The status of CBPP in west and central Africa and strategies for sustainable control

B. M. Seck^[38], M. Kané^[39], W. Amanfu^[40]

Introduction

CBPP is still a big problem for most cattle producing countries in sub-Saharan Africa, because of its insidious nature and the difficulties associated with controlling the disease. In the late 1960s, expectations for the control of the disease and eventual eradication were high due to the development and the use of freeze-dried CBPP attenuated vaccines (T1 44, KH₃J) instead of the previous broth culture vaccines. Later on, the various rinderpest vaccination campaigns gave the opportunity to increase CBPP vaccination rates in many countries using combined (bisec-rinderpest virus vaccine plus CBPP vaccine) vaccines or administering the two vaccines separately. At the end of Pan African Rinderpest Campaign (PARC) programme, outbreaks of CBPP declined dramatically in some countries (i.e. in Senegal, Niger, Chad and Cameroon). Elsewhere, although the disease prevalence declined, more than 20 years ago, it still remains endemic or sporadic in those countries.

In response to this CBPP persistence in Western and Central Africa and due to new developments in disease outbreaks in Eastern and Southern Africa (in mid and the late 1990’s), several technical meetings have been held on various issues on CBPP that detailed the major constraints impeding the control of the disease on the continent.

This presentation is intended to provide updated information on CBPP status in West and Central Africa and to propose a strategic plan for its sustainable control. It is based, especially for West Africa, on the activities and the conclusions of the last coordination meeting of the FAO TCP - “Coordinated programme to strengthen capacity for the epidemiosurveillance and control of CBPP”, (TCP/RAF/0172) - held in October, 2002 in Ouagadougou, Burkina Faso in conjunction with PACE, and which focused on the development of a proposal for a “Coordinated and Progressive Control of CBPP within the western Africa sub-region”. For Central Africa, data were obtained from various PACE programme progress reports and from OIE Zoosanitary status report for year 2002.

Main livestock production systems in West and Central Africa

The main livestock management system, within the cattle producing countries of the two sub-regions, is the extensive pastoral system characterized by livestock transhumance and nomadic livestock system within Sahelian zones. In Mali, the central delta of River Niger is a convergence zone for seasonal grazing for a huge number of transhumant and nomadic cattle herds from Mauritania, Burkina Faso and Niger. In Chad, the Lake Chad zone plays a similar role for transhumant herds from Cameroon, Central Africa Republic Niger and Nigeria. These seasonal traditional movement of transhumant and nomadic cattle herds are accompanied by an important flux of cattle trade movements (more than 500,000 heads yearly) directed southward throughout the year from Sahelian zones of Burkina Faso, Mali, Mauritania, Niger, Cameroon and Chad to coastal countries of Benin, Côte d’Ivoire, Ghana, Liberia, Nigeria, Senegal and Togo.

Within West and Central Africa, cattle movement monitoring by veterinary services is known to be sub-optimal due to lack of resources (human, financial, material). The livestock industry infrastructures (markets, abattoirs, slaughter slabs) are usually monitored by veterinary authorities, but CBPP suspected cases or lesions noticed at their level are not often integrated into the data of the national CBPP surveillance system. In addition, only two countries have made efforts to achieve local cattle identification system (by tattoo in Guinea, by numbered metal ear-tag in Côte d’Ivoire) in order to improve cattle movement monitoring and animal disease trace-back.

Current CBPP status and control in West and Central Africa

With regards to CBPP reported prevalence, West and Central Africa are not under the same burden of disease. While the disease is endemic within most of West African countries, only a few countries in Central Africa currently report it. In terms of cattle population, it must be realized that: (1) There are more cattle producing countries in West than Central Africa; (2) In Central Africa, the Sahelian pastoral zones of Cameroon and Chad have 74% of cattle stocks within the sub-region; (3) West Africa cattle population is 46.5 million cattle heads against 5.9 millions for Central Africa.

