In today’s presentation we will cover information regarding the organism that causes Foot and Mouth Disease and its epidemiology. We will also talk about the economic impact the disease has had in the past and could have in the future. Additionally, we will talk about how it is transmitted, the species it affects (including humans), clinical and necropsy signs seen, and diagnosis and treatment of the disease. Finally, we will address prevention and control measures for the disease as well as actions to take if Foot and Mouth Disease is suspected.
Foot and mouth disease virus (FMDV) is in the family Picornaviridae, genus Aphthovirus. There are 7 immunologically distinct serotypes, which do not cross protect, and over 60 subtypes. New subtypes spontaneously develop, making effective vaccination difficult with new outbreaks. The FMDV is inactivated at a pH below 6.5 or above 11 (acidic or very basic conditions). The pH drop that occurs in muscle tissue post-mortem will inactivate the virus. It can survive in milk and milk products, frozen bone marrow, and lymph glands with stability increasing at lower temperatures. It can remain active on surfaces for days to weeks and survives drying if it is in serum. FMDV primarily affects cloven-hoofed domestic and wild animals such as cattle, sheep, goats, pigs and water buffalo. It can also affect hedgehogs, armadillos, nutrias, elephants, capybaras, rats and mice.
Prior to 1929, the United States had FMD in several states, generally due to the importation of infected animals or their products. This led to restrictions being imposed on importations of animals or their products from infected countries in 1929, many of which are still in effect today. An outbreak in Canada in 1953 was quickly controlled and Mexico was endemic with FMD until then as well. The North American continent has been free of FMD since 1953. Internationally, many countries have endemic FMD and some have had significant outbreaks that are highlighted here. Italy’s 1993 outbreak cost over $130 million, and the 1997 Taiwan outbreak cost roughly $15 billion. Great Britain had documented outbreaks in 1967-68 and 1981 in Hampshire. The recent outbreak in 2001, could cost the country £3.1 billion, by 2005. Diagram of United Kingdom.
FMD is considered by many to be the most economically devastating livestock disease virus in the world. This is largely due to the fact that it is highly transmissible, results in economic losses in animal production, and depopulation, the most effective means of control, would cost the producer and the government millions, even billions of dollars. The indirect effects of FMD would occur when countries around the world close their doors to our exports of beef, pork, mutton, dairy products, and live animals. This means the United States would have the potential to lose $3.1 billion in beef exports and $1.3 billion in pork exports each year. In a recent revenue impact analysis done of a FMD outbreak in the U.S., by Paarlberg and others (Potential revenue impact of an outbreak of foot-and-mouth disease in the United States. JAVMA ; 220,7:988-992), it was estimated that $14 billion would be lost in farm income. Livestock exports would drop $6.6 billion. Another indirect effect is that of consumer fear. Even though FMD is not a risk to humans, consumption of red meat and dairy products could be reduced and estimates include a 20% decline in consumer purchases, causing a loss to farm income of $20.8 billion.
FMD was found worldwide after WWII and the last outbreak in the United States was in 1929. The endemic areas include Asia, Africa, Middle East and parts of South America. Epidemics have occurred in Taiwan, South Korea, Japan, Mongolia, Britain, France, and the Netherlands. The Netherlands, North and Central America, Australia and New Zealand have been free of FMD for many years. The World Organization for Animal Health (formally known as the OIE- Office of International Epizootics) has a list of Member Countries that are FMD free countries where vaccination is not practiced. The map depicts those countries. Taken from the OIE website on June 28, 2004 http://www.oie.int/Cartes/world/a_Monde.htm For updates to that information, please access www.oie.int/eng/info/en_fmd#Resolution as outbreaks continue to occur and FMD-Free status changes.
It is important to understand that FMD has and is currently occurring in many countries around the world. This map is taken from the Food and Agriculture Organization of the United Nations giving us an accurate assessment of the worldwide impact as of June 29, 2004 from the FAO website http://fao.org/ag/againinfo/commissions/en/fmdmaps/maps2003/2003.gif
In a susceptible animal population, like the United States, morbidity can reach 100% but mortality is generally less than 1% from the disease. Younger animals and highly virulent strains of the virus can cause mortality to increase. Because of the economic impact of this disease, animals are generally destroyed to prevent further spread, but clinically could recover in time.
