Co-Administration of Adjuvanted Recombinant Ov-103 and Ov-RAL-2 Vaccines Confer Protection against Natural Challenge in A Bovine Onchocerca ochengi Infection Model of Human Onchocerciasis

Onchocerciasis (river blindness), caused by the filarial nematode Onchocerca volvulus, is a neglected tropical disease mainly of sub-Saharan Africa. Worldwide, an estimated 20.9 million individuals live with infection and a further 205 million are at risk of disease. Current control methods rely on mass drug administration of ivermectin to kill microfilariae and inhibit female worm fecundity. The identification and development of efficacious vaccines as complementary preventive tools to support ongoing elimination efforts are therefore an important objective of onchocerciasis research. We evaluated the protective effects of co-administering leading O. volvulus-derived recombinant vaccine candidates (Ov-103 and Ov-RAL-2) with subsequent natural exposure to the closely related cattle parasite Onchocerca ochengi. Over a 24-month exposure period, vaccinated calves (n = 11) were shown to acquire infection and microfilaridermia at a significantly lower rate compared to unvaccinated control animals (n = 10). Furthermore, adult female worm burdens were negatively correlated with anti-Ov-103 and Ov-RAL-2 IgG1 and IgG2 responses. Peptide arrays identified several Ov-103 and Ov-RAL-2-specific epitopes homologous to those identified as human B-cell and helper T-cell epitope candidates and by naturally-infected human subjects in previous studies. Overall, this study demonstrates co-administration of Ov-103 and Ov-RAL-2 with Montanide™ ISA 206 VG is highly immunogenic in cattle, conferring partial protection against natural challenge with O. ochengi. The strong, antigen-specific IgG1 and IgG2 responses associated with vaccine-induced protection are highly suggestive of a mixed Th1/Th2 associated antibody responses. Collectively, this evidence suggests vaccine formulations for human onchocerciasis should aim to elicit similarly balanced Th1/Th2 immune responses.</jats:p

Bacterial Pathogens Involved in Bovine Mastitis and Their Antibiotic Resistance Patterns in the Adamawa Region of Cameroon

Data on the sensitivity pattern of bacteria are scarce in sub-Saharan Africa, especially in Cameroon. This paper reports the prevalence of bovine mastitis and major bacterial pathogens associated with the disease and their antimicrobial profiles in the Adamawa Region of Cameroon. It was conducted to investigate the sensitivity pattern of bacteria isolated from mastitis cases that could be helpful in the application of appropriate therapeutic measures. For this study, 224 lactating cows were examined. A high average prevalence (59.8%) in subclinical mastitis was recorded as compared to clinical mastitis (3.6%; χ2=163.7, P=10-4). Out of the 135 clinical and subclinical mastitis cases recorded, bacteria were cultured from 115 milk samples (85.2%, n=135). In all, 14 different bacterial pathogens were isolated including: coagulase negative Staphylococci (27.5%), Staphylococcus aureus (23.3%), Escherichia coli (11.3%), Streptococcus agalactiae (7.1%), Streptococcus dysagalactiae (4.2%), Enterococcus faecalis (2.8%), Klebsiella pneumoniae (2.8%), Enterobacter aerogenes (2.1%), Pseudomonas aeruginosa (2.1%), Corynebacterium spp. (1.4%), Proteus spp. (1.4%), Brucella spp. (1.4%), Mycoplasma spp. (0.7%), and Mycobacterium spp. (0.7%). A major variationin the sensitivity of isolated bacteria against 14 different antibiotics was noticed. Overall the sensitivity test revealed that Enrofloxacin, Gentamicin, and to a lesser extent Oxacillin and Amoxicillin/Clavulanic acid, were most efficacious. The study gives a significant contribution to the epidemiology and contributes to reducing the lack of knowledge about the antibiotic resistance patterns of major bacterial mastitis in Cameroon. The application of these antibiotics could be beneficial in resolving the cases of bovine mastitis in dairy herds. Keywords: Antibiotic resistance; Cameroon: Cattle; Mastitis; Pathogenic bacteria

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