Traceback systems in most countries of Asia are not well developed, as indicated by responses to a questionnaire by veterinary officials in thirteen countries. Marking of animals for traceback is practised only in a limited number of countries in specific areas or zones and for specific purposes only. In Malaysia, traceback has been undertaken by marking farm code tattoos on pigs. This enables the identification of the farm of origin of pigs found to be infected by Nipah virus in sero-surveillance programmes. The origin of the foot and mouth disease (FMD) virus that surfaced in the Republic of Korea in March 2000 was investigated through several epidemiological studies of suspected sources of contamination such as imported hay, yellow sand, milk collection trucks and feed delivery trucks. None of these studies gave results that indicated the origin of the FMD virus. The origin of the FMD virus that was recorded in Japan in March 2000 was also investigated in epidemiological studies; in this case, imported wheat straw was incriminated as the most likely source of infection. Comparative studies of the pathogenicities of FMD (type O) viruses isolated in Taipei China, the Republic of Korea and Japan, suggest that these viruses might have originated as vaccine strains used in a third country.
During 2005, 764 children were brought to a large children's hospital in Ho Chi Minh City, Vietnam, with a diagnosis of hand, foot, and mouth disease. All enrolled children had specimens (vesicle fluid, stool, throat swab) collected for enterovirus isolation by cell culture. An enterovirus was isolated from 411 (53.8%) of the specimens: 173 (42.1%) isolates were identified as human enterovirus 71 (HEV71) and 214 (52.1%) as coxsackievirus A16. Of the identified HEV71 infections, 51 (29.5%) were complicated by acute neurologic disease and 3 (1.7%) were fatal. HEV71 was isolated throughout the year, with a period of higher prevalence in October-November. Phylogenetic analysis of 23 HEV71 isolates showed that during the first half of 2005, viruses belonging to 3 subgenogroups, C1, C4, and a previously undescribed subgenogroup, C5, cocirculated in southern Vietnam. In the second half of the year, viruses belonging to subgenogroup C5 predominated during a period of higher HEV71 activity.
Matched MeSH terms: Hand, Foot and Mouth Disease/transmission
Enterovirus A71 (EV-A71) causes hand-foot-and-mouth disease (HFMD), which may be complicated by fatal encephalomyelitis. Although fecal-oral or oral-oral routes are important in person-to-person transmission, how viral shedding and exposure may predispose individuals to infection remains unknown. We investigated person-to-person transmission by using a model of HFMD and encephalomyelitis based on EV-A71 oral infection of 2-week-old hamsters. Animals (index animals) infected with 104 50% cell culture infective doses of virus uniformly developed severe disease four days post-infection (dpi), whereas littermate contacts developed severe disease after six to seven days of exposure to index animals. Virus was detected in oral washes and feces at 3-4 dpi in index animals and at three to eight days after exposure to index animals in littermate contact animals. In a second experiment, non-littermate contact animals exposed for 8 or 12 h to index animals developed the disease six and four days post-exposure, respectively. Tissues from killed index and contact animals, studied by light microscopy, immunohistochemistry and in situ hybridization, exhibited mild inflammatory lesions and/or viral antigens/RNA in the squamous epithelia of the oral cavity, tongue, paws, skin, esophagus, gastric epithelium, salivary glands, lacrimal glands, central nervous system neurons, muscles (skeletal, cardiac and smooth muscles) and liver. Orally shed viruses were probably derived from infected oral mucosa and salivary glands, whereas fecal viruses may have derived from these sites as well as from esophageal and gastric epithelia. Asymptomatic seroconversion in exposed mother hamsters was demonstrated. Our hamster model should be useful in studying person-to-person EV-A71 transmission and how drugs and vaccines may interrupt transmission.
Matched MeSH terms: Hand, Foot and Mouth Disease/transmission*