Baseline analysis of Mycoplasma mycoides subsp. mycoides antigens as targets for a DIVA assay for use with a subunit vaccine for contagious bovine pleuropneumonia.

BACKGROUND: Mycoplasma mycoides subsp. mycoides (Mmm) is the causative agent of contagious bovine pleuropneumonia in cattle. A prototype subunit vaccine is being developed, however, there is currently no diagnostic test that can differentiate between infected cattle and those vaccinated with the prototype subunit vaccine. This study characterized Mmm proteins to identify potential antigens for use in differentiating infected from vaccinated animals. RESULTS: Ten Mmm antigens expressed as recombinant proteins were tested in an indirect ELISA using experimental sera from control groups, infected, and vaccinated animals. Data were imported into R software for analysis and drawing of the box and scatter plots while Cohen's Kappa assessed the level of agreement between the Mmm antigens. Two vaccine antigens (MSC_0499 and MSC_0776) were superior in detecting antibodies in sera of animals vaccinated with the subunit vaccines while two non-vaccine antigens (MSC_0636 and LppB) detected antibodies in sera of infected animals showing all clinical stages of the disease. Sensitivity and specificity of above 87.5% were achieved when the MSC_0499 and MSC_0636 antigens were tested on sera from vaccinated and infected animals. CONCLUSIONS: The MSC_0499 and MSC_0776 antigens were the most promising for detecting vaccinated animals, while MSC_0636 and LppB were the best targets to identify infected animals. Further testing of sera from vaccinated and infected animals collected at different time intervals in the field should help establish how useful a diagnostic test based on a cocktail of these proteins would be.

Volunteer based approach to dog vaccination campaigns to eliminate human rabies: Lessons from Laikipia County, Kenya.

BACKGROUND: An estimated 59,000 people die from rabies annually, with 99% of those deaths attributable to bites from domestic dogs (Canis lupus familiaris). This preventable Neglected Tropical Disease has a large impact across continental Africa, especially for rural populations living in close contact with livestock and wildlife. Mass vaccinations of domestic dogs are effective at eliminating rabies but require large amounts of resources, planning, and political will to implement. Grassroots campaigns provide an alternative method to successful implementation of rabies control but remain understudied in their effectiveness to eliminate the disease from larger regions. METHODOLOGY/PRINCIPAL FINDINGS: We report on the development, implementation, and effectiveness of a grassroots mass dog rabies vaccination campaign in Kenya, the Laikipia Rabies Vaccination Campaign. During 2015-2017, a total of 13,155 domestic dogs were vaccinated against rabies in 17 communities covering approximately 1500 km2. Based on an estimated population size of 34,275 domestic dogs, percent coverages increased across years, from 2% in 2015 to 24% in 2017, with only 3 of 38 community-years of vaccination exceeding the 70% target. The average cost of vaccinating an animal was $3.44 USD with in-kind contributions and $7.44 USD without in-kind contributions. CONCLUSIONS/SIGNIFICANCE: The evolution of the Laikipia Rabies Vaccination Campaign from a localized volunteer-effort to a large-scale program attempting to eliminate rabies at the landscape scale provides a unique opportunity to examine successes, failures, and challenges facing grassroots campaigns. Success, in the form of vaccinating more dogs across the study area, was relatively straightforward to achieve. However, lack of effective post-vaccination monitoring and education programs, limited funding, and working in diverse community types appeared to hinder achievement of 70% coverage levels. These results indicate that grassroots campaigns will inevitably be faced with a philosophical question regarding the value of local impacts versus their contributions to a larger effort to eliminate rabies at the regional, country, or global scale.

Seroprevalence of canine neosporosis and bovine viral diarrhoea in dairy cattle in selected regions of Kenya.

Neospora caninum is the causative agent for canine neosporosis (CN), a disease of potential zoonotic importance causing reproductive losses in cattle while causing neuromuscular disease in dogs. Bovine viral diarrhoea on the other hand is caused by the bovine viral diarrhoea virus (BVDV) and is one of the most important reproductive diseases of cattle worldwide. In Kenya, these infections are of economic importance due to the losses they cause in farms in which they are diagnosed or are subclinical. Such losses include reduced milk production, reduced conception, early embryonic deaths and abortions which lead to reproductive wastage. This study was conducted between April 2017 and July 2018 and determined the seroprevalence of neoporosis and BVD in select dairy herds in Kenya. Kakamega, Nandi and Makueni Counties from where dairy farms were purposively sampled were used. Serum samples were collected from randomly selected dairy animals aged at least 2 years in the selected farms and screened for BVDV and CN antibodies. Seroprevalence of N. caninum was 24.1% (n = 552) and BVD, 52.3% (n = 545) across all the counties. Co-infection where antibodies against the two infective agents were present was in 14.6% (n = 541) animals. Chi-square tests of association between prevalence and county were significant for BVD (p = .000) but not for neosporosis (p = .626). Further chi-square tests of association between the two infections were not significant (p = .105) neither were the associations of BVD (p = .575) and neosporosis (p = .626) on pregnancy status. These two diseases are rarely investigated as causes of bovine infertility. Detection of antibodies in the studied dairy herds underpins the need for enhanced surveillance by laboratories and for further studies to understand associated risk factors to formulate effective control strategies in dairy cattle to forestall abortions and production and reproduction losses.

Capsular polysaccharide from Mycoplasma mycoides subsp. mycoides shows potential for protection against contagious bovine pleuropneumonia.

Contagious Bovine Pleuropneumonia (CBPP) is a severe respiratory disease caused by Mycoplasma mycoides subsp. mycoides (Mmm) which is widespread in Africa. The capsule polysaccharide (CPS) of Mmm is one of the few identified virulence determinants. In a previous study, immunization of mice against CPS generated antibodies, but they were not able to prevent multiplication of Mmm in this model animal. However, mice cannot be considered as a suitable animal model, as Mmm does not induce pathology in this species. Our aim was to induce antibody responses to CPS in cattle, and challenge them when they had specific CPS antibody titres similar or higher than those from cattle vaccinated with the live vaccine. The CPS was linked to the carrier protein ovalbumin via a carbodiimide-mediated condensation with 1-ethyl-3(3-imethylaminopropyl) carbodiimide (EDC). Ten animals were immunized twice and challenged three weeks after the booster inoculation, and compared to a group of challenged non-immunized cattle. When administered subcutaneously to adult cattle, the vaccine elicited CPS-specific antibody responses with the same or a higher titre than animals vaccinated with the live vaccine. Pathology in the group of immunized animals was significantly reduced (57%) after challenge with Mmm strain Afadé compared to the non-immunized group, a figure in the range of the protection provided by the live vaccine.