Contagious Bovine Pleuropneumonia Experimental Transmission in Zebu Cattle by Contact: Study of Clinical and Pathological Aspects of the Disease

Abstract

The experimental transmission of contagious bovine pleuropneumonia (CBPP) was carried out by putting into close contact 14 naive zebu cattle with 12 naturally infected N’Dama cattle taken from a CBPP field outbreak. The healthy zebus originated from various CBPP-free herds and had not been vaccinated against CBPP in the past several years. Four control animals who had never been in contact with Mycoplasma mycoides subsp. mycoides Small Colony (MmmSC) were housed separately. The experiment lasted 12 months. All animals were monitored for clinical signs and regularly sampled for serological and bacteriological analyses. Postmortem analyses were performed on all animals to assess the presence of CBPP gross lesions and to take samples for MmmSC isolation. The results showed the efficacy of CBPP transmission by contact. Animals were assigned to three groups according to clinical, postmortem, and laboratory findings, as follows: acute form including two deaths (5/13), subacute to chronic form (6/13), and resistant form (2/13). Animals with obvious clinical signs of the disease showed various lung lesions at necropsy (hepatization, sequestra, pleural fluid, lung adhesions, fibrotic scars, etc.) as well as seroconversion. MmmSC was isolated from hepatized lungs and sequestral contents. In contrast, the two animals with a resistant form never presented any clinical nor any serological signs. The control animals remained clinically healthy throughout the experiment; at necropsy, no CBPP-characteristic lesion was noted and laboratory analyses remained negative. This study confirmed previous observations that showed that CBPP infection can be successfully transmitted to cattle by contact, and it could provide an experimental basis for future research such as the characterization of the host immune and pathological responses at various stages of the disease