Taxonomy and biological properties of the pathogen
The foot-and-mouth disease pathogen belongs to the Picornaviridae family and is classified into a separate genus, Aphthovirus. Genetically, it is an RNA-containing virus. The classification of the pathogen includes a single species, which nevertheless features seven different serotypes. Morphologically and chemically, the foot-and-mouth disease virus bears significant resemblance to other members of the picornavirus group.
A key feature of the pathogen is its high virulence. The virus is characterized by pronounced dermatotropism—the ability to selectively infect cells of the skin and mucous membranes, causing local tissue defects.
Regarding resistance, Aphthovirus can persist in the external environment and in contaminated food products for a prolonged period, lasting several weeks. Despite this, the virus exhibits high susceptibility to chemical disinfectants, making their application an effective way to eliminate the pathogen from surfaces.
Infection epidemiology
Foot-and-mouth disease is a classic zoonosis. The primary natural reservoir and source of infection are sick animals. Cattle are the main source, but pigs, small ruminants, and rodents can also be involved in the epidemiological process.
Infected animals actively shed viral particles into the environment through various biological secretions, primarily milk, saliva, and urine.
There are two main routes of transmission for humans:
- Contact route: occurs primarily through direct handling of infected farm animals.
- Alimentary route: infection is transmitted by consuming raw milk or dairy products derived from infected livestock that have not undergone heat treatment.
Despite the variety of transmission routes, human susceptibility to the foot-and-mouth disease virus is generally considered low.
Clinical presentation in humans
Because the virus has pronounced dermatotropism, the clinical presentation in an infected person has highly specific, easily recognizable features. The disease proceeds with a marked febrile state.
The key and most striking symptom is the formation of aphthae—characteristic ulcerative lesions. They are most commonly localized on the oral mucosa, as well as on the skin of the patient's hands and feet.
Laboratory diagnostics and prevention
To confirm the diagnosis, specific clinical material is sent to the laboratory: aphthae contents, saliva, or the patient's blood.
Laboratory diagnostics rely on the following methods:
- Biological method: involves experimental inoculation of laboratory animals (traditionally guinea pigs and suckling mice). An alternative is inoculating the material into susceptible cell cultures for subsequent virus isolation.
- Serological method: based on testing paired serum samples from the patient to detect antibody dynamics. Various serological reactions are used for this: CF test (complement fixation test), neutralization test, HI test (hemagglutination inhibition), and ELISA (enzyme-linked immunosorbent assay).
Prevention of foot-and-mouth disease in humans is exclusively non-specific. Specific vaccines for humans are not used; protection is based on adhering to sanitary and hygienic standards when handling animals and heat-treating milk.
Briefly: answers to topical questions
What serotypes of the foot-and-mouth disease virus exist?
There are 7 serotypes of the foot-and-mouth disease virus. The pathogen is represented by a single species belonging to the Picornaviridae family, genus Aphthovirus. Animals that have recovered can be reinfected with a different serotype because only type-specific immunity develops in the body. Specific names of the existing serotypes are not provided in the materials.
What is the duration of the incubation period for foot-and-mouth disease in humans?
The duration of the incubation period for foot-and-mouth disease in humans ranges from 2 to 12 days. Most commonly, this latent period lasts 3–5 days. During this time, the virus interacts with epithelial cells at the site of entry (mucous membranes of the upper gastrointestinal tract or damaged skin). The pathogen enters via integrin receptors, followed by replication in the cell cytoplasm and subsequent viremia.
Which cell cultures are used to isolate the foot-and-mouth disease virus?
Tissue cultures from cattle, pigs, and sheep are used to isolate the foot-and-mouth disease virus.
In addition, the following models are used:
- Chicken embryos — developing embryos are suitable for successful cultivation.
- Cell cultures — in these, the virus has a short infectious cycle (2–4 days) and exhibits a direct cytopathic effect.
To identify the isolated pathogen in cell culture, a neutralization test using type-specific sera is applied.
What chemical disinfectants are used to destroy the foot-and-mouth disease virus?
Alkalis, acids, and formaldehyde are used to inactivate the foot-and-mouth disease virus. The virus is resistant to many chemicals and has low susceptibility to alcohol and ether.
"Aphthae on feet, hands, and in the mouth — foot-and-mouth disease virus (Aphthovirus) calls for livestock care." This helps remember the main symptoms (aphthae), lesion localization, and the primary reservoir of infection.
Class and exam questions
How can a human become infected with the foot-and-mouth disease virus?
Infection occurs via contact through caring for sick animals (cattle, pigs, etc.), as well as alimentary transmission through the consumption of raw contaminated milk.
Is there specific prevention of foot-and-mouth disease for humans?
No, humans only receive non-specific prevention, which includes following hygiene rules when working with animals and avoiding unpasteurized milk.
What methods are used for serological diagnostics of foot-and-mouth disease?
Serological diagnostics involves testing paired blood sera using the complement fixation test (CFT), neutralization test (NT), indirect hemagglutination assay (IHA), and ELISA.
What is the main clinical manifestation of foot-and-mouth disease in humans?
The main symptom is a febrile state combined with the formation of aphthae (ulcerative lesions) on the oral mucosa and the skin of the hands and feet.
What else to study on this topic
- Morphological structure of Picornaviridae viruses
- Features of the 7 serotypes of the foot-and-mouth disease virus
- Biological assays in guinea pigs and suckling mice: procedure technique
- Mechanisms of dermatotropism development in viruses
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