Transmission primarily occurs via respiratory aerosols and direct or indirect contact with infected animals. Aerosol transmission requires proper temperature and humidity. The FMD can survive for 1-2 days in the human respiratory tract, thus potentially spreading to animals. Contaminated animal parts such as meat, milk, bones, glands, and cheese that are fed to animals can also spread the disease. Contact with contaminated fomites such as boots, hands, or clothing can also be a source of infection. Other sources include artificial insemination, and contaminated biological, and hormone preparations. Peak transmission occurs when vesicles rupture.
Different animal species react to FMD in different ways. Sheep and goats are considered maintenance hosts in that they have mild signs which delay diagnosis and allow for aerosol, contact spread, and environmental contamination. Sheep can carry the virus in their pharyngeal tissue for 4-6 months. Pigs are amplifying hosts in that they concentrate the virus in their respiratory secretions and are much more infective via aerosol transmission. Pigs shed high levels of virus, but for a short time and are not long-term carriers. Cattle are indicator hosts because they are most often the first species to demonstrate clinical signs with more severe, rapidly progressing lesions. Cattle can carry the virus in their pharyngeal tissue for 6-24 months once exposed or vaccinated with FMD.
Humans normally do not acquire FMD, but the serotypes that have been isolated include O (most commonly), C and rarely A. Humans can act as a fomite and transmit FMD to other animal species. As mentioned previously, humans can harbor the FMD virus in their respiratory tract for 1-2 days. Also, if their boots, clothing or vehicles become contaminated they can spread the virus to susceptible animals. Also, if humans ingest unprocessed milk or dairy products from infected animals, they are at risk for contracting infection. This too has very low incidence.
The incubation period for FMD is 2 to 12 days and animals that are in contact with infected animals will generally develop signs in 3 to 5 days. Fever and vesicles (blisters) on the feet, mouth, nares, muzzle and teats are the characteristic lesions of FMD. These will eventually progress to erosions which cause the affected animal to have clinical signs associated with the lesioned area. Abortion can occur in adults and death in young animals without any other clinical signs. Animals generally recover in two weeks but secondary infections can lead to longer recovery time. The photo depicts oral erosions on the tongue and lips of a cow with FMD.
Clinical signs in cattle include oral lesions such as vesicles on the tongue, dental pad, gums, soft palate, nostrils or muzzle. This will lead to excess salivation, drooling, and serous nasal discharge. The photo depicts a cow with excessive salivation and drooling due to oral lesions. Photo courtesy of the Gray Book.
Teat lesions can occur and cause a decrease in milk production. Hoof lesions in the interdigital space and on the coronary band are also common leading to lameness and a reluctance to move. Photo depicts ruptured vesicles at the end of a bovine teat, from the Gray Book.
Pigs have more severe hoof lesions than cattle with vesicles on the coronary band, heel and interdigital space. Vesicles are often seen on the snout but oral lesions are not as common or less severe than in cattle if they do occur. Drooling is rare in pigs because of this. Top photo depicts severe hoof lesions on a pig with FMD (from USDA http://www.usda.gov/oc/photo/01cs0008.htm) and the lower picture is of lame pigs due to their hoof lesions (Gray Book).
Since sheep and goats are referred to as a maintenance host, fever, oral lesions and lameness occur but are very mild and sometimes are not detected. This makes it difficult to diagnose and prevent the spread of disease to other species.
Clinically, all vesicular diseases produce a fever with vesicles that progress to erosions in the mouth, nares, muzzle, teats and feet. Vesicular diseases are clinically indistinguishable from one-another, especially in swine as this chart shows, and diagnosis can only be made through virus isolation initially. Any disease with vesicles and fever should be reported to a state or federal veterinarian.
