Livestock Foot and Mouth Disease: Signs, Causes & Control

This is a highly contagious viral disease of ruminants and pigs characterized by an initial fever and formation of vesicles on mucosae, and subsequently the erosion of the gum, tongue, and feet. It is clinically manifested by excessive salivation.

It is not highly fatal, but the lack of production and prohibition on the free movement of infected animals and their products make it one of the most serious animal diseases in the world.

Cause of Foot And Mouth Disease in Livestock

Foot and mouth disease in cattle and goats is caused by an Aphthovirus, one of the smallest viruses known. It has different immunological types (serotypes).

The serotypes include European types O, A, and C, which are prevalent in Europe and South America. SAT1, SAT2, and SAT3 are the main causative agents of outbreaks in Africa, while Asia-1 is responsible for outbreaks in countries such as Pakistan, Thailand, and Bangladesh in the Middle East region.

Note

There is no cross-immunity among the serotypes, and recent investigation shows that even the sub-serotypes are immunologically different from others in the same group. The virus is resistant to freezing and even some strong disinfectants, which can be carried by personnel (farm workers, vehicles).

Formalin (best), sodium carbonate, among others, kill the virus.  It can also be killed by boiling, and the virus can survive for a long time on premises where animals are kept.

Transmission of Foot And Mouth Disease in Livestock

The main method in which foot and mouth disease is transmitted is by ingestion, mainly via feeds, although wind-borne transmission can occur. The virus is present in milk and saliva before signs appear.

It can also be found in the urine and feces of affected animals, and all excretions contain the virus. Pigs contract the infection through the ingestion of meat scraps and can introduce infection into other areas.

Spread from the pigs to cattle is by the movement of people and abattoir waste. Birds can carry infection across borders. In the bone marrow of meat carcasses for 73 days, it can also survive in blood and lymph nodes for 2 months.

Foot and mouth disease in cattle

Clinical Signs of Foot And Mouth Disease in Livestock

1. The incubation period is 3-8 days (1-21 days)
2. High fever is more pronounced in young animals.
3. The fever is followed by dejection and anorexia, and stomatitis (acute and painful).
4. Abundant saliva hanging in long ropey strings.
5. Smacking of lips, slow and careful chewing.
6. Vesicles on buccal mucosae, dental pads, and tongue.
7. Vesicles rupture within 24 hours, leaving a raw, painful surface.
8. On the tongue, vesicles are on the dorsum and are thick-walled, giving the tongue an uneven appearance, which results in the emaciation of the infected animals.
9. Vesicles on the feet, especially the coronet, cause lameness, and the discomfort may lead to recumbency.
10. There is heat in the coronet area; in the long run, there may be a separation between the coronary border and the horn or hoof.
11. There are lesions on the udder in milking cows, which make the udder swollen and painful, leading to a reduction in milk production and rapid loss of condition.
12. There may be a malignant form of the disease-causing myocarditis (tiger disease) and consequent heart failure.
13. In sheep and goats, the course is usually very mild with no salivation, and the duration of the disease is shorter. Abortion may occur mostly in ewes (female sheep). There are lesions on the feet forcing the animals to kneel while eating and drinking, and Lambs may die due to gastroenteritis

Postmortem Findings of Foot And Mouth Disease in Livestock

In cattle, there are lesions on the feet and mouth, and this may also be found in the pharynx, esophagus, and in the 4 stomach chambers (rumen, reticulum, omasum, and abomasum) and trachea, and bronchi.

In the malignant form, myocarditis occurs, and the heart muscle shows streaks of yellow tissue, interspersed with the normal heart muscle.

Diagnosis of Foot And Mouth Disease in Livestock

The history of exposure provides clues to investigate the possibility of an animal having foot and mouth disease.

Clinical signs and postmortem findings (droopy salivation, fever, smacking lips, tiger heart).

Take samples - take intact lesions from feet, mouth & blood serum, and whole blood for laboratory examination.