CBPP Prevalence and Distribution

In Central Africa, CBPP has never been reported by Congo, Equatorial Guinea and Gabon. In this sub-region, the disease status is far from being clear due to lack or imprecision of available data (Table 1).

CBPP is endemic or sporadic all over West Africa except in the Gambia, Guinea Bissau and Senegal (Table 2). The disease has never been reported by Guinea Bissau, while the last cases in Gambia and in Senegal were reported in 1971 and 1992 respectively. The disease is well established in Burkina Faso, Côte d'Ivoire, Ghana, Mauritania and Mali but is sporadic in Niger and Guinea - Conakry.

Within both West and Central Africa, CBPP outbreak reporting is not usually followed by field investigations to collect more epidemiological, economic or ancillary data. Therefore, in many circumstances, when morbidity and mortality figures are available (Table 3) it is not possible to compute the corresponding morbidity and mortality rates.

Table 1. CBPP Outbreaks in Central Africa (Unit)

nd - no available data. Sources: Country report;
+? - disease suspected except for
* from OIE Countries' zoosanitary status 2002

Table 1. CBPP outbreaks in West Africa (Unit)

Source - Country National Veterinary services
nd - no available data

Table 3. Morbidity and morality figures within CBPP outbreaks (in cattle head)

CBPP Distribution

West Africa

In the Sahelian countries of this - region, at least three CBPP endemic areas can be distinguished at the bordering provinces between; (1) Burkina Faso, Mali and northern Côte d'Ivoire; (2) Mali and Mauritania; and, (3) Niger and Mali. They include a lot of common dry-season pastures used by transhumant herds from these different countries. Nevertheless, the recent trend of the disease is characterised by spread towards central Côte d'Ivoire, southern Mali and southern Burkina Faso due to the increase of southward flux of transhumance movement, the gradual settlement of pastoralists in long-lasting pasture zones and the increase of purchase and use of oxen for cotton production.

The current CBPP distribution within West African coastal countries affected by the disease is as follows:

• In Côte d’Ivoire, CBPP occurs every year, mainly in its Central and Northern provinces (sharing borders with Burkina Faso and Mali) inside a “V” shaped area delineated by the provinces of Odienné in the north-west, Bongouanou in the south and Abengourou in the East;

• In Ghana, the disease is endemic and reported in nearly all the ten regions of the country and in many circumstances, the source of the outbreaks has been traced to trade cattle or to transhumant cattle from northern neighbouring countries;

• In Guinea, the eastern part of the country, sharing borders with Mali and Côte d'Ivoire is the traditional CBPP endemic zone while its western part, protected by a sanitary cordon, is free from the disease since the late 1980s';

• In Benin, Nigeria and Togo, the disease prevalences as well as its distributions are unclear or not updated. Although Togo reported to OIE 15 CBPP outbreaks for year 2002, there is no indication about their distribution. Nigeria, with the biggest cattle population of the sub-region (19.8 million out of a total of 46.5 in year 2000), reported only one CBPP outbreak in year 2002 in spite of its transhumant cattle which move from northern Nigeria to Niger, Cameroon and Lake Chad.

In Central Africa, CBPP was not reported from Congo, Gabon and Equatorial Guinea. In year 2002, the two CBPP outbreaks reported from northern Cameroon were both from transhumant cattle herds coming back from Chad. Elsewhere, the absence of data or the imprecision on reported outbreak locations (i.e. the four outbreaks of Chad in 2002) made drawing of geographic distribution of disease difficult. In Democratic Republic of Congo, CBPP started at the border with Uganda in 1981 and within a 10-year period affected 10% of the cattle population of Ituri Province. Since then, the civil unrest in the country made disease surveillance and reporting impossible. The Lake Chad zone, which is a gathering area for a number of transhumant herds from Niger, Nigeria, Cameroon and Central African Republic, used to be considered as the zone where CBPP transmission occurs and from where it is disseminated southwards.

