Impact of livestock diseases in Africa

More than a billion people around the world living under poverty, depend on livestock for their livelihoods. In Africa; this number is estimated at about 300 million people. Animals provide these people with food protein, traction power and manure for crop production. In arid and semi-arid areas of Africa, livestock play a crucial role in food provision. In these regions livestock act as a "bank" for provision of cash derived from sales of their products or of the animals themselves in times of crisis, to raise the funds needed to purchase food and meet other family needs.

When food prices soared during 2008, an unspecified but large number of livestock in these regions were sold to meet food needs and there is now a need to restock which can only be achieved when the impact of animal diseases is reduced as they impact greatly on these social groups.

Few studies are available in Africa to validate the impact of livestock diseases, but estimates at the worldwide level, indicate that average losses due to animal diseases are more than 20%. While there is hardly accurate data on losses attributed to livestock diseases in sub-Saharan Africa, it is believed that this percentage could be higher. Overall economic losses have previously been estimated at US$ 2 billion. Losses due to morbidity as reflected by reduction in growth, lactation, work output and reproduction are probably of the same magnitude.

The impact of animal diseases, either due to overt disease or disease risk, are all likely to be proportionally greater for the poor because they are exposed to more animal disease risk and have less capacity to cope with that risk than those who are better-off. This combination (exposure to risk and lack of capacity) reduces yet further their chances of escaping poverty.

Reducing the incidence of these diseases is therefore one of the priorities to be considered in order to feed the world and reduce poverty. This requires a clear political will, which the World Organization for Animal Health (OIE) and its partners such as African Union (AU) Interafrican Bureau for Animal Resources (AU-IBAR), the Food and Agriculture Organization (FAO) of the United Nations and the World Health Organization (WHO) of the United Nations must encourage at the global level.

Indeed, access to adequate supply of good quality food is not just an agricultural problem but also a public health issue which must be tackled from a global point of view. Below are some facts that support this view:

• Since 1992, the undernourished population in developing countries has declined by just 3 million from 823 to 820 million.
• The African Union predicts a USD$2billion annual gap in animal protein requirements by 2030.
• 70% of people living on an income of less than a USD$1 a day are dependent upon livestock for their income and food security.
• The rural poor constitute 66% of the population (504m) of the poorest 38 countries in Africa.
• Livestock keepers are not only found among the rural poor, but also among the poor urban dwellers who keep them to supplement their income and protein needs.
• 25% of their livestock die yearly because of preventable animal diseases. In some cases this statistic masks the destructive capacity of diseases such as Newcastle Disease, which affects poultry that are most affordable by the poorest, often leading to 100% flock mortality.

For these reasons human and animal health are inextricably linked and should be addressed together for sustainable poverty reduction.

Unfortunately, output from livestock has decreased by 25% partly because of diseases whose prevention is constrained by limited availability of vaccines and poor vaccine distribution systems. This is particularly critical for neglected diseases such as PPR in sheep and goats, CCPP in goats, CBPP in cattle and ND in poultry, which by coincidence have the highest impact among the poor livestock keepers.

Although vaccines for these diseases exist, and are produced by African laboratories, the technology used to produce some of the vaccines is not entirely in conformity with the current global trend. This is further compounded by acutely limited resources and investments that are required to increase their production capacity, distribution and delivery. Quick investments and financial resources are therefore required in order to improve access to quality vaccines. This approach is supported by the World Development Report (2000/2001) which emphasizes on "a change of focus from development that supports the national economy to a direct focus on the ailments of the poor."

Peste des petits ruminants (PPR)

PPR has been described as the most destructive viral disease in small ruminants with young animals (3 – 18 months) being most susceptible. It is the main constraint to small ruminant production especially amongst pastoral communities with production losses ranging from 50 – 90 % and mortality rates of 10 – 90%. When associated with other diseases such as Capripox, mortality can reach 100%.

In early 2000s, an animal disease consultancy of the FAO singled out PPR as one of the important animal diseases to be taken into consideration in poverty alleviation policies. The PPR vaccine has the ability to prevent infection, the disease and further shedding and it confers life-long immunity.

