foot and mouth disease-
Definition :
foot and mouth disease (sometimes called hoof and mouth disease) is a highly contagious acute disease of all cloven-footed animals caused by aphthovirus characterized by fever and vesicular eruption in the mouth and on the feet .
Etiology :
Picorna virus which is member of the genus aphthovirus.
There are seven serotype of FMD virus : A , O , C , Asia-1 and southern african territories (SAT) 1 , 2 and 3 .
Picorna virus is non enveloped , icosahedral and containing single strained RNA .
Picorna virus is inactivated by temperature above 50 C.
Picorna virus is inactivated by PH lesser than 6.0 or PH more than 9.0 .
Picorna virus is inactivated by NaOH (2 %) , Na2CO3 (4 %) and the citric acid (.2 %) .
It is sensetive to environmental influence as sunlight and dessication .
It survives for long period at freezing temperature .
Epidemiology :
a)geographical distribution .
Endemic .
Asia , Africa . the middle east , south America and Europe .
Currently , the OIE recognizes countries to be in one of the three diseases states with regardes to FMD
1-FMD present with or without vaccination .
2-FMD free with vaccination
3-FMA free without vaccination.
b)host range
Cloven footed domestic (cattle , buffaloes , sheep , goats and swine and somewild animals ).
Other susceptible species , elephants , rats and mice .
Camelidae (camel ) has low susceptibility.
Horses are not susciptable to FMD and humans are rarly affected.
Morbidity :
100% in susceptible population of domestic animals .
Mortality :
Less than 1% but very high in young animals due to myocarditis.
Sources of virus :
1-Incubating and clinically affected animals .
2-Breathe , saliva , feces , urine , milk and semen (up to 4 days before clinical signs ).
3-Meat and by-products in which PH has remained above 6 .
4-Carriers animals particularly cattle and water buffalo .
5-Recovered cattle may be carrier for 18 to 24 months and recovered sheep may be carrier for 1 - 2 months .
Transmission :
_Direct or indirect contact (mainly by inhalation , ingestion and artificial insemination ).
_Vectors : animate ( humans , pigs , birds ) or inanimate (vehicles ,implement )
_spread over greater distances with movement of infected or contaminated animals , products , objects and people .
Pathogenesis :
Inhalation or ingestion from infected animals and their products.
Replication in the epithelium of the upper respiratory tract or alimentary tract.
Vesicles are formed in 1 -4 days in the lips or oral mucosa .
Followed by viremia and pyrexia .
Secondary vesicles are formed 2 days later .
Hydropic degeneration (balloon degeneration ) followed by necrosis .
In young animals , the virus tends to localize in the myocardium (known as tiger heart ) leading to sudden death .
NB grayish or yellowish streaking in the myocardium (degeneration and necrosis ) in heart of young animal and called tiger heart .
Incubation period 2 to 21 days ( average 3-8 days )
Clinical finding :
_Fever ( 103 to 105 F )
_Dullness.
_Anorexia
_Shivering
_Reduction in milk production for 2 - 3 days.
_Blisters on buccal and nasal mucosal membrane including mouth , tongue and lips .
_Blisters between claws and coronary band and evenon the udder and teat .
_After 24 hours , rupture vesicle leaving erosion .
_sticky , foamy , stringy saliva drips from the mouth of animal.
_Painful tongue and mouth that decrease in appetites ,resulting in loss weight .
Signs in sheep and goats
_Lesions are less pronounced .
_Foot lesions may go unrecognized.
_Lesions in dental pad of sheep.
_Agalactia
Signs in pig
_ Lesions are observed in snout.
_ Sever foot lesions particularly when it is housed on concrete .
_ High mortality in piglets .
Sequelae to FMD in cattle
_ Tongue erosions .
_ Hoof deformation .
_ Mastitis .
_ Breeding problems .
_ Secondary infection .
_ Abortion .
_ Low milk production .
_ Myocarditis and death in young .
_ Diabetes mellitus .
_Panting
_Pituitary gland damage .
Diagnosis
_ case history .
_ clinical signs .
_ collection samples / specimens ( oral , nasal , foot or mammary lesions are good sources of specimens , vesicular fluid , epithelium covering a vesicle (.5 gm ) , about 5 ml blood with anticoagulant , esophageal - pharyngeal fluid .
_ isolation and identification .
10 % suspension preparation .
Inoculation into susceptible tissue culture ( primary bovine thyroid cells and primary pig, calf and lamb kidney cells ,inoculation of BHL-21 and IB-RS-2 cell lines )
_ CFT , ELISA and RT PCR .
Differential diagnosis
1- FMD : vesicle , myocarditis and gastroentritis .
2- VE ( vesicular exanthema ) : vesicle but no myocarditis and gastroenteritis .
3-VS (vesicular stomatitis ) : less conspicuous vesicles , no myocarditis and gastrointeritis .
Treatment
_Washing affected area with mild disinfectant ( 2% caustic soda , 4% soda ash ,and 2% acetic acid )
_ Applying antibiotics locally .
_ protective dressing to inflamed area to prevent secondary infection .
_Sulfadimidine or broad-spectrum antibiotics injections are useful to the secondary bacterial infection .
_ A good systemic response is reported to the administration of flunixin meglumine .
_ Fly repellent must be used.
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