectional study to investigate the seroepidemiology of CCPP in the small ruminants of Oman. For this purpose, we sampled a total of 4015 small ruminants (2119 goats and 1896 sheep) from 510 flocks belonging to different governorates of Oman. A commercial competitive enzyme-linked immune-sorbent assay (cELISA) was used to test the samples. Prevalence (%) along with 95% confidence intervals (CI) was calculated, and a univariable analysis was conducted to screen different risk factors. Furthermore, a binary logistic regression model was built at the animal and flocklevel (Table 3). In total, 147 (28.8%, CI 24.9, 33.0) flocks tested positive for the CCPP and the seroprevalence ranged from 10.0 to 53.8% in various governorates (p = 0.001). The prevalence was significantly (P<0.001) high in goats (28%, CI 23.8, 32.5) as compared to sheep (13.1%, CI 24.9, 33.0). At flock level; the open herds (OR 2.08, 1.33, 3.27), having a location in the coastal regions (OR 1.70, 1.14, 2.53) and flock size of more than 100 animals (OR 2.45, 1.54, 3.91) were the significant risk factors for CCPP in Oman. At the animal level; goats (OR 2.87, CI 2.17, 3.81), and small ruminants above the age of one year (OR 2.23, CI 1.38-3.59) were found more likely to acquire CCPP. We suggest that a control program based on the changes in the management system to minimize the risk factors and a possible mass vaccination should be devised to check CCPP in Oman.

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

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.

Investigation of acute-phase proteins and cytokines response in goats with contagious caprine pleuropneumonia with special reference to their diagnostic accuracy

Acute-phase proteins (APPs) have always had valued diagnostic potentialities in response to infection. This study aimed to evaluate the diagnostic accuracy of selected APPs and proinflammatory cytokines (PIC) in goats with contagious caprine pleuropneumonia (CCPP) under field conditions. Moreover, to highlight the role of tested biomarkers in CCPP pathogenesis. Fifty-eight goats (38 confirmed cases with CCPP and 20 healthy controls) were involved in this investigation. C-reactive protein (CRP), procalcitonin (PCT), haptoglobin (HP), fibrinogen (Fb), serum amyloid A (SAA), selected PIC (IL1-α, IL1-β, IL-6, interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α)) levels were investigated in serum samples from all goats under investigation. Latex agglutination test was used for diagnosis of goats with CCPP. For microbiological investigations, nasopharyngeal swabs (from all goats), lung tissues and pleural fluids (from only necropsied goats) were collected. This study revealed that all tested parameters have a high to moderate degree of diagnostic performance for CCPP. Magnitudes of increase in levels of APPs (CRP, HP and SAA) were stronger than PIC, IFN-γ, Fb and PCT. All tested parameters showed high diagnostic accuracy (AUROC >90%), except HP (AUROC = 87.3%) and IFN-γ (AUROC = 78.8%) showed moderate accuracy in differentiation of goats with and without CCPP infection. For detecting goats with and without CCPP infection, HP had the lowest sensitivity (Se = 81.6%) and Fb had the lowest specificity (Sp = 85.0%) among the APPs parameters tested. However, PCT showed the highest Se (100%) and Sp (95.0%) to detect goats with and without CCPP infection among tested parameters. Conclusively, this study endorses the significance of selected APPs and PIC as additional screening diagnostic parameters for naturally occurring CCPP in goats. However, it does not replace traditional methods for diagnosis of CCPP in goats. Furthermore, APPs and PIC have an important role in disease pathogenesis in goats.