| Occurrence - Foot and mouth disease (FMD) is a
disease that is endemic in many countries, including much of
Africa, Asia, and South America. It affects all cloven-hoofed
animals and is the most contagious of animal diseases. In
animals the disease presents with acute fever, followed
by the development of blisters chiefly in the mouth and
on the feet. Infected animals secrete numerous virus
particles before clinical signs appear.
Infectious
agent - It is caused by a virus of the family
Picornaviridae, genus Aphthovirus, of which there are
different serotypes:O, A, C, SAT1, SAT2, SAT3, and
Asia1. The current outbreak in countries in the European
Union is due to the highly virulent pan-Asiatic
serotype O.
Identification
in humans - Although FMD may affect humans, its occurrence is
quite rare and the human disease is benign. Given the high
incidence of the disease in animals, both in past and
recent outbreaks worldwide, the FMD virus has been
isolated and typed in not more than 40 patients during the last
century, and one case was an asymptomatic infection. The type of
virus most often isolated in humans is type O followed by type C
and rarely A.
Symptoms:
These have been mostly mild and self-limiting -
mainly uncomfortable tingling blisters on the hands but
also fever, sore throat, and blisters on the feet and
in the mouth and tongue. Patients have usually recovered a week
after the last blister
formation.
Mode of
transmission in humans - The circumstances in which it
occurs in humans are not well defined, though all
reported human cases have had close contact with
infected animals or drank raw milk from infected
cows. In 1834, in Hertwig, Germany, three veterinarians
self-infected themselves by drinking 250 ml of milk from infected
cows on four consecutive days. The three men developed clinical
manifestations. There is no report of infection from
pasteurized milk, and it is generally accepted that FMD
has no implications for the human food chain.
Incubation
period - The incubation period in humans is 2-6
days.
Person-to-person spread has not been
reported. Suspected and confirmed human cases
must have no contact with susceptible livestock to avoid
transmitting the disease to animals.
Diagnosis -
FMD should not be confused with the human disease hand, foot, and
mouth disease. This is an unrelated and usually mild
viral infection, principally of children, caused by
different viruses, primarily coxsackie A virus. The disease can
also be confused with herpes simplex and sometimes vesicular
stomatitis.
Laboratory diagnosis – Criteria for establishing
a diagnosis of FMD in humans are the isolation of the virus from
the patient and/or identification of specific antibodies after
infection. Laboratory tests for diagnosis of human FMD are the
same as for animals.
Control of FMD
in humans – Prevention of the disease in humans consists
mainly of controlling the disease in domestic animals. However,
wounds or abrasions of persons in contact with sick animals or
with contaminated materials should be protected and milk should be
pasteurized or boiled.
Control of FMD
in animals – Control requires close collaboration between
veterinary, health, and local authorities.
The highest risk
to European Union countries comes from providing food to animals
in these countries from legal and illegal imports of infected live
animals and from contaminated meat or dairy products
from infected countries. International travellers bringing back
food from endemic countries could also spread the
disease.
The FMD
virus can survive for long periods in a range of fresh,
partially cooked, cured, and smoked meats and in
inadequately pasteurized dairy products. Spread of the
virus is facilitated by the development of long distance animal
trading. Dense livestock populations may also enhance
local spread in the vicinity of an outbreak.
Awareness
of the disease among livestock owners is crucial, as are
good diagnostic facilities. Spread can take place on the
wind and mechanically by the movement of animals, people,
and vehicles that have been contaminated with the
virus. Thus the whole population has a role in
combating the disease. Restriction of non-essential
movement both into and out of affected farms and more
widely in the countryside is important.
Non-microbiological hazards which may be associated
with a major outbreak of FMD and the destruction of large numbers
of animals - Hazards to public health may also originate
from carcass disposal and use of disinfectants. Pyres for carcass
incineration are a distressing sight for the public, the smell is
unpleasant and they may put people at risk by creating traffic
hazards. However, the main risk to the public is likely to come
from smoke, causing breathing difficulties in people with
respiratory disease. Burning of carcasses also generates dioxins
and residual organic material, polyaromatic hydrocarbons from
burning creosote-treated wooden sleepers. During the control of
FMD outbreak in animals, the use of large quantities of
disinfectant may lead to contamination of ground water and
subsequent ill-health resulting from its consumption.
In addition,
people may suffer from certain mental health disorders,
resulting from the mass slaughtering and destruction of
animals carried out as part of the disease control measures and of
the economic losses associated with these.
| 