Attempts to transmit porcine reproductive and respiratory syndrome virus by aerosols under controlled field conditions.

An experimental infection with porcine reproductive and respiratory syndrome virus (PRRSV) was established in 150 five-month-old pigs housed in a fan-ventilated finishing facility, the infected barn. To determine whether air exhausted from the wall fans contained infectious PRRSV, a trailer containing 10 four-week-old PRRSV-naive sentinel pigs was placed 10 m from the building from day 3 after the 150 pigs were infected until day 10. To connect the two airspaces, one end of an opaque plastic tube, 15 m in length and 5 cm in diameter, was fastened to the wall fan of the infected barn, and the other end was placed inside the trailer. Air from the building was exhausted into the trailer 24 hours a day for seven consecutive days and PRRSV infection was monitored in the infected pigs and the sentinel pigs. Air samples were collected from the infected barn and the trailer. PRRSV infection was detected in the infected pigs three and seven days after they were infected, but not in the sentinel pigs. All the air samples were negative for PRRSV by PCR, virus isolation and a pig bioassay.

Evaluation of the role of mallard ducks as vectors of porcine reproductive and respiratory syndrome virus.

To assess the transmission of porcine reproductive and respiratory syndrome virus (PRRSV) from pigs to mallard ducks, 10 adult (one-year-old) female mallard ducks were housed with pigs infected experimentally with PRRSV, and allowed to be in close contact with them for 21 days. To evaluate the transmission of PRRSV from mallard ducks to pigs, two adult ducks were inoculated orally with PRRSV (total dose 10(6.0) TCID50) and allowed to drink PRRsv-infected water; 24 hours later, two four-week-old PRRsv-naive sentinel pigs were housed in pens below the cages housing the ducks for 14 days. In both experiments, cloacal and faecal samples were collected three times a week from the ducks and tested by PCR, virus isolation and a pig bioassay. Blood samples from the pigs were tested by ELISA, PCR and virus isolation. Sera from the ducks were tested by serum neutralisation. The ducks were examined postmortem and selected tissues were tested by PCR, virus isolation, histopathology and pig bioassay. In both experiments all the cloacal swabs, faecal samples, tissues and sera from the ducks were negative by all the tests. The sera from the pigs in the first experiment were PCR positive at three, seven, 14 and 21 days after infection and ELISA positive at 14 and 21 days. Sera from the pigs in the second experiment were negative by all the tests. The virus was isolated from the oral inoculum and the drinking water provided for the ducks in the second experiment. Under the conditions of this study, it was not possible to demonstrate the transmission of PRRSV either from the pigs to the ducks or from the ducks to the pigs.

Studies on the carriage and transmission of porcine reproductive and respiratory syndrome virus by individual houseflies (Musca domestica).

The objectives of the study were to determine the site of porcine reproductive and respiratory syndrome virus (PRRSV) in individual houseflies, to assess whether an individual housefly could transmit PRRSV to a susceptible pig, and to compare the ability of PCR, virus isolation and a pig bioassay to detect PRRSV in houseflies. In the first experiment 26 houseflies were fed on a pig infected experimentally with PRRSV; 13 were processed as a whole fly homogenate, while an exterior surface wash and a gut homogenate were collected from the other 13. Infectious PRRSV was recovered from nine of the whole fly homogenates, 12 of the gut homogenates and one of the exterior surface washes. In the second experiment, two of 10 individual houseflies, which had fed on an infected pig, transmitted PRRSV to a susceptible pig in a controlled manual transmission protocol. In the third experiment, single flies or pools of 30 flies were immersed in different concentrations of a PRRSV inoculum, then tested by PCR, virus isolation and bioassay. The virus was detected at a concentration of 10(1) TCID50/ml by PCR, 10(2) TCID50/ml by the bioassay and 10(3) TCID50/ml by virus isolation.

Transmission of porcine reproductive and respiratory syndrome virus by houseflies (Musca domestica).

Three hundred houseflies were allowed to feed on donor pigs viraemic with porcine reproductive and respiratory syndrome virus (PRRSV) on the fifth, sixth and seventh days after the pigs had been inoculated with the virus. After 60 seconds, the flies' feeding was interrupted, and they were transferred manually to feed to repletion on a naive recipient pig housed in a separate room. To enhance the chance of the flies obtaining the pigs' blood, the back of each pig was scarified with sandpaper until a slight haemorrhage was visible. The PRRSV was transmitted from the donor to the recipient pigs, and PRRSV RNA was detected by reverse transcriptase-PCR from homogenates of the flies. In a second experiment, 210 houseflies were allowed to feed to repletion on a PRRSV-infected pig on the sixth day after it had been inoculated, and were then maintained under laboratory conditions. Groups of 30 flies were collected immediately after they had fed and six, 12, 24, 48, 72 and 96 hours later, and were tested for PRRSV. Homogenates of the flies collected up to six hours after feeding were PCR- and pig bioassay-positive, but the others were negative by both tests.

Atresia pulmonar con septum ventricular intacto: enfoque diagnóstico y terapéutico / Pulmonary atresia with intact interventricular septum

Se describe la variabilidad, evaluación prenatal, la aproximación diagnóstica y las estrategias de tratamiento en atresia pulmonar con septum ventricular intacto, en un centro cardioquirúrgico pediátrico chileno. Una enfermedad poco común, que muestra considerable heterogeneidad morfológica, y sin reportes locales sobre estos tópicos. Estudiamos una serie consecutiva de 28 casos, en un período de cinco años (1997-2002), en el centro cardiovascular del Hospital Luis Calvo Mackenna. Las características morfológicas de cada caso fueron evaludas por revisión directa de los ecocardiogramas, angiocardiogramas, y uno de los protocolos quirúrgicos. De los 28 pacientes, la atresia fue membranosa en 82 por ciento y muscular en 18 por ciento. El ventrículo derecho fue bipartito en el 30 por ciento, unipartito en el 6 por ciento and tripartito en el 64 por ciento de los casos. Se identificaron anormalidades coronarias en el 36 por ciento, y circulación de estas dependiente del ventrículo derecho en el 7,1 por ciento. La mediana para el valor del anillo valvular tricuspideo fue de -3. El diagnóstico fue hecho en etapa fetal en seis de 28 casos (21.4 por ciento). Se tomaron las medidas para que en todos estos pacientes el parto se produjera, en un hospital cercano al centro cardiovascular. La reparación quirúrgica se realizó, basándose en predictores ecocardiográficos, el grupo con solución biventricular mostró un valor Z tricuspideo promedio de -1,1 para el grupo univentricular este valor fue de -5 (p<0,001), el índice trucúspide/mitral (T/M) fue de 0,8 y 0,4 respectivamente (p<0,001). Tres pacientes dentro del grupo biventricular requirieron, posteriormente una solución de tipo ventrículo y medio con un índice T/M medio de 0,4 (p<0,001). Existió 100 por ciento de concordancia respecto a la presencia de alteraciones coronarias, entre las técnicas ecocardiográficas y angiográfica. Este estudio muestra datos acerca de la diversidad morfológica, los esfuerzos iniciales en el diagnóstic fetal, hecho en nuestro país, además de los excelentes resultados quirúrgicos obtenidos con un enfrentamiento diagnóstico y terapéutico selectivo, en esta poco común patología