Geographical spread

PPR is widespread in Western and Central Africa and appears to be spreading in Eastern Africa as well. The disease is also present in Middle East, the sub-Indian Continent and several Asian countries. Although good data is scarce in Africa, recent vaccination campaigns in Kenya (more than 10 million animals vaccinated), Northern Uganda and Somalia indicate that the situation is quite alarming. The disease was reported in Tanzania in December 2008 and is currently ravaging sheep and goats in Ethiopia. In recent years PPR has been spreading northward and has been diagnosed in Morocco with a high risk of spreading into southern Europe.

Impact

The socio-economic importance of PPR is a result of heavy losses at production level and market effects along the value chain. It is estimated that 10% of the total impact of the disease is on trade and public expenditure and 90% on herd productivity.

• In Nigeria, an outbreak that occurred in 1979 killed 10-20% of the national small ruminant flock that was estimated at US$ 75 million.
• A cost benefit analysis conducted in Niger in 1993 to assess the benefit of vaccination against PPR concluded that an investment of US$ 2 million on vaccination would generate US$ 24 million in return for a five year vaccination program.
• In Ethiopia FAO estimates that losses associated with PPR reached an average of US$ 375 per flock per year, with an average of 143 small ruminants per flock (an average loss of more than US$ 2 per animal).
• In the 2008 outbreak in Kenya, the cost of vaccines used is estimated at € 4.8 million out of a total vaccination campaign cost of €12 million.

The important direct economic losses caused by PPR are often further aggravated by the sanitary measures imposed by authorities in controlling animal movement and trade restriction on their by-products. Because of the high negative economic impact in countries affected by PPR, this disease is one of the priorities of the FAO Emergency Preventive System (EMPRES) programme.

Vaccine production

A number of African laboratories in Botswana, Cameroon, Niger, Mali, Senegal, Nigeria, Morocco, Chad, Kenya and Ethiopia, and some in the Middle East have obtained the seed stock for the vaccine from the OIE Reference Laboratory at CIRAD-EMVT (Elevage et Médecine Vétérinaire Tropicale) and are producing the vaccine.

Contagious caprine pleuropneumonia (CCPP)

CCPP is a disease of goats caused by Mycoplasma capricolum subspecies capripneumoniae (Mccp). It is characterized by high morbidity (80-100%) and mortality (60-100%) rates. The disease is of major economic importance in Africa and has been described as the most serious infectious disease of goats in East Africa. A specific risk for CCPP is that it has been spreading beyond its traditional distribution area due to lack of diagnostic capacity in most countries; poor transportation access to the affected areas and inadequate availability of control tools.

Geographical spread

The distribution of the disease in the African continent is not well known as veterinary services are not able to confirm suspicious cases. This is due to difficulties in isolating the causative agent or inability of the diagnostic laboratories to use Polymerase Chain Reaction (PCR) based techniques. So far the CCPP situation seems well characterised in Eastern and Horn of African countries (Eritrea, Ethiopia, Kenya, Uganda, Tanzania, Sudan and Somalia ). Little is known in other African countries where the disease seems to evolve in an epizootic manner with outbreaks occurring very irregularly (Chad 1987, 1995, Cameroon 1997, Tunisia 1982 and Nigeria 2008 ) threatening the rest of the continent and beyond. The most recent information in 2009 on CCPP indicates that the disease is now Mauritius and Tajikistan, an illustration that this disease may have a much wider distribution and importance than actually declared. While the real distribution of CCPP is unknown in many African countries it is very probable that the disease has a much wider distribution but confirmation of outbreaks are not done because of clinical confusion with other syndromes such as Pasteurellosis; the wide use of antibiotic treatments which modify the clinical course; the difficulties to grow the causative organisms and the absence of adequate samples submitted to national reference laboratories for diagnosis.

Impact

Direct losses due to CCPP are associated with the high morbidity and mortality rates (100% and > 60% respectively) of the disease which leads to reduced milk and meat yield and loss of income thus worsening food and nutritional security. Indirect losses are associated with the extra cost of treatment, increased risk associated with antibiotic residues and reproductive wastage.
In most goat production systems in Africa, goats are often the responsibility of women and CCPP therefore negatively impacts on the ability of women to provide for their children and family needs. Goats have the advantage over cattle of recovering faster following droughts.