It is important to remember that FMD is clinically indistinguishable from other vesicular diseases, especially in swine, so if suspicious lesions are seen, authorities should be notified immediately. FMD lesions consist of single or multiple vesicles from 2mm to 10cm in size in various stages of development. They start out as a small white area and progress to a fluid filled blister. Once they rupture, they leave a red eroded area that is covered by a gray fibrinous coating, that eventually is replaced with new epithelium and a demarcation line. Dry lesions are common in the pig oral cavity and occur when the fluid escapes through the epidermis and appear more necrotic than vesicular. Pigs can lose their hoof in severe cases of coronary band lesions. Yellow or gray streaking leaves “Tiger heart” lesions (photo) on the myocardium caused by degeneration and necrosis. The rumen pillars may also have vesicular lesions. The photo depicts a heart with a pale area in the myocardium that is an area necrosis from the USAHA Gray Book.
Differential diagnosis in swine includes vesicular stomatitis, swine vesicular disease, vesicular exanthema in swine, foot rot, chemical and thermal burns. In cattle, oral lesions later in the disease can resemble rinderpest, infectious bovine rhinopneumonitis (IBR), bovine virus diarrhea (BVD), malignant catarrhal fever (MCF), and bluetongue. The photo depicts an unruptured vesicle on the snout of a pig caused by FMD (Gray Book), but remember, it is clinically indistinguishable from swine vesicular disease, vesicular stomatitis and vesicular exanthema of swine.
Before collecting or sending any samples from animals with a suspected foreign animal disease, the proper authorities should be contacted. Samples should only be sent under secure conditions and to authorized laboratories to prevent the spread of the disease.
Clinically, vesicular diseases are indistinguishable from one another. However, if salivation and lameness are present with vesicular lesions, FMD should be considered a differential. Fever is often the first clinical sign, so that should prompt you to examine the mouth and feet for early lesions. Tranquilization may be necessary for a thorough exam as vesicles may be hard to identify initially. The photo depicts oral lesions on the tongue of a pig (Gray Book), but these are clinically indistinguishable from swine vesicular disease, vesicular stomatitis and vesicular exanthema of swine.
For initial diagnosis of an outbreak in a region, virus isolation and identification must be performed on vesicular fluid or the epithelium covering vesicles. Following that, antigen or nucleic acid detection can be used, as can complement fixation. ELISA and virus neutralization tests can detect antibody in serum. Contact authorities if you are suspicious of a vesicular disease. Samples must be properly obtained, securely packaged, and sent to authorized laboratories for diagnosis. Call before sampling as a Foreign Animal Disease Diagnostician (FADD) is trained to handle exotic diseases.
Currently there is no treatment for FMD as it is a virus. Supportive care should be provided to those animals afflicted with the disease, but due to the grave economic impact, animals will be quarantined, euthanized, and disposed of once they are found infected. Vaccines are available for use in some countries and this will be discussed under prevention and control.
Most human infection reports ended when mass vaccination eradicated the disease in animals in Europe and other countries. It is a zoonotic concern, but one of very low incidence. Only 40 cases of human FMD have been reported since 1921. Humans with FMD generally have an incubation period of 2 to 6 days prior to clinical disease manifestation. Initially onset includes a fever, mild headache, malaise, oral dryness, muscle pain, and a tingling, burning sensation of fingers, palms, and feet prior to vesicle formation.
Aphthae, or vesicles, may be pin head to 2cm in diameter and fluid filled initially. Vesicles or blisters in the mouth, generally on the tongue and palate, are the most painful and interfere in eating, drinking, and talking. Diarrhea often accompanies these lesions. Most blisters dry up in 2-3 days and the skin sloughs and heals by first intention. Recovery usually occurs within a week of the last blister appearance.
Clinically this disease resembles Coxsackie A group viruses, which includes hand, foot, and mouth disease and herpangina, Herpes simplex virus, which includes primary herpetic gingivostomatitis, and sometimes vesicular stomatitis. To definitively diagnose FMD in humans, the virus must be isolated and identified by the identification of specific antibodies after infection, much in the same way it is diagnosed in animals. As this is a virus, treatment would consist of supportive care, such as parenteral nutrition, intravenous fluids, antibiotics if there is a risk of secondary infection. Photo depicts a child with Hand, Foot, and Mouth disease which is NOT the same as FMD but resembles it. Note the lesions on the palms. Photo accessed at www.info.gov.hk/dh/diseases/CD/photoweb/Handfootandmouthdisease-1.jpg
FMD infection in humans is not considered a public health concern. Since 1921, there have only been 40 human cases that were isolated and typed on three continents (Europe, Africa, South America). There were three subtypes, with O predominating, also C and rarely A.