CBPP Surveillance and Reporting

In spite of the setting up of national priority animal disease epidemiosurveillance networks (officially formalised into most of PACE participating countries during the last 2 years), and support from other animal health projects, weaknesses are still noticed in most of the CBPP surveillance systems put in place and at various levels (on field, along cattle roads, in cattle markets, abattoirs and slaughter slabs). In particular, within many countries, the CBPP abattoir/slaughter slab surveillance is not effective or not linked to the CBPP epidemiological surveillance network. Therefore, usually there is no resulting trace-back of field observations of CBPP-like lesions to their herd of origin. The clinical surveillance of herds within affected areas is not regularly undertaken. Cattle movement monitoring is in general sub-optimal as it is not systematic and no permits are issued for inter-provincial movement between areas of different CBPP status (i.e. Mali, Burkina Faso, Côte d'Ivoire). Between ECOWAS countries, transboundary cattle should be (theoretically) provided with International Transhumance Certificate and vaccinated against CBPP. Unfortunately, the border quarantine stations are not often used by transboundary herds and are not provided with veterinary staff.

Two exceptions in the weaknesses of CBPP surveillance and reporting are found in Guinea and Senegal. In Guinea, the CBPP surveillance system receives significant back up from a livestock breeders group, “Sanitary defence group”, so that stockbreeders are the real first line of early warning and early reaction systems. Senegal has a solid, well structured and functional CBPP surveillance system that is provided with regular and updated information on CBPP. Within both countries, private veterinarians granted sanitary mandates, are formally involved in CBPP field, abattoir surveillance and disease reporting.

Laboratory Confirmation of CBPP Diagnosis

In most of West and Central Africa, only the central veterinary laboratories are in a position to perform CBPP laboratory confirmatory diagnosis. Laboratory testing methods include complement fixation test, enzyme linked immunosorbent assay (ELISA) test, agar gel immunodiffusion (AGID) test and/or bacteriological culture and isolation, identification and characterization. The provincial laboratories are often understaffed, ill equipped and undersupplied with laboratory reagents and media so that their role is limited to serum collection.

Within some countries, suspected field cases or CBPP-like lesions at the abattoirs, are not systematically subjected to confirmatory laboratory diagnosis although everywhere, CBPP is a notifiable disease. The annual figure of field and abattoir samples received for laboratory confirmatory diagnosis ranges between 30 samples (in Mali and Burkina Faso) to one thousand samples (in Côte d’Ivoire and Ghana). In Côte d'Ivoire, Ghana and Guinea, CBPP surveillance and control programmes benefit from excellent laboratory support.

Current CBPP Control Strategies

In Gambia, Guinea Bissau, Congo and Gabon the current strategy to prevent CBPP re-entry is based on increased surveillance of the disease along with increased public awareness. CBPP vaccination has never been done in Guinea Bissau. It was stopped in Gambia and Gabon in 1971 and 1997, respectively. Elsewhere within the two sub-regions, annual vaccination remains the main CBPP control strategy. Although in all countries the veterinary zoosanitary regulations consider CBPP as a notifiable disease and foresee mandatory zoosanitary measures, these are often limited to affected herds for a short period of time and ring vaccination around the disease foci is often carried out. The CBPP control strategy in Ghana is based on annual vaccination in endemic areas complemented by in case of outbreaks, test and slaughter of sick and infected animals and vaccination of animals at risk.

Guinea's PARC programme during the late 1990s focused on CBPP control that led to one of the most comprehensive CBPP control strategies in West Africa due to a combination of factors such as:

• Annual mass vaccination campaign in endemic zones;

• Slaughtering of all clinically affected and exposed cattle within CBPP outbreaks or village based on the extent of the epidemic;

• Country zoning with infected, surveillance and free zone; a sanitary barrier divides the country into two parts with strict ban of cattle movement from the CBPP-infected area into CBPP-free area, except to the abattoir by motorised transportation and under veterinary escort;

• Ear notch branding of all cattle sent to infected area markets;

• Individual identification of cattle by tattoo (started since 1992);

• Active involvement of around 12,000 veterinary auxiliaries and 500 livestock producers "Defence groups" and private veterinarians in cattle movement monitoring and CBPP surveillance and reporting;

• Presence of a central office dedicated to CBPP data collection, analysis and information feed-back to all interested parties;

• Regular technical refresher courses for the veterinary personnel and regular public awareness campaigns.