Current strategies for control using vaccination

CCPP is an OIE listed notifiable disease and vaccination associated with antibiotic treatment is the most important strategy to control the disease. While an effective vaccine for CCPP exists, control strategies are impaired by lack of diagnostic capacity in most countries and limited vaccine production capacity linked to technical limitations in the production process. Increasing diagnostic and vaccine production capacities will therefore be a prerequisite for informed intervention strategies for control of the disease to reduce its impact. There is only one vaccine available for CCPP. This is a killed vaccine currently produced by the National Veterinary Institute (NVI) in Ethiopia and the Kenya Veterinary Vaccines Production Institute (KEVEVAPI). Trials of the vaccine have shown it to be highly effective, providing protection for over one year. However, there is a limited production capacity.

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.

Geographical spread

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.

Impact

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.

Newcastle disease (ND)

FAO estimates a population of approximately 1.38 billion chickens in Africa of which more than 70% are in villages playing a vital role in the livelihood strategies of many poor rural households. With their economic asset value estimated at US$ 5.75 billion, village chickens provide meat, eggs, food for special festivals and petty cash for school fees and medial expenses. However, one major constraint to production of village chickens in many developing countries is ND whose outbreaks are unpredictable and discourage poultry keepers from paying proper attention to the husbandry and welfare of their chickens.

The incubation period of ND varies from 4 to 5 days (range 2 to 15 days) depending on the strain of the infecting virus. The ND virus may persist in undispersed chicken faeces for more than six months but under village conditions the virus is unlikely to survive outside a host for more than one month. In commercial poultry production, and also under experimental conditions with compost from chicken faeces, the virus has been found to survive for 16-21 days. The clinical signs of ND vary considerably depending on the virulence and tropism of the virus involved; the species of bird, the age of host, the immune status of the host and environmental conditions.

Geographical spread

ND is present everywhere on the African continent with the exception of Egypt, Morocco and Tunisia which have not reported the disease occurrence in the past four years. Libya reported suspected disease outbreak in 2005.

Impact

In countries where there are circulating strains of ND virus, chickens may experience mortalities of up to 100% in unprotected flocks. Village poultry keepers tend to accept losses due to ND as near inevitable, which acts as a powerful disincentive to improve other aspects of the husbandry of their birds. Observations from Mozambique indicate that controlling ND had the potential to increase incomes derived from poultry by 42%. Adoption of additional simple and low-cost husbandry measures increased this to 82% and after one year of successful campaign, the average chicken flock had increased from 5 to 13 birds thus increasing off-take numbers for increased consumption of chicken products or sales to increase household purchasing power, and because women were involved throughout, increased decision-making power for women.

A preliminary estimate generated by a model developed by ILRI suggests that in Africa, more than 589 million chickens are at risk of ND. The model predicts that if an ND vaccine was used in 10% of the birds at risk, this would potentially prevent more than 6 million chicken deaths.

Current strategies for control using vaccination

Vaccination is the only effective way of controlling ND. Thermostable ND vaccines, together with inactivated ND vaccines have been used successfully in the backyard sector in many African countries. An advantage of the inactivated ND vaccines, (though more expensive), is that they can be found commercially, and incorporated into programs aimed at supporting backyard poultry owners. Another advantage of is that the number of applications per year are fewer. Many vaccines (both live and inactivated) produced by multinational companies are freeze-dried into multi-dose vials, often containing 1,000 or 2,500 doses and, because of high number of doses they are mainly of benefit to commercial poultry producers whose chickens are kept in large, single-age or confined flocks. The live vaccines must be kept under "cold chain" from manufacture until administration to the chickens.

In contrast, village chickens are raised in small, multi-age, free-range flocks and large multi-dose vials of vaccine are therefore inappropriate. Further, it is difficult to maintain "cold chain" under village conditions. In many rural areas in Africa, these vaccines are there not even available. In this regard, the future long-term control of ND in village chickens in Africa lies in supporting the production and utilization of thermostable I-2 vaccines.