I attended a clinical case few days ago. It was supposed to be our avian round but we received an emergency call from a vet whom asked our lecturer to look on the case at the quarantine center Rantau Panjang.
I was thrilled to find out that it was about FMD! So far I have never seen FMD case alive and today was our gold pot.
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On the farm..
**Malaysia is one of the FMD countries
Foot-and-mouth disease (FMD) is a severe, highly communicable and economically devastating viral disease of cattle and swine. It also affects sheep, goats, deer, and other clovenhoof ruminants. Many affected animals recover, but the disease leaves them debilitated. FMD causes severe losses in the production of meat and milk. The disease does not effect food safety or humans. Other susceptible species include hedgehogs, nutria, rats, armadillos, elephants, capybaras, and mice. FMD is not recognized as a zoonotic disease.
The disease is characterized by fever and blisterlike lesions followed by erosions on the tongue and lips, in the mouth, on the teats, and between the hooves. Because it spreads widely and rapidly and because it has grave economic as well as clinical consequences, FMD is one of the animal diseases that livestock owner dread most.
Cattle is the most susceptible to FMD
Etiology
The FMD disease is caused by a virus. The FMD virus (FMDv) is a member of the genus Apthovirus in the family Picornaviridae. The virion is a small (23-nm) single-stranded RNA virus. The virus survives in lymph nodes and bone marrow at neutral pH, but destroyed in muscle when in pH<6.0 i.e. after rigor mortis. The virus can persist in contaminated fodder and the environment for up to one month, depending on the temperature and pH conditions. There are seven serotypes of FMD virus, O, A, C, Asia 1, SAT 1, SAT 2 and SAT 3, distributed throughout the world and many subtypes of the FMD virus. Immunity to one type does not protect an animal against other types.
Serotype O is the most widely distributed, being endemic in many South American, African and Asian countries, affecting all susceptible species. Certain strains of serotype O appear particularly adapted to a particular host species. Within serotype O there are groups of strains (genotypes) that are associated with particular areas of distribution, and species preference.
FMDV can infect most or all members of the order Artiodactyla (cloven-hooved mammals), as well as a few species in other orders. Each species varies in its susceptibility to infection and clinical disease, as well as its ability to transmit the virus to other animals. Livestock susceptible to FMD include cattle, pigs, sheep, goats, water buffalo and reindeer. Lllamas, alpacas and camels can be infected experimentally, but do not appear to be very susceptible. FMDV can also infect at least 70 species of wild animals including African buffalo (Syncerus caffer), bison (Bison spp.), elk, moose, chamois, giraffes, wildebeest, blackbuck, warthogs, kudu, impala, and several species of deer, antelopes and gazelles. Susceptible non clovenhooved species include hedgehogs, armadillos, kangaroos, nutrias, capybaras, guinea pigs, rats and mice. Infections have been reported in African and Asian elephants in zoos; however, African elephants are not considered susceptible to FMD under natural conditions in southern Africa.
On most continents, cattle are usually the most important maintenance hosts for FMDV, but some virus strains are primarily found in pigs, sheep or goats. Cattle and African buffalo are the usual maintenance hosts for FMDV in Africa; African buffalo are currently thought to carry only the SAT serotype. With this exception, wildlife hosts do not seem to be able to maintain FMD viruses, and are usually infected by contact with domesticated livestock. Early reports suggested that transmission also occurred between cattle and European hedgehogs, but there is no evidence that this species has helped to propagate FMDV in the last 40 years.
Transmission
FMD viruses can be spread by animals, people, or materials that bring the virus into physical contact with susceptible animals. An outbreak can occur when:
- Animals carrying the virus are introduced into susceptible herds.
- Contaminated facilities are used to hold susceptible animals.
- Contaminated vehicles are used to move susceptible animals.
- Raw or improperly cooked garbage containing infected meat or animal products is fed to susceptible animals.
- People wearing contaminated clothes or footwear,or using contaminated equipment, pass the virus to susceptible animals.
- Susceptible animals are exposed to materials such as hay, feedstuffs, hides, or biologics contaminated with the virus.
- Susceptible animals drink common source contaminated water.
- A susceptible animal is inseminated by semen from an infected animal
Vesicles (blisters) followed by erosions in the mouth or on the feet and the resulting excessive salivation or lameness are the best known signs of the disease. Often blisters may not be observed because they easily rupture, leading to erosions. These signs may appear in affected animals during an FMD outbreak:
- Marked rise in body temperature for 2 to 3 days.
- Vesicles that rupture and discharge clear or cloudy fluid, leaving raw, eroded areas surrounded by ragged fragments of loose tissue.
- Production of sticky, foamy, stringy saliva.
- Reduced consumption of feed due to painful tongue and mouth lesions.
- Lameness with reluctance to move.
- Abortions.
- Low milk production (dairy cows).