In 2002, the Federal Government of Nigeria funded a five-year CBPP control programme with a containment phase (foreseeing compulsory annual mass vaccination, transhumance certificate, livestock movement control etc.) to be followed by an eradication phase (with compulsory slaughter of sick or exposed cattle and compensation, active surveillance etc.).

For countries in West Africa, CBPP vaccination campaigns are targeted one-round annual vaccination with T1 44 or with T1 SR vaccine (Table 4). The cattle stock mobility, the cost of vaccine dose and the T₁ vaccine side-effects are cited as reasons for the low vaccination rate and the difficulty to do more than one-round vaccination yearly (Table 4).

Table 4. CBPP Vaccination in West Africa

Sources: FAO statistics (2002) for Cattle stocks; National Veterinary Services for immunisation figures

In Central Africa, CBPP vaccination is mandatory in Chad and Cameroon but not in Central Africa Republic. The vaccination has been officially stopped in Gabon in 1997. In Democratic Republic of Congo it was also stopped since 1994 because of lack of resources and civil unrest.

In West Africa and Chad, CBPP vaccination fees are partially or totally supported by livestock owners or traders through a cost recovery scheme. Table 5 indicates the respective cost of one vaccine dose and one cattle vaccination fees (direct ones). The collected revenue is used for cold chain maintenance, vaccination material and purchasing of vaccination certificate cards. The CBPP vaccine (T1 44 or T1 SR) used is supplied by one of the following laboratories: Garoua (Cameroon), Bamako (Mali) and Dakar (Senegal).

Table 5. CBPP vaccine and vaccination cost (Unit)

Currency exchange rate: 1Euro = 656FCFA 1UM = 2.5FCFA; 1FG = 0.65FCFA; 1US$ = 650FCFA = 8,347Cedis

Officially, within the two sub-regions, antibiotics are not allowed to be used for treating CBPP affected animals.

Throughout the two sub-regions, stockbreeders and cattle traders associations are involved in CBPP surveillance and control. Private veterinarians are associated with vaccination campaigns against priority disease through “sanitary mandate”, but except in few countries, they are not yet closely associated with field and abattoir surveillance and disease reporting for CBPP.

Conclusions on CBPP Status in West and Central

Although CBPP status seems relatively clearer in West Africa (except within some coastal countries: Benin, Nigeria and Togo) than in Central Africa, the imprecision of the data on animals at risk, as well as the epidemiologic parameters and economic impact of the disease, demand that studies are carried out to clarify the situation within most of the countries before expecting sustainable CBPP control and minimizing the risk of transboundary spread of the disease.

Strategies for Sustainable CBPP Control

The overall proposed CBPP control strategy, for West and Central Africa, is based on:

• Preparatory activities aimed at collecting epidemiologic and economic data necessary to justify and properly plan an effective and sustainable CBPP control strategy.

• Normative activities, at both national and sub-regional levels, dedicated to reducing as much as possible, the disease burden or risk at national level and to minimize its transboundary spread through a coordinated CBPP risk assessment and management.

Phase1. Defining the Epidemiological Status of CBPP within each Sub-region through:

• enhanced CBPP field, market and abattoir surveillance, reporting and trace-back systems at national and sub-regional levels for improved understanding of CBPP epidemiology and economic impacts;

• improved priority animal disease control infrastructures - including improved veterinary diagnostic laboratories support for CBPP confirmatory diagnosis- to allow development of justified and rationale and economic disease control plans;

• effective involvement of rural communities, cattle traders and other stakeholders into all aspects of CBPP surveillance, reporting and control through training, communication and public awareness campaigns;

• improved cattle movements monitoring and trace-back systems at national and subregional level - updating transhumance and trade cattle routes; use of official accompanying documents of moving cattle groups and re-enforcement of harmonised

International Herd Health Certification usage.

