This study is the first to report that buffaloes exposed to foot and mouth disease virus (FMDV) can also develop symptoms such as a high body temperature, just like cattle. Doctors dealing with animal health issues can use this information to understand more about how buffaloes respond to infection by FMDV.
Foot-and-mouth disease (FMD) negatively affects the lives of many farmers in Africa because when there is an outbreak, farmers are unable to sell their cattle. Cattle with FMD develop a fever, and blisters on their tongue, mouth, nose and feet. Researchers knew that buffaloes carry the FMDV, but they did not know much about how it affects them, as compared to cattle.
In this study, the researchers thus looked specifically at how FMDV affects buffaloes.
They divided 24 buffaloes into 6 groups of 4. They injected buffaloes in 3 of the groups with 3 different types of FMDV (the types are called AT1, SAT2 and SAT3). After 2 days, they allowed the injected buffaloes to mix (make contact) with those not injected with FMDV.
The researchers observed the buffaloes for 30 days. They recorded their body temperatures and measured the amount of virus in their blood, throat and noses. They also checked for antibodies, which are special molecules that the body’s immune system produces to fight infection or disease caused by viruses, bacteria or other microorganisms.
The researchers found that the injected buffaloes showed mild signs of FMD and a high body temperature (up to 39.5°C), which dropped after 4 days. They said 2 injected buffaloes had small blisters in their mouths. After 2-9 days of mixing, all non-injected buffaloes also got infected but did not develop any blisters.
Interestingly, the researchers found that buffaloes injected with virus type SAT2 were quick to have a high temperature and for longer periods. However, they did not find any relationship between increased temperature and viral loads (the amount of virus in the body).
The researchers said they were able to detect FMDV in the injected buffaloes 2 days after injection, and after several days in the non-injected buffaloes. The virus numbers reduced with time. They also said that as soon as they noticed antibodies in the blood, FMDV had been cleared completely, meaning the immune system was able to fight the infection.
They said they did not observe any change in total white blood cell count in all buffaloes, but they reported possible swelling. The body’s immune system produces white blood cells, or leukocytes, during an infection to help defend against the infection.
They said their study was the first to show that African buffalo were indeed also affected by FMDV to an extent that they developed a high body temperature (fever).
But, the researchers recommended more studies to understand why African buffaloes only get mild symptoms, unlike cattle.
The researchers were based in South Africa and the USA.
Foot-and-mouth disease (FMD) is one of the most important livestock diseases restricting international trade. While it is clear that African buffalo (Syncerus caffer) act as the main wildlife reservoir, viral and immune response dynamics during FMD virus acute infection have not been described before in this species. We used experimental needle inoculation and contact infections with three Southern African Territories serotypes to assess clinical, virological and immunological dynamics for thirty days post infection. Clinical FMD in the needle inoculated buffaloes was mild and characterised by pyrexia. Despite the absence of generalised vesicles, all contact animals were readily infected with their respective serotypes within the first 2-9 days after being mixed with needle challenged buffaloes. Irrespective of the route of infection or serotype there were positive associations between the viral loads in blood and the induction of host innate pro-inflammatory cytokines and acute phase proteins. Viral loads in blood and tonsils were tightly correlated during the acute phase of the infection, however, viraemia significantly declined after a peak at 4 days post infection (dpi), which correlated with the presence of detectable neutralising antibodies. In contrast, infectious virus was isolated in the tonsils until the last sampling point (30 dpi) in most animals. The pattern of virus detection in serum and tonsil swabs was similar for all three serotypes in the direct challenged and contact challenged animals.
We have demonstrated for the first time, that African buffalo are indeed systemically affected by FMD virus and clinical FMD in buffalo is characterized by a transient pyrexia. Despite the lack of FMD lesions, infection of African buffalo was characterised by high viral loads in blood and oropharynx, rapid and strong host innate and adaptive immune responses and high transmissibility.
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