Efficacy of Long-acting Oxytetracycline in Treating Contagious Bovine Pleuropneumonia and Potential for Carrier Status in Treated Cattle

Abstract

Contagious bovine pleuro-pneumonia (CBPP) is currently one of the most important diseases affecting cattle in Sub-Saharan Africa with great economic implications. It causes restrictions in trade, loss of productivity and loss of life in affected cattle. This respiratory disease has been controlled by strategies including restriction of animal movement, vaccination, test and slaughter. However, these strategies have had challenges in implementation in some places where it occurs due to: cultural practices encouraging aggregation of cattle; husbandry system that involves constant cattle movement; quality of vaccines delivered in vaccination campaigns; lack of funds for setting infrastructure to control movement; and funding compensation in test and slaughter exercises. This has resulted in surges of outbreaks of the disease in areas where it had been controlled. Due to these challenges, other control strategies have been advocated including the use of antibiotics. The objectives of this study were: (1) to assess the efficacy of one of the antibiotics used, long-acting Oxytetracycline (®Alamycine, Norbrook Laboratories Limited), in treating contagious bovine pleuropneumonia in cattle, and (2) to assess whether the treated animals become carriers. . Thirty cattle were bought from a CBPP-free area and brought to KALRO research station in Muguga. They were naturally-infected by exposing them to known-infected cattle; earlier infected with pathogenic Mycoplasma mycoides variety mycoides, small colonies (Mmm SC). After 42 days of contact, the thirty cattle were randomly divided into two groups of 15 each: Treatment group: treated with Oxytetracycline [a single dose 20% Oxytetracycline each (20 mg/Kg body weight), deep intramuscular] and Control group; given a placebo (saline). . The two groups were followed-up for another 31 days post treatment, during which progression of disease was assessed through clinical-sign observations, serology (complement fixation test) and mycoplasma isolation from naso-pharyngeal swabs. Cattle that showed severe illness were killed humanely by captive bolt stunning and exsanguination, post mortem examination xiv done, and samples of infected tissues collected. Then the carrier-status experiment followed, where each of the two groups was mixed with 5 CBPP-free (sentinel) cattle for one month; the sentinels were then tested to see if mycoplasma organisms could be isolated from their naso-pharynx. For the first experiment, significantly (p< 0.05) higher rectal temperatures were recorded in the control group particularly between day 7 and 14 post-treatment. The severity of CBPP as determined by clinical observations (general body condition, diarrhoea, appetite, respiratory distress, nasal discharge, cough, and rectal temperatures) was more in the control group; that is: the Oxytetracycline treatment group exhibited milder clinical signs (p <0.00) over the same period. No fever (39.5 0C) was recorded in the Oxytetracycline treatment group, while, in the control group, temperatures were found to be significantly (p <0.05) high between days 7 and 14 post treatment. When sentinel animals were mixed with the treated group (infected and Oxytetracycline treated cattle), none of them yielded mycoplasma organisms from naso-pharynx; thus, there was no evidence of development of carrier status after treatment. On the other hand, when sentinel animals were mixed with the control group (infected and not treated cattle), one of them yielded mycoplasma organisms from pleural fluid; caudal mediastinal, peribronchial lymph nodes. In conclusion this study has shown that Oxytetracycline treatment of cattle infected with CBPP has some efficacy by reducing the severity of the disease. It has also shown no evidence of carrier-status development after the treatment. However, further studies are recommended to support these findings.