Foot-and-mouth disease – overview - PowerPoint Presentation

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Foot-and-mouth disease – overview

In South Africa the initial transmission of foot-and-mouth disease (FMD) takes place from infected carrier buffalo to cattle. FMD outbreaks in South Africa occur mainly when there has been contact between cattle and infected buffalo in the area along the Kruger National Park.

FMD is a viral disease and one of the most contagious in the world.

An infected animal will become sick and show signs of the disease within three days to a maximum of 14 days (incubation period).

The animal will usually recover within 7-14 days as it will develop its own immunity against the disease.

The virus will affect all cloven-hooved farm animals and game species, but under local conditions where SAT strains occur, it will be found mostly in cattle.

Further transmission and disease spread occurs when

an infected bovine becomes sick while in direct contact with or being in the direct vicinity of healthy cattle

or other cloven-hooved livestock.

An outbreak will spread even further if infected or sick cattle and other cloven-hooved farm animals are then transported to areas where the disease does not yet occur.

The virus can also be exhaled and form micro-drops which can be spread across greater distances via the wind.

Airborne transmission can play a major role where a large number of cattle are found in close proximity to one another, e.g. in a feedlot, at an auction or a livestock event.

To date transmission across long distances (e.g. more than a kilometre) has not played a major role in the spread of the disease in South Africa.

However, animals that have recovered from the disease, can carry the virus at a very low level for 28 days and even longer. Transmission from such cattle to susceptible cattle has, however, not yet been proven to be a high-risk route of transmission in South Africa.

The mortality rate is very low (<5%) with the exception of very young animals, in which case the rate can be much higher. Production can be affected and animals will lose a lot of condition.

People who were in physical contact with the animals during the phase when animals exhibit signs of the disease, can be temporarily infected and transmit the disease to other susceptible animals if they come into close contact with them within 48 hours.

The virus can also survive in the environment (manure, infected instruments, hay, vehicles that transported infected animals). Once the virus dries out it will die much quicker, but it can for example survive in damp manure under warm conditions with high humidity for more than 30 days.

As this is a viral disease, there is no primary treatment. Only supportive treatment is possible and the animal must develop its own immunity in order to recover.

FMD disease signs 

Observations

Saliva flow

Saliva flowing from the mouth is usually one of the first signs indicating that the animal, specifically cattle, is infected.Saliva can be foamy and slightly bloody.Animal does not want to eat.Animal looks sick and won’t eat due to mouth lesions.Nasal discharge and possibly also eye discharge.LamenessMore than one foot is affected and in many cases all the feet are affected.Later on the animal will stand with a arched back because of the pain caused by the foot lesions.During the recent FMD outbreak (2019/20 Limpopo) foot lesions and and severe lameness were not as visible.

Examination of animal

Animal initially has a high fever.

Blisters in the mucosa of the mouth.

Blisters on the top surface of the tongue, boonste hard palate, gums and inside of the cheeks.Mouth blisters are usually not noticed during the examination, as they normally merge very quickly and burst open.Open sores in the mucosa of the mouth after blisters have burst open.In some cases there is loose mucosa on the edges of the sores, representing the remainders of blisters that have burst open.Blisters between the hooves at the top corner where the the hooves join.Red inflammation line on the attachment between the edge of the hoof and the skin – seen more often in small-stock.Open sores between the claws once the blisters are open.

More than one hoof will be affected, often all the hooves.In animals that have recovered, the hoof’s edge can be separated where it attaches to the skin.

Disease transmission mainly takes place from bovine to bovine

just prior to and in the few days after

having observed the first disease signs.

Under South African conditions in which the SAT strains of the virus are involved, the risk of disease transfer is lowered by 95%,

where one is able to prevent contact between a sick animal and a healthy animal.