Serotyping, antibiogram, and detection of bacterial pathogens associated with bovine respiratory disease in selected areas of Ethiopia

Background

Bovine Respiratory Disease (BRD) is a multifactorial and economically important illness of cattle. The current study was designed to characterize the major bacterial pathogens associated with BRD and determine the antibiotic susceptibility patterns of isolates. Samples were collected from 400 pneumonic cases of cattle.

Results

Laboratory assay revealed isolation of 376 (94.0%) bacterial pathogens. The most prevalent bacterial pathogens recovered were Mannheimia haemolytica (M. haemolytica) followed by Pasteurella multocida (P. multocida), Histophilus somni (H. somni), and Bibersteinia trehalosi (B. trehalosi) from 191 (50.80%), 81 (21.54%), 56 (14.89%), and 48 (12.77%) samples, respectively. M. haemolytica strains were confirmed using multiplex PCR assay through the amplification of PHSSA (~ 325 bp) and Rpt2 (~ 1022 bp) genes. Capsular typing of P. multocida revealed amplification of serogroup A (hyaD-hyaC) gene (~ 1044 bp) and serogroup D (dcbF) gene (~ 657 bp). B. trehalosi isolates displayed amplification of the sodA gene (~ 144 bp). Besides, serotyping of M. haemolytica showed the distribution of serotype A:1 (82.20%), A:2 (10.47%), and A:6 (7.33%). Whereas, biotyping of P. multocida revealed a higher prevalence of biotype A:3 (83.95%), then A:1 (8.64%), A:2 (4.94%), and A:12 (2.47%). The majority of the retrieved isolates showed remarkable susceptibility to enrofloxacin, ciprofloxacin, sulfamethoxazole-trimethoprim, florfenicol, and ceftiofur (100%). Besides, varying degree of antimicrobial resistance was observed against streptomycin, gentamicin, penicillin-G, and ampicillin.

Conclusions

The current findings confirmed that M. haemolytica (A:1) strain is the most common bacterial pathogen identified from BRD cases in the study areas of Ethiopia. Hence, continuous outbreak monitoring and evaluation of antibiotics susceptibility patterns of bacterial pathogens associated with BRD are indispensable to reduce the impact of BRD in the study areas. Further investigation of bacterial pathogens and genotypic analysis of pathogens from a wider area of the country is essential to design a cost-efficient control strategy.

Bacteriological findings and hormonal profiles in the postpartum Balady goats

Twenty-six Balady goats categorized according to parity into primiparous and pluriparous goats were used to investigate bacterial flora of the genital tract and hormonal profiles during the postpartum (PP) period. Escherichia coli and Staphylococcus aureus were isolated in pure or mixed culture from the uterus. Arcanobacterium pyogenes was isolated from swabs obtained from the vagina and cervix of one primiparous goat. Uteri and cervices but not vaginas were free of bacterial contamination by day 10 PP except for one pluriparous goat with scanty E. coli contamination on day 25 PP. Fluctuating oestradiol 17beta (E2) levels demonstrated resumption of follicular activity as early as day 13 PP in both parity groups. Progesterone (P4) levels remained low at basal levels throughout the study period. Higher concentrations of 15-keto-13,14-dihydroprostaglandin F2alpha (PGFM) were observed during the first week PP compared with the rest of the PP period. PGFM concentrations dropped to low basal level by day 10 PP and remained constantly low throughout the study period. P4, E2 and PGFM profiles were not different between the different parity groups. In conclusion, intrauterine infection is not common in goats with normal kidding. E. coli was the most common intrauterine bacterial isolate. E2 and P4 profiles were consistent with resumption of follicular growth but not ovulation. High PGFM concentrations coincided with the fast regression phase of uterine involution. Hormonal profile and bacterial contamination and clearance were similar to those reported in other related species and not related to parity.

