29/04/2020
Foot and mouth disease (FMD, Aphthous fever)
is an acute viral and extremely contagious disease of cloven footed animals such as cattle,sheep, goats, pigs and antelope.
It is manifested by vesicles and erosions in the muzzle, nares,mouth, feet, teats, udder and pillar of the rumen. There are three main strains of viruses causingFMD, namely A, O and C.
Three additional strains, SAT 1, SAT 2 and SAT 3 have been isolatedfrom Africa and a further strain ASIA-1 from Asia and the Far East.
: Direct and indirect contact with infected animals and their secretions including
saliva, blood, urine, faeces, milk and semen, aerosol droplet dispersion, infected animal byproducts, swill containing scraps of meat or other animal tissue and fomites and vaccines.
:
Before vesicle formation:
1. Incubation is 1 - 5 days or longer
2. Morbidity: Nearly 100 %
3. Mortality: variable depending on the strain of virus and its virulence and susceptibility of
host; 50 % in young animals, 5 % in adults
4. Fever up to 41.7°C
5. Dullness
6. Lack of appetite
7. Drastic drop in milk production.
8. Uneasiness and muscle tremors
Vesicle formation:
9. Smacking and quivering of lips
10. Extensive salivation and drooling
11. Shaking of feet and lameness
The vesicles and later erosions are commonly found on the muzzle, tongue , oral
cavity, teat and on the skin between and above the hoofs of the feet. In more chronic cases in
cattle the hoof become loose and the animal may walk with characteristic “clicking” sound
(Slippering).
Some strains of FMD, particularly in swine, sheep and goats cause erosions instead of vesicles
findings :
1. Necrosis of heart muscle(tiger heart), usually only in young acutely infected animals.
2. Ulcerative lesions on tongue, palate, gums, pillars of the rumen and feet.
Judgement : In countries or in zones within a country free or nearly free of FMD diseased or
suspect animals are prohibited to be admitted in an abattoir or slaughtered. If FMD is suspected
on postmortem examination the carcass and viscera are condemned and appropriate action
recommended by the regulatory authorities of the country must be taken. In countries where this
disease is present, the judgement should be in accordance with the current animal health
requirements, and consisted with effective public health protection. Particular attention should
be paid to secondary bacterial infections and general findings. Sanitary measures should be
taken to comply with national animal health policy.
Remarks : Latent infections with Salmonella organisms were reported in animals affected with
FMD.
in bovine and ovine species
:
1:Vesicular stomatitis,
2:allergic stomatitis,
3:feedlot glossitis,
4: photosensitization,
5:bluetongue,
6:rinderpest,
7:infectious bovine rhinotracheitis,
8:malignant catarrhal fever,
9:bovine papular stomatitis,
10:bovine viral diarrhoea,
11:pseudocowpox,
12:ovine pox,
13:contagious ecthyma,
14:footrot,
15:mycotoxicosis and increased salt in concentrate.
: In order to prevent the spread of the virus in the abattoir, the equipment and room should be disinfected with 2 % NaOH (caustic soda). In some countries sodium carbonate (Na2CO3) is used.
The vehicle conveying diseased animals should also be disinfected and abattoir personnel leaving the abattoir should pass through a footbath with 1 % solution of
NaOH.
The virus of FMD can survive in meat and meat products for a considerable length of time.
Outside the pH range of 6 – 9, viral infectivity is destroyed. A bovine carcass matured at above
+2°C produces a drop in the pH of muscle tissue to between 5.3 – 5.7 within 24 hours of
slaughter.
This is caused by the formation of sarcolactic acid. Quick freezing of the meat arrests acid production and consequently the virus remains infective for about 6 months.
In salted meat at 4°C, the virus is still infective in bone marrow and lymph nodes for 6 months.
In blood clots in large vessels of cattle and swine, the virus is infective for 2 months. The virus is inactivated by ultraviolet rays, acetic acid, 2 % lye and ethylene oxide. At high temperatures, the virus is only
active for a short period. 2 % NaOH solution inactivates the virus in 1 – 2 minutes. In dry refusein stalls, the virus remains infective for 14 days, 3 days on soil surfaces in summer compared to39 days in fall. It is also infective for 39 days in urine and for 20 weeks on hay dried at 22°C.
The virus can be destroyed with 0.5 % citric or lactic acid, by cooking meat to an internal
temperature of 69°C and by pasteurization processes of milk.
Abdullahi mohamed hassan
Dr:Adnan