- Myocarditis (inflammation of the muscular walls of the heart) and death, especially in newborn animals. Animals do not normally regain lost weight for many months. Recovered cows seldom produce milk at their former rates, and conception rates may be low.
Hypersalivation
Blister on the coronary band of the hoof
Blister on the tongue and mouth
Diagnosis
The symptoms of FMD vary with the species, but vesicles and erosions in the oral cavity or on the feet, teats or other areas are suggestive. In cattle, suspicion should be raised by simultaneous salivation and lameness, particularly when a vesicular lesion has been seen or is suspected to exist. Profuse salivation is uncommon in pigs or sheep, where lameness is more typical. Suspect or febrile animals should be examined closely for lesions. When sudden death is observed in young cloven-hooved livestock, older animals should also be examined; young animals that die of heart disease may not have vesicular lesions. Tranquilization may be necessary for a thorough examination as vesicles are painful and may be difficult to see. Laboratory confirmation is necessary, as all vesicular diseases have almost identical clinical signs.
FMD cannot be distinguished clinically from other vesicular diseases including vesicular stomatitis, swine vesicular disease and vesicular exanthema. In domesticated animals, the symptoms may also resemble foot rot, traumatic stomatitis, and chemical and thermal burns. In cattle, oral lesions can resemble rinderpest, infectious
bovine rhinotracheitis, bovine viral diarrhea, malignant catarrhal fever and epizootic hemorrhagic disease. In sheep, the lesions can be confused with bluetongue, contagious ecthyma, and lip and leg ulceration.
Samples to collect
In acute disease, the preferred sample for virus detection is epithelium from unruptured or freshly ruptured vesicles, or vesicular fluid. Sedation is generally advisable before these samples are collected. FMDV is extremely sensitive to low pH, and virus isolation is dependent on good buffering; epithelial samples should be shipped in a transport medium, and kept refrigerated or on ice. If vesicles are not available, blood (serum) and esophageal-pharyngeal fluid samples can be collected for virus isolation or RT-PCR. Esophageal–pharyngeal fluids are taken by probang cup from ruminants, or as throat swabs from pigs, and are shipped in transport medium. These samples should be refrigerated or frozen immediately after collection. Vesicles are the preferred sample from animals that died of heart failure, but myocardial tissue or blood can be collected if vesicles are not present. FMDV may also be found in milk, other secretions and excretions, and other organs. Serum should be collected for serology. In animals suspected to be carriers, esophagealpharyngeal fluids should be collected.
Probang cup
Treatment
FMD has no treatment
Prevention and control
FMD outbreaks are usually controlled by quarantines and movement restrictions, euthanasia of affected and incontact animals, and cleansing and disinfection of affected premises, equipment and vehicles. Effective disinfectants include sodium hydroxide (2%), sodium carbonate (4%), citric acid (0.2%) and Virkon-S®. Iodophores, quaternary ammonium compounds, hypochlorite and phenols are less effective, especially in the presence of organic matter. Infected carcasses must be disposed of safely by incineration, rendering, burial or other techniques. Milk from infected cows can be inactivated by heating to 100°C (212°F) for more than 20 minutes. Slurry can be heated to 67°C (153°F) for three minutes. Rodents and other vectors may be killed to prevent them from mechanically disseminating the virus. Good biosecurity measures should be practiced on
uninfected farms to prevent entry of the virus.
Vaccination may be used to reduce the spread of FMDV or protect specific animals (e.g. those in zoological collections) during some outbreaks. The decision to use vaccination is complex, and varies with the scientific, economic, political and societal factors specific to the outbreak. Vaccines are also used in endemic regions to protect animals from clinical disease. FMDV vaccines must closely match the serotype and strain of the infecting strain. Vaccination with one serotype does not protect the animal against other serotypes, and may not protect the animal completely or at all from other strains of the same serotype. Currently, there is no universal FMD vaccine. Vaccine banks contain a wide variety of strains, particularly those judged to be the greatest threat of introduction, for use in an outbreak.
Humans are thought to carry FMDV mechanically for a short period of time, based on a study that found this
virus in the nasal passages of one of eight people 28 hours after they had been exposed to infected animals and none of the eight people at 48 hours. People who have been exposed to infected animals should avoid susceptible livestock for a designated period, usually a few days to a week. Some recent studies suggest that extended avoidance periods may not be necessary if good biosecurity practices, including effective personal hygiene protocols (showering or washing hands, and changing clothing), are followed. The discrepancy between these studies remains to be resolved, and government authorities should be consulted for the most recent waiting period recommendations.
Sources: 'Van Nostrand’s Scientific Encyclopedia. — 10th ed.- edited by Glenn D.Considine, Published by John Wiley & Sons, Inc., Hoboken, New Jersey, USA, 2008, p. 2057-2059. Adapted and illustrated to be posted by Leopoldo Costa.
FMD: the center for food security and public health, Iowa State of university Fiebre Aftosa
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