Ultrasonic assessment of puerperal uterine involution in Balady goats

Twenty-six postpartum Balady goats (primiparous, n=13; pluriparous, n=13) were used in this study. One animal of each group was slaughtered on postpartum days 1, 2, 4, 7, 10, 13, 19 and 25; in addition, three control nulliparous goats were slaughtered, and the genital tracts collected. Progress of uterine involution was monitored by repeated ultrasonographic measurements in live animals (primiparous n=6; pluriparous n=6) and measurement of the outer circumference of the uterine horns of slaughtered animals (primiparous n=8; pluriparous n=8). A consistent and progressive decrease in ultrasonographic and outer circumference measurements was found, although faster during the first 7 days postpartum than between days 7 and 19 postpartum. Uterine involution, assessed by the upper limit of the measurements in the nulliparous goats, followed a quadratic pattern and was completed by day 19 postpartum. Ultrasonographically, two elliptical-circular echogenic areas separated by an anechoic line of the stratum vascularis were depicted. Regressing caruncles and fluid in uterine lumen were recognized during the first week postpartum. Further analysis revealed a highly positive correlation between the outer circumference and ultrasonographic measurements. In conclusion, uterine involution in Balady goats was completed by day 19 postpartum and was unrelated to parity. The close association between ultrasound findings and macroscopic involution indicated that ultrasonography can dependably be used to monitor uterine involution under field conditions and can be a suitable alternative to animal slaughter for the study of uterine involution.

Technical and Economic Evaluation of Different Methods of Newcastle Disease Vaccine Administration

Two types of locally produced live vaccines (HB1 and La Sota--lentogenic strains) and inactivated oil adjuvant (IOAV) vaccine were used to compare the efficiency of three vaccination techniques, namely drinking water, ocular and spray on broiler chicks. The ocular route of vaccination on 1-day-old chicks followed by a booster dose on the third week through the same route induced a significantly higher level of haemagglutination inhibition antibody titre (P < 0.0001). The highest mean antibody titre was log(2) 6.6 and 93.3% of the chicks were protected from the challenge. The spray technique induced a lower antibody titre (peak of log(2) 5.9) and only 53% of the chicks in this treatment survived against the challenge. The results of this study show that the ocular route is superior to the drinking water route, which is superior to the spray technique. The economic analysis result showed that the ocular HB1 and La Sota vaccine administration method to 1- and 21-day-old chicks gave the highest revenue followed by the drinking water method. In terms of total cost, the injection method required the highest cost (0.21 birr/chick) followed by the ocular method (0.18 birr/chick). The marginal cost of vaccine administration is too small compared with marginal revenues from relative effectiveness of the methods. The internal rate of return for the ocular method was very high. The results of sensitive analysis on revenues from different vaccination methods indicate that a 25% reduction in broiler price reduces the marginal revenue from the ocular method by 12 487 birr but this still does not prove that the ocular method is economically viable for small- and medium-scale poultry farms.

Transfection of mouse eggs and embryos using DNA combined to cationic liposomes

We have used plasmid DNA in combination with cationic liposomes to transfect mouse eggs and embryos. The plasmid was rhodamine labeled, which allowed a direct visualization of the DNA uptake by the cells. Immature eggs, collected from the ovaries, were easily transfected, but once the egg was ovulated the zona pellucida (ZP) acted as a barrier and prevented transfection. Permeabilization or removal of the ZP was therefore a requirement to allow transfection. Transfected eggs were capable of being fertilized in vitro giving raise to embryos that expressed the recombinant protein. Morulae and blastocysts were also transfected when the ZP was permeabilized, but the efficiency of transfection decreased and in some cases not all the blastomeres incorporated the plasmid. Pronuclear embryos were cultured and showed expression of the transgene from the 2-cell stage. This indicates that liposome-transfection of oocytes or pronuclear embryos could be a simple and suitable method to introduce foreign genes in embryos and perhaps could be also useful to generate transgenic animals.