Abstract
A 25-year retrospective study investigated the incidence of contagious bovine pleuropneumonia (CBPP) in the northern communal regions of Namibia. Throughout the study period, the proportion of bovine animals that clinically recovered following treatment of suspected CBPP infection were greater than those that died from suspected CBPP infection (71.6% and 28.4%, respectively, N=4743; z=42.16, p<.001). The proportion of unconfirmed CBPP diagnoses was greater than that of confirmed cases (65.4% and 34.6%, respectively, z=30.04, p<.001). More animals died from confirmed CBPP infection in the North Central Regions (NCR) and Zambezi region (5.4% and 4.1%, respectively) than in Kavango and Kunene regions (2.1% and 0.5%, respectively; p<.05). Kavango region had the greatest proportion of animals (7.9%; p<.05) that clinically recovered following treatment of confirmed CBPP infection whilst more animals in NCR and Kunene region recovered following treatment of unconfirmed CBPP (41.6% and 1.0%, respectively; p<.05). The NCR and Kunene region had greater proportions of animals that died from unconfirmed CBPP infections (9.1% and 1.0%, respectively; p<.05). More animals than expected died of confirmed CBPP in 1990, 1995, 2000, 2002, 2003 and 2004 (p<.05) whereas more animals than expected died of suspected CBPP in 1990, 1991, 1993 and 2004 (p<.05). Overall, the majority of animals died of confirmed CBPP in April, August and December (2.8%, 1.9% and 0.7%, respectively, p<.05). The highest CBPP vaccination coverage was achieved in 2003, 2004, 2009, 2011 and 2012 (96.6%, 82.6%, 84.8%, 90.1% and 90.1%; respectively). The greatest CBPP incidence rates (per 100 000) occurred in 1995, 1996, 1997, 1998 and 2003 (54.1, 43.4, 75.3, 106.2 and 25.5, respectively). The highest CBPP-related mortalities (per 100 000) occurred in 1995, 1996, 1997, 1998 and 2004 (25.3, 11.1, 17.2, 11.9 and 15.6, respectively). Although the incidence of CBPP cases has decreased, control of the disease remains a challenge because of cross-border livestock movements between northern Namibia and southern Angola.

Key words: CBPP; Namibia; vaccination; incidence; mortality; annual