General observations about FMD in sheep
- The onset of lameness is highly variable, 2 days to one week after infection or not at all.
- Lameness may be transient. Feet heel quickly unless there is secondary infection.
- Vesicles in the mouth rupture quickly, usually within a day, as the mucosa is thin
- Mouth lesions heal very quickly and there may be no evidence of infection as early as 5 days after the first appearance of lesions.
- A history of transient lameness in sheep may indicate the presence of foot-and-mouth disease virus in a flock of sheep.
The clinical signs observed in sheep during the current epidemic have been highly variable. The following cases are examples of clinical scenarios which have been reported to the epidemiology at Page Street.
Out of 572 sheep only 2 morbid sheep were observed
- off food, high temperature (lO6 deg. C.) and unwilling to rise, erosion on dental pad with fibrin. No other lesions.
- off food, temperature of 104deg. C, unwilling to rise, erosion on dental pad..
Three out of 80 sheep, were found to be lame
- Lame off-hind leg, temperature of 104.5 deg C. One ruptured vesicle on dental pad. No other lesions. Nothing seen on lame leg.
- Temperature of 104.5 deg C, lame, no visible lesions
- Temperature of 102 deg C, lame, ulcerated lesion above the coronary band on the off-hind foot.
25 out of 130 sheep appeared depressed with tender feet and droopy ears
- Several sheep were licking their lips. Three of the more severely affected sheep were examined. Newly ruptured vesicles were found on the dental pad and unruptured vesicles were present on the coronary band of all three.
Tracing of one wether which developed clinical signs 2 days after service of form D
- Temperature of 41 deg C, very dull, one vesicle on dental pad and ruptured vesicles on bulb of heel
Vesicles were found in 3 out of 580 sheep
Clinical signs were not observed in these sheep. There was no lameness, no depression, no salivation and no lip smacking. Vesicles were only discovered by detailed examination of the mouths and feet of all 580 sheep.
- A healing lesion covering the whole area of the dental pad and one small healing lesion just inside the upper lip. The feet were clear.
- An unruptured vesicle was found, by pulling the toes apart, in the interdigital area of the left fore. A ruptured vesicle was found inside the upper lip.
- A healing lesion was found inside the lower gum. The feet were clear.
Lameness in 5 out of 574 sheep consigned to a slaughterhouse
- Five sheep showed lameness at ante-mortem inspection and were not slaughtered. The following lesions were observed in only two of these sheep: split in the coronary band with loose epithelium; damaged epithelium in the interdigital cleft. There were no mouth lesions.
The following comments can be made about FMD virus, currently circulating in sheep:
- The morbidity is very low and clinical signs are generally mild and transient.
- Mouth lesions, when present, are usually accompanied by high temperatures.
- Foot vesicles, when present, do not always produce lameness and are not necessarily accompanied by high temperatures.
- A transient lameness may be observed in several sheep within a flock. Examination has then revealed clinical signs in individual sheep.
- Lameness in all four feet may be associated with splits between the cleats.
Clinical signs may not be evident on visual inspection and it may be necessary to check temperatures and examine the mouths and feet of all individual animals to establish the presence of FMD infection within a flock. Vesicles on the coronary band are unobtrusive and it is necessary to pull back the hair to observe them.