The USDA has upgraded the safeguarding measures in place to prevent introduction of FMDV into the U.S. The USDA APHIS has strict import restrictions in place to prohibit importations of live ruminants, swine, and their products from FMD-affected countries. Government officials at ports of entry continue to monitor travelers and their belongings that have returned from an FMD area. There are 450 foreign animal disease diagnosticians (FADD) employed to investigate suspicious lesions and other unusual symptoms that private veterinary practitioners alert them to. Several states have also been involved in training exercises regarding actions to take if FMD is introduced. Additionally, APHIS has a federal plan in place should it occur on U.S. soil. Producers should implement and follow strict, complete biosecurity protocols on U.S. livestock production facilities as their best means of prevention.
Due to the economically devastating nature of this disease, state and federal veterinarians should be notified immediately of any suspicious cases of FMD. While waiting for the authorities or a confirmed diagnosis, all suspect animals should be quarantined. Photo depicts a quarantined farm that was FMD positive in the UK in 2001. Photo courtesy of Katie Steneroden, DVM at ISU.
Should FMD be confirmed by diagnosis, depopulation may need to occur. Depopulation protocols include plans for the infected premises, contact exposed premises, and contiguous premises. Proper destruction of all exposed cadavers, litter and animal products are required. Photo depicts the burning of carcasses that were FMD positive.
Proper disinfection of all contact premises and infected materials is also required. Preparing disinfectants for the farm entrance, vehicles, and people is imperative in preventing the spread. Some of the effective disinfectants include: 2% sodium hydroxide (lye), 4% sodium carbonate (soda ash), 5.25% sodium hypochlorite (household bleach), and 0.2% citric acid. FMD is resistant to various compounds such as iodophores, quaternary ammonium, hypochlorite and phenol. Make sure the areas are free of organic matter for any of the disinfectants to be effective. Photo depicts the entrance to a farm that was FMD positive in the UK in 2001. Note the straw at the gate and containers of disinfectant for travelers to use.
FMD vaccines are killed, serotype specific preparations and available to members (U.S., Mexico, Canada) of the Vaccine Bank. The North American Foot-and-Mouth Vaccine Bank (NAVB) is housed at the USDA Foreign Animal Disease Diagnostic Laboratory (FADDL) at Plum Island Animal Disease Center- located 1½ miles off the coast of Long Island, New York. The scientists at this biosafety-3 level lab monitor outbreaks worldwide to stock the NAVB with the FMD antigens from the most active serotype or strains of the virus. FMD has 7 different serotypes and more than 60 subtypes and there is no universal vaccine available. It is essential to isolate the virus and identify the serotype to select the correct vaccine. A decision to vaccinate during an outbreak would be made by collaboration of USDA, state, and local officials.
With this technology, why don’t we vaccinate for FMD? There is no need to vaccinate against a disease that animals have not had in this country since 1929. However, we may need to do so during an outbreak to contain it. There are huge implications to vaccinating animals. First, annual re-vaccination would be required to maintain immunity and this is very costly and time consuming. It would be necessary to vaccinate against all 7 serotypes of the virus. The FMD vaccine does not protect against getting the infection, it just lessens the clinical manifestations. So if a vaccinated animal came in contact with the virus, it could harbor it for months or years in its respiratory tract and shed it to others. This false sense of security of “vaccinated animals” could do more harm than good. Finally, if the U.S. does vaccinate, our international trade status would be in jeopardy as we couldn’t claim FMD-free status. To earn FMD-free status, the OIE health code requires a 3-month waiting period after they slaughter their last positive animal, given ongoing surveillance through serological testing has occurred throughout the disease monitoring process.
