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Scientists Estimate Impact of Pox Viruses on Nigerian Farms

03 August 2020

Scientists from The Pirbright Institute have shown that outbreaks of lumpy skin disease (LSD), sheeppox and goatpox (SGP) have an immediate and long-lasting impact on the livelihoods of farmers in North-East Nigeria.

Researchers analysed data from a study conducted with Bauchi State College of Agriculture to understand the burden these three diseases place on farmers and the tactics they employ to limit losses. These findings were then used to suggest potential methods for targeted control.

LSD and SGP are caused by infection with capripoxviruses and are found throughout large parts of Africa and Asia, occasionally entering Europe. They can cause severe disease in sheep, goats and cattle, resulting in substantial hardship to farmers in regions where smallholder farming is a large source of income and food.

The team surveyed 99 subsistence farmers that had been affected by outbreaks of LSD and SGP. The farms were classified as following either a backyard husbandry system (i.e. in a fixed location) or transhumance (i.e. move from one grazing area to another in seasonal fashion). Each farmer indicated the number of infected animals and animals that died as a result of LSD and/or SGP, as well as changes in weight and milk production, and the fate of the diseased animals.

This data enabled the team to estimate the economic impact of LSD and SGP and explore differences across farms. The results, published in Frontiers in Veterinary Science, showed that SGP was fatal in over 30 percent of sheep and goats, with even higher rates seen in younger animals. Mortality was less common in cattle with LSD, although they exhibited a 65 percent drop in milk production and never fully recovered even after the sickness had passed.

To cope with outbreaks, most of the farmers treated infected animals with antibiotics, which are not effective against viruses, although they may alleviate secondary bacterial infections. Many farmers decided to slaughter or sell infected animals – those that chose to sell were only able to recover around 50 percent of the price of a healthy animal. The team noted that backyard farmers tended to wait far longer before selling on affected animals than transhumance farmers.

Dr Georgina Limon-Vega, lead author of the study at Pirbright explains: “This could be because backyard farmers typically rear small herds, so any losses they sustain would affect their personal food supplies and would decrease the herd size dramatically. They therefore wait in the hope that animals will recover rather than selling them straight away. On the other hand, transhumance herds tend to be large, so they can sell infected animals quickly to protect the rest of the herd and still have enough left to fulfil their needs.”

The researchers were surprised to see that many farmers bought replacement animals from the same market they sold their infected animals. Livestock markets could therefore act as hubs for disease spread, but further studies are needed to investigate how their trading dynamics affect transmission.

A year on, most of the farmers had not replaced animals they had lost, showing that LSD and SGP have a lasting impact that is hard to recover from. Total financial losses on the herd value averaged 33 percent, with backyard farmers losing a larger proportion of their value than transhumance farmers.

As LSD and SGP vaccines are currently unavailable in Nigeria, the team recommended exploring control strategies based on tackling disease circulation in markets. Infected animals or those coming from affected herds could be separated from healthy animals at markets to lower chances of transmission and markets could be decontaminated when they are closed. Farmers would also benefit from increased awareness of the diseases and how they are transmitted so they can make informed choices when buying their animals.

“Conducting this type of study is essential to quantify and recognise how farmers are affected by livestock diseases. Understanding the pressures that they face and their coping mechanisms helps us to suggest potential tailored control strategies, rather than blanket procedures that may be ineffective”, finished Dr Limon-Vega.