What causes fmd in cattle

Overview

Foot-and-mouth disease (FMD) is a severe, highly contagious viral disease that affects cloven-hoofed animals, with cattle being particularly susceptible. It is characterized by fever and the formation of vesicles (blisters) and erosions, primarily in the mouth, on the tongue, on the teats, and on the skin above the hooves. While FMD is rarely fatal in adult cattle, it can cause significant morbidity, leading to reduced milk production, weight loss, lameness, and decreased fertility. In young animals, mortality rates can be higher. The economic impact of FMD outbreaks is immense, primarily due to trade embargoes imposed on affected countries and the costs associated with control and eradication measures.

What Causes Foot-and-Mouth Disease in Cattle?

The causative agent of FMD is the Foot-and-Mouth Disease Virus (FMDV). This virus is a non-enveloped RNA virus belonging to the genus Aphthovirus within the family Picornaviridae. There are seven distinct serotypes of FMDV: O, A, C, SAT1, SAT2, SAT3, and Asia1. Crucially, infection with one serotype does not confer immunity to other serotypes, meaning an animal can be infected multiple times if exposed to different serotypes. Within these serotypes, there are further variations, known as topotypes, which can influence the virus's geographical distribution and virulence.

How Does FMD Virus Spread?

FMDV is extremely contagious and can spread through several routes:

Direct Contact:

This is the most common mode of transmission. The virus is shed in high concentrations in vesicular fluid, saliva, milk, semen, and feces of infected animals. Healthy animals can become infected by coming into direct contact with infected animals or their excretions.

Airborne Transmission:

FMDV can be transmitted over long distances through the air, particularly in temperate climates when wind conditions are favorable. This is especially a concern with cattle, which shed large quantities of the virus. Aerosols containing the virus can travel for many kilometers from an infected premises.

Indirect Transmission (Contamination):

The virus can survive for extended periods on contaminated objects, known as fomites. This includes:

• Vehicles and Equipment: Farm machinery, vehicles, and equipment that have been in contact with infected animals or their environments.
• Animal Products: Uncooked or improperly processed meat, milk, and dairy products from infected animals can harbor the virus.
• Feed and Water: Contaminated feed or water sources can spread the virus to susceptible animals.
• Clothing and Footwear: People moving between infected and uninfected premises can carry the virus on their clothing, footwear, and hands.

Infected Animals Shedding the Virus:

Animals that recover from FMD can sometimes become carriers, continuing to shed the virus for months, particularly in their pharyngeal region. This chronic shedding can act as a reservoir for future outbreaks.

Factors Influencing Spread:

Several factors can influence the rate and extent of FMD spread:

• Animal Density: High densities of susceptible animals in close proximity facilitate rapid transmission.
• Climate: Temperate climates with prevailing winds can enhance airborne spread. Humidity and temperature also play a role in virus survival.
• Biosecurity Measures: The effectiveness of biosecurity protocols on farms and at borders significantly impacts the risk of introduction and spread.
• Movement of Animals: The movement of infected or contaminated animals, their products, or materials across regions or borders is a major driver of FMD epidemics.

Understanding the viral etiology and the diverse transmission pathways of FMD is crucial for implementing effective prevention, control, and eradication strategies to protect cattle populations and the agricultural economy.