The importance of livestock, in Nigeria, cannot be ignored. Small ruminants which include sheep and goat is a value chain employing a significant number of people from the farmer, to the marketer, the butcher, the meat seller, the food vendor and the commercial roasted/grilled meat vendor. Another important value chain is the traditional leather industry that depends on small ruminants’ skin as a major source of raw material. These value chains generate a cash flow that supports the livelihood of a large number of Nigerians across all 36 states. It is interesting to note that the goat meat has low cholesterol and is suitable for people on low energy diet which makes it a nutritional necessity for many. Additionally, the social value attached to the ram (male sheep) during festive seasons and the high preference for the goat meat as a special delicacy particularly in the southwest and southeast goes a long way to highlight the economic value of the livestock in the country.
Going by the 2016 livestock census, sheep numbered 41.3 million while goat numbered 72.5 million in Nigeria. The yield from this number shows high potential in revenue generation from the livestock sector. Although, the livestock population seems high, yet it has not met the national demand for animal protein, neither has it reflected in the GDP over the years. This is due to some challenges facing the small ruminant livestock sector, which includes the Peste des petits ruminants (PPR) disease.
PPR is an acute, contagious, and frequently fatal disease of sheep and goats, caused by a morbillivirus related to the viruses that cause rinderpest in cattle, measles in humans, and distemper in dogs. Depending on age and species (sheep are clinically more resistant than goats) the disease may be hyper-acute (mortality at 98% among 4–7 months old animals), acute (mortality at 60% among all population), mild (no mortality). When introduced to a naïve population, morbidity and mortality can reach almost 100%, causing a major shock to livestock keepers’ livelihood and to small ruminant market.
As a way of avoiding such shocks and losses, vaccination remains the main tool for controlling and eradicating this deadly PPR disease. Newborn animals from mothers with PPR antibodies (naturally immunized or vaccinated), can inherit maternal antibodies, through colostrum, and be protected from the infection for the first 2–4 months of their life. After this period, animals become fully susceptible. Kids and lambs should receive their first PPR vaccination at approximately 30 and 60 days of age to protect them against the disease. PPR vaccines currently in use are able to induce protective immunity against all known serotypes and immunity is lifelong. Infection is transmitted primarily by direct contact and the virus does not persist in the environment. Infected animals are infectious for a short period of time and there is no carrier state.
Looking forward, the Global Strategy for the Control and Eradication (GSCE) of PPR should be implemented by livestock farms at various levels. The strategy suggests mass vaccination (100%) of all animals older than 3 months of age in a first phase, followed by a phase of targeted vaccination of animals between 4 and 12 months of age. This strategy, if efficiently implemented will economically strengthen the livestock market, with an average benefit-cost ratio of 33.8. Consequently, an efficient surveillance of the PPR disease is essential to evaluate the effectiveness of all control and preventive strategies.
The surveillance process entails collecting, analyzing and interpreting all data generated from the identification of the virus, classification of the types and occurrence, vaccination and other activities involved in the control of PPR disease. The collection of samples and relevant data is usually carried out by Community Animal Health Workers (CAHWs) who are the first respondents to the disease occurrence. They are the farmer’s first point of call while they, in turn, transfer their collected samples for further analysis and report technical cases to veterinarians. The data gathered can be used to monitor changes in viral occurrence for example trends in the development of antimicrobial resistance, identify high-risk populations or areas to target interventions, and provide a valuable database of disease activity for future reference. Surveillance ensures that vaccination results in increased flock immunity, reduced disease incidence and eventually reduced virus circulation and its elimination ultimately.