Contagious bovine pleuropneumonia (CBPP)
CBPP is a contagious disease of cattle and water buffalo caused by Mycoplasma mycoides subspecies mycoides (SC) - (MmmSC). The disease is regarded as one of the most serious trans-boundary animal diseases (TADs) affecting cattle production in Africa with an estimated economic losses of up to US$2billion per annum. Affected animals suffer from acute respiratory distress due to extensive lesions of pleurisy and pneumonia.
CBPP is widespread in Africa (See maps attached in the Annex). The disease is currently endemic in Angola and Northern Namibia, posing a direct threat to Southern Namibia which is currently free from disease. Although CBPP was eradicated in Europe using vaccination as well as controlling animal movement, sporadic re-occurrences have been reported in Portugal in 1983 after being absent from the country for about thirty years (1954-1983) and again in 1999. It therefore presents a potential threat to cattle in Europe. It is suspected that CBPP is also present in parts of Asia.
It is very difficult to evaluate the losses due to CBPP in many African countries where the disease is enzootic (endemic) because of the lack of proper reporting and economic evaluation. Available data on the impact of the disease is however, limited to incidence rather than the effects on livelihoods. While such data may not be readily available, empirical evidence indicates that the disease occurrence in many sub-Saharan (SSA) countries comprising about 433.9 million people of whom 10% entirely depend on livestock for livelihoods may be significant. In countries where some data has been gathered, losses due to CBPP have been estimated to be very high especially when the disease enters a CBPP free zone or country where cattle are susceptible. As an example, losses due to the reintroduction of CBPP in Tanzania may have caused more than $11 million dollars of direct loss in 1990. The reintroduction of CBPP in Botswana in 1995 led to the slaughter of 320,000 cattle at a cost of US$ 100 million, with further indirect losses estimated at over US$ 400 million.
Considering the diversity of apparently important cattle diseases in Africa and the need for Donors and Governments to prioritise investments, it is not surprising that CBPP has received little attention in most countries where it exists because of the enormous costs involved in its control.
Current strategies for control using vaccination
Effective control of CBPP control is best achieved when the real epidemiological situation and economical losses have been evaluated. Once this is done, control strategies may rely on various tools such as slaughter, movement control, vaccination and antibiotic treatments. Ideally the best control strategy should be a combination of these tools adapted to each local situation to reach the highest Cost/Benefit ratio. Eradication would be the most cost-effective alternative in a long-term perspective.
In practice, most African states organizing vaccination campaigns have no control on the distribution of antibiotics which are mainly controlled by the private sector. Movement control is difficult to enforce and slaughter has been used only in a very limited number of cases in Botswana and Zambia.
There are two vaccines available in Africa to control CBPP. These are T1/144 and T1sr, both which are attenuated vaccines. T1/44 which is the mostly used is produced by 10 laboratories on the continent. It offers better protection (1 year) compared to T1sr (6 months) but has more side-effects with post-vaccinal reactions likely to occur in animals vaccinated for the first time. The possibility for post-vaccinal reactions, including the likelihood of residual virulence in the vaccine strain to cause clinical CBPP, has therefore to be taken into account when organizing vaccination campaigns. Consequently, the search for new CBPP vaccines has become a major issue for African countries that are facing an increase in outbreaks. The rationale for this search is based on a better understanding of the Mycoplasma virulence mechanisms that could lead to a targeted attenuation of MmmSC strains. It is also based on a better understanding of the bovine immune response that may be driven to a pathogenic inflammatory response or conversely to a better balanced response leading to protection. Besides safety concerns, current vaccines are relatively easy and cheap to produce and offer 80 % protection when properly used.