In differential diagnosis, conditions without vesicles and non-ropy salivation, such as Rinderpest, often have a high mortality rate.

Vesicular stomatitis is characterized by the absence of lesions on the feet and teats, and samples should be taken for laboratory examination.

This disease is mainly found in temperate areas. Rabies is identified by drooling saliva and nervous involvement with pica (eating non-nutritious items).

In Lumpy Jaw, saliva drips, and the disease is bacterial, affecting the jaw bones and causing swelling.

Footrot affects only one or two animals, while Foot and Mouth Disease affects the entire herd.

Treatment of Foot And Mouth Disease in Livestock

There is no specific treatment. The treatment of infected animals mainly involves the use of antibiotics, flunixin meglumine, and mild disinfectants.

Here only occasionally undertaken to cater for secondary bacterial infection. Where slaughter is not compulsory, treatment with disinfectants and the use of protective clothing may also shorten the course of the disease, and mouthwash with potassium permanganate oxide or wound spray may be attempted.

Control of Foot And Mouth Disease in Livestock

Foot and mouth disease is difficult to control because there are several ways in which it is spread. Multiple hosts are involved in the spread of the disease, and viral antigens are involved.

Animals that have been vaccinated can develop short-lived immunity, lasting only 2-3 years, while the virus may be able to persist in certain environmental conditions, leading to viral resistance.

The Following Can be Done in Case of The Outbreak

To effectively control the outbreak of Foot and Mouth Disease, it is crucial to announce its presence. This will prompt the Commissioner of Veterinary Services to impose a quarantine in the affected area, preventing the movement of animals and animal products in and out of the outbreak zone.

As a precautionary measure, it is advisable to slaughter highly susceptible animal species to create a buffer zone of approximately 10km to protect neighboring animals.

Within the outbreak zone, a 40km wide ring vaccination of all cattle should be carried out following a vaccination program for calves.

The immunity generated lasts for 2-3 years, after which it is important to revaccinate your animals. This process should be repeated annually for an indefinite period.

Note: In the case of any vaccination program. The vaccine to be used should contain the specific antigen that is present in that area and a slaughter policy should be practiced.

The Economic Impact of Foot And Mouth Disease

This is a notifiable disease affecting all cloven-hoofed animals. The virus is resistant to sunlight, disinfectants, and processing methods such as cheese, pasteurized milk, and frozen semen.

The presence of the disease leads to restrictions on the movement of animals and their by-products, resulting in economic losses such as the inability to sell hides and skins, meat, milk, semen, and others.

Controlling the disease is expensive as it requires multiple drugs, including antibiotics, sprays, and disinfectants, and has a high morbidity rate of over 80% but low mortality of 5%.

There may also be a permanent impact, such as a 25% reduction in milk production or infertility, even after recovery.

This disease is a global issue and affects animals worldwide.

Problems in Controlling Foot And Mouth Disease

1. Cloven-footed wildlife is affected, and it is difficult to enforce the quarantine.
2. It is difficult for farmers to move their animals from one place to another.
3. It is difficult/impossible for the government to compensate farmers for their animals or losses as a result of the disease in some countries.

Conclusion

In conclusion, Foot and Mouth Disease poses a significant threat to livestock worldwide. This highly contagious viral disease can result in substantial economic losses due to restrictions on the movement of animals and their products. While not highly fatal, the disease causes a lack of production and can lead to serious complications in infected animals.

The disease is caused by different serotypes of the Aphthovirus, and there is no cross-immunity among these serotypes. It is primarily transmitted through ingestion and can also spread through wind, milk, saliva, urine, feces, and even birds. The clinical signs include fever, excessive salivation, vesicles on mucosae, erosion of the gums and feet, and reduced milk production.

Controlling Foot and Mouth Disease is a challenging task due to its multiple hosts and resistance to environmental conditions. Vaccination programs and quarantine measures play a crucial role in managing outbreaks. However, there are difficulties in enforcing quarantines, compensating farmers for losses, and controlling the disease in wildlife.