RESUMEN
In February and March 2009, approximately 1,500 backyard pigs of variable age became sick, and approximately 700 of them died or were euthanized in the Lower Artibonite Valley and the Lower Plateau of the Republic of Haiti. The main clinical sign was posterior ataxia followed by paresis and/or paralysis on the second or third day of illness. No gross lesions were observed at postmortem examinations. The morbidity and mortality were approximately 60% and 40%, respectively. Diagnostic samples (whole blood, brain, tonsil, lymph nodes, spleen, and lung) were negative for Classical swine fever virus and African swine fever virus. Porcine teschovirus type 1 was detected by reverse transcription polymerase chain reactions in brain samples. Results of virus isolation, electron microscopy of virus particles, histopathological analysis on brain tissues, nucleic acid sequencing, and phylogenetic analysis of the viral isolate supported the diagnosis of teschovirus encephalomyelitis. The outbreak of the disease in Haiti is the first appearance of the severe form of teschovirus encephalomyelitis in the Americas. This disease poses a potential threat to the swine industries in other Caribbean countries, as well as to Central and North American countries.
Asunto(s)
Encefalomielitis/veterinaria , Infecciones por Picornaviridae/veterinaria , Enfermedades de los Porcinos/virología , Teschovirus/aislamiento & purificación , Animales , Anticuerpos Antivirales/análisis , Brotes de Enfermedades/veterinaria , Encefalomielitis/diagnóstico , Encefalomielitis/epidemiología , Encefalomielitis/virología , Haití/epidemiología , Histocitoquímica/veterinaria , Microscopía Electrónica/veterinaria , Filogenia , Infecciones por Picornaviridae/diagnóstico , Infecciones por Picornaviridae/epidemiología , Infecciones por Picornaviridae/virología , ARN Viral/química , ARN Viral/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/veterinaria , Análisis de Secuencia de ADN , Porcinos , Enfermedades de los Porcinos/epidemiología , Teschovirus/genética , Teschovirus/ultraestructuraRESUMEN
Classical swine fever (CSF) is an economically devastating disease of pigs. Instrumental to the control of CSF is a well-characterized assay that can deliver a rapid, accurate diagnosis prior to the onset of clinical signs. A real-time fluorogenic-probe hydrolysis (TaqMan) reverse transcription polymerase chain reaction (RT-PCR) for CSF was developed by the United States Department of Agriculture (USDA) at the Plum Island Animal Disease Center (CSF PIADC assay) and evaluated for analytical and diagnostic sensitivity and specificity. A well-characterized panel including Classical swine fever virus (CSFV), Bovine viral diarrhea virus (BVDV), and Border disease virus (BDV) isolates was utilized in initial feasibility and optimization studies. The assay was initially designed and validated for use on the ABI 7900HT using the Qiagen QuantiTect® Probe RT-PCR chemistry. However, demonstrating equivalency with multiple one-step RT-PCR chemistries and PCR platforms increased the versatility of the assay. Limit of detection experiments indicated that the Qiagen QuantiTect® Multiplex (NoROX) and the Invitrogen SuperScript® III RT-PCR kits were consistently the most sensitive one-step chemistries for use with the CSF PIADC primer/probe set. Analytical sensitivity of the CSF PIADC assay ranged from <1-2.95 log(10) TCID(50)/ml on both the ABI 7900HT and ABI 7500 platforms. The CSF PIADC assay had 100% diagnostic sensitivity and specificity when tested on a panel of 152 clinical samples from the Dominican Republic and Colombia. The ability to perform this newly developed assay in 96-well formats provides an increased level of versatility for use in CSF surveillance programs.