미국 주류학계의 구제역에 대한 입장을 잘 정리한 자료입니다.

마지막 인간에게 미치는 영향(공중보건, Public Health)을 기술한 부분을 보면… 구제역이 인수공통전염병(zoonosis)라는 사실 자체는 부정하지 않고… 인체에 전염된 사례가 40건 정도 있긴 하지만 공중보건 상 고려해야 할 정도는 아니라는 입장을 개진하고 있습니다.

“구제역은 공중보건 상 문제가 될 것으로 고려되지 않는다. 인간에게 구제역 바이러스가 감염된 것은 1921년 후 40건 정도가 진단될 정도로 아주 드물다. (감염된 인간에서는) 병변 부위에 수포가 생기고, 인플루엔자와 유사한 증상이 나타날 수 있다. 이 질병은 일반적으로 약하게 증상이 나타나고, 바이러스가 인체에서 생존하는 기간이 짧으며, 인간대 인간 전염이 이루어지지 않아 감염이 제한적이다.(Foot-and-mouth disease is not considered to be a public health problem. FMDV infections in humans are very rare, with approximately 40 cases diagnosed since 1921. Vesicular lesions and influenza-like symptoms can be seen; the disease is generally mild, short-lived and self-limiting.)”

==================

Foot and Mouth Disease

Fiebre Aftosa

Last Updated: September 24, 2007

Importance
Foot-and-mouth disease (FMD) is a highly contagious viral disease that primarily affects cloven-hooved livestock and wildlife. Although adult animals generally recover, the morbidity rate is very high in naïve populations, and significant pain and distress occur in some species. Sequelae may include decreased milk yield, permanent hoof damage and chronic mastitis. High mortality rates can be seen in young animals. Although foot-and-mouth disease was once found worldwide, it has been eradicated from some regions including North America and most of Europe. Where it is endemic, this disease is a major constraint to the international livestock trade. Unless strict precautions are followed, FMD can be readily re-introduced into disease-free livestock. Once this occurs, the disease can spread rapidly through a region, particularly if detection is delayed. Outbreaks can severely disrupt livestock production, result in embargoes by trade partners, and require significant resources to control. Direct and indirect economic losses equivalent to several billion US dollars are not uncommon. Since 1997, a PanAsia lineage virus has caused a series of outbreaks in Asia, Africa, the Middle East and Europe. Some outbreaks, particularly those in Taiwan and the United Kingdom, have been devastating.

Etiology
The foot-and-mouth disease virus (FMDV) is a member of the genus Aphthovirus in the family Picornaviridae. There are seven immunologically distinct serotypes – O, A, C, SAT 1, SAT 2, SAT 3 and Asia 1 – and over 60 strains within these serotypes. New strains occasionally develop spontaneously.
FMDV serotypes and strains vary within each geographic region. Serotype O is the most common serotype worldwide. This serotype is responsible for a pan-Asian epidemic that began in 1990 and has affected many countries throughout the world. Other serotypes also cause serious outbreaks. Immunity to one serotype does not provide any cross-protection to other serotypes. Cross-protection against other strains varies with their antigenic similarity.

Transmission
FMDV can be found in all secretions and excretions from acutely infected animals, including expired air, saliva, milk, urine, feces and semen. Pigs, in particular, produce large quantities of aerosolized virus. Animals can shed FMDV for up to four days before the onset of symptoms. This virus is also found in large quantities in vesicle fluid, and peak transmission usually occurs when vesicles rupture. Transmission can occur by direct or indirect contact with infected animals and contaminated fomites; routes of spread include inhalation of aerosolized virus, ingestion of contaminated feed, and entry of the virus through skin abrasions or mucous membranes. The importance of each of these routes varies with the species. For example, pigs are less susceptible to aerosolized virus than cattle or sheep. Sheep may have less obvious symptoms than other species, and have been important in disseminating the virus in some outbreaks. Sexual transmission could be a significant route of spread for the SAT type viruses in African buffalo populations.
Some animals carry FMDV for prolonged periods after recovering from acute disease. Animals with natural or vaccine-induced immunity can also become carriers if they are later exposed to virus; these animals can remain asymptomatic.