Foot and MouthDiseaseFMD, Aftosa
Center for Food Security anOverview• Organism• Economic Impact• Epidemiology• Transmission• Clinical Signs• Diagnosis and Treatment• Prevention and Control• Actions to take
Center for Food Security anHistory• 1929: Last case in U.S.• 1953: Last cases inCanada and Mexico• 1993: Italy• 1997: Taiwan• 2001: United Kingdom− Other outbreaks in1967-68 and 1981
Center for Food Security anEconomic Impact• Direct costs− Economic losses tofarmers andproducers− Eradication costs− Millions to billions ofdollars lostEconomicallyDevastating!!• Indirect costs− Exports shut down− $3.1 billion in beef− $1.3 billion in pork− $14 billion in lostfarm income− $6.6 billion inlivestock exports− Consumer fear
Center for Food Security anGeographic Distribution
Center for Food Security anFoot and Mouth DiseaseDistribution 2003
Center for Food Security anMorbidity/ Mortality• Morbidity 100% in susceptible animalpopulation− United States, Canada, Mexico, others• Mortality less than 1%− Higher in young animals and highlyvirulent virus strains− Animals generally destroyed to preventspread
Center for Food Security anAnimal Transmission• Respiratory aerosols− Proper temperature and humidity− Survives 1-2 days in human respiratorytract• Direct contact− Ingestion of infected animal parts− AI, biologicals, hormones• Indirect contact via fomites
Center for Food Security anAnimal TransmissionSpecies Host CarrierSheepGoatsMaintenance Pharyngealtissue 4-6monthsPigs Amplifier NoCattle Indicator Pharyngealtissue 6-24months
Center for Food Security anHuman Transmission• Very rarely develop mild clinical signs• Type O, C, rarely A• Act as a transmitter to animals− Harbor virus in respiratory tractfor 1-2 days− Contaminated boots, clothing, vehicles− Spread to susceptible animals• Ingestion of unprocessed milk or dairyproducts from infected animals
Center for Food Security anClinical Signs• Incubation period: 2-12 days• Fever and vesicles− Feet, mouth, naresmuzzle, teats− Progress to erosions• Abortion• Death in young animals• Recover in two weeks unlesssecondary infections arise
Center for Food Security anClinical Signs in Cattle• Oral lesions− Vesicles on tongue,dental pad, gums,soft palate, nostrils,muzzle− Excess salivation,drooling, serousnasal discharge
Center for Food Security anClinical Signs in Cattle• Teat lesions− Decreased milkproduction• Hoof lesions− Interdigital space− Coronary band− Lameness− Reluctant to move
Center for Food Security anClinical Signs in Pigs• Hoof lesions− More severe than in cattle− Coronary band, heel,interdigital space− Lameness• Snout vesicles• Oral vesiclesless common− Drooling is rare
Center for Food Security anClinical Signs inSheep and Goats• Mild, if any, signs− Fever− Oral lesions− Lameness• Makes diagnosis andprevention of spreaddifficultFredWard,USDALarryRana,USDA
Center for Food Security anFoot & MouthDiseaseVesicularStomatitisSwine VesicularDiseaseVesicularExanthema ofSwineClinicalSigns bySpeciesAll vesicular diseases produce a fever with vesicles that progress toerosions in the mouth, nares, muzzle, teats, and feetCattleOral & hoof lesions,salivation, drooling,lameness, abortions,death in younganimals, "panters";DiseaseIndicatorsVesicles in oralcavity, mammaryglands, coronarybands, interdigitalspaceNot affected Not affectedPigsSevere hoof lesions,hoof sloughing, snoutvesicles, less severeoral lesions:Amplifying HostsSame as cattleSevere signs inanimals housed onconcrete; lameness,salivation,neurological signs,younger moresevereDeeper lesions withgranulation tissueformation on the feetSheep &GoatsMild signs if any;Maintenance HostsRarely show signs Not affected Not affectedHorses,Donkeys,MulesNot affectedMost severe withoral and coronaryband vesicles,drooling, rubmouths on objects,lamenessNot affected Not affected
Center for Food Security anPost Mortem Lesions• Clinically indistinguishable from othervesicular diseases, especially swine• Single or multiple vesicles• Various stages ofdevelopment− White area, 2mm-10cm− Fluid filled blister− Red erosion, fibrin coating• Dry lesions• Tiger heart
