(Apthous fever, contagious aptha, Vesicular aptha) Foot and Mouth Disease (FMD) is an acute febrile contagious disease of cloven footed animals. Disease is characterised by high fever and vesicular eruptions in the mouth, feet and teats and udder. Epithelium and mucus membranes are mostly affected. Skin at certain regions like muzzle, teat, udder, skin at base of horns and nares are also affected. Cattle and pigs are most susceptible. Constant contact can cause mild form of FMD in human beings, dogs and cat. It is caused by Picorna virus, the smallest known virus of animal origin. This RNA virus is having seven distinct types, viz. O (Oise valley in France), A (Alemand in France), C, Asia 1, SAT I (South African Territories), SAT II and SAT III. Virus is resistant to alcohol, ether and chloroform. Most effective disinfectants are 1 – 2 % Sodium hydroxide (NaOH), formalin or 4% Sodium Carbonate (NaCo3) solution. Virus can remain in infected premises for one year, three months in human clothing, 4-5 months in hay and bran, one month in hairs of animal and for one year in frozen semen without losing potency. Boiling for 15 minutes will destroy the virus. Virus can be preserved in Glycerine Phosphate Buffer with a pH of 7.6 (virus is stable between a pH of 7.4 – 7.6). Virus is not stable at pH above 11 or below 6. Virus can be cultured in living chicken embryo, testicular cell culture of cattle and pig, thyroid and kidney cell culture of bovine. Plaque is formed in culture. Guinea pigs, mice, chicks and rabbits are infected experimentally. Transmission: Virus is highly contagious and have short incubation period (2-8 days). In halation and ingestion are main route of infection. In a farm virus may gain entry through food stuff, feeding utensils, waterer and infective materials. All secretions and excretions like urine, saliva, milk and faeces of infected animals remain infective. It has been suggested that, cattle serve as indicator, sheep as maintenance host and pigs as amplifier host. Free living birds and human and animal movement carries the infection from one place to another. Pathogenesis: Immediately after entry virus will divide and cause slight raised blanched appearance known as primary lesion. From here virus will enter to lymph and then to blood stream. Stage of viraemia and a high rise in temperature occurs (104-106˚F). Virus will concentrate in certain predilection sites like lining mucus membrane of digestive and respiratory tract. Virus will cause degenerative and cytolytic changes and development of pockets at various locations. There fluids will accumulate and vesicle will form. Vesicles can be observed in epithelium of mouth, dental pad, feet and udder. Immediately after vesicle formation fever will subside and virus disappears from blood. At this time virus can be isolated from vesicular fluid. Within two days vesicles will rupture (erosion) and highly vascular area appears. Clinical findings: Morbidity is 100% and mortality is more in young animals where there is direct involvement of myocardium is there (myocarditis and myocardial degeneration). Loss of appetite, rise in temperature, stingy salivation, reluctance to move, formation of vesicles, smacking sound, reduction in milk production, development of mastitis. Chronic condition leads to a situation called panters (panting even after moderate exercise). Hairs at cervical region, face and shoulder become very long. They lose their capacity to react with temperature variation due to endocrine damage. In pigs haemorrhages can be seen between hoof and skin and this is very characteristic. Lameness is more predominant, rise in temperature, loss of appetite, vesicle formation in the inter-digital space, abortion and 100 % mortality in piglets. In sheep, predominant lesion is lameness. In goats, oral lesions are more. Head as such may swell. Lesions: characteristic lesions are vesicles and ulceration. Heart muscles of young animals show grey or yellow foci or streaks in myocardium which is described as “Tiger Heart”. Rumen pillar may show typical eroded lesions. Diagnosis: Symptoms. Laboratory diagnosis: Collection of vesicular fluid and dorsal surface of tongue in vials packed in ice and overall packing with thermo cool box. CFT, NT, AGPT, FAT, ELISA are the tests employed. Animal inoculation studies are conducted in mice or guinea pig with suspected materials. Foot pad inoculation is done in guinea pig. Vesicles will appear in 1-7 days of inoculation. In mice inoculation is done through IM or IP route. Positive specimen will produce degenerative changes skeletal muscles and myocardium. Differential diagnosis: FMD won’t affect Horse. But Vesicular stomatitis will affect cattle, pig, sheep, goat, horse and guinea pig. Vesicular Exanthema affects only Pigs. Blue tongue affects Cattle, sheep and goat. Treatment: Symptomatic treatment. Mouth lesions can be washed with astringent like alum (1-2%) or 1% Potassium permanganate solution. Sticky dressing powder with glycerine or honey and Boric acid (Mel boracis) is most commonly used. Dressing powder containing antiseptic fly repellents, astringent and sticky materials are preferred for inter-digital lesions. Feet may be washed with 2% copper sulphate solution. Along with this, long acting antibiotics also should be given. Control: Restriction of animal movement, vaccination of animals, isolation of the affected animals, restriction of movement of animal attendants, attend the healthy animals first and restriction of suckling calves from taking milk from affected mothers. Vaccination: 1. Formalised vaccine: affected materials were triturated and formalised and inoculated. 2. Formalised Aluminium hydroxide gel vaccine: 0.05% formalin added and Aluminium hydroxide gel is used for adsorption of virus. SC route but dose required is more (30 mL). 3. Crystal violet vaccine: SC route, dose is high (30 mL), immunity for 1year to 1 year and six months. 4. a. Polyvalent vaccine (by Baif): Containing O, A, C, Asia 1 and Asia 22. Cell culture vaccine dose is only 5 mL (route SC) for sheep and goat, but 10 mL for cattle, buffalo and calf. Calves are vaccinated at an age of 6-8 weeks and booster is given at 4 months of age and then six months later. In adult animals’ booster should be given 3-4 months after primary vaccination. 4. b. Polyvalent vaccine (by Hoechst): Containing O, A, C and Asia. Cell culture vaccine dose is only 5 mL (route SC) for sheep and goat, but 10 mL for cattle, buffalo and calf. Initial vaccination can be done at 3 weeks and above, booster within 3 months and revaccination every six months thereafter. 4. c. Polyvalent vaccine –Raksha FMD (by Indian Immunologicals): Containing O, A, C, Asia 1 and Asia 22 (inactivated by aziridine compound). Cell culture vaccine dose is only 1 mL (route SC) for sheep and goat, but 3 mL for cattle, buffalo and calf. Initial vaccination can be done at 4 months, booster within 2-4 weeks and revaccination every six months thereafter. 4. d. Polyvalent vaccine –Raksha O vac (by Indian Immunologicals): Adjuvanted by mineral oil (inactivated by aziridine compound). Dose: Cattle, buffalo, calf and pigs - 2 mL, IM. Initial vaccination can be done at 4 months, and revaccination every nine months thereafter. Goat and sheep: 1 mL, IM. Initial vaccination can be done at 4 months, and revaccination every nine months thereafter.