FMDV can persist for up to nine months in sheep and up to four months in goats. Most cattle carry this virus for six months or less, but some animals remain persistently infected for up to 3.5 years. Individual African buffalo have been shown to be carriers for at least five years, and the virus can persist in a herd of African buffalo for at least 24 years. Llamas do not become carriers. A single study suggested that pigs may become carriers, but many other studies have found that this species cleared the infection within 3 to 4 weeks. In carriers, FMDV is found only in the esophageal-pharyngeal fluid.

The amount of virus is small, and it may be found only intermittently. Carriers might be able to transmit FMDV to other animals if they come in close contact; the importance of this route of transmission is controversial. Unequivocal evidence for transmission from carriers has been reported only from Africa, where African buffalo can spread the disease to cattle. With the exception of African buffalo, wildlife seems to be infected by contact with domesticated animals; FMDV disappears from the wildlife populations when outbreaks in livestock are controlled. Persistent infections have been reported in some experimentally infected wildlife including fallow (Dama dama) and sika deer (Cervus nippon) and kudu (Tragelaphus strepsiceros), and occasionally in red deer (Cervus elaphus). Deer could carry FMDV for up to 11 weeks.

FMDV can be transmitted on fomites including vehicles, as well as mechanically by animals and other living vectors. Airborne transmission can occur under favorable climatic conditions. FMDV is thought to have been transmitted via aerosols from Brittany to Jersey (approximately 30 miles or 48 km) and for approximately 70 miles (113 km) from Jersey to the Isle of Wight. There is limited information on the survival of FMDV in the environment, but most studies suggest that it remains viable, on average, for three months or less. In very cold climates, survival up to six months may be possible. Virus stability increases at lower temperatures; in cell culture medium at 4°C (39°F), this virus can remain viable for up to a year. It was reported to survive on bran and hay for more than three months in a laboratory. It can also remain viable for approximately two months on wool at 4°C, with significantly decreased survival when the temperature increases to 18°C (64°F), and for 2 to 3 months in bovine feces. Organic material protects the virus from drying, and enhances its survival on fomites. Virus survival is also enhanced when FMDV is protected from sunlight. FMDV is inactivated at pH below 6.5 or above 11. This virus can persist in meat and other animal products when the pH remains above 6.0,but it is inactivated by acidification of muscles during rigor mortis. It can survive for long periods in chilled or frozen lymph nodes or bone marrow.
In humans, FMDV may be carried in the nasal passages for a period of time. In one study, this virus was detected in the nasal passages of one of eight people 28 hours after exposure to infected animals, and from none of the eight at 48 hours. More recent studies have found that FMDV is not transmitted by people when personal hygiene and biosecurity protocols are followed, and suggest that nasal carriage of the virus may be unimportant. The discrepancy between these studies remains to be resolved.

Incubation Period
In cattle, the incubation period varies from two to 14 days, depending on the dose of the virus and route of infection. In pigs, the incubation period is usually two days or more, but can be as short as 18-24 hours. The incubation period in sheep is usually 3 to 8 days. Incubation periods as short as 24 hours and as long as 12 days have been reported in this species after experimental infection.

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. Some countries maintain individual vaccine banks. There are also three international vaccine banks: the North American FMD Vaccine Bank (for Canada, the U.S. and Mexico), the E.U. Vaccine Bank (for all EU countries) and the International Vaccine Bank (for a variety of countries including Australia, New Zealand and some European nations).
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.
Transmission of FMDV from wildlife in southern Africa is controlled by separating wildlife from domesticated livestock with fences, and by vaccination of livestock.

Public Health
Foot-and-mouth disease is not considered to be a public health problem. FMDV infections in humans are very rare, with approximately 40 cases diagnosed since 1921. Vesicular lesions and influenza-like symptoms can be seen; the disease is generally mild, short-lived and self-limiting.