Center for Food Security anDifferential Diagnosis• In swine− Vesicular stomatitis− Swine vesicular disease− Vesicular exanthemaof swine− Foot rot− Chemical and thermal burns• In cattle− Rinderpest, IBR, BVD, MCF, Bluetongue
Center for Food Security anSampling• Before collecting or sending anysamples, the proper authoritiesshould be contacted• Samples should only be sent undersecure conditions and to authorizedlaboratories to prevent the spread ofthe disease
Center for Food Security anClinical Diagnosis• Clinically vesicular diseases areindistinguishable• Salivation, lameness with vesiclesrequires further testing• Tranquilization may be necessary
Center for Food Security anDiagnosis• Laboratory Tests− Initial diagnosis Virus isolation and identification− Antigen or nucleic acid detection− Complement fixation− ELISA and virus neutralization• Notify authorities and wait forinstructions before collecting samples
Center for Food Security anTreatment• No treatment available• Supportive care to those afflicted• U.S. outbreak could result in− Quarantine− Euthanization− Disposal• Vaccine available− Ramifications are many and discussed later
Center for Food Security anHuman Clinical Signs• Very low incidence of human disease− 40 cases since 1921− Most reports ended when FMD waseradicated in Europe• Incubation period: 2-6 days• Clinical signs− Mild headache, malaise, fever− Tingling, burning sensation of fingers,palms, feet prior to vesicle formation
Center for Food Security anHuman Clinical Signs• Vesicles 2 mm to 2 cm in diameter− Fluid-filled• Oral blisters on tongue, palate− Painful− Interfere in eating, drinking, talking− Diarrhea• Vesicles dry up in 2-3 days• Recover within a week of last blisterappearing
Center for Food Security anDiagnosis and Treatment• Clinically FMD in humans resembles− Coxsackie A group viruses Hand, foot and mouth disease Herpangina− Herpes simplex virus Primary herpetic gingivostomatitis− Vesicular stomatitis• Virus isolation or antibody identificationrequired for diagnosis• Treatment is supportive careHand, Foot &Mouth Disease
Center for Food Security anPublic Health Significance• FMD in humans is not a publichealth concern• 40 cases since 1921 documentedin humans− Europe, Africa, South America
Center for Food Security anPrevention• USDA APHIS: Strict import restrictions− Prohibit live ruminants, swine, and theirproducts from FMD-affected countries− Monitor travelers and belongings atports of entry• 450 FADD to investigate suspicious lesions• State planning/training exercises• Biosecurity protocols for livestock facilities
Center for Food Security anRecommended Actions• Notification of Authorities− Federal:Area Veterinarian in Charge (AVIC)www.aphis.usda.gov/vs/area_offices.htm− State veterinarianwww.aphis.usda.gov/vs/sregs/official.html• Quarantine
Center for Food Security anRecommended Actions• Confirmatorydiagnosis• Depopulation mayoccur− Proper destructionof exposedcadavers, litter,animal products
Center for Food Security anDisinfection• Effective solutions include− 2% sodium hydroxide (lye)− 4% sodium carbonate (soda ash)− 5.25% sodiumhypochlorite(household bleach)− 0.2% citric acid• Areas must be free of organic matter
Center for Food Security anVaccination• Killed vaccine, serotype specific• North American Foot-and-MouthVaccine Bank− Plum Island, NY• Monitor disease outbreaks worldwideand stock active serotypes and strains• It is essential to isolate virus andidentify the serotype to select thecorrect vaccine
Center for Food Security anVaccination• U.S. has no need to vaccinate− Have not had animals affected since 1929• May be used to control an outbreak• Huge implications if we do vaccinate− Annual re-vaccination required Costly, time consuming− Does not protect against infection, justclinical signs Spread infection to other animals− International trade status harmed
Center for Food Security anResources• World Organization for Animal Health(OIE) website− www.oie.int• USDA APHIS Veterinary Services− www.aphis.usda.gov/vs• 1-866-SAFGUARD is a toll-freehotline with recorded messages forinternational travelers
AcknowledgmentsDevelopment of thispresentation was fundedby a grant from theCenters for Disease Controland Prevention to theCenter for Food Securityand Public Health at IowaState University.