Phase 2. Reduce CBPP Risks at National level by:

· prevention of CBPP re-entry into:

• country not currently reporting CBPP (i.e. Gambia, Guinea Bissau, Senegal, Gabon etc.) by combined intensive active CBPP surveillance, animal movement monitoring and control, establishment of formal buffer and surveillance zones to protect disease high risk areas;

• long-lasting CBPP-free zones protected by sanitary cordon (i.e. western part of Guinea-Conakry) by strengthening or establishing CBPP sanitary cordon, imposing cattle movement control towards CBPP-free zones combined with intensive disease surveillance and re-enforcement of other sanitary prophylactic measures into established surveillance and buffer zones.

In such zones, an appropriate level of CBPP control activities, by sanitary prophylactic measures mainly, would be undertaken where needed to contain any new CBPP foci as fast as possible and minimise the risk of disease spread.

· reduction of CBPP incidence within endemic countries and limitation of its spread by intensive and regular vaccination of exposed cattle within endemic and high risk areas followed with intensive disease surveillance and cattle movement control.

Within affected large Sahelian pastoral areas, the testing, vaccinating and control of such diseased herds is currently out of the capacities of most veterinary services. Consequently, control measures would be a compromise between the ideal methods and those that are practically possible. Therefore, in these areas, once the disease incidence has been reduced to a low level, through vaccination, intensive disease surveillance, systematic clinical and pathological surveillance, serosurveillance and other ancillary actions - other control measures could be justified and implemented.

· development of detailed national and sub-regional control plans.

While it is not appropriate to develop mid and long-term national CBPP control or eradication plans until the epidemiology of the disease is understood and reliable data available, as well as the priorities for control measures correctly identified, the continuing presence of the disease demands that control measures be initiated. Later on, these control measures would be evaluated and the different CBPP eco- epidemiological zones re-defined before achieving the mid and long-term control plans for the disease.

Phase 3. Minimise CBPP Transboundary Spread at Sub-regional level through:

• Improved CBPP risk assessment and management - including improved CBPP emergency response capabilities, harmonised disease surveillance, reporting and control strategies;

• Institutionalised CBPP active surveillance and control programmes, involving all stakeholders, in order to establish CBPP free eco-epidemiological zones with recognised international sanitary barriers;

• Established sub-regional mechanisms allowing transparency in CBPP risks assessment and surveillance systems evaluation;

• Harmonised appropriate legislative/regulatory support for CBPP surveillance and control.

This phase should lead to the definition of regional sanitary barriers or buffer zones based on CBPP status, ecological factors, cattle husbandry systems and movement patterns. For instance it could be established, between Senegal and its neighbouring countries, buffer zones of 50 km at least deep at borders and inside Mauritania, Mali and

Guinea with their corresponding surveillance zones inside Senegal.

Phase 4. Maintain Optimal Conditions for CBPP-free Status within each Sub-region through:

• improved and continuing sub-regional coordinated efforts and shared resources for CBPP active surveillance and reporting, information dissemination and cattle movement monitoring that could put some countries in the sub-region on the OIE pathway for Declaration of freedom from CBPP.

The above disease control strategy elements would need a high level of political commitment, as CBPP control requires courageous administrative decisions and rigorous application of disease control measures with discipline.

Conclusions

The proposed approach puts emphasis on a good preparatory phase (including improvement of extension services, rural community awareness activities, disease surveillance and control infrastructures, livestock movement monitoring system) followed by normative integrated activities requiring strong and sustained activities at both national and sub-regional level to alleviate the critical factors impeding the two sub-regions in the control of CBPP.

At present, countries in the region have the opportunity through the current animal disease control initiatives, to develop and maintain institutional capacity in priority animal disease surveillance and control. Nevertheless, for an appropriate and sustained CBPP control, there is the need for a strong political commitment, in developing strategies for controlling this disease through improved animal health care delivery system, coordinated efforts and resource sharing between countries in the region.