**4. Clinical signs**

By carrying out epidemiological investigation, we can estimate how long has the disease been on the farm, where did the disease come from, and where the disease might have spread to. To establish a likely time period of infection dynamics took place in animals of the farm, aging clinical lesions is important. Looking for the oldest lesions allows identify‐ ing the time of first infection in the herd. Clinical examination starts by taking history about type and time of clinical signs and affected animals from the farmer. Then, the ani‐ mals from a distance to see general demeanor, salivation, lameness, or ataxia were ob‐ served. When we examine the individual animal, check the mouth (especially in cattle) then the feet (in pigs) in order.

The clinical signs of FMD were the most clearly manifested in pigs followed by dairy cat‐ tle comparing to other species. In the epidemic of 2010/2011, only 2.6% of the dairy cattle farms and 1.9% of the pig farms were subclinically infected, while no clinical signs of FMD was observed in 10‐20% of the outbreak farms with beef cattle, deer, or goats. For beef cattle, the number of farms with ulcers (n = 408, 28.6%) was higher than that showing vesicles (n = 316, 22.2%). For dairy cattle, on the contrary, vesicles (n = 166, 32.6%) were more frequent than ulcers (n = 107, 21.0%) in dairy cattle farms. In 58.9% of the pig farms, vesicle was the most dominant sign of FMD. In pigs, more severe signs, such as lameness or ataxia (14.6%) and shedding of claws (4.6%), were also distinctively shown. Another clinical characteristic observed in the 2010/2011 FMD epidemic was sudden death of suck‐ ling piglets, which was observed in 21.2% of pig farms. The average age of the oldest lesion in an outbreak farm was higher in the vaccinated than the non‐vaccinated in cattle, while it was higher in non‐vaccinated in pigs. Considering that vaccination was firstly performed on cattle then on pigs, and the outbreaks continued only in pig farms at the later phase of the epidemic, difference of lesions' age between cattle and pig at detecting seemed mainly associated with farmers' attention and recognition [11].

In the epidemic of 2014/2015, any clinical signs of FMD were observed in all of the 185 outbreak farms. Vesicles, which were observed 65.0% of the outbreak pig farms, were the most promi‐ nent clinical signs, followed by lameness (43.9%), ataxia (38.9%), and hemorrhage in hooves (25.